Relation between body surface mapping and endocardial spread of ventricular activation in postinfarction heart

Body Surface Mapping and Endocardial Activation Patterns. Introduction: Bod y surface mapping (BSM) can be used to identify the site of earliest endoca rdial activation of ventricular tachycardias (VTs). The multielectrode QRS morphology during VT is determined by both the site of earliest activation and the subsequent spread of electrical activation through the ventricles. This study investigated the relationship between the site of earliest endoc ardial activation, endocardial spread of activation, and the morphology of the multielectrode surface map in patients with remote myocardial infarctio n. Methods and Results: In 14 patients with VT late (8.2 +/-5.2 years) after m yocardial infarction, BSM and simultaneous left ventricular 64-site basket endocardial mapping was performed during a total of 17 monomorphic VTs. In addition, multisite pacing by sequential use of the 64 basket electrodes wa s performed in 9 patients. BSM and basket mapping revealed the same endocar dial breakthrough sites in 8 (47%) of 17 VTs and 189 (59%) of 322 pacing si tes; adjacent sites were found in 2 (12%) of 17 VTs and 36 (11%) of 322 pac ing sites. Large zones of conduction block explained the mismatch in locali zation in 2 (12%) of 17 VTs and 52 (16%) of 322 pacing sites. Regional diff erences in endocardial electrogram amplitudes were found as a cause for dis similarity in 3 (18%) of 17 VTs and 73 (23%) of 322 pacing sites. Multiple endocardial breakthrough sites were found in 1 (6%) of 17 VTs and 8 (2%) of 322 pacing sites Finally, an epicardial exit site was suggested in 3 (18%) of 17 VTs as an explanation for mismatch, as no early endocardial activity could be recorded. Conclusion: Zones of conduction block, regional differences in signal ampli tude, and multiple endocardial breakthrough sites are frequent causes for m ismatch between BSM and basket catheter activation mapping.