Background: Intramural scar is a potential source for ventricular arrhythmias in patients with non-ischemic cardiomyopathy. However, its localization may be challenging because endocardial and epicardial voltage amplitudes are often normal. We hypothesized that intramural non-uniform anisotropy with zigzag conduction produces endocardial electrograms with multiple components that may serve as surrogates for intramural scar.
Objective: Compare the accuracy of voltage amplitude and electrogram characteristics in identifying intramural scar.
Methods: In a swine model of healed circumflex infarction that produces intramural scar and preserved endocardial and epicardial layers (n=5), mapping of the endocardium and epicardium was performed with Carto 3^® and a multielectrode catheter with 48 electrodes (Octaray™, Biosense Webster) during atrial pacing. Voltage amplitude, electrogram characteristics and activation maps were compared to cardiac magnetic resonance imaging with late gadolinium enhancement (LGE).
Results: Bipolar and unipolar voltage amplitudes across the intramural scar were relatively normal (Endocardial:1.36±0.32mV, 7.24±1.42mV; Epicardial: 1.21±0.30mV, 6.15±1.02mV) despite a nearly transmural scar with preserved endocardial and epicardial layers seen on LGE (Figure). Endocardial electrograms across from the corresponding LGE had multicomponent potentials (>5) during or after the QRS (72.2±13.2%). Late activation approximated the intramural scar location.
Conclusion: Multicomponent electrograms of normal voltage amplitude may be more predictive of intramural scar than bipolar or unipolar voltage amplitude.