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 microU/ml) and 120 min (median: 88 versus 51 microU/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.