Kalyanam Shivkumar - Academia.edu (original) (raw)

Papers by Kalyanam Shivkumar

Research paper thumbnail of Quantitative Analysis of Localized Sources Identified by Focal Impulse and Roter Modulation Mapping in Atrial Fibrillation

Circulation: Arrhythmia and Electrophysiology, 2015

-New approaches to ablation of atrial fibrillation (AF) include focal impulse and rotor modulatio... more -New approaches to ablation of atrial fibrillation (AF) include focal impulse and rotor modulation (FIRM) mapping, and initial results reported with this technique have been favorable. We sought to independently evaluate the approach by analyzing quantitative characteristics of atrial electrograms (AEGMs) used to identify rotors, and describe acute procedural outcomes of FIRM-guided ablation. -All FIRM-guided ablation procedures (n=24, 50% paroxysmal) at UCLA Medical Center were included for analysis. During AF, unipolar AEGMs collected from a 64-pole basket catheter were used to construct phase maps and identify putative AF sources. These sites were targeted for ablation, in conjunction with pulmonary vein isolation (PVI) in most patients (n=19, 79%). All patients had rotors identified (mean 2.3 ± 0.9 per patient, 72% in LA). Prespecified acute procedural endpoint was achieved in 12/24 (50%) patients: AF termination (n=1), organization (n=3), or >10% slowing of AF cycle length (n=8). Basket electrodes were within 1cm of 54% of LA surface area, and a mean of 31 electrodes per patient showed interpretable AEGMs. Offline analysis revealed no differences between rotor and distant sites in dominant frequency or Shannon entropy. Electroanatomic mapping showed no rotational activation at FIRM-identified rotor sites in 23/24 patients (96%). -FIRM-identified rotor sites did not exhibit quantitative AEGM characteristics expected from rotors, and did not differ quantitatively from surrounding tissue. Catheter ablation of these sites, in conjunction with PVI, resulted in AF termination or organization in a minority of patients (4/24, 17%). Further validation of this approach is necessary.

Research paper thumbnail of Transmural "Scar-to-Scar" Reentrant Ventricular Tachycardia

Indian pacing and electrophysiology journal, 2013

We describe a scar-related reentrant ventricular tachycardia circuit with a proximal segment in a... more We describe a scar-related reentrant ventricular tachycardia circuit with a proximal segment in an endocardial basal septal scar and an exit in a region of slow conduction in a non-overlapping region of epicardial basal lateral scar. The 12-lead EKG demonstrates criteria for a basal lateral epicardial VT, however the same morphology could be produced with a longer stim-latency with pace mapping or VT induction from the endocardial septal region of scar. A significant segment of myocardium demonstrated no endocardial or epicardial scar on electroanatomic mapping, suggesting the presence of a mid-myocardial isthmus. Further evidence was provided by assessment of unipolar settings. The epicardial VT that initially appeared to originate from the basal lateral epicardial region, was successfully treated with radiofrequency ablation of the lateral aspect of the endocardial septal scar.

Research paper thumbnail of Author's Reply to "More Awareness less Risk --- Interpretation of Ablation Risk Caused by Coronary Arterial Anatomy

Heart rhythm : the official journal of the Heart Rhythm Society, Jan 23, 2015

Research paper thumbnail of Neuraxial modulation for treatment of VT storm

Journal of biomedical research, 2015

In the hyperadrenergic state of VT storm where shocks are psychologically and physiologically tra... more In the hyperadrenergic state of VT storm where shocks are psychologically and physiologically traumatizing, suppression of sympathetic outflow from the organ level of the heart up to higher braincenters plays a significant role in reducing the propensity for VT recurrence. The autonomic nervous system continuously receives input from the heart (afferent signaling), integrates them, and sends efferent signals to modify or maintain cardiac function and arrhythmogenesis. Spinal anesthesia with thoracic epidural infusion of bupivicaine and surgical removal of the sympathetic chain including the stellate ganglion has been shown to decrease recurrences of VT. Excess sympathetic outflow with catecholamine release can be modified with catheter-based renal denervation. The insights provided from animal experiments and in patients that are refractory to conventional therapy have significantly improved our working understanding of the heart as an end organ in the autonomic nervous system.

Research paper thumbnail of Electrophysiological effects of right and left vagal nerve stimulation on the ventricular myocardium

American journal of physiology. Heart and circulatory physiology, 2014

Vagal nerve stimulation (VNS) has been proposed as a cardioprotective intervention. However, regi... more Vagal nerve stimulation (VNS) has been proposed as a cardioprotective intervention. However, regional ventricular electrophysiological effects of VNS are not well characterized. The purpose of this study was to evaluate effects of right and left VNS on electrophysiological properties of the ventricles and hemodynamic parameters. In Yorkshire pigs, a 56-electrode sock was used for epicardial (n = 12) activation recovery interval (ARI) recordings and a 64-electrode catheter for endocardial (n = 9) ARI recordings at baseline and during VNS. Hemodynamic recordings were obtained using a conductance catheter. Right and left VNS decreased heart rate (84 ± 5 to 71 ± 5 beats/min and 84 ± 4 to 73 ± 5 beats/min), left ventricular pressure (89 ± 9 to 77 ± 9 mmHg and 91 ± 9 to 83 ± 9 mmHg), and dP/dtmax (1,660 ± 154 to 1,490 ± 160 mmHg/s and 1,595 ± 155 to 1,416 ± 134 mmHg/s) and prolonged ARI (327 ± 18 to 350 ± 23 ms and 327 ± 16 to 347 ± 21 ms, P < 0.05 vs. baseline for all parameters and P...

Research paper thumbnail of Cardiac involvement in sarcoidosis: evolving concepts in diagnosis and treatment

Seminars in respiratory and critical care medicine, 2014

Clinically evident sarcoidosis involving the heart has been noted in at least 2 to 7% of patients... more Clinically evident sarcoidosis involving the heart has been noted in at least 2 to 7% of patients with sarcoidosis, but occult involvement is much higher (> 20%). Cardiac sarcoidosis is often not recognized antemortem, as sudden death may be the presenting feature. Cardiac involvement may occur at any point during the course of sarcoidosis and may occur in the absence of pulmonary or systemic involvement. Sarcoidosis can involve any part of the heart, with protean manifestations. Prognosis of cardiac sarcoidosis is related to extent and site(s) of involvement. Most deaths due to cardiac sarcoidosis are due to arrhythmias or conduction defects, but granulomatous infiltration of the myocardium may be lethal. The definitive diagnosis of isolated cardiac sarcoidosis is difficult. The yield of endomyocardial biopsies is low; treatment of cardiac sarcoidosis is often warranted even in the absence of histologic proof. Radionuclide scans are integral to the diagnosis. Currently, 18F-fluo...

