Impaired Myocardial Flow Reserve Is Associated with Pulmonary Hypertension in Patients with Hypertrophic Cardiomyopathy

Objectives: Microvascular function detected by quantitative PET could play a key role in the evaluation of myocardial ischemia in patients with hypertrophic cardiomyopathy(HCM). Pulmonary hypertension is a known complication of HCM and is associated with a poor prognosis even with mild elevations in pulmonary pressures. We aim to investigate the relationship between microvascular dysfunction and pulmonary hypertension in HCM.

Methods: 89 symptomatic HCM patients underwent rest and hyperemia N-13 ammonia PET to quantify global and regional (septal, lateral, anterior and inferior) myocardial blood flow (MBF) and myocardial flow reserve (MFR). Echocardiographic pulmonary artery systolic pressure (PASP) was utilized to estimate pulmonary hypertension. Patients were divided into 2 groups based on present or absent pulmonary hypertension. Results: Compared with patients without pulmonary hypertension (PASP&#8804;36 mmHg, n=58, 65%), patients with pulmonary hypertension (PASP >36 mmHg, n=31, 35%) had larger left atria, higher E/A and E/e' ratio, significantly reduced global stress MBF (1.85± 0.52 vs. 2.13± 0.56 ml/min/g; p<0.05) and MFR (2.21± 0.57 vs. 2.62± 0.75; p<0.01), while the MBF at rest were similar. Global parameters demonstrated the fair correlation with PASP (stress MBF: r=-0.23, p=0.03; MFR: r=-0.32, p=0.002); Regionally, the highest coefficients was observed in septal wall (stress MBF: r= -0.27, p=0.01; MFR: r=-0.31, p=0.003). In multivariate logistic regression analysis including global and regional blood flow assessments, only global MFR (odds ratio: 0.39, 95%CI: 0.18-0.78; p=0.009) was identified as an independent predictor for pulmonary hypertension in our HCM cohort.

Conclusions: Pulmonary hypertension is correlated with impaired microvascular function. Absolute quantification of MFR may be useful as a precursor for pulmonary hypertension in HCM.