B-PO03-087 ATRIAL UNIPOLAR VOLTAGE MAPPING FOR DETECTION OF INTRAMURAL ABLATION GAPS

Abstract

Endocardial bipolar voltage is primarily influenced by superficial muscle layers. Thus, endocardial scar with surviving intramural/epicardial layers may exhibit low bipolar voltage. Alternatively, intramural/epicardial scar with preserved endocardium may exhibit normal voltage. To examine the value of unipolar voltage for assessing atrial tissue. In a chronic swine model of transcaval ablation line with intentional gap (7.9-14.8mm), the RA was mapped after a survival period of 6 weeks using a multielectrode catheter (Pentaray, Biosense Webster). Unipolar and bipolar voltage maps were compared with histopathology. In 10 swine, the transcaval ablation line was transmural in 4 and non-transmural in 6. Four gaps exhibited endocardial scar with preserved mid-myocardial and epicardial layers; 1 gap showed preserved endocardium with mid-myocardial scar, and 1 gap showed a fully preserved atrial wall. Bipolar voltage (using a 0.50mV cutoff) performed well for detecting all endocardial gaps (0.64mV, IQR: 0.36-1.52, PPV=100%) but failed to detect intramural gaps (0.28mV, IQR:0.13-0.52, p=0.004; PPV=0%;). Lowering the bipolar voltage cutoff to 0.2mV did not significantly improve its sensitivity to detect intramural gaps (PPV=25%). In contrast, unipolar voltage was higher in sites of intramural gaps (1.37mV, IQR:1.12-1.93) compared to regions of transmural scar (0.74mV, IQR:0.58-0.94, p<0.001; PPV=100%) without false positive gap detection (NPV=100%); Figure. Unipolar voltage mapping may be useful for detecting intramural surviving muscle. The clinical utility and specific cutoff values require further investigation.