Research paper thumbnail of Relationship Between Sinus Rhythm Late Activation Zones and Critical Sites for Scar-Related Ventricular Tachycardia: A Systematic Analysis of Isochronal Late Activation Mapping

Circulation: Arrhythmia and Electrophysiology, 2015

-It is not known if the most delayed late potentials are functionally most specific for scar-rela... more -It is not known if the most delayed late potentials are functionally most specific for scar-related ventricular tachycardia (VT) circuits. -Isochronal late activation maps (ILAM) were constructed to display ventricular activation during sinus rhythm over eight isochrones. Analysis was performed at successful VT termination sites and prospectively tested. 33 patients with 47 scar-related VTs where a critical site was demonstrated by termination of VT during ablation were retrospectively analyzed. In those that underwent mapping of multiple surfaces, 90% of critical sites were on the surface that contained the latest late potential. However, only 11% of critical sites were localized to the latest isochrone (87.5-100%) of ventricular activation. The median percentage of latest activation at critical sites was 78% at a distance from the latest isochrone of 18 mm. Sites critical to reentry were harbored in regions with slow conduction velocity, where 3 isochrones were present within a 1 cm radius. 10 consecutive patients underwent ablation prospectively guided by ILAM, targeting concentric isochrones outside of the latest isochrone. Elimination of the targeted VT was achieved in 90%. Termination of VT was achieved in 6 patients at a mean ventricular activation percentage of 78%, with only 1 requiring ablation in the latest isochrone. -Late potentials identified in the latest isochrone of activation during sinus rhythm are infrequently correlated with successful ablation sites for VT. The targeting of slow conduction regions propagating into the latest zone of activation may be a novel and promising strategy for substrate modification.

Research paper thumbnail of The molecular basis of cardiac arrhythmias in patients with cardiomyopathy

Current heart failure reports, 2004

Cardiac arrhythmias are a leading cause of mortality and morbidity in Western society. In some sp... more Cardiac arrhythmias are a leading cause of mortality and morbidity in Western society. In some specific instances, these arrhythmias are caused by abnormalities of cardiac ion channels, such as sodium, calcium, and potassium channels, which carry ionic currents and are fundamental determinants of cardiac excitability. Abnormalities of these ion channels are attributed to mutations in the genes encoding the channel protein and cause altered function of channels, which can predispose to arrhythmias. During heart failure, many channels also malfunction because of altered expression, resulting in lethal arrhythmias.

Research paper thumbnail of Detecting and monitoring arrhythmia recurrence following catheter ablation of atrial fibrillation

Frontiers in Physiology, 2015

Atrial fibrillation (AF) is the most common arrhythmia prompting clinical presentation, is associ... more Atrial fibrillation (AF) is the most common arrhythmia prompting clinical presentation, is associated with significant morbidity and mortality. The incidence and prevalence of this arrhythmia is expected to grow significantly in the coming decades. Of the available pharmacologic and non-pharmacologic treatment options, the fastest growing and most intensely studied is catheter-based ablation therapy for AF. Given the varying success rates for AF ablation, the increasingly complex factors that need to be taken into account when deciding to proceed with ablation, as well as varying definitions of procedural success, accurate detection of arrhythmia recurrence and its burden is of significance. Detecting and monitoring AF recurrence following catheter ablation is therefore an important consideration. Multiple studies have demonstrated the close relationship between the intensity of rhythm monitoring with wearable ambulatory cardiac monitors, or implantable cardiac rhythm monitors and the detection of arrhythmia recurrence. Other studies have employed algorithms dependent on intensive monitoring and arrhythmia detection in the decision tree on whether to proceed with repeat ablation or medical therapy. In this review, we discuss these considerations, types of monitoring devices, and implications for monitoring AF recurrence following catheter ablation.

Research paper thumbnail of Initial Experience with an Active-Fixation Defibrillation Electrode and the Presence of Nonphysiological Sensing

Nonphysiological sensing by a pacing and defibrillation electrode may result in inappropriate def... more Nonphysiological sensing by a pacing and defibrillation electrode may result in inappropriate defibrillator discharges and/or inhibition of pacing. Active-fixation electrodes may be more likely to sense diaphragmatic myopotentials because of the protrusion of the screw for fixation. In addition, the movement of the fixation screw in an integrated bipolar lead system could also result in inappropriate sensing. This may be increasingly important in patients who are pacemaker dependent because the dynamic range of the autogain feature of these devices is much more narrow. Five of 15 consecutive patients who received a CPI model 0154 or 0155 active-fixation defibrillation electrode with an ICD system (CPI Ventak A V3DR model 1831 or CPI Ventak VR model 1774 defibrillator) are described. In 2 of the 15 patients, nonphysiological sensing appearing to be diaphragmatic myopotentials resulted in inappropriate defibrillator discharges. Both patients were pacemaker dependent. Changes in the sensitivity from nominal to less sensitive prevented inappropriate discharges. In one patient, discreet nonphysiological sensed events with the electrogram suggestive of ventricular activation was noted at the time of implantation. This was completely eliminated by redeployment of the active-fixation lead in the interventricular septum. In two other patients, discreet nonphysiological sensed events resulted in intermittent inhibition of ventricular pacing after implantation. These were still seen in the least sensitive autogain mode for ventricular amplitude. These were not seen on subsequent interrogation 1 month after implantation. Increased awareness of nonphysiological sensing is recommended. The CPI 0154 and 0155 leads seem to be particularly prone to this abnormality. Particular attention should be made when deploying an active-fixation screw for an integrated bipolar lead. This increased awareness is more important when a given individual is pacemaker dependent, which may warrant DFT testing in a least or less sensitive mode in these patients.

