Recently, we introduced coronary venous electroanatomical mapping as a tool to assess LV electrical activation at the time of CRT implantation in patients with LBBB. However, recent studies have suggested that CRT may be beneficial in a subset of IVCD patients with evidence of LV activation delay. The reduced benefit of CRT observed in this subgroup of patients has led international guidelines to assign a lower level of recommendation to CRT in patients with IVCD. This may explain why, in contrast to patients with LBBB, patients with IVCD show a variable response to CRT. Non-specific intraventricular conduction delay (IVCD), on the other hand, is considered a more heterogeneous group of conduction disorders exhibiting a more variable pattern of ventricular electrical activation. Left bundle branch block (LBBB) is typically associated with early septal activation and delayed activation of the LV lateral wall. The supposed mechanism of the benefit of cardiac resynchronisation therapy (CRT) is that delayed activation of the left ventricular (LV) lateral wall causes mechanical dysfunction, which can be reverted by paced pre-excitation of this delayed LV region. QRS characteristics on the ECG seem unable to identify delayed LV lateral wall activation in this subgroup of patients. ConclusionĬoronary venous electroanatomical mapping can be used at the time of CRT implantation to determine the presence of delayed LV lateral wall activation in patients with IVCD.
QRS duration, and prevalence of QRS fragmentation and left/right axis deviation, and left anterior/posterior fascicular block did not differ between patients with and without delayed LV lateral wall activation. In these patients, the latest activated region was consistently located on the basal lateral wall. Resultsĭelayed LV lateral wall activation occurred in 12/23 patients (maximal LVLW-AT = 133 ± 20 ms ). QRS morphology, duration, fragmentation, axis deviation, and left anterior/posterior fascicular block were assessed on baseline ECGs. LV lateral wall activation was considered delayed if maximal activation time measured at the LV lateral wall (LVLW-AT) exceeded 75 % of the QRS duration. Electrical activation time was measured in milliseconds from QRS onset and expressed as percentage of QRS duration. Twenty-three consecutive CRT candidates with IVCD underwent intra-procedural coronary venous electroanatomical mapping using EnSite NavX. We assessed LV lateral wall activation in a cohort of CRT candidates with IVCD using coronary venous electroanatomical mapping, and investigated whether baseline QRS characteristics on the ECG can identify delayed LV lateral wall activation in this group of patients. Although typically associated with left bundle branch block, delayed LV lateral wall activation may also be present in patients with non-specific intraventricular conduction delay (IVCD). Delayed left ventricular (LV) lateral wall activation is considered the electrical substrate that characterises patients suitable for cardiac resynchronisation therapy (CRT).