The predictive value of serum enzymes for perioperative myocardial infarction after cardiac operations

Cardiac markers following cardiac surgery and percutaneous coronary intervention

Differentiation between procedure-related necrosis and postprocedural myocardial infarction (MI) is challenging because of the inherent association of these procedures to varying levels of myocardial injury. To improve risk stratification of patients at risk of an acute MI, the universal definition of MI implemented cardiac biomarker thresholds. The cutoff points for these thresholds, however, are largely arbitrary and lack therapeutic implications. Measurement of cardiac marker concentrations after percutaneous coronary intervention and cardiac surgery should, therefore, be used as a marker of baseline risk, atherosclerosis burden, and procedural complexity rather than a conclusive marker to diagnose acute MI.

[Haemorrhage and morbidity associated with the use of tranexamic acid in cardiac surgery: a retrospective, multicentre cohort study]

INTRODUCTION

Postoperative bleeding is common complication, affecting up to 20% of patients, after cardiac bypass surgery. Fibrinolysis is one of the causes of this excessive bleeding, and for this reason the use of tranexamic acid is recommended. The problem with using this is that there are numerous guidelines and differences in the dose to be administered. Our aim was to evaluate whether there were any differences in postoperative bleeding and morbidity after cardiac surgery with the administering of different tranexamic acid doses in three university hospitals.

MATERIAL AND METHODS

A retrospective, multicentre cohort study was conducted. A total of 146 patients who were subjected to elective cardiac bypass surgery according to the anaesthetic-surgical protocol of each hospital were included in the study. The clinical histories were reviewed, and they were divided into two groups according to the tranexamic acid dose: Group A (high doses), initial dose of 20mg/kg and continuous infusion of 4 mg/kg/hour until closure of the sternotomy. A further 100mg was added to prime the bypass machine. Group B (low doses), initial dose of 10mg/kg followed by a continuous infusion of 2mg/kg/hour until closure of the sternotomy. A further 50mg was added to prime the bypass machine. Variables, such as age, sex, weight, height, type of surgical procedure (valvular, coronary or mixed), haematocrit, INR, and preoperative platelet count, time and temperature of the bypass machine, and haematocrit on sternum closure, were recorded. Among the post-operative variables collected were: debit due to drainage at 6, 12 and 24 hours after surgery, number and type of blood products transfused in the first 24 hours, need for further surgery due to haemorrhage, CVA, TIA, or a new acute myocardial infarction, convulsions, and mortality.

RESULTS

The incidence of increased bleeding (patients in the 90 percentile) was higher in Group B at all the study evaluation times (P<.05). The incidence of further surgery due to bleeding, and the need for transfusion of ≥ 3 units of packed red cells was lower in Group A (5.56%) than in Group B (13.89%). There were no significant differences in the requirements for blood products transfusions between the groups. As regards associated morbidity, there was one isolated case of convulsion and a perioperative AMI in another case in Group A, and three cases of perioperative AMI in Group B.

CONCLUSIONS

Elevated doses of tranexamic acid in cardiac bypass surgery appear to significantly reduce bleeding in the first hours after surgery compared to low doses. However, this decrease did not lead to a reduction in the needs for blood products.

The clinical significance of cardiac troponins in medical practice

Troponins are regulatory proteins that form the cornerstone of muscle contraction. The amino acid sequences of cardiac troponins differentiate them from that of skeletal muscles, allowing for the development of monoclonal antibody-based assay of troponin I (TnI) and troponin T (TnT). Along with the patient history, physical examination and electrocardiography, the measurement of highly sensitive and specific cardiac troponin has supplanted the former gold standard biomarker (creatine kinase-MB) to detect myocardial damage and estimate the prognosis of patients with ischemic heart disease. The current guidelines for the diagnosis of non-ST segment elevation myocardial infarction are largely based on an elevated troponin level. The implementation of these new guidelines in clinical practice has led to a substantial increase in the frequency of myocardial infarction diagnosis. Automated assays using cardiac-specific monoclonal antibodies to cardiac TnI and TnT are commercially available. They play a major role in the evaluation of myocardial injury and prediction of cardiovascular outcome in cardiac and non-cardiac causes. In this review we discuss the clinical applications of cardiac troponins and the interpretation of elevated levels in the context of various clinical settings.

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.

Impact of pexelizumab, an anti-C5 complement antibody, on total mortality and adverse cardiovascular outcomes in cardiac surgical patients undergoing cardiopulmonary bypass

BACKGROUND

During cardiac surgery requiring cardiopulmonary bypass, pro-inflammatory complement pathways are activated by exposure of blood to bio-incompatible surfaces of the extracorporeal circuit and reperfusion of ischemic organs. Complement activation promotes the generation of additional inflammatory mediators thereby exacerbating tissue injury. We examined the safety and efficacy of a C5 complement inhibitor for attenuating inflammation-mediated cardiovascular dysfunction in cardiac surgical patients undergoing cardiopulmonary bypass.

