Impact of cardiac resynchronization therapy using hemodynamically optimized pacing on left ventricular remodeling in patients with congestive heart failure and ventricular conduction disturbances

Robotic-Assisted Left Ventricular Lead Placement

Robot-assisted left ventricular lead implantation for cardiac resynchronization therapy is a feasible and safe technique with superior visualization, dexterity, and precision to target the optimal pacing site. The technique has been associated with clinical response and beneficial reverse remodeling comparable with the conventional approach via the coronary sinus. The lack of clinical superiority and a residual high nonresponder rate suggest that the appropriate clinical role for the technique remains as rescue therapy.

Optimal cut-off value of reverse remodeling to predict long-term outcome after cardiac resynchronization therapy in patients with ischemic cardiomyopathy

BACKGROUND

Whether the optimal cut-off value of left ventricular (LV) reverse remodeling is different in patients with ischemic cardiomyopathy (ICM) vs. non-ischemic cardiomyopathy (NICM) is unclear. This study aimed to clarify this value in patients with ICM and NICM.

METHODS AND RESULTS

LV reverse remodeling was defined as a reduction in LV end-systolic volume (LVESV) at 6 months after cardiac resynchronization therapy (CRT). The clinical endpoint was the combination of cardiac death and first hospitalization for worsening heart failure. Ninety-one of 372 patients had ICM. Event-free survival rates did not differ between ICM and NICM groups (66.8% vs. 78.9%; p=0.12). Receiver operating characteristics analysis revealed a 9% reduction in ESV as the optimal cut-off value to predict the composite endpoint in patients with ICM and a 15% reduction in patients with NICM. Multivariate analysis revealed that reductions in ESV of ≥15% and ≥9% were independent predictors of the composite endpoint, as were left bundle branch block (LBBB) and B-type natriuretic peptide (BNP) at 6 months after CRT. In combination with LBBB and BNP, reduction in ESV ≥9% had a higher, but not significant, C-statistics value than ESV ≥15% (0.854, 95% CI 0.729-0.940 vs. 0.801, 95% CI 0.702-0.908, p=0.07).

CONCLUSION

The optimal cut-off value of a reduction in LVESV was lower in patients with ICM than in patients with NICM.

Perfusion and metabolic scintigraphy with (123)I-BMIPP in prognosis of cardiac resynchronization therapy in patients with dilated cardiomyopathy

OBJECTIVE

The objective of the study was to investigate the left ventricular (LV) myocardial perfusion and metabolism in patients with idiopathic dilated cardiomyopathy (DCM) and to identify the scintigraphic predictors of the efficacy of cardiac resynchronization therapy (CRT).

METHODS

The study comprised 63 patients with DCM and severe heart failure (NYHA class III-IV). Before CRT, all patients received gamma-scintigraphy with (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) and with (123)I-β-methyl-iodophenyl pentadecanoic acid ((123)I-BMIPP) for evaluation of myocardial perfusion and metabolism, respectively. Before and after 6 months of CRT, all patients underwent echocardiography study to assess cardiac hemodynamics.

RESULTS

After 6 months of CRT, patients were divided into two groups: group 1 comprised responders in whom LV end systolic volume (LVESV) decreased by ≥15 % (n = 39); group 2 comprised non-responders in whom LVESV decreased by <15 % (n = 24). Before CRT, LV pumping function did not significantly differ between groups. Significant differences were found in the following preoperative scintigraphic parameters: myocardial perfusion defect size [7.4 % (5.9; 13.2) % and 11.8 (8.8; 16.2) %, p < 0.05] and metabolic defect size [7.4 (4.4; 14.7) % and 8.8 (8.8; 17.6) %, p < 0.05]. Metabolic scintigraphy showed greater diagnostic efficacy in determining the indications for CRT compared with perfusion scintigraphy [areas under the ROC curves (AUC) of 0.722 and 0.612, respectively]. The best metabolic defect size threshold value of 7.35 % predicted CRT efficacy with the sensitivity and specificity rates of 77.8 and 66.7 %, respectively.

CONCLUSION

Data of metabolic scintigraphy may be useful for the integrated prediction of CRT efficacy.

Efficacy of equilibrium radionuclide angiography to predict acute response to cardiac resynchronization therapy in patients with heart failure

OBJECTIVE

To predict the acute response to cardiac resynchronization therapy (CRT) in patients with left ventricular mechanical dyssynchrony using equilibrium radionuclide angiography (ERNA).

