Characterization of Sinus Node Activation by Noncontact Voltage Mapping

Abstract

Sinus node activation (SNA) was characterized in 34 patients (pt) by analyzing isopotential maps (IPM) and unipolar electrograms (UEG) recorded with noncontact array catheters. Initial activation IPM were defined as broad (>15mm diameter) or discrete (<15mm). UEG were analyzed for morphology and dV/dT (rapid v slow). In 13 pt initial SNA was localized to the superior and mid crista terminales (CT). IPM had a discrete initiation with a monophasic QS UEG with rapid dV/dT. Endocardial breakout site was at the initial activation site. In 21 pt initial SNA was at the SVC-RA junction superior to the CT. IPM had initial broad low voltage UEG with a biphasic slurred QS with slow initial dV/dT preceding rapid dV/dT. Endocardial breakout was remote from initial activation inferiorly along the CT. Breakout UEG had a rapid dV/dT. Isoproterenol increased dV/dT and activation shifted superiorly. SNA originates at 2 sites. A superior site is consistent with midmyocardial activation and anisotropic conduction to a distant endocardial breakout. Inferior CT sites are consistent with subendocardial activation. These findings may be important for SN ablation.