Right ventricular MR abnormalities in myotonic dystrophy and relationship with intracardiac electrophysiologic test findings: initial results

Abstract

Purpose: To prospectively determine whether a relationship exists between magnetic resonance (MR) imaging abnormalities of the right ventricle (RV) and intracardiac electrophysiologic (EP) test results in patients with myotonic dystrophy.

Materials and methods: Conventional T1-weighted single-shot black-blood fast spin-echo and gradient-echo MR imaging of the heart was prospectively performed in 32 patients with myotonic dystrophy who required EP testing. Patients were divided into two groups according to EP test results: (a) inducible (n = 15), indicating inducible ventricular tachyarrhythmias, and (b) noninducible (n = 17). Morphologic and functional MR data were analyzed by two independent investigators. Nonparametric statistical methods and kappa statistics were used.

Results: No morphologic or functional abnormalities of the RV wall were observed in noninducible patients. Increased signal intensity of the RV wall, indicative of fatty replacement, was identified in 13 inducible patients. Myocardial thinning of the RV was observed in six inducible patients. An overlap of morphologically abnormal areas and areas of hypo- or dyskinesis were present in 11 inducible patients. RV outflow tract diameter was larger and RV ejection fraction was smaller in inducible patients than in noninducible patients, although differences were not significant. Interobserver agreement for MR findings was good (increased signal intensity: kappa = 0.87, P >.30 [pairwise Wilcoxon signed rank test]; myocardial thinning: kappa = 0.87, P >.30; hypo- or dyskinesis: kappa = 1.00, P >.99). There was a strong relationship between MR abnormalities and inducibility during EP testing (increased signal intensity, P <.001; myocardial thinning, P <.01; hypo- or dyskinesis, P <.01).

Conclusion: The relationship between MR morphologic and functional RV abnormalities and EP testing suggests potential for the use of MR imaging as a noninvasive method to estimate the individual risk of arrhythmia in patients with myotonic dystrophy.