METHODS

Pexelizumab (Alexion Pharmaceuticals, Inc, Cheshire, CT), a recombinant, single-chain, anti-C5 monoclonal antibody, was evaluated in a randomized, double-blinded, placebo-controlled, multicenter trial that involved 914 patients undergoing coronary artery bypass grafting with or without valve surgery requiring cardiopulmonary bypass.

RESULTS

Pexelizumab was administered intravenously as a bolus (2.0 mg/kg) or bolus plus infusion (2.0 mg/kg plus 0.05 mg/kg/h for 24 hours), and inhibited complement activation. There were no statistically significant differences between placebo-treated and pexelizumab-treated patients in the primary endpoint (composite of death, or new Q-wave, or non-Q-wave [myocardial-specific isoform of creatine kinase > 60 ng/mL] myocardial infarction, or left ventricular dysfunction, or new central nervous system deficit). However, post hoc analysis revealed a reduction in the composite of death or myocardial infarction (myocardial-specific isoform of creatine kinase >/= 100 ng/mL) for the isolated coronary artery bypass grafting, bolus plus infusion subgroup on POD 4 (p = 0.007) and on POD 30 (p = 0.004).

CONCLUSIONS

Pexelizumab had no statistically significant effect on the primary endpoint. However, the reduction in death or myocardial infarction (myocardial-specific isoform of creatine kinase >/= 100 ng/mL) as revealed in the post hoc analysis in the isolated coronary artery bypass grafting bolus plus infusion subpopulation, suggests that further investigation of anti-C5 therapy for ameliorating complement-mediated inflammation and myocardial injury is warranted.

Intravasal microdialysis is superior to intramyocardial microdialysis in detecting local ischaemia in experimental porcine myocardial infarction

OBJECTIVE

A novel application of microdialysis was studied, where myocardial outflow of energy metabolites was monitored by intravasal microdialysis in the myocardial venous outflow during ischaemia and reperfusion. These levels where related to levels monitored by microdialysis catheters placed intramyocardially.

METHODS

Microdialysis catheters were introduced into the great cardiac vein (GCV), ischaemic myocardium and non-ischaemic myocardium in 10 anaesthetized pigs. The left anterior descending coronary artery was occluded for 60 min in five pigs and five pigs served as controls. Ischaemia was followed by 120 min of reperfusion. Microdialysis samples were analysed for glucose, lactate, pyruvate and glycerol. Venous lactate and glucose levels were measured by blood samples from the femoral vein.

RESULTS

All animals subjected to ischaemia developed myocardial infarction. Lactate, lactate/pyruvate ratio and glycerol increased in the microdialysis samples from the GCV and the catheter placed in ischaemic myocardium while no changes were detected in samples from the catheter placed in the non-ischaemic myocardium.

CONCLUSION

In this study, we have demonstrated that intravasal microdialysis catheters rapidly and reliably detect local myocardial ischaemia, while intramyocardially placed microdialysis catheters will not show these changes if placed in a non-ischaemic area.

Transmyocardial laser revascularization: epicardial ECG detection provides efficient R-wave triggering during mobilization of the heart

OBJECTIVE

In order to achieve an accurate intraoperative ECG detection, a new technique in detecting the trigger-signal was developed. In contrast to the traditional three-lead ECG-configuration, the left leg electrode was connected to a transient epicardial pacemaker electrode on the left-ventricular surface.

BACKGROUND DATA

The Holmium:YAG-Laser for Transmyocardial Laser Revascularization (TMLR) is R-wave-triggered, providing the release of energy only during the refractory period of the heart cycle. However, an exact ECG-triggering during mobilization of the apex and/or posterior wall is difficult to achieve by using conventional ECG-configuration, therefore increasing the risk for mistriggering and induction of arrhythmias during TMLR.

MATERIALS AND METHODS

Two groups of patients, all undergoing stand alone TMLR-procedures via left minithoracotomy, were compared. Ten patients were operated with the conventional ECG configuration (group 1) and ten patients with the modified epicardial ECG configuration (group 2).

RESULTS

In patients of group 1, as a result of a loss of the trigger signal or due to the triggering of artifacts, the incidence of correctly triggered QRS-complexes was 56% of all documented QRS-complexes. In contrast, an excellent triggering was observed in 98% (p < 0.001) in group 2, resulting in a reduction of laser operative time by 35% (p < 0.001) and a decrease in the incidence of intraoperative ventricular fibrillation (0 vs. 3).

CONCLUSION

In conclusion, this new ECG configuration is a simple but effective method in achieving an excellent ECG signal during all stages of TMLR. As a consequence, a reduction in operative time and incidence of ventricular fibrillation can be achieved.

