Determinants of Mortality in Patients Undergoing Cardiac Resynchronization Therapy: Baseline Clinical, Echocardiographic, and Angioscintigraphic Evaluation Prior to Resynchronization

Long-term independent predictors of positive response to cardiac resynchronization therapy

AIMS

Cardiac resynchronization therapy (CRT) is currently considered an important breakthrough in the treatment of selected patients with refractory heart failure. However, long-term predictors of mortality, morbidity and time to recovery of ventricular function for those patients who respond positively to CRT remain poorly investigated.

METHODS

This is a retrospective follow-up study involving one hospital. Between August 2004 and October 2008, 211 consecutive patients with refractory heart failure received a CRT device in the Cardiology Division of Ospedale Civile Maggiore in Verona. The clinical characteristics studied were age, sex, heart rhythm, left ventricular end-systolic volume/body surface area (LVESV/BSA), left ventricular ejection fraction, QRS duration, type of bundle-branch block, cause, New York Heart Failure Association functional class, pharmacological therapy and lead position. The objective of this study was to evaluate the effect of several baseline characteristics on long-term prognosis in heart failure patients treated with CRT.

RESULTS

Nonischemic cause, left bundle-branch block and a basal LVESV/BSA of 106 ml/m or less were the only independent predictors of a positive response to CRT (P < 0.005). Additionally, a reduction in LVESV/BSA after CRT was associated both with increased survival and reduced rehospitalization for heart failure (P < 0.005).

CONCLUSION

A better selection of patients on the basis of cause, type of bundle-branch block and basal LVESV/BSA can increase the number of patients that would benefit from CRT.

Heart failure patients selection for cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is an established treatment for refractory chronic heart failure (CHF) patients with ventricular dyssynchrony. The patient selection for this therapy remains the basis for response improvement. Various parameters, methods and technology for identification of appropriate patient are under research. The influences of age and gender, disease progress stage such as mild and late stage CHF including right ventricular dysfunction, dyssynchrony and scar identified by imaging techniques like echocardiography, magnetic resonance and nuclear imaging, and atrial fibrillation on CRT benefits were respectively discussed. This review summarizes the current advancement in these areas.

Beta-blocker utilization and outcomes in patients receiving cardiac resynchronization therapy

INTRODUCTION

Optimal pharmacologic therapy (OPT) is considered a prerequisite to consideration for cardiac resynchronization therapy (CRT).

HYPOTHESIS

Medications such as beta-blockers (BB) with demonstrated benefit in heart failure (HF) are being under utilized in patients receiving CRT.

METHODS

Consecutive patients receiving a CRT-capable defibrillator in 2004 at a tertiary care center for standard indications were studied. Clinical data and medications upon hospital discharge were recorded. Patients were followed for endpoints of death or transplantation.

RESULTS

Of 177 patients receiving a CRT device, 129 (73%) received BB therapy (group 1). Of the 48 patients not on BBs (group 2), relative contraindications were documented in 21 (allergy in 3, hypotension or inotrope-dependent HF in 4, chronic obstructive pulmonary disease [COPD] in 6, and amiodarone therapy in 8). The remaining 27 patients (group 3) did not receive BB therapy despite absence of documented justification. Compared to group 1, group 3 patients were similar in terms of clinical characteristics and angiotensin-converting enzyme inhibitor (ACEI) use, but were less likely to be on statin therapy. Patients were followed for a mean of 19.9 +/- 9.2 mo. After adjusting for age, QRS duration, creatinine, left ventricular ejection fraction (LVEF), statin use, and presence of ischemic HF etiology, patients not receiving BB therapy in the absence of contraindication had increased risk of death or transplantation (odds ratio [OR]: 3.1, p = 0.043).

CONCLUSIONS

Absence of BB therapy appears to be independently associated with poor outcome in CRT recipients. These results suggest that a crucial component of OPT may be underutilized in a population of HF patients receiving CRT.

What is treatment success in cardiac resynchronization therapy?

