New Q waves after coronary artery bypass surgery for angina pectoris

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.

Impact of perioperative myocardial infarction on angiographic and clinical outcomes following coronary artery bypass grafting (from PRoject of Ex-vivo Vein graft ENgineering via Transfection [PREVENT] IV)

Myocardial infarction (MI) after coronary artery bypass grafting (CABG) is associated with significant morbidity and mortality. Frequency, management, mechanisms, and angiographic and clinical outcomes associated with perioperative MI remain poorly understood. PREVENT IV was a multicenter, randomized, placebo-controlled trial of edifoligide in 3,014 patients undergoing CABG. Angiographic and 2-year clinical follow-up were complete for 1,920 and 2,956 patients, respectively. Perioperative MI was defined as creatinine kinase-MB increase >or=10 times the upper limit of normal or >or=5 times the upper limit of normal with new 30-ms Q waves within 24 hours of surgery. Baseline characteristics, in-hospital management, and angiographic and clinical outcomes of patients with and without perioperative MI were compared. Perioperative MI occurred in 294 patients (9.8%). Patients with perioperative MI had longer surgery (250 vs 230 minutes; p <0.001), more on-pump surgery (83% vs 78%; p = 0.048), and worse target-artery quality (p <0.001). Patients with perioperative MI more frequently underwent angiography within 30 days of enrollment (1.7% vs 0.6%; p = 0.021). One-year angiographic vein graft failure occurred in 62.4% of patients with and 43.8% of patients without perioperative MI (p <0.001). Two-year composite clinical outcome (death, MI, or revascularization) was worse in patients with perioperative MI before (19.4% vs 15.2%; p = 0.039) and after (hazard ratio 1.33, 95% confidence interval 1.00 to 1.76, p = 0.046) adjusting for differences in significant predictors. In conclusion, perioperative MI was relatively common, was associated with worse outcomes, and mechanisms other than vein graft failure accounted for a substantial proportion of these MIs. Further research is needed into the prevention and treatment of perioperative MI in patients undergoing CABG.

Cardiac troponin T for prediction of short- and long-term morbidity and mortality after elective open heart surgery

BACKGROUND

Increased cardiac troponins in blood are observed after virtually every open heart surgery, indicating perioperative myocardial cell injury. We sought to determine the optimum time point for blood sampling and the respective cutoff value of cardiac troponin T (cTnT) for risk assessment in patients undergoing cardiac surgery.

METHODS

In a series of 204 patients undergoing scheduled open heart surgery, mainly for coronary artery bypass grafting (n = 132) or valve repair (n = 27), cTnT concentrations were measured before and 4 and 8 h after cross-clamping and then daily for 7 days. Individual risk was assessed by use of the Cleveland Clinic Foundation Risk score and intraoperative risk indicators such as duration of cardiopulmonary bypass, cross-clamping, and perioperative release of cardiac markers. Patients were followed for 28 months.

RESULTS

Cardiac mortality, all-cause mortality rates, and rates of nonfatal acute myocardial infarction (AMI) at 28 months were 6.9%, 8.8%, and 6.8%, respectively. cTnT was higher in patients with Q-wave AMI or postoperative heart failure requiring inotropic support, and in nonsurvivors. The ROC curve revealed a cTnT > or = 0.46 microg/L at 48 h as the optimum discriminator for long-term cardiac mortality. Stepwise logistic regression identified higher Cleveland Clinic Risk Score [odds ratio (OR) = 2.6 per point], cross-clamp time >65 min (OR = 6.6), and cTnT (OR = 4.9) as significant and independent predictors of long-term cardiac mortality.

CONCLUSIONS

A single postoperative cTnT measurement can be used to estimate myocardial cell injury that impacts long-term survival after open heart surgery. It adds independently to established risk indicators.

Troponin I, troponin T, or creatine kinase-MB to detect perioperative myocardial damage after coronary artery bypass surgery

STUDY OBJECTIVES

To compare cardiac troponin I (cTnI), cardiac troponin T (cTnT), and creatine kinase MB (CKMB mass) in patients with and without new Q wave on the ECG following coronary artery bypass graft (CABG) surgery.

PATIENTS

After ethic committee's approval and informed consent, 82 patients, mean age 63+/-10 years, scheduled for CABG were included.

INTERVENTIONS

Arterial blood samples were drawn during cardiopulmonary bypass, before, and 6, 12, 24, and 48 h after aortic cross-clamp release. cTnI, cTnT, and CKMB mass were measured. The appearance of new Q wave on the ECG performed preoperatively and 24 h postoperatively was used to assess myocardial lesion independently of biological markers.

