Post-challenge hyperinsulinaemia rather than hyperglycaemia is associated with the severity of coronary artery disease in patients without a previous diagnosis of diabetes mellitus.

OBJECTIVE: To ascertain the prevalence of abnormal glucose metabolism in patients with coronary artery disease (CAD) but no previous diagnosis of diabetes mellitus (DM) and to examine the relation between the severity of CAD and responses of glucose and insulin to the glucose tolerance test. METHODS AND RESULTS: Abnormalities of glucose metabolism and insulin response were analysed in 144 patients with CAD without a previous diagnosis of DM who underwent both coronary arteriography and 75 g oral glucose tolerance test. The proportions of impaired and diabetic glucose tolerance were very high (39% for impaired and 21% for diabetic glucose tolerance); only 40% had normal glucose tolerance. The parameters of glucose metabolism were not associated with the number of diseased coronary arteries or the presence of previous myocardial infarction (MI). However, the insulin concentration at 60 minutes or 120 minutes after glucose challenge, insulin area, and the ratio of insulin to glucose area were significantly higher in patients with significant coronary stenosis and with previous MI. Fasting glucose concentration and most conventional risk factors did not predict post-challenge hyperinsulinaemia. CONCLUSION: Patients with CAD without a previous diagnosis of DM had a high prevalence of abnormal glucose tolerance. Post-challenge hyperinsulinaemia was associated with the number of diseased coronary arteries and the presence of previous MI. The insulin response to the glucose challenge test requires further investigation as a potential risk factor for CAD and a potential target for intervention.

Exercise myocardial perfusion scintigraphy is useful for evaluating myocardial ischemia even in the elderly.

Pharmacologic stress testing is recommended to elderly patients as a valuable alternative to exercise testing. We examined whether exercise testing is as useful for evaluating myocardial ischemia in the elderly as in the young. The consecutive 1,508 patients who underwent exercise 201Tl single-photon emission computed tomography (SPECT) were divided into six age groups: 6-29 years (n = 56), 30-44 (n = 143), 45-54 (n = 311), 55-64 (n = 498), 65-74 (n = 402), and 75-88 (n = 98). Both heart rate and rate-pressure product at peak exercise were significantly lower in patients aged 75-88 than in the other five groups. The frequency of ischemic ST depression was higher in patients aged 75-88 than in those aged 6-74, although the difference was not significant. Moreover, the frequency of 201Tl transient defect was significantly higher in patients aged 75-88 than in those aged 6-74. On the other hand, the sensitivity of ischemic ST depression for 201Tl transient defect was similar among the six groups, but the specificity was significantly lower in patients aged 75-88 than in those aged 6-74. In conclusion, exercise 201Tl SPECT is useful for evaluating myocardial ischemia even in the elderly, but exercise electrocardiography has limitations such as lower specificity in the elderly than 201Tl SPECT.

Metaiodobenzylguanidine and heart rate variability in heart failure.

It is assumed that the low-frequency power (LF) of heart rate variability (HRV) increases with progress of congestive heart failure (CHF), therefore positively correlating with cardiac 123I-metaiodobenzylguanidine (MIBG) washout. It is demonstrated here that HRV, including normalized LF, correlated inversely with MIBG washout and positively with the ratio of heart-to-mediastinum MIBG activity in controls and CHF patients, whereas these correlations were not observed within CHF patients. Thus MIBG washout may increase and HRV including normalized LF may decrease with CHF, although the HRV and MIBG measures may not similarly change in proportion to the severity of the cardiac autonomic dysfunction in CHF.