Regional Myocardial Blood Flow Possible Mechanism for Late Electrophysiological Outcome

Background We postulated that the late electrophysiological effects of radiofrequency (RF) ablation may be related to microvascular injury extending beyond the region of acute coagulation necrosis. Methods and Results Eighteen RF lesions created in the left anterior descending coronary artery (LAD) perfusion bed of seven open chest anesthetized dogs were studied. The ablation electrode and surrounding myocardium were imaged using high-resolution two-dimensional echocardiography at x 4 magnification. After 60 seconds of RF delivery, sonicated albumin microbubbles (mean size, 4.3 ,um) were injected into the LAD to measure regional myocardial perfusion, and time-intensity plots were generated from simultaneously acquired two-dimensional echocardiography images. The regions with persistent contrast effect on two-dimensional echocardiography were larger than the pathological lesions (mean cross-sectional area, 48.3+6.3 versus 19.3±4.7 mm2, respectively; P<.0001). The mean contrast transit rate in the area corresponding to the