RESULTS

There were 69 patients without new Q wave on the ECG (group 1) and 13 with (group 2). In group 1, cTnI reached a peak of 2.1 microg/L (median, interquartile range [IQ]=2.4) at 12 h, cTnT increased progressively with a peak of 0.22 microg/L (IQ=0.2) at 48 h, and CKMB presented an earlier peak of 10 microg/L (IQ=6.2) at 6 h. Starting with the same median value, group 2 patients presented significantly higher peaks: cTnI: 17 microg/L (IQ=16) at 12 h; cTnT: 1.4 microg/L (IQ=2.3) at 12 h; and CKMB mass: 74 microg/L (IQ=61) at 6 h. Receiver operating characteristic (ROC) curves were constructed. The area under the curve was 0.90 for cTnI, 0.84 for CKMB, and 0.81 for cTnT (not significant). The best cutoff values to discriminate between group 1 and group 2 patients were determined with the ROC curves: cTnI=5 microg/L; CKMB mass=20 microg/L; cTnT=0.3 microg/L. Sensitivity, specificity, and positive and negative values for cTnI (5 microg/L) were 91%, 82%, 53%, and 98%, respectively.

CONCLUSIONS

There was little differences among cTnI, cTnT, and CKMB after CABG to diagnose myocardial damage as assessed by new Q wave on the ECG. There was a trend of cTnI to be a better discriminator than cTnT, but it did not reach statistical significance.

Clinical significance of perioperative Q-wave myocardial infarction: the Emory Angioplasty versus Surgery Trial

OBJECTIVE

The primary end point of the Emory Angioplasty versus Surgery Trial was a composite of three events: death, Q-wave infarction, and a new large defect on 3-year postoperative thallium scan. This study examines the clinical significance of Q-wave infarction in the surgical cohort (194 patients) of the Emory trial.

METHODS

Twenty patients (10.3%) with Q-wave infarctions were identified: 13 patients had inferior Q-wave infarctions and seven patients had anterior, lateral, septal, or posterior Q-wave infarctions (termed anterior Q-wave infarctions).

RESULTS

In the inferior Q-wave infarction group, postoperative cardiac catheterization (at 1 year or 3 years) in 11 patients revealed normal ejection fraction (ejection fraction >55%) in 10 (91%), no wall motion abnormalities in 10 (91%), and all grafts patent in 10 (91%). In the anterior Q-wave infarction group, postoperative catheterization in six patients revealed normal ejection fractions in five (83%), no wall motion abnormalities in three (50%), and all grafts patent in three (50%). Average peak postoperative creatine kinase MB levels were as follows: no Q-wave infarction (n = 174) 37 +/- 43 IU/L, inferior Q-wave infarction 40 +/- 27 IU/L, and anterior Q-wave infarction 58 +/- 38 IU/L. Mortality in the 20 patients with Q-wave infarctions was 5% (1/20) at 3 years; in patients without a Q-wave infarction it was 6.3% (11/174) (p = 0.64). Of 17 patients with a Q-wave infarction who underwent postoperative catheterization, 11 (65%) had a normal ejection fraction, normal wall motion, and all grafts patent with an uneventful 3-year postoperative course.

CONCLUSIONS

The core laboratory screening of postoperative electrocardiograms, particularly in the case of inferior Q-wave infarctions, appears to identify a number of patients as having a Q-wave infarction with minimal clinical significance. Q-wave infarction identified in the postoperative period seems to be a weak end point with little prognostic significance and therefore not valuable for future randomized trials.

Pathogenesis and prognostic significance of conduction abnormalities after coronary bypass surgery

Of 200 men who underwent isolated coronary bypass graft surgery, 40 (20%) developed new postoperative, persistent conduction abnormalities. The pathogenesis of conduction abnormalities was examined by relating their presence to that of significant proximal left coronary disease before surgery, and to various intraoperative factors that included indices of myocardial preservation and revascularization. Proximal left coronary disease was observed in 92 (46%) of 200 patients, of whom 27 (29%) developed conduction abnormalities. In contrast, of the 108 patients without proximal left coronary disease, only 13 (12%) developed persistent conduction abnormalities (P < 0.01). Intraoperative factors appeared to have little or no role in the development of such abnormalities. It is concluded that the development of persistent postoperative conduction abnormalities is related more to proximal left coronary disease than to intraoperative factors and that such abnormalities do not progress during long-term follow-up (average 53 months).

