Evidence Of Perioperative Myocardial Infarction Research Articles

Polymorphisms in glutathione S-transferase are risk factors for perioperative acute myocardial infarction after cardiac surgery: a preliminary study

In the present study we explored glutathione S-transferase (GST) polymorphisms in selected patients who experienced accelerated myocardial injury following open heart surgery and compared these to a control group of patients without postoperative complications. 758 Patients were enrolled from which 132 patients were selected to genotype analysis according to exclusion criteria. Patients were divided into the following groups: Group I: control patients (n=78) without and Group II.: study patients (n=54) with evidence of perioperative myocardial infarction. Genotyping for GSTP1 A (Ile105Ile/Ala113Ala), B (Ile105Val/Ala113Ala) and C (Ile105Val/Ala113Val) alleles was performed by using real-time-PCR. The heterozygous AC allele was nearly three times elevated (18.5 vs. 7.7%) in the patients who suffered postoperative myocardial infarction compared to controls. Contrary, we found allele frequency of 14.1% for homozygous BB allele in the control group whereas no such allele combination was present in the study group. These preliminary results may suggest the protective role for the B and C alleles during myocardial oxidative stress whereas the A allele may represent predisposing risk for cellular injury in patients undergoing cardiac surgery.

Echocardiographic Identification of Iatrogenic Injury of the Circumflex Artery During Minimally Invasive Mitral Valve Repair

Injury to the circumflex artery after mitral valve (MV) repair or replacement is a recognized complication of this procedure. We designed an echocardiographic method to visualize the course and flow of the circumflex artery, to detect iatrogenic injury to this structure intraoperatively, as well as to predict the coronary dominance pattern in MV surgery patients. After Ethics Committee approval, a prospective study was undertaken in 110 patients undergoing minimal invasive MV repair. Intraoperative transesophageal echocardiography was used to visualize the circumflex artery using a combination of B-mode imaging and color Doppler with different Nyquist limits. The course of the circumflex artery and the coronary sinus and their corresponding diameters were documented at the proximal and distal ends of both vessels. Preoperative angiographic data were used to determine the coronary dominance type. The course of the circumflex artery could be detected proximally in 109 patients (99%), to the point of intersection with the coronary sinus in 99 patients (90%), and distal to this intersection in 95 patients (86%) using our technique. Three patients had evidence of iatrogenic aliasing (circumflex stenosis) or "no flow" (circumflex occlusion) on transesophageal echocardiography examination after repair and therefore underwent surgical or percutaneous correction. All 3 of these patients had an uncomplicated postoperative course thereafter with no evidence of perioperative myocardial infarction. All remaining patients with normal circumflex examinations after repair did not show any clinical evidence of myocardial infarction or unstable hemodynamics postoperatively. The 95% confidence interval for the diameter of the proximal circumflex artery was 4.5 mm to 5.6 mm for the left dominant type patients and 3.8 mm to 4.2 mm for the right dominant and balanced type patients (p = 0.01). The early recognition of iatrogenic injury of the circumflex artery is feasible with intraoperative transesophageal echocardiography examination, and may lead to treatment before extensive myocardial infarction occurs. We suggest that visualization of the circumflex artery with our technique should be performed more frequently in patients undergoing MV surgery.