Research paper thumbnail of Catheter ablation of accessory pathways near the coronary sinus: Value of defining coronary arterial anatomy

Heart rhythm : the official journal of the Heart Rhythm Society, 2015

Accessory pathways can lie near or within the coronary sinus (CS). Radiofrequency catheter ablati... more Accessory pathways can lie near or within the coronary sinus (CS). Radiofrequency catheter ablation of accessory pathways is a well-established treatment option, but this procedure can cause damage to adjacent coronary arteries. The purpose of this study was to evaluate the anatomic relationship between the coronary arteries and the CS. Retrospective data of patients who underwent catheter ablation of supraventricular tachycardia between June 2011 and August 2013 was reviewed. In addition, detailed analysis of coronary computed tomographic angiography (CTA) data from 50 patients was performed. Between June 2011 and August 2013, 427 patients underwent catheter ablation of supraventricular tachycardia, of whom 105 (age 28 ± 17 years, 60% male) had accessory pathway-mediated tachycardia. Of these, 23 patients had accessory pathways near the CS, and 60% (N = 14) underwent concurrent coronary angiography. In 4 patients, the posterolateral (inferolateral) branch (PLA) of the right coronar...

Research paper thumbnail of Device artifact reduction for magnetic resonance imaging of patients with implantable cardioverter-defibrillators and ventricular tachycardia: late gadolinium enhancement correlation with electroanatomic mapping

Heart rhythm : the official journal of the Heart Rhythm Society, 2014

Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) of ventricular scar has been s... more Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) of ventricular scar has been shown to be accurate for detection and characterization of arrhythmia substrates. However, the majority of patients referred for ventricular tachycardia (VT) ablation have an implantable cardioverter-defibrillator (ICD), which obscures image integrity and the clinical utility of MRI. The purpose of this study was to develop and validate a wideband LGE MRI technique for device artifact removal. A novel wideband LGE MRI technique was developed to allow for improved scar evaluation on patients with ICDs. The wideband technique and the standard LGE MRI were tested on 18 patients with ICDs. VT ablation was performed in 13 of 18 patients with either endocardial and/or epicardial approach and the correlation between the scar identified on MRI and electroanatomic mapping (EAM) was analyzed. Hyperintensity artifact was present in 16 of 18 of patients using standard MRI, which was eliminated using ...

Research paper thumbnail of Sympathetic Nerve Stimulation, Not Circulating Norepinephrine, Modulates T-Peak to T-End Interval by Increasing Global Dispersion of Repolarization

Circulation: Arrhythmia and Electrophysiology, 2014

T-peak to T-end interval (Tp-e) is an independent marker of sudden cardiac death. Modulation of T... more T-peak to T-end interval (Tp-e) is an independent marker of sudden cardiac death. Modulation of Tp-e by sympathetic nerve activation and circulating norepinephrine is not well understood. The purpose of this study was to characterize endocardial and epicardial dispersion of repolarization (DOR) and its effects on Tp-e with sympathetic activation. In Yorkshire pigs (n=13), a sternotomy was performed and the heart and bilateral stellate ganglia were exposed. A 56-electrode sock and 64-electrode basket catheter were placed around the epicardium and in the left ventricle (LV), respectively. Activation recovery interval, DOR, defined as variance in repolarization time, and Tp-e were assessed before and after left, right, and bilateral stellate ganglia stimulation and norepinephrine infusion. LV endocardial and epicardial activation recovery intervals significantly decreased, and LV endocardial and epicardial DOR increased during sympathetic nerve stimulation. There were no LV epicardial versus endocardial differences in activation recovery interval during sympathetic stimulation, and regional endocardial activation recovery interval patterns were similar to the epicardium. Tp-e prolonged during left (from 40.4±2.2 ms to 92.4±12.4 ms; P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.01), right (from 47.7±2.6 ms to 80.7±11.5 ms; P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.01), and bilateral (from 47.5±2.8 ms to 78.1±9.8 ms; P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.01) stellate stimulation and strongly correlated with whole heart DOR during stimulation (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001, R=0.86). Of note, norepinephrine infusion did not increase DOR or Tp-e. Regional patterns of LV endocardial sympathetic innervation are similar to that of LV epicardium. Tp-e correlated with whole heart DOR during sympathetic nerve activation. Circulating norepinephrine did not affect DOR or Tp-e.

Research paper thumbnail of Ventricular tachycardia in ischemic heart disease substrates

Indian Heart Journal, 2014

Advances in the treatment of myocardial infarction (MI) have improved survival after ischemic car... more Advances in the treatment of myocardial infarction (MI) have improved survival after ischemic cardiac injury. Post-infarct structural and functional remodeling results in electrophysiologic substrates at risk for monomorphic ventricular tachycardia (MMVT). Characterization of this substrate using a variety of clinical and investigative tools has improved our understanding of MMVT circuits, and has accelerated the development of device and catheter-based therapies aimed at identification and elimination of this arrhythmia. This review will discuss the central role of the ischemic heart disease substrate in the development MMVT. Electrophysiologic characterization of the post-infarct myocardium using bipolar electrogram amplitudes to delineate scar border zones will be reviewed. Functional electrogram determinants of reentrant circuits such as isolated late potentials will be discussed. Strategies for catheter ablation of reentrant ventricular tachycardia, including structural and functional targets will also be examined, as will the role of the epicardial mapping and ablation in the management of recurrent MMVT.

Research paper thumbnail of Catheter ablation of scar-based ventricular tachycardia: Relationship of procedure duration to outcomes and hospital mortality

Heart Rhythm, 2015

Ablation has become an important option for treatment of ventricular tachycardia (VT). The influe... more Ablation has become an important option for treatment of ventricular tachycardia (VT). The influence of procedure duration on outcomes remains unexamined. The purpose of this study was to determine the influence of procedure duration on outcomes and complications over an 8-year period Patients referred for scar-mediated VT ablation from 2004 to 2011 were retrospectively analyzed. Procedure duration was defined as the time from the insertion of catheters through the femoral vein to the time of their withdrawal. Procedure duration was analyzed in relationship with baseline and intraoperative covariates, acute procedural outcomes, complications, and 6-month clinical outcomes. One hundred forty-eight patients underwent VT ablation with mean procedure duration of 5.7 ± 1.8 hours. VT recurrence and survival at 6 months were 46% and 82%, respectively, and were not associated with procedure duration. Hospital mortality increased with intraoperative intraaortic balloon pump insertion (adjusted odds ratio [OR] 13.7, 95% confidence interval [CI] 2.35-79.94, P = .004) and was improved with successful ablation of the clinical VT as a procedural end-point (adjusted OR 0.13, 95% Cl 0.03-0.54, P = .005). The association between procedure duration and hospital mortality remained after adjusting for significant baseline variables (adjusted OR 1.75, 95% CI 1.14-2.68, P = .0098) and intraoperative variables (adjusted OR 1.6, 95% CI 1.12-2.29, P = .0104). Hospital mortality was significantly increased by unsuccessful clinical VT ablation as a procedural end-point and intraoperative intraaortic balloon pump insertion. However, after adjusting for significant baseline and intraoperative covariates, procedure duration still was associated with increased hospital mortality. Procedure duration had no impact on VT recurrence and survival at 6 months.