Cardiac outflow of amino acids and purines during myocardial ischemia and reperfusion

A novel application of microdialysis was studied, in which myocardial outflow of amino acids and purines was monitored by intravasal microdialysis in the myocardial venous outflow during ischemia and reperfusion. Microdialysis catheters were introduced into the great cardiac vein, pulmonary artery, and external jugular vein in 20 anesthetized pigs. The left anterior descending artery was occluded in four groups of pigs for 0, 10, 15, and 60 min. Ischemia was followed by 120 min of reperfusion. Microdialysis samples were analyzed for taurine, aspartate, glutamate, hypoxanthine, inosine, and guanosine. Myocardial infarction developed when ischemia exceeded 10 min. Taurine, aspartate, inosine, and guanosine increased early in the great cardiac vein during ischemia. We found the outflow patterns of amino acids and purines to be graded in response to different lengths of ischemia. In this study we have demonstrated a graded outflow of amino acids and purines in response to ischemia and a positive correlation between infarct size and myocardial outflow of amino acids and purines. This could be of value in a clinical setting to quantify the extent of myocardial damage.

Serum cardiac troponin I after conventional and minimal invasive coronary artery bypass surgery

We evaluated myocardial release of cardiac troponin I (cTnI) in patients treated with conventional coronary artery bypass grafting (CABG), which employs extracorporeal circulation, and different kinds of minimal invasive coronary artery bypass grafting (MICABG), a surgical technique where the operation is performed without extra-corporeal circulation. Furthermore, we evaluated the usefulness of serum cTnI measurement to detect perioperative myocardial infarction (PMI) after coronary artery bypass surgery. Thirty-one patients were included: sixteen underwent CABG, fifteen underwent different MICABG and five patients had PMI. Blood specimens for cTnI measurements were collected up to 72 hours after opening the graft. Aortic cross-clamping time was a minor determinant of myocardial damage; on the other side, the trauma during surgery correlated with the number of involved arteries and with the manoeuvre employed to obtain heart dislocation, and appeared a more important determinant of myocardial damage. In patients with PMI, the cumulative release of cTnI was higher than in patients free from PMI; however, only after 24-72 hours we observed significant differences in serum cTnI values, because the increased perioperative values of cTnI complicated the interpretation of the myocardial status and a single cut-off could not be used to exclude PMI.

Total intravenous anesthesia with a propofol-ketamine combination during coronary artery surgery

OBJECTIVE

To evaluate the cardiovascular effects of a propofol-ketamine combination in patients undergoing coronary artery surgery.

DESIGN

Prospective, randomized study.

SETTING

Tertiary care teaching hospital, single center.

PARTICIPANTS

Seventy-eight adult patients.

INTERVENTIONS

Patients were randomly allocated to receive propofol-ketamine for induction and maintenance of anesthesia (n = 36) or fentanyl-enflurane (controls, n = 42).

MEASUREMENTS AND MAIN RESULTS

Hemodynamics and other variables were recorded during and after surgery and for 24 hours in the intensive care unit. Before cardiopulmonary bypass (CPB), there was similar incidence of treatment for hypotension (42% of patients in both groups), tachycardia (propofol-ketamine, 6%; controls, 5%), and myocardial ischemia (propofol-ketamine, 3%; controls, 12%). In the propofol-ketamine group, there was a decreased requirement for inotropic agents after CPB (22% of patients) compared with controls (49% of patients; p = 0.02). There was a reduced incidence of myocardial infarctions (creatine kinase myocardial band >133 U/L) in the propofol-ketamine group compared with the control group (0% v 14%; p = 0.02; Fisher's exact test). Patients in the propofol-ketamine group were more likely to have their tracheas extubated within 8 hours of arrival in the intensive care unit compared with controls (33% v 7%; p = 0.01; Cochran-Mantel-Haenzel test).

CONCLUSIONS

The propofol-ketamine combination was associated with a similar incidence of pre-CPB hypotension and ischemia, a decreased need for inotropes after CPB, an earlier time to tracheal extubation, and a reduced incidence of myocardial infarctions compared with controls.

Significance of right bundle branch block in the diagnosis of myocardial ischemia in patients undergoing coronary artery bypass grafting

BACKGROUND

Perioperative diagnosis of myocardial ischemia following cardiac surgical procedures remains a challenging problem. Particularly, the role of new conduction disturbances as markers of postoperative ischemia is still questionable. The goal of this study was to elucidate the diagnostic significance of new postoperative right bundle branch block (RBBB) for the detection of perioperative myocardial ischemia in patients undergoing elective coronary artery bypass grafting (CABG).

METHODS

In 169 consecutive patients, three-channel Holter monitoring and serial assessment of serum enzymes were performed for 48 h, and 12-lead ECG repeated for up to 5 days postoperatively. Postoperative events were classified as either myocardial infarction (MI), transient ischemic events (TIE) or various conduction disturbances.

