Evaluation of myocardial damage during coronary artery grafting with serial determinations of serum CPK MB isoenzyme

The comparison and validity of troponin I assay systems in diagnosing myocardial ischemic injury after surgical coronary revascularization

OBJECTIVE

A prospective observational study was conducted to test the agreement between 2 commercially available automated cardiac troponin-I immunoassay systems (Opus Plus, Behring Diagnostics UK Ltd, Hounslow, UK; AxSYM, Abbott Laboratories, Abbott Park, IL) and to determine a normal reference range and threshold value indicative of perioperative myocardial infarction (PMI) after elective coronary artery bypass graft (CABG) surgery for the Opus Plus system.

DESIGN

Prospective, observational study. Setting : Single institution, cardiothoracic specialty hospital.

PARTICIPANTS

Seventy patients undergoing elective CABG surgery.

INTERVENTIONS

After institutional review board approval, patients received standardized anesthetic, surgical, and myocardial preservation techniques. Serial electrocardiographs, creatine kinase-MB, troponin-I, and perioperative outcome data were collected. Correlation between the immunoassay systems was tested using 124 duplicate samples from the first 18 patients. The normal reference range and threshold value indicative of PMI were tested for the Opus Plus system using duplicate samples from all 70 patients.

MEASUREMENTS AND MAIN RESULTS

Peak troponin-I concentrations (median [interquartile range]) differed significantly when measured by the Opus Plus and AxSYM immunoassay systems (5.61 [3.20-22.35] microg/L v 46.50 [14.55-70.95] microg/L, respectively; p < 0.001). There was clear proportional bias that was corrected with log transformation of the raw data. By using confidence interval and receiver operating characteristic curve analysis, the authors showed that a value > or =15 mug/L was indicative of PMI (Opus Plus system) and accordingly report a 35.7% (2.9% Q-wave) overall incidence of PMI in this study population (n = 70).

CONCLUSIONS

These data highlight differences between commercially available troponin-I assay systems. The authors recommend that each institution establish a local reference range and threshold indicative of perioperative myocardial infarction for its specific patient population and assay system and provide sample methodology.

Coronary revascularization: a procedure in transition from on-pump to off-pump? The role of glucose-insulin-potassium revisited in a randomized, placebo-controlled study

OBJECTIVE

To investigate an optimized glucose-insulin-potassium (GIK) solution regimen as an alternate myocardial protective strategy in off-pump coronary artery bypass graft (OP-CAB) surgery and as a supplement to conventional coronary artery bypass graft (CABG) surgery using cardiopulmonary bypass (CPB).

DESIGN

Prospective, randomized, placebo-controlled.

SETTING

Single institution, cardiothoracic specialty hospital.

PARTICIPANTS

Forty-four patients scheduled for elective multivessel coronary artery surgery using either conventional CPB (n = 22) or OP-CAB techniques (n = 22).

INTERVENTIONS

Preischemic, ischemic, and postischemic administration of GIK solution was carried out, optimally dosed to ensure nonesterified fatty acid (NEFA) suppression, and supplemented with magnesium, a glycolytic enzymatic cofactor.

MEASUREMENTS AND MAIN RESULTS

GIK solution therapy reduced plasma NEFA levels (p < 0.001) in OP-CAB surgery and CPB groups but failed to affect the incidence of non-Q wave perioperative myocardial infarction, incidence of postoperative atrial fibrillation, incidence of postoperative infection, reduction in creatinine clearance, or duration of postoperative intensive care unit or hospital length of stay. After adjusting for GIK solution therapy, OP-CAB surgery resulted in significantly less ischemic injury (troponin I >15 microg/L, 19.0% v 91.3%; p = 0.0001) and reduced postoperative infections (14.3% v 43.5%; p = 0.049).

CONCLUSION

GIK solution therapy achieved NEFA suppression and an insignificant trend toward reduced biochemical parameters of ischemic injury in OP-CAB surgery and CPB groups, but no major clinical benefit (perioperative myocardial infarction, intensive care unit length of stay, or hospital length of stay) was shown after elective CABG surgery in low-risk patients. Compared with CPB, OP-CAB surgery significantly reduced ischemic injury and postoperative infections.

