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CRT-D vs. CRT-P in Nonischemic Cardiomyopathy
Study Questions:
Can mid-wall fibrosis determined by cardiac magnetic resonance imaging (CMR) be helpful in selecting patients with nonischemic cardiomyopathy (NICM) for cardiac resynchronization therapy (CRT) with defibrillation (CRT-D) versus pacing (CRT-P)?
Methods:
The investigators retrospectively reviewed patients who underwent CRT-D or CRT-P placement and preimplant CMR to identify patients with NICM at two hospitals in the United Kingdom. Patients with prior myocardial infarction, coronary revascularization, diagnosis of ischemic cardiomyopathy, ischemic pattern scar on CMR, diagnosis of hypertrophic or restrictive cardiomyopathy, primary valvular abnormality, sarcoidosis, amyloidosis, or myocarditis were excluded. Patients were followed for a primary outcome of survival free of heart transplant or left ventricular assist device. Cox proportional hazards regression was used to estimate the independent impact of late gadolinium enhancement (LGE) on outcomes.
Results:
Among 252 patients identified, 68 (27%) had mid-wall fibrosis on LGE CMR imaging. Over a median follow-up of approximately 4 years, a total of 92 patients experienced the primary endpoint for annualized rate of 12.8% in those with mid-wall fibrosis compared to 6.9% among those without. After adjustment for age, New York Heart Association (NYHA) class, CRT type, hypertension, and atrial rhythm, mid-wall fibrosis was associated with an adjusted hazard ratio of 2.31 (95% confidence interval, 1.45-3.68) and a c-statistic of 0.70. Similar trends were seen for broader composite endpoints including heart failure hospitalization and major adverse cardiac events. Intriguingly, mid-wall fibrosis was more strongly associated with sudden cardiac death (adjusted hazard ratio, 3.75) than pump failure (adjusted hazard ratio, 1.95). Furthermore, there was a significant interaction between mid-wall fibrosis and device type (CRT-D vs. CRT-P) such that CRT-D was associated with lower mortality in those with mid-wall fibrosis (hazard ratio, 0.23), but not those without it.
Conclusions:
Among patients with NICM and mid-wall LGE, CRT-D was associated with better outcomes than CRT-P, but not among those without mid-wall LGE.
Perspective:
This important study finds observational evidence that CMR may be helpful in selecting patients who may find benefit from CRT-D over CRT-P. Given the negative results of the recently published DANISH trial suggesting that defibrillators may not improve outcomes, in general, among patients with NICM, there is renewed interest in better tools for risk stratification. This study shows that mid-wall LGE, which has previously been associated with adverse prognosis in NICM, may be useful for this purpose. This hypothesis deserves further testing in a prospective trial. The authors also only focused on mid-wall fibrosis to the exclusion of patchy, transmural, epicardial, and sub-endocardial fibrosis patterns. Whether similar results would be seen with these additional forms of scar is also an important question.
Keywords: Arrhythmias, Cardiac, Cardiac Imaging Techniques, Cardiac Pacing, Artificial, Cardiac Resynchronization Therapy, Cardiomyopathies, Death, Sudden, Cardiac, Defibrillators, Endomyocardial Fibrosis, Gadolinium, Heart-Assist Devices, Heart Failure, Heart Transplantation, Hypertension, Magnetic Resonance Imaging, Treatment Outcome
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