Assessment of endothelial function by brachial artery flow mediated dilatation in microvascular disease

BACKGROUND Cardiac syndrome X is an important therapeutic and diagnostic challenge to physician. Study of Csx patients may help to understand the pathophysiology of coronary microcirculation and to gain an insight on the management of these group patients. METHODS We measured the flow mediated dilation of the brachial artery both endothelium dependent and independent vasodilatation by high resolution ultrasound in 30 cardiac syndrome X patients and matched with 30 healthy control subjects. RESULTS Significantly decreased flow mediated dilatation was observed in patients when compared to control (9.42±7.20 vs 21.11±9.16 p<0.01) but no significant difference was observed between groups in response to nitroglycerin (25.39±6.82 vs 28.87±8.69). Receiver operator characteristic analysis showed that value of <11.11 had sensitivity of 80%, specificity 86.67%, positive predictive value 76.66%, negative predictive value 83.33%. In total, 46% of subjects had endothelial dysfunction and of them, CSX subjects had higher prevalence (76% vs 16% p<0.01) than control subjects. Higher mean values of body mass index, systolic blood pressure and diastolic blood pressure was observed in subjects with FMD<11.11 than >11.11(p<0.01). In logistic regression analysis, FMD was significantly associated with systolic blood pressure (Odds ratio 1.122 95% CI 1.053-1.196 p<0.01) and body mass index (Odds 1.248 95%CI 0.995-1.56 p<0.05). CONCLUSIONS The study suggests impairment of endothelial function in cardiac syndrome X patients. Increased Systolic blood pressure and body mass index may increase the risk of impairment of endothelial function in this group of patients.