Predictors and outcomes of cardiac complications following elective coronary bypass grafting

Our objective was to determine the predictors of cardiac complications among a cohort of elective coronary artery bypass graft (CABG) surgery patients and to determine the relationship of such complications to subsequent quality of life and symptoms. A total of 248 patients were enrolled and 237 completed 6 month follow-up. The combined rate of both major and minor cardiac complications was 9.7% (n = 24). Patients in this study were evaluated preoperatively, monitored intraoperatively, followed immediately postoperatively and at 6 months. Major cardiac complications accounted for 3.6% (n = 9) and minor complications for 6% (n = 15). Using multivariable logistic regression analysis, the predictors of major cardiac complications were receiving diuretics preoperatively (p = .01) and increased time during cross-clamping (p = .006). At 6 months after surgery, 19% of the patients with postoperative cardiac complications experienced worsening of symptoms, in contrast to only 8% of those without cardiac complications (p = .03). We concluded that patients who were on preoperative diuretics and those who had longer cross-clamp times were at higher risk of cardiac complications. The majority of patients who had acute cardiac complications had improved function and symptoms at 6 months postoperatively.

Cardiac troponin I and Q-wave perioperative myocardial infarction after coronary artery bypass surgery

OBJECTIVE

To monitor cardiac troponin I (cTnI), a newly developed biochemical index for cardiac damage, in patients during and after coronary artery bypass surgery (CABS) to determine whether the measurement of the serum levels of this marker could be of value in formulating an early diagnosis of Q-wave perioperative myocardial infarction (PMI).

DESIGN

Prospective study with sequential measurements of biological markers in a selected surgical patient group.

SETTING

University research laboratory and general university hospital (Cardiac Surgery Unit and Anesthesiology and Reanimation Unit).

PATIENTS

Forty-two patients undergoing elective CABS without concomitant valvular replacement.

INTERVENTIONS

There were no interventions required for this study. However, patients entered into the study had CABS, sequential arterial blood samples, ECG recordings, and echocardiograms performed.

MEASUREMENTS AND MAIN RESULTS

Pre-, intra-, and postoperative (up to 48 hrs) measurements of cardiac troponin I, MB-CK, and total creatine kinase, as well as serial electrocardiograms and echocardiograms. Perioperative infarction was assessed as the development of new persistent regional wall motion abnormalities in echocardiography together with electrocardiographic alterations and MB-CK increases. Eight patients had Q-wave PMI. All PMI patients had elevated peak cTnI values (all >9.2 ng/mL), whereas the 34 nonPMI patients had peak values <9.0 ng/mL; therefore, sensitivity and specificity (with a 9.0 ng/mL cut-off value) are 100%. MB-CK measurement peak values did not demonstrate such a high specificity and sensitivity.

CONCLUSIONS

Because of its high specificity and sensitivity, serial measurements of cTnI provide a rapid and accurate method for confirming or excluding the diagnosis of perioperative myocardial injury. cTnI evaluation can therefore be used both as an independent prognostic marker for patients undergoing cardiac surgery and as a powerful tool for detecting smaller PMIs often missed with standard PMI diagnostic criteria.

Cardiac troponin T: a new marker of myocardial tissue damage in bypass surgery

The purpose of this study was to evaluate cardiac troponin T (TnT) in the diagnosis of minor perioperative myocardial tissue damage and small myocardial infarctions during aortocoronary bypass surgery. In 15 patients without enzymatic or electrocardiographic signs of perioperative myocardial ischemia (group 1, uncomplicated bypass surgery), TnT did not exceed 3.55 micrograms/L. In 3 patients with perioperative non-Q-wave infarctions (group 2), TnT was significantly higher than in group 1 patients. In all 3 patients, TnT peak concentrations exceeded 3.5 micrograms/L. Thirteen patients (group 3, borderline cases) showed either signs of perioperative myocardial ischemia by creatine kinase isoenzyme MB (CKMB) activity levels (CKMB > 20 U/L on the first postoperative day, 3 patients) or by electrocardiography (new ST-T segment alterations, 10 patients). TnT concentrations were comparable to group 1 patients and indicated uncomplicated bypass surgery in all 3 patients with solely elevated CKMB activities. On the other hand, TnT concentrations in 3 patients with electrocardiographic signs of perioperative myocardial ischemia were significantly higher than in uncomplicated patients (group 1) with peak values exceeding 3.5 micrograms/L. Thus, TnT indicated perioperative non-Q-wave infarctions not detected by CKMB activity in these 3 patients. These results are in accordance with findings in nonsurgical patients. They suggest a higher sensitivity and specificity of cardiac TnT compared to CKMB activity in the diagnosis of small perioperative myocardial infarctions after bypass surgery.

