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Oral Abstract

Oral Abstract Clinical #3- Transformative Cardiac MRI Research

Novel insights into arrhythmic risk in sarcomere-positive and negative hypertrophic cardiomyopathy: a comprehensive multiparametric cardiac magnetic resonance and spectroscopy study

Saturday, February 1, 2025
11:10 AM – 11:20 AM East Coast USA Time
Location: Diplomat Ballroom
Background: The lifetime burden of ventricular arrhythmia and sudden cardiac death among patients with hypertrophic cardiomyopathy (HCM) is higher in those with sarcomeric variants (Sarc+HCM) compared to those without (Sarc-HCM)(1). We hypothesised that pathogenic sarcomere variants might lead to this increased risk by creating a higher burden of microstructural and metabolic abnormalities. We prospectively evaluated hypertrophy-matched Sarc+ and Sarc-HCM patients with multiparametric cardiac magnetic resonance (CMR) imaging and assessed whether the cumulative burden of such abnormalities associated with arrhythmic risk.

Methods: One hundred prospectively recruited participants (39 Sarc+HCM, 41 Sarc-HCM, and 20 healthy controls) underwent multiparametric CMR including 31P-MRS, diffusion-tensor imaging (DT-CMR), blood oxygen level-dependent imaging (BOLD), and quantitative myocardial perfusion imaging. HCM patients without prior history of non-sustained VT (NSVT) underwent extended ECG monitoring. Myocardial energetics were assessed by measuring the phosphocreatine-to-ATP (PCr/ATP) ratio, myocardial oxygenation by ∆BOLD (%), myocardial disarray by fractional anisotropy (FA), sheetlet orientation by |E2A|°, myocardial perfusion by myocardial perfusion reserve (MPR), and fibrosis by late gadolinium enhancement (LGE).

Results: Sarc+ and Sarc-HCM participants had similar maximum wall thickness (20mm vs 18mm, p=0.131). Sarc+HCM were younger than their Sarc-HCM counterparts (51 years vs 57 years, p=0.005), but had greater LGE burden (13% vs 5%, p=0.009). PCr/ATP ratios were equally reduced in Sarc+ and Sarc-HCM compared to controls (1.64 vs 1.64 vs 1.97, p< 0.001). Sarc+ and Sarc-HCM exhibited comparable hypercontractile diastolic |E2A|° relative to controls (51° vs 53° vs 28°, p< 0.001). In the most hypertrophied segments, Sarc+HCM patients had lower FA than Sarc-HCM patients (0.46 vs 0.50 vs 0.57, p< 0.05), indicating greater myocardial disarray. MPR was equally reduced in both groups compared to controls (p=0.01), yet Sarc+HCM participants showed more blunted myocardial oxygenation (∆BOLD 9% vs 12% vs 19%, p=0.01 ). PCr/ATP, FA, LGE and ∆BOLD were independently associated with NSVT. The presence of one of these CMR abnormalities in the worst quartile associated with a nearly fourfold increased risk of NSVT (OR 3.8, p< 0.001), and two or more increased the risk almost fifteen times.

Conclusion: Despite matching for degree of hypertrophy, Sarc+HCM patients exhibited a greater burden of microstructural and metabolic abnormalities at a younger age compared to Sarc-HCM patients. The cumulative burden of these abnormalities significantly increased the risk of NSVT amongst patients. These findings provide mechanistic insights into the higher risk of arrhythmias and sudden cardiac death among Sarc+HCM patients.

Main Illustration- Burden of microstructural and metabolic abnormalities in sarcomeric and non-sarcomeric HCM