Comparison of sevoflurane and isoflurane in OPCAB surgery

Maintenance of anaesthesia with volatile anaesthetic agents affects the perioperative course of patients undergoing off-pump coronary artery bypass (OPCAB) surgery. This facilitates adequate depth of anaesthesia, reduction in need of analgesic dosage, early extubation and transfer from Intensive Care Unit. We compared two volatile anaesthetic agents sevoflurane and isoflurane in terms of haemodynamic effects, amount of analgesic needed during surgery, quantity of agent needed for maintenance of anaesthesia and postoperative recovery in 40 patients undergoing OPCAB surgery. Anaesthesia was induced with fentanyl, midazolam and thiopentone, and vecuronium was used for muscle relaxation. An Octopus stabiliser was used and coronary anastomosis was performed using internal mammary artery and saphenous vein grafts. Routine monitoring was performed. The depth of anaesthesia was monitored using Bispectral index monitor. The inspired/expired concentration of anaesthetic agents to maintain the desired BIS and the amount of volatile anaesthetic agent needed was also noted. The amount of analgesic used intraoperatively was noted in both the groups. The 'time of awakening' defined as eye opening on verbal commands, and time of extubation were noted. There were no differences in haemodynamic parameters, depth of anaesthesia, and quantity of agent needed, but patients in isoflurane group required more intraoperative analgesics than sevoflurane group. Time of awakening (48+/-13 vs 114 +/- 21 mins; P < 0.001) and subsequent extubation (124 +/- 25 vs 177 +/- 36 mins, P<0.001) was earlier in sevoflurane group than isoflurane group. There was no evidence of perioperative myocardial infarction in both the groups. We conclude that sevoflurane and isoflurane can both be safely used in OPCAB surgery, but the awakening and extubation times are significantly less with sevoflurane.

Is new ST-segment elevation after coronary artery bypass of clinical importance in the absence of perioperative myocardial infarction?

Objective To determine the frequency and significance of new ST-segment elevation during the early postoperative period after coronary artery bypass grafting (CABG) in patients without enzymatic or electrocardiogram evidence of perioperative myocardial infarction (MI). Methods Pre- and early postoperative electrocardiograms were reviewed in 506 patients undergoing CABG in whom MI was excluded by the absence of new Q waves or left bundle branch block and a peak postoperative troponin I less than 10 ng/mL. Results New ST-segment elevation of 0.1 mV or greater was observed in 64 patients (12.6%). Patients with and without ST-segment elevation did not differ with regard to age, prior coronary artery bypass, number of grafts, use of the internal mammary artery, incidence of postoperative atrial fibrillation, length of stay in the intensive care unit, duration of hospitalization, or 30-day mortality. Conclusions ST-segment elevation not due to perioperative MI is common after CABG but is not associated with increased postoperative morbidity or mortality.

Warm and tepid cardioplegia: Do they provide equal myocardial protection?

Background Cardiac troponin I (CTnI) has been shown to be a marker of myocardial injury. The aim of this prospective, randomized study was to compare intermittent antegrade warm cardioplegia with tepid blood cardioplegia in patients undergoing first elective coronary artery bypass graft, using CTnI release as the criterion for evaluating the adequacy of myocardial protection. Methods Seventy patients were randomly assigned to one of two cardioplegia groups. CTnI concentrations were measured in serial venous blood samples drawn immediately before cardiopulmonary bypass and after aortic unclamping at 6, 9, 12, and 24 hours. Analysis of covariance with repeated measures was performed to test the effect of the type of cardioplegia and time on CTnI concentration. Results The total amount of CTnI released (8.23 ± 20.5 μg in the warm group and 3.19 ± 2.4 μg in the tepid group) was not statistically different ( p = 0.23). The CTnI concentration did not differ for any sample in either of the two groups when adjusted on ejection fraction and the number of preoperative myocardial infarctions ( p = 0.06). No patient in the tepid group versus 4 patients in the warm group showed CTnI evidence of perioperative myocardial infarction ( p = 0.12). Conclusions Our study showed no preference for warm or tepid cardioplegia in terms of myocardial protection, either for clinical or biological data.

