CENTRAL AND PERIPHERAL HEMODYNAMIC-RESPONSES TO HIGH-CARBOHYDRATE ANDHIGH-FAT MEALS IN HUMAN CARDIAC TRANSPLANT RECIPIENTS

1. Patients with autonomic dysfunction and elderly people with an age- related decline in autonomic function can suffer from a fall in blood pressure after eating, While the cardiovascular changes after eating a nd the effect of meal composition on these changes are well establishe d, the underlying mechanisms are less clear, 2. This study assessed th e cardiac, circulatory and humoral responses to ingestion of isoenerge tic (2.5 MJ) high carbohydrate and high fat meals in nine orthotopic c ardiac transplant recipients, who before transplantation had significa nt circulatory, metabolic and autonomic abnormalities and after transp lantation had complete or partial extrinsic cardiac denervation, and c ompared them to the responses seen in nine healthy age-matched control subjects, 3. All variables were measured non-invasively. Cardiac tran splant recipients, despite cardiac denervation, showed a normal heart rate response to high carbohydrate and high fat meals (maximal increas e at 30 min postprandially +7.8 +/- 1.1 and +6.3 +/- 1.4 beats/min res pectively), a normal cardiac output response to the high carbohydrate meal (maximal increase at 30 min +1.16 +/- 0.25 l/min), but a signific antly attenuated cardiac output response to the high fat meal, Cardiac transplant recipients had attenuated superior mesenteric artery blood flow responses after both meals (P < 0.05) and an attenuated calf vas cular resistance response after the high fat meal (P < 0.01), Througho ut the study after both meals, cardiac transplant recipients maintaine d blood pressure, 4. This study demonstrates that cardiac transplant r ecipients, despite partial or complete cardiac denervation, have a nor mal chronotropic response to food and a normal cardiac output response to a high carbohydrate meal, The attenuated cardiac output response t o a high fat meal did not compromise blood pressure, due at least in p art to decreased splanchnic vasodilatation.