Abstract
BACKGROUND: Although standard cardiac magnetic resonance (CMR) findings are typically normal in patients with idiopathic premature ventricular contractions (PVCs), it remains unclear whether a comprehensive protocol incorporating left ventricular (LV) strain and tissue characterization can detect subclinical myocardial abnormalities. This study aimed to determine if advanced CMR parameters can reveal a burden-dependent myocardial phenotype in patients with idiopathic PVCs. METHODS: In this retrospective study, 72 patients with idiopathic PVCs and 25 controls underwent comprehensive 3T CMR with feature-tracking (FT) strain analysis and native T1/T2 mapping. Patients were stratified by 24-hour PVC burden into three groups: <500 PVC/24 h (n=24), 500-10,000 PVC/24 h (n=23), and >10,000 PVC/24 h (n=25). RESULTS: Compared to controls, patients with >10,000 PVC/24 h (high burden) exhibited significantly impaired myocardial strain after multiple-comparison correction, including reductions in two-dimensional (2D) global radial (27.4%±7.0% vs. 33.9%±6.2%; P=0.005), 2D global circumferential (-16.7%±2.8% vs. -19.2%±2.1%; P=0.001), three-dimensional (3D) global circumferential (-17.5%±3.7% vs. -20.6%±2.0%; P=0.003), 2D apical radial (28.1%±11.0% vs. 40.2%±12.2%; P=0.002), and 2D apical circumferential strain (-16.7%±4.4% vs. -20.8%±3.8%; P=0.001). Notably, the most pronounced strain impairment was observed in the apical segments. These strain parameters were also significantly impaired in the high-burden compared to the low-burden (<500 PVC/24 h) group (all P values <0.05). Moreover, the high-burden demonstrated elevated global native T1 (1,344.5±40.0 vs. 1,289.4±16.6 ms in controls; P<0.001) and T2 (54.4±3.7 vs. 49.4±3.1 ms in controls; P<0.001) values, with the most pronounced alterations localized to the basal segments (T1 and T2; P<0.001 for comparison with controls). A significant dose-response relationship was confirmed for both strain and mapping parameters across the burden groups. CONCLUSIONS: As a hypothesis-generating study, our work, based on comprehensive CMR assessment, identified a novel, burden-dependent myocardial phenotype in patients with idiopathic PVC. The discovery of this phenotype, characterized by distinct patterns of systolic dysfunction and interstitial alterations, should be examined in terms of its clinical and prognostic significance in subsequent longitudinal studies.