JACC study shows benefit of ICDs for primary prevention in non ischemic cardiomyopathy

Does the use of ICD as a primary prevention modality provide similar protection in all forms of cardiomyopathy?

Although current guidelines recommend primary prevention ICD therapy irrespective of the type of cardiomyopathy for the prevention of sudden cardiac death (SCD) among patients with significantly reduced left ventricular ejection fraction and symptoms of heart failure, some recent observations like the DANISH trial have questioned the efficacy of such therapy among patients with nonischemic cardiomyopathy (NICMP).

A recent study published in JACC Clinical Electrophysiology has investigated the potential differences in outcomes between patients with ischemic cardiomyopathy (ICMP) versus (NICMP) treated with ICD therapy for the primary prevention of SCD in a combined database of 5 landmark ICD trials conducted between 1997 and 2017. The results from this study have shown that patients with NICMP also experience a similar risk of life-threatening ventricular arrhythmic events as patients with ICMP but have a lower incidence of death related to cardiac and noncardiac causes. This supports the use of ICD as primary prevention modality in this population.

Authors Narins et al analysed 4803 patients with ICMP (n = 3,106) or NICMP (n = 1,697) with a primary prevention ICD enrolled in 5 randomized trials conducted between 1997 and 2017.( MADIT-II, M2Risk, MADIT-CRT, MADIT-RIT, and the RAID trials).

The primary end point was sustained ventricular tachycardia (VT) ≥200 beats/min or ventricular fibrillation (VF). Secondary end points included appropriate ICD therapy and all-cause mortality. Differences in cause-specific mortality, including noncardiac, sudden cardiac, and non-sudden cardiac death, were also examined.

Patients with ICMP were significantly older and had more comorbid conditions, whereas those with NICMP had a more advanced heart failure class at enrollment and were more often prescribed medical or cardiac resynchronization therapy for heart failure.

Multivariate analysis showed that ICMP versus NICMP had a similar risk of VT/VF events and appropriate ICD therapy, whereas the risk of all-cause mortality was 1.8-fold higher among ICM versus NICM patients dominated by non-sudden cardiac mortality.

Whereas individuals with ICMP demonstrated consistent mortality benefit in large multicenter randomized trials of ICD versus conventional medical therapy performed in the early 2000s, randomized trials examining ICD implantation for patients with NICMP have yielded variable results.

Significant differences in demographic variables and comorbid conditions exist between patients with ischemic and nonischemic cardiomyopathies, which may contribute to disparities in outcomes. As expected, because ICMP is a byproduct of advanced atherosclerotic coronary artery disease, individuals with ICMP in the study patient population were significantly older, more often male, and had more atherosclerotic risk factors and noncardiac conditions than those with NICMP. This could have confounded the results of trials challenging the use of ICDs in NICMP.

ICD placement is expected to provide the greatest mortality benefit among patient groups who have a high risk of potentially lethal arrhythmic events, but a low risk of death related to nonarrhythmic causes such as progressive heart failure or noncardiac conditions.

"Within our cohort, the occurrence of ventricular arrhythmias was equal between the ICM and NICM groups, whereas mortality related to nonarrhythmic causes was less frequent with NICM. Although speculative and in need of confirmation in dedicated clinical trials, this observation supports the hypothesis that a potential "benefit" of ICD therapy may exist for appropriately selected patients with NICM", note authors in discussion.

These findings provide support for ongoing research aimed at further delineating which individuals with ICM and NICM are most likely to benefit from ICD therapy.

Source: JACC Clinical Electrophysiology: DOI: 10.1016/j.jacep.2021.06.020