PATIENTS AND METHODS

A total of 24 consecutive heart failure patients scheduled for CRT were included. ERNA was performed before and within 48 h after pacemaker implantation to calculate both left ventricular (LV) volumes and LV dyssynchrony. LV dyssynchrony was defined as the standard left ventricular phase shift and left ventricular phase standard deviation (LVPS% and LVPSD%). Patients were subsequently divided into acute responders or nonresponders, based on a reduction of at least 15% in LV end-systolic volume immediately after CRT.

RESULTS

Fifteen patients (63%) were classified as acute responders. Baseline characteristics were similar between responders and nonresponders except for the LVPS% and LVPSD%, which were larger in responders. Moreover, responders demonstrated a significant reduction of LVPS% and LVPSD% immediately after CRT (from 28.00±2.88 to 17.53±4.94 and 11.20±2.54 to 5.60±1.80, P<0.001), whereas in nonresponders LVPS% and LVPSD% remained unchanged (from 21.44±3.91 to 19.56±4.22% and 6.55±1.51 to 6.22±1.30%, P=NS). Receiver operating characteristic curve analysis revealed that a cut-off value of 25% for LVPS%, a sensitivity of 80% with a specificity of 89% were obtained to predict acute ERNA response to CRT (area under the curve=0.93) and a cut-off value of 8.5% for LVPSD%, a sensitivity of 87% with a specificity of 89% were obtained to predict acute ERNA response to CRT (area under the curve=0.95).

CONCLUSION

ERNA is highly predictive for acute response to CRT. ERNA also allows assessment of changes in LV volumes and LV ejection fraction before and after CRT implantation.

The Role of Atrioventricular and Interventricular Optimization for Cardiac Resynchronization Therapy

Many patients with left ventricular systolic dysfunction may benefit from cardiac resynchronization therapy; however, approximately 30% of patients do not experience significant clinical improvement with this treatment. AV and VV delay optimization techniques have included echocardiography, device-based algorithms, and several other novel noninvasive techniques. Using these techniques to optimize device settings has been shown to improve hemodynamic function acutely; however, the long-term clinical benefit is limited. In most cases, an empiric AV delay with simultaneous biventricular or left ventricular pacing is adequate. The value of optimization of these intervals in "nonresponders" still requires further investigation.

Robotic-Assisted Left Ventricular Lead Placement

Robot-assisted left ventricular lead implantation for cardiac resynchronization therapy is a feasible and safe technique with superior visualization, dexterity, and precision to target the optimal pacing site. The technique has been associated with clinical response and beneficial reverse remodeling comparable with the conventional approach via the coronary sinus. The lack of clinical superiority and a residual high nonresponder rate suggest that the appropriate clinical role for the technique remains as rescue therapy.

Left Ventricular Lead Placement Targeted at the Latest Activated Site Guided by Electrophysiological Mapping in Coronary Sinus Branches Improves Response to Cardiac Resynchronization Therapy

INTRODUCTION

Electrophysiological mapping (EPM) in coronary sinus (CS) branches is feasible for guiding LV lead placement to the optimal, latest activated site at cardiac resynchronization therapy (CRT) procedures. However, whether this procedure optimizes the response to CRT has not been demonstrated. This study was to evaluate effects of targeting LV lead at the latest activated site guided by EPM during CRT.

METHODS

Seventy-six consecutive patients with advanced heart failure who were referred for CRT were divided into mapping (MG) and control groups (CG). In MG, the LV lead, also used as a mapping bipolar electrode, was placed at the latest activated site determined by EPM in CS branches. In CG, conventional CRT procedure was performed. Patients were followed for 6 months after CRT.

RESULTS

Baseline characteristics were comparable between the 2 groups. In MG (n = 29), EPM was successfully performed in 85 of 91 CS branches during CRT. A LV lead was successfully placed at the latest activated site guided by EPM in 27 (93.1%) patients. Compared with CG (n = 47), MG had a significantly higher rate (86.2% vs. 63.8%, P = 0.039) of response (>15% reduction in LV end-systolic volume) to CRT, a higher percentage of patients with clinical improvement of ≥2 NYHA functional classes (72.4% vs. 44.7%, P = 0.032), and a shorter QRS duration (P = 0.004).

CONCLUSIONS

LV lead placed at the latest activated site guided by EPM resulted in a significantly greater CRT response, and a shorter QRS duration.

ICD and CRT use in ischemic heart disease in women

Although the role of implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy (CRT) in improving outcomes in ischemic cardiomyopathy (ICM) has been described, the data regarding gender-based survival outcomes are limited. There is a higher preponderance of non-ischemic cardiomyopathy (NICM) in women, and most of the ICM literature is derived from sub-study analysis. This review summarizes the current body of literature on prognosis, pathophysiology, and the present clinical practice for device implantation in women with ICM.