Cardiac enzyme elevations after cardiac surgery: The cardiologist's perspective

The clinical significance of myocardial infarction (MI) in patients after major cardiac surgery including valvular replacement and coronary artery bypass grafting (CABG) has been investigated for a number of years. Early reports from some investigators documented that perioperative MI, defined primarily by electrocardiographic criteria, was associated with a worsened longterm prognosis. Other investigators found no correlation of MI with outcomes.1 However, in-hospital postoperative complications were typically more common in patients with evidence of perioperative MI. In studies that have not documented a worsened long-term outcome, mortality was not increased and left ventricular performance was not impaired.2-4 Studies that reported worsened clinical outcomes found increases in both in-hospital and long-term mortality.5-7 Fewer patients with perioperative Q-wave MI had 5-year eventfree survival compared with patients without perioperative events (76% vs 90%).5 Postoperative MI, age, left ventricular function, and the number of comorbidities have been shown to be potent independent predictors of long-term survival.8 In contrast, a substudy analysis from the Coronary Artery Surgery Study (CASS) trial showed that in-hospital mortality was higher in patients with new Q-waves compared with those patients without (10% vs 1%) but 3-year mortality was similar (5%).6 Recently, a number of investigators have evaluated biomarkers of myocardial injury in patients undergoing cardiac surgery.9-14 These studies have included measures of creatine kinase (CK), CK-MB, troponin I, or troponin T. Almost all patients have at least a minor elevation in serum levels of biomarkers as a result of surgical trauma. Marked elevations have been reported in 20% to 40% of patients. In most studies postoperative complications were more common in patients with significant biomarker elevations, but no long-term clinical outcome data have been reported.

Elective stenting of "unprotected" left main coronary stenosis in patients without contraindication to bypass surgery

Coronary surgery is at this point of time the standard therapy of unprotected left main coronary artery stenosis. Coronary angioplasty (PTCA) is performed only in bail out situations. The number of publications of successful percutaneous intervention in unprotected left main coronary stenosis is increasing because of increasing use of stents and ticlopidine to avoid stent-thrombosis. From 9/96 to 7/98, 13 patients with unprotected left main coronary stenosis were treated with stents. All of them were accepted by the heart surgeon for bypass surgery but were not considered to be optimal candidates due to advanced age of more than 80 years (n = 5), significant co-morbidity (n = 2) or diffuse diseased peripheral coronary segments (n = 6). Mean age of patients was 74 +/- 10 years, 9 were male, and all patients presented with angina III-IV (CCS). Mean ejection fraction was 55 +/- 15%. Localization of stenoses were classified as ostial (n = 5), middle (n = 3), and bifurcational (n = 6). One patient had stenoses both in the ostium and in the bifurcation. In all cases a PTCA of the culprit stenosis was performed prior to stent implantation. The mean diameter of the stents used was 3.3 +/- 0.3 mm and the mean length was 11 +/- 4 mm. In 6 patients a PTCA of either left anterior descendens (LAD) or right coronary artery was performed in the same session. In 4 of these patients it was followed by a stent implantation. All procedures were performed with surgical stand-by, an intraaortal balloon pump was available, but was not uses prophylactically. Stent implantation could be performed successfully in 12 out of the 13 patients (success rate 92%). In bifurcational stenoses stents were positioned with the proximal end in the left main and the distal end in the LAD. Significant injury or occlusion of the circumflex artery was not observed. In one patient with bifurcational stenosis with severe calcification it was not possible to cross the lesion with an accurate sized balloon. Trying to cross with a smaller balloon (2.5 mm) resulted in dissection of the left main coronary artery which could not be reopened again by catheter technique. This patient was transferred to the operating room under conditions of cardiopulmonary resuscitation and a bypass surgery was performed. He was dismissed from the hospital with no evidence of perioperative myocardial infarction. The mean time for follow-up was 12 +/- 7 months, all patients are still alive. In 6 patients an angiography was performed during follow-up because of suspicion of recurrent ischemia. Two patients out of these 6 had restenoses in the left main coronary artery which were re-dilated (17%). Another 2 patients had stenoses in other coronary segments and were also dilated. Thus, stenting of left main coronary artery stenoses is feasible, however, with acceptable risks and could be considered in selected patients as an alternative to coronary artery surgery.