Activities of mitochondrial aspartate aminotransferase and creatine kinase isoenzyme MB in serum following coronary bypass surgery

The mitochondrial isoenzyme of aspartate aminotransferase showed only slight increases in serum of twenty-seven patients after uncomplicated coronary bypass surgery, which contrasted the rapid and substantial increases in creatine kinase MB. In seven patients suffering perioperative infarction or serious complications, substantial increases in mitochondrial aspartate aminotransferase were detected and the elevations in creatine kinase MB were prolonged. Mitochondrial aspartate aminotransferase may appear as a specific marker of myocardial necrosis following coronary bypass surgery. The elevations of creatine kinase and creatine kinase MB were detected as early as 5 minutes after onset of coronary reperfusion and slightly higher activities were measured in coronary sinus blood than in systemic blood sampled simultaneously. Increases in mitochondrial aspartate aminotransferase, however, could first be measured 8 hours after reperfusion.

Effect of hyaluronidase on mortality and morbidity in patients with early peaking of plasma creatine kinase MB and non-transmural ischaemia. Multicentre investigation for the limitation of infarct size (MILIS)

A multicentred, randomised, blind study was started in 1978 to compare propranolol or hyaluronidase with placebo in patients with acute myocardial infarction admitted within 18 hours of onset of symptoms. Patients were randomised to group A and received hyaluronidase, propranolol, or placebo, or, if propranolol was contraindicated, to group B and received hyaluronidase or placebo. Hyaluronidase (500 U/kg given every six hours for 48 hours) had no effect on mortality or infarct size in the overall population. Because spontaneous reperfusion was more common in patients with early peaking of plasma creatine kinase MB or non-transmural electrocardiographic changes or both, the results were reanalysed for two subgroups: those in whom plasma creatine kinase peaked less than 15 hours after the onset of symptoms (early peak, n = 184) and those with a peak greater than 15 h after the onset of symptoms (late peak, n = 546). The distribution of time to peak activity of creatine kinase MB was similar in the hyaluronidase and placebo groups. In the early peak patients who were given hyaluronidase (groups A and B) total mortality and cardiac-specific four year mortality were significantly lower. This was most pronounced in group B in which the total mortality was 45% and cardiovascular mortality was 47% less than in the placebo group. Similarly, mortality from cardiovascular disease in patients (groups A and B) with nontransmural ischaemia (ST-T changes) given hyaluronidase was significantly lower, with group B showing a 50% reduction. In the subsets of patients with late peaking of creatine kinase MB or those presenting with transmural electrocardiographic changes there was no difference in total mortality or deaths from cardiac disease between those given hyaluronidase and those given placebo. Hyaluronidase was associated with improved survival in patients with early peaking of plasma creatine kinase MB, suggesting the possibility of salvage of myocardium in patients who have early spontaneous reperfusion and possibly after therapeutic reperfusion.

Evaluation of increased serum creatine kinase as an indicator of irreversible myocardial damage in dogs

To evaluate the relationship between creatine kinase (CK) elevation and irreversible myocardial damage, a coronary artery branch was occluded for periods of 5 to 40 min in ten dogs. In five other dogs the coronary vessel was occluded for 480 min, and five dogs underwent the same operative procedure but without occlusion of the artery. The serum CK was monitored for 8 hours postoperatively in all dogs. Elevation of the CK levels occurred in all groups, but the area under the time-enzyme activity curve showed no statistically significant difference between the group with 480-min occlusion, in which transmural myocardial infarction occurred in all dogs, and the group with temporary occlusion, in which no infarction could be histologically or histochemically demonstrated. Contrastingly, a statistically significant difference was found between the group with temporary occlusion and the control group with no occlusion. The results suggest that CK elevation is of no value as an indicator of irreversible myocardial damage during heart surgery that involves temporary myocardial ischaemia.

Aprotinin does not add protective effect to cold cardioplegia during coronary artery bypass surgery

The effect of aprotinin on intraoperative and postoperative CK-MB and left ventricular contractility in terms of dp/dt response to atrial pacing up to 150 beats/min was studied in 20 patients randomized before aortocoronary bypass surgery to either aprotinin or placebo administration. Cold cardioplegia and topical deep hypothermia were used in both groups. No difference could be demonstrated between the aprotinin and the placebo group, and the authors therefore concluded that aprotinin does not add substantially to the protective effect of cold cardioplegia and deep topical hypothermia during aortocoronary bypass surgery.

