Perioperative myocardial infarction related to coronary bypass surgery

Acute ischemic syndromes following coronary artery bypass graft surgery

Coronary artery bypass graft (CABG) surgery, performed for the control of angina pectoris, leads to postoperative relief from symptoms in most patients. Amelioration of ischemia and improvement in exercise capacity after CABG are well documented. However, patients currently undergoing CABG are more complex than in the past--they are older and are maintained on medical therapy for longer periods. A large number of these patients have had one or more previous myocardial revascularization procedures. The post-operative period would appear to be a time of vulnerability for coronary events. However, previous investigators have focused on the pre- and intraoperative aspects of peri-CABG ischemia. Outcome data suggest that the postoperative interval is at least equally important as a determinant of short- and long-term morbidity and mortality. We discuss the epidemiology, etiology, pathophysiology, and treatment of ischemic syndromes in the postoperative period after CABG. In addition, we review recent data from a series of 14 patients, observed at our institution, who underwent cardiac catheterization and, in some cases, angioplasty of the culprit vessel in the immediate postoperative period.

Comparison of some criteria for diagnosing a myocardial infarction after aorto-coronary bypass grafting (CABG)

The incidence of myocardial infarction during a 1-year follow-up period after coronary bypass surgery (CABG), i.e. a recent myocardial infarction (RMI), was studied in 86 patients. Different criteria for the diagnosis of a RMI were compared. Clinical observation, including ECG and serum enzyme analysis, diagnosed RMI in 8% of patients. Specific ECG changes indicating RMI (ECGsp) occurred in 12% of cases, and if less specific ECG changes were also taken into account (ECGsp+nonsp) RMI was found in 30% of cases. Asynergy, detected by two-plane ventriculography, indicated RMI in 24% of the patients, and was probably the most valid of the criteria examined. The differences in diagnostic accuracy of the various criteria highlight the importance of defining diagnostic criteria.

Frequency of acute myocardial infarction in valve repairs versus valve replacement for pure mitral regurgitation

Three hundred thirty-five consecutive isolated mitral valve operations for mitral regurgitation in patients with no significant coronary artery disease were reviewed over a 26-month period for the presence of a perioperative acute myocardial infarction (AMI). Of 224 patients undergoing mitral valve repair 12 (5.4%) had electrocardiographic and cardiac enzyme evidence of perioperative AMI develop. Of 111 patients undergoing mitral valve replacement none had perioperative AMI develop as determined by electrocardiographic and enzyme criteria (p = 0.01). All 12 infarctions after valve repair involved the inferior wall by electrocardiographic or echocardiographic criteria. Although no patient had significant clinical difficulty in recovery, 7 of the 12 patients (58%) were left with Q waves upon hospital discharge. The etiology of the AMI is believed to be air emboli introduced at the time of testing valve competence during left ventricular insufflation under pressure. Changes in surgical technique may reduce or eliminate this complication.

Non-Q wave perioperative myocardial infarction: assessment of the incidence and severity of regional dysfunction with quantitative two-dimensional echocardiography

Since the widespread use of hypothermic potassium cardioplegia began, marked reductions in perioperative mortality and the rate of Q wave-associated myocardial infarctions have been noted. No study to date has evaluated whether there has been an equally dramatic improvement in the incidence of postoperative myocardial infarctions unassociated with Q wave development. We used a previously validated quantitative two-dimensional echocardiographic analytic algorithm to determine the incidence and severity of regional wall motion abnormalities (RWMAs) and first-pass radionuclide ventriculography to assess deterioration in global left ventricular function in the four following groups of patients (total n = 65): (1) those with peak postoperative creatine kinase (CK)-MB levels equal to or less than the mean value for patients undergoing coronary artery bypass surgery at our institution (n = 10), (2) those with CK-MB levels between the mean and 1 SD above the mean (n = 10), (3) those with peak CK-MB levels higher than 1 SD above the mean (n = 25), and (4) those with new pathologic Q waves on the postoperative electrocardiogram (n = 20). All patients had electrocardiograms without pathologic Q waves and normal wall motion and ejection fraction by contrast ventriculography before surgery. The incidence of postoperative RWMA by two-dimensional echocardiography for groups 1 through 4 was 0%, 20%, 55%, and 89%, respectively. Percent of abnormal left ventricular segments, wall motion scores, and the deterioration in left ventricular ejection fraction as assessed by radionuclide ventriculography were similar for patients with new RWMAs whether or not new Q waves developed (p = NS for all).(ABSTRACT TRUNCATED AT 250 WORDS)

