Scar Extension Measured by Magnetic Resonance-Based Signal Intensity Mapping Predicts Ventricular Tachycardia Recurrence After Substrate Ablation in Patients With Previous Myocardial Infarction.

Objectives: The aim of this study was to determine if noninvasive measurement of scar by contrast-enhanced magnetic resonance imaging (MRI)-based signal intensity (SI) mapping predicts ventricular tachycardia (VT) recurrence after endocardial ablation.

Background: Scar extension on voltage mapping predicts VT recurrence after ablation procedures.

Methods: A total of 46 consecutive patients with previous myocardial infarction (87% men, mean age 68 ± 9 years, mean left ventricular ejection fraction 36 ± 10%) who underwent VT substrate ablation before the implantation of a cardioverter-defibrillator were included. Before ablation, contrast-enhanced MRI was performed, and areas of endocardial and epicardial scarring and heterogeneous tissue were measured; averaged subendocardial and subepicardial signal intensities were projected onto 3-dimensional endocardial and epicardial shells in which dense scar, heterogeneous tissue, and normal tissue were differentiated.

Results: During a mean follow-up period of 32 ± 24 months 17 patients (37%) had VT recurrence. Patients with recurrence had larger scar and heterogeneous tissue areas on SI maps in both endocardium (81 ± 27 cm vs. 48 ± 21 cm [p = 0.001] and 53 ± 21 cm vs. 30 ± 15 cm [p = 0.001], respectively) and epicardium (76 ± 28 cm vs. 51 ± 29 cm [p = 0.032] and 59 ± 25 cm vs. 37 ± 19 cm [p = 0.008]). In the multivariate analysis, MRI endocardial scar extension was the only independent predictor of VT recurrence (hazard ratio: 1.310 [per 10 cm]; 95% confidence interval: 1.051 to 1.632; p = 0.034). Freedom from VT recurrence was higher in patients with small endocardial scars by MRI (<65 cm) than in those with larger scars (≥65 cm) (85% vs. 20%, log-rank p = 0.018).

Conclusions: Pre-procedure endocardial scar extension assessment by contrast-enhanced MRI predicts VT recurrence after endocardial substrate ablation. This information may be useful to select patients for ablation procedures.