Lorne Gula - Academia.edu (original) (raw)

Papers by Lorne Gula

Research paper thumbnail of Evaluation of the Young Patient Resuscitated from Ventricular Fibrillation

Cardiac Electrophysiology Clinics, 2011

Cardiac Electrophysiology Clinics, Volume 3, Issue 4, Pages 593-608, December 2011, Authors:Rajes... more Cardiac Electrophysiology Clinics, Volume 3, Issue 4, Pages 593-608, December 2011, Authors:Rajesh N. Subbiah, MBBS, PhD; Peter Leong-Sit, MD; Lorne J. Gula, MD; Allan C. Skanes, MD; James A. White, MD; Raymond Yee, MD; George J. Klein, MD; Andrew D. Krahn, MD.

Research paper thumbnail of Fused 3-dimensional whole-heart coronary artery, coronary vein and myocardial scar imaging at 3 T: Feasibility in patients with ischemic and non-ischemic cardiomyopathy

Journal of Cardiovascular Magnetic Resonance, 2010

Research paper thumbnail of Reduced Intrathoracic Impedance Correlates with Poor Renal Function in Heart Failure Patients

Journal of Cardiac Failure, 2014

Research paper thumbnail of Investigating syncope: a review

Current opinion in cardiology, 2006

This review focuses on recent literature on the cardiovascular investigation of syncope. Syncope ... more This review focuses on recent literature on the cardiovascular investigation of syncope. Syncope is a common and complex clinical entity with many varied etiologies, the diagnosis of which can often be elusive. Recent advances in the area of investigation in syncope include improvements in technologies for arrhythmia event monitoring and an increase in applicability and efficacy of traditional investigations. These advances have increased our ability to manage syncope. A better understanding of the etiology of syncope in certain cohorts has allowed tailoring of investigations and management of syncope. This is evident when syncope occurs in the presence of structural heart disease, which is associated with a higher incidence of arrhythmias and an increased 1-year mortality. Patients with left-ventricular dysfunction should be considered candidates for an implantable cardioverter defibrillator based on heart function and syncopal presentation. In the absence of significant heart dise...

Research paper thumbnail of Effect of beta-blockers on QT dynamics in the long QT syndrome: measuring the benefit

Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology, 2014

Beta-blockers are the standard of care for the treatment of long QT syndrome (LQTS), and have bee... more Beta-blockers are the standard of care for the treatment of long QT syndrome (LQTS), and have been shown to reduce recurrent syncope and mortality in patients with type 1 LQTS (LQT1). Although beta-blockers have minimal effect on the resting corrected QT interval, their effect on the dynamics of the non-corrected QT interval is unknown, and may provide insight into their protective effects. Twenty-three patients from eight families with genetically distinct mutations for LQT1 performed exercise stress testing before and after beta-blockade. One hundred and fifty-two QT, QTc, and Tpeak-Tend intervals were measured before starting beta-blockers and compared with those at matched identical cycle lengths following beta-blockade. Beta-blockers demonstrated heart-rate-dependent effects on the QT and QTc intervals. In the slowest heart rate tertile (<90 b.p.m.), beta-blockade increased the QT and QTc intervals (QT: 405 vs. 409 ms; P = 0.06; QTc: 459 vs. 464 ms; P = 0.06). In the fastest...

Research paper thumbnail of A Randomized Controlled Trial of the Efficacy and Safety of Electroanatomic Circumferential Pulmonary Vein Ablation Supplemented by Ablation of Complex Fractionated Atrial Electrograms Versus Potential-Guided Pulmonary Vein Antrum Isolation Guided by Intracardiac Ultrasound

Circulation-arrhythmia and Electrophysiology, 2009

The study was conducted to compare relative safety and efficacy of pulmonary vein antrum isolatio... more The study was conducted to compare relative safety and efficacy of pulmonary vein antrum isolation (PVAI) using intracardiac echocardiographic guidance and circumferential pulmonary vein ablation (CPVA) for atrial fibrillation (AF) using radiofrequency energy. Sixty patients (81% men; 81% paroxysmal; age, 56+/-8 years) failing 2+/-1 antiarrhythmic drugs were randomly assigned to undergo CPVA (n=30) or PVAI (n=30) at 5 centers between December 2004 and October 2007. CPVA patients had circular lesions placed at least 1 cm outside of the veins. Ipsilateral veins were ablated en block with the end point of disappearance of potentials within the circular lesion. Left atrial roof line and mitral isthmus line were ablated without verification of block. For patients in AF postablation or with AF induced with programmed stimulation, complex fractionated electrograms were mapped and ablated to the end point of AF termination or disappearance of complex fractionated electrograms. PVAI did not include complex fractionated electrogram ablation. Esophageal temperature was monitored and kept within 2 degrees C of baseline or under 39 degrees C. Success was defined as absence of atrial tachyarrhythmias (AF/AT) off antiarrhythmic drugs. There was no difference between CPVA and PVAI regarding to baseline variables, catheter used, duration of the procedure, or RF delivery. Fluoroscopy time was longer with PVAI (54+/-17 minutes versus 77+/-18 minutes, P=0.0001). No significant complications occurred in either arm. PVAI was more likely to achieve control of AF/AT off antiarrhythmic drugs (57% versus 27%, P=0.02) at 2+/-1 years of follow-up. A single PVAI procedure is more likely to result in freedom from AF/AT off antiarrhythmic drugs than CPVA supplemented by complex fractionated electrogram ablation in select patients.