RESULTS

Transient (n=9) or permanent (n=4) RBBB occurred in 13 patients (8%); 14 patients (8%) showed signs of perioperative MI and 18 patients (11%) evidence of TIE. Peak activity of creatine-kinase (CK, 561+/-135 vs. 316+/-19, P<0.05) and CK-MB (22.7+/-3.2 vs. 13.4+/-0.8, P<0.01) were higher in patients with RBBB than in patients without perioperative ischemic events. Peak CK-MB levels were significantly higher in patients with MI as compared to those with RBBB (33.4+/-7.6 vs. 22.7+/-3.2, P<0. 05). Patients with TIE had similar perioperative enzyme levels as patients with no events.

CONCLUSION

It is concluded that the combined assessment of repeated 12-lead ECG, continuous Holter monitoring and enzyme analysis allows a reliable diagnosis of perioperative myocardial ischemia and conduction disturbances. The occurrence of new RBBB following elective CABG is indicative of perioperative myocardial necrosis and thus serves as a valuable tool for the diagnosis of new, perioperative ischemic events.

Troponin levels in patients with myocardial infarction after coronary artery bypass grafting

BACKGROUND

The objective of this study was to evaluate serum cardiac troponin T and I levels in patients in whom electrocardiogram, myocardial scan, and serum CK-MB levels of the MB isoenzyme of creatine kinase indicated perioperative myocardial infarction (MI) after coronary artery bypass grafting (CABG).

METHODS

We studied 590 patients who underwent CABG at the Montreal Heart Institute between 1992 and 1996. Postoperative cardiac troponin T levels (493 patients), troponin I levels (97 patients), and activity of the MB isoenzyme of creatine kinase, electrocardiograms, clinical data, and clinical events were recorded prospectively. The diagnosis of perioperative PMI was defined by a new Q wave on the electrocardiogram, by serum levels of the MB isoenzyme of creatine kinase higher than 100 IU/L within 48 hours after operation, or both.

RESULTS

After CABG, 22 patients in whom troponin T levels (22/493, 4.5%) and 6 patients in whom troponin I levels (6/97, 6.2%) were measured had sustained a perioperative MI according to current diagnostic criteria. In these patients, troponin T levels higher than 3.4 microg/L 48 hours after CABG best detected the presence of perioperative MI, with an area under the receiver operating characteristic curve of 0.95, a sensitivity of 90%, a specificity of 94%, a positive predictive value of 41%, a negative predictive value of 99%, and a likelihood ratio of 15. Serum troponin I levels higher than 3.9 microg/L 24 hours after CABG confirmed the perioperative MI with an area under the receiver operating curve of 0.86, a sensitivity of 80%, a specificity of 85%, a positive predictive value of 24%, a negative predictive value of 99%, and a likelihood ratio of 5.

CONCLUSIONS

Serum troponin T levels higher than 3.4 microg/L 48 hours after CABG correlated best with the diagnosis of perioperative MI. Serum troponin T levels greater than 3.9 microg/L 24 hours after CABG also correlated with the diagnosis of perioperative MI, although a larger experience is needed to confirm the validity of the chosen cutoff value.

Pharmacology and biological efficacy of a recombinant, humanized, single-chain antibody C5 complement inhibitor in patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass (CPB) induces a systemic inflammatory response that causes substantial clinical morbidity. Activation of complement during CPB contributes significantly to this inflammatory process. We examined the capability of a novel therapeutic complement inhibitor to prevent pathological complement activation and tissue injury in patients undergoing CPB.

METHODS AND RESULTS

A humanized, recombinant, single-chain antibody specific for human C5, h5G1.1-scFv, was intravenously administered in 1 of 4 doses ranging from 0.2 to 2.0 mg/kg before CPB. h5G1.1-scFv was found to be safe and well tolerated. Pharmacokinetic analysis revealed a sustained half-life from 7.0 to 14.5 hours. Pharmacodynamic analysis demonstrated significant dose-dependent inhibition of complement hemolytic activity for up to 14 hours at 2 mg/kg. The generation of proinflammatory complement byproducts (sC5b-9) was effectively inhibited in a dose-dependent fashion. Leukocyte activation, as measured by surface expression of CD11b, was reduced (P<0.05) in patients who received 1 and 2 mg/kg. There was a 40% reduction in myocardial injury (creatine kinase-MB release, P=0.05) in patients who received 2 mg/kg. Sequential Mini-Mental State Examinations (MMSE) demonstrated an 80% reduction in new cognitive deficits (P<0.05) in patients treated with 2 mg/kg. Finally, there was a 1-U reduction in postoperative blood loss (P<0. 05) in patients who received 1 or 2 mg/kg.

