Noncontact Voltage Maps of SVC Myocardial Segments and RA Connections

Abstract

Myocardial segments (MYO) can extend into the superior vena cava (SVC) from the RA. To characterize entry and exit sites and course of MYO, the SVC and SVC-RA junction were mapped with noncontact multielectrode array catheters in 9 patients (pt) during sinus rhythm and RA pacing. Discrete MYO were found in all pt. Multiple segments with RA connections were identified in 5 pt: 3 had posteromedial and anterolateral connections, 1 had anterior, lateral and posteromedial connections, 1 had posterior and medial connections. In 4 pt activation conducted into the SVC along the posterior segment and out the SVC along a second segment. A single discrete posteromedial segment was identified in 4 pt. MYO course was straight (n = 6) or spiral around the SVC (n = 3); in 4 pt MYO branched distally. Segments extended 3-6cm into SVC. No pt had a completely circumferential segment. In 3 pt tachycardia originated in an anterior segment 1-2cm into SVC. SVC MYO have complex anatomy often with multiple segments and RA connections. These can be sites of reentrant circuits and ectopic foci driving atrial tachycardia.