ISCHEMIC OR NON-ISCHEMIC MYOCARDIAL SCAR QUANTIFICATION PREDICTS FUTURE ARRHYTHMIC EVENTS IN CANDIDATES FOR PRIMARY PREVENTION ICD

Abstract

Background: Patients with ischemic cardiomyopathy (ICM) and non-ischemic cardiomyopathy (NICM) are at risk of sudden cardiac arrest (SCA). Delayed enhancement (DE) MRI may identify sub-populations at higher risk of arrhythmic events. This study evaluates the role of DE MRI scar quantification for the prediction of future events in both ICM and NICM populations. Methods: 125 consecutive patients referred for cardiac MRI to determine ICD eligibility (ICM = 61 pts, NICM =64 pts) were enrolled. DE MRI was done in a standard fashion and signal threshold analysis blindly performed. Total scar was defined as any signal ≥2SD above normal reference myocardium, while the difference between 3 and 5SD thresholds being defined as “borderzone”. All patients were prospectively followed for the primary combined endpoint of appropriate ICD therapy or SCA. A composite secondary endpoint of major adverse events (SCA, appropriate ICD therapy and all-cause mortality) was also evaluated. Results: The mean age and EF was 61.4±11.2 yo and 26.5±7.5% (range 8.9 to 40%), respectively. A total of 76 pts received an ICD. During a median follow-up of 412±191days, 16 patients (13%) had a primary endpoint (15 ICD therapies and 1 aborted SCA). An additional 6 patients had death from any cause contributing to the secondary endpoint. The mean total scar mass was significantly higher in pts with a primary outcome (65.1±27.8 g vs. 31.3±18.7 g, p<0.001) or secondary outcome (54.5±29.6 g vs. 31.6±19.1 g, p<0.001). Similarly, the borderzone mass was higher in pts with a primary event (25.3±10.8g vs. 18.3±9.8g, p=0.009) or secondary event (23.7±10.5 g vs. 18.2±9.9g p=0.02). ROC analysis revealed that total scar mass had the greatest AUC values of 0.85 (0.73~0.96, p<0.001) and 0.74 (0.63~0.86, P<0.001) for primary and secondary events, respectively. Only total scar mass remained predictive of the primary or secondary outcome in multivariate analysis. In subgroup analysis of both ICM and NICM patients, total scar mass remained the sole predictor of adverse events. Conclusion: Total scar mass predicts arrhythmic events in patients being considered for primary prevention ICD irrespective of ischemic or nonischemic etiology.