The identification of Mahaim spiked potentials may be the optimal method to permit their successful ablation. Detailed electrophysiologic assessment is indispensable for successful ablation of tachycardias associated with Mahaim fibers because tachycardias unassociated with Mahaim fibers can occur despite complete elimination of the Mahaim fiber.

Slow AV nodal pathway ablation using RF is highly effective for patients with refractory AV nodal reentrant tachycardia (AVNRT). We report three catheter ablation cases using RF current in patients associated with persistent left superior vena cava (PLSVC). Three patients with drug refractory AVNRT of common variety were involved in this study. An electrode catheter introduced through the left subclavian vein inserted directly into the coronary sinus, a typical anatomical finding of PLSVC. The ablation procedure was initially performed at the posteroinferior region of Koch's triangle. A slow pathway potential could not be found from that area; nonsustained junctional tachycardia (NSJT) did not occur during the delivery of RF current; there was failure to eliminate slow AV nodal pathway conduction. The catheter then was moved into the bed of the proximal portion of the markedly enlarged coronary sinus. A slow AV nodal pathway potential was recorded through the ablation catheter, and the delivery of RF current caused NSJT in two patients. Complete elimination of slow AV nodal pathway conduction was accomplished in these two patients by this method. No adverse effects were provoked by this procedure. Catheter ablation of the slow AV nodal pathway guided by a slow pathway potential and the appearance of NSJT was feasible and safe in the area of the coronary sinus ostium in patients associated with PLSVC.

Left atrial linear lesions affect right atrial endocardial activation, whereas right atrial lesions do not affect left atrial activation in a canine model of atrial fibrillation. These findings suggest that the left atrium is the driver during chronic atrial fibrillation in this animal model and may explain the limited success of right atrial ablation alone in human atrial fibrillation.

Our current understanding is that atrial fibrillation (AF) is initiated most often by a focal trigger from the orifice of or within one of the pulmonary veins. Though mapping and ablation of these triggers appears to be curative in most patients with paroxysmal AF, there are a number of limitations to ablating focal triggers via mapping and ablating the earliest site of activation with a "point" radiofrequency lesion. One way to circumvent thesen limitations is an anatomically-guided ablative approach. By electrically isolating one or more pulmonary veins from the left atrium with a circumferential lesion, firing from within those veins would be unable to reach the body of the atrium, and thus could not trigger atrial fibrillation. We have developed a novel over-the-wire catheter design which integrates a cylindrical ultrasound transducer within a saline filled balloon, termed TTB-USA (through-the-balloon ultrasound ablation) in order to produce narrow circumferential zones of hyperthermic tissue death at the pulmonary vein ostia. Animal studies show great promise, and clinical trials will begin soon.

Long linear lesions can be safely and effectively performed in the canine left atrium, using a tip-deflectable multielectrode catheter. Intracardiac echocardiography may be helpful for positioning the ablation catheter in some parts of the left atrium, and preablation parameters, especially a nontraumatic low-power RF application, are able to predict ultimate lesion creation with high accuracy.

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This novel automatic 62-lead QRST subtraction algorithm enables discrete isolation of T-U wave obscured ectopic atrial activity on the surface ECG while retaining the intricate spatial detail in P wave morphology. Future clinical application of the algorithm may enable improved ECG localization of focal triggers of paroxysmal atrial fibrillation, atrial tachycardia, and the atrial insertion of accessory pathways.