Current incidence and determinants of perioperative myocardial infarction in coronary artery surgery

Increasingly, patients undergoing coronary artery bypass grafting (CABG) are elders, have had previous CABG, and have poor left ventricular function. To evaluate determinants of perioperative myocardial infarction (PMI) after isolated CABG, 499 consecutive patients were reviewed. Definite PMI (total peak creatine kinase [CK] > 700 U/L, creatine kinase MB [CK-MB] > 30 ng/ml, and new pathologic electrocardiographic Q waves) occurred in 25 patients (5.0%) and probable PMI (total peak CK > 700 U/L, CK-MB > 30 ng/ml, and a new wall-motion abnormality) occurred in 10 (2.0%) patients. According to multivariate logistic regression analysis, independent risk factors for definite or probable PMI (adds ratios; 95% confidence intervals) were emergency surgery (3.1; 1.1 to 8.4; p = 0.003), aortic cross-clamp time > 100 minutes (4.2; 1.6 to 11.2; p = 0.004), myocardial infarction in the preceding week (2.6; 1.0 to 6.4; p = 0.04), and previous revascularization (2.4; 1.1 to 5.2; p = 0.02). In conclusion, both preoperative and intraoperative factors influence the risk of PMI after CABG. Despite changes in the profile of patients undergoing CABG, the incidence of PMI in this tertiary center is comparable with that found in earlier series, probably because of improvements in surgical techniques and postoperative care.

Coronary pathology predicts conduction disturbances after coronary artery bypass grafting

Conduction disturbances after coronary artery bypass grafting may result from compromised septal blood flow. To examine this hypothesis we reviewed the preoperative coronary angiography of 55 consecutive patients undergoing coronary artery bypass grafting. Thirty-five patients had either no lesion or a discrete lesion in the left anterior descending coronary artery that did not include the septal perforator (type I anatomy). Twenty patients had a lesion of the left anterior descending coronary artery at the origin of the first septal branch, a lesion of the first septal artery, or a pair of lesions in the left anterior descending coronary artery that straddled the origin of the first septal artery; all lesions were proximal to the graft site (type II anatomy). None of the patients with type I anatomy had a major conduction disturbance after coronary artery bypass grafting. Eleven of the patients with type II anatomy had major conduction disturbances after coronary artery bypass grafting; right bundle-branch block in 1, right bundle-branch block and left anterior hemiblock in 2, left bundle-branch block in 5, and complete atrioventricular block that required pacemaker implantation in 3 (p less than 0.001). In the 20 patients with type II anatomy, the appearance of conduction disturbances correlated well with the absence of retrograde flow to the septal branches from the right coronary artery (p less than 0.01). Pathological lesions in the left anterior descending coronary artery that compromise flow in the first perforator and that do not provide an adequate circulation produce localized damage and conduction disturbances after coronary artery bypass grafting. This can be predicted from the preoperative angiographic anatomy.

Perioperative myocardial infarction after coronary artery bypass surgery. Clinical significance and approach to risk stratification

The clinical significance of perioperative myocardial infarction (MI) after coronary artery bypass surgery is not known. Therefore, strategies for the risk stratification of these patients do not exist. This study was undertaken to define the effect of perioperative MI on prognosis after discharge from the hospital and to develop an approach to the risk stratification of these patients. Fifty-nine patients with and 115 patients without perioperative MI were observed for 30 months for the development of cardiac events (death, nonfatal MI, and admission to hospital for unstable angina or congestive heart failure). Patients with perioperative MI were significantly more likely than patients without to have a cardiac event (31% versus 12%, p less than 0.01) and multiple events (19% versus 1%, p less than 0.001). Cox regression analysis identified two independent predictors of cardiac events other than perioperative MI (relative risk, 2.7): inadequate revascularization (relative risk, 3.5) and depressed (less than 40%) postoperative ejection fraction (EF) (relative risk, 2.1). Event-free survival rate of patients with perioperative MI varied markedly depending on the number of other negative prognostic variables present. Patients with perioperative MI who were adequately revascularized and had a postoperative EF greater than 40% had an event-free survival rate similar to patients without a perioperative MI (92% versus 87%, p = NS). Patients with perioperative MI who were inadequately revascularized and had depressed postoperative EF had an event-free survival rate of 13% (p less than 0.001 versus all other subsets). Event-free survival rate was intermediate (68%) in patients with perioperative MI and with only one of the other two variables (p less than 0.001 versus other subsets). In conclusion, perioperative MI adversely affects prognosis. Patients can be stratified into low, high, and intermediate risk subsets based on a simple assessment of the adequacy of revascularization and a determination of residual left ventricular function.

Arrhythmias after coronary bypass surgery

Ninety patients undergoing coronary bypass surgery were studied prospectively by bedside and subsequent ambulatory electrocardiographic monitoring to investigate the incidence, possible causes, and prevention of atrial fibrillation. Patients with good left ventricular function were divided randomly into a control group or groups treated with digoxin or propranolol. In the control group the incidence of atrial fibrillation was 27% and of significant ventricular extrasystoles 3%. Propranolol reduced the incidence of atrial fibrillation (14.8%), whereas digoxin had no effect and increased the incidence of ventricular extrasystoles. Age, sex, severity of symptoms, cardiomegaly, heart failure, previous myocardial infarction, and number of grafts did not affect the result. The operative myocardial ischaemic time was related to the occurrence of atrial fibrillation. There was also a significant relation between atrial fibrillation and bundle branch block. Atrial fibrillation is common after coronary artery grafting; it may be due to diffuse myocardial ischaemia or hypothermic injury. The incidence may be reduced by beta blockade.