Synchronized coronary venous retroperfusion: prompt improvement of left ventricular function in experimental myocardial ischemia

The effect of synchronized coronary venous retroperfusion of arterial blood on cardiac function after experimental coronary occlusion was examined by two-dimensional echocardiography. In 18 closed chest anesthetized dogs, the proximal left anterior descending coronary artery was occluded for 6 hours with an intracoronary balloon catheter. Eight of these animals served as untreated controls. Ten were treated with synchronized retroperfusion initiated 30 minutes after occlusion, and treatment was interrupted for 5 minutes at 1 hour after occlusion for study of the rapidity of retroperfusion response. Quantitative echographic analysis yielded global ejection fraction and regional indexes of contraction in a low left ventricular short-axis section, including segmental systolic area change, systolic wall thickening and end-diastolic wall thickness. At 6 hours after occlusion, ejection fraction had decreased from 50.7 +/- 4.9% to 28.1 +/- 7.7% (mean +/- standard deviation) in control dogs, but was significantly (p less than 0.01) less depressed in treated dogs (from 55.9 +/- 5.2 to 41.8 +/- 9.3%). The ischemic zone fractional area change at 30 minutes of occlusion exhibited a marked depression in both groups, after which the dysfunction persisted in the control dogs, but was largely reversed with retroperfusion from 6.0 +/- 6.5 to 35.9 +/- 15.9% at 6 hours of occlusion (p less than 0.01). Brief interruption of retroperfusion 1 hour after occlusion reduced ischemic zone fractional area change from 33.0 +/- 14.9 to 12.2 +/- 9.5% (p less than 0.01). This depression was promptly reversed to 33.6 +/- 12.2% when retroperfusion was resumed. Segmental wall thickening followed a similar trend.(ABSTRACT TRUNCATED AT 250 WORDS)

Relation between QRS changes and left ventricular function after coronary artery bypass grafting

Preoperative and serial postoperative electrocardiograms (ECGs) were reviewed in 104 patients undergoing rest and exercise radionuclide angiocardiography before and 1 to 12 months after coronary artery bypass grafting (CABG). Five patient groups were defined by ECG findings before and after CABG: Group I--normal ECG before and no ECG change after CABG; Group II--prior myocardial infarction by ECG before but no QRS change after CABG; Group III--all patients with a minor QRS change (less than 0.04-second Q wave, loss of R-wave amplitude) after CABG; Group IV--all patients with a major QRS change (greater than or equal to 0.04-second Q wave) after CABG; Group V--all patients without new Q waves or loss of R-wave amplitude but with a major QRS change (conduction disturbance) after CABG. Mean resting ejection fraction changed little after CABG in all groups, although the 0.03 increase in Group I was significant (p less than 0.05). Group IV had the largest decrease in resting ejection fraction after CABG (0.04), but this was not statistically significant. Mean exercise ejection fraction increased significantly (p less than 0.0001) in Groups I, II and III but not in Groups IV and V. QRS changes do not consistently reflect impairment of left ventricular (LV) function after CABG.

Perioperative myocardial infarction: a diagnostic dilemma

Patients undergoing coronary bypass grafting were studied for incidence of perioperative myocardial infarction (MI) using three modalities: serial electrocardiograms (ECG), serial creatine phosphokinase isoenzymes (MB-CPK), and serial technetium 99m-labeled pyrophosphate scans. A definite perioperative MI was diagnosed if the results were positive in two of the three variables studied. The perioperative infarction rate for the entire group was 8%. The operative mortality was 2.9%. Seven of 8 perioperative MIs were diagnosed by the use of scanning alone. The combination of isoenzyme and ECG analysis diagnosed 5 of 8 perioperative MIs. The MB-CPK and ECG studies were associated with a higher incidence of false-positive diagnoses than myocardial scanning. Patients with perioperative MI had a benign clinical course. Justification for performing three routine 99mTc-pyrophosphate scans on all patients undergoing aortocoronary bypass operation is still to be determined.