Munmohan Virdee

Left ventricular diastolic function assessed using Doppler tissue imaging in patients with hypertrophic cardiomyopathy: relation to symptoms and exercise capacity

Background: Conventional Doppler indices of left ventricular diastolic function do not correlate with symptoms or exercise capacity in patients with hypertrophic cardiomyopathy, because of their dependence on loading conditions. Diastolic mitral annular velocity measured using Doppler tissue imaging has been reported to be a preload independent index of left ventricular diastolic function. Objective: To determine the relation between diastolic annular velocities combined with conventional Doppler indices and symptoms or exercise capacity in hypertrophic cardiomyopathy. Methods: 85 patients with hypertrophic cardiomyopathy and 60 normal controls were studied. Diastolic mitral annular velocities, transmitral left ventricular filling, and pulmonary venous velocities were measured. Results: Early diastolic velocities at lateral and septal annulus were lower in patients with hypertrophic cardiomyopathy than in controls (lateral Ea: 10 (3) v 18 (4) cm/s, p < 0.0001; septal Ea: 7 (2) v 12 (3) cm/s, p < 0.0001). Unlike conventional Doppler indices alone, transmitral early left ventricular filling velocity (E) to lateral Ea ratio correlated inversely with peak oxygen consumption (r = −0.42, p < 0.0001). Patients in New York Heart Association (NYHA) class III had a higher transmitral E to lateral Ea ratio (12.0 (4.6)) than those in NYHA class II (7.6 (3.1), p < 0.005) or class I (6.6 (2.6), p < 0.0001). Conclusions: Early diastolic mitral annular velocities are reduced in patients with hypertrophic cardiomyopathy. Unlike conventional Doppler indices alone, the transmitral E to lateral Ea ratio correlates with NYHA functional class and exercise capacity.

Left ventricular lead placement in cardiac resynchronization therapy: where and how?

Cardiac resynchronization therapy (CRT) offers proven benefit to patients with refractory symptomatic chronic heart failure (New York Heart Association Class III or IV), severe left ventricular (LV) systolic dysfunction (LV ejection fraction <35%), and LV dyssynchrony (QRS width >120 ms). Cardiac resynchronization therapy has the potential to improve survival and functional capacity, reduce hospital admissions, and promote LV reverse remodelling. Although difficult to truly evaluate, up to 30% of patients do not attain symptomatic benefit. Factors associated with a poor outcome include inappropriate patient selection, inadequate device programming, presence of myocardial scar, and suboptimal LV lead placement. Left ventricular dyssynchrony is an important determinant of CRT response, although at present no reliable single measure to identify patients beyond QRS width has been identified. In this review, we discuss the effect of LV lead placement to pace the region of maximal dyssynchrony, the impact of total scar burden on response, and the relationship between LV lead position and localized scar. Consideration is also given to prospectively defining placement of the LV lead including surgical epicardial lead positioning.

Effect of Low-Amplitude Two-Dimensional Radial Strain at Left Ventricular Pacing Sites on Response to Cardiac Resynchronization Therapy

BACKGROUND Left ventricular (LV) lead placement to areas of scar has detrimental effects on response to cardiac resynchronization therapy (CRT). Speckle-tracking radial two-dimensional strain offers assessment of the extent of regional myocardial deformation. The aim of this study was to assess the impact of LV lead placement at areas of low-amplitude strain on CRT response. METHODS The optimal cutoff of radial strain amplitude at the LV pacing site associated with an unfavorable CRT response was determined in a derivation group (n = 65) and then tested in a second consecutive validation group (n = 75) of patients with heart failure. Patients had concordant LV leads if placed at the most delayed site, and dyssynchrony was defined as anteroseptal to posterior delay ≥ 130 msec. CRT response was defined as a ≥15% reduction in LV end-systolic volume at 6 months. RESULTS In the derivation group, a derived cutoff for radial strain amplitude of <9.8% defined low-amplitude segments (LAS) and had a high specificity but low sensitivity for predicting LV reverse remodeling, suggesting a strong negative predictive value. In the validation group, compared with patients without LAS at the LV pacing site, in patients with LAS (n = 16), CRT response was significantly lower (62.7% vs 31.3%, P < .05). By multivariate analysis, LV lead concordance and the absence of an LAS at the LV pacing site but not dyssynchrony were significantly related to CRT response. CONCLUSION LV lead placement over segments with two-dimensional radial strain amplitudes <9.8% is associated with poor outcomes of CRT.