CONCLUSIONS

A single-chain antibody specific for human C5 is a safe and effective inhibitor of pathological complement activation in patients undergoing CPB. In addition to significantly reducing sC5b-9 formation and leukocyte CD11b expression, C5 inhibition significantly attenuates postoperative myocardial injury, cognitive deficits, and blood loss. These data suggest that C5 inhibition may represent a novel therapeutic strategy for preventing complement-mediated inflammation and tissue injury.

Are electrocardiographic Q-wave criteria reliable for diagnosis of perioperative myocardial infarction after coronary surgery?

OBJECTIVE

A major assumption in cardiovascular medicine is that Q-waves on the electrocardiogram indicate major myocardial tissue damage. The appearance of a new Q-wave has therefore been considered the most reliable criterion for diagnosis of perioperative myocardial infarction (PMI) in cardiac surgery. In a study, originally intended to evaluate troponin-T as a marker of PMI, analysis of our data aroused the need to address the reliability of Q-wave criteria for diagnosis of PMI.

METHODS

In 302 consecutive patients undergoing coronary surgery, Q-wave and other electrocardiogram (ECG) criteria were compared with biochemical markers of myocardial injury and the postoperative course. All ECGs were analysed by a cardiologist blinded to the biochemical analyses and the clinical course.

RESULTS

The incidence of positive Q-wave criteria was 8.1%. Combined biochemical (CK-MB > or = 70 microg/l) and Q-wave criteria were found in 1.0%. Patients with new Q-waves did not have CK-MB or troponin-T levels significantly different from those without Q-waves. More than 25% of the Q-waves were associated with plasma troponin-T below the reference level (< 0.2 microg/l) on the fourth postoperative day. Q-wave criteria alone did not influence the postoperative course. In contrast, biochemical markers correlated with clinical outcome.

CONCLUSIONS

The majority of Q-waves appearing after coronary surgery were not associated with major myocardial tissue damage, and according to troponin-T one-fourth of the Q-waves were not associated with myocardial necrosis. Furthermore, the appearance of Q-waves had little influence on short term clinical outcome. Therefore, the use of Q-wave criteria as the gold standard for diagnosis of PMI may have to be questioned.

Myocardial injury after electrical therapy for cardiac arrhythmias assessed by troponin-T release

Episodes of ventricular fibrillation with subsequent intracardiac, and to a lesser extent, external defibrillation give rise to a statistically significant increase in S-troponin T, S-CK-MB(mass) and S-myoglobin indicative of a minor myocardial injury or dysfunction. In contrast, no such signs were observed after external direct-current conversion of atrial fibrillation using high energies, or after pace-terminated ventricular tachycardia.

Myocardial cooling and right ventricular function in patients with right coronary artery disease: antegrade vs. retrograde cardioplegia

BACKGROUND

Protection of the right ventricular (RV) myocardium during ischaemia in cardiac surgery is difficult, especially in patients with severe right coronary artery (RCA) disease. Retrograde coronary sinus cardioplegia is thought to distribute uniformly, but doubts still remain as to its adequacy in RV preservation. This study evaluated distribution of antegrade vs. exclusively retrograde coronary sinus cold blood cardioplegia by assessing myocardial cooling and compared the effects on RV function.

METHODS

Fifty-eight patients scheduled for elective coronary artery surgery-29 patients with significant RCA disease and another 29 with no significant RCA stenosis (controls)-were randomised to receive either antegrade or retrograde cold blood cardioplegia through either aortic root or conventional self-inflating coronary sinus catheter (RCA-ante, RCA-retro, C-ante and C-retro groups). RV function was assessed by fast-response thermodilution. Myocardial temperatures were measured in the anterior and posterior wall of the right and left ventricle.

RESULTS

Cooling of the posterior wall of the RV was effective only in the control patients given antegrade cardioplegia (14.7 degrees C), whereas in the other groups the lowest myocardial temperatures there remained above 20 degrees C (P < 0.001). In patients with obstructed RCA both antegrade and retrograde cold cardioplegia led to uneven cooling of the myocardium. After cardiopulmonary bypass the RV ejection fraction (RVEF), RV stroke work index (RVSWI) and cardiac index (CI) were significantly reduced in the RCA-retro group, and RVSWI and CI in the C-retro group, too. Regression analysis showed an inverse relationship between the temperatures of the posterior walls of the ventricles and changes in the RVEF and CI.

CONCLUSIONS

Retrograde and antegrade cardioplegia alone were not effective in reducing the temperature of the posterior wall of the RV in the patients with obstructed RCA, in whom with retrograde cardioplegia RV haemodynamics were impaired for 1 hour following bypass. Neither retrograde nor antegrade cardioplegia alone can be relied on to protect the posterior wall of the RV in the patients with obstructed RCA.

