Causes-of-Death Analysis of Patients With Cardiac Resynchronization
What are the causes of death among patients with cardiac resynchronization therapy pacemaker (CRT-P) compared with cardiac resynchronization defibrillator (CRT-D) in clinical practice?
CeRtiTuDe was a multicenter prospective follow-up cohort study. Mortality rates were compared between patients with and without a defibrillator, and analyzed using Cox proportional hazards regression.
The study enrolled 1,705 patients: 535 patients with CRT-P and 1,170 with CRT-D. Compared with CRT-D patients, subjects with CRT-P were older, less often male, more symptomatic, had less coronary artery disease, wider QRS, more atrial fibrillation, and more comorbidities. At 2-year follow-up, the annual overall mortality rate was 83.8 per 1,000 person-years. The crude mortality rate among CRT-P patients was double compared with CRT-D (relative risk, 2.01; 95% confidence interval [CI], 1.56-2.58). In a Cox proportional hazards regression analysis, CRT-P remained associated with increased mortality (hazard ratio, 1.54; 95% CI, 1.07-2.21; p = 0.021), although other potential confounders may have persisted. By cause-of-death analysis, 95% of the excess mortality among CRT-P subjects was related to an increase in nonsudden death.
In this large cohort of consecutive patients in France, the excess mortality in CRT-P recipients over CRT-D patients was mainly due to nonsudden death. This suggests that CRT-P patients are appropriately selected in clinical practice.
This study reminds us that competing risks for mortality need to be carefully considered in patients, who ostensibly qualify for defibrillator therapy. Large randomized clinical trials, which established the value of CRT-D in heart failure patients, had exclusion criteria reducing the number of patients with significant comorbidities. The investigators in the present study did not provide the implanting physicians with guidelines about who should receive CRT-D vs. CRT-P; they were merely observers of the prevalent practice pattern. The clinicians, however, appear to have made the right call most of the time. The rates of heart failure hospitalization were greater in the CRT-P group, which is consistent with the greater heart failure mortality in this group. On the other hand, it is also possible that by promoting remodeling of the left ventricle, CRT may ameliorate the substrate for ventricular arrhythmias, resulting in fewer sudden deaths. The study was not randomized, and should not be interpreted to suggest lack of benefit of CRT-D over CRT-P in general.
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