Comparative outcomes of ischemic and non-ischemic dilated cardiomyopathy in ICD recipients: a 30-Year retrospective analysis

Ischemic cardiomyopathy (ICM) and non-ischemic dilated cardiomyopathy (NIDCM) are the two main entities included in the landmark studies that established the use of implantable-cardioverter-defibrillators (ICDs). While arrhythmogenesis is in both cases triggered primarily in fibrotic areas of the ventricular myocardium due to reentry mechanisms, little is known regarding outcomes of patients with ICM vs NIDCM after the implantation of the ICD.

Data from the ICD registry of our Cardiology department were analyzed. The registry encompasses data from 1993 to present day. All patients that receive an ICD for primary or secondary prevention in our hospital are registered. We retrospectively compared the two main subgroups of patients, those with ICM to NIDCM regarding appropriate therapies from the ICD (anti-tachycardia pacing or shock) during a mean follow up period of over 15 years.

A total of 1582 patients were included in the analysis. Of them, 1064 suffered from ICM and the rest (518 patients) from NIDCM. The majority of the patients were male (91%). In the whole cohort, 1265 patients received an ICD for primary prevention and 317 patients for secondary prevention. In 77.3% of the patients an electrophysiological study (EPS) to induce ventricular arrhythmias (VA) was conducted. In 45.6% of patients a sustained VA was induced. Regarding the risk of receiving an appropriate therapy, ICM patients in general did not differ from the NIDCM ones (26.4 % vs 30.7%, p=0,074), nor did patients in the primary prevention subgroup, respectively (23% vs 26%, p=0.18). On the contrary, in the secondary prevention subgroup, NIDCM patients received appropriate therapies more often than the ICM ones, a difference that reached statistical significance (52.3% vs 37.9%, p=0.021)

In secondary prevention ICD recipients the risk of malignant arrhythmias is substantially higher in the NIDCM subgroup vs ICM. A possible genetic background giving rise to more wild phenotypes in NIDCM patients in accordance with the evolving nature of the arrhythmogenic substrate in NIDCM seem to play a significant role.