705-3 Initial Experience with Left Ventricular Endocardial Catheter Manipulation Guided by Intracardiac Ultrasound Visualization: Improved Accuracy Over Fluoroscopic Imaging

The accuracy of radiofrequency ablation catheter tip localization with reference to surrounding anatomy was examined with both fluoroscopic and intracardiac long axis ultrasound imaging modalities in the canine left ventricle. 72 lesions (5–6 per dog) were created in 14 dogs with the delivery of 20–65 watts of radiofrequency power via 4–12mm tip catheters. Using a 9 RAO and 9 LAO mapping zone grid system, the relationship between fluoroscopic catheter tip position and underlying anatomy was established. The catheter tip location predicted by the fluoroscopic approach correlated precisely with the specific post-mortem lesion location in 52 (72%) of lesions. In 18 (25%), the lesions were found to be one zone (1–2cm) removed from the predicted site and were ≥2 zones removed in 2 (3%) lesions. locations predicted by longitudinally imaging intracardiac ultrasound as referenced to papillary muscles, the interventricular septum, and aortic and mitral annulae were significantly more accurate (chi2= 7.1, p = 0.029) than with fluoroscopy. In each of 20 sites examined, the lesion was within 5mm of that predicted by intracardiac ultrasound localization. This information demonstrates that ultrasound guidance during catheter mapping may be superior to that possible with fluoroscopy. This is of importance for the localization of tachycardia circuits, the investigational localization of radiofrequency lesions created with catheter techniques, and for return site energy delivery in cases of unstable or only marginally reproducible tachycardias