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Cardiac Resynchronization Therapy for Non-ischemic Cardiomyopathy—Immediate Changes in QRS Duration, with Left Bundle Branch Block Pattern on Electrocardiogram

Saurav Chatterjee, Gunjan Guha and Joydeep Ghosh
American Heart Hospital Journal Volume 9 No.1

Background: We evaluated mean QRS duration improvement immediately after cardiac resynchronization therapy (CRT) in patients with non-ischemic cardiomyopathy (NICM), with a left bundle branch block (LBBB) pattern on electrocardiogram (ECG), owing to obligatory right ventricular pacing or as a new finding; and to what extent. Methods and results: We tabulated ECGs of 18 subjects, 24 hours before and after receiving CRT, for both groups. The percentage decreases of QRS duration in all groups were statistically similar (p<0.05). There was a significant negative correlation (p<0.05) between age and the percentage of the QRS decrease. Conclusions: The study showed a greater reduction in QRS duration with CRT for younger subjects.

Conventional right ventricular (RV) apical pacing has been indicated to have deleterious effect on left ventricular (LV) systolic function.1 Biventricular (BiV) pacing and cardiac resynchronization therapy (CRT) has been found to arrest decline of LV systolic function and prevent cardiac remodeling in patients with heart failure. A widened QRS complex on electrocardiogram (ECG) of a patient with chronic heart failure has been demonstrated to indicate worsening of LV systolic function2 as well as correlated with an increased risk of death.3,4,5 Biventricular pacing has been postulated to have a beneficial effect on symptoms of patients with medically refractory chronic heart failure and widened QRS complex.6 It has been suggested that non-ischemic cardiomyopathy (NICM) patients with CRT have a better prognosis than those with ischemic cardiomyopathy.7 Our study aimed to evaluate if CRT therapy improved QRS duration, and to what extent, within 24 hours of biventricular pacemaker insertion in subjects with NICM having a left bundle branch block pattern (LBBB) on ECG. The study also aimed to evaluate if presence of atrial fibrillation/flutter contributed to observed outcome.

Methods
Eighteen patients (mean age 67.3 yrs) with NICM--four women and 14 men—with left bundle branch block (LBBB) pattern on ECG, that underwent biventricular pacemaker implantation for CRT between June, 2009 and December, 2009 were included. Four subjects (three men and one woman) were on prior RV pacing, which produced the LBBB pattern on ECG, and were receiving an upgrade to bi-ventricular pacing and CRT. The other 14 subjects included had LBBB pattern on ECGs and were eligible for de novo CRT with bi-ventricular pacing because of NICM.

ECGs of subjects were done 24 hours before receiving CRT as well as within 24 hours after bi-ventricular pacemaker implantation, and tracings were compared for changes in QRS duration. Also, prior atrial fibrillation/flutter was noted. The mean values of QRS duration from three blinded observations were tabulated and analyzed to eliminate inter-observer variability.

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  • 1. Resident, Dept of Internal Medicine, Maimonides Medical Center, Brooklyn, New York; 2. Research Scholar (Doctoral), Oregon State University, Corvallis, Oregon; 3. Associate Director, Electrophysiology, Maimonides Medical Center, Brooklyn, New York
  • Correspondence: Saurav Chatterjee, MD, Dept of Internal Medicine, Maimonides Medical Center, Brooklyn, New York. E: saurav.sphs@gmail.com