Research paper thumbnail of Repolarization parameters are associated with mortality in chagas disease patients in the United States

Indian pacing and electrophysiology journal, 2014

The goal of this study was to examine the association between ECG repolarization parameters and m... more The goal of this study was to examine the association between ECG repolarization parameters and mortality in Chagas disease (CD) patients living in the United States. CD patients with cardiomyopathy (CM) and bundle branch block (BBB) or BBB alone were compared to age- and sex-matched controls. QT interval, QT dispersion (QTd), T wave peak to T wave end duration (Tp-Te) and T wave peak to T wave end dispersion ((Tp-Te)d) were measured. Presence of fractionated QRS (fQRS) was also assessed. The main outcome measure was the association between ECG parameters and mortality or need for cardiac transplant. A total of 18 CM and 13 BBB CD patients were studied with 97% originating from Mexico or Central America. QTd (60.0±15.0 ms vs 43.5±9.8 ms, P=0.0002), Tp-Te (102.6±29.3 ms vs 77.1±11.0 ms, P=0.0002) and (Tp-Te)d (39.5±9.4 ms vs 22.7±7.6 ms, P<0.0001) were prolonged in CD CM patients compared to CM controls. Chagas CM patients had more fQRS then controls (84.2±0.10% vs 33.3±0.11%, p=0...

Research paper thumbnail of Beyond Coronary Sinus Angiography: The Value of Coronary Arteriography and Identification of the Pericardiophrenic Vein During Left Ventricular Lead Placement

Pacing and Clinical Electrophysiology, 2005

The purpose of this study was to define the role coronary arteriography (venous phase) for improv... more The purpose of this study was to define the role coronary arteriography (venous phase) for improving the success of left ventricular (LV) lead implantation and to define the value of identifying the pericardiophrenic vein for optimal LV lead placement in biventricular (bi-v) device implantation. Seventy-seven patients underwent bi-v device implantation between July 2002 and October 2003. If the coronary sinus (CS) could not be accessed, then left coronary arteriography was performed during the same procedure. CS access was guided by venous phase images of the coronary arteriogram. The pericardiophrenic vein was identified by selective cannulation or direct visualization. Patients with Cr &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 1.5 had gadolinium used as the contrast agent. Seventy-five successful implants were performed (97%). In seven patients (9%) repeated attempts at retrograde cannulation of the CS failed (attempt time 130 +/- 20 minute, mean +/- SD). In these patients, coronary arteriography helped define the location of the CS, which was subsequently successfully cannulated. In six patients the pericardiophrenic vein was identified either during occlusion venography of the CS (postthoracotomy, veno-venous collaterals, n = 2) or during selective cannulation of the pericardiophrenic vein (using a DAIG Csl catheter, n = 4). The vein was directly visualized in three patients who underwent surgical LV lead implantation. LV leads in all these cases were implanted in areas not overlying the preidentified pericardiophrenic vein. During follow-up, none of these patients had evidence of phrenic nerve stimulation. Intraoperative left coronary arteriography increases the success of CS cannulation. Identification of the pericardiophrenic vein is a useful method to avoid phrenic nerve stimulation.

Research paper thumbnail of Characterization of the Arrhythmogenic Substrate in Ischemic and Nonischemic Cardiomyopathy

Journal of the American College of Cardiology, 2010

Objective-The purpose of this study was to compare the characteristics and prevalence of late pot... more Objective-The purpose of this study was to compare the characteristics and prevalence of late potentials (LP) in patients with cardiomyopathy of nonischemic (NICM) and ischemic (ICM) etiologies and evaluate their value as targets for catheter ablation.

Research paper thumbnail of Coupling Interval Variability Differentiates Ventricular Ectopic Complexes Arising in the Aortic Sinus of Valsalva and Great Cardiac Vein From Other Sources: Mechanistic and Arrhythmic Risk Implications

Journal of the American College of Cardiology, 2014

The objective of this study was to determine whether premature ventricular contractions (PVCs) ar... more The objective of this study was to determine whether premature ventricular contractions (PVCs) arising from the aortic sinuses of Valsalva (SOV) and great cardiac vein (GCV) have coupling interval (CI) characteristics that differentiate them from other ectopic foci. PVCs occur at relatively fixed CI from the preceding normal QRS complex in most patients. However, we observed patients with PVCs originating in unusual areas (SOV and GCV) in whom the PVC CI was highly variable. We hypothesized that PVCs from these areas occur seemingly randomly because of the lack of electrotonic effects of the surrounding myocardium. Seventy-three consecutive patients referred for PVC ablation were assessed. Twelve consecutive PVC CIs were recorded. The ΔCI (maximum - minimum CI) was measured. We studied 73 patients (age 50 ± 16 years, 47% male). The PVC origin was right ventricular (RV) in 29 (40%), left ventricular (LV) in 17 (23%), SOV in 21 (29%), and GCV in 6 (8%). There was a significant difference between the mean ΔCI of RV/LV PVCs compared with SOV/GCV PVCs (33 ± 15 ms vs. 116 ± 52 ms, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001). A ΔCI of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;60 ms demonstrated a sensitivity of 89%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 94%. Cardiac events were more common in the SOV/GCV group versus the RV/LV group (7 of 27 [26%] vs. 2 of 46 [4%], p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.02). ΔCI is more pronounced in PVCs originating from the SOV or GCV. A ΔCI of 60 ms helps discriminate the origin of PVCs before diagnostic electrophysiological study and may be associated with increased frequency of cardiac events.