Myocardial infarction related to coronary artery bypass graft surgery

Fifty consecutive patients undergoing coronary artery bypass grafting for chronic stable angina were assessed by serial electrocardiography, preoperative and postoperative myocardial scanning with technetium-99m pyrophosphate, gated radionuclide ventriculography, and serial measurement of creatine kinase, aspartate aminotransferase, urea stable lactic dehydrogenase, and creatine kinase isoenzyme (MB) to assess the incidence of perioperative myocardial infarction and identify the most appropriate diagnostic techniques. The correlation between myocardial scanning and the measurement of peak enzyme and isoenzyme activity was excellent in the diagnosis of perioperative infarction, although electrocardiography proved less helpful. There appeared to be no advantage in measuring creatine kinase MB rather than the more routinely measured enzymes. There were two deaths and evidence of myocardial infarction in five other patients, an incidence of 14%. Perioperative infarction was associated with a significant reduction in resting ejection fraction in two cases. In those patients without evidence of perioperative infarction the mean increase in ejection fraction of 7.8% was statistically significant.

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)

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.

Serum myoglobin concentration as an index of myocardial damage after cardiac surgery

We assessed serum myoglobin concentration as an index of myocardial damage after cardiothoracic surgery in a dog model and man. Experimentally, we compared 12 dogs subject to left thoracotomy either with or without coronary artery ligation to cause an infarct. Serial blood sampling for 24 hours after surgery showed that the times taken for the myoglobin peak concentrations to appear distinguished the two groups without overlap. These times were 2.4 +/- 0.4 hours after surgery without ligation compared with 9.8 +/- 0.8 hours in the ligated group (P less than 0.001). Clinically, serial sampling was performed over 48 hours in 20 patients having undergone cardiac surgery involving cardiopulmonary bypass. A further 80 patients were investigated for 12 hours. Myoglobin was compared with the activities of creatine kinase, 2-hydroxybutyrate dehydrogenase and glutamate-oxaloacetate transaminase in relation to electrocardiographic criteria of myocardial damage. A myoglobin peak greater than 800 micrograms/1 appearing later than 6 hours after starting bypass was found in those patients suffering myocardial damage. The appearance times and activities of the enzymes tested were widely scattered and difficult to interpret. We conclude that blood samples taken at approximately 3 and 6 hours after starting bypass should suffice to characterise both peak myoglobin and its time of appearance which together form a sensitive index of myocardial damage. However, this conclusion is limited by the low incidence of myocardial damage (3%) in this group of patients.

The origin of plasma creatine kinase 1, detected in patients during and following open heart surgery

Plasma creatine kinase 1 (CK-1) was detected intra-operatively in 6 out of 6 patients and postoperatively in 15 out of 22 patients, undergoing cardiac surgery. A transient increase in plasma levels of creatine kinase 2 (CK-2) and total creatine kinase (CK-tot.) activity was observed in all patients. The disappearance rates for the 2 isoenzymes in the circulation were CK-1: Kd = 4.7 X 10(-3) min-1, and CK-2: Kd = 0.60 X 10(-1) min-3. Analysis of vessel and heart tissue showed that the saphenous vein contained mainly CK-1; high activities of all three isoenzymes were found in the parts of the heart investigated. Most probably, both CK-1 and CK-2 are liberated from injured cardiac tissue.

Use of survival analysis to determine the clinical significance of new Q waves after coronary bypass surgery

There are few data on the long-term effects of new Q waves on survival and morbidity after coronary bypass graft surgery (CABG). We followed 1340 patients who underwent CABG in 1978 at 10 hospitals participating in the Coronary Artery Surgery Study (CASS). The incidence of perioperative Q-wave infarction was 4.76% (range 0.0-10.3% by hospital). The rate of infarction was higher in patients who had an increased left ventricular end-diastolic pressure or cardiomegaly on the preoperative chest radiograph. Patients who received more grafts or who had longer cardiopulmonary bypass time were also at higher risk of infarction. In a stepwise discriminant analysis of 44 clinical, angiographic and surgical variables, cardiopulmonary bypass time, topical cardiac hypothermia and cardiomegaly entered the stepwise selection of variables. Long-term survival was adversely affected by the appearance of new postoperative Q waves. The hospital mortality was 9.7% in the 62 patients who had new postoperative Q waves and 1.0% in the 1278 patients who did not (p less than 0.001); the 3-year cumulative survival rates were 85% and 95%, respectively (p less than 0.001). In patients who survived to hospital discharge, the presence of new postoperative Q waves did not adversely affect 3-year survival (94% and 96%, respectively). The survival rates were worse in patients who had a history of infarction or who had impaired left ventricular function preoperatively. The number of readmissions to hospital after CABG among the patients who had a transmural perioperative infarction was similar to to that among patients who did not. We conclude that the appearance of new Q waves after CABG adversely affects survival. The major impact on mortality occurs before hospital discharge. Patients who are destined to have a perioperative infarct cannot be predicted from commonly measured preoperative and angiographic variables.

