Left Ventricle Research Papers - Academia.edu (original) (raw)

In presence of aortic stenosis, a jet is produced downstream of the aortic valve annulus during systole. The vena contracta corresponds to the location where the cross-sectional area of the flow jet is minimal. The maximal transvalvular... more

In presence of aortic stenosis, a jet is produced downstream of the aortic valve annulus during systole. The vena contracta corresponds to the location where the cross-sectional area of the flow jet is minimal. The maximal transvalvular pressure gradient (TPG(max)) is the difference between the static pressure in the left ventricle and that in the vena contracta. TPG(max) is highly time-dependent over systole and is known to depend upon the transvalvular flow rate, the effective orifice area (EOA) of the aortic valve and the cross-sectional area of the left ventricular outflow tract. However, it is still unclear how these parameters modify the TPG(max) waveform. We thus derived an explicit analytical model to describe the instantaneous TPG(max) across the aortic valve during systole. This theoretical model was validated with in vivo experiments obtained in 19 pigs with supravalvular aortic stenosis. Instantaneous TPG(max) was measured by catheter and its waveform was compared with the one determined from the derived equation. Our results showed a very good concordance between the measured and predicted instantaneous TPG(max). Total relative error and mean absolute error were on average 9.4+/-4.9% and 2.1+/-1.1 mmHg, respectively. The analytical model proposed and validated in this study provides new insight into the behaviour of the TPG(max) and thus of the aortic pressure at the level of vena contracta. Because the static pressure at the coronary inlet is similar to that at the vena contracta, the proposed equation will permit to further examine the impact of aortic stenosis on coronary blood flow.

Description of the heart as a pump has been dominated by models based on elastance and compliance. Here, we are presenting a somewhat new concept of time-varying passive and active elastance. The mathematical basis of time-varying... more

Description of the heart as a pump has been dominated by models based on elastance and compliance. Here, we are presenting a somewhat new concept of time-varying passive and active elastance. The mathematical basis of time-varying elastance of the ventricle is presented. We have defined elastance in terms of the relationship between ventricular pressure and volume, as: dP = EdV + VdE, where E includes passive (Ep) and active (Ea) elastance. By incorporating this concept in left ventricular (LV) models to simulate filling and systolic phases, we have obtained the time-varying expression for Ea and the LV-volume dependent expression for Ep. Using the patient's catheterization-ventriculogram data, the values of passive and active elastance are computed. Ea is expressed as [formula: see text] Epis represented as: [formula: see text]. Ea is deemed to represent a measure of LV contractility. Hence, Peak dP/dt and ejection fraction (EF) are computed from the monitored data and used as ...

Introduction Pulse pressure (PP) has been reported as an independent predictor of cardiovascular mortality in hemodialysis patients. In this study, we aimed to investigate association of PP with echocardiographic and vascular structural... more

Introduction Pulse pressure (PP) has been reported as an independent predictor of cardiovascular mortality in hemodialysis patients. In this study, we aimed to investigate association of PP with echocardiographic and vascular structural changes such as atherosclerosis and arterial calcifications in HD patients. Patients and methods In this cross-sectional study, 108 chronic hemodialysis patients (49 male, 59 female, mean age: 46 ± 13 years) were included.

Cardiac resynchronization therapy (CRT) can be an effective procedure for patients with heart failure but 30% of patients do not respond. This may be partially caused by the sub-optimal placement of the left ventricular lead. We... more

Cardiac resynchronization therapy (CRT) can be an effective procedure for patients with heart failure but 30% of patients do not respond. This may be partially caused by the sub-optimal placement of the left ventricular lead. We demonstrate how pre-procedural cardiac MR images can be used to assist CRT by integration of anatomical and functional information with live X-ray images. We evaluated our approach in 7 patients. Each patient underwent pre-CRT MRI scan using MultiHance contrast. This included whole heart imaging sequence; 3D tagged and cine imaging for function; and late enhancement imaging for scar. The MRI data were processed to yield a detailed anatomical model. Whole heart segmentation was achieved automatically using the Philips EP Planner and the coronary venous anatomy was manually segmented by a clinical expert. Functional information was derived using the Tomtec 4D LV-Analysis. The left ventricle was segmented into the standard 16 segment AHA model and the functional information could be added to this. If scar was present, this was segmented by an expert and added to the model. The implant was carried out using a Philips Allura X-ray system and the detailed cardiac model was registered to the X-ray fluoroscopy using multiple views of a catheter looped in the right atrium. There was complete freedom of movement of the X-ray system and respiratory motion compensation was achieved by tracking the diaphragm. The software framework was a specially modified version of the Philips EP Navigator. We validated the registration using balloon occlusion coronary veno-grams. The mean 2D target registration error for 7 patients was 1.3±0.68 mm. Furthermore, left lead deployment was successful in all patients.