Research paper thumbnail of Bilateral Cardiac Sympathetic Denervation for the Management of Electrical Storm

Journal of the American College of Cardiology, 2012

Research paper thumbnail of Quantitative Analysis of Localized Sources Identified by Focal Impulse and Roter Modulation Mapping in Atrial Fibrillation

Circulation: Arrhythmia and Electrophysiology, 2015

-New approaches to ablation of atrial fibrillation (AF) include focal impulse and rotor modulatio... more -New approaches to ablation of atrial fibrillation (AF) include focal impulse and rotor modulation (FIRM) mapping, and initial results reported with this technique have been favorable. We sought to independently evaluate the approach by analyzing quantitative characteristics of atrial electrograms (AEGMs) used to identify rotors, and describe acute procedural outcomes of FIRM-guided ablation. -All FIRM-guided ablation procedures (n=24, 50% paroxysmal) at UCLA Medical Center were included for analysis. During AF, unipolar AEGMs collected from a 64-pole basket catheter were used to construct phase maps and identify putative AF sources. These sites were targeted for ablation, in conjunction with pulmonary vein isolation (PVI) in most patients (n=19, 79%). All patients had rotors identified (mean 2.3 ± 0.9 per patient, 72% in LA). Prespecified acute procedural endpoint was achieved in 12/24 (50%) patients: AF termination (n=1), organization (n=3), or &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;10% slowing of AF cycle length (n=8). Basket electrodes were within 1cm of 54% of LA surface area, and a mean of 31 electrodes per patient showed interpretable AEGMs. Offline analysis revealed no differences between rotor and distant sites in dominant frequency or Shannon entropy. Electroanatomic mapping showed no rotational activation at FIRM-identified rotor sites in 23/24 patients (96%). -FIRM-identified rotor sites did not exhibit quantitative AEGM characteristics expected from rotors, and did not differ quantitatively from surrounding tissue. Catheter ablation of these sites, in conjunction with PVI, resulted in AF termination or organization in a minority of patients (4/24, 17%). Further validation of this approach is necessary.

Research paper thumbnail of Transmural "Scar-to-Scar" Reentrant Ventricular Tachycardia

Indian pacing and electrophysiology journal, 2013

We describe a scar-related reentrant ventricular tachycardia circuit with a proximal segment in a... more We describe a scar-related reentrant ventricular tachycardia circuit with a proximal segment in an endocardial basal septal scar and an exit in a region of slow conduction in a non-overlapping region of epicardial basal lateral scar. The 12-lead EKG demonstrates criteria for a basal lateral epicardial VT, however the same morphology could be produced with a longer stim-latency with pace mapping or VT induction from the endocardial septal region of scar. A significant segment of myocardium demonstrated no endocardial or epicardial scar on electroanatomic mapping, suggesting the presence of a mid-myocardial isthmus. Further evidence was provided by assessment of unipolar settings. The epicardial VT that initially appeared to originate from the basal lateral epicardial region, was successfully treated with radiofrequency ablation of the lateral aspect of the endocardial septal scar.

Research paper thumbnail of Author's Reply to "More Awareness less Risk --- Interpretation of Ablation Risk Caused by Coronary Arterial Anatomy

Heart rhythm : the official journal of the Heart Rhythm Society, Jan 23, 2015

Research paper thumbnail of Neuraxial modulation for treatment of VT storm

Journal of biomedical research, 2015

In the hyperadrenergic state of VT storm where shocks are psychologically and physiologically tra... more In the hyperadrenergic state of VT storm where shocks are psychologically and physiologically traumatizing, suppression of sympathetic outflow from the organ level of the heart up to higher braincenters plays a significant role in reducing the propensity for VT recurrence. The autonomic nervous system continuously receives input from the heart (afferent signaling), integrates them, and sends efferent signals to modify or maintain cardiac function and arrhythmogenesis. Spinal anesthesia with thoracic epidural infusion of bupivicaine and surgical removal of the sympathetic chain including the stellate ganglion has been shown to decrease recurrences of VT. Excess sympathetic outflow with catecholamine release can be modified with catheter-based renal denervation. The insights provided from animal experiments and in patients that are refractory to conventional therapy have significantly improved our working understanding of the heart as an end organ in the autonomic nervous system.

Research paper thumbnail of Electrophysiological effects of right and left vagal nerve stimulation on the ventricular myocardium

American journal of physiology. Heart and circulatory physiology, 2014

Vagal nerve stimulation (VNS) has been proposed as a cardioprotective intervention. However, regi... more Vagal nerve stimulation (VNS) has been proposed as a cardioprotective intervention. However, regional ventricular electrophysiological effects of VNS are not well characterized. The purpose of this study was to evaluate effects of right and left VNS on electrophysiological properties of the ventricles and hemodynamic parameters. In Yorkshire pigs, a 56-electrode sock was used for epicardial (n = 12) activation recovery interval (ARI) recordings and a 64-electrode catheter for endocardial (n = 9) ARI recordings at baseline and during VNS. Hemodynamic recordings were obtained using a conductance catheter. Right and left VNS decreased heart rate (84 ± 5 to 71 ± 5 beats/min and 84 ± 4 to 73 ± 5 beats/min), left ventricular pressure (89 ± 9 to 77 ± 9 mmHg and 91 ± 9 to 83 ± 9 mmHg), and dP/dtmax (1,660 ± 154 to 1,490 ± 160 mmHg/s and 1,595 ± 155 to 1,416 ± 134 mmHg/s) and prolonged ARI (327 ± 18 to 350 ± 23 ms and 327 ± 16 to 347 ± 21 ms, P < 0.05 vs. baseline for all parameters and P...

Research paper thumbnail of Cardiac involvement in sarcoidosis: evolving concepts in diagnosis and treatment

Seminars in respiratory and critical care medicine, 2014

Clinically evident sarcoidosis involving the heart has been noted in at least 2 to 7% of patients... more Clinically evident sarcoidosis involving the heart has been noted in at least 2 to 7% of patients with sarcoidosis, but occult involvement is much higher (> 20%). Cardiac sarcoidosis is often not recognized antemortem, as sudden death may be the presenting feature. Cardiac involvement may occur at any point during the course of sarcoidosis and may occur in the absence of pulmonary or systemic involvement. Sarcoidosis can involve any part of the heart, with protean manifestations. Prognosis of cardiac sarcoidosis is related to extent and site(s) of involvement. Most deaths due to cardiac sarcoidosis are due to arrhythmias or conduction defects, but granulomatous infiltration of the myocardium may be lethal. The definitive diagnosis of isolated cardiac sarcoidosis is difficult. The yield of endomyocardial biopsies is low; treatment of cardiac sarcoidosis is often warranted even in the absence of histologic proof. Radionuclide scans are integral to the diagnosis. Currently, 18F-fluo...