Research paper thumbnail of When should we recommend catheter ablation for patients with the Wolff???Parkinson???White syndrome?

Current Opinion in Internal Medicine, 2008

Catheter ablation has been proven as very effective and safe therapy for patients with symptomati... more Catheter ablation has been proven as very effective and safe therapy for patients with symptomatic Wolff-Parkinson-White (WPW) syndrome. Its application in asymptomatic individuals with WPW pattern remains controversial. This review will elaborate on the role of catheter ablation in symptomatic and asymptomatic patients with WPW pattern on ECG. Several recent prospective studies evaluated invasive risk stratification followed by prophylactic catheter ablation in asymptomatic patients with WPW pattern. Inducibility of arrhythmias in these patients during invasive electrophysiological study was shown to predict the development of future symptomatic arrhythmias. Although ablation of accessory pathways performed in &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;inducible&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; patients decreased the incidence of subsequent symptomatic arrhythmias, the studies were not powered to detect a reduction in life-threatening arrhythmias. Radiofrequency catheter ablation remains the first-line therapy for patients with symptomatic WPW syndrome. Invasive electrophysiological study and possible ablation of accessory pathway may be offered to well informed asymptomatic individuals with WPW if they are willing to trade the very small risk of subsequent sudden death or incapacity for a small immediate procedural risk of serious complications or death. Asymptomatic patients may require invasive risk stratification and possible catheter ablation for important social or professional reasons.

Research paper thumbnail of A Detailed Description and Assessment of Outcomes of Patients With Hospital Recorded QTc Prolongation

The American Journal of Cardiology, 2015

Corrected QT (QTc) interval prolongation has been shown to be an independent predictor of mortali... more Corrected QT (QTc) interval prolongation has been shown to be an independent predictor of mortality in many clinical settings and is a common finding in hospitalized patients. The causes and outcomes of patients with extreme QTc interval prolongation during a hospital admission are poorly described. The aim of this study was to prospectively identify patients with automated readings of QTc intervals &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;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;550 ms at 1 academic tertiary hospital. One hundred seventy-two patients with dramatic QTc interval prolongation (574 ± 53 ms) were identified (mean age 67.6 ± 15.1 years, 48% women). Most patients had underlying heart disease (60%), predominantly ischemic cardiomyopathy (43%). At lease 1 credible and presumed reversible cause associated with QTc interval prolongation was identified in 98% of patients. The most common culprits were QTc interval-prolonging medications, which were deemed most responsible in 48% of patients, with 25% of these patients taking ≥2 offending drugs. Two patients were diagnosed with congenital long-QT syndrome. Patients with electrocardiograms available before and after hospital admission demonstrated significantly lower preadmission and postdischarge QTc intervals compared with the QTc intervals recorded in the hospital. In conclusion, in-hospital mortality was high in the study population (29%), with only 4% of patients experiencing arrhythmic deaths, all of which were attributed to secondary causes.

Research paper thumbnail of Early repolarization is associated with symptoms in patients with type 1 and type 2 long QT syndrome

Heart Rhythm, 2014

Early repolarization (ER) is associated with an increased risk for death from cardiac causes. Rec... more Early repolarization (ER) is associated with an increased risk for death from cardiac causes. Recent evidence supports ER&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s role as a modifier and/or predictor of risk in many cardiac conditions. The purpose of this study was to determine the prevalence of ER among genotype-positive patients with long QT syndrome (LQTS) and evaluate its utility in predicting the risk of symptoms. ER was defined as QRS slurring and/or notching associated with ≥1-mV QRS-ST junction (J-point) elevation in at least 2 contiguous leads, excluding the anterior precordial leads. The ECG with the most prominent ER was used for analysis. Major ER was defined as ≥ 2-mm J-point elevation. Symptoms of LQTS included cardiac syncope, documented polymorphic ventricular tachycardia (VT), and resuscitated cardiac arrest. One hundred thirteen patients (mean age 41 ± 19 years; 63 female) were reviewed, among whom 414 (mean 3.7 ± 1.5) ECGs were analyzed. Of these, 30 patients (27%) with a history of symptoms. Fifty patients (44%) had ER, and 19 patients (17%) had major ER. Patients with major ER were not different from patients without major ER with respect to age, sex, long QT type, longest QTc recorded, number of patients with QTc &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;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;500 ms, or use of beta-blockade. Univariate and independent predictors of symptom status included the presence of major ER, longest QTc recorded &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;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;500 ms, and female sex. ER ≥2 mm was the strongest independent predictor of symptom status related to LQTS, along with female sex and QTc &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;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;500 ms.