Effects of tricuspid valve regurgitation on outcome in patients with cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) has a symptomatic and survival benefit for patients with heart failure (HF), but the percentage of nonresponders remains relatively high. The aims of this study were to assess the clinical significance of baseline tricuspid regurgitation (TR) or worsening TR after implantation of a CRT device on the response to therapy. This is a multicenter retrospective analysis of prospectively collected databases that includes 689 consecutive patients who underwent implantation of CRT. The patients were divided into groups according to baseline TR grade and according to worsening TR within 15 months after device implantation. Outcome was assessed by clinical and echocardiographic response within 15 months and by estimated survival for a median interquartile range follow-up time of 3.3 years (1.6, 4.6). TR worsening after CRT implantation was documented in 104 patients (15%). These patients had worse clinical and echocardiographic response to CRT, but worsening of TR was not a significant predictor of mortality (p = 0.17). According to baseline echocardiogram, 620 patients (90%) had some degree of TR before CRT implant. Baseline TR was an independent predictor of worse survival (p <0.001), although these patients had significantly better clinical and echocardiographic response compared with patients without TR. In conclusion, worsening of TR after CRT implantation is a predictor of worse clinical and echocardiographic response but was not significantly associated with increased mortality. Baseline TR is associated with reduced survival despite better clinical and echocardiographic response after CRT implantation.

Strategies to improve cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) emerged 2 decades ago as a useful form of device therapy for heart failure associated with abnormal ventricular conduction, indicated by a wide QRS complex. In this Review, we present insights into how to achieve the greatest benefits with this pacemaker therapy. Outcomes from CRT can be improved by appropriate patient selection, careful positioning of right and left ventricular pacing electrodes, and optimal timing of electrode stimulation. Left bundle branch block (LBBB), which can be detected on an electrocardiogram, is the predominant substrate for CRT, and patients with this conduction abnormality yield the most benefit. However, other features, such as QRS morphology, mechanical dyssynchrony, myocardial scarring, and the aetiology of heart failure, might also determine the benefit of CRT. No single left ventricular pacing site suits all patients, but a late-activated site, during either the intrinsic LBBB rhythm or right ventricular pacing, should be selected. Positioning the lead inside a scarred region substantially impairs outcomes. Optimization of stimulation intervals improves cardiac pump function in the short term, but CRT procedures must become easier and more reliable, perhaps with the use of electrocardiographic measures, to improve long-term outcomes.

British randomised controlled trial of AV and VV optimization ("BRAVO") study: rationale, design, and endpoints

Background

Echocardiographic optimization of pacemaker settings is the current standard of care for patients treated with cardiac resynchronization therapy. However, the process requires considerable time of expert staff. The BRAVO study is a non-inferiority trial comparing echocardiographic optimization of atrioventricular (AV) and interventricular (VV) delay with an alternative method using non-invasive blood pressure monitoring that can be automated to consume less staff resources.

Methods/Design

BRAVO is a multi-centre, randomized, cross-over, non-inferiority trial of 400 patients with a previously implanted cardiac resynchronization device. Patients are randomly allocated to six months in each arm. In the echocardiographic arm, AV delay is optimized using the iterative method and VV delay by maximizing LVOT VTI. In the haemodynamic arm AV and VV delay are optimized using non-invasive blood pressure measured using finger photoplethysmography. At the end of each six month arm, patients undergo the primary outcome measure of objective exercise capacity, quantified as peak oxygen uptake (VO₂) on a cardiopulmonary exercise test. Secondary outcome measures are echocardiographic measurement of left ventricular remodelling, quality of life score and N-terminal pro B-type Natriuretic Peptide (NT-pro BNP). The study is scheduled to complete recruitment in December 2013 and to complete follow up in December 2014.

Discussion

If exercise capacity is non-inferior with haemodynamic optimization compared with echocardiographic optimization, it would be proof of concept that haemodynamic optimization is an acceptable alternative which has the potential to be more easily implemented.

Trial registration

Clinicaltrials.gov NCT01258829

Predictors and outcomes of "super-response" to cardiac resynchronization therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) has been shown to improve heart failure (HF) symptoms and survival. We hypothesized that a greater improvement in left-ventricular ejection fraction (LVEF) after CRT is associated with greater survival benefit.

