Thoracic epidural anesthesia reduces myocardial infarct size after coronary artery occlusion in dogs

The effect of thoracic epidural anesthesia (TEA) with lidocaine on regional myocardial blood flow (RMBF), hemodynamic performance, and myocardial infarct size after coronary artery occlusion was assessed in 21 dogs. In seven dogs, the left anterior descending coronary artery (LAD) was temporarily occluded twice: once before TEA (control) and once during TEA. Systemic hemodynamic parameters, RMBF (using radionuclide-labeled microspheres), and epicardial electrocardiographic maps (15 sites) were obtained before and 15 min after each temporary LAD occlusion. Compared with the ischemic period before TEA, the following were decreased during ischemia with TEA: heart rate, ST segment elevation, cardiac index, the peak first time derivative of left ventricular (LV) pressure, LV tension-time index, the rate-pressure product, and LV stroke-work index. Ischemic zone endocardial RMBF was increased from a control value of 26 +/- 6% to 36 +/- 6% of normal during TEA (P less than 0.05). An additional 14 dogs randomly received either TEA (1% lidocaine, 10 ml/hr) or epidural saline plus 1% lidocaine (10 ml/hr, intramuscularly), beginning 1 hr after LAD occlusion. After 6 hr, the heart was removed and the left ventricle was sectioned parallel to the atrioventricular groove. The infarcts (tetrazolium-stained) were 46% smaller with TEA than with saline, 15.4 +/- 1.8% vs 28.7 +/- 2.3% of the left ventricle (P less than 0.05). Thus TEA reduced hemodynamic correlates of myocardial O2 consumption, improved regional (ischemic zone) endocardial perfusion, and reduced the extent of myocardial infarction.