Improved acute haemodynamic response to cardiac resynchronization therapy using multipoint pacing cannot solely be explained by better resynchronization

The recently developed quadripolar left ventricular (LV) leads have been developed to increase the benefit of cardiac resynchronization therapy (CRT). These leads offer the option to stimulate the LV on multiple sites (multipoint pacing, MPP). Invasive haemodynamic measurements have shown that MPP increases haemodynamic response. To investigate whether the beneficial effect of MPP can be explained by better electrical resynchronization. Different LV lead locations were tested during biventricular (BiV) pacing and MPP in 29 CRT candidates. The 12-lead electrocardiogram (ECG) and the invasive LV pressure curves were measured simultaneously. The Kors matrix was used to convert the ECG into a vectorcardiogram (VCG). The acute haemodynamic benefit of MPP was compared with the reduction in QRS duration and VCG-derived QRS area. Out of the 29 patients, three patients were excluded due to missing LV pressures or ECG measurements. In the remaining 26 patients MPP resulted in a significant haemodynamic improvement compared to BiV pacing without a significant change in QRS duration and QRS area. In only 5 out of the 26 patients the QRS area decreased during MPP compared to BiV pacing. In 17 patients MPP did not change QRS duration and significantly increased QRS area but moved the direction of the maximal QRS vector (azimuth) more opposite from baseline compared to BiV pacing. In 4 patients the QRS area was small during baseline, indicating limited electrical dyssynchrony. The acute haemodynamic benefit of MPP over BiV pacing is achieved by either electrical resynchronization (reduction in QRS area) or by a rotation of the maximal QRS vector, indicating a more LV dominated activation sequence. The latter property was found in two-thirds of the cohort studied.