Research paper thumbnail of Syncope

Handbook of Clinical Neurology, 2008

Research paper thumbnail of Unusual Marker Annotation: Something Shifty is Going On

Pacing and Clinical Electrophysiology, 2010

Research paper thumbnail of Model-based navigation of left and right ventricular leads to optimal targets for cardiac resynchronization therapy: a single-center feasibility study

Circulation. Arrhythmia and electrophysiology, 2014

Left ventricular (LV) and right ventricular pacing site characteristics have been shown to influe... more Left ventricular (LV) and right ventricular pacing site characteristics have been shown to influence response to cardiac resynchronization therapy (CRT). This study aimed to determine the clinical feasibility of image-guided lead delivery using a 3-dimensional navigational model displaying both LV and right ventricular (RV) pacing targets. Serial echocardiographic measures of clinical response and procedural metrics were evaluated. Thirty-one consecutive patients underwent preimplant cardiac MRI with the generation of a 3-dimensional navigational model depicting optimal segmental targets for LV and RV leads. Lead delivery was guided by the model in matched views to intraprocedural fluoroscopy. Blinded assessment of final lead tip location was performed from postprocedural cardiac computed tomography. Clinical and LV remodeling response criteria were assessed at baseline, 3 months, and 6 months using a 6-minute hall walk, quality of life questionnaire, and echocardiography. Mean age ...

Research paper thumbnail of Syncope: Review of Monitoring Modalities

Current Cardiology Reviews, 2008

Elucidating the underlying cause of unexplained syncope, palpitations or other possible arrhythmi... more Elucidating the underlying cause of unexplained syncope, palpitations or other possible arrhythmia-related symptoms is a formidable clinical challenge. Cardiac monitoring supplements the most important &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;test&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; in patients with syncope or palpitations, that of a thoughtful history and physical examination. Ideally, comprehensive physiologic monitoring during spontaneous symptoms would constitute what, at present, is an unattainable gold standard test for establishing a cause. Short of that goal, establishing an accurate symptom-rhythm correlation can often provide a diagnosis. Ambulatory outpatient monitoring is a powerful diagnostic tool for the evaluation of cardiac arrhythmias. Evolving technologies have provided a vast array of monitoring options for patients suspected of having cardiac arrhythmias, with each modality differing in duration of monitoring, quality of recording, convenience and invasiveness. Holter monitors, event monitors and external loop recorders are non-invasive and provide easily accessible short-term monitoring solutions. In instances where the diagnosis remains elusive, a more long-term strategy with an implantable loop recorder may be the preferred path.

Research paper thumbnail of ICD Problems-Is the Device to Blame?

Pacing and Clinical Electrophysiology, 2011

Research paper thumbnail of Intracardiac ECHO Integration With Three Dimensional Mapping: Role in AF Ablation

Journal of Atrial Fibrillation, 2008

Catheter ablation of atrial fibrillation (AF) is typically guided by 3D mapping. This involves po... more Catheter ablation of atrial fibrillation (AF) is typically guided by 3D mapping. This involves point-by-point reconstruction of the 3D virtual anatomy and may be time consuming and require substantial fluoroscopy exposure. Intracardiac echocardiography (ICE) affords real time ...

Research paper thumbnail of Central Venous Occlusion Is Not an Obstacle to Device Upgrade with the Assistance of Laser Extraction

Pacing and Clinical Electrophysiology, 2005

To assess the efficacy and safety of laser-assisted lead extraction for upgrade of existing pacem... more To assess the efficacy and safety of laser-assisted lead extraction for upgrade of existing pacemakers and defibrillators in patients with central venous obstruction. Implantable cardiac defibrillators and biventricular pacing have become the accepted therapeutic measures for patients with congestive heart failure. Many patients who are candidates for device therapy, however, already have existing right ventricular leads and the presence of central venous obstruction. Upgrade of existing devices in these patients is a dilemma, which is increasingly encountered by device-implanting physicians. Laser-assisted extraction of existing leads can facilitate access for device upgrade and provide an alternative to lead abandonment and contralateral implant. We review our experience with laser-assisted lead extraction in patients, referred for upgrade of existing devices, who were found to have, or known to have, ipsilateral subclavian vein occlusion. Over the past 3 years, 18 patients (13 men, 5 women; mean age 63.9 +/- 16 years) with subclavian vein occlusion underwent successful laser-assisted lead extraction (total 29 leads) and upgrade of existing leads to defibrillators and/or biventricular systems. Mean implant duration prior to extraction was 70.8 +/- 43.5 (11-192) months. Cannulation of the coronary sinus and placement of a transvenous left ventricular lead were achieved in all 13 patients in whom it was attempted. No complications occurred. Laser-assisted lead extraction is a safe and effective approach, allowing for ipsilateral device upgrade in patients with existing devices and central venous obstruction.