There is an increasing demand for natural compounds that improve women's health by mimicking the critical benefits of estrogen to the bones and the cardiovascular system but avoiding its deleterious effects on the breast and uterus.... more

There is an increasing demand for natural compounds that improve women's health by mimicking the critical benefits of estrogen to the bones and the cardiovascular system but avoiding its deleterious effects on the breast and uterus. The estrogenic properties of glabridin, the major isoflavan in licorice root, were tested in view of the resemblance of its structure and lipophilicity to those of estradiol. The results indicate that glabridin is a phytoestrogen, binding to the human estrogen receptor and stimulating creatine kinase activity in rat uterus, epiphyseal cartilage, diaphyseal bone, aorta, and left ventricle of the heart. The stimulatory effects of 2.5-25 microg/animal glabridin were similar to those of 5 microg/animal estradiol. Chemical modification of glabridin showed that the position of the hydroxyl groups has a significant role in binding to the human estrogen receptor and in proliferation-inducing activity. Glabridin was found to be three to four times more active...

A three-dimensional computational fluid dynamics (CFD) method has been developed to simulate the flow in a pumping left ventricle. The proposed method uses magnetic resonance imaging (MRI) technology to provide a patient specific, time... more

A three-dimensional computational fluid dynamics (CFD) method has been developed to simulate the flow in a pumping left ventricle. The proposed method uses magnetic resonance imaging (MRI) technology to provide a patient specific, time dependent geometry of the ventricle to be simulated. Standard clinical imaging procedures were used in this study. A two-dimensional time-dependent orifice representation of the heart valves was used. The location and size of the valves is estimated based on additional long axis images through the valves. A semi-automatic grid generator was created to generate the calculation grid. Since the time resolution of the MR scans does not fit the requirements of the CFD calculations a third order bezier approximation scheme was developed to realize a smooth wall boundary and grid movement. The calculation was performed by a Navier–Stokes solver using the arbitrary Lagrange–Euler (ALE) formulation. Results show that during diastole, blood flow through the mitral valve forms an asymmetric jet, leading to an asymmetric development of the initial vortex ring. These flow features are in reasonable agreement with in vivo measurements but also show an extremely high sensitivity to the boundary conditions imposed at the inflow. Changes in the atrial representation severely alter the resulting flow field. These shortcomings will have to be addressed in further studies, possibly by inclusion of the real atrial geometry, and imply additional requirements for the clinical imaging processes.

Background Myocardial revascularization in presence of severe Left Ventricular Dysfunction (LVD) presents a challenging surgical scenario. To improve the results of this high risk procedure, off-pump revascularization is being... more

Background Myocardial revascularization in presence of severe Left Ventricular Dysfunction (LVD) presents a challenging surgical scenario. To improve the results of this high risk procedure, off-pump revascularization is being increasingly used; yet without conclusive evidence of definite benefit. Present study aims to assess the early outcome of coronary revascularization in presence of severe Left Ventricle (LV) dysfunction by off pump method as against conventional on- pump technique. Methods 125 consecutive cases of isolated coronary artery disease with severe LVD, having undergone Coronary Artery Bypass Grafting (CABG) over a two and a half year period (January 1, 2006 to June 30, 2008) were studied retrospectively. Group I consisted of 78 cases of Off-Pump Coronary Artery Bypass Grafting (OPCAB), while group II consisted of 47 cases of on-pump CABG. The follow up period was 5 to 30 months (mean 14 months). Results There were 5 hospital deaths, 3 in the OPCAB group and 2 in group II of on-pump CABG (p= ns). Two patients in the OPCAB group required conversion to on pump surgery due to hemodynamic instability. No patient in either group had recurrence of symptoms. Patients in both groups had comparable inotropic requirement, length of ICU stay and total hospital stay. There was no incidence of neurologic injury in either group. Blood transfusion requirement was significantly less in the OPCAB group (P p=0.01). Conclusions OPCAB is a safe and effective method in the presence of significant LVD. It may be preferentially applied to patients with pre-existing renal insufficiency.

