Rutger Bendz

Myocardial Protection During Aortic Valve Replacement: Cardiac Metabolism and Enzyme Release Following Continuous Blood Cardioplegia

Cardiac metabolism following hypothermic potassium cardioplegia with blood as cardioplegia vehicle was studied in two groups of patients undergoing aortic valve replacement. In 15 patients, blood was given as single dose infusion (single dose group) and in 18 patients the same initial bolus was followed by a continuous perfusion (25-30 ml/min) with modified blood from the heart-lung machine (continuous blood group). Simultaneous samples were drawn from arterial and coronary sinus blood before and during the first 60 min after cardioplegia. In the continuous blood group, samples were also drawn during the period of cardioplegic perfusion. The samples were analyzed for PO 2, O2-saturation and content, PCO2, pH, lactate, pyruvate, glucose, potassium, myoglobin, creatine kinase (CK), its isoenzyme MB, and aspartate aminotransferase (ASAT). In addition myoglobin and enzymes were followed in peripheral venous blood for 24 hours. Myocardial biopsies were taken from the left ventricle at the beginning and end of cardioplegia and analyzed for adenosine triphosphate (ATP), creatine (C) and creatinephosphate (CP). The pattern of metabolic changes after cardioplegia was similar in both groups with decreased myocardial oxygen extraction, marked lactate and potassium release, increased glucose uptake and significant enzyme and myoglobin release. However, the degree of changes was significantly smaller in the continuous blood group. The myocardial biopsies also showed significantly less ATP and CP decrease in the continuous blood group, suggesting, together with the other metabolic results, that the myocardial protection afforded by continuous blood cardioplegia was superior to that of the single dose group. Furthermore, continuous perfusion permitted easy control of myocardial temperature during the period of aortic cross-clamping.

Serum Enzymes with Special Reference to CK-MB Following Coronary Bypass Surgery

In a consecutive series of 25 coronary bypass operations, the postoperative serum activity levels of total creatine kinase (CK) and its more heart-specific isoenzyme CK-MB were examined and related to the levels of aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT) and thermostable lactate dehydrogenase (LD-T), to electrocardiographic (ECG) findings and to surgical characteristics. Detectable CK-MB activity was found in all patients, usually appearing while the operation was still in progress. Peak CK-MB occurred earlier than peak total CK. There was no ECG evidence of myocardial infarction in any patient. The degree of postoperative CK-MB elevation, however, correlated to the duration of extracorporeal circulation (ECC) and aortic cross-clamping (AC). After 120 min of ECC and 70 min of AC, release of CK-MB, as well as of the other enzymes studied, increased considerably. There was a significant correlation between high CK-MB activity and high early postoperative activities of total CK, ASAT and LD-T. When CK-MB determinations are not available, ASAT is preferable to total CK or LD-T in the early evaluation of operative myocardial injury. From the fourth postoperative day, only LD-T is informative in this respect; a second rise of ASAT and ALAT is probably of hepatic origin.

Diagnostic Significance of Serum Ck-Mb Elevations Following Surgical Damage to Skeletal Muscles

Total creatine kinase (CK) and its isoenzyme MB (CK-MB) were studied in the serum of 14 patients following thoracotomy, mostly for pulmonary surgery, and in various thoracic muscles from another 9 patients subjected to the same procedure. CK-MB consistently appeared in the serum and was present in all muscle samples examined. CK-MB as a percentage of total CK (the CK-MB/CK ratio) was of similar order in serum and muscle, approximately 1.5%. Compared with previous findings after cardiopulmonary bypass surgery, maximum serum CK-MB activity occurred later, and the CK-MB levels as well as the CK-MB/CK ratio were considerably lower after non-cardiac thoracic surgery. It is suggested that the CK-MB/CK ratio 24 hours after operation may be used in the diagnosis of peri-operative myocardial infarction, particularly in non-cardiac surgery. After thoracotomy, this ratio was below 2.2%. In a series of patients with acute myocardial infarction, reported previously, the ratio was above 5.4%. Secondary rises of serum CK-MB following cardiac surgery should, apparently also be analysed in relation to the simultaneous total CK level.