Research paper thumbnail of Silent Conduction

Pacing and Clinical Electrophysiology, 2007

A 69-year-old man with a history of hypertension and symptomatic paroxysmal atrial flutter underw... more A 69-year-old man with a history of hypertension and symptomatic paroxysmal atrial flutter underwent radiofrequency ablation. A four catheter study was performed with a diagnostic duodecapolar catheter placed in the lateral right atrium along the crista terminalis with the distal pole (TA 1,2) situated in the low lateral right atrium (lateral to the ablation line) and the proximal catheter (TA 9,10) at the high lateral right atrium. A decapolar coronary sinus (CS) catheter was sited with proximal poles 9 and 10 at the coronary sinus ostium. The patient was in tachycardia at the start of the procedure, and electrograms from the halo catheter combined with entrainment from the tricuspid isthmus revealed typical counterclockwise isthmus-dependent atrial flutter. A deflectable 8-mm ablation catheter was placed in the right ventricle and then withdrawn from the tricuspid annulus to the subeustachian ridge to map the atrial signal along the cavotricuspid isthmus (CTI). The largest atrial signal was targeted near the subeustachian ridge, 1 and application of radiofrequency (RF) energy at this site resulted in termination of flutter. Subsequent pacing from the proximal coronary sinus (CS 9,10) and septal tricuspid isthmus revealed the atrial activation patterns illustrated in . Has clockwise isthmus conduction block been achieved?

Research paper thumbnail of Differential Entrainment Distinguishes Atrioventricular Nodal Reentry Tachycardia from Atrioventricular Reentrant Tachycardia

Pacing and Clinical Electrophysiology, 2010

Entrainment from the right ventricular (RV) apex and the base has been used to distinguish atriov... more Entrainment from the right ventricular (RV) apex and the base has been used to distinguish atrioventricular reentrant tachycardia (AVRT) from atrioventricular nodal reentry tachycardia (AVNRT). The difference in the entrainment response from the RV apex in comparison with the RV base has not been tested. Fifty-nine consecutive patients referred for ablation of supraventricular tachycardia (SVT) were included. Entrainment of SVT was performed from the RV apex and base, pacing at 10-40-ms faster than the tachycardia cycle length. SA interval was calculated from stimulus to earliest atrial electrogram. Ventricle to atrium (VA) interval was measured from the RV electrogram (apex and base) to the earliest atrial electrogram during tachycardia. The SA-VA interval from apex and base was measured and the difference between them was calculated. Thirty-six AVNRT and 23 AVRT patients were enrolled. Mean age was 44 ± 12 years; 52% were male. The [SA-VA]apex-[SA-VA]base was demonstrable in 84.7% of patients and measured -9.4 ± 6.6 in AVNRT and 10 ± 11.3 in AVRT, 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;amp;amp;lt; 0.001. The difference was negative for all AVNRT cases and positive for all septal accessory pathways (APs). The difference between entrainment from the apex and base is readily performed and is diagnostic for all AVNRTs and septal APs.

Research paper thumbnail of Feasibility of Magnetic Resonance Imaging in Patients with an Implantable Loop Recorder

Pacing and Clinical Electrophysiology, 2008

The implantable loop recorder (ILR) is a useful tool in the diagnosis of syncope. Our understandi... more The implantable loop recorder (ILR) is a useful tool in the diagnosis of syncope. Our understanding of their functional and safety profile in interfering environments such as magnetic resonance imaging (MRI) becomes increasingly important as they become more prevalent. We report four patients with an ILR who underwent MRI. The ILR memory was cleared before MRI and no changes were made to programmed settings. Device interrogation took place immediately after the scan. Patients were surveyed for device movement and heating, in addition to cardiopulmonary symptoms after their MRI. Following MRI scanning, all patients were asymptomatic and no device movement or heating was observed. In addition, the functionality of the device remained unaffected. Artifacts mimicking arrhythmias were seen in all ILR patients regardless of the type of MRI scan. MRI scanning of ILR patients can be performed without harm to patient or device, but artifacts that could be mistaken for a tachyarrhythmia are seen frequently.

Research paper thumbnail of Current of Injury Predicts Acute Performance of Catheter-Delivered Active Fixation Pacing Leads

Pacing and Clinical Electrophysiology, 2007

During pacemaker lead (PPML) implantation, the implanter must assess lead stability (fixation) an... more During pacemaker lead (PPML) implantation, the implanter must assess lead stability (fixation) and pacing threshold adequacy. Implanters rely principally on lead impedance (IMP) and pacing threshold measurements after fixation of the PPML to determine adequacy of pacing sites. Continuously monitoring lead parameters during fixation might better identify predictors of acute lead stability and performance. At the time of PPML implantation with a catheter delivered, fixed screw, 4-Fr PPML (Medtronic 3830, Minneapolis, MN, USA) patients underwent measurements of R-wave amplitude, slew rate, and current of injury (COI) (maximum and at 80 ms) during each turn of the helix. Lead stability was tested with traction applied to the lead body. Eighteen patients (age 70 +/- 9 years, 9 males) were studied. Right ventricular lead positioning was attempted 43 times; 26 positions demonstrated good fixation and 18 had satisfactory threshold. Sites of good fixation consistently showed larger COI (maximum and at 80 ms) compared to poor fixation sites throughout each turn of the helix; R wave, slew rate, and IMP did not differ significantly. When all measures of COI were examined in a stepwise regression model only the final measure of COI at 80 ms proved significantly associated with acute stability (P = 0.032). Lead stability and threshold adequacy are predictable from assessment of the magnitude of injury current. Continuous monitoring of lead parameters during fixation does not appear to confer any benefit over assessment of the parameters after final rotation of the lead. A negative COI is associated with poor threshold and/or fixation.

