Concealed structural abnormalities in patients with apparently idiopathic arrhythmias of left ventricular origin: a magnetic resonance imaging study

Abstract

Purpose: Monomorphic Ventricular Arrhythmias of LV origin (VAs-LV) are usually associated with structural heart disease. However, routine diagnostic work-up occasionally does not identify any abnormality; in these patients, VAs-LV are referred as idiopathic. Aim of the present study was to investigate the value of cardiac MRI for the detection of concealed myocardial structural changes in pts with apparently idiopathic monomorphic VAs-LV. Methods: 39 consecutive pts (64% males, mean age 44±14 years) with monomorphic VAs-LV (i.e. frequent ventricular premature beats, recurrent non-sustained or sustained ventricular tachycardia with right bundle branch block morphology) and negative routine diagnostic work-up were included in the study. For comparison purposes, 61 consecutive pts (62% males, mean age 40±16 years) with monomorphic VAs of Right Ventricular Outflow Tract (RVOT) origin (i.e. with left bundle branch block morphology and inferior axis) and negative routine diagnostic work-up were also included. Routine diagnostic work-up included physical examination, blood tests, 12-lead ECG, transthoracic echocardiography and exercise stress testing; multi-slice computed tomography or invasive coronary angiography were also performed in selected pts. Both groups of pts underwent comprehensive cardiac MRI study, to assess LV and RV function, myocardial fatty infiltration, edema, and necrosis/fibrosis. Results: The 2 groups of pts did not differ significantly in age (p=0.22) and gender (p=0.86). No significant difference was observed between patients with VAs-LV and VAs-RVOT regarding LVEDV (78±18ml/m2 vs. 76±14ml/m2; p=0.56), RVEDV (71±15ml/m2 vs. 72±13ml/m2; p=0.72), LVEF (66±9% vs. 66±8%; p=0.93) and RVEF (69±7% vs. 69±7%; p=0.71). Cardiac MRI demonstrated myocardial structural abnormalities in 16 (41%) pts with VAs-LV vs. 5 (8%) pts with VAs-RVOT (p<0.001). At multivariate analysis, male gender (OR=11.6, 95% CI 2.1-65.0; p=0.005), family history of sudden cardiac death and/or cardiomyopathy (OR=5.2, 95% CI 1.3-20.4; p=0.019) and VAs-LV (OR 11.5, 99%CI 3.0-43.7; p<0.001) were independently related to the presence of myocardial structural abnormalities. Conclusions: Cardiac MRI detects myocardial structural changes in a non-negligible proportion of pts with apparently idiopathic monomorphic VAs-LV. Accordingly, cardiac MRI should be implemented in the routine diagnostic work-up of these pts, in order to better characterize the pathogenic substrate of VAs and to better tailor specific therapy.