The oral glucose tolerance test induces myocardial ischemia in healthy older adults

Abstract

Postprandial myocardial ischemia has been observed in frail older adults with postprandial hypotension and in patients with severe coronary artery disease, especially after high doses of carbohydrates. The impact of oral glucose on myocardial oxygen supply and demand in healthy older adults without postprandial hypotension or postprandial angina remains unexamined. We hypothesized that oral glucose would result in decreased myocardial oxygen supply relative to demand in a healthy older subject pool free of postprandial hypotension, reversible coronary risk factors and postprandial angina. 19 older adults (mean age 71.9+/-1.1 yr) were screened for reversible coronary risk factors. Subjects were given a standardized oral glucose load (75 g) or a sham isovolumetric unsweetened drink during two separate sessions. Indirect measures of oxygen supply (Diastolic Pressure Time Index, DPTI) and demand (Rate Pressure Product, RPP; Systolic Pressure Time Index, SPTI) were obtained from aortic arterial blood pressure waveforms. The Subendocardial Viability Ratio (SEVR, DPTI/SPTI) and DPTI/RPP were also calculated. Oral glucose resulted in decreases in both SEVR (P=0.016) and DPTI/RPP (P=0.028) in the glucose session, indicating a decrease in the relative myocardial oxygen supply to demand. This was due solely to a decrease in myocardial oxygen supply while measures of myocardial oxygen demand did not change significantly. Oral glucose decreases myocardial oxygen supply in older adults free of severe coronary artery disease and without postprandial hypotension. This represents a previously unrecognized complication of oral glucose tolerance tests in healthy older adults.