Research paper thumbnail of Evaluation of the Young Patient Resuscitated from Ventricular Fibrillation

Cardiac Electrophysiology Clinics, 2011

Cardiac Electrophysiology Clinics, Volume 3, Issue 4, Pages 593-608, December 2011, Authors:Rajes... more Cardiac Electrophysiology Clinics, Volume 3, Issue 4, Pages 593-608, December 2011, Authors:Rajesh N. Subbiah, MBBS, PhD; Peter Leong-Sit, MD; Lorne J. Gula, MD; Allan C. Skanes, MD; James A. White, MD; Raymond Yee, MD; George J. Klein, MD; Andrew D. Krahn, MD.

Research paper thumbnail of Fused 3-dimensional whole-heart coronary artery, coronary vein and myocardial scar imaging at 3 T: Feasibility in patients with ischemic and non-ischemic cardiomyopathy

Journal of Cardiovascular Magnetic Resonance, 2010

Research paper thumbnail of Reduced Intrathoracic Impedance Correlates with Poor Renal Function in Heart Failure Patients

Journal of Cardiac Failure, 2014

Research paper thumbnail of Investigating syncope: a review

Current opinion in cardiology, 2006

This review focuses on recent literature on the cardiovascular investigation of syncope. Syncope ... more This review focuses on recent literature on the cardiovascular investigation of syncope. Syncope is a common and complex clinical entity with many varied etiologies, the diagnosis of which can often be elusive. Recent advances in the area of investigation in syncope include improvements in technologies for arrhythmia event monitoring and an increase in applicability and efficacy of traditional investigations. These advances have increased our ability to manage syncope. A better understanding of the etiology of syncope in certain cohorts has allowed tailoring of investigations and management of syncope. This is evident when syncope occurs in the presence of structural heart disease, which is associated with a higher incidence of arrhythmias and an increased 1-year mortality. Patients with left-ventricular dysfunction should be considered candidates for an implantable cardioverter defibrillator based on heart function and syncopal presentation. In the absence of significant heart dise...

Research paper thumbnail of Effect of beta-blockers on QT dynamics in the long QT syndrome: measuring the benefit

Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology, 2014

Beta-blockers are the standard of care for the treatment of long QT syndrome (LQTS), and have bee... more Beta-blockers are the standard of care for the treatment of long QT syndrome (LQTS), and have been shown to reduce recurrent syncope and mortality in patients with type 1 LQTS (LQT1). Although beta-blockers have minimal effect on the resting corrected QT interval, their effect on the dynamics of the non-corrected QT interval is unknown, and may provide insight into their protective effects. Twenty-three patients from eight families with genetically distinct mutations for LQT1 performed exercise stress testing before and after beta-blockade. One hundred and fifty-two QT, QTc, and Tpeak-Tend intervals were measured before starting beta-blockers and compared with those at matched identical cycle lengths following beta-blockade. Beta-blockers demonstrated heart-rate-dependent effects on the QT and QTc intervals. In the slowest heart rate tertile (<90 b.p.m.), beta-blockade increased the QT and QTc intervals (QT: 405 vs. 409 ms; P = 0.06; QTc: 459 vs. 464 ms; P = 0.06). In the fastest...

Research paper thumbnail of A Randomized Controlled Trial of the Efficacy and Safety of Electroanatomic Circumferential Pulmonary Vein Ablation Supplemented by Ablation of Complex Fractionated Atrial Electrograms Versus Potential-Guided Pulmonary Vein Antrum Isolation Guided by Intracardiac Ultrasound

Circulation-arrhythmia and Electrophysiology, 2009

The study was conducted to compare relative safety and efficacy of pulmonary vein antrum isolatio... more The study was conducted to compare relative safety and efficacy of pulmonary vein antrum isolation (PVAI) using intracardiac echocardiographic guidance and circumferential pulmonary vein ablation (CPVA) for atrial fibrillation (AF) using radiofrequency energy. Sixty patients (81% men; 81% paroxysmal; age, 56+/-8 years) failing 2+/-1 antiarrhythmic drugs were randomly assigned to undergo CPVA (n=30) or PVAI (n=30) at 5 centers between December 2004 and October 2007. CPVA patients had circular lesions placed at least 1 cm outside of the veins. Ipsilateral veins were ablated en block with the end point of disappearance of potentials within the circular lesion. Left atrial roof line and mitral isthmus line were ablated without verification of block. For patients in AF postablation or with AF induced with programmed stimulation, complex fractionated electrograms were mapped and ablated to the end point of AF termination or disappearance of complex fractionated electrograms. PVAI did not include complex fractionated electrogram ablation. Esophageal temperature was monitored and kept within 2 degrees C of baseline or under 39 degrees C. Success was defined as absence of atrial tachyarrhythmias (AF/AT) off antiarrhythmic drugs. There was no difference between CPVA and PVAI regarding to baseline variables, catheter used, duration of the procedure, or RF delivery. Fluoroscopy time was longer with PVAI (54+/-17 minutes versus 77+/-18 minutes, P=0.0001). No significant complications occurred in either arm. PVAI was more likely to achieve control of AF/AT off antiarrhythmic drugs (57% versus 27%, P=0.02) at 2+/-1 years of follow-up. A single PVAI procedure is more likely to result in freedom from AF/AT off antiarrhythmic drugs than CPVA supplemented by complex fractionated electrogram ablation in select patients.

