958-98 Reduction in Exercise Threshold to Post-prandial Angina Occurs After Carbohydrate, but not Fat or Protein, and Independently of Myocardial Oxygen Consumption

Abstract

We investigated the role of food constituents in mechanisms contributing to post-prandial angina (PPA). Studies were performed in 8 males (aged 60 ± 3 yrs). with reproducible PPA, after an overnight fast, off drugs (except GTN) for 3 days. HR, BP, rate pressure product (RPPI, time to onset of angina (TA) and 1 mm ST depression (TST), plasma noradrenaline (NOR, nmol/l) and adrenaline (AD, nmol/l, were measured before, 30 min after water (WM), liquid carbohydrate (CM), fat (FM), and protein (PM) meals, and during exercise (Bruce protocol). Meals were isocaloric (1000 cal), isovolumic, and administered in random order, on separate days. HR, BP, and RPP increased to similar levels 30 min after CM, FM and PM, compared to WM. During exercise TA, TST and ED were reduced after CM, but not FM or PM, compared to WM ( * = p < 0.05). RPP was unchanged after CM, but increased after FM and PM, compared to WM. Plasma NOR rose after CM (3.4 ± 0.4 to 4.9 ± 04 * ) and FM (3.1 ± 0.3 to 4.2 ± 0.2 * ), but not after PM or WM. Plasma AD did not rise after meals. Angina 1 mm ST DEP Peak Exercise TA (sec) RPP × 10 -3 TST (sec) RPP × 10 -3 Time (sec) RPP × 10 -3 WM 141 ± 20 16 ± 07 141 ± 20 17 ± 1.2 317 ± 62 18 ± 1.2 CM 109 ± 17 * 18 ± 10 109 ± 17 * 18 ± 1.4 254 ± 66 * 20 ± 1.2 FM 157 ± 59 17 ± 1.0 157 ± 21 19 ± 1.2 * 287 ± 62 20 ± 1.2 PM 149 ± 64 18 ± 0.5 * 149 ± 22 18 ± 1.0 291 ± 65 20 ± 1.1 * 1. Decrease in time to angina, 1 mm ST DEP, and peak exercise occur after carbohydrate meal but not fat meal or protein meal. 2. This is not accompanied by a rise in rate-pressure product after carbohydrate meal unlike fat meal and protein meal. 3. Decreased exercise threshold to post-prandial ischaemia after carbohydrate meal occurs independently of increased myocardial oxygen consumption, suggesting ‘steal’ mechanisms contribute.