BACKGROUND: Biventricular pacing (BiV) is employed as the current standard for cardiac resynchronisation therapy. Other pacing modalities have been proposed as alternatives; however, data on changes in electrical activation sequence caused by pacing from various sites are limited. AIM: To describe changes in activation patterns during different ventricular pacing modes in patients with chronic heart failure. METHODS: A total number of 20 patients (mean age 59.6+/-8 years) with chronic heart failure, intraventricular conduction abnormality (QRS >130 ms) or complete AV block were studied. Endocardial activation maps of both ventricles (CARTOTM, Biosense-Webster) were obtained during spontaneous rhythm and biventricular (BiV, n=9), right ventricular bifocal (BiF, n=7) and single-site left ventricular (LV, n=4) pacing. The following parameters were assessed: activation pattern, total LV endocardial activation time (LVAT) and electrical interventricular delay (IVD). RESULTS: Right ventricular apical pacing was associated with the longest LVAT (145+/-24 ms). On the contrary, both BiV and BiF pacing shortened LVAT with BiV being superior in the degree of LVAT reduction (89+/-13 vs 103+/-10 ms, p<0.05). BiV pacing also significantly shortened IVD and modified the LV activation sequence in a complex manner. Such changes were not observed during BiF pacing. In the presence of fusion with spontaneous activation, single-site LV pacing was comparable to BiV pacing. CONCLUSIONS: Among the different pacing modes, BiV pacing and single-site LV pacing with fusion resulted in the most pronounced changes in ventricular activation that appear to be a prerequisite for successful resynchronization of both ventricles.

Department of Cardiology Institute for Clinical and Experimental Medicine Vídenská 1958 9 14021 Praha 4 Czech Republic