Postoperative monitoring of myocardial oxygen tension: experience in 51 coronary artery bypass patients

Following a preliminary feasibility report, polarographic monitoring of myocardial tissue O2 tension (Pmo2) in 51 coronary bypass patients has been accomplished. In this context, the influence of rapid atrial pacing (RAP), O2 inhalation, and intra-aortic balloon assistance (IAB) was statistically analyzed using Wilcoxon sign-rank and Student's t-tests. Electrodes were implanted in revascularized and nonrevascularized areas for comparison (24.0 +/- 1.1; and 26.3 +/- 1.8 mmHg Pmo2, p, not significant). Increasing myocardial O2 demand with RAP caused a 6% PmO2 drop (p less than 0.01). A 70% O2 inhalation increased Pmo2 by 30% (p less than 0.01). In 5 cases the benefit of IAB was confirmed by a 41% increase in Pmo2 (p = 0.02). These data support the clinical usefulness of polarographic Pmo2 as a measure of regional myocardial oxygenation. In addition to early recognition of intraoperative or postoperative graft failure previously reported, the efficacy of various therapeutic interventions can be more precisely determined.

Effect of perioperative myocardial infarction on late survival in patients undergoing coronary artery bypass surgery

From the Seattle Heart Watch angiography registry, the baseline characteristics and late survival of 77 patients who sustained operative infarction (new Q waves) with myocardial revascularization were compared with 1790 patients who underwent coronary artery bypass without perioperative infarction. With the exception of coronary collateral vessels, which were less frequently seen in the patients with perioperative infarction, no baseline or operative characteristic distinguished between the two groups. Late survival was clearly adversely affected by perioperative infarction. Five-year survival was 76% in patients with perioperative infarction, compared with 90% in those with no perioperative infarction.

Extent of myocardial damage after open-heart surgery assessed from serial plasma enzyme levels in either of two periods (1975 and 1980)

Perioperative myocardial damage caused by cardiac surgery in 32 patients operated upon in 1980 is quantified in terms of total quantity of alpha-hydroxybutyrate dehydrogenase released from the heart into the circulation, and compared with perioperative myocardial damage in 32 patients operated upon in 1975. In the five year period between 1975 and 1980, various aspects concerning anaesthesia, pharmacological treatment, and myocardial preservation techniques have been subjected to considerable changes. Comparison of calculated myocardial damage in 1980 with that in 1975 shows a general reduction of about 40% in patients having coronary artery bypass grafting, 75% in patients with aortic valve replacement, and 10% in patients with mitral valve replacement.

Transient bundle branch block following use of hypothermic cardioplegia in coronary artery bypass surgery: high incidence without perioperative myocardial infarction

Hypothermic cardioplegia (HCP) is a method commonly used for myocardial preservation at the time of aortic cross-clamping during coronary artery bypass grafting (CABG). This study assessed the frequency and significance of transient bundle branch block (BBB) in 50 patients undergoing CABG using HCP compared to 61 controls. All patients had normal QRS complexes on preoperative ECG. CLinical, hemodynamic, and operative data were similar in both groups. Seventeen (34%) of the HCP group and four (6%) of the controls developed postoperative BBB (p less than 0.001). These changes were transient in all but three patients in the HCP group. None of the HCP patients with transient BBB had evidence of perioperative myocardial infarction. Clinical and operative parameters did not provide prediction of development of transient BBB. This study demonstrates that transient BBB in the immediate post-CABG period occurs commonly with the use of HCP and does not indicate myocardial necrosis.

Predictors of perioperative myocardial infarction in coronary artery operation

Postoperative graft patency and thirteen perioperative variables were evaluated as potential risk factors for perioperative myocardial infarction (MI) in 102 consecutive patients undergoing coronary artery bypass grafting. Also, the incidence of perioperative MI and the amount of CK-MB released in the postoperative period were compared in three groups of patients selected according to the myocardial preservation technique employed: (1) topical hypothermia with and (2) without aortic cross-clamping and (3) cardioplegia. A perioperative MI as detected by electrocardiogram, enzymes, and myocardial scintigraphy with technetium 99 developed in 15 patients. Most important predictors of perioperative MI were found to be (1) left main and triple-vessel coronary artery disease, (2) a left ventricular end-diastolic pressure greater than or equal to 15 mm Hg, (3) a decreased ejection fraction (p < 0.05), and (4) cardiopulmonary bypass time > 120 minutes (p < 0.01). The incidence of perioperative MI was 50% in patients with three or more risk factors and 7% in those with less than three risk factors (p < 0.001). Graft patency was similar in patients with or without perioperative MI. Differing myocardial preservation techniques did not influence CK-MB release or the incidence of perioperative MI. Thus, the severity of ischemic heart disease and the length of the cardiopulmonary bypass time were important predictors of perioperative MI while graft patency and myocardial preservation technique did not appear to be related to its incidence in this study.