Immediate postoperative care of cardiac surgical patients

Anesthetic care of the cardiac surgery patient is a continuum, beginning with the preoperative visit and ending when the patient is ambulatory and breathing well on the postoperative floor. Anesthesiologists are well-suited to provide postoperative care because the respiratory and cardiovascular management techniques are an extension of OR management. Attention to details is as important in the ICU as in the OR and offers the opportunity to forestall or reduce morbidity.

Comparison of perioperative myocardial protection with nifedipine versus nifedipine and metoprolol in patients undergoing elective coronary artery bypass grafting

A randomized study was performed on 70 patients undergoing elective coronary bypass grafting to examine whether the combined infusion of the calcium channel blocker nifedipine (10 micrograms/kg per hour) and the beta 1-blocker metopropol (12 micrograms/kg per hour, n = 34) reduces the prevalence of perioperative myocardial ischemia and arrhythmias. The control group received nifedipine alone (n = 36). In both groups the infusion was started from the onset of extracorporal circulation and maintained over a period of 24 hours. Repeated 12-lead electrocardiographic and 3-channel Holter monitor recordings for 48 hours were used to define perioperative myocardial ischemia (transient ischemic event, myocardial infarction) and arrhythmias (sinus tachycardia, supraventricular tachycardia, atrial flutter/fibrillation, ventricular tachycardia). Hemodynamic parameters were repeatedly assessed for 24 hours and serum enzyme levels (creatine kinase, MB isoenzyme of creatine kinase) for up to 36 hours after the operation. The two groups did not differ significantly with respect to preoperative anamnestic and surgical data. No signs of perioperative myocardial infarction were detected in either group. However, a significantly lower incidence of transient ischemic episodes was observed in the nifedipine-metoprolol group than in the nifedipine group (3% vs 11%; p < 0.05). In addition, there was a tendency toward lower creatine kinase MB levels and peak values of creatine kinase and creatine kinase MB in the nifedipine-metoprolol group. With regard to perioperative arrhythmias, there was a significantly lower incidence of sinus tachycardia and atrial flutter/fibrillation in the nifedipine-metoprolol group (9% and 6%) than in the nifedipine group (33% and 27%, p < 0.05). In addition, postoperative heart rate was lower in the nifedipine-metoprolol group starting from the sixth hour after release of the aortic crossclamp (p < 0.05 and p < 0.01, respectively). No other hemodynamic parameters showed significant differences between the two groups and all returned to preoperative levels within 24 hours. In conclusion, perioperative application of nifedipine and metoprolol in patients undergoing elective coronary bypass grafting reduces the prevalence of perioperative myocardial ischemia and arrhythmias without significant negative inotropic effects. The combined infusion of the two drugs appears superior to nifedipine alone in preventing perioperative myocardial ischemia and reducing reperfusion-induced arrhythmias.

Acadesine: a new drug that may improve myocardial protection in coronary artery bypass grafting. Results of the first international multicenter study. Multinational Acadesine Study Group

The effect of acadesine, an adenosine-regulating agent, on the incidence of myocardial infarction, all adverse cardiovascular outcomes (myocardial infarction, cardiac death, left ventricular dysfunction, life-threatening arrhythmia, or cerebrovascular accident) and mortality was assessed in 821 patients undergoing coronary artery bypass grafting. Patients were prospectively stratified to a high-risk group (age > 70 years, unstable angina, previous coronary bypass, unsuccessful angioplasty, or ejection fraction < 30%) or a non-high-risk group. They were randomized in a double-blind manner to placebo (n = 418) or acadesine (n = 403) by intravenous infusion over 7 hours (0.1 mg/kg per minute) and in the cardioplegic solution (placebo or acadesine; 5 micrograms/ml). Acadesine did not significantly affect the incidence of myocardial infarction in the overall study population, but it significantly reduced the incidence of Q-wave myocardial infarction in high-risk patients (placebo, 19.7%; acadesine, 10.0%; p = 0.032). The incidences of all adverse cardiovascular outcomes (placebo, 19.4%; acadesine, 18.4%) and overall mortality (placebo, 3.4%; acadesine, 2.7%) were similar between the two treatment groups. However, acadesine reduced the incidence of cardiac related events that contributed to deaths occurring during the first 3 postoperative days so that the incidence of death in this period was lower (placebo, 1.9%; acadesine, 0.2%; p = 0.038). No adverse events were related to acadesine treatment. Although overall there were no statistically significant between-group differences for the primary study end points, a secondary analysis in a prospectively defined high-risk subgroup suggests that acadesine may be beneficial in some patients.

Biochemical markers of myocardial damage

OBJECTIVE

To assess various biochemical markers of myocardial damage.

