Monitoring regional myocardial function after myocardial revascularization

A system using only small platinum electrodes for monitoring intramyocardial polarographic oxygen tension (MP02), electrograms (ECG), and impedance-derived wall motion (WM) was experimentally tested and clinically implemented. In nine open-chest, anesthetized dogs. two platinum electrodes were inserted along the subepicardial direction of the muscle fibers. As verified by cinefluoroscopy, WM corresponded to changes in distance between the platinum electrodes (r = 0.91 +/- 0.02). The system responded to a 10 minute occlusion of the left anterior descending coronary artery (LAD) as follows: Dyskinetic WM appeared in 10 seconds (p less than 0.05); MP02 decreased (26.4 +/- 1.8 to 14.8 +/= 1.9 mm Hg, p less than 0.05) in 1 minute; ST segments increased (4.8 +/- 1.5 to 12.3 +/- 3.1 mV, p less than 0.05) in 3 minutes. On reperfusion, WM, ST segments, and MP02 normalized in 15 seconds, 30 seconds, and 1 minute, respectively. Hence, ischemia affects WM more acutely than either ECG or MP02. In five patients, ischemic changes before coronary bypass were reversed over 5 days: MP02 (17.4 +/-; 1.9 to 19.6 +/-1.7 mm Hg), ST segment (2.2 +/- 6 to 1.0 +/- 0.4 mV), and WM returned to normal. Thus a system has been designed which simultaneously monitors regional WM, MP02, and ECG. The method has proved to be a sensitive and practical approach for assessing perioperative myocardial function.