Research paper thumbnail of Relationship Between Sinus Rhythm Late Activation Zones and Critical Sites for Scar-Related Ventricular Tachycardia: A Systematic Analysis of Isochronal Late Activation Mapping

Circulation: Arrhythmia and Electrophysiology, 2015

-It is not known if the most delayed late potentials are functionally most specific for scar-rela... more -It is not known if the most delayed late potentials are functionally most specific for scar-related ventricular tachycardia (VT) circuits. -Isochronal late activation maps (ILAM) were constructed to display ventricular activation during sinus rhythm over eight isochrones. Analysis was performed at successful VT termination sites and prospectively tested. 33 patients with 47 scar-related VTs where a critical site was demonstrated by termination of VT during ablation were retrospectively analyzed. In those that underwent mapping of multiple surfaces, 90% of critical sites were on the surface that contained the latest late potential. However, only 11% of critical sites were localized to the latest isochrone (87.5-100%) of ventricular activation. The median percentage of latest activation at critical sites was 78% at a distance from the latest isochrone of 18 mm. Sites critical to reentry were harbored in regions with slow conduction velocity, where 3 isochrones were present within a 1 cm radius. 10 consecutive patients underwent ablation prospectively guided by ILAM, targeting concentric isochrones outside of the latest isochrone. Elimination of the targeted VT was achieved in 90%. Termination of VT was achieved in 6 patients at a mean ventricular activation percentage of 78%, with only 1 requiring ablation in the latest isochrone. -Late potentials identified in the latest isochrone of activation during sinus rhythm are infrequently correlated with successful ablation sites for VT. The targeting of slow conduction regions propagating into the latest zone of activation may be a novel and promising strategy for substrate modification.

Research paper thumbnail of The molecular basis of cardiac arrhythmias in patients with cardiomyopathy

Current heart failure reports, 2004

Cardiac arrhythmias are a leading cause of mortality and morbidity in Western society. In some sp... more Cardiac arrhythmias are a leading cause of mortality and morbidity in Western society. In some specific instances, these arrhythmias are caused by abnormalities of cardiac ion channels, such as sodium, calcium, and potassium channels, which carry ionic currents and are fundamental determinants of cardiac excitability. Abnormalities of these ion channels are attributed to mutations in the genes encoding the channel protein and cause altered function of channels, which can predispose to arrhythmias. During heart failure, many channels also malfunction because of altered expression, resulting in lethal arrhythmias.

Research paper thumbnail of Detecting and monitoring arrhythmia recurrence following catheter ablation of atrial fibrillation

Frontiers in Physiology, 2015

Atrial fibrillation (AF) is the most common arrhythmia prompting clinical presentation, is associ... more Atrial fibrillation (AF) is the most common arrhythmia prompting clinical presentation, is associated with significant morbidity and mortality. The incidence and prevalence of this arrhythmia is expected to grow significantly in the coming decades. Of the available pharmacologic and non-pharmacologic treatment options, the fastest growing and most intensely studied is catheter-based ablation therapy for AF. Given the varying success rates for AF ablation, the increasingly complex factors that need to be taken into account when deciding to proceed with ablation, as well as varying definitions of procedural success, accurate detection of arrhythmia recurrence and its burden is of significance. Detecting and monitoring AF recurrence following catheter ablation is therefore an important consideration. Multiple studies have demonstrated the close relationship between the intensity of rhythm monitoring with wearable ambulatory cardiac monitors, or implantable cardiac rhythm monitors and the detection of arrhythmia recurrence. Other studies have employed algorithms dependent on intensive monitoring and arrhythmia detection in the decision tree on whether to proceed with repeat ablation or medical therapy. In this review, we discuss these considerations, types of monitoring devices, and implications for monitoring AF recurrence following catheter ablation.

Research paper thumbnail of Initial Experience with an Active-Fixation Defibrillation Electrode and the Presence of Nonphysiological Sensing

Nonphysiological sensing by a pacing and defibrillation electrode may result in inappropriate def... more Nonphysiological sensing by a pacing and defibrillation electrode may result in inappropriate defibrillator discharges and/or inhibition of pacing. Active-fixation electrodes may be more likely to sense diaphragmatic myopotentials because of the protrusion of the screw for fixation. In addition, the movement of the fixation screw in an integrated bipolar lead system could also result in inappropriate sensing. This may be increasingly important in patients who are pacemaker dependent because the dynamic range of the autogain feature of these devices is much more narrow. Five of 15 consecutive patients who received a CPI model 0154 or 0155 active-fixation defibrillation electrode with an ICD system (CPI Ventak A V3DR model 1831 or CPI Ventak VR model 1774 defibrillator) are described. In 2 of the 15 patients, nonphysiological sensing appearing to be diaphragmatic myopotentials resulted in inappropriate defibrillator discharges. Both patients were pacemaker dependent. Changes in the sensitivity from nominal to less sensitive prevented inappropriate discharges. In one patient, discreet nonphysiological sensed events with the electrogram suggestive of ventricular activation was noted at the time of implantation. This was completely eliminated by redeployment of the active-fixation lead in the interventricular septum. In two other patients, discreet nonphysiological sensed events resulted in intermittent inhibition of ventricular pacing after implantation. These were still seen in the least sensitive autogain mode for ventricular amplitude. These were not seen on subsequent interrogation 1 month after implantation. Increased awareness of nonphysiological sensing is recommended. The CPI 0154 and 0155 leads seem to be particularly prone to this abnormality. Particular attention should be made when deploying an active-fixation screw for an integrated bipolar lead. This increased awareness is more important when a given individual is pacemaker dependent, which may warrant DFT testing in a least or less sensitive mode in these patients.

