Early pathological changes of coronary microvasculation in heart failure with preserved ejection fraction

The majority of heart failure with preserved ejection fraction (HFpEF) patients present with coronary microvascular dysfunction (CMD). However, it is uncertain whether CMD is a primary factor in ventricular remodeling/diastolic dysfunction and HFpEF, or whether CMD is secondary to myocardial remodeling in HFpEF. Eight-week-old male C57BL/6N mice were simultaneously administered with high-fat diet (HFD) and N(ω)-nitro-L-arginine methyl ester (L-NAME) via drinking water for 5 weeks. Body weight, blood pressure and glucose tolerance, athletic endurance were observed. Cardiac systolic and diastolic function were detected using trans-thoracic Doppler echocardiography. Heart weight/tibial length and wheat germ agglutinin staining (WGA) were performed to evaluate cardiomyocytes. To detect the degree of cardiac fibrosis, picrosirius red (PSR) staining was performed. The coronary microvascular and pericytes were investigated by immunofluorescence staining. Coronary flow reserve (CFR) was measured by echocardiography to assess the coronary microvascular function. The HFpEF mouse model was constructed using HFD and L-NAME. HFpEF was evident by preserved ejection fraction (EF), fractional shortening (FS) and significantly elevated E/e’, impaired glucose tolerance and reduced exercise capacity in mice treated with L-NAME and HFD. Cardiomyocyte hypertrophy and cardiac fibrosis were observed in the HFpEF group. The density of capillary was decreased in HFpEF group, accompanied by increased capillary diameter and tortuosity. Moreover, the number and coverage rate of cardiac pericytes were reduced in HFpEF group. No significant differences were found in CFR after modeling 5 weeks. But CFR was decreased in HFpEF group when extending modeling time to 12 weeks. Our findings have demonstrated that coronary microvascular pathological changes appeared during the early stages of HFpEF and appeared before coronary functional indicator changed.