Release of cardiac troponin I in antegrade crystalloid versus cold blood cardioplegia

Objective: The purpose of this study was to assess the efficacy of myocardial protection, comparing antegrade crystalloid cardioplegia with cold blood cardioplegia, in patients with preserved left ventricular function who were undergoing elective first coronary artery bypass grafting. Release of cardiac troponin I was used as a marker for the effectiveness of myocardial protection. Methods: A consecutive series of 62 patients were randomly assigned to receive crystalloid or blood cardioplegia. Cardiac troponin I concentrations were determined in venous blood samples before the operation, immediately after unclamping, at 6, 9, 12, and 24 hours, and daily thereafter for 5 days. Results: Rising levels of troponin I were found in all patients. The time course and peak release were similar in the crystalloid cardioplegia and the blood cardioplegia groups. No patients in either group had electrocardiographic evidence of perioperative myocardial infarction. Cardiac troponin I was able to detect small areas of myocardial damage, not revealed by electrocardiography or creatine kinase MB release. Aprotinin administration was associated with lower cardiac troponin I release in both groups. Cardiac troponin I was lower in patients whose conditions did not require electrical defibrillation after aortic unclamping, irrespective of cardioplegia type. The presence of a main stem lesion was associated with higher cardiac troponin I release only in the crystalloid cardioplegia group. Conclusions: Antegrade cold blood cardioplegia is equally effective as antegrade crystalloid cardioplegia in a randomized group of patients with preserved left ventricular function who were undergoing elective first coronary artery bypass grafting. Aprotinin administration resulted in lower cardiac troponin I release, whereas electrical defibrillation was related to a higher release irrespective of cardioplegia type. The presence of a main stem lesion resulted in higher cardiac troponin I release in the crystalloid cardioplegia group. (J Thorac Cardiovasc Surg 1999; 118:452-9)

Expanding indications for pediatric coronary artery bypass

Pediatric coronary artery bypass has been done mostly for ischemic complications of Kawasaki disease. We reviewed our clinical experience between 1987 and 1994 with internal thoracic artery–coronary artery bypass in one infant and five children for varying indications. Indications for coronary bypass included Kawasaki disease (2), congenital left main coronary ostial stenosis, iatrogenic coronary cameral fistula, anomalous origin of the left coronary artery from the pulmonary artery, and single coronary artery traversing between the great arteries in a patient after cardiac transplantation. An additional cohort of 34 control patients of various ages and weights (1 day to 16.1 years, 2.6 kg to 62 kg) had angiographic measurements of the right coronary, left coronary, and left internal thoracic arteries with respect to the feasibility of performing coronary artery bypass. All six patients survived internal thoracic artery–left anterior descending coronary artery bypass without evidence of perioperative myocardial infarction. Postoperative angiographic studies in five and color Doppler echocardiography in one showed graft patency. Retrospective angiographic measurements in the 34 control patients showed that internal thoracic and coronary arteries are proportionately quite large in neonates and infants compared with those in older children and adolescents. Internal thoracic artery–coronary artery bypass should be considered for the expanding indications presented herein and when emergency intraoperative life–threatening situations present themselves. Long–term patency and reoperation rates have yet to be determined. (J T HORAC C ARDIOVASC S URG 1996;111:181-9)

Aortic root cardioplegia: An adequate method for myocardial protection in complete occlusion of the left main coronary artery

Three cases of coronary artery bypass grafting for complete occlusion of the left main coronary artery are described. Delivery of cardioplegia through the aortic root was used in all 3 cases with no evidence of perioperative myocardial infarction. Despite its theoretical disadvantages, aortic root cardioplegic delivery is an adequate technique of myocardial preservation in the presence of sufficient collateral vessels.

