Comparison of the cardiodynamic and metabolic effects of dobutamine with those of norepinephrine and dopamine in the dog isolated heart.

A comparative study of the cardiodynamic and metabolic effects of norepinephrine, dopamine and dobutamine was carried out on the isolated heart-lung preparation from dogs, modified to measure coronary outflow and myocardial oxygen consumption. Infusions of the three sympathomimetic drugs which increased myocardial contractility, as reflected by maximal rate of rise of left ventricular pressure, dp/dt, by 24%, produced comparable increases in heart rate of 5 to 7% with the three drugs, comparable increases in myocardial oxygen consumption of 11% with dopamine and 19% with dobutamine and a decrease in mechanical efficiency of 13% with dobutamine. At higher doses which increased dp/dt by an average of 68%, heart rate increased by 9%, 19% and 26% following norepinephrine, dopamine and dobutamine, respectively, the increase produced by dobutamine being significantly higher than that produced by norepinephrine. Myocardial oxygen consumption increased significantly following dopamine by 39% and dobutamine by 46% but not following norepinephrine. Mechanical efficiency decreased following dobutamine by 24%. At average increases in dp/dt of 123% and 166%, there were further increases in heart rate and myocardial oxygen consumption and decreases in mechanical efficiency, the changes in each parameter being similar for all three drugs. The increase in coronary outflow was compared with the spontaneous increase which is regularly observed with time in the isolated heart-lung preparation. Only dobutamine was found to increase coronary outflow by 49%, 117% and 137% at increases in dp/dt of 71%, 118% and 173%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)