B-po05-021 repeatability of ventricular arrhythmia characteristics during exercise stress testing in patients with catecholaminergic polymorphic ventricular tachycardia

In patients with catecholaminergic polymorphic ventricular tachycardia (CPVT), the exercise stress test (EST) is the cornerstone for both the diagnosis of CPVT and assessment of therapeutic efficacy. In general, the presence of couplets or more complex ventricular arrhythmias (VA) during EST compels treatment intensification. However, the repeatability of VAs on consecutive ESTs is unknown. To test the repeatability of VA characteristics on consecutive ESTs in patients with CPVT. We retrospectively assessed all ESTs of patients diagnosed with CPVT and included EST pairs (defined as consecutive ESTs within 18 months and without treatment or on the exact same treatment). Multiple EST pairs per patient were allowed. We performed paired analyses of VA complexity, which was defined as mild [absence of ventricular ectopy, isolated premature ventricular complex (PVC), or bigeminal PVCs] or complex [couplets or NSVT], and heart rate at the first PVC (HR-PVC1). A total of 128 EST pairs from 71 patients (median age at first EST: 32.0 [16.5-45.5] years, 52.1% female) were included with a median time interval of 6.2 [4.2-11.7] months between ESTs. Nineteen (14.8%) EST pairs were off treatment, 46 (35.9%) on beta-blocker monotherapy, 5 (3.9%) on flecainide monotherapy and 58 (45.3%) on therapy with beta-blocker and flecainide. Baseline heart rate, maximum heart rate, exercise time, maximum workload, protocol and reason for discontinuation were similar between the EST pairs. VAs on the first EST were mild in 107 (83.6%) cases and remained mild in 93 (86.9%) of the paired ESTs. VAs on the first EST were complex in 21 (16.4%) cases and remained complex in 13 (61.9%) of the paired EST. The repeatability of VA complexity was moderate (kappa=0.44). HR-PVC1 was moderately repeatable (intraclass correlation coefficient: 0.71 (95% CI 0.56-0.83), p<0.001), and the mean absolute difference was 0.4±39 beats per minute. In this cohort of patients with CPVT, repeatability of VA characteristics on consecutive ESTs seemed moderate despite similar circumstances. These findings warrant further research into the reasons thereof to ultimately improve EST repeatability and thereby its clinical value in patients with CPVT.