Echocardiographic assessment of the effects of acute left ventricular pacing on patients with severe congestive heart failure and narrow QRS duration

Introduction

More than 20% of patients with congestive heart failure (CHF) exhibit one form or another of mechanical dyssynchrony, intraventricular conduction impairment, or bundle branch block. The concept of dual-chamber pacing in refractory heart failure was introduced to be followed later by the technique of biventricular pacing to restore cardiac synchrony in the failing heart. The aim of the present study was to address the issue of applying the technique of left ventricular (LV) pacing to that substrate of heart failure patients with a narrow rather than wide QRS complex, and with LV rather than biventricular pacing in order to permit the use of an ordinary dual-chamber pacemaker.

Methods

We conducted an acute study on 20 patients (15 male, five female; mean age 43 years); all had CHF (12 ischemic and eight idiopathic) with normal QRS duration on ECG. All patients were under maximal tolerated doses of antifailure treatment. All patients were subjected to M-mode and two-2D echocardiography to measure: left ventricular end-diastolic dimension (LVEDD), left ventricular end-systolic dimension (LVESD), fractional shortening (FS), ejection fraction (EF), mitral regurge area and cardiac output before and 15 minutes after LV pacing. All patients were subjected to temporary dual-chamber right atrium, LV pacing; the LV lead was passed retrogradely via the transaortic route. The pulmonary capillary wedge pressure (PCWP) was measured using a trilumen, balloon-tipped thermodilution Swan–Ganz catheter. Patients were divided into group I (PCWP >15 mmHg, 10 patients) and group II (PCWP <15 mmHg, 10 patients).

Results

Echocardiographic measurements after pacing in group I showed significantly lower LVEDD (5.12 vs. 6.53 cm, P < 0.004), lower LVESD (4.01 vs. 4.65 cm, P < 0.034), smaller mitral regurge area (9.7 vs. 13.4 cm², P < 0.005), higher FS (18.9 vs. 17, P < 0.04) and higher EF (37.9 vs. 35.5%, P < 0.02). In contrast, following pacing in group II, the hemodynamics were not significantly different from pre-pacing values.

Conclusion

Single LV – rather than biventricular – pacing could achieve remarkable hemodynamic beneficial effects in patients with CHF even with normal QRS, but only in that substrate of patients with a high PCWP. Although this is an acute study, our findings open the scope for widespread application of the concept of multisite pacing.