Left ventricular dysfunction induced by occlusion of coronary arteries in conscious dogs.

The aim of the present study was to investigate stable left ventricular dysfunction resulting from severe myocardial ischemia in conscious dogs, in order to evaluate the action of cardiotonic agents under pathological conditions mimicking moderate cardiac failure. Mongrel dogs with a catheter implanted in the left ventricle were trained on a treadmill and subjected to a standardized exercise before and after a Harris-type ligation of the anterior descending branch of the left coronary artery in two stages. Two weeks later the lower third of the left circumflex coronary branch was also occluded, and the exercise test repeated for at least two additional weeks to evaluate the changes in the left ventricular function indicated by left ventricular systolic pressure, end-diastolic pressure, heart rate, positive and negative dP/dtmax and dP/dt/P. Noninvasive radionuclide investigations of the left ventricular function and myocardial perfusion were done before and after the development of cardiac failure. Following occlusion of the anterior descending and circumflex coronary arteries, the baseline end-diastolic pressure increased from 7.6 +/- 2.3 mmHg to 23.3 +/- 3.0 mmHg (p < 0.05) and increased even further during exercise (to 49.2 +/- 3.5 mmHg, p < 0.05). After the development of cardiac failure, no substantial change occurred in the end-diastolic pressure, either during rest or repeated exercise tests.(ABSTRACT TRUNCATED AT 250 WORDS)