Right ventricular to pulmonary arterial uncoupling: clinical, functional and morphological insights in patients with hypertrophic cardiomyopathy

Right ventricular (RV) to pulmonary arterial (PA) uncoupling measures RV exhaustion. There is limited evidence regarding the association between RV to PA coupling and hypertrophic cardiomyopathy (HCM). Evaluate RV to PA uncoupling in patients with HCM. Prospective cohort study in 62 patients with HCM without obstructive epicardial coronary disease. Echocardiography was used to assess RV to PA coupling as the ratio of tricuspid annular plane systolic excursion (TAPSE) to pulmonary artery systolic pressure (PASP). Coronary flow reserve in the left anterior descending artery (CVFR_LAD) was a surrogate marker for coronary microvascular dysfunction. Cardiopulmonary exercise testing (CPET) and cardiac magnetic resonance (CMR) were also performed. Mean age was 55 (15) years, 65% males. Mean TAPSE/PASP was 0.56 (0.23). The independent predictors of RV to PA coupling were age (β: - 0.184), left atrial volume index (β: - 0.641), CFVR_LAD (β: 0.183) and the extent of LGE in the LV (β: - 0.262). 43.5% showed reduced exercise tolerance. Independent predictors of peak VO2 were male gender (β: 0.349), age (β: - 0.286), global radial strain (β: 0.249) and TAPSE/PASP (β: 0.253). TAPSE/PASP showed a modest predictive accuracy for peak VO2 < 20 ml/Kg/min (AUC 0.671, p = 0.022), with the best cut-off set at 0.60 mm/mmHg (sensitivity 85% and specificity 47%). A TAPSE / PASP ≤ 0.60 mm/mmHg was present in 66% of patients. In patients with HCM, both coronary microvascular dysfunction and fibrosis are associated with RV to PA coupling, which is a determinant of exercise tolerance.