Research paper thumbnail of Catheter ablation of accessory pathways near the coronary sinus: Value of defining coronary arterial anatomy

Heart rhythm : the official journal of the Heart Rhythm Society, 2015

Accessory pathways can lie near or within the coronary sinus (CS). Radiofrequency catheter ablati... more Accessory pathways can lie near or within the coronary sinus (CS). Radiofrequency catheter ablation of accessory pathways is a well-established treatment option, but this procedure can cause damage to adjacent coronary arteries. The purpose of this study was to evaluate the anatomic relationship between the coronary arteries and the CS. Retrospective data of patients who underwent catheter ablation of supraventricular tachycardia between June 2011 and August 2013 was reviewed. In addition, detailed analysis of coronary computed tomographic angiography (CTA) data from 50 patients was performed. Between June 2011 and August 2013, 427 patients underwent catheter ablation of supraventricular tachycardia, of whom 105 (age 28 ± 17 years, 60% male) had accessory pathway-mediated tachycardia. Of these, 23 patients had accessory pathways near the CS, and 60% (N = 14) underwent concurrent coronary angiography. In 4 patients, the posterolateral (inferolateral) branch (PLA) of the right coronar...

Research paper thumbnail of Device artifact reduction for magnetic resonance imaging of patients with implantable cardioverter-defibrillators and ventricular tachycardia: late gadolinium enhancement correlation with electroanatomic mapping

Heart rhythm : the official journal of the Heart Rhythm Society, 2014

Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) of ventricular scar has been s... more Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) of ventricular scar has been shown to be accurate for detection and characterization of arrhythmia substrates. However, the majority of patients referred for ventricular tachycardia (VT) ablation have an implantable cardioverter-defibrillator (ICD), which obscures image integrity and the clinical utility of MRI. The purpose of this study was to develop and validate a wideband LGE MRI technique for device artifact removal. A novel wideband LGE MRI technique was developed to allow for improved scar evaluation on patients with ICDs. The wideband technique and the standard LGE MRI were tested on 18 patients with ICDs. VT ablation was performed in 13 of 18 patients with either endocardial and/or epicardial approach and the correlation between the scar identified on MRI and electroanatomic mapping (EAM) was analyzed. Hyperintensity artifact was present in 16 of 18 of patients using standard MRI, which was eliminated using ...

Research paper thumbnail of Sympathetic Nerve Stimulation, Not Circulating Norepinephrine, Modulates T-Peak to T-End Interval by Increasing Global Dispersion of Repolarization

Circulation: Arrhythmia and Electrophysiology, 2014

T-peak to T-end interval (Tp-e) is an independent marker of sudden cardiac death. Modulation of T... more T-peak to T-end interval (Tp-e) is an independent marker of sudden cardiac death. Modulation of Tp-e by sympathetic nerve activation and circulating norepinephrine is not well understood. The purpose of this study was to characterize endocardial and epicardial dispersion of repolarization (DOR) and its effects on Tp-e with sympathetic activation. In Yorkshire pigs (n=13), a sternotomy was performed and the heart and bilateral stellate ganglia were exposed. A 56-electrode sock and 64-electrode basket catheter were placed around the epicardium and in the left ventricle (LV), respectively. Activation recovery interval, DOR, defined as variance in repolarization time, and Tp-e were assessed before and after left, right, and bilateral stellate ganglia stimulation and norepinephrine infusion. LV endocardial and epicardial activation recovery intervals significantly decreased, and LV endocardial and epicardial DOR increased during sympathetic nerve stimulation. There were no LV epicardial versus endocardial differences in activation recovery interval during sympathetic stimulation, and regional endocardial activation recovery interval patterns were similar to the epicardium. Tp-e prolonged during left (from 40.4±2.2 ms to 92.4±12.4 ms; P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.01), right (from 47.7±2.6 ms to 80.7±11.5 ms; P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.01), and bilateral (from 47.5±2.8 ms to 78.1±9.8 ms; P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.01) stellate stimulation and strongly correlated with whole heart DOR during stimulation (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001, R=0.86). Of note, norepinephrine infusion did not increase DOR or Tp-e. Regional patterns of LV endocardial sympathetic innervation are similar to that of LV epicardium. Tp-e correlated with whole heart DOR during sympathetic nerve activation. Circulating norepinephrine did not affect DOR or Tp-e.

Research paper thumbnail of Ventricular tachycardia in ischemic heart disease substrates

Indian Heart Journal, 2014

Advances in the treatment of myocardial infarction (MI) have improved survival after ischemic car... more Advances in the treatment of myocardial infarction (MI) have improved survival after ischemic cardiac injury. Post-infarct structural and functional remodeling results in electrophysiologic substrates at risk for monomorphic ventricular tachycardia (MMVT). Characterization of this substrate using a variety of clinical and investigative tools has improved our understanding of MMVT circuits, and has accelerated the development of device and catheter-based therapies aimed at identification and elimination of this arrhythmia. This review will discuss the central role of the ischemic heart disease substrate in the development MMVT. Electrophysiologic characterization of the post-infarct myocardium using bipolar electrogram amplitudes to delineate scar border zones will be reviewed. Functional electrogram determinants of reentrant circuits such as isolated late potentials will be discussed. Strategies for catheter ablation of reentrant ventricular tachycardia, including structural and functional targets will also be examined, as will the role of the epicardial mapping and ablation in the management of recurrent MMVT.

Research paper thumbnail of Catheter ablation of scar-based ventricular tachycardia: Relationship of procedure duration to outcomes and hospital mortality

Heart Rhythm, 2015

Ablation has become an important option for treatment of ventricular tachycardia (VT). The influe... more Ablation has become an important option for treatment of ventricular tachycardia (VT). The influence of procedure duration on outcomes remains unexamined. The purpose of this study was to determine the influence of procedure duration on outcomes and complications over an 8-year period Patients referred for scar-mediated VT ablation from 2004 to 2011 were retrospectively analyzed. Procedure duration was defined as the time from the insertion of catheters through the femoral vein to the time of their withdrawal. Procedure duration was analyzed in relationship with baseline and intraoperative covariates, acute procedural outcomes, complications, and 6-month clinical outcomes. One hundred forty-eight patients underwent VT ablation with mean procedure duration of 5.7 ± 1.8 hours. VT recurrence and survival at 6 months were 46% and 82%, respectively, and were not associated with procedure duration. Hospital mortality increased with intraoperative intraaortic balloon pump insertion (adjusted odds ratio [OR] 13.7, 95% confidence interval [CI] 2.35-79.94, P = .004) and was improved with successful ablation of the clinical VT as a procedural end-point (adjusted OR 0.13, 95% Cl 0.03-0.54, P = .005). The association between procedure duration and hospital mortality remained after adjusting for significant baseline variables (adjusted OR 1.75, 95% CI 1.14-2.68, P = .0098) and intraoperative variables (adjusted OR 1.6, 95% CI 1.12-2.29, P = .0104). Hospital mortality was significantly increased by unsuccessful clinical VT ablation as a procedural end-point and intraoperative intraaortic balloon pump insertion. However, after adjusting for significant baseline and intraoperative covariates, procedure duration still was associated with increased hospital mortality. Procedure duration had no impact on VT recurrence and survival at 6 months.