Cardiac resynchronization therapy (CRT) is an established treatment for symptomatic patients with heart failure, a prolonged QRS duration, and impaired left ventricular (LV) function. Identification of ‘responders’ and ‘non-responders’ to CRT has attracted considerable attention. The response to CRT can be measured in terms of symptomatic response or clinical outcome, or both. Alternatively, the response to CRT can be measured in terms of changes in surrogate measures of outcome, such as LV volumes, LV ejection fraction, invasive measures of cardiac performance, peak oxygen uptake, and neurohormones. This review explores whether these measures can be used in assessing the symptomatic and prognostic response to CRT. The role of these parameters to the management of individual patients is also discussed.

Optimization and validation of radionuclide angiography phase analysis parameters for quantification of mechanical dyssynchrony

INTRODUCTION

Cardiac resynchronization therapy (CRT) has the potential to improve the outcome of patients suffering from mechanical dyssynchrony and heart failure. It has been suggested that accurate quantification of baseline extent of mechanical dyssynchrony may lead to pre-selection of patients likely to respond to CRT. The standard deviation from a phase histogram (phaseSD), synchrony (S) and entropy (E) are parameters obtained from phase analysis of planar radionuclide angiography (RNA) that may provide an accurate means of assessing mechanical dyssynchrony. In this paper, the ability of phaseSD, S, and E to detect mechanical dyssynchrony was investigated and optimal values for image smoothing, histogram noise thresholding, and bin size were defined. Finally, the intra- and inter-observer reproducibility of the methodology was assessed.

METHODS

PhaseSD, S, and E were calculated for 37 normal subjects (LVEF > 50%, end-diastolic volume < 120 mL, end-systolic volume < 60 mL, QRS < 120 ms, and normal wall motion) and 53 patients with mechanical dyssynchrony (LVEF < 30%, QRS > 120 ms, and typical LBBB). Receiver-operator characteristics (ROC) curves were created and the area under the curve (AUC), for each parameter, was determined using three different imaging filters (no filter and an order 5 Hann filter with cut-off of 5/50 and 10/50). The AUC was also determined using histogram threshold values varying between 0% and 50% (of the max amplitude value). Finally, AUC for E was determined for bins sizes varying between 1 degrees and 20 degrees . Inter- and intra-observer variability was calculated at optimal imaging values.

RESULTS

No smoothing was found to maximize the AUC. The AUC was independent of histogram threshold value. However, a value of 20% provided optimal visualization of the phase image. The AUC was also independent of bin size. At the optimal imaging values, the sensitivity and specificity for all parameters for detection of mechanical dyssynchrony was measured to be 89-100%. Inter- and intra-observer correlation coefficients >0.99 were found for phaseSD, S and E.

CONCLUSIONS

Optimized planar RNA phase analysis parameters, phaseSD, S, and E, were able to detect mechanical dyssynchrony with low inter- and intra-observer variability. Studies assessing the ability of these parameters to predict CRT outcome are required.

Characteristics of heart failure patients associated with good and poor response to cardiac resynchronization therapy: a PROSPECT (Predictors of Response to CRT) sub-analysis

AIMS

Predictors of Response to Cardiac Resynchronization Therapy (CRT) (PROSPECT) was the first large-scale, multicentre clinical trial that evaluated the ability of several echocardiographic measures of mechanical dyssynchrony to predict response to CRT. Since response to CRT may be defined as a spectrum and likely influenced by many factors, this sub-analysis aimed to investigate the relationship between baseline characteristics and measures of response to CRT.

