Indices of bipolar complex fractionated atrial electrograms correlate poorly with each other and atrial fibrillation substrate complexity

BACKGROUND: The pathophysiological relevance of complex fractionated atrial electrograms (CFAE) in atrial fibrillation (AF) remains poorly understood.

OBJECTIVE: The aim of this study was to comprehensively investigate how bipolar CFAE correlates with unipolar electrogram fractionation and the underlying electrophysiological substrate of AF.

METHODS: Ten-second unipolar AF electrograms were recorded using a high-density electrode from the left atrium of 20 patients with AF (10 with persistent AF and 10 with paroxysmal AF) undergoing cardiac surgery. Semiautomated bipolar CFAE algorithms: complex fractionated electrogram-mean, interval confidence interval, continuous electrical activity, average complex interval, and shortest complex interval were evaluated against AF substrate complexity measures following fibrillation wave reconstruction derived from local unipolar activation time. The effect of interelectrode spacing and electrode orientation on bipolar CFAE was also examined.

RESULTS: All 5 semiautomated bipolar CFAE algorithms showed poor correlation with each other and AF substrate complexity measures (conduction velocity, number of waves or breakthroughs per AF cycle, and electrical dissociation). Bipolar CFAE also correlated poorly with fractionation index derived from unipolar electrograms. Increased interelectrode spacing resulted in an increase in bipolar CFAE detected except for the interval confidence interval algorithm. CFAE appears unaffected by bipolar electrode orientation (vertical vs horizontal). By contrast, unipolar fractionation index correlated well with AF substrate complexity measures and can be regarded as a marker for conduction block.

CONCLUSION: The lack of pathophysiological relevance of bipolar CFAE analysis may in part contribute to the divergent and limited success rates of catheter ablation strategies targeting CFAE.