The Impact of the Right Ventricular Lead Position on Response to Cardiac Resynchronization Therapy

Introduction: Left ventricular (LV) lead placement to the latest contracting area (concordant LV lead) is associated with better response to cardiac resynchronization therapy (CRT) compared to a discordant LV lead. However, the effect of the right ventricular (RV) lead site on CRT response is unclear. We investigated the relationship of the RV and LV lead positions on CRT response.

Prognostic Benefit of Optimum Left Ventricular Lead Position in Cardiac Resynchronization Therapy : Follow-Up of the TARGET Study Cohort (Targeted Left Ventricular Lead Placement to guide Cardiac Resynchronization Therapy)

OBJECTIVES This study was conducted to assess the impact of left ventricular (LV) lead position on longer-term survival after cardiac resynchronization therapy (CRT). BACKGROUND An optimal LV lead position in CRT is associated with improved clinical outcome. A strategy of speckle-tracking echocardiography can be used to guide the implanter to the site of latest activation and away from segments of low strain amplitude (scar). Long-term, prospective survival data according to LV lead position in CRT are limited. METHODS Data from a follow-up registry of 250 consecutive patients receiving CRT between June 2008 and July 2010 were studied. The study population comprised patients recruited to the derivation group and the subsequent TARGET (Targeted Left Ventricular Lead Placement to guide Cardiac Resynchronization Therapy) randomized, controlled trial. Final LV lead position was described, in relation to the pacing site determined by pre-procedure speckle-tracking echocardiography, as optimal (concordant/adjacent) or suboptimal (remote). All-cause mortality was recorded at follow-up. RESULTS An optimal LV lead position (n = 202) conferred LV remodeling response superior to that of a suboptimal lead position (change in LV end-systolic volume: -24 ± 15% vs. -12 ± 17% [p < 0.001]; change in ejection fraction: +7 ± 8% vs. +4 ± 7% [p = 0.02]). During long-term follow-up (median: 39 months; range: <1 to 61 months), an optimal LV lead position was associated with improved survival (log-rank p = 0.003). A suboptimal LV lead placement independently predicted all-cause mortality (hazard ratio: 1.8; p = 0.024). CONCLUSIONS An optimal LV lead position at the site of latest mechanical activation, avoiding low strain amplitude (scar), was associated with superior CRT response and improved survival that persisted during follow-up.

Cardiac resynchronization therapy optimization using noninvasive cardiac output measurement.

Aims:  Noninvasive cardiac output (CO) measurement (NICOM) is a novel method to assess ventricular function and offers a potential alternative for optimization of cardiac resynchronization therapy (CRT) devices. We compared the effect of NICOM‐based optimization to no optimization (empiric settings) on CRT outcomes.

Non-invasive cardiac output measurements based on bioreactance for optimization of atrio- and interventricular delays.

AIMS Non-invasive cardiac output monitoring (NICOM) based on bio-reactance offers a portable method to assess ventricular function. Optimization of cardiac resynchronization therapy (CRT) by echocardiography is labour-intensive. We compared the ability of NICOM and echocardiography to facilitate optimum CRT device programming. METHODS AND RESULTS Forty-seven patients in sinus rhythm were evaluated within 14 days of CRT implantation. The atrio- (AV) and interventricular (VV) delay intervals were incrementally adjusted and at each setting, NICOM and echocardiographic data were recorded. Left ventricular (LV) volumes and function were assessed by echocardiography at baseline and 3 months. Response to CRT was defined as a reduction in LV end-systolic volume (LVESV) by >15%. In all patients, cardiac output (CO) increased significantly at optimized settings compared with baseline (5.66 +/- 1.4 vs. 4.35 +/- 1.1 L/min, P < 0.001). A 20% increase in acute CO following CRT predicted LVESV reduction of >15% with a sensitivity of 81% and specificity of 92% (AUC 0.86). The optimum AV delay determined by NICOM was confirmed by echocardiography in 40 of 47 patients (85%, r = 0.89, P < 0.01) and for VV delay in 39 of 47 patients (83%, r = 0.89, P < 0.01). CONCLUSION Non-invasive cardiac output monitoring is a simple, reliable, and portable alternative to echocardiography to program CRT devices.