Purpose To confirm the central role of antenatal echocardiography and necropsy in the prenatal diagnosis of rare congenital heart defects. Methods A 33-year-old woman undergoing second trimester scan using 2D transabdominal and Doppler... more

Purpose To confirm the central role of antenatal echocardiography and necropsy in the prenatal diagnosis of rare congenital heart defects. Methods A 33-year-old woman undergoing second trimester scan using 2D transabdominal and Doppler sonography. Results The echocardiographic examination showed, at the level of the four-chamber view, a predominant left ventricle with a rudimental right ventricle and a single artery emerging with failed visualization of the pulmonary trunk: a diagnosis of truncus arteriosus communis associated with tricuspid atresia and hypoplastic right heart was made. No other ultrasound-associated anomalies were seen. Fetal karyotype and 22q11.2 microdeletion for Di George syndrome were sought using cordocentesis performed at 21 weeks and both the results were normal. After extensive counselling, the couple opted for termination of pregnancy at 22 weeks gestation. Necroscopy confirmed the prenatal ultrasound diagnosis. Necroscopy of the heart was performed in a manner that resembled the fetal echocardiographic examination and revealed two atria, two atrio-ventricular valves with recognizable mitral and tricuspid morphology, a prevalent ventricle of left-type and a rudimental ventricle of right type and a ventricular septal defect. The common truncus was seen coming out above the ventricular septum, whilst the pulmonary arteries arise separated from the truncus communis. No other structural thoraco-abdominal anomalies were found. Conclusions A combined diagnostic strategy based on second trimester fetal echocardiography, genetic analysis and necroscopy has made identification of a rare congenital heart disease possible.

Brain edema formation is one of the most important mechanisms responsible for brain damage after ischemic stroke. Despite considerable efforts, no specific therapy is available yet. Arginine vasopressin (AVP) regulates cerebral water... more

Brain edema formation is one of the most important mechanisms responsible for brain damage after ischemic stroke. Despite considerable efforts, no specific therapy is available yet. Arginine vasopressin (AVP) regulates cerebral water homeostasis and has been involved in brain edema formation. In the current study, we investigated the role of AVP V1 and V2 receptors on brain damage, brain edema formation, and functional outcome after transient focal cerebral ischemia, a condition comparable with that of stroke patients undergoing thrombolysis. C57/BL6 mice were subjected to 60-min middle cerebral artery occlusion (MCAO) followed by 23 h of reperfusion. Five minutes after MCAO, 100 or 500 ng of [deamino-Pen(1), O-Me-Tyr(2), Arg(8)]-vasopressin (AVP V1 receptor antagonist) or [adamantaneacetyl(1), O-Et-D-Tyr(2), Val(4), Abu(6), Arg(8,9)]-vasopressin (AVP V2 receptor antagonist) were injected into the left ventricle. Inhibition of AVP V1 receptors reduced infarct volume in a dose-dependent manner by 54% and 70% (to 29+/-13 and 19+/-10 mm3 versus 63+/-17 mm3 in controls; P<0.001), brain edema formation by 67% (to 80.4%+/-1.0% versus 82.7%+/-1.2% in controls; P<0.001), blood-brain barrier disruption by 75% (P<0.001), and functional deficits 24 h after ischemia, while V2 receptor inhibition had no effect. The current findings indicate that AVP V1 but not V2 receptors are involved in the pathophysiology of secondary brain damage after focal cerebral ischemia. Although further studies are needed to clarify the mechanisms of neuroprotection, AVP V1 receptors seem to be promising targets for the treatment of ischemic stroke.