BiV Pacing in Class IV Heart Failure
BiV Pacing in Class IV Heart Failure
Abstract & Commentary
By John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville. Dr. DiMarco is a consultant for Novartis, and does research for Medtronic and Guidant.
Synopsis: Cardiac resychronization therapy reduces morbidity and mortality in class IV heart failure patients.
Source: Lindenfeld J et al. Effects of Cardiac Resynchronization Therapy With or Without a Defibrillator on Survival and Hospitalizations in Patients With New York Heart Association Class IV Heart Failure. Circulation. 2007; 115:204-212.
This report from the companion trial details the effects of cardiac resynchronization with or without defibrillation in patients with ambulatory class IV heart failure. The COMPANION trial was a randomized trial that compared optimal pharmacologic therapy, cardiac resynchronization therapy (CRT), and cardiac resynchronization therapy plus defibrillation (CRT-D) in patients with ischemic or nonischemic cardiomyopathy, class III or class IV heart failure, an ECG QRS interval of at least 120 msec, sinus rhythm and a hospitalization for the treatment of heart failure within 12, but not within one month, of enrollment. Enrolled patients were randomly assigned in a 1:2:2 ratio to pharmacologic therapy, CRT or CRT-D. This report focuses on the subset of 217 of the 1,520 COMPANION patients who were classified at the time of enrollment as having New York Heart Association class IV heart failure.
In comparison to the NYHA class III patients in COMPANION, the NYHA class IV patients had a slightly longer duration of heart failure, a lower ejection fraction, a shorter 6-minute walk distance, lower systolic and diastolic blood pressure, and decreased use of ACE inhibitors or beta blockers, the latter, presumably because of intolerance.
The primary endpoint in COMPANION was time to death or hospitalization for any cause. Time to the primary endpoint was significantly prolonged by both CRT and CRT-D compared with medical therapy among Class IV patients, as well as in the overall trial. Favorable trends for all-cause mortality were observed, but were not significant because of the relatively small size of the ambulatory class IV cohort (hazard ratios 0.67 for CRT and 0.63 for CRT-D). Time-to-death or heart failure hospitalization was also significantly improved with both CRT and CRT-D compared with medical therapy. Time-to-sudden-death was significantly prolonged by CRT-D, but not by CRT compared to medical therapy. Time-to-heart-failure-death showed favorable trends with both CRT and CRT-D, but these trends were not statistically significant.
Despite these improvements in the survival curves, mortality in this group remained high. At one year in the NYHA class IV patients, 44% of medical therapy patients had died compared with 36% of CRT patients and 30% of CRT-D patients. By 2 years, 62% of medical therapy subjects, 45% of CRT subjects and 55% of CRT-D subjects had died. Comparison with COMPANION patients classified as NYHA class III showed, as would be expected, higher rates of mortality in the ambulatory class IV patients. Many Class IV patients also showed functional improvement. At one month after implant, 67% of NYHA Class IV CRT and CRT-D patients improved at least one NYHA class compared with only 31% of medical therapy patients. Mortality benefit was seen among those who improved their functional status but was not seen in the subset of patients who did not improve their functional status. Quality-of-life score also improved in the CRT and CRT-D patients compared with medical therapy. Only limited data were available on 6-minute walk test duration.
Implantation of the resynchronization device was however more difficult in the heart failure patients in class IV compared to those in class III. Overall, 27 of 162 (17%) class IV patients did not receive a CRT device vs only 105 of 1,050 (10%) class III patients.
The authors conclude that both CRT and CRT-D are beneficial in altering mortality and morbidity in ambulatory class IV patients.
Commentary
Most prior studies on resynchronization therapy and implantable defibrillators have included either no or only a small number of patients classified as having NYHA class IV heart failure symptoms. COMPANION allowed entry of Class IV patients but, in order to be eligible, patients should have been dyspneic at rest with worsening dyspnea on exertion, and yet not have had a hospitalization within the previous 30 days. This is a relatively small subset of Class IV patients often referred to as ambulatory Class IV. Most patients who are chronically in Class IV have frequent hospitalizations or require inotropic support. Current guidelines do not support a role for either ICD therapy or CRT in these Class IV patients, despite the fact that there are some positive small observational studies. In the COMPANION trial, the effects seen in ambulatory class IV patients were qualitatively similar to those seen among class III patients. Although NYHA class is a somewhat subjective assessment, the data here suggest that CRT has potential benefit in ambulatory patients with advanced heart failure on optimal medical therapy who otherwise meet criteria for resynchronization.
Cardiac resychronization therapy reduces morbidity and mortality in class IV heart failure patients.Subscribe Now for Access
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