Insulin resistance and hyperlipoproteinemia in microvascular angina: Risk factors or pathogenetic link?

Background: Patients with chest pain and normal epicardial coronary arteries (microvascular angina; syndrome X) are characterized by an impairment of myocardial perfusion reserve which may be related to functional and morphological abnormalities of the intramyocardial arterioles. Methods: In an attempt to identify predisposing factors for microvascular angina we investigated 34 consecutive patients (15 female, 19 male; mean age 53 +/- 7 years) with microvascular angina but without hypertension or left ventricular hypertrophy. The metabolic profile, including plasma insulin, glucose, cholesterol, low-density lipoprotein cholesterol, triglycerides, very-low-density lipoprotein cholesterol and fibrinogen levels, was determined in each case. Furthermore, insulin and glucose levels were measured after an oral glucose load of 100 g over 3 h. All parameters were compared with those of a control group of 15 healthy subjects matched for age, sex and body mass index. Results: The systolic blood pressure in microvascular angina was 137 +/- 17 mmHg and thus higher than that of healthy controls (124 +/- 11 mmHg); diastolic blood pressure was 85 +/- 7 compared with 78 +/- 9 mmHg in controls. Insulin level was significantly elevated in patients with microvascular angina 90 min (median: 101 versus 54 mu U/ml) and 120 min (median: 88 versus 51 mu U/ml) after ingestion of 100 g glucose. The fasting glucose level was 98 +/- 12 versus 87 +/- 7 mg/dl in controls. Glucose concentration was also elevated after 30 min (176 +/- 28 versus 148 +/- 32 mg/dl), after 45 min (198 +/- 35 versus 152 +/- 53 mg/dl) and after 60 min (193 +/- 44 versus 145 +/- 54 mg/dl). In microvascular angina, parameters such as total cholesterol (244 +/- 46 versus 199 +/- 29 mg/dl), low-density lipoprotein cholesterol (157 +/- 41 versus 122 +/- 18 mg/dl) and fibrinogen (377 +/- 150 versus 285 +/- 69 mg/dl) were elevated. Conclusions: The metabolic profile in patients with microvascular angina suggests a pathogenetic role of insulin resistance and hyperlipoproteinemia in the setting of impaired myocardial coronary reserve and in early stages of hypertensive heart disease.