Research paper thumbnail of When should we recommend catheter ablation for patients with the Wolff???Parkinson???White syndrome?

Current Opinion in Internal Medicine, 2008

Catheter ablation has been proven as very effective and safe therapy for patients with symptomati... more Catheter ablation has been proven as very effective and safe therapy for patients with symptomatic Wolff-Parkinson-White (WPW) syndrome. Its application in asymptomatic individuals with WPW pattern remains controversial. This review will elaborate on the role of catheter ablation in symptomatic and asymptomatic patients with WPW pattern on ECG. Several recent prospective studies evaluated invasive risk stratification followed by prophylactic catheter ablation in asymptomatic patients with WPW pattern. Inducibility of arrhythmias in these patients during invasive electrophysiological study was shown to predict the development of future symptomatic arrhythmias. Although ablation of accessory pathways performed in &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;inducible&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; patients decreased the incidence of subsequent symptomatic arrhythmias, the studies were not powered to detect a reduction in life-threatening arrhythmias. Radiofrequency catheter ablation remains the first-line therapy for patients with symptomatic WPW syndrome. Invasive electrophysiological study and possible ablation of accessory pathway may be offered to well informed asymptomatic individuals with WPW if they are willing to trade the very small risk of subsequent sudden death or incapacity for a small immediate procedural risk of serious complications or death. Asymptomatic patients may require invasive risk stratification and possible catheter ablation for important social or professional reasons.

Research paper thumbnail of A Detailed Description and Assessment of Outcomes of Patients With Hospital Recorded QTc Prolongation

The American Journal of Cardiology, 2015

Corrected QT (QTc) interval prolongation has been shown to be an independent predictor of mortali... more Corrected QT (QTc) interval prolongation has been shown to be an independent predictor of mortality in many clinical settings and is a common finding in hospitalized patients. The causes and outcomes of patients with extreme QTc interval prolongation during a hospital admission are poorly described. The aim of this study was to prospectively identify patients with automated readings of QTc intervals &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;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;550 ms at 1 academic tertiary hospital. One hundred seventy-two patients with dramatic QTc interval prolongation (574 ± 53 ms) were identified (mean age 67.6 ± 15.1 years, 48% women). Most patients had underlying heart disease (60%), predominantly ischemic cardiomyopathy (43%). At lease 1 credible and presumed reversible cause associated with QTc interval prolongation was identified in 98% of patients. The most common culprits were QTc interval-prolonging medications, which were deemed most responsible in 48% of patients, with 25% of these patients taking ≥2 offending drugs. Two patients were diagnosed with congenital long-QT syndrome. Patients with electrocardiograms available before and after hospital admission demonstrated significantly lower preadmission and postdischarge QTc intervals compared with the QTc intervals recorded in the hospital. In conclusion, in-hospital mortality was high in the study population (29%), with only 4% of patients experiencing arrhythmic deaths, all of which were attributed to secondary causes.

Research paper thumbnail of Early repolarization is associated with symptoms in patients with type 1 and type 2 long QT syndrome

Heart Rhythm, 2014

Early repolarization (ER) is associated with an increased risk for death from cardiac causes. Rec... more Early repolarization (ER) is associated with an increased risk for death from cardiac causes. Recent evidence supports ER&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s role as a modifier and/or predictor of risk in many cardiac conditions. The purpose of this study was to determine the prevalence of ER among genotype-positive patients with long QT syndrome (LQTS) and evaluate its utility in predicting the risk of symptoms. ER was defined as QRS slurring and/or notching associated with ≥1-mV QRS-ST junction (J-point) elevation in at least 2 contiguous leads, excluding the anterior precordial leads. The ECG with the most prominent ER was used for analysis. Major ER was defined as ≥ 2-mm J-point elevation. Symptoms of LQTS included cardiac syncope, documented polymorphic ventricular tachycardia (VT), and resuscitated cardiac arrest. One hundred thirteen patients (mean age 41 ± 19 years; 63 female) were reviewed, among whom 414 (mean 3.7 ± 1.5) ECGs were analyzed. Of these, 30 patients (27%) with a history of symptoms. Fifty patients (44%) had ER, and 19 patients (17%) had major ER. Patients with major ER were not different from patients without major ER with respect to age, sex, long QT type, longest QTc recorded, number of patients with QTc &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;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;500 ms, or use of beta-blockade. Univariate and independent predictors of symptom status included the presence of major ER, longest QTc recorded &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;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;500 ms, and female sex. ER ≥2 mm was the strongest independent predictor of symptom status related to LQTS, along with female sex and QTc &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;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;500 ms.

