LP are frequently found in post-myocardial infarction scars and are useful ablation targets. The relative prevalence and characteristics of LP in patients with NICM is not well understood.
Thirty-three patients with structural heart disease (NICM, n = 16; ICM, n = 17) referred for catheter ablation of ventricular tachycardia were studied. Electroanatomic mapping was performed endocardially (n = 33) and epicardially (n = 19). The LP were defined as low voltage electrograms (<1.5 mV) with onset after the QRS interval. Very late potentials (vLP) were defined as electrograms with onset >100 ms after the QRS.
We sampled an average of 564 ± 449 points and 726 ± 483 points in the left ventricle endocardium and epicardium, respectively. Mean total low voltage area in patients with ICM was 101 ± 55 cm2 and 56 ± 33 cm2, endocardial and epicardial, respectively, compared with NICM of 55 ± 41 cm2 and 53 ± 28 cm2, respectively. Within the total low voltage area, vLP were observed more frequently in ICM than in NICM in endocardium (4.1 % vs. 1.3 % ; p = 0.0003) and epicardium (4.3 % vs. 2.1 % , p = 0.035). An LP-targeted ablation strategy was effective in ICM patients (82 % nonrecurrence at 12 ± 10 months of follow-up), whereas NICM patients had less favorable outcomes (50 % at 15 ± 13 months of follow-up).
The contribution of scar to the electrophysiological abnormalities targeted for ablation of unstable ventricular tachycardia differs between ICM and NICM. An approach incorporating LP ablation and pace-mapping had limited success in patients with NICM compared with ICM, and alternative ablation strategies should be considered.