Role of transient ischaemia and perioperative myocardial infarction in the genesis of new septal wall motion abnormalities after coronary bypass surgery

To evaluate the role of ischaemia in the genesis of new septal wall motion abnormalities after coronary artery bypass surgery 45 patients were studied by cross sectional echocardiography before and 8-10 days after operation. Regional left ventricular wall motion was classified as normal, hypokinetic, akinetic, or dyskinetic. Septal wall motion abnormalities were correlated with electrocardiographic Q wave changes and serial serum MB creatine kinase measured before and 4, 7, 21, 48, and 72 hours after operation. Of the 14 patients who developed new septal wall motion abnormalities after operation two developed septal akinesis (both had perioperative infarction) and one new dyskinesis in the previously akinetic septal segment. Of the 11 patients with new septal hypokinesis, eight had normal serial creatine kinase MB values, two had raised values peaking four and seven hours after operation, with a return to normal values at 21 hours indicating transient ischaemia, and one had enzymatic criteria for perioperative infarction. Most new echocardiographic septal wall motion abnormalities after coronary artery bypass grafting are not caused by transient ischaemia, perioperative infarction, or generalised cell necrosis.

Intraoperative myocardial protection: a comparison of blood and asanguineous cardioplegia

Cardiac arrest was achieved in 84 patients using asanguineous cardioplegia and in 97 patients using cold blood potassium cardioplegia. The patient groups were similar in age, sex ratio, and preoperative risk factors. Other than the cardioplegic solution used, the conduct of each operation was identical. There were no differences in mean total pump time (118 minutes for the asanguineous cardioplegia group versus 117 minutes for the cold blood cardioplegia group) or cross-clamp time (73.5 versus 70 minutes, respectively). However, the blood cardioplegia group had a greater number of distal anastomoses per patient (3.9 versus 3.7; p less than 0.05). Myocardial protection was assessed clinically and by serial electrocardiograms. Cellular integrity was determined by release of the myocardial isoenzyme of serum creatine kinase (CK-MB). Cellular morphology was studied in 6 randomly selected patients in each group by electron microscopic examination of left ventricular myocardial samples obtained before and after bypass. Three patients given blood cardioplegia and 5 given asanguineous cardioplegia required intraaortic balloon counterpulsation at termination of bypass. There were no ultrastructural changes in either group. Electrocardiographic changes (Minnesota code) occurred in 12 of 84 patients receiving asanguineous cardioplegia versus 12 of 97 patients receiving cold blood potassium cardioplegia. To maintain a satisfactory cardiac index (greater than 2.0 L/min/m2), 38 of 84 patients given asanguineous cardioplegia versus 25 of 97 patients given blood cardioplegia required inotropic support up to 24 hours postoperatively (p less than 0.05). Infarct size determined from CK-MB release was significantly greater (p less than 0.05) in patients given asanguineous cardioplegia (36.27 gm-equivalents) than in those given blood cardioplegia (26.7 gm-equivalents).(ABSTRACT TRUNCATED AT 250 WORDS)

Interpretation of changes in the activity of creatine kinase MB isoenzyme in serum after coronary artery bypass grafting

Measurement of CK-MB in the sera of patients undergoing coronary artery bypass grafting shows a significant increase above pre-operative levels in all cases. However, the timing of the peak post-operative activity and its level allow criteria to be proposed which differentiate between two classes of patients: those with myocardial infarction or lesser myocardial damage, in whom peak activities are seen in specimens taken 21 hours after operation; and those in whom peak activities are found in specimens taken 4-7 hours after operation, presumably reflecting reversible myocardial changes. Activity peaks of more than 50 U/l occurring at 21 hours are considered to support a diagnosis of myocardial infarction.

Myocardial infarction in patients with previous coronary artery bypass surgery

An increasing proportion of patients hospitalized with myocardial infarction have previously undergone coronary artery bypass surgery. To define this subgroup, 77 patients with acute infarction occurring 2 or more months (mean 52.8) after bypass surgery were compared with 77 control patients with infarction. Baseline characteristics of the groups were similar except that post-bypass patients were more often men (p = 0.02) and more likely to have had a previous infarction (37 versus 21, p = 0.008). Infarct size was smaller in the post-bypass group as assessed by peak creatine kinase (CK), peak CK-MB, maximal number of electrocardiographic leads with ST elevation, maximal summed ST elevation and QRS score measured 7 to 10 days after admission (p less than 0.001 for each variable). Five control patients but none of the post-bypass patients died in the hospital (p = 0.06). Serious complications (death, acute heart failure, ventricular fibrillation, second or third degree atrioventricular block) occurred in 24 control patients but in only 5 post-bypass patients (p less than 0.001). Angiography was performed after infarction in 45 of the 77 post-bypass patients. Occlusion of both a native coronary artery and its graft was found in 24 of the 45; these patients had had higher peak CK levels (p = 0.008) than the other 21 patients who had angiography. The probable causes of infarction in these 21 were disease progression in nonbypassed arteries or graft occlusion with arterial stenosis, or vice versa, and disease progression distal to a patent graft.(ABSTRACT TRUNCATED AT 250 WORDS)