Research paper thumbnail of Syncope

Handbook of Clinical Neurology, 2008

Research paper thumbnail of Unusual Marker Annotation: Something Shifty is Going On

Pacing and Clinical Electrophysiology, 2010

Research paper thumbnail of Model-based navigation of left and right ventricular leads to optimal targets for cardiac resynchronization therapy: a single-center feasibility study

Circulation. Arrhythmia and electrophysiology, 2014

Left ventricular (LV) and right ventricular pacing site characteristics have been shown to influe... more Left ventricular (LV) and right ventricular pacing site characteristics have been shown to influence response to cardiac resynchronization therapy (CRT). This study aimed to determine the clinical feasibility of image-guided lead delivery using a 3-dimensional navigational model displaying both LV and right ventricular (RV) pacing targets. Serial echocardiographic measures of clinical response and procedural metrics were evaluated. Thirty-one consecutive patients underwent preimplant cardiac MRI with the generation of a 3-dimensional navigational model depicting optimal segmental targets for LV and RV leads. Lead delivery was guided by the model in matched views to intraprocedural fluoroscopy. Blinded assessment of final lead tip location was performed from postprocedural cardiac computed tomography. Clinical and LV remodeling response criteria were assessed at baseline, 3 months, and 6 months using a 6-minute hall walk, quality of life questionnaire, and echocardiography. Mean age ...

Research paper thumbnail of Syncope: Review of Monitoring Modalities

Current Cardiology Reviews, 2008

Elucidating the underlying cause of unexplained syncope, palpitations or other possible arrhythmi... more Elucidating the underlying cause of unexplained syncope, palpitations or other possible arrhythmia-related symptoms is a formidable clinical challenge. Cardiac monitoring supplements the most important &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;test&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; in patients with syncope or palpitations, that of a thoughtful history and physical examination. Ideally, comprehensive physiologic monitoring during spontaneous symptoms would constitute what, at present, is an unattainable gold standard test for establishing a cause. Short of that goal, establishing an accurate symptom-rhythm correlation can often provide a diagnosis. Ambulatory outpatient monitoring is a powerful diagnostic tool for the evaluation of cardiac arrhythmias. Evolving technologies have provided a vast array of monitoring options for patients suspected of having cardiac arrhythmias, with each modality differing in duration of monitoring, quality of recording, convenience and invasiveness. Holter monitors, event monitors and external loop recorders are non-invasive and provide easily accessible short-term monitoring solutions. In instances where the diagnosis remains elusive, a more long-term strategy with an implantable loop recorder may be the preferred path.

Research paper thumbnail of ICD Problems-Is the Device to Blame?

Pacing and Clinical Electrophysiology, 2011

Research paper thumbnail of Intracardiac ECHO Integration With Three Dimensional Mapping: Role in AF Ablation

Journal of Atrial Fibrillation, 2008

Catheter ablation of atrial fibrillation (AF) is typically guided by 3D mapping. This involves po... more Catheter ablation of atrial fibrillation (AF) is typically guided by 3D mapping. This involves point-by-point reconstruction of the 3D virtual anatomy and may be time consuming and require substantial fluoroscopy exposure. Intracardiac echocardiography (ICE) affords real time ...

Research paper thumbnail of Central Venous Occlusion Is Not an Obstacle to Device Upgrade with the Assistance of Laser Extraction

Pacing and Clinical Electrophysiology, 2005

To assess the efficacy and safety of laser-assisted lead extraction for upgrade of existing pacem... more To assess the efficacy and safety of laser-assisted lead extraction for upgrade of existing pacemakers and defibrillators in patients with central venous obstruction. Implantable cardiac defibrillators and biventricular pacing have become the accepted therapeutic measures for patients with congestive heart failure. Many patients who are candidates for device therapy, however, already have existing right ventricular leads and the presence of central venous obstruction. Upgrade of existing devices in these patients is a dilemma, which is increasingly encountered by device-implanting physicians. Laser-assisted extraction of existing leads can facilitate access for device upgrade and provide an alternative to lead abandonment and contralateral implant. We review our experience with laser-assisted lead extraction in patients, referred for upgrade of existing devices, who were found to have, or known to have, ipsilateral subclavian vein occlusion. Over the past 3 years, 18 patients (13 men, 5 women; mean age 63.9 +/- 16 years) with subclavian vein occlusion underwent successful laser-assisted lead extraction (total 29 leads) and upgrade of existing leads to defibrillators and/or biventricular systems. Mean implant duration prior to extraction was 70.8 +/- 43.5 (11-192) months. Cannulation of the coronary sinus and placement of a transvenous left ventricular lead were achieved in all 13 patients in whom it was attempted. No complications occurred. Laser-assisted lead extraction is a safe and effective approach, allowing for ipsilateral device upgrade in patients with existing devices and central venous obstruction.

