Relationship between magnetic resonance imaging scar characteristics assessment, inducible and spontaneous Ventricular tachycardia in post-infarct patients with a moderate left ventricular dysfunction
Corrélation anatomo-électrophysiologique entre la cicatrice d'infarctus du myocarde et la tachycardie ventriculaire chez les patients avec une FEVG > 35% : IRM et SVP
Résumé
BACKGROUND Inducibility of ventricular tachycardia (VT) at programmed ventricular stimulation (PVS) can identify patients with a substrate for VT in post myocardial infarction (MI). We previously demonstrated that a critical surface of intramural scar (>1.77 cm²) at the infarct border was related to VT in post MI patients with severe left ventricular (LV) dysfunction (≤35%). OBJECTIVES : We thought to evaluate whether infarct scar characteristics, especially intramural scar at the infarct border, assessed by cardiac magnetic resonance imaging (MRI), was predictive of inducible and spontaneous VT in patients with a remote MI and a LV ejection fraction (LVEF) superior to 35%. METHODS: We studied 27 patients with a remote MI (> 6 months) referred for PVS and MRI. LVEF and MI scar characteristics were evaluated with cine and gadolinium-enhanced MRI. Clinical and MRI characteristics were compared between patients with positive PVS and negative PVS. In a same way, characteristics were compared for spontaneous VT after a follow-up period. RESULTS: Patients with a positive PVS (30%) had a lower LVEF (40.3±3.5 vs. 48.9±8.2%, p=0.009), a larger infarct size (53.1±18.7 vs. 30.1±22.2 cm², p=0.002) with a greater transmural scar surface (24.5±11.3 vs. 6.8±10.7 cm²; p= 0.007). They had a greater intramural scar surface at the infarct border (6.8±3.5 vs. 2.1±2.3 cm²; p=0.003). In bivariate analysis (association with LVEF and others MI scar characteristics) only intramural scar surface remained associated with positive PVS (HR between 1.89 and 2.46, p<0.05). All patients with positive PVS had an intramural scar surface >1.77 cm² and none of patients with surface ≤ 1.77 cm² had inducible VT. Patient with intramural scar surface ≤ 1.77cm2 have a trend for a higher VT-free survival probability than patient with a surface >1.77 cm² (100% versus 81.2±9.8%, p=0.15, CONCLUSIONS: Intramural scar surface at the infarct border, as measured by cardiac MRI, is the best identifier of patients who have a substrate for VT. Further evaluation of this criterion as a predictor of spontaneous VT in post MI patients with LVEF > 35% is warranted.
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