Effects of coronary washout on cardiac function during brief periods of ischemia and hypoxia.

Abstract

Coronary washout has been shown effective in preserving metabolism during hypoxia, but its impact on mechanical function is unknown. To investigate this, experiments were conducted in a regionally perfused swine heart preparation (n = 19) in which oxygen (O2) delivery was repetitively restricted for short times (3 min) by randomly changing coronary flow (delta Qc) and/or arterial oxygen content (delta O2a) in the perfusion circuit. Recovery periods in each animal were at least 15 min between trials. Changes in metabolism and mechanics were expressed as a function of delta Qc and delta O2a (the two independent determinants) using linear regression equations. Significance and the ranking of importance for the two determinants were estimated by F testing, the t values of the respective regression coefficients, and partial regression analysis. Myocardial oxygen consumption (MVO2) was dependent on both flow and O2 content (MVO2% = 115.8 + 0.8 delta Qc% + 1.1 delta O2a%). However, regional mechanical function, including total shortening (TS) and an index of work (Indexw), was dependent only on arterial O2 content, e.g., TS% = 94.9 + 0.1 delta Qc% + 0.8 delta O2a% and Indexw% = 85.5 + 0.2 delta Qc% + 1.1 delta O2a%. In these latter relationships, O2 content ranked higher than Qc by factors of 7.39:1 and 5.34:1, respectively. Thus it was concluded that coronary washout offers no selective advantages in preserving average regional mechanical function during short-term O2 deprivation.