METHODS AND RESULTS

In 693 patients across 2 international centers, the improvement in LVEF after CRT was determined. Patients were grouped as non-/modest-, moderate-, or super-responders to CRT, defined as an absolute change in LVEF of ≤5%, 6-15%, and >15%, respectively. Changes in New York Heart Association (NYHA) functional class and left ventricular end-diastolic dimension (LVEDD) were assessed for each group. There were 395 non-/modest-, 186 moderate-, and 112 super-responders. Super-responders were more likely to be female and to have nonischemic cardiomyopathy, lower creatinine, and lower pulmonary artery systolic pressure than non-/modest- and moderate-responders. Super-responders were also more likely to have lower LVEF than non-/modest-responders. There was no difference in NYHA functional class, mitral regurgitation grade, or tricuspid regurgitation grade between groups. Improvement in NYHA functional class (-0.9 ± 0.9 vs -0.4 ± 0.8 [P < .001] and -0.6 ± 0.8 [P = .02]) and LVEDD (-8.7 ± 9.9 mm vs -0.5 ± 5.0 and -2.4 ± 5.8 mm [P < .001 for both]) was greatest in super-responders. Kaplan-Meier survival analysis revealed that super-responders achieved better survival compared with non-/modest- (P < .001) and moderate-responders (P = .049).

CONCLUSIONS

Improvement in HF symptoms and survival after CRT is proportionate to the degree of improvement in LV systolic function. Super-response is more likely in women, those with nonischemic substrate, and those with lower pulmonary artery systolic pressure.

Indications for cardiac resynchronization therapy

Initial studies established patient selection criteria for cardiac resynchronization therapy (CRT) as left ventricular ejection fraction less than or equal to 35%, QRS greater than or equal to 120 ms, and New York Heart Association 3-4. Based on newer data, post hoc analyses, and meta-analyses, these criteria have been refined and guidelines updated, highlighting left bundle branch morphology and QRS greater than 150 ms in selecting patients with a likelihood of favorable outcomes. Guidelines will change as more data become available; the decision to apply CRT should be based on patient clinical profile and the balance of risk tolerance and likelihood of benefit.

Myocardial recovery and the failing heart: medical, device and mechanical methods

BACKGROUND

Cardiac remodeling describes the molecular, cellular, and interstitial changes that cause the ventricle to develop pathologic geometry as heart failure progresses. Reverse remodeling, or the healing of a failing heart, leads to improved mortality and quality of life.

FINDINGS

Therapies that lead to reverse remodeling include medications such as β-blockers and angiotensin-converting enzyme inhibitors; cardiac resynchronization therapy with biventricular pacing; and mechanical support with left ventricular assist devices.

CONCLUSIONS

Further study is needed to better predict which patients will benefit most from these therapies and will then go on to experience reverse remodeling and myocardial recovery.

Remote past left ventricular function before chronic right ventricular pacing predicts responses to cardiac resynchronization therapy upgrade

BACKGROUND

This study examined factors that could predict response to cardiac resynchronization therapy (CRT) upgrade in patients who developed heart failure (HF) after long-term right ventricular (RV) pacing.

METHODS

Twenty-five consecutive patients who received CRT upgrade for long-term RV pacing (RVP) were enrolled in this study. None of these patients were eligible for CRT at the moment of starting RVP. After 5.7 ± 4.0 years chronic RVP, these 25 patients developed HF symptoms and received CRT upgrade. Echocardiography was conducted at the moment of CRT upgrade and 6 months after CRT. Remote past left ventricular ejection fraction (RP-LVEF) at the moment of starting RVP was retrospectively obtained from the echocardiographic and cardiac catherization reports. Responders were defined as a reduction in LV end-systolic volume (LVESV) ≥ 15%. Their clinical and echocardiographic parameters were analyzed and compared.

RESULTS

Responders had significant higher RP-LVEF as compared to nonresponders (53.6 ± 16.5% vs 31.4 ± 11.6%, P = 0.002). RP-LVEF correlated with reduction in LVESV after CRT upgrade (P < 0.001). RP-LVEF ≥ 43.5% as a cutoff value predicted response to CRT upgrade with an area under the receiver-operating curve of 0.87, a sensitivity of 78%, and a specificity of 100%. Intrinsic QRS width, septal-posterior wall motion delay, or tissue Doppler-derived dyssynchrony indexes did not predict responses to CRT upgrade.

CONCLUSION

In long-term RVP patients who developed HF and received CRT upgrade, RP-LVEF ≥ 43.5% predicts good response. Conventional dyssynchrony indexes do not predict responses to CRT upgrade in these patients.

Short-term reduction in intrinsic heart rate during biventricular pacing after cardiac surgery: a substudy of a randomized clinical trial

BACKGROUND

The Biventricular Pacing After Cardiac Surgery trial investigates hemodynamics of temporary pacing in selected patients at risk of left ventricular dysfunction. This trial demonstrates improved hemodynamics during optimized biventricular pacing compared with atrial pacing at the same heart rate 1 and 2 hours after bypass and reduced vasoactive-inotropic score over the first 4 hours after bypass. However, this advantage of biventricular versus atrial pacing disappears 12 to 24 hours later. We hypothesized that changes in intrinsic heart rate can explain variable effects of atrial pacing in this setting.

METHODS

Heart rate, mean arterial pressure, cardiac output, and medications depressing heart rate were analyzed in patients randomized to continuous biventricular pacing (n = 16) or standard of care (n = 18).

RESULTS

During 30-second testing periods without pacing, intrinsic heart rate was lower in the paced group 12 to 24 hours after bypass (76.5 ± 17.5 vs 91.7 ± 13.0 beats per minute; P = .040) but not 1 or 2 hours after bypass. Cardiac output (4.4 ± 1.2 vs 3.6 ± 1.9 L/min; P = .054) and stroke volume (53 ± 2 vs 42 ± 2 mL; P = .051) increased overnight in the paced group. Vasoactive medication doses were not different between groups, whereas dexmedetomidine administration was prolonged over postoperative hours 12 to 24 in the paced group (793 ± 528 vs 478 ± 295 minutes; P = .013).

CONCLUSIONS

These observations suggest that hemodynamic benefits of biventricular pacing 12 to 24 hours after cardiopulmonary bypass lead to withdrawal of sympathetic drive and decreased intrinsic heart rate. Depression of intrinsic rate increases the apparent benefit of atrial pacing in the chronically paced group but not in the control group. Additional study is needed to define clinical benefits of these effects.

Gender-related safety and efficacy of cardiac resynchronization therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) is an established therapy for patients with chronic heart failure (CHF) and a broad QRS complex. Gender-related safety and efficacy data are necessary for informed patient decision-making for female patients with CHF. The aim of the study was to assess the effects of gender on the outcome of CRT in highly symptomatic heart failure patients.

HYPOTHESIS

Gender may have an effect on the outcome of heart failure patients undergoing cardiac resynchronisation therapy.

METHODS

The study analyzed the 2-year follow-up of 393 New York Heart Association (NYHA) class III/IV patients with a class I CRT indication enrolled in the Management of Atrial Fibrillation Suppression in AF-HF Comorbidity Therapy (MASCOT) study.

RESULTS

In female patients (n = 82), compared with male patients (n = 311), CHF was more often due to dilated cardiomyopathy (74% vs 44%, respectively; P < 0.0001). Females also had a more impaired quality-of-life score and a smaller left ventricular end-diastolic diameter (LVEDD). Women were less likely than men to have received a CRT defibrillator (35% vs 61%, respectively; P < 0.0001). After 2 years, the devices had delivered more biventricular pacing in women than in men (96% ± 13% vs 94% ± 13%, respectively; P < 0.0004). Women had a greater reduction in LVEDD than did men (-8.2 mm ± 11.1 mm vs -1.1 mm ± 22.1 mm, respectively; P < 0.02). Both genders improved similarly in NYHA functional class. Women reported greater improvement than men in quality-of-life score (-21.1 ± 26.5 vs -16.2 ± 22.1, respectively; P < 0.0001). After adjustment for cardiovascular history, women had lower all-cause mortality (P = 0.0007), less cardiac death (P = 0.04), and fewer hospitalizations for worsening heart failure (P = 0.01).

CONCLUSIONS

Females exhibited a better response to CRT than did males. Because females have such impressive benefits from CRT, improved screening and advocacy for CRT implantation in women should be considered.

Sex-Based Differences in Cardiac Arrhythmias, ICD Utilisation and Cardiac Resynchronisation Therapy

Many important differences in the presentation and clinical course of cardiac arrhythmias are present between men and women that should be accounted for in clinical practice. In this paper, we review published data on gender differences in cardiac excitable properties, supraventricular tachycardias, ventricular tachycardias, sudden cardiac death, and the utilisation of implantable defibrillators and cardiac resynchronisation therapy. Women have a higher heart rate at rest, and a longer QT interval than men. They further have a narrower QRS complex and lower QRS voltages on the 12-lead ECG with more often non-specific repolarisation abnormalities at rest. Supraventricular tachycardias, such as AV nodal reentrant tachycardia, are twice as frequent in women compared with men. Atrial fibrillation, however, has a 1.5-fold higher prevalence in men. The triggers for idiopathic right ventricular outflow tract tachycardia (VT) initiation are gender specific, i.e. hormonal changes play an important role in the occurrence of these VTs in women. There are clear-cut gender differences in acquired and congenital LQTS. Brugada syndrome affects men more commonly and severely than women. Sudden cardiac death is less prevalent in women at all ages and occurs 10 years later in women than in men. This may be related to the later onset of clinically manifest coronary heart disease in women. Among patients who receive ICDs and CRT devices, women appear to be under-represented, while they may benefit even more from these novel therapies.

Cardiac resynchronisation therapy: a randomised trial of factory or echocardiographic settings for optimum response

BACKGROUND

We aimed to assess whether echocardiographically-optimised atrioventricular (AV) and interventricular (VV) delay programming provided any additional benefit over standard settings following biventricular pacemaker implantation in patients with advanced heart failure.

METHODS

Paired data were collected on 22 patients (aged 67.5 ± 8.3 years, 16 male) with refractory heart failure, NYHA class III/IV symptoms, sinus rhythm, LBBB and a broad QRS complex >120 ms. All patients underwent implantation of a biventricular pacemaker and were randomised to eight weeks of factory pacing mode (Mode 1) or echocardiographically-guided pacing mode (Mode 2), followed by eight weeks in the alternate mode, in a randomised blinded crossover design.

RESULTS

Peak oxygen consumption, 6 min walk distance, NYHA class and quality of life scores improved after biventricular pacing, but no significant difference was found between the two modes, with the exception of peak oxygen consumption score (baseline: 14.8 ± 0.9, Mode 1: 14.6 ± 1.2, Mode 2: 16.1 ± 1.2 mL/kg/min), which was better in Mode 2 than Mode 1 (p 0.003).

CONCLUSION

Transthoracic echocardiographic optimisation of AV and VV delays following biventricular pacing may offer additional clinical benefit in an unselected group of patients when compared with factory settings.

Prediction of long-term outcome of cardiac resynchronization therapy by acute pressure-volume loop measurements

AIMS

Invasive assessment of acute haemodynamic response to biventricular pacing has been proposed as a tool to determine individual response and to optimize the effects of CRT. However, the long-term results of this approach have been poorly studied. The present study relates acute haemodynamic effects of CRT to long-term outcome.

METHODS AND RESULTS

Forty-one patients were analysed in the present study. During temporary biventricular pacing before implantation, acute changes in LV pump function were assessed by pressure-volume loop measurements and related to long-term response after CRT. In the study population [30 (71%) men, NYHA class 2.9 ± 0.4, EF 28 ± 7%, QRS 150 ± 25 ms], baseline mean stroke work (SW) and dP/dt(max) were 4.6 ± 2.6 L × mmHg and 874 ± 259 mmHg/s, respectively. During biventricular pacing, mean SW and dP/dt(max) increased significantly by 43 ± 39% (+ 2.2 ± 2.4 L × mmHg, P < 0.001) and 13 ± 18% (+ 96 ± 136 mmHg/s, P < 0.001), respectively. In long-term responders (n = 29, 71%) compared with non-responders (n = 12, 29%), the acute increase in SW was significantly higher (+57 ± 33% vs. + 10 ± 30%, P < 0.001), whereas the acute increase in dP/dt(max) was not significantly different between responders and non-responders (+ 15 ± 18% vs. 6 ± 15%, P = 0.139). Receiver operating characteristic (ROC) curve analysis indicated that SW was superior to dP/dt(max), QRS duration and LV dyssynchrony in prediction of response to CRT. A cut-off value for SW of 20% yielded a sensitivity of 90% and specificity of 75% to predict reverse remodelling at 6 months.

CONCLUSION

Invasive assessment of acute haemodynamics is a reliable tool to determine individual response to CRT. An acute increase in SW predicts long-term response to CRT with a higher accuracy than an acute increase in dP/dt(max), baseline QRS duration, and degree of LV mechanical dyssynchrony.

John Sutton M, Daubert JC. Effect of QRS Duration and Morphology on Cardiac Resynchronization Therapy Outcomes in Mild Heart Failure

Background—

Cardiac resynchronization therapy (CRT) decreases mortality, improves functional status, and induces reverse left ventricular remodeling in selected populations with heart failure. We aimed to assess the impact of baseline QRS duration and morphology and the change in QRS duration with pacing on CRT outcomes in mild heart failure.

Methods and Results—

Resynchronization Reverses Remodeling in Systolic Left Ventricular Dysfunction (REVERSE) was a multicenter randomized trial of CRT among 610 patients with mild heart failure. Baseline and CRT-paced QRS durations and baseline QRS morphology were evaluated by blinded core laboratories. The mean baseline QRS duration was 151±23 milliseconds, and 60.5% of subjects had left bundle-branch block (LBBB). Patients with LBBB experienced a 25.3-mL/m 2 mean reduction in left ventricular end-systolic volume index ( P <0.0001), whereas non-LBBB patients had smaller decreases (6.7 mL/m 2 ; P =0.18). Baseline QRS duration was also a strong predictor of change in left ventricular end-systolic volume index with monotonic increases as QRS duration prolonged. Similarly, the clinical composite score improved with CRT for LBBB subjects (odds ratio, 0.530; P =0.0034) but not for non-LBBB subjects (odds ratio, 0.724; P =0.21). The association between clinical composite score and QRS duration was highly significant (odds ratio, 0.831 for each 10-millisecond increase in QRS duration; P <0.0001), with improved response at longer QRS durations. The change in QRS duration with CRT pacing was not an independent predictor of any outcomes after correction for baseline variables.

Conclusion—

REVERSE demonstrated that LBBB and QRS prolongation are markers of reverse remodeling and clinical benefit with CRT in mild heart failure.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00271154.

Global and regional ventricular repolarization study by body surface potential mapping in patients with left bundle-branch block and heart failure undergoing cardiac resynchronization therapy

BACKGROUND

The controversial effects promoted by cardiac resynchronization therapy (CRT) on the ventricular repolarization (VR) have motivated VR evaluation by body surface potential mapping (BSPM) in CRT patients.

METHODS

Fifty-two CRT patients, mean age 58.8 ± 12.3 years, 31 male, LVEF 27.5 ± 9.2, NYHA III-IV heart failure with QRS181.5 ± 14.2 ms, underwent 87-lead BSPM in sinus rhythm (BASELINE) and biventricular pacing (BIV). Measurements of mean and corrected QT intervals and dispersion, mean and corrected T peak end intervals and their dispersion, and JT intervals characterized global and regional (RV, Intermediate, and LV regions) ventricular repolarization response.

RESULTS

Global QTm (P < 0.001) and QTc(m) (P < 0.05) were decreased in BIV; QTm was similar across regions in both modes (P = ns); QTc(m) values were lower in RV/LV than in Intermediate region in BASELINE and BIV (P < 0.001); only RV/Septum showed a significant difference (P < 0.01) in the BIV mode. QTD values both of BASELINE (P < 0.01) and BIV (P < 0.001) were greater in the Intermediate than in the LV region. CRT effect significantly reduced global/regional QTm and QTc(m) values. QTD was globally decreased in RV/LV (Intermediate: P = ns). BIV mode significantly reduced global T peak end mean and corrected intervals and their dispersion. JT values were not significant.

CONCLUSIONS

Ventricular repolarization parameters QTm, QTc(m), and QTD global/regional values, as assessed by BSPM, were reduced in patients under CRT with severe HF and LBBB. Greater recovery impairment in the Intermediate region was detected by the smaller variation of its dispersion.

Cardiac resynchronization therapy modulation of exercise left ventricular function and pulmonary O₂ uptake in heart failure

To better understand the mechanisms contributing to improved exercise capacity with cardiac resynchronization therapy (CRT), we studied the effects of 6 mo of CRT on pulmonary O(2) uptake (Vo(2)) kinetics, exercise left ventricular (LV) function, and peak Vo(2) in 12 subjects (age: 56 ± 15 yr, peak Vo(2): 12.9 ± 3.2 ml·kg(-1)·min(-1), ejection fraction: 18 ± 3%) with heart failure. We hypothesized that CRT would speed Vo(2) kinetics due to an increase in stroke volume secondary to a reduction in LV end-systolic volume (ESV) and that the increase in peak Vo(2) would be related to an increase in cardiac output reserve. We found that Vo(2) kinetics were faster during the transition to moderate-intensity exercise after CRT (pre-CRT: 69 ± 21 s vs. post-CRT: 54 ± 17 s, P < 0.05). During moderate-intensity exercise, LV ESV reserve (exercise - resting) increased 9 ± 7 ml (vs. a 3 ± 9-ml decrease pre-CRT, P < 0.05), and steady-state stroke volume increased (pre-CRT: 42 ± 8 ml vs. post-CRT: 61 ± 12 ml, P < 0.05). LV end-diastolic volume did not change from rest to steady-state exercise post-CRT (P > 0.05). CRT improved heart rate, measured as a lower resting and steady-state exercise heart rate and as faster heart rate kinetics after CRT (pre-CRT: 89 ± 12 s vs. post-CRT: 69 ± 21 s, P < 0.05). For peak exercise, cardiac output reserve increased significantly post-CRT and was 22% higher at peak exercise post-CRT (both P < 0.05). The increase in cardiac output was due to both a significant increase in peak and reserve stroke volume and to a nonsignificant increase in heart rate reserve. Similar patterns in LV volumes as moderate-intensity exercise were observed at peak exercise. Cardiac output reserve was related to peak Vo(2) (r = 0.48, P < 0.05). These findings demonstrate the chronic CRT-mediated cardiac factors that contribute, in part, to the speeding in Vo(2) kinetics and increase in peak Vo(2) in clinically stable heart failure patients.

The acute effects of changes to AV delay on BP and stroke volume: potential implications for design of pacemaker optimization protocols

BACKGROUND

The AV delay optimization of biventricular pacemakers (cardiac resynchronization therapy) may maximize hemodynamic benefit but consumes specialist time to conduct echocardiographically. Noninvasive BP monitoring is a potentially automatable alternative, but it is unknown whether it gives the same information and similar precision (signal/noise ratio). Moreover, the immediate BP increment on optimization has been reported to decay away: it is unclear whether this is the result of an (undesirable) decrease in stroke volume or a (desirable) compensatory relief of peripheral vasoconstriction.

METHODS AND RESULTS

To discriminate between these alternative mechanisms, we measured simultaneous beat-to-beat stroke volume (flow) using Doppler echocardiography, and BP using finger photoplethysmography, during and after AV delay changes from 40 to 120 ms in 19 subjects with cardiac pacemakers. BP and stroke volume both increased immediately (P<0.001, within 1 heartbeat). BP showed a clear decline a few seconds later (average rate, -0.65 mm Hg/beat; r=0.95 [95% CI, 0.86-0.98]); in contrast, stroke volume did not decline (P=0.87). The immediate BP increment correlated strongly with the stroke volume increment (r=0.74, P<0.001). The signal/noise ratio was 3-fold better for BP than stroke volume (6.8±3.5 versus 2.3±1.4; P<0.001).

CONCLUSIONS

Improving AV delay immediately increases BP, but the effect begins to decay within a few seconds. Reassuringly, this is because of compensatory vasodilatation rather than reduction in cardiac function. Pacemaker optimization will never be reliable unless there is an adequate signal/noise ratio. Using BP rather than Doppler minimizes noise. The early phase (before vascular compensation) has the richest signal lode.

The "missing" link between acute hemodynamic effect and clinical response

The hemodynamic, mechanical and electrical effects of cardiac resynchronization therapy (CRT) occur immediate and are lasting as long as CRT is delivered. Therefore, it is reasonable to assume that acute hemodynamic effects should predict long-term outcome. However, in the literature there is more evidence against than in favour of this idea. This raises the question of what factor(s) do relate to the benefit of CRT. There is increasing evidence that dyssynchrony, presumably through the resultant abnormal local mechanical behaviour, induces extensive remodelling, comprising structure, as well as electrophysiological and contractile processes. Resynchronization has been shown to reverse these processes, even in cases of limited hemodynamic improvement. These data may indicate the need for a paradigm shift in order to achieve maximal long-term CRT response.

Impact of preoperative anterior leaflet tethering on the recurrence of ischemic mitral regurgitation and the lack of left ventricular reverse remodeling after restrictive annuloplasty

BACKGROUND

The aim of this multicenter study was to investigate the impact of the preoperative anterior mitral leaflet tethering angle, α', on the recurrence of mitral regurgitation (MR) and left ventricular (LV) reverse remodeling (LVRR) after undersized mitral ring annuloplasty.

METHODS

The study population consisted of 362 patients, who were divided into two groups by baseline α': group 1, α' < 39.5° (n = 196), and group 2, α' ≥ 39.5° (n = 166). End points were recurrent MR ≥ 2+; LVRR, defined as a reduction in end-systolic volume index > 15%; and LV geometric reverse remodeling, defined as a reduction in systolic sphericity index to a normal value of <0.72 in patients with altered baseline geometry.

RESULTS

MR occurred in 9.6% (n = 19) and 43.3% (n = 72) of the patients in groups 1 and 2, respectively (P < .001). LVRR (85.7% vs 22.2%) at follow-up was higher in group 1 (P < .001). On multivariate regression analysis, α' ≥ 39.5° was a strong predictor of MR recurrence, lack of LV reverse remodeling and lack of LV geometric reverse remodeling (all P values < .001). In contrast, the posterior mitral leaflet tethering angle, β', was not significant (all P values > .05). When we allowed for interactions between α' and other risk factors, this effect occurred also in low-risk subgroups, and it was equivalent or generally attenuated in higher risk patients. There were no significant interactions between α' and any of the covariates (all P values > .05).

CONCLUSIONS

Anterior mitral leaflet tethering is a powerful predictor of MR recurrence and lack of LVRR after undersized mitral ring annuloplasty. Evaluation of leaflet tethering should be incorporated into clinical risk assessment and prediction models.