PE-452787-1 THE RELATIONSHIP BETWEEN VENTILATORY ANAEROBIC THRESHOLD AND ARRHYTHMIA ONSET IN PATIENTS WITH CATECHOLAMINERGIC VENTRICULAR TACHYCARDIA

Abstract

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a genetic disease associated with malignant ventricular arrhythmias, typically developing at high heart rate (HR) and catecholamine states. Patients are often restricted from exercise. Cardiopulmonary exercise testing (CPET) is used to diagnose and monitor patients to ensure HR-associated arrhythmias are adequately blunted on beta blockers (BB). In addition to peak HR, CPET can also determine the ventilatory anaerobic threshold (VAT), the point at which the body shifts from aerobic to anaerobic metabolism generating lactic acid as a byproduct. VAT is commonly used in prescribing exercise intensity in those with and without heart disease but has not been evaluated in CPVT patients. This transition point could be useful clinically in determining more precise exercise limits in patients with CPVT. To assess if there is an association between VAT and the development of arrhythmia during exercise in those diagnosed with CPVT. This is a retrospective cohort study on all patients with CPVT completing exercise testing at our institution from July 2017 through September 2022. VAT was calculated utilizing the V-slope method. Simple ectopy was defined as single, uniform premature ventricular complexes (PVCs) and complex ectopy defined as polymorphic PVCs or ventricular tachycardia. The HR at the time ventricular ectopy first developed was noted. There were 44 CPETs completed by 10 patients (19.8±10.4 years-old at first test; 50% male) with genetically-confirmed CPVT. Most tests occurred while the patient was on BB therapy (39/44). Patients had simple ectopy in 34 tests and complex ectopy in 25. No patients developed complex ectopy before VAT during any test (Figure 1). Average HR at VAT (101.4±14.7 bpm) was below both the HR at which simple (122.1±14.3 bpm) and complex (136.8±18.4 bpm) ectopy developed. Average HR at each point in exercise was lower in the group on BB than those not on a BB. These HR and arrhythmia trends were similar on the initial CPET at diagnosis and on their subsequent tests. Patients with CPVT seem to reach VAT prior to the onset of ventricular ectopy. Anaerobic metabolism may play a role in the arrhythmogenicity of these patients, possibly due to lactic acid production. If confirmed in larger studies, activity restrictions could be liberalized to allow low-intensity exercise below the VAT with precise HR goals in patients with CPVT.