Metabolism in human endomyocardial biopsies and cardiac work

The activities of the Krebs cycle (KC), glycolytic pathway (GP), and the hexose monophosphate shunt were studied in endomyocardial biopsies obtained from 25 patients and were related to left ventricular stroke work index (LVSWI). Unexpectedly, KC activity was greater in patients with a reduced LVSWI than in those with a normal or elevated LVSWI. When the cardiac work:KC ratio, defined as LVSWI divided by KC activity, was plotted against LVSWI, the correlation coefficient was 0.86. Cardiac work did not correlate with other metabolic pathways measured. Patients with a reduced LVSWI generated less cardiac work per unit of KC activity than those who had a normal or elevated LVSWI. These data indicate that a reduction in LVSWI below 40 gram-meters/square meter (gm-m/m2) may be associated with either inefficient energy production, inefficient energy utilization, or both.