Graft patency in patients with coronary artery bypass operation complicated by perioperative myocardial infarction

Coronary artery bypass graft patency was examined by contrast-enhanced computed tomography in 18 patients with perioperative myocardial infarction soon after surgery to determine the role of graft occlusion. Preoperative coronary angiograms were reviewed to assess native coronary disease and visible collateral channels in the distribution of the myocardial infarction. Perioperative myocardial infarction was diagnosed if creatine kinase-MB was elevated, characteristic electrocardiographic changes occurred and, in the majority of cases, the pyrophosphate scan was positive. Fourteen patients (78%) had patent grafts and perioperative myocardial infarction in the distribution of the grafted vessel. Four patients had an occluded graft with infarction in the distribution of the grafted vessel. Among the 14 patients with patent grafts, there was a significant difference (p less than 0.0005) in the degree of the mean (+/- standard deviation) diameter stenosis of 80 +/- 11% in native coronary vessels supplying the perioperatively infarcted myocardium versus a 55 +/- 12% mean diameter stenosis in the 23 bypassed native coronary vessels supplying noninfarcted myocardium. It is concluded that the majority of perioperative myocardial infarcts associated with coronary artery bypass operations are not caused by graft occlusion. The severity of coronary obstruction in the grafted vessel and the lack of collateral vessels to the region of perioperative infarction in patients with patent grafts suggests that an island of jeopardized myocardium exists that is subject to inadequate intraoperative preservation.

The enzymology of skeletal muscle disorders

In myopathic disorders, abnormal serum enzyme activities are seen primarily in diseases of skeletal muscle where the condition involves the muscle fibers themselves. In denervation myopathies, serum enzyme activities are usually normal. The most dramatic increases of serum enzymes, particularly creatine kinase, are found in the dystrophic diseases, particularly Duchenne dystrophy. A review is given here of the many causes of abnormal serum enzyme activities where the source of enzymes is believed to be skeletal muscle. These include the dystrophies, various types of trauma, exercise, drug- and poison-induced causes including alcohol, malignant hyperthermia, inflammatory diseases, and miscellaneous causes. Tissue and serum activities are summarized for the commonly performed serum enzymes, i.e., CK, LD, AST, and aldolase. An extensive tabular and current description of the various types of dystrophies is given along with serum CK and pyruvate kinase activities.

The definition of myocardial infarction during aortocoronary bypass surgery

In a study of 392 aortocoronary bypass (CABG) patients, we found 16 patients with a postoperative new Q wave, 29 patients with new intraventricular conduction disturbance, 17 patients with cardiogenic shock, and 14 patients with excessive CK-MB activity. Those criteria were considered as diagnostic of perioperative acute myocardial infarction (AMI). Listing the 392 patients in a Venn diagram: five patients had three positive criteria, eight had two, 43 had one, and 336 had none. Ventricular arrhythmia, supraventricular arrhythmia, or ST-T changes occurred in decreasing frequency in patients with a decreasing number of positive criteria. Five patients died postoperatively and in four a postmortem examination was available. Diagnostic criteria partly predicted autopsy findings. We conclude that the diagnostic criteria of perioperative myocardial infarction have a low diagnostic performance.