Diagnostic criteria for acute myocardial infarction in patients undergoing coronary artery bypass surgery

Current techniques for diagnosing perioperative myocardial infarction were studied in 58 patients who underwent coronary bypass surgery. All patients had preoperative and postoperative ECGs and technetium-99m stannous pyrophosphate myocardial scintigrams; serum CK-MB was measured immediately after surgery and daily for 3 days. Postoperative bypass graft visualization and left ventriculography were performed before hospital discharge in every patient. Nine patients (16%) had new Q waves postoperatively. Five of these nine patients had positive pyrophosphate scintigrams, postive CK-MB and new wall motion abnormalities, and the remaining four had negative CK-MB, negative phyrophosphate scintigrams and no new wall motion abnormalities. Seven patients (12%) had newly positive postoperative pyrophosphate scintigrams, positive CK-MB and new wall motion abnormalities on postoperative ventriculography, but only four had new Q waves postoperatively. Eight patients (14%) had new wall motion abnormalities; seven had positive pyrophosphate scintigrams and all had positive CK-MB, but only five had new Q waves. Sixteen patients (28%) had positive CK-MB, including all patients with either positive pyrophosphate scintigrams or new wall motion abnormalities, Eight patients had positive CK-MB without other evidence of perioperative infarction. A newly positive postoperative pyrophosphate scintigram is more senstive and specific than the development of new postoperative Q waves for the diagnosis of hemodynamically significatn perioperative myocardial in farction. CK-MB is highly sensitive, but too nonspecific to be useful for the diagnosis of perioperative infarction.

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.

Bypass surgery for left main coronary artery disease. Reduced perioperative myocardial infarction with preoperative intra-aortic balloon counterpulsation

From July 1975 to December 1977, 91 consecutive patients with left main coronary artery disease defined by cardiac catheterisation as greater than or equal to 50 per cent luminal narrowing underwent coronary bypass surgery. Prospective examination of the preoperative and postoperative clinical course of these patients was performed to determine the incidence of perioperative myocardial infarction. Intra-aortic balloon counterpulsation was instituted preoperatively in 35 patients, and these patients were classed as group A. Fifty-six patients did not receive the intra-aortic balloon pump and were classed as group B. Of 26 demographic, clinical, haemodynamic, and operative descriptors, only two were found to be significantly different between the two groups: the severity and the pattern of angina. Group A had a higher percentage of patients with class IV angina (80% vs 45%) and a greater proportion with unstable angina (37% vs 7%). Despite these differences group A patients had only a 3 per cent incidence of perioperative myocardial infraction while group B had a 23 per cent perioperative infarction rate. It is suggested that perioperative intra-aortic balloon counterpulsation can reduce the risk of perioperative myocardial infraction in patients with left main coronary artery stenosis.

Recognition and quantification of myocardial injury by means of plasma enzyme and isoenzyme activities after cardiac surgery

Serial plasma enzyme determinations were carried out in 32 patients who underwent cardiac surgery with the aid of extracorporeal circulation. Plasma creatine kinase (CK), the cardiospecific isoenzyme of CK (CKMB), and alpha-hydroxybutyrate dehydrogenase (HBDH) were determined from the onset of surgery up to 100 to 120 hours after operation. From the plasma enzyme activities, the total amount of enzyme released by the injured heart into the circulation could be calculated using mathematical equations solved numerically by means of a computer. The calculated amount of CK, CKMB, and HBDH released by the heart correlated well with (1) postoperative mortality, and (2) peak activities of the respective enzymes. The calculated amount of any of the 3 enzymes released showed poor or no correlation with (1) electrocardiographic criteria of myocardial infarction, (2) duration of cardiopulmonary bypass, and (3) duration of total aortic cross-clamping. This study shows that the extent of myocardial injury after surgery can be assessed quantitatively using the calculated amounts of enzyme released, as well as using peak plasma activities of CKMB and HBDH.

