Catheter Ablation of Atrial Fibrillation: The Search for Substrate-Driven End Points

Indications for catheter ablation of atrial fibrillation (AF) have expanded to include increasingly complex cases, such as long-standing persistent AF and structural heart disease. Although pulmonary vein isolation remains essential for most ablation procedures, the role of substrate modification has taken on increasing importance. Despite the various ablation strategies available, single-procedure efficacy remains suboptimal among patients with structural heart disease or long-standing persistent AF, where recurrence rates may exceed 50% after a single procedure. These high rates of AF recurrence support the notion that currently available procedural end points are ineffective in identifying which patients are most likely to benefit from substrate modification and defining when that substrate has been sufficiently modified such that additional ablation is unnecessary. In order to improve outcomes, the next generation of procedural end points should seek to define specific properties of the underlying atrial electrical substrate and characterize the impact of catheter ablation on those electrophysiologic properties. The use of substrate-driven end points would be a major step in the process of moving from empiric ablation lesions to a customized ablation strategy based on atrial physiology. In this article, we review current approaches to catheter ablation of AF and discuss specific procedural end points as they pertain to each ablation strategy. We also provide a paradigm for the future development of novel substrate-driven procedural end points.