METHODS AND RESULTS

Before routinely using any test as a biochemical marker of myocardial damage, the published evidence for its diagnostic utility must be critically assessed. Such assessment includes receiver operator curve (ROC) curve analyses, confidence interval estimates of claimed sensitivity and specificity values, and the effects of testing in serial and parallel modes. It is also necessary to establish the test's rule-in (high specificity) and rule-out (high sensitivity) decision thresholds that may vary with time after the onset of symptoms. The spectrum of ischemic heart disease includes acute (sudden death, non-Q- and Q-wave infarctions) and chronic (stable, unstable, and variant angina) conditions. Biochemical markers of myocardial damage are of most value in the diagnosis of acute ischemic heart disease, although increasingly some of these markers are being found to possess a prognostic value in chronic ischemic heart disease. The markers of enzymatic activity include aspartate aminotransferase, creatine kinase (together with isoenzymes and isoforms), and lactate dehydrogenase and isoenzymes. Creatine kinase isoenzyme-2 may also be measured immunologically, and this type of assay is in increasing use both because of its speed and because its blood levels rise earlier than the corresponding activities. The commercially available nonenzymatic markers are myoglobin and troponin T; troponin I is expected to become available in late 1995. While myoglobin is a nonspecific indicator of myocardial damage, its diagnostic value is due to its early appearance in blood. Troponin T is more cardiac specific, but the published data appears to suggest that the cardiac specificity of troponin I is superior. Troponin levels become abnormal at about the same time after the onset of symptoms as mass assays of creatine kinase isoenzyme-2; therefore, they are not useful as early markers of myocardial damage.

CONCLUSION

The availability of these nonenzymatic markers of myocardial damage must force a reassessment of the continued use of the enzymatic markers. Are they necessary, and if so, which ones should be retained?

Serum cardio-specific troponin T after open heart surgery in patients with and without perioperative myocardial infarction

One hundred and sixteen consecutive patients undergoing open heart surgery were studied to evaluate the diagnostic use of cardiac specific troponin T in serum (S-TnT) measured preoperatively, at day 1 and day 4 postoperatively. The results were related to perioperative myocardial infarction (POMI), diagnostically based on ECG-changes, as well as to other perioperative variables. Cardiac surgery resulted in increased levels of S-TnT day 1 in all patients, and the level of this increase was dependent on the type of surgical procedure performed and the duration of cardiac perioperative ischaemia. Similar results were observed for serum creatine kinase isoenzyme (mass determination) (S-CKMB), but differences were generally less well correlated with other perioperative variables. At day 1, patients with POMI had higher levels of S-TnT as well as S-CKMB when compared to patients without POMI. At day 4, most patients still had elevated levels of S-TnT, but the difference in S-TnT levels between patients with POMI and patients without POMI was more pronounced. In contrast, the levels of S-CKMB were essentially normalized in both groups. Measurements of S-TnT at day 4 appears to be of significant value in diagnosing POMI. However, most of the patients without POMI had increased levels of S-TnT at day 4, suggesting that some irreversible operatively induced myocardial damage had occurred. Thus, even at a late postoperative stage the perioperative duration of ischaemia and type and extent of the surgical procedure should be taken into consideration.

Reperfusion ventricular fibrillation and electric countershocks during coronary artery bypass operations--association with postoperative CK-MB release

Reperfusion ventricular fibrillation during coronary artery bypass surgery is common and electric shocks are often needed to terminate it. Both the fibrillation and the reversing electric shocks are potentially detrimental to the myocardium. In 61 aortocoronary bypass patients with uncomplicated clinical course (no difficulties in weaning from bypass, no ECG changes and no inotropic medication), serial creatine kinase-MB values were recorded. Evaluated explanatory variables were patient age, ejection fraction, aortic occlusion time, perfusion time, number of peripheral anastomoses and of anastomoses to marginal branches, myocardial fibrillation time before aortic cross-clamping, after cross-clamping prior to cardiac arrest and after declamping, and number of defibrillations. The results indicated that reperfusion fibrillation times up to 10 minutes are not harmful, provided that left ventricular decompression is carried out. Too early and thus numerous defibrillations raise creatine kinase-MB levels and probably also damage the myocardium, and therefore should be avoided.

Myocardial release of troponin T after coronary bypass surgery

The temporal changes in cardiac S-troponin T, S-creatine kinase-MB(S-CK-MB)mass and S-myoglobin were studied for 5 days after coronary bypass grafting in 70 patients. Perioperative infarction occurred in ten patients (2 Q wave, 8 non-Q wave). All three markers showed significant increase even in patients without signs of perioperative infarction. Within 8-12 hours their levels rose significantly (p < 0.001) more in the infarction than in the non-infarction cases. Troponin T and CK-MBmass both showed early (< 8-12 h) peaks in patients with perioperative infarction. CK-MBmass returned to near normal levels within 48-72 hours, whereas troponin T remained markedly increased throughout the observation. Myoglobin concentrations varied widely among the infarction cases. In the non-infarction group, troponin T and CK-MBmass (but not myoglobin) were related to the aortic cross-clamp time. Troponin T (but not CK-MBmass) remained elevated throughout the study period in patients with longer cross-clamp times. These findings may indicate continuous release from damaged myocardium in cases of perioperative infarction. Troponin T and CK-MBmass can serve as markers of perioperative infarction and troponin T may also be useful as a marker in studies on myocardial protection.