Beyond cold cardioplegia

One hundred fifteen consecutive patients were operated on for myocardial revascularization or valvular disease or both with continuous antegrade and retrograde aerobic warm (37 °C) blood cardioplegia. Mean cross-clamp time was 56.3 ± 21 minutes (± standard deviation). Mean reperfusion time was 18.4 ± 11.8 minutes (range, 5 to 81 minutes). Five patients (4.3%) died, and 15 (13%) needed inotropic support. Two (1.7%) required intraaortic balloon support. Two patients (1.7%) had evidence of perioperative myocardial infarction, and 98 (85%) returned spontaneously to normal sinus rhythm. Sixteen patients had a cross-clamp time greater than 80 minutes. All 16 of them had an uneventful postoperative course except for 1 patient who required inotropic drugs. This method of myocardial protection is now used for all open heart procedures in our institution.

Retrograde continuous warm blood cardioplegia: A new concept in myocardial protection

This report presents the results in our first clinical series of patients receiving continuous warm blood cardioplegia through the coronary sinus. Warm oxygenated blood cardioplegia has certain theoretical advantages, such as continuously supplying oxygen and substrates to the arrested heart while avoiding the side effects of hypothermia. Retrograde infusion of cardioplegia also offers certain advantages (eg, in valve operations and in patients with severe coronary artery disease) that are complementary to warm blood cardioplegia. Retrograde warm blood cardioplegia was used in 113 consecutive patients (85 men and 28 women with a mean age of 61 years) undergoing various procedures. Three percent of the patients died, 7% needed transient intraaortic balloon pump support, 6% had evidence of perioperative myocardial infarction, and 96% had spontaneous return of rhythm. There were no coronary sinus injuries. This new technique of retrograde continuous warm blood cardioplegia is a simple, safe, and reliable method of myocardial protection that may change the way we currently protect the heart intraoperatively.

Coronary artery bypass grafting in patients with calcified ascending aorta: Aortic no-touch technique

To perform coronary artery bypass grafting safely for patients with calcified ascending aorta, an “aortic no-touch technique,” which consisted of (1) maximal utilization of In situ arterial grafts, (2) fibrillatory arrest without aortic cross-clamp, (3) left ventricular venting through the right superior pulmonary vein, and (4) femoral artery perfusion, was attempted in 3 patients. All were men, aged 64, 70, and 56 years, respectively, with triple-vessel disease with severe atherosclerotic lesion in the ascending aorta. Bilateral internal mammary arteries and the right gastroepiploic artery were used in all patients. All patients survived without evidence of perioperative myocardial infarction or cerebrovascular accident.

Lactate dehydrogenase isoenzyme-1 in serum for detection of peri-operative myocardial infarction after cardiac surgery.

We prospectively studied changes in serum lactate dehydrogenase isoenzyme-1 (LD-1, EC 1.1.1.27) in 99 consecutive patients after either coronary artery bypass grafting (CABG, n = 61), isolated cardiac-valve replacement (n = 24), or the two procedures combined (n = 14); 86 of these had no clinical evidence of peri-operative myocardial infarction (MI). Blood was sampled immediately after surgery and at 6-h intervals for up to 42 h thereafter. LD-1 was isolated by using the LD M-subunit antiserum. Samples from the non-MI patients were used to establish the reference intervals for LD-1. By 24 h after surgery, mean serum LD-1 values were higher (P less than 0.001) in non-MI patients who underwent isolated valve replacement (222 +/- 74 U/L) or combined CABG and valve replacement (266 +/- 58 U/L) than in 50 non-MI patients who underwent CABG alone (134 +/- 42 U/L). Separate reference intervals were determined for CABG and other patients at each sampling time. By 24 h after operation, LD-1 exceeded these reference intervals in the 10 CABG and two combined-procedure patients in whom other evidence of MI was present. Measurement of LD-1 24 to 42 h after cardiac surgery appears to be a useful test for the diagnosis of perioperative MI.

