No Association Found Between Ischemia and Rate of Congestive Heart Failure Hospitalization Following Cardiac Resynchronization Therapy

Introduction: The myocardial scarring resulting from ischemic coronary artery disease (CAD) can interfere with effective lead placement during the implantation of multilead cardioverter defibrillators for cardiac resynchronization therapy (CRT). Extensive myocardial scarring has been associated with poorer physiological and survival outcomes. Objective: This study evaluated whether CRT recipients with ischemic cardiomyopathy respond as well as recipients with nonischemic cardiomyopathy, using hospital admission for congestive heart failure (CHF) as a measure of response. Methods: Individuals who had undergone CRT in 2013 and had been hospitalized for CHF in the 12 months prior to implantation were identified from a large private health insurer's claims database. Participants had to have 12 months of continuous enrollment before and after implantation. The study sample was divided into a nonischemic and an ischemic group, and a subset of the ischemic group with a diagnosis of ST elevation myocardial infarction (STEMI) was identified and considered to be representative of individuals with the greatest likelihood of scarring. The rate of CHF hospital admission in the 12 months post-implantation was computed for each group. Both the entire ischemic group and the STEMI subset were separately compared with the nonischemic group. Two-tailed p-values from Fisher's exact test were used to evaluate the significance of the association between ischemia and post-implantation CHF hospitalization. Results: The number of people excluded for not having a CHF admission in the year prior to implant was 802, 143, and 51 for the nonischemic, ischemic, and STEMI groups respectively. No significant differences were found in the rates of post-implantation CHF admissions between the groups which were compared. CHF hospitalizations occurred in 38/200 people in the nonischemic group (19%), 17/71 in the ischemic group (24%), and 6/34 in the STEMI group (18%). The rate of CHF admissions post-implant was not significantly different in the ischemic versus nonischemic comparison (P = .39) or in the STEMI versus nonischemic comparison (P = 1.00). Conclusions: No association was found between the presence of ischemic heart disease, or even an ischemic event likely to produce a high degree of scarring, and the likelihood of being hospitalized for CHF in the year after undergoing CRT. While the small sample size limited the power of the study, in all of the groups, people had a ≤ 24% chance of CHF admission in the year post-implantation, although they had experienced a CHF admission in the year prior. Thus, no evidence was found to suggest that physicians should be advised to restrict the use of CRT in patients with a history of ischemic heart disease or evidence of myocardial scarring.