136-60: Can the QRS morphology predict the latest activated site during CRT implantation using an electroanatomic mapping of the coronary venous?

Purpose: In order to have a good clinical response, CRT is nowadays performed positioning the LV lead in the latest activated region (LAR), usually placed in the lateral wall, avoiding the apical position. The aim of the study is to describe the anatomical position of LAR related to different QRS morphology using EnSite Velocity electroanatomic mapping (EAM).

Methods and results: A unipolar/bipolar EAM of the all mappable coronary vein (CV) was performed in 52 consecutive patients with an indication to CRT implantation (mean age 75,1 ± 7,1). LAR was defined as the latest absolute unipolar intra-cardiac electrogram measured from the QRS onset. We defined 4 possible anatomical locations for the LAR in the standard LAO fluoroscopic projection (anterior, antero-lateral, infero-lateral, inferior), and 3 in the RAO projection (basal, median, apical). An average of 2.48 CV were mapped and CV angiography was required only in 23% cases, with a median fluoroscopy time of 4,03 min. Among our patients, 36 had a complete LBBB (LBBB group), 8 had a complete RBBB (RBBB group), and in 8 patient the QRS duration was less than 120 ms (IBBB group, including incomplete BBB and normal QRS).

No significant difference were found among different LAR locations in RAO projection and LAR was recorded in 3 cases in CV apical position.

Conclusions: The location of LAR in the CV showed a high variability between CRT patients. The presence of different QRS morphologies affected the location of LAR but it was not sufficient to predict its position. In LBBB patients LAR was frequently found in antero-lateral as well as infero-lateral CV, while in RBBB patients the distribution was more heterogeneous. Almost 6% of patients presented an apical location of LAR. These results support the need of EAM to guide LV lead to the LAR.