Scar progression in patients with nonischemic cardiomyopathy and ventricular arrhythmias

Background Disease progression in patients with nonischemic cardiomyopathy (NICM) is poorly understood. Objective To assess left ventricular (LV) scar progression and dilatation by using endocardial electroanatomic mapping. Methods We studied 13 patients with NICM and recurrent ventricular tachycardia. Two detailed sinus rhythm endocardial voltage maps (265 ± 122 points/map) were obtained after a mean of 32 months (range 9-77 months). The scar area, defined by low bipolar (BI; <1.5 mV) and unipolar (UNI; <8.3 mV) endocardial voltage, and the LV volume were measured and compared. A scar difference of >6% of the LV surface and an increase in LV volume of >20 mL were considered beyond measurement error. Results Six (46%) patients had an increase in scar area beyond boundaries of prior ablation. Five patients had an increase in UNI and 1 patient had an increase in both BI and UNI areas. The increase in BI area represented 16% and the increase in UNI area represented 6.5%-46.2% of the LV surface. A significant decrease in LV ejection fraction was found only in patients with scar progression (from 39% ± 8% to 32% ± 8%; P =.003). LV dilation (LV volume increase ranging between 9% and 23%) was noted in 3 patients, all of whom had scar progression. Conclusions Progressive scarring with an increase in the area of UNI and less commonly BI electrogram abnormality is seen in 46% of the patients with NICM and ventricular tachycardia and is associated with LV dilatation and decrease in LV ejection fraction. The prominent UNI abnormality suggests predominantly midmyocardial or epicardial scarring.