LV based pacing in patients with heart failure and a narrow QRS--an acute hemodynamic study

Biventricular pacing is beneficial in refractory systolic heart failure having QRS duration more than 130 msec by improving regional dysynchrony and decreasing diastolic mitral regurgitation. Current data show significant systolic dysynchrony in symptomatic systolic heart failure patients out of which nearly 40% have a QRS duration of less than 120 msec. Our study aims at assessing acute hemo-dynamic impact of Biventricular (BiV) and compare it with isolated left ventricular (LV) pacing in patients of systolic heart failure and QRS duration < or = 120 msec.

Seven patients with symptomatic systolic heart failure with LV Ejection fraction (LVEF) < or = 35% (mean 25.7 +/- 11.3%). NYHA functional class more than II and QRS duration < or = 120 msec (mean 92.8 +/- 17.0 msec) were studied at baseline and following BiV and LV pacing with AV delay 100 msec for 5 minutes in random order. Parameters analyzed were heart rate, systolic BP, pulse pressure, LV dimension, LVEF, cardiac output(CO), LV dP/dT, LV and RV isovolumic contraction time and aorto pulmonary flow delay. Duration of QRS complex at baseline and following pacing was noted. 'Responders' were defined as having increase in CO by at least 10% of mean basal cardiac output in study group.

BiV pacing resulted in significant improvement in systolic BP (140.71 +/- 21.33 vs 149.29 +/- 19.67 mmHg, p = 0.02), pulse pressure (58.14 +/- 21.14 vs 67.29 +/- 19.57 mmHg, p = 0.01), LVEF (25.71 +/- 11.3 vs 32.86 +/- 4.60%, p = 0.01), CO (3.24 +/- 1.05 vs 3.89 +/- 1.1 l/min, p = 0.02) and LV dP/dT (0.69 +/- 0.22 vs 1.00 +/- 0.23 mmHg/msec, p = 0.001) with a trend towards reduction in LV isovolumic contraction time (115.28 +/- 21.61 vs 99.29 +/- 17.18 msec, p = 0.14) and aorto pulmonary flow delay (25.14 +/- 24.36 vs 12.14 +/- 36.15 msec, p = 0.32). LV pacing resulted in a trend towards improvement in parameters as compared to baseline, systolic BP (140.71 +/- 21.33 vs 146.71 +/- 23.03 mmHg, p = 0.16); pulse pressure (58.14 +/- 21.14 vs 63.29 +/- 26.59 mmHg, p = 0.2); LVEF (25.71 +/- 11.3 vs 33.27 +/- 10.0, p = 0.06); CO (3.24 +/- 1.05 vs 3.27 +/- 0.6 l/min, p = 0.88); LV dP/dT (0.69 +/- 0.22 vs 0.96 +/- 0.39 mmHg/msec, p = 0.16); LV isovolumic contraction time (115.28 +/- 21.61 vs 98.21 +/- 21.34 msec, p = 0.18); aortopulmonary flow delay (25.14 +/- 24.36 vs 5.21 +/- 30.1 msec, p = 0.2). Biventricular and LV pacing resulted in a non-significant increase in duration of paced QRS complexes (105.43 +/- 14.82 msec, p = 0.11 and 108.86 +/- 19.73, p = 0.15 respectively) as compared to 92.86 +/- 17.04 msec at baseline. Three out of 7 patients could be classified as 'responders' to biventricular pacing.

BiV pacing, and not LV pacing, benefits patients of systolic heart failure (EF < or = 35%) and narrow QRS (< or = 120 msec) on surface ECG.