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Heart Failure

Heart Failure and Ventricular Dyssynchrony

Many patients with advanced systolic heart failure exhibit significant intra- or interventricular conduction delays (IVCD) that disturb the synchronous beating of the ventricles so that they pump less efficiently. This delayed ventricular activation and contraction is referred to as ventricular dyssynchrony and is often seen as a wide QRS complex with a left bundle branch block morphology on ECG.1

ECG depicting interventricular conduction delay
ECG depicting interventricular conduction delay

Ventricular dyssynchrony has been shown to have a number of deleterious effects on cardiac function, including reduced diastolic filling time2, weakened contractility3, protracted mitral regurgitation3, and post-systolic regional contraction4 that together result in diminished stroke volume.

A number of studies have shown a wide QRS to be associated with a poor prognosis. One-year follow-up data from the Italian Network on Congestive Heart Failure (IN-CHF) registry found that the concurrent presence of left bundle branch block and atrial fibrillation with heart failure was associated with a significant increase in mortality, and that this synergistic effect remained significant even after adjusting for clinical variables usually associated with advanced heart failure.5 In a study by Iuliano of 669 NYHA class II-IV heart failure patients, a prolonged QRS was associated with increased mortality (49.3% vs. 34.0%) and sudden death (24.8% vs. 17.4%), while LBBB was associated with worse survival, but not sudden death.6 Finally, in a substudy analysis from the Vesnarinone Study (VEST), patients with NYHA class II-IV heart failure who had a wider QRS (>200 ms) had a five-times greater mortality risk than those with the narrowest QRS duration (<90 ms).7

References
  1. Ventricular pacing: a promising new therapeutic strategy in heart failure. For whom? Editorial. Eur Heart J 2000;21:1211-1214.
  2. Grines CL, Bashore TM, Boudoulas H, et al. Functional abnormalities in isolated left bundle branch block. The effect of interventricular asynchrony. Circulation 1989; 79: 845-853.
  3. Xiao HB, Lee CH, Gibson DG. Effect of left bundle branch block on diastolic function in dilated cardiomyopathy. Br Heart J 1991; 66: 443-447.
  4. Søgaard P, Egeblad H, Kim WY, et al. Tissue Doppler imaging predicts improved systolic performance and reversed left ventricular remodeling during long-term cardiac resynchronization therapy. J Am Coll Cardiol 2002; 30: 723 – 730.
  5. Baldasseroni S, De Biase L, Fresco C, et al; Italian Network on Congestive Heart Failure. Cumulative effect of complete left bundle-branch block and chronic atrial fibrillation on 1-year mortality and hospitalization in patients with congestive heart failure. A report from the Italian network on congestive heart failure (in-CHF database). Eur Heart J 2002; 23(21): 1692-1698.
  6. Iuliano S, Fisher SG, Karasik PE, Fletcher RD, Singh SN, for the Department of Veterans Affairs Survival Trial of Antiarrhythmic Therapy in Congestive Heart Failure. QRS duration and mortality in patients with congestive heart failure. Am Heart J 2002;143:1085-1091.
  7. Gottipaty VK, Krelis SP, Fei Lu K, et al. The Resting Electrocardiogram Provides a Sensitive and Inexpensive Marker of Prognosis in Patients with Chronic Congestive Heart Failure. J Am Coll Cardiol 1999; 33: abstract 145A.

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