Myocardial recovery after cardiac surgery: A study of hemodynamic performance and electrophysiology during the first 18 postoperative hours

Abstract

Hemodynamic and vectorcardiographic variables were monitored in 23 patients with acquired heart disease, before and during the first 18 postoperative hours of cardiac surgery. The hemodynamic pattern directly after surgery was characterized by left ventricular depression and increased heart rate. Thus, stroke volume index had decreased from the preoperative 29 +/- 1 to 24 +/- 1 mL/beat/m2, and heart rate had increased from 61 +/- 2 to 94 +/- 4 beats/min. During the following hours a gradual normalization of stroke volume occurred, leading to a cardiac index that was adequate after 8 to 10 hours, judging from the mixed venous oxygen saturation (68% +/- 1%). Fourteen patients had an uneventful postoperative course, with no signs of acute myocardial infarction, and did not require inotropic support. These patients had small but consistent vectorcardiographic changes; the QRS vector difference increased moderately, and the ST vector magnitude also increased. No correlation was found between hemodynamic and vectorcardiographic variables, nor between timing of hemodynamic recovery and vectorcardiographic changes. Patients with a perioperative myocardial infarction had a vectorcardiographic pattern that was compatible with acute myocardial infarction. These patients had markedly elevated ST vector magnitude and QRS vector difference values, which were discernible during the first postoperative hours. The present data suggest that the timing of metabolic and electrophysiological recovery of the heart differ, and a computerized vectorcardiographic system may be of value in the early detection of perioperative myocardial infarction.