Research paper thumbnail of Repolarization parameters are associated with mortality in chagas disease patients in the United States

Indian pacing and electrophysiology journal, 2014

The goal of this study was to examine the association between ECG repolarization parameters and m... more The goal of this study was to examine the association between ECG repolarization parameters and mortality in Chagas disease (CD) patients living in the United States. CD patients with cardiomyopathy (CM) and bundle branch block (BBB) or BBB alone were compared to age- and sex-matched controls. QT interval, QT dispersion (QTd), T wave peak to T wave end duration (Tp-Te) and T wave peak to T wave end dispersion ((Tp-Te)d) were measured. Presence of fractionated QRS (fQRS) was also assessed. The main outcome measure was the association between ECG parameters and mortality or need for cardiac transplant. A total of 18 CM and 13 BBB CD patients were studied with 97% originating from Mexico or Central America. QTd (60.0±15.0 ms vs 43.5±9.8 ms, P=0.0002), Tp-Te (102.6±29.3 ms vs 77.1±11.0 ms, P=0.0002) and (Tp-Te)d (39.5±9.4 ms vs 22.7±7.6 ms, P<0.0001) were prolonged in CD CM patients compared to CM controls. Chagas CM patients had more fQRS then controls (84.2±0.10% vs 33.3±0.11%, p=0...

Research paper thumbnail of Beyond Coronary Sinus Angiography: The Value of Coronary Arteriography and Identification of the Pericardiophrenic Vein During Left Ventricular Lead Placement

Pacing and Clinical Electrophysiology, 2005

The purpose of this study was to define the role coronary arteriography (venous phase) for improv... more The purpose of this study was to define the role coronary arteriography (venous phase) for improving the success of left ventricular (LV) lead implantation and to define the value of identifying the pericardiophrenic vein for optimal LV lead placement in biventricular (bi-v) device implantation. Seventy-seven patients underwent bi-v device implantation between July 2002 and October 2003. If the coronary sinus (CS) could not be accessed, then left coronary arteriography was performed during the same procedure. CS access was guided by venous phase images of the coronary arteriogram. The pericardiophrenic vein was identified by selective cannulation or direct visualization. Patients with Cr &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 1.5 had gadolinium used as the contrast agent. Seventy-five successful implants were performed (97%). In seven patients (9%) repeated attempts at retrograde cannulation of the CS failed (attempt time 130 +/- 20 minute, mean +/- SD). In these patients, coronary arteriography helped define the location of the CS, which was subsequently successfully cannulated. In six patients the pericardiophrenic vein was identified either during occlusion venography of the CS (postthoracotomy, veno-venous collaterals, n = 2) or during selective cannulation of the pericardiophrenic vein (using a DAIG Csl catheter, n = 4). The vein was directly visualized in three patients who underwent surgical LV lead implantation. LV leads in all these cases were implanted in areas not overlying the preidentified pericardiophrenic vein. During follow-up, none of these patients had evidence of phrenic nerve stimulation. Intraoperative left coronary arteriography increases the success of CS cannulation. Identification of the pericardiophrenic vein is a useful method to avoid phrenic nerve stimulation.

Research paper thumbnail of Characterization of the Arrhythmogenic Substrate in Ischemic and Nonischemic Cardiomyopathy

Journal of the American College of Cardiology, 2010

Objective-The purpose of this study was to compare the characteristics and prevalence of late pot... more Objective-The purpose of this study was to compare the characteristics and prevalence of late potentials (LP) in patients with cardiomyopathy of nonischemic (NICM) and ischemic (ICM) etiologies and evaluate their value as targets for catheter ablation.

Research paper thumbnail of Coupling Interval Variability Differentiates Ventricular Ectopic Complexes Arising in the Aortic Sinus of Valsalva and Great Cardiac Vein From Other Sources: Mechanistic and Arrhythmic Risk Implications

Journal of the American College of Cardiology, 2014

The objective of this study was to determine whether premature ventricular contractions (PVCs) ar... more The objective of this study was to determine whether premature ventricular contractions (PVCs) arising from the aortic sinuses of Valsalva (SOV) and great cardiac vein (GCV) have coupling interval (CI) characteristics that differentiate them from other ectopic foci. PVCs occur at relatively fixed CI from the preceding normal QRS complex in most patients. However, we observed patients with PVCs originating in unusual areas (SOV and GCV) in whom the PVC CI was highly variable. We hypothesized that PVCs from these areas occur seemingly randomly because of the lack of electrotonic effects of the surrounding myocardium. Seventy-three consecutive patients referred for PVC ablation were assessed. Twelve consecutive PVC CIs were recorded. The ΔCI (maximum - minimum CI) was measured. We studied 73 patients (age 50 ± 16 years, 47% male). The PVC origin was right ventricular (RV) in 29 (40%), left ventricular (LV) in 17 (23%), SOV in 21 (29%), and GCV in 6 (8%). There was a significant difference between the mean ΔCI of RV/LV PVCs compared with SOV/GCV PVCs (33 ± 15 ms vs. 116 ± 52 ms, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001). A ΔCI of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;60 ms demonstrated a sensitivity of 89%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 94%. Cardiac events were more common in the SOV/GCV group versus the RV/LV group (7 of 27 [26%] vs. 2 of 46 [4%], p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.02). ΔCI is more pronounced in PVCs originating from the SOV or GCV. A ΔCI of 60 ms helps discriminate the origin of PVCs before diagnostic electrophysiological study and may be associated with increased frequency of cardiac events.

Research paper thumbnail of Bilateral Cardiac Sympathetic Denervation for the Management of Electrical Storm

Journal of the American College of Cardiology, 2012