Changes in serum creatine kinase and lactate dehydrogenase caused by acute perioperative myocardial infarction and by transatrial cardiac surgical procedures

A prospective clinical study was conducted to ascertain if a patient's postoperative elevation in serum creatine kinase MB isoenzyme coupled with determination of the lactate dehydrogenase1/lactate dehydrogenase2 ratio could differentiate whether atrial or ventricular myocardium was the source of these changes. Animal studies have shown that atrial myocardium is as rich a source of creatine kinase MB as is ventricular myocardium. Atrial myocardium has a lactate dehydrogenase1/lactate dehydrogenase2 ratio less than 1.00, whereas in ventricular myocardium the ratio is greater than 1.00. Sixty-four patients were assigned to six groups on the basis of serial electrocardiograms and vectorcardiograms by a cardiologist who was unaware of their clinical courses. The control group (Group 1) consisted of 16 patients admitted to the coronary care unit who had no electrocardiographic changes. Three surgical groups without electrocardiographic or vectorcardiographic evidence of perioperative myocardial infarction were studied: 10 patients undergoing routine coronary artery bypass procedures (Group 2), six adults undergoing repair of secundum atrial septal defect (Group 3), and 13 patients having mitral valve replacement (Group 4). Two groups of surgical patients who had acute perioperative transmural myocardial infarctions confirmed by serial electrocardiograms and vectorcardiograms were studied: 15 patients (Group 5) who had elective coronary artery bypass procedures and four (Group 6) who had mitral valve replacement. This study suggests that serum creatine kinase MB levels in excess of 50 IU/L on the postoperative day 1 and day 2 samples coupled with serum lactate dehydrogenase1/lactate dehydrogenase2 ratios greater than 1.00 on the postoperative day 2 and day 3 samples support the diagnosis of acute myocardial infarction. Patient groups undergoing procedures necessitating atriotomies had average elevations in serum creatine kinase MB and in the lactate dehydrogenase1/lactate dehydrogenase2 ratio, but these were significantly less than those seen when acute perioperative myocardial infarction had occurred.

Coronary Artery Bypass Graft Surgery: Clinical Comparison of Cold Blood Potassium Cardioplegia, Warm Cardioplegic Induction, and Secondary Cardioplegia

An analysis of myocardial protection was performed in 45 low-risk patients undergoing coronary bypass procedures who were divided into three equal groups with similar preoperative ejection fractions and coronary artery obstructions. Group 1 (N = 15) received cold blood cardioplegia, Group 2 received cold blood cardioplegia and secondary cardioplegia, and Group 3 received cold blood cardioplegia plus warm cardioplegic induction. The aortic cross-clamp time and the number of bypass grafts were similar among the groups. The following variables were measured serially: electrocardiographic changes, serum myocardial-specific isoenzyme of creatine kinase, cardiac output, left ventricular filling pressure, ejection fraction, and left ventricular wall motion. The three methods evaluated were all effective in protecting the myocardium during global myocardial ischemia. Patients who received secondary cardioplegia (Group 2) were more likely to exhibit spontaneous defibrillation (12/15) than those in Group 1 (5/15) or Group 3 (6/15) ( p < 0.05). However, measurements of left ventricular performance and evidence of perioperative myocardial infarction were similar among all three groups. These data suggest that a standard technique of cold potassium cardioplegia alone should be the method of choice in elective, low-risk coronary bypass operations rather than this technique in combination with either of the other two more costly and complex methods evaluated in this study.

The radionuclide evaluation of septal wall motion following coronary bypass surgery.

