We have previously demonstrated that the spatial characteristics (intramural and epicardial components) of MI scar predicts the occurence of monomorphic ventricular tachycardia (MVT) after a myocardial infarction (MI). We studied whether MI scar characteristics, as assessed by magnetic resonance imaging (MRI), was related to the minimum cycle lenght(mCL) of MVT.

We studied 50 patients (43 men, mean age 60±13 years) with previous MI, cardiac MRI study, primary (n=12) or secondary prevention indication of implantable cardiac defibrillator (ICD) and who experienced MVT. Delayed contrast enhancement (DCE) was used to delineate post-MI scars.

MVT occurred 15±9 years after MI and the mCL was 303±49ms. MRI showed areas with intramural and/or epicardial scar (adjacent to areas showing endocardial or transmural scar) in all patient. Patients were classified depending on the median of the mCL (300ms). There were no statistical differences between the 2 groups for: gender, medication, indication of ICD, history of coronary artery revascularization, infarct location and for the following MRI parameters: left ventricular (LV) ejection fraction, LV end-diastolic volume, LV mass, total myocardial surface, total MI scar surface, transmural, endocardial or epicardial MI scar surface. In patients with a mCL>300ms, there was a trend for older age at first MVT episode (64±2 vs. 57±3 year; p=0.06) and a greater intramural scar surface (5.8±3.7 vs. 2.9±1.6cm²;p=0.002). Age (r=0.32; p=0.02) and intramural scar surface (r=0.47; p<0.001)were associated with the mCL. After multiple linear regression, age and intramural scar surface remained significantly associated with the mCL (respectively: P=1.3±0.6; p=0.03 and P=6.5±2; p=0.003).

Our study suggests that the mCL of MVT may be related to age and to the intramural MI scar surface at the infarct border (figure next page).