Why Is Catheter Ablation Less Successful than Surgery for Treating Ventricular Tachycardia that Results from Coronary Artery Disease?

Abstract

Nearly 80% of patients with coronary artery disease who have map-directed surgery for control of ventricular tachycardias require no drug therapy to prevent recurrences, while fewer than 50% of patients undergoing catheter ablation have similar outcomes. Catheter ablation will fail if arrhythmogenic sites are incompletely ablated by lesions that are too small or too far away from the reentrant pathway or if all arrhythmogenic sites are not identified. The underlying assumptions used to guide site selection are that: (a) ventricular tachycardias arise from reentrant mechanisms; (b) monomorphic ventricular tachycardias with similar QRS morphologies arise from the same pathway; (c) the ventricular tachycardia initiated during the procedure represents the patient's spontaneous arrhythmia; (d) the endocardial site that should be ablated can be identified from cardiac activation maps produced during induced ventricular tachycardia or from ancillary techniques; and (e) the patient has only one or two reentrant pathways. Relying on incorrect assumptions may account for the difference in success rates. Patients may have similar appearing ventricular tachycardias that arise from different pathways, and the entire thin layer of viable tissue between the infarct and the endocardium may contain many reentrant pathways. Some ventricular tachycardias may arise from the myocardium away from the endocardium, while others may arise from the epicardium. Small lesions may not be large enough to eliminate all possible reentrant pathways. Catheter ablation may be less successful because the lesions are inadequate, the assumptions guiding the selection of arrhythmogenic tissue are incorrect, or all arrhythmogenic sites are not identified. The primary reason catheter ablation is less successful than surgery in the treatment of ventricular tachycardias is that catheter ablation does not ablate as much tissue as is removed by surgery. The success rate of catheter ablation probably can be improved if the amount of tissue ablated is increased.

Electrocardiographic Recognition of the Epicardial Origin of Ventricular Tachycardias

“…One proposed explanation is that the reentry circuits may be located deep in the subendocardium or in the epicardium, making them inaccessible to current ablation techniques. 7,8 Epicardial mapping of arrhythmia foci or circuits has been attempted in open chest surgery 9,10 and with RF ablation catheters. 11,12 These studies suggest that the slow conduction zone may be located subepicardially in up to 33% of patients.…”

Radiofrequency Catheter Ablation of Ventricular Tachycardia from the Anterobasal Left Ventricle.

“…In patients with coronary artery disease, success rates are between 50 % and 70 %, both for DC fulguration and RF catheter ablation, [16][17][18] despite the introduction of various mapping criteria such as pace mapping, 19,20) earliest endocardial activation, 21) entrainment with concealed fusion, 22,23) and analysis of the postpacing interval after pacing from the mapping catheter. 24) Potential reasons for this include insufficient lesion size generated by RF current 24,25) or an even more complex arrhythmogenic substrate than described by currently accepted mapping criteria. However, the mechanism of VT in other cardiac diseases is not always reentry but may involve enhanced automaticity as well as triggered activity.…”

Alternation in the Flutter Wave Morphology During Radiofrequency Catheter Ablation for Common Atrial Flutter

“…15,16 Blanchard et al also described that catheter ablation for reentrant ventricular tachycardia might appear to fail, even if it prevented one reentrant pathway from recurring, if another reentrant pathway was still present that produced tachycardia with a similar electrocardiographic axis. 17 Cauchemez et al described that in most patients there is no transverse activation going through the posterior intercaval right atrial wall, 4 and Olgin et al 18 and Nakagawa et al 19 also described that the borders of the this area of conduction block were the crista terminalis and the eustachian ridge. Our cases seem to be exceptional ones in terms of this conduction block created in the right atrium.…”