Infarct morphology identifies patients with substrate for sustained ventricular tachycardia

Objectives

We sought to evaluate whether infarct size characterization by cardiac magnetic resonance imaging (MRI) is a better predictor of inducible ventricular tachycardia (VT) than left ventricular ejection fraction (LVEF).

Background

Inducibility of VT at electrophysiologic study (EPS) and low LVEF can identify patients with a substrate for VT. Magnetic resonance imaging has been shown to identify, with high precision, areas of myocardial infarction and may therefore be a better tool to evaluate for a substrate for VT.

Methods

We studied 48 patients with known coronary artery disease who were referred for EPS using cine and gadolinium-enhanced MRI. Wall motion and infarct characteristics were determined blindly and compared among patients with no inducible ventricular arrhythmias (n = 21), those with inducible monomorphic VT (MVT, n = 18), and those with either inducible polymorphic VT or ventricular fibrillation (n = 9).

Results

Patients with MVT had larger infarcts than patients who did not have inducible arrhythmias (mass: 49 ± 5 g [SE] vs. 28 ± 5 g, p < 0.005; surface area: 172 ± 15 cm²vs. 93 ± 14 cm², p < 0.0005). Patients with polymorphic VT/fibrillation had intermediate values (mass: 36 ± 7 g; surface area: 115 ± 22 cm²). Ejection fraction was inversely related to infarct mass and surface area, with R²values ranging from 0.21 to 0.27. Logistic regression and receiver-operating characteristic analysis demonstrated that infarct mass and surface area were better predictors of inducibility of MVT than LVEF.

Conclusions

Infarct surface area and mass, as measured by cardiac MRI, are better identifiers of patients who have a substrate for MVT than LVEF. Further evaluation of infarct size characterization by cardiac MRI as a predictor of sudden cardiac death is warranted.