Impaired coronary flow reserve in dilated cardiomyopathy: lack of tissue microvasculature remodeling

Abstract

Objective: The aim of this study is to evaluate the cause of CFR impairment in DCM patients by correlating functional CFR assessed and microvascular structural abnormalities measured on endomyocardial biopsy (EMB). Materials and methods: We evaluated EMBs from 26 consecutive DCM patients and EMBs from 11 consecutive Heart Transplant patients. We performed morphometric analysis on EMBs. We measured myocyte mean diameter, capillary density, microvascular remodeling (vessel media area/total vessel area ratio (%)). Coronary flow velocity in the left anterior descending coronary artery was detected by Transthoracic Doppler Echocardiography (TDE) at rest and during adenosine infusion. CFR was the ratio of hyperemic diastolic flow velocity (DFV) to resting DFV. A CFR≤2.5 was considered abnormal. The results were compared to a control group, consisted of 11 heart-transplant (HTx) patients with impaired CFR due to microvascular remodeling. Results: Despite CFR in DCM patients is comparable to the HTx pts (2,25±0,61 vs. 2,0±0,5, p=0.4), microvascular remodeling is significantly lower in DCM pts compared to HTx group (43,93±7,12% vs. 72,3±8,0%, p<0,0001). In DCM patients capillary density (194,83±22,63 vs. 157,2±42,4, p=0,03), fibrosis (19,44±7,55% vs. 6,8±5,0%, p<0,02) and myocyte mean diameter (23,79±3,01μm vs. 20,5±3,7μm, p=0,5) are significantly higher than in HTx group. In DCM patients CFR shows a significant inverse correlation with central venous pressure (r= -0,692, p=0,02), with right heart pressure (r= -0,609, p=0,05) and with NTproBNP (r= -0,754, p=0,01) and a positive correlation with cardiac output (r=0,737, p=0,01) and oxygen consumption (r=0,412, p=0,02). Conclusion: CFR impairment in DCM patients is not related to microvascular remodeling. It is closely related to cardiac performance and the patient's clinical status. Patients with pathological CFR (CFR<2,5) have a poorer prognosis, since they have worsen clinical and hemodynamic conditions.