Ablation: past, present, and future Dr Eric Prystowsky Director Clinical Electrophysiology Laboratory St Vincent Hospital Indianapolis Dr Mel Scheinman Professor of Cardiology University of California San Francisco

Ablation: past, present, and future In the late 70’s, the only option for refractory supraventricular tachycardia was surgical: cryosurgery or direct surgical division of the AV junction. This arrhythmia was most commonly atrial fibrillation refractory to drug therapy.

Ablation: past, present, and future Experimental techniques and their pitfalls at the time included both laser energy, which suffered from lack of precision and radiofrequency, which was poorly refined. Early studies led to AV junctional ablation using electrical energy discharges: Scheinman MM, Morady F, Hess DS, Gonzalez R. Catheter-induced ablation of the atrioventricular junction to control refractory supraventricular arrhythmias. JAMA 1982;248:851-5

Ablation: past, present, and future Before performing the first human procedure, studies in 10 dogs were successful, and under pathological examination, damage in the heart was limited to the region of the atrium and contiguous areas around the summit of the ventricular septum. No valvular or coronary lesions were seen. Energies levels in the range of joules were required to produce complete AV block.

Ablation: past, present, and future “[Radiofrequency] was the next best step in the sense that we could use titratable energy to selectively destroy accessory pathways without inordinate barotrauma, which was the big problem with DC shock.” Dr Mel Scheinman Professor of Cardiology University of California San Francisco

Ablation: past, present, and future Flexible catheter tips were developed to deliver the correct amount of radiofrequency energy, since small electrode tips were associated with failure in the earliest RF experiments. A 4 mm tip gives the largest amount of tissue damage for a given amount of delivered energy.

Ablation: past, present, and future “I think that the ordinary electrophysiologist is going to have to learn about complex mapping because I don't think you're going to be able to really intelligently handle some of the complex cases, the complex atrial tachycardias, atrial flutters without state-of- the-art multi-electrode mapping.” Dr Mel Scheinman Professor of Cardiology University of California San Francisco

Ablation: past, present, and future The adult electrophysiologist is now seeing very complicated arrhythmias including complex atrial flutter and incisional reentry. In order to understand these complicated circuits, an understanding of advanced imaging and complex mapping techniques is required. Future systems will likely involve noncontact mapping systems that give perfect endocardial mappings within a few beats.

Ablation: past, present, and future In flutter ablation, future catheter systems may involve only 1 burn across the isthmus through multiple electrodes, allowing for the creation of linear lesions. Preliminary work in the animal model incorporates the use of magnetic catheter systems. Additional experimental energy systems include microwave, ultrasound and cryoenergy.

Ablation: past, present, and future “Where [do] you think we should be heading with a fib? One concern is that it's the first time I've seen in our field people doing things without fundamental knowledge of why they're doing it… It seems to me we don't have a fundamental knowledge of why a particular line in a particular place makes any difference. I'm a little concerned about that.” Dr Eric Prystowsky Director, Clinical Electrophysiology Laboratory St Vincent Hospital Indianapolis

Ablation: past, present, and future Surgeons, in proof of principle, have shown that you can correct atrial fibrillation using a series of atrial lesions. The pulmonary vein area appears to be a critical area, although lesions here may lead to pulmonary stenosis, perforation, tamponade and stroke. Longterm follow-up suggests recurrence rates of up to 50%. Standardization of atrial fibrillation ablation may take decades.

Ablation: past, present, and future “I think molecular biology and genetics are going to have a tremendous impact and I see that as the next big step forward. We're all thinking of devices and making it better and cheaper and we're thinking about ablation tools, but I think that in the long haul it's going to be the molecular jocks that are going to point the way.” Dr Mel Scheinman Professor of Cardiology University of California San Francisco