Determinants of right ventricular - pulmonary arterial uncoupling in hypertrophic cardiomyopathy

Abstract Background Right ventricular (RV) – pulmonary arterial (PA) coupling, assessed by echocardiography, is a non-invasive surrogate on how the RV is adapted to an increased afterload in the pulmonary circulation. In cases of exhaustion of compensatory RV remodeling, the ratio decreases and there is RV-PA uncoupling. Our objective was to identify what are the determinants of this parameter in patients with hypertrophic cardiomyopathy (HCM). Methods This prospective cohort study enrolled patients with HCM without obstructive epicardial coronary artery disease, that underwent a comprehensive evaluation. Echocardiography was used to assess RV-PA coupling as the ratio of tricuspid annular plane systolic excursion (TAPSE) to pulmonary artery systolic pressure (PASP). In addition, coronary flow reserve in the left anterior descending artery (CFR_LAD) was also evaluated: diastolic coronary flow velocity was measured in basal conditions and in hyperemia and CFR was calculated as the ratio of hyperemic and basal peak diastolic flow velocities. This was used as a surrogate marker of coronary microvascular dysfunction. Cardiac magnetic resonance (CMR) was also performed to evaluate RV function (volumes and ejection fraction), and the extent of late gadolinium enhancement (LGE) in the left ventricle (LV). Results We enrolled 62 patients, with a mean age of 55 (15) years, 64% males. In 64% it was an asymmetrical septal hypertrophy phenotype, in 31% an apical hypertrophy, and in 27%, it was an obstructive HCM. Mean TAPSE/PASP was 0.556 (0.23) and median was 0.50. All patients had a normal LV ejection fraction. Univariable linear regression analysis showed that age, maximal wall thickness, E/E’, indexed left atrial volume (LAVi), CFR-LAD, %LGE and % hypoperfusion (by CMR) were correlated with RV-PA uncoupling. The HCM phenotype or the presence of obstruction were not associated with uncoupling. Multivariable stepwise linear regression analysis showed that the independent predictors of RV-PA uncoupling were age (b-estimate: - 0.180, p=0.009), LAVi (b-estimate: -0.645, p=<0.001), CFR-LAD (b-estimate: 0.183, p=0.011) and %LGE (b-estimate: -0.270, p=<0.001). Conclusion In patients with HCM, the presence of coronary microcirculation abnormalities and the extent of LGE in the LV are independent predictors of RV-PA uncoupling.