Right ventricular apical pacing in patients with previous left bundle brunch block

The aim of the study was to compare the functional effects of right ventricular apical pacing (RVAP) with spontaneous ventricular activation in heart failure patients with and without LBBB. 12 patients (mean age 65 ± 9, 5 women, NYHA 2–3, DDD pacemakers implanted for brady-arrythmias) devided in two group. Group I consisted of 6 heart failure patients with LBBB. Group II consisted of 6 heart failure patients without LBBB. Age, gender, NYHA class, pacemaker indication, RR interval, AV delay, diagnosis, LV size were similiar in the two groups. All patients underwent Echo Doppler examination before and after 29±4 days of continuous RVAP. The following parametars were measured: electromechanical delay (EMD) – the time from ventricular spike during RVAP or the onset of QRS to the onset of contraction of the last activated LV segment (posterior wall); Interventricular contraction delay (IVCD) – as the time between onset of aortic and pulmonary flow; LV diastolic filling duration, preejection time and ejection time. Group I: RVAP was associated with no significant difference in QRS width (148±24 vs 139±31ms, NS), significant shortening of EMD (170±11 vs 179±22ms, p<0.01) and significant shortening of IVCD (71±18 vs 79±21ms, p<0.05), while LV filling time, preejection time and ejection time showed no significant differences. Group II: RVAP was associated with no significant difference in QRS width (101±29 vs 89±21ms, p>0.05), significant longer EMD (129±14 vs 98±10 ms, p<0.05), significant longer IVCD (61±20 vs 17±8ms p<0.01); LV filling time was shorter (324±61 vs 357±61 ms, p<0.05). Preejection time and ejection time showed no significant difference. RVAP can reduce the degree of LV asynchrony in heart failure pts with LBBB, while in heart failure pts without LBBB, RVAP worsening LV perfomance and induced higher degree of interventricular desynchronization. In pts with reduced LV function the RVAP should be minimal or CRT should be considered.