Cardiac cryolesions: factors affecting their size and a means of monitoring their formation.

Twenty-seven endocardial cryolesions were created in mongrel dogs and analyzed to determine the effects on cryolesion size of both the initial myocardial temperature (37 degrees C versus 12 degrees C) and the pressure within the nitrous oxide delivery line (tank pressure of more than 700 pounds per square inch [psi] versus tank pressure of less than 700 psi). In addition, local myocardial temperatures were monitored to determine their utility in the intraoperative determination of the extent of cryothermic cell death. Cryolesion volume was significantly affected by both the initial myocardial temperature (p less than 0.001) and the line pressure (p = 0.014). In a 37 degrees C myocardium, the mean lesion volume ranged from 0.501 +/- 0.183 cc at line pressures lower than 700 psi to 0.839 +/- 0.258 cc at line pressures greater than 700 psi. In a 12 degrees C myocardium, the mean volume was 1.151 +/- 0.436 cc at line pressures lower than 700 psi and 1.361 +/- 0.288 cc at line pressures higher than 700 psi. A myocardial temperature of 0 degrees C occurs at the edge of the area of cell death. When analyzing the range from -5 degrees to +5 degrees C, the probability of a point at or lower than 0 degrees C falling inside the cryolesion is 84.2%. Monitoring intramyocardial temperature will predict the border of a cryolesion.

Large animal model of left ventricular aneurysm.

In 28 Dorsett sheep, ligation of the distal homonymous (equivalent to human left anterior descending) and second diagonal coronary arteries produced a constant transmural infarct of 22.9% +/- 2.5% (mean +/- standard deviation) of the left ventricular mass. Serial left ventriculograms showed that within four hours the infarct segment expands, wall thickness decreases, and aneurysmal dilatation occurs and progresses over the next 60 days in all sheep. Epicardial ventricular point references indicated that adjacent noninfarcted myocardium participates in the formation of the aneurysm. Anatomy of the coronary vasculature was studied in 22 excised sheep hearts. In sheep, coronary arterial anatomy is remarkably constant. The left coronary artery provides all of the blood supply to the left ventricle and septum and only a small rim of both the anterior and posterior right ventricles. Cardiac veins from the left ventricle drain into the coronary sinus, which also receives the left azygos vein. Right ventricular veins drain separately. The essentially separate coronary circulations to the two ventricles, the paucity of coronary collateral circulation, and the consistent evolution of left ventricular infarcts into aneurysms are important advantages of the ovine model for both metabolic and ventricular mechanical studies of acute myocardial infarction and left ventricular aneurysm.

Emergency and elective surgery in patients over age 70.

Emergency surgery in 100 patients over age 70 was associated with a 31 per cent morbidity and a 20 per cent mortality, significantly greater than the 6.8 per cent morbidity and 1.9 per cent mortality following elective procedures in the same age group (P less than .0005). Sixteen per cent (100 of 613) of all geriatric patients were operated on under emergent conditions and the postoperative hospitalization was often significantly prolonged when compared with similar elective operations (P less than .05). Emergency surgery was most commonly performed on the large bowel (25%), abdominal wall (17%), stomach (17%), biliary tract (11%), and small bowel (10%). Inguinal herniorraphy was the most frequently performed elective procedure (33%), followed by colon resection (25%), and cholecystectomy (12%). Fifty-nine per cent (23 of 39) of complications associated with urgent operation and 39 per cent (16 of 41) following elective surgery involved the cardiorespiratory systems and were frequently related to underlying diseases. Of the 20 patients who died in the intensive care unit of multisystem failure, 16 had undergone emergency procedures. Elective surgery in the elderly may be performed safely; however, emergency surgery entails a high risk to the patient and a high cost in hospital resources.

The effect of insulin and glucagon on systolic properties of the normal and septic isolated rat heart.

Controversy exists in the literature concerning the effects of insulin and glucagon on cardiac muscle contractility, in particular during anoxia, ischemia or sepsis. The purpose of the present study was to determine the effects of insulin and glucagon on the systolic function of the normal and the dysfunctioning septic rat myocardium in the Langendorff preparation. In the normal isolated rat heart, neither insulin nor glucagon exhibited any lasting inotropic effect on systolic function or coronary flow. Sepsis (cecal ligation and puncture) resulted in a dramatic reduction of systolic function to 44% of control animals. All insulin-containing formulations tested improved systolic function in septic hearts by a mean of 85% compared to Krebs and glucose only. However, this improvement did not reach statistical significance compared to the use of Krebs and glucose only. Glucagon at 100 micrograms/l was doing as well as Krebs and glucose alone while at 1 mg/l glucagon was only able to maintain pre-perfusion contractility. Our results suggest that neither insulin nor glucagon seem to possess special inotropic properties for the isolated perfused normal or septic rat heart.

The different effects of leucine, isoleucine, and valine on systolic properties of the normal and septic isolated rat heart.

Protein turnover in cardiac and skeletal muscle is affected by the provision of amino acids, particularly the branched chain amino acids (BCAA). The effect of each of the BCAA, valine, leucine, and isoleucine, on the systolic function of isolated normal or septic rat heart perfused as a Langendorff preparation was examined. Thirty normal control and 28 septic rats (cecal ligation and puncture) were perfused with either Krebs + 8.5 mM glucose or Krebs + 5.0 mM glucose and 3.5 mM valine, leucine, or isoleucine. Septic hearts perfused with Krebs + 8.5 mM glucose exhibited developed force (DF) and force velocity (dF/dt) levels which were reduced to an average of 45 and 50%, respectively, compared to normal controls, and improved by 35% during 60 min perfusion over measurements made at time zero. In normal hearts DF and dF/dt decreased significantly during perfusion with leucine (27%) and isoleucine (20%). In sepsis, perfusion with leucine and isoleucine resulted in a mild improvement in systolic function. However, valine was far less effective than leucine and isoleucine in maintaining systolic function in sepsis, due apparently to valine being a less efficient energy substrate for the cardiac muscle in a state of severe energy deficit. Thus, valine, leucine, and isoleucine seem to exert different effects on the systolic function of normal and septic isolated rat hearts.