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 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.     

Long-term prognosis after myocardial infarction in patients with previous coronary artery bypass surgery

A group of 205 patients hospitalized with myocardial infarction 2 to 162 months (mean 66) after bypass surgery and 205 control patients with myocardial infarction were compared and followed up for 34 +/- 25 months after hospital discharge. At baseline the postbypass group contained more men (p less than 0.03) and more patients with previous myocardial infarction (p less than 0.06), but the groups were otherwise comparable. Indexes of infarct size were lower in postbypass patients: sum of ST elevation, QRS score, peak serum creatine kinase (CK) (1,115 +/- 994 versus 1,780 +/- 1,647 IU/liter) and peak MB CK (all p less than or equal to 0.001). Postmyocardial infarction ejection fraction was 45 +/- 15% in the postbypass group and 43 +/- 15% in the control group (p = NS); in-hospital mortality rate was 4 and 5%, respectively (p = NS). When patent grafts were taken into account, the two groups were comparable in extent of coronary artery disease. At 5 years after discharge, cumulative mortality was similar in the postbypass and control groups (30 versus 25%, respectively, p = NS). However, postbypass patients had more reinfarctions (40 versus 23%, p = 0.007), more admissions for unstable angina (23 versus 18%, p = 0.04) and more revascularization procedures (34 versus 20%, p = 0.04) than did control patients. The total for these events at 5 years was 70% in the postbypass group and 49% in the control group (p = 0.001). Thus, although patients with previous bypass surgery who develop acute myocardial infarction have a smaller infarct, their subsequent survival is no better than that of other patients with acute myocardial infarction. They experience more reinfarctions and unstable angina. Previous bypass surgery is an important clinical marker for recurrent cardiac events after myocardial infarction.     

Myocardial infarction in patients with previous coronary artery bypass surgery

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

Quantification of peri-operative myocardial infarction after coronary artery bypass surgery.

Dear Editor, In a recent study in the Journal, Steuer and colleagues¹ reportthat elevated biochemical markers after on-pump CABG correspondto the amount of peri-operatively infarcted myocardium as measuredby delayed-enhancement cardiac MRI (DE-MRI). They found that18 out of 23 (78%)     

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.     

Ventricular arrhythmias after coronary artery bypass graft surgery: incidence, risk factors and long-term prognosis

The incidence, risk factors and long-term prognosis of complex ventricular arrhythmias after coronary artery bypass graft surgery are not known. Complex ventricular arrhythmias are defined as Lown grades 4a (couplets), 4b (ventricular tachycardia) and 5 (R on T phenomenon). Ninety-two patients with normal left ventricular function who underwent elective coronary artery bypass graft surgery were prospectively evaluated. Ventricular arrhythmias were documented by predischarge 24 hour ambulatory electrocardiographic monitoring; 43% of patients had no or simple ventricular arrhythmias (Lown grades 1 to 3) and 57% had complex ventricular arrhythmias. Risk factors analyzed included age, sex, diabetes, hypertension, smoking, preoperative digoxin or propranolol therapy, cardiopulmonary bypass time, aortic cross-clamp time, number of vessels bypassed, peak creatine kinase (CK) elevation and pericarditis. No risk factor identified patients at higher risk for complex ventricular arrhythmias. Patients were followed up for 6 to 24 months (mean 16). Patients with complex ventricular arrhythmias did not have a higher incidence of sudden death, cardiac death, syncope, angina, myocardial infarction or cerebrovascular accident. It was concluded that: Complex ventricular arrhythmias are common after coronary artery bypass graft surgery. None of