Changes in left ventricular performance related to perioperative myocardial infarction in coronary artery bypass graft surgery

Strict electrocardiographic, enzymatic, scintigraphic, and hemodynamic criteria for perioperative myocardial infarction (MI) were defined and related to serial assessments of left ventricular performance during rest and exercise in patients seen early and late after coronary artery bypass graft operation. Global left ventricular performance was determined by radionuclide ventriculography from which changes in the pattern of serial postoperative ejection fractions (EF) were obtained. Patients were divided into two groups based on the presence or absence of perioperative MI, and were matched in pairs on the basis of preoperative EF and extent as well as location of coronary artery obstructions. The results indicate that neither short- nor long-term depression in resting EF occurred subsequent to perioperative MI. However, an exercise-related increase in EF eight months postoperatively was depressed in patients who had perioperative MI compared with those who did not. Patients with new Q waves and abnormal postoperative elevation in serum levels of the myocardial isoenzyme of creatine kinase (CK-MB) had a greater early decrease in EF compared with patients without evidence of perioperative MI. However, seven days after operation, the EF in both groups returned to preoperative levels. Patients with abnormal technetium 99m-pyrophosphate scintigrams had changes in perioperative EF similar to those in patients without MI. The presence of low cardiac output syndrome immediately after operation was associated with immediate and short-term decreases in EF, which were not seen in any of the other patient subgroups.

CK isoenzymes and transaminases after coronary cardiography, cardiac surgery and non-cardiac thoracotomy

The diagnosis of a heart infarct in the early postoperative period is often difficult. In the present study, the levels of serum CK, its isoenzymes (MM, MB and BB), aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) were followed up after coronary arteriography (12 patients), cardiac surgery (23 patients) and non-cardiac thoracotomy (28 patients). Elevation of MB was not detected after coronary arteriography, except in two patients, who had had even before the examination a mildly positive MB finding and electrocardiographic changes indicative of subendocardial infarction. After cardiac surgery the MB findings were positive in all but two patients, who had undergone aortic valve surgery. However, the average MB level was lower than in the 10 heart infarct patients who served as controls. After non-cardiac thoracotomy, six patients had a positive serum MB, but the value of MB was quite low as compared with values after cardiac surgery and nearly insignificant in terms of heart infarct diagnosis.

Myocardial protective effect of maintained beta-blockade in aorto-coronary bypass surgery

Twenty-nine patients were randomly allocated to two groups before undergoing aorto-coronary bypass surgery. In one group the beta-blocking medication was withdrawn three days preoperatively, and in the other group it was maintained. The patients in the latter group were additionally given 100 mg metoprolol per os two hours before surgery. The degree of myocardial injury, as judged from cumulated activity of S-CK B, was less when the beta-blockade was maintained.

Multicentre investigation of myocardial protection with cold cardioplegia

In order to analyze factors of importance for the efficiency of myocardial protection during open-heart surgery, a study was made of 144 patients undergoing isolated aortic valve replacement with various cardioplegic techniques. The cardioplegia was of Bretschneider type in 54 cases, St Thomas in 31 and Ringer-potassium type in 11 cases. Single or multi-dose blood cardioplegia was used in 11 cases and continuous blood cardioplegia in 30 cases. Local cardiac hypothermia was additionally employed in all patients. The efficiency of myocardial protection was assessed mainly from the incidence of postoperative conduction disturbances, myocardial enzyme release and need for inotropic support. All patients survived the operation. In 20% surgery was followed by transient or persistent disturbance of conduction, in 9% by abnormally increased CK-MB release and in 5% by requirement for inotropic support. Preoperative risk factors such as high age or severe left ventricular (LV) hypertrophy or dysfunction had little influence on the results. Patients in whom aortic stenosis (AS) was dominant in the complex with aortic insufficiency (AS + AI) showed 20-hour postoperative CK-MB enzyme activity twice as high as those with pure aortic insufficiency. The most important factors in myocardial protection were the duration of aortic occlusion and the myocardial temperature during cardioplegia. When the aortic occlusion lasted more than 80 min there was a 32% incidence of conduction disturbances and 20-hour CK-MB activity thrice as high as after shorter occlusion. Patients with mean myocardial temperature below 18 degrees C during cardioplegia invariably had low enzyme activities, which indicated good myocardial protection. The best overall results were obtained in patients operated on during hypothermia at 25-27 degrees C, with single or multi-dose blood cardioplegia and with efficient local cooling of the heart.

