Multiparametric CMR Tissue Characterization Distinguishes Pathological From Physiological Cardiac Hypertrophy and Correlates With CPET Findings

Introduction: Physiological and pathological cardiac hypertrophy differ in terms of mechanisms, phenotypes, and outcomes. We aimed to characterize the cardiac tissue phenotype of athletes and HF patients. Methods: Prospectively enrolled participants underwent CMR and CPET. HF patients (NYHA class II-III) were classified as HFpEF (LVEF>=45%) or HFrEF (LVEF<45%). Results: One-hundred and eighty participants were categorized in four groups: athletes (n=44, 32±12 years), HFpEF (n=47, 61±11 years, H2FPEF score 5±2), HFrEF (n=47, 54±10 years), and healthy controls (n=42, 41±13 years). LVEF was markedly reduced in HFrEF (athletes 65±6%, HFpEF 59±11, HFrEF 29±9, controls 66±4, p<.001). LV mass index (athletes 65±6%, HFpEF 59±11, HFrEF 29±9, controls 66±4, p<.001) and cardiomyocyte mass index (athletes 64±15g/m 2 , HFpEF 66±24, HFrEF 82±36, controls 42±8, p<.001) were greater in athletes and in HF patients (Fig 1A). Athletes and HFpEF patients had concentric LV remodeling, while HFrEF patients showed eccentric remodeling (Fig 1B). Intracellular lifetime of water was longer in athletes and shorter in HFrEF (athletes .17±.07s, HFpEF .15±.05, HFrEF .13±.05, controls .14±.05, p<.001) (Fig 2A). ECV was similarly increased in both HF groups (athletes .28±.04%, HFpEF .31±.05, HFrEF .31±.05, controls .28±.04, p<.001) (Fig 2B). Native T1 (athletes 1175±55ms, HFpEF 1261±61, HFrEF 1274±61, controls 1229±75, p=.01) correlated with CPET maximal oxygen consumption (VO 2 max) in HF patients (r=-.023, p=.048) (athletes 52±10, HFpEF 18±6, HFrEF 17±4, controls 29±9, p<.001). Conclusion: Physiological hypertrophy was characterized by increased cardiomyocyte diameter, normal ECV, and shorter native T1 due to its greater cardiomyocyte volume. Contrastingly, pathological hypertrophy’s longer native T1 was a result of its higher ECV and correlated with VO 2 max in HF. Cardiomyocyte diameter was smaller in HFrEF than in HFpEF.