Research paper thumbnail of Silent Conduction

Pacing and Clinical Electrophysiology, 2007

A 69-year-old man with a history of hypertension and symptomatic paroxysmal atrial flutter underw... more A 69-year-old man with a history of hypertension and symptomatic paroxysmal atrial flutter underwent radiofrequency ablation. A four catheter study was performed with a diagnostic duodecapolar catheter placed in the lateral right atrium along the crista terminalis with the distal pole (TA 1,2) situated in the low lateral right atrium (lateral to the ablation line) and the proximal catheter (TA 9,10) at the high lateral right atrium. A decapolar coronary sinus (CS) catheter was sited with proximal poles 9 and 10 at the coronary sinus ostium. The patient was in tachycardia at the start of the procedure, and electrograms from the halo catheter combined with entrainment from the tricuspid isthmus revealed typical counterclockwise isthmus-dependent atrial flutter. A deflectable 8-mm ablation catheter was placed in the right ventricle and then withdrawn from the tricuspid annulus to the subeustachian ridge to map the atrial signal along the cavotricuspid isthmus (CTI). The largest atrial signal was targeted near the subeustachian ridge, 1 and application of radiofrequency (RF) energy at this site resulted in termination of flutter. Subsequent pacing from the proximal coronary sinus (CS 9,10) and septal tricuspid isthmus revealed the atrial activation patterns illustrated in . Has clockwise isthmus conduction block been achieved?

Research paper thumbnail of Differential Entrainment Distinguishes Atrioventricular Nodal Reentry Tachycardia from Atrioventricular Reentrant Tachycardia

Pacing and Clinical Electrophysiology, 2010

Entrainment from the right ventricular (RV) apex and the base has been used to distinguish atriov... more Entrainment from the right ventricular (RV) apex and the base has been used to distinguish atrioventricular reentrant tachycardia (AVRT) from atrioventricular nodal reentry tachycardia (AVNRT). The difference in the entrainment response from the RV apex in comparison with the RV base has not been tested. Fifty-nine consecutive patients referred for ablation of supraventricular tachycardia (SVT) were included. Entrainment of SVT was performed from the RV apex and base, pacing at 10-40-ms faster than the tachycardia cycle length. SA interval was calculated from stimulus to earliest atrial electrogram. Ventricle to atrium (VA) interval was measured from the RV electrogram (apex and base) to the earliest atrial electrogram during tachycardia. The SA-VA interval from apex and base was measured and the difference between them was calculated. Thirty-six AVNRT and 23 AVRT patients were enrolled. Mean age was 44 ± 12 years; 52% were male. The [SA-VA]apex-[SA-VA]base was demonstrable in 84.7% of patients and measured -9.4 ± 6.6 in AVNRT and 10 ± 11.3 in AVRT, 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;amp;amp;lt; 0.001. The difference was negative for all AVNRT cases and positive for all septal accessory pathways (APs). The difference between entrainment from the apex and base is readily performed and is diagnostic for all AVNRTs and septal APs.

Research paper thumbnail of Feasibility of Magnetic Resonance Imaging in Patients with an Implantable Loop Recorder

Pacing and Clinical Electrophysiology, 2008

The implantable loop recorder (ILR) is a useful tool in the diagnosis of syncope. Our understandi... more The implantable loop recorder (ILR) is a useful tool in the diagnosis of syncope. Our understanding of their functional and safety profile in interfering environments such as magnetic resonance imaging (MRI) becomes increasingly important as they become more prevalent. We report four patients with an ILR who underwent MRI. The ILR memory was cleared before MRI and no changes were made to programmed settings. Device interrogation took place immediately after the scan. Patients were surveyed for device movement and heating, in addition to cardiopulmonary symptoms after their MRI. Following MRI scanning, all patients were asymptomatic and no device movement or heating was observed. In addition, the functionality of the device remained unaffected. Artifacts mimicking arrhythmias were seen in all ILR patients regardless of the type of MRI scan. MRI scanning of ILR patients can be performed without harm to patient or device, but artifacts that could be mistaken for a tachyarrhythmia are seen frequently.

Research paper thumbnail of Current of Injury Predicts Acute Performance of Catheter-Delivered Active Fixation Pacing Leads

Pacing and Clinical Electrophysiology, 2007

During pacemaker lead (PPML) implantation, the implanter must assess lead stability (fixation) an... more During pacemaker lead (PPML) implantation, the implanter must assess lead stability (fixation) and pacing threshold adequacy. Implanters rely principally on lead impedance (IMP) and pacing threshold measurements after fixation of the PPML to determine adequacy of pacing sites. Continuously monitoring lead parameters during fixation might better identify predictors of acute lead stability and performance. At the time of PPML implantation with a catheter delivered, fixed screw, 4-Fr PPML (Medtronic 3830, Minneapolis, MN, USA) patients underwent measurements of R-wave amplitude, slew rate, and current of injury (COI) (maximum and at 80 ms) during each turn of the helix. Lead stability was tested with traction applied to the lead body. Eighteen patients (age 70 +/- 9 years, 9 males) were studied. Right ventricular lead positioning was attempted 43 times; 26 positions demonstrated good fixation and 18 had satisfactory threshold. Sites of good fixation consistently showed larger COI (maximum and at 80 ms) compared to poor fixation sites throughout each turn of the helix; R wave, slew rate, and IMP did not differ significantly. When all measures of COI were examined in a stepwise regression model only the final measure of COI at 80 ms proved significantly associated with acute stability (P = 0.032). Lead stability and threshold adequacy are predictable from assessment of the magnitude of injury current. Continuous monitoring of lead parameters during fixation does not appear to confer any benefit over assessment of the parameters after final rotation of the lead. A negative COI is associated with poor threshold and/or fixation.