Risk analysis of operative intervention for failed coronary angioplasty

To assess the outcome of emergency coronary artery bypass grafting (CABG) after failed percutaneous transluminal coronary angioplasty (PTCA), 91 patients undergoing emergency CABG after failed PTCA over a 30-month period ending July 31, 1991, were studied. For reference, a cohort of patients (91) concurrently undergoing elective CABG equally matched for age, sex, number of grafts, ventricular function, and reoperative status was compared. Specific outcomes including death, hospital length of stay, use of blood products, and development of myocardial infarction were analyzed. More than half the patients undergoing emergency CABG for failed PTCA required three or more grafts. Operative mortality was 12.1% (11/99) for emergency CABG compared with 1% (1/91) for elective case-matched CABG patients (p = 0.007). Emergency CABG patients required frequent use of postoperative inotropes (p = 0.02) and intraaortic balloon counterpulsation (p = 0.001). Length of hospital stay (p = 0.005), administration of blood products (p = 0.009), postoperative myocardial infarction (p = 0.0005), and ventricular arrhythmias (p = 0.0004) were increased after emergency compared with elective CABG. The presence of multivessel disease or use of a reperfusion catheter had no influence on clinical outcome. Despite accumulated experience and improved operative management, patients requiring emergency CABG for failed PTCA remain at increased risk for postoperative complications and death.

Initial experience with low-potassium cold blood cardioplegia: a clinical comparative study

This study presents the results of bypass grafting in 96 patients operated on for triple-vessel coronary artery disease between May 1988 and September 1990. In the first 54 patients a cold crystalloid solution was employed, and in the 42 more recent patients cold blood low-potassium cardioplegia was employed. There were no differences in postoperative cardiac index or left ventricular stroke work index. Yet, in patients with impaired prebypass left ventricular stroke work index, postbypass left ventricular performance correlated negatively with duration of aortic cross-clamping in the cold crystalloid group (r = -0.441, p = 0.045). In contrast, no correlation was found in the cold blood low-potassium group (r = 0.125, p = 0.587). The incidence of myocardial infarction, need for inotropic support, and need for intraaortic balloon counterpulsation were similar among the groups. Release of the myocardial isoenzyme creatine kinase-MB from 12 to 30 hours after operation was significantly less in the low-potassium blood cardioplegia group. The use of low-potassium blood cardioplegia resulted in a marked reduction in the operative administration of fluids (1,527 +/- 87 versus 3,511 +/- 148 mL; p less than 0.001). In conclusion, low-potassium cold blood cardioplegia is a simple and effective method of myocardial protection. The fact that left ventricular stroke work index recovery was not dependent on the duration of aortic occlusion and that release of the MB isoenzyme of creatine kinase was reduced in the low-potassium blood cardioplegia group implies better myocardial protection.

Nifedipine reduces the incidence of myocardial infarction and transient ischemia in patients undergoing coronary bypass grafting

A randomized study was performed on 104 patients undergoing elective coronary artery bypass grafting to examine whether the infusion of nifedipine (n = 53) reduces the incidence of perioperative myocardial ischemia and necrosis in the early postoperative period. Continuous hemodynamic and three-channel Holter monitoring was performed for 24 hours and serial assessment of serum enzymes and 12-lead electrocardiography were performed for 36 hours postoperatively. Nifedipine (minimum dose, 10 micrograms/kg/hr for 24 hours) was applied from the onset of extracorporal circulation. The control group (n = 51) received nitroglycerin (minimum dose, 1 micrograms/kg/min for 24 hours). Using the combined analyses of electrocardiography and Holter recordings, myocardial ischemia was defined as being either a transient ischemic event (TIE), transient coronary spasm (TCS), or myocardial infarction (MI). The two groups did not differ with respect to preoperative New York Heart Association classification, age, history of myocardial infarction, extracorporal circulation and aortic cross-clamp time, number of distal anastomoses, or systemic and pulmonary hemodynamics. The incidence of perioperative myocardial ischemia was substantially lower in the nifedipine than in the nitroglycerin group [TIE: three of 53 patients (6%) versus nine of 50 patients (18%), p less than 0.001; MI: two of 53 patients (4%) versus six of 50 patients (12%), p less than 0.001; and TCS: none of 53 patients (0%) versus two of 50 patients (4%), p = NS].(ABSTRACT TRUNCATED AT 250 WORDS)