A high risk subgroup of patients with unstable angina pectoris treated medically or surgically

Among patients consecutively admitted to a coronary care unit (CCU) without a subsequent diagnosis of acute myocardial infarction (AMI), a subgroup fo unstable angina was selected, defined as continued episodes of angina at rest during a 48-hour period, despite medical treatment in the CCU. During a four-year period, 15 patients fulfilled these criteria. Eight patients were medically treated, seven of whom developed an AMI with three subsequent deaths. Six of the infarcts occurred within eight days of admission. In six patients, fulfilling the criteria, surgical treatment was performed. Angiography and surgery in this group were associated with low incidences of myocardial infarction, late infarction and death. In one patient, surgery was declined due to unfavourable anatomical conditions. This patient subsequently developed an AMI and died. It is concluded that the combination of recent onset of angina and continued episodes of angina at rest, despite medical treatment, selects a high risk subgroup of unstable angina. Acute coronary angiography and surgery ought to be considered in this subgroup.

Perioperative myocardial infarction associated with coronary artery bypass graft surgery: improved sensitivity in the diagnosis within 6 hours after operation with 99mTc-glucoheptonate myocardial imaging and myocardial-specific isoenzymes

The present study was performed to evaluate scintigraphic imaging with technetium 99m-labeled glucoheptonate and serum enzyme levels of creatine phosphokinase isoenzyme (MB-CPK) in the early diagnosis of perioperative acute myocardial infarction associated with saphenous vein bypass graft operations. Myocardial imaging was done in 27 patients (50% of whom were considered high-risk) before operation and again 5 hours after operation. Four of these patients (15%) had both electrocardiographic and serum MB-CPK evidence of acute myocardial infarction, and all 4 had developed positive postoperative scintigrams. Four other patients had only elevated serum MB-CPK, and scintigrams became positive after operation in 3 of them. In addition, serum MB-CPK 6 hours after operation was 83 +/- 21 mIU/ml (mean +/- standard error of the mean) in patients with positive postoperative scans compared with 24 +/- 5 mIU/ml in those patients with negative postoperative scintigrams (p less than 0.001). Myocardial imaging with 99mTc-glucoheptonate in the perioperative period is rapid, safe, and atraumatic. Furthermore, our results suggest that it is a sensitive method for the early diagnosis of perioperative acute myocardial infarction, and, when imaging is combined with serum MB-CPK isoenzyme analysis, the reliability of the diagnosis of acute myocardial infarction is enhanced even further. Only 1 of the patients who showed perioperative myocardial damage had acute hemodynamic compromise or obvious impairment of recovery in the immediate postoperative period, and the 30-day mortality of the total group was 4% (1 of 27).

Electrocardiographic pseudo-infarction pattern: appearance with a large posterior pericardial effusion after cardiac surgery

Two patients with a large posterior pericardial effusion after cardiac surgery presented with electrocardiographic precordial Q waves without evidence of myocardial infarction. Resolution of the pericardial fluid resulted in the disappearance of the Q waves. Changes in conductivity and orientation of the heart within the pericardial space, along with a decrease in QRS voltage, could lead to the loss of initial R waves in the precordial leads, eventually resulting in a QS complex. Care should be taken in interpreting the electrocardiogram after cardiac surgery in patients with a large posterior pericardial effusion. The clinical course along with serial electrocardiographic and echocardiographic tracings should be helpful in identifying this false infarction pattern.

Positive myocardial scintigraphy at the bedside--evaluation using a portable gamma camera

A study was undertaken to evaluate the role of positive infarct scintigraphy in the diagnosis of acute myocardial infarction (AMI), using Technetium99m stannous pyrophosphate (Tc-PYP) and a portable gamma camera. Sixty-one patients admitted to the Coronary Care Unit (CCU) with a presumptive diagnosis of AMI or ischaemic cardiac pain were studied. Positive scans were present in 24/25 (96%) patients with AMI and new Q waves, and in 10/12 (83%) patients with AMI and no Q waves. Nine of eleven (82%) patients with chest pain and no infarction had negative scans. Of thirteen patients with unstable angina, ten (77%) had positive scans. A further eight patients undergoing coronary artery bypass surgery for angina pectoris were studied pre- and postoperatively. Two patients had strongly positive postoperative scans. The Tc-PYP scan is valuable in the detection of peri-operative infarction following coronary artery surgery, and in patients with unstable angina the technique may detect small amounts of myocardial necrosis undetectable by more conventional means. When the diagnosis of infarction is obvious from the ECG, enzymes, or a combination of the two, the Tc-PYP scan provides no extra information helpful in patient management.