We investigated the diagnostic accuracy of radionuclide global and regional left ventricular (LV) function after coronary revascularization. A consecutive series of 43 patients was studied. First-pass radionuclide angiograms were performed preoperatively (4 days +/- s.d. 3 days, range 1-18 days) and postoperatively (7 days +/- s.d. 3 days, range 3-19 days). Regional radionuclide LV function was assessed using the two-dimensional display of systole and the three-dimensional ejection fraction image. Electrocardiograms were obtained the day prior to surgery and every 8 h for the first three postoperative days. Creatine kinase (CK) and lactate dehydrogenase (LDH) isoenzymes were obtained the day prior to surgery and every 8 h for the first three postoperative days. In 39 patients who did not develop perioperative myocardial infarction by isoenzyme or ECG criteria, we found that 38 patients showed unchanged or improved global and regional LV function, while one patient without isoenzyme or ECG evidence of perioperative myocardial infarction developed a new septal wall motion abnormality. Thus, the specificity of the radionuclide radioventriculogram for new septal wall motion abnormalities was very high. In four patients who developed isoenzyme and ECG evidence of myocardial infarction, septal wall motion worsened in all four patients while global left ventricular ejection function fell significantly in three patients. Thus, the radionuclide radioventriculogram also had high diagnostic sensitivity. In summary, contrary to past and recent reports, this investigation demonstrated that the radionuclide radioventriculogram can be used to assess global and regional LV function after coronary artery bypass surgery and furthermore, that it reliably indicates the presence of a new postoperative myocardial infarction.

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-py-rophosphate 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-MB Release Following Coronary Artery Bypass Grafting in the Absence of Myocardial Infarction

Elevation of levels of the myocardial-specific isoenzyme of creatine kinase (CK-MB) in the immediate postoperative period in patients undergoing coronary artery bypass grafting is usually associated with myocardial necrosis. However, mean isoenzyme elevations of 18 ± 2 IU/L (standard error of the mean) were recently observed in 6 patients in the absence of electrocardiographic or scintigraphic (technetium 99m stannous pyrophosphate) evidence of perioperative myocardial infarction. To test the hypothesis that surgical trauma of the atrium and aorta during cannulation for cardiopulmonary bypass might contribute to elevated CK-MB levels, biopsy of the right atrial appendage and aorta of 7 patients was done at operation, the tissue samples were assayed for total creatine kinase (CK) activity using the Rosalki technique, and for CK-MB using column chromatography. The results indicate that the human atrium is a rich source of CK, with the proportion of CK-MB similar to that present in the ventricle (20%). In addition, technical considerations inherent in the performance of coronary bypass surgery may result in release of CK-MB, causing elevated serum enzyme levels in the post-coronary artery bypass patient in the absence of myocardial infarction.

Radionuclide Assessment of Left Ventricular Function in Patients Requiring Intraoperative Balloon Pump Assistance

Twenty-three surviving patients who were weaned from cardiopulmonary bypass with intraaortic balloon pump assistance returned for follow-up radionuclide left ventricular (LV) function and thallium 201 perfusion studies at a mean of 23 ± 3 months following operation. It was found that despite profound intraoperative myocardial depression requiring intraaortic balloon assistance, 13 patients had no change (within 10%) in the resting LV ejection fraction compared with the preoperative measurement. Among all 23 patients, there was no difference between mean (± standard error of the mean) preoperative and postoperative resting LV ejection fraction (48 ± 4 vs 46 ± 4%, p = not significant [NS]). Only 11 patients had perioperative myocardial infarction documented by new Q waves in the electrocardiogram, by elevation of creatine kinase–MB fraction, or by defects on thallium 201 imaging not explained by documented myocardial infarction before operation. Overall, postoperative resting LV ejection fraction was not different from the preoperative value in patients with perioperative myocardial infarction (44 ± 7 vs 47 ± 5%, p = NS). Postoperative resting LV ejection fraction rose by ≥ 10% compared with preoperative values in 4 patients (3 with aortic valve replacement), remained within the 10% limit in 9 patients, and fell by ≥ 10% in 10 patients (7 with perioperative myocardial infarction). Only 4 out of 16 patients studied at follow-up with exercise radionuclide studies demonstrated a normal LV response to exercise (≥ 5% increase in LV ejection fraction). Thus, among survivors requiring intraaortic balloon pump assistance for weaning from cardiopulmonary bypass, LV performance at rest is frequently preserved. In addition, 11 of the 23 patients had evidence of perioperative myocardial infarction, indicating a component of reversible intraoperative LV dysfunction.