Background: Myocardial scars cause heterogeneous ventricular activation, which results in fragmented QRS (f-QRS) complexes and the resultant left ventricular (LV) dysfunction and dyssynchrony and thus further mortality. The accurate management of this patient population is essential to lessen mortality and improve the quality of life.
 
Methods: The present cross-sectional study recruited 80 patients (40 with f-QRS and 40 with non–f-QRS) who underwent cardiac resynchronization therapy defibrillator (CRT-D) implantation and followed them up for 6 months. The 2 groups were compared, before and after CRT-D implantation, concerning the New York Heart Association functional class; the quality of life; the incidence of all arrhythmias, including tachyarrhythmias; echocardiographic findings; the number of hospitalization; and mortality.
 
Results: The study population consisted of 80 patients at a mean age of 62.05±11.25 years: 40 cases with f-QRS and 40 with non–f-QRS. Men comprised 68.8% (n=55) of the patients. Ischemic cardiomyopathy was detected in 62.5% of the patients, nonischemic cardiomyopathy in 37.5%, and sinus rhythm in 76 cases. The mean values of the LV ejection fraction, the LV end-diastolic diameter, and the LV end-systolic diameter in both groups were 17.12±5.77, 6.44±0.81, and 5.70±0.81, respectively (P<0.05). An improvement was observed among the patients with non–f-QRS in echocardiography after CRT-D implantation, which was not related to the incidence of ischemic or nonischemic LV dysfunction. Dyspnea on exertion and mitral regurgitation improved in both groups (P>0.05).
 
Conclusions: The presence of f-QRS in patients with heart failure could confirm a diminished response to CRT-D implantation according to echocardiographic findings and could be considered an accurate patient selection guide. (Iranian Heart Journal 2021; 22(2): 77-82)