The morphology of unipolar potentials predicts the depth of activation foci

Abstract

Background: The depth of an arrhythmic focus is a major determinant of ablation procedural outcome. This study examined the relationship between the morphology of unipolar potentials and the depth and horizontal distance to activation foci. Methods: Unipolar left ventricular epicardial mapping was performed in 7 open-chest dogs, using silicon sheets with 12 unipolar electrodes 1 mm apart, during bipolar pacing from an octopolar plunge electrode with 1-mm interelectrode spacing. The morphology of the unipolar electrograms was classified as QS, rS, qrS, qRS, rsr’S, or rsR’S. Results: A QS complex was recorded immediately above a subepicardial or mid-myocardial pacing site. An rS complex was recorded away from a subepicardial pacing site. A positive wave originating from a down sloping deflection (R-in-QR) such as r wave in qrS, R wave in qRS, r′ wave in rsr’S or R′ wave in rsR’S complexes was observed when the recording was above a deep myocardial pacing site or away from a mid-myocardial pacing site. The amplitude of negative wave immediately before R-in-QR (Q-in-QR) was inversely correlated with the horizontal (R=−0.40; P<0.0001) and linear (R=−0.22; P=0.0006) distance to the pacing site, and the amplitude of R-in-QR was positively correlated with the horizontal (R=0.25; P=0.0001) and linear (R=0.29; P<0.0001) distance to the pacing site. The amplitude of the initial r wave was not correlated with the depth or horizontal and linear distance to the pacing site. Conclusion: The morphology of unipolar electrograms predicted the horizontal distance and the depth of nearby foci of activation.

Keywords

• Epicardial mapping
• Epicardial electrogram
• Unipolar potential
• Intramyocardial pacing
• Ventricular pacing
• Catheter ablation
• Ventricular arrhythmia