Coronary surgery for unstable angina pectoris. Incidence and mortality of perioperative myocardial infarction

The incidence of perioperative myocardial infarction determined by electrocardiogram was examined in 123 consecutive patients having only coronary artery bypass grafting for unstable angina pectoris, at Yale-New Haven Hospital from January 1974 to June 1975. The incidence of myocardial infarction and its mortality were correlated with clinical, haemodynamic, anatomical, and operative factors. Myocardial infarction occurred in 18% of all patients (22/123); 15 inferior, 6 anterior, and 1 anterolateral wall. Three factors appeared to be related to the occurrence of myocardial infarction: left main coronary artery disease (LMCD), (47%, 7/15), increased left ventricular end-diastolic pressure (LVEDP), (27%, 14/52), and cardiopulmonary bypass time more than 60 minutes (24%, 21/88). The mortality of perioperative myocardial infarcation was 13.6% (3/22), while for patients without perioperative myocardial infarction the mortality was 2% (2/101). The overall operative mortality was 4% (5/123). The risk of perioperative myocardial infarction is significantly increased by left main coronary artery disease, increased left ventricular end-diastolic pressure, and cardiopulmonary bypass time more than 60 minutes, in patients undergoing coronary artery surgery for unstable angina pectoris. The mortality of perioperative myocardial infarction is high (13.6%) in patients with unstable angina.

Fascicular conduction distrubances after coronary bypass surgery

Two hundred patients underogoing coronary bypass graft surgery were studied to determine the frequency and significance fo new fascicular conduction distrubances. The follow-up period ranged from 13 to 39 months. New disturbances developed in 39 patients (20 percent). Isolated right bundle branch block (6 percent) and left anterior hemiblock (6 percent) were the most common disturbances. Righ bundle branch block was usually transient and was not associated with further complications in the follow-up period. However, patients with either transient or persistent left bundle branch block or left anterior hemiblock, or both, had (1) increased later mortality compared with patients without new fascicular conduction disturbances (5 of 26 versus 11 of 161; P less than 0.02), and (2) increased late myocardial infarction (2 of 26 versus 2 of 161; P less than 0.05). New left fascicular conduction disturbances after coronary surgery identified a subset of patients with more extensive ischemic heart disease, suggesting that these patients require close follow-up care.

Significance of new Q waves after bypass grafting: correlations between graft patency, ventriculogram, and surgical venting technique

New postoperative electrocardiographic Q waves have been described in eight of 40 per cent of patients undergoing bypass grafting for coronary artery disease. Various theories have been proposed to explain these new Q waves. Correlations of new Q waves to vein bypass occlusion, prolonged pump time or aortic cross-clamping time are controversial. Indeed, whether or not the appearance of new postoperative Q waves means real transmural myocardial infarction is not clear. We report herein our experience with postoperative Q waves in 56 patients with vein bypass grafts and the relationship of new Q waves to ventricular venting, graft patency, and the postoperative ventriculogram. Our observations indicate that: (1) Not all Q waves are due to occlusion of the saphenous bypass grafts (as noted by others). (2) A certain percentage of new Q waves may not reflect true transmural myocardial infarction, especially when all the vein grafts are patent and the postoperative ventriculograms show improvement. (3) Some new Q waves reflect true transmural infarction due to occlusion of grafts or of distal coronary arteries with deteriorated left ventriculograms. (4) The high incidence of new Q waves in patients with ventricular vents is probably due to direct myocardial trauma at the apex of the left ventricle.

The first decade of aortocoronary bypass grafting, 1967-1977. A review

Despite a decade of experience with aortocoronary bypass grafting embracing 300,000 or more operations, indications for its use remain controversial. The controversy persists because of a lack of adequate controls with which to compare the clinical course of operated patients; only 1248 have been reported who have been studied in a carefully controlled and random manner. Benefit has been claimed frequently by comparing the course of patients treated surgically with medically treated patients followed the decade before. Such comparisons are not valid in view of the well documented changes in the natural history of coronary artery disease that have been occurring during the last decade. Despite a low operative mortality and rate of graft closure, available data in the literature do not indicate that initial symptomatic improvement necessarily persists, or that myocardial infarctions, arrhythmias, or congestive heart failure will be prevented, or that life will be prolonged in the vast majority of operated patients.

Myocardial consequences of coronary artery bypass graft surgery. The paradox of necrosis in areas of revascularization

Myocardial infarction after coronary artery bypass graft (CABG) surgery has been described clinically in up to 30% of patients but there is little morphologic information about the character and pathogenesis of the myocardial injury. We studied myocardium in the distribution of bypassed and nonbypassed coronary arteries for the presence of contraction band necrosis as compared to coagulation necrosis, in 58 autopsied patients who died less than 1 month after surgery. Operation related necrosis consisting of focal subendocardial contraction band necrosis was present to some degree in 48 (83%) patients. Regional transmural necrosis was present in 22 (38%) patients and was of two types. Contraction band necrosis occurred in 18 patients and was in the distribution of a patent bypassed coronary artery in 15 of them. Coagulation necrosis was found in four patients, and in each was in the distribution of a new graft-releated coronary artery occlusion. The results suggest that coronary artery reflow through widely patent grafts following the period of operative nonperfusion, rather than graft or intrinsic coronary artery occlusion, accounts for the majority of operation-related myocardial "infarcts" associated with CABG surgery. Thus, prevention of intraoperative myocardial injury must also focus on characteristics of the phase of myocardial reperfusion.