Abstract 4138424: Ring of Power: Unraveling a Rare Diagnosis in a Young Male with Palpitations

Case Description: A 36-year-old male presented for an outpatient treadmill ECG stress test for further evaluation of palpitations exacerbated by exercise. He had no ischemic ECG changes, but developed a sustained episode of polymorphic VT at 13 minutes (Figure 1a). The test was stopped and the VT self-terminated after 43 seconds. The patient was admitted for further workup. Lab workup was unremarkable; baseline ECG demonstrated no ST-T wave changes and displayed normal QT and QRS duration. TTE showed mild biventricular dysfunction. Coronary CT angiogram showed type 3 subtype of Vieussens’ arterial ring (VAR), with an absent left main and super-dominant RCA supplying both LAD and LCx. FFR-CT showed non-hemodynamically significant stenosis in the mid-distal LAD (Figure 1b). Left heart catheterization confirmed presence of VAR and mild diffuse disease in a small-caliber mid-distal LAD (Figures 1c&d). No malignant course or dynamic coronary compression was present. Cardiac MRI revealed normal biventricular function and the absence of late gadolinium enhancement. An exercise stress test, now with myocardial perfusion, was performed and was entirely normal without evidence of myocardial ischemia. Genetic testing for catecholaminergic polymorphic VT was negative. After a multidisciplinary discussion, it was decided not to pursue CABG in the absence of demonstrable ischemia at peak exercise. He underwent an ICD placement for secondary prevention and was discharged on beta blockers. Discussion: Three distinct subtypes of VAR have been described, with type 3 being the rarest. The coronary anomaly was first described by Raymond de Vieussens in 1706, and represents an embryologic remnant of the conotruncal circle. It may be diagnosed incidentally in asymptomatic patients or present with angina especially if underlying CAD, aneurysms or fistulae are present. We report the first case of exercise-induced polymorphic VT in a type 3 VAR patient, theorizing that intermittent myocardial ischemia at peak exercise may induce VT in these patients. Surgical revascularization may be considered if myocardial ischemia is demonstrated on stress testing, although its benefit in patients without such evidence of ischemia is unknown.