A 54-year-old man with new-onset ventricular fibrillation.

CLINICAL INTRODUCTION: A 54-year-old man without significant medical history presented with sudden-onset chest discomfort and multiple episodes of ventricular fibrillation requiring external defibrillation and cardiopulmonary resuscitation. Coronary angiography ruled out significant artery stenosis. Both ventriculography and echocardiography revealed decreased left ventricular ejection fraction (25%). On examination, he was haemodynamically stable. The lungs were clear to auscultation and there was no jugular venous dilation. The cardiac examination revealed a regular rate and rhythm without murmur. Cardiac magnetic resonance (CMR) and 18F-2-fluoro-2-deoxyglucose positron emission tomography (FDG-PET) images were shown (figure 1).heartjnl;103/23/1922/F1F1F1Figure 1Cardiac magnetic resonance with a T1-weighted inversion recovery image (A) and 18F-2-fluoro-2-deoxyglucose positron emission tomography (B) in a 54-year-old man with new-onset ventricular fibrillation.

QUESTION: Which of the following would be the next best step?Implantable loop recorderElectrophysiological testing for radiofrequency catheter ablationEndomyocardial biopsyGenetic testing.