Mechanism of reperfusion arrhythmia prostaglandin as a washout metabolite

This study was designed to clarify the mechanism of reperfusion arrhythmia. In the mongrel dogs, the left anterior descending coronary artery was occluded for 15 min and then the ligation was released. The dogs were divided into two groups: one was the control group, and the other the indomethacin group in which indomethacin, an inhibitor of prostaglandin (PG) biosynthesis, was premedicated at 30 min before ligation. The ventricular multiple response threshold (VMRT), and plasma levels of K+, PG E and PG F2 alpha were measured in the great cardiac vein before and during occlusion, and after reperfusion. In the control group, during occlusion, VMRT decreased and did not return to normal soon after reperfusion. The levels of PG E and PG F2 alpha in the great cardiac vein did not change significantly during occlusion; however, PG E became significantly elevated after reperfusion. In the indomethacin group, the time course of VMRT was essentially similar to that of the control group during occlusion; however, lowering of VMRT after reperfusion was prevented significantly. The PG F2 alpha level in the great cardiac vein did not elevate after reperfusion or during occlusion. In both groups, the level of K+ in the great cardiac vein was elevated during occlusion, but rapidly decreased to normal after reperfusion. These results suggest that PG E, as a washout metabolite, is a key factor in evoking reperfusion arrhythmia.

Myocardial protection through cold cardioplegia with potassium or diltiazem. Experimental evidence that diltiazem provides better protection even when coronary flow is impaired by a critical stenosis

Intermittent aortic root infusion of a cold solution containing either potassium chloride (KCl) or diltiazem was performed in 32 dogs during a 2-hour aortic clamping. Half of the dogs in each group had a critical stenosis created on the circumflex artery before cardiopulmonary bypass. Global left ventricular (LV) function was determined 1 hour after bypass by means of LV pressure, peak dP/dt, LV end-diastolic pressure, cardiac and stroke work indexes. Regional function was assessed through microcrystals in the areas of the circumflex and left anterior descending coronary arteries. LV pressure decreased in all dogs, but more so with the KCl solution (p = 0.02). The stenosis had no specific effect on LV pressure, but affected peak positive dP/dt (p = 0.007) and LV end-diastolic pressure (p less than 0.0001). Cardiac and stroke work indexes decreased more in the KCl group than in the diltiazem group (p less than 0.002) with or without stenosis. Both positive and negative dP/dt were affected by the type of solution (a greater decrease with KCl), but the narrowing affected only the positive dP/dt. Regional LV function remained unchanged in the absence of a narrowing and was depressed equally in dogs with a narrowing whether they received KCl or diltiazem. Overall LV function appeared to be better preserved with diltiazem, with or without impairment of circumflex flow.

Myocardial protection during aortocoronary bypass operations. Comparison of two different operative procedures: cold chemical cardioplegia versus intermittent cross-clamping of the aorta

Myocardial injury was studied in 40 randomized coronary patients operated on electively with coronary bypass grafting using two different techniques, (A) cardioplegic arrest and continuous cross-clamping of aorta, and (B) ischaemic arrest and intermittent cross-clamping of aorta. The released quantity of the MB isoenzyme of creatine kinase was used as an indicator of myocardial injury. Of the whole group, 3 patients (8%) suffered a myocardial infarction as judged by ECG. The CK-MB release was not significantly different in the two groups. The total period of aortic cross-clamping was markedly longer in the cardioplegic group than in the intermittent clamping group. A significant correlation between the duration of aortic clamping and the amount of CK-MB release was found in the cardioplegic group. Our results indicate that the beneficial effects of cardioplegic arrest are outweighed by an unavoidable longer period of total aortic clamping as compared with the intermittent clamping technique.

Myocardial protection during aortic valve replacement

Peri-operative myocardial damage during aortic valve replacement is evaluated by analysis of S-GOT and LDH in the early postoperative phase. Combining the mortality figures and enzyme changes postoperatively, it is demonstrated that the peri-operative myocardial damage is significantly lower in the group operated on under cold cardioplegia a.m. Bretschneider, than in the group operated on under normothermia or moderate hypothermia and induced ventricular fibrillation.

Serum CK-MB activity during and after aortocoronary bypass surgery

Frequent serum sampling of CK-MB and total CK levels was carried out in 100 patients during and up to 48 hours following aortocoronary bypass surgery. Using an ion exchange chromatography method for CK-MB determination, significantly higher serum CK-MB levels (peak 46.1 +/- 5.2 cf. 31.3 +/- 2.2 u/L), but not total CK levels were present 6 to 16 hours postoperatively in those with new Q waves in the ECG. Serum levels of CK-MB in those patients with uncomplicated surgery were defined. New post-operative Q waves were seen in only one half of cases with frankly abnormal CK-MB curves and seriously underestimated the incidence of perioperative infarction. Peak levels of CK-MB in patients with new Q waves occurred within 16 hours of surgery suggesting that infarction is usually an intraoperative or early post-operative event.