Myocardial Protection During Aortic Valve Replacement. Cardiac Metabolism and Enzyme Release Following Hypothermic Cardioplegia

Cardiac metabolism following hypothermic potassium cardioplegia was studied in 23 patients undergoing isolated aortic valve replacement. All had normal coronary arteries. Cardioplegia was induced by infusing 700-1 000 ml of cold Ringers acetate containing 20 mekv K+ selectively into the left coronary artery. Simultaneous blood samples were taken from the radial artery, a central vein and from the coronary sinus before and after cardioplegia. The PO2, O2-saturation and content, PCO2, pH, lactate, glucose, potassium, myoglobin, total creatine kinase (CK), its isoenzyme CK-MB, aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) were assessed. Before bypass lactate was extracted by the heart. During the initial 10 to 20 min after cardioplegia there was a marked release of lactate in the coronary sinus. Myoglobin concentration and CK-MB serum activity peaked during the first 4 hours after the release of the aortic cross-clamping. In order to determine the best indicator of myocardial damage after cardioplegia, duration of extracorporeal circulation (ECC-time), aortic occlusion time (AOT), mean myocardial temperature (MMT) and the product of AOT and MMT, referred to as time-temperature area (TTA), were related to possible indicators of myocardial injury, such as enzyme and myoglobin release. The TTA was the best way of expressing the degree of exposure of the heart to ischaemia. The CK-MB to peak area (CK-MB max area) was the best indicator of the degree of ischaemic injury sustained by the heart during operation.

Myocardial Protection During Aortic Valve Replacement: Effects of Mannitol in the Cardioplegia Solution on Cardiac Metabolism and Enzyme Release

Myocardial substrate metabolism and enzyme release following hypothermic potassium cardioplegia with and without the addition of mannitol in the cardioplegic solution were studied in two series of patients undergoing isolated aortic valve replacement. Measurements were made of PO2. O2-saturation and content, PCO2, pH, glucose, lactate, pyruvate, potassium, myoglobin, creatine kinase (CK), its isoenzyme MB and aspartate aminotransferase (ASAT) simultaneously in arterial and coronary sinus blood before cardioplegia and during the first 60 min after the release of aortic cross-clamping. In addition, myoglobin and enzymes were followed in peripheral venous blood for 72 hours after cardioplegia. Analysis of the results revealed no striking difference between the groups. Nevertheless, with the addition of mannitol, there was a slightly lower release of lactate and myoglobin probably indicating a more rapid metabolic recovery of the myocardium.

Serum creatine kinase (CK) activity after M-subunit inhibition in patients with atypical CK isoenzymes — a comparison to findings in acute myocardial infarction

The serum levels of total creatine kinase (CK), and of CK-B, as estimated by the enzymatic anti-M-subunit immunoinhibition method, were studied in 14 patients with CK-B elevation associated with advanced malignant disease, in nine subjects with electrophoretically verified, immunoglobulin-bound CK-BB (macro CK) and in 28 patients with acute myocardial infarction (AMI). The range of CK-B activity was similar in all three groups. In AMI, the ratio CK-B/total CK at peak CK-B was less than 13% (mean 7%). In both the groups with atypical CK, the ratios varied from about 30% to nearly 100%, with a mean amounting to 2/3 of total CK activity. CK-B elevations in patients with untreated malignant tumours tended to increase with time, but occasionally remained fairly constant for months, like those in subjects with macro CK. Complementary CK isoenzyme separation, e.g. by electrophoresis, is needed to differentiate conditions with atypical CK activity, detected by routine use of CK-B determinations in the diagnosis of AMI.

Myocardial Protection During Aortic Valve Replacement: Comparison Between Sanguineous and Asanguineous Cardioplegic Solutions

Myocardial substrate metabolism and enzyme release following hypothermic potassium cardioplegia were studied in two series of patients undergoing isolated aortic valve replacement. In 15 patients blood was used as cardioplegia vehicle (blood cardioplegia group) and a plain electrolyte solution was used in a control group of 17 patients. Simultaneous blood samples were drawn from arterial and coronary sinus blood before and during the first 60 min after release of aortic cross-clamping. Blood samples were analyzed for PO2. O2-saturation and content, PCO2, pH, lactate, pyruvate, glucose, potassium, myoglobin, creatine kinase (CK), its isoenzyme MB and aspartate aminotransferase (ASAT). In addition, myoglobin and enzymes were followed in peripheral venous blood for 48 hours. The pattern of metabolic changes after cardioplegia was similar in both groups, but some differences were encountered in the degree of the changes in potassium, myoglobin and CK-MB between the groups. The differences were nevertheless small and cell damage was probably of reversible nature in all patients, but the myocardial protection afforded by single dose blood cardioplegia was not unquestionably better than that of the control group.