Cardiac resynchronisation therapy: pacemaker versus internal cardioverter-defibrillator in patients with impaired left ventricular function

Objective Studies have shown beneficial effects of cardiac resynchronisation therapy (CRT) on mortality among patients with heart failure. However the incremental benefits in survival from CRT with a defibrillator (CRT-D) are unclear. The choice of appropriate device remains unanswered. Method This is a single-centre observational study in a tertiary cardiac centre. Patients (n=500) implanted with a CRT device with pacing alone (CRT-P) (n=354) and CRT-D (n=146) were followed for at least 2 years (mean 29 months, SD 14 months). The primary end point was all-cause mortality. Results A total of 116 deaths (23.2%) were recorded: 88 (24.8%) and 28 (19.2%), in the CRT-P and CRT-D groups, respectively. At 1 year there was a trend favouring CRT-D (HR 0.54, 95% CI 0.27 to 1.07, p=0.08) but this was attenuated by the 2nd year and became insignificant at the end of follow-up (HR 0.76, 95% CI 0.50 to 1.170, p=0.21). There was no survival benefit from having an internal cardioverter-defibrillator if patients were deemed non-responders to CRT. 27% of the CRT-P patients with ischaemic cardiomyopathy met indications for potential internal cardioverter-defibrillator implantation for primary prevention. These were older patients with poorer baseline function in comparison with CRT-D patients with devices for primary prevention. Once these differences were adjusted for, there was no difference in outcome between the groups. Conclusions CRT-D did not offer additional survival advantage over CRT-P at longer-term follow-up, as the clinical benefit of a defibrillator attenuated with time. Further work is needed to define which subset of patients benefit from CRT-D.

Cardioverter-defibrillator implantation and generator replacement in the octogenarian

AIMS Increase in life expectancy has led to increased rate of implantable cardioverter-defibrillator (ICD) implantation in patients in their 80s, but there are no current formal recommendations to guide physicians when elderly patients with ICDs require elective unit replacement (EUR). This study aims at assessing survival and rates of ICD therapies in patients who have had ICD implantation or EUR above the age of 80, focusing on the latter. METHODS AND RESULTS Retrospective analysis of a prospectively kept database of all ICD-related procedures carried out in a single tertiary centre. Patients 80 years of age or older submitted to ICD implantation (n = 42) or EUR (n = 34) between November 1991 and May 2012 were included. Using collected baseline and outcome data from this cohort, we assessed survival of these patients and the rates of ICD therapies. Median additional years of life after ICD implantation and ICD EUR in patients who died before data retrieval was 2.5 and 1.2, respectively, and while 65% of deceased patients after ICD implantation died in the first 3 years after the procedure, 50% of deceased post-ICD EUR patients died within the first year. Mortality rates at 1 and 2 years post-EUR were 23.1 and 38.1%, respectively. Furthermore, ventricular tachycardia occurred in a small minority of patients after EUR (16.7%) and no ventricular fibrillation-triggered ICD therapies were reported in both groups. CONCLUSION In octogenarians who are due for an ICD EUR, careful thought should be given to the current clinical status, comorbidities, and general frailty prior to considering them for the procedure. A survival benefit from ICD EUR in this age stratum is not likely.

Radial Strain Delay Based on Segmental Timing and Strain Amplitude Predicts Left Ventricular Reverse Remodeling and Survival After Cardiac Resynchronization Therapy

Background— Dyssynchrony assessment based on the timing of regional contraction is inherently independent of underlying myocardial contractility. We tested the hypothesis that patient selection for cardiac resynchronization therapy (CRT) would be enhanced using a parameter derived from the net radial strain delay (RSD) for the 12 basal and mid–left ventricular segments (calculated radial strain delay RSD [RSDc]), based on not only timing but also amplitude of segmental strain. Methods and Results— Echocardiographic data were analyzed in 240 patients with symptomatic heart failure undergoing CRT (New York Heart Association class III/IV; QRS >120 milliseconds; ejection fraction, 23±7%). RSDc was calculated as the sum of difference between peak radial strain and radial strain at aortic valve closure before CRT implantation. CRT response was defined as >15% reduction in left ventricular end-systolic volume at 6 months. In a derivation group (n=102), RSDc was higher in responders compared with nonresponders (74±39% versus 29±15%; P<0.001) and related to the change in left ventricular end-systolic volume (r=−0.53; P<0.001). RSDc >40% predicted remodeling (sensitivity, 87%; specificity, 88%). In the validation group (n=108), RSDc similarly predicted response (sensitivity, 89%; specificity, 84%). Survival at long-term follow-up was greater in patients with RSDc >40% (P<0.0001). Conclusions— RSDc, based on both the timing and the amplitude of segmental strain, has a strong predictive value for CRT remodeling response and long-term survival.