Myocardial injury and CK-MB release during aortic valve surgery with selective coronary perfusion

The postoperative serum activity of creatine kinase MB isoenzyme (CK-MB) was studied in 25 patients undergoing isolated aortic valve replacement (Björk-Shiley prosthesis). Hypothermia at 30 degrees C and selective coronary perfusion (CP) were used for myocardial protection. Repeated electrocardiograms revealed no signs of perioperative myocardial infarction. In all patients, CK-MB was detected in the serum. The CK-MB as a percentage of total CK at peak CK-MB [12 +/- 1 (mean +/- SEM)] was of the same magnitude as that found in acute myocardial infarction (AMI). Peak CK-MB occurred 2 +/- 0 h after the end of surgery. Peak total CK occurred after 17 +/- 3 h, and the plasma half-life for total CK was three times that of CK-MB. Thus, the kinetics of serum CK differed from those in AMI, but were similar to those reported after coronary bypass operations. The release of CK-MB, as well as of asparatate aminotransferase and thermostable lactate dehydrogenase, was related to the duration of aortic cross-clamping (AC), with a marked increase after 90 min. In two subgroups with similar AC time, postoperative CK-MB activity was higher in the subgroup with longer CP, indicating that CP as a method of myocardial protection may be entirely beneficial.

The origin of creatine kanase BB occurring in serum during aortocoronary bypass surgery

The serum concentration of creatine kinase (CK)-BB during and after coronary bypass surgery was measured by a sensitive and highly specific radioimmunoassay technique. All patients showed a distinct and temporary increase in CK-BB concentration shortly after the start of operation. Our results indicate that this increase has no connection with damage of the heart or the brain. Most probably the BB isoenzyme is liberated mainly from the saphenous vein as a consequence of the surgical manipulations during the heart operation.

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.

Improved oxygen delivery to the myocardium during hypothermia by perfusion with 2,3 DPG-enriched red blood cells

The oxygen affinity of red cells increases stepwise with temperature reductions below 37 degrees C. In vitro studies demonstrated that biochemically modified red cells with increased 2,3 diphosphoglycerate (2,3 DPG) (150% and 250% of normal) exhibited significantly less oxygen affinity at 24 degrees C than did unmodified cells. At 15 degrees C, significant attenuation of affinity was observed with 250%, but not 150%, of normal 2,3 DPG cells. Measurements made of isolated fibrillating dog hearts during perfusion at 24 degrees C alternately with unmodified (80% of normal 2,3 DPG) and modified (300% of normal 2,3 DPG) red cells demonstrated significantly greater oxygen consumption, higher coronary sinus partial pressures of oxygen and carbon dioxide, higher in vitro P50 values, and lower arterial and coronary sinus lactate levels during perfusion with modified as compared with unmodified cells. This evidence, indicating improved oxygen delivery to hypothermic dog hearts by red cells with 300% of normal 2,3 DPG activity, suggests that high 2,3 DPG cells might protect myocardial tissue in patients undergoing hypothermic cardiac operation.

MB creatine kinase and the evaluation of myocardial injury following aortocoronary bypass operation

Myocardial injury was studied in 104 patients undergoing coronary artery grafting without cold chemical cardioplegia using the quantity of the isoenzyme MB of the creatine kinase liberated as an indicator. This method of evaluation, which is said to permit comparison of different techniques of myocardial protection, allowed us to consider the relative importance of several factors believed to have an influence on intraoperative myocardial injury. Indices of significance were duration of symptoms before operation, presence of chronic arterial hypertension, and the type of antiangina treatment employed. Other operative factors included severity of the arterial lesions, number of anastomoses performed, and duration of extracorporeal circulation and of aortic cross-clamping.

The importance of monitoring intramyocardial temperature during hypothermic myocardial protection

In 50 patients undergoing cardiac operation, hypothermic cardioplegic solution was infused into the root of the aorta immediately after aortic cross-clamping. Cardiac standstill was achieved within 1 to 3 minutes. However, monitoring of intramyocardial temperature with a needle thermistor revealed that such core cooling is unpredictable (the intramyocardial temperature achieved ranged from 7 degrees to 33 degrees C), unstable (this temperature can rise at more than 0.5 degrees C per minute), and uneven (a difference of up to 17 degrees C was observed between the intramyocardial temperature of the anterior and posterior left ventricular sites). The area supplied by the stenotic coronary artery was least protected. Monitoring of intramyocardial temperature enables one to know when supplementary cooling is indicated. We conclude that widespread differences in this temperature during cardiac operation make monitoring advisable for optimal myocardial protection.