METHODS AND RESULTS

A total of 286 patients were grouped according to relative reduction in left ventricular end-systolic volume (LVESV) after 6 months of CRT: super-responders (reduction in LVESV > or =30%), responders (reduction in LVESV 15-29%), non-responders (reduction in LVESV 0-14%), and negative responders (increase in LVESV). In addition, three subgroups were formed according to clinical and/or echocardiographic response: +/+ responders (clinical improvement and a reduction in LVESV > or =15%), +/- responders (clinical improvement or a reduction in LVESV > or =15%), and -/- responders (no clinical improvement and no reduction in LVESV > or =15%). Differences in clinical and echocardiographic baseline characteristics between these subgroups were analysed. Super-responders were more frequently females, had non-ischaemic heart failure (HF), and had a wider QRS complex and more extensive mechanical dyssynchrony at baseline. Conversely, negative responders were more frequently in New York Heart Association class IV and had a history of ventricular tachycardia (VT). Combined positive responders after CRT (+/+ responders) had more non-ischaemic aetiology, more extensive mechanical dyssynchrony at baseline, and no history of VT.

CONCLUSION

Sub-analysis of data from PROSPECT showed that gender, aetiology of HF, QRS duration, severity of HF, a history of VT, and the presence of baseline mechanical dyssynchrony influence clinical and/or LV reverse remodelling after CRT. Although integration of information about these characteristics would improve patient selection and counselling for CRT, further randomized controlled trials are necessary prior to changing the current guidelines regarding patient selection for CRT.

Association of electrostimulation with cell transplantation in ischemic heart disease

BACKGROUND

Until now, cell therapy has constituted a passive therapeutic approach; the only effects seem to be related to the reduction of the myocardial fibrosis and the limitation of the adverse ventricular remodeling. Cardiac resynchronization therapy is indicated in patients with heart failure to correct conduction disorders associated with chronic systolic and diastolic dysfunction. The association of electrostimulation with cellular cardiomyoplasty could be a way to transform passive cell therapy into "dynamic cellular support." Electrostimulation of ventricles following skeletal myoblast implantation should induce the contraction of the transplanted cells and a higher expression of slow myosin, which is better adapted for chronic ventricular assistance. The purpose of this study is to evaluate myogenic cell transplantation in an ischemic heart model associated with cardiac resynchronization therapy.

METHODS

Twenty two sheep were included. All animals underwent myocardial infarction by ligation of 2 coronary artery branches (distal left anterior descending artery and D2). After 4 weeks, autologous cultured myoblasts were injected in the infarcted areas with or without pacemaker implantation. Atrial synchronized biventricular pacing was performed using epicardial electrodes. Echocardiography was performed at 4 weeks (baseline) and 12 weeks after infarction.

RESULTS

Echocardiography showed a significant improvement in ejection fraction and limitation of left ventricular dilatation in cell therapy with cardiac resynchronization therapy as compared with the other groups. Viable cells were identified in the infarcted areas. Differentiation of myoblasts into myotubes and enhanced expression of slow myosin heavy chain was observed in the electrostimulated group. Transplantation of cells with cardiac resynchronization therapy caused an increase in diastolic wall thickening in the infarcted zone relative to cells-only group and cardiac resynchronization therapy-only group.

CONCLUSIONS

Biventricular pacing seems to induce synchronous contraction of transplanted myoblasts and the host myocardium, thus improving ventricular function. Electrostimulation was related with enhanced expression of slow myosin and the organization of myoblasts in myotubes, which are better adapted at performing cardiac work. Patients with heart failure presenting myocardial infarct scars and indication for cardiac resynchronization therapy might benefit from simultaneous cardiac pacing and cell therapy.

The effects of aetiology on outcome in patients treated with cardiac resynchronization therapy in the CARE-HF trial

AIMS

Cardiac dyssynchrony is common in patients with heart failure, whether or not they have ischaemic heart disease (IHD). The effect of the underlying cause of cardiac dysfunction on the response to cardiac resynchronization therapy (CRT) is unknown. This issue was addressed using data from the CARE-HF trial.

METHODS AND RESULTS

Patients (n = 813) were grouped by heart failure aetiology (IHD n = 339 vs. non-IHD n = 473), and the primary composite (all-cause mortality or unplanned hospitalization for a major cardiovascular event) and principal secondary (all-cause mortality) endpoints analysed. Heart failure severity and the degree of dyssynchrony were compared between the groups by analysing baseline clinical and echocardiographic variables. Patients with IHD were more likely to be in NYHA class IV (7.5 vs. 4.0%; P = 0.03) and to have higher NT-proBNP levels (2182 vs. 1725 pg/L), indicating more advanced heart failure. The degree of dyssynchrony was more pronounced in patients without IHD (assessed using mean QRS duration, interventricular mechanical delay, and aorta-pulmonary pre-ejection time). Left ventricular ejection fraction and left ventricular end-systolic volume improved to a lesser extent in the IHD group (4.53 vs. 8.50% and -35.68 vs. -58.52 cm(3)). Despite these differences, CRT improved all-cause mortality, NYHA class, and hospitalization rates to a similar extent in patients with or without IHD.

CONCLUSION

The benefits of CRT in patients with or without IHD were similar in relative terms in the CARE-HF study but as patients with IHD had a worse prognosis, the benefit in absolute terms may be greater.

Comparison of benefits and mortality in cardiac resynchronization therapy in patients with atrial fibrillation versus patients in sinus rhythm (Results of the Spanish Atrial Fibrillation and Resynchronization [SPARE] Study)

The efficacy of cardiac resynchronization therapy (CRT) in patients with atrial fibrillation (AF) and the need for atrioventricular junction ablation in these patients is controversial. The aim of the study was to analyze CRT results in patients with permanent AF. A total of 470 consecutive patients who underwent CRT in 6 centers were included in this study. Of these patients, 126 (27%) had permanent AF. Patients were evaluated at baseline and 12 months. No difference was found in the magnitude of improvement experienced by patients with AF compared with those in sinus rhythm (SR) with respect to quality of life, distance in 6-minute walking test, and left ventricular reverse remodeling. Despite the beneficial effects of CRT, death from refractory heart failure at 12 months was higher in patients with AF (17 of 126; 13.5%) than those in SR (14/344; 4.1%; p <0,001). Furthermore, permanent AF was an independent predictive factor for mortality from refractory heart failure (hazard ratio 5.4, 95% confidence interval 1.9 to 15.1). In conclusion, patients with AF treated with CRT who survived at the 12-month follow-up had the same functional improvement and remodeling as those in SR. However, AF was an independent risk factor for mortality from heart failure after CRT implantation.

Usefulness of pulmonary artery pressure by echocardiography to predict outcome in patients receiving cardiac resynchronization therapy heart failure

Secondary pulmonary hypertension is a marker of advanced heart failure (HF) that confers a poor prognosis. Consecutive patients from 2004 through 2005 who underwent echocardiographic assessments of systolic pulmonary arterial pressure (SPAP) before the implantation of cardiac resynchronization therapy defibrillators were included. Patients were divided into tertiles according to baseline SPAP. Patients in the lowest (group I, 20 to 29 mm Hg) and highest (group III, 45 to 88 mm Hg) tertiles were compared for the end points or death or transplantation and for HF hospital admission. Two hundred seventy patients were evaluated, of whom 95% were Caucasians and 91% men. The mean age was 66.5 +/- 11.6 years, the mean QRS duration was 155 +/- 30 ms, the mean left ventricular ejection fraction was 22.6 +/- 9.7%, and the mean New York Heart Association functional class was 3.0 +/- 0.4. In a multivariate model, death or transplantation was significantly more likely in group III (hazard ratio 2.62, 95% confidence interval 1.1 to 6.4, p = 0.036), as was HF admission (hazard ratio 6.35, 95% confidence interval 2.6 to 15.8, p <0.001). In patients with follow-up echocardiographic assessments, a reduction in SPAP was a significant predictor of freedom from the combined end point (hazard ratio 0.29, 95% confidence interval 0.12 to 0.76, p = 0.011). In conclusion, elevated baseline SPAP in patients who underwent cardiac resynchronization therapy is an independent predictor of all-cause mortality or transplantation and HF admission. A decrease in SPAP on follow-up echocardiography is an independent positive prognostic marker.

Response to Cardiac Resynchronization Therapy Predicts Survival in Heart Failure: A Single-Center Experience

OBJECTIVE

To determine whether survival after cardiac resynchronization therapy (CRT) is related to improvement in clinical or echocardiographic parameters.

BACKGROUND

In clinical trials, CRT improved symptoms, left ventricular (LV) structure, function, and survival. In clinical practice, response to CRT is highly variable and whether survival benefit is confined to those patients who experience improvement in clinical status or cardiac structure and function is unclear.

METHODS

This is a single-center study of patients receiving clinically indicated CRT between January 2002 and December 2004.

RESULTS

Of 309 patients (age 68 +/- 11 years, 83% male) receiving CRT at our institution during the study period, 174 returned for follow-up and 127 had repeat echocardiography. Baseline clinical characteristics and survival were similar among those who did or did not return for follow-up. In paired analyses, New York Heart Association (NYHA) class (-0.56 +/- 0.07, p < 0.0001), ejection fraction (EF, 6.3 +/- 0.7%, P < 0.0001), LV dimension (-2.7 +/- 0.6 mm, P < 0.0001), pulmonary artery systolic pressure (PASP, -4.6 +/- 1.3 mm Hg, P = 0.0007), and MR severity grade (-0.20 +/- 0.05, P = 0.0002) improved after CRT. Survival after CRT was associated with decrease in NYHA class (risk ratio [RR]= 0.43, P = 0.0004), increase in EF (RR = 0.94, P = 0.02), and decrease in PASP (RR = 0.96, P = 0.03). Change in EF and NYHA class were correlated (r = -0.46, P < 0.0001) and, adjusting for this covariance, change in NYHA (P = 0.04) but not EF (P = 0.12) was associated with improved survival.

CONCLUSION

Patients who experience improved symptoms, ventricular function, and/or hemodynamics have better survival after CRT. These data enhance understanding of the relationship between CRT clinical response and survival benefit in clinical practice.

Baseline predictors of cardiac events after cardiac resynchronization therapy in patients with heart failure secondary to ischemic or nonischemic etiology

We evaluated the value of baseline parameters derived from tissue Doppler imaging (TDI) for event prediction in patients with heart failure (HF) secondary to ischemic and nonischemic cause who underwent cardiac resynchronization therapy (CRT). Seventy-four consecutive patients with HF (mean age 59 +/- 11 years) underwent CRT. Baseline clinical parameters included New York Heart Association class, 6-minute walking distance, HF cause, and diabetes. TDI-derived parameters included lateral and septal E/E' ratios defined as peak early left ventricular (LV) filling velocity (E wave) to TDI-derived peak early diastolic velocity of the mitral annulus (E' wave). During a median follow-up of 720 days, 21 patients (28%) had cardiac death or hospitalization for HF. These patients more often had an ischemic cause (p <0.05), diabetes (p <0.05), and restrictive filling (p <0.001), less often had LV dyssynchrony (p <0.05), and had higher septal and lateral E/E' ratios (p <0.001 for the 2 comparisons). In a multivariable model using a forward selection algorithm, only the lateral E/E' ratio remained an independent predictor of cardiac outcome. After 3 months of CRT, TDI-derived systolic mitral annular systolic and diastolic velocities improved significantly in nonischemic patients for the septal and lateral sides. In contrast, in ischemic patients no significant improvements were seen. Significant improvements were seen in septal and lateral E/E' ratios in ischemic and nonischemic patients. However, the improvement in lateral E/E' ratio was significantly less and absolute 3-months E/E' ratios were worse in ischemic patients. In conclusion, baseline lateral E/E' ratio is an independent predictor for cardiac events in patients with HF treated with CRT. The worse clinical outcome in ischemic patients may be due to failure of improvement in systolic and diastolic mitral annular velocities after CRT, resulting in a less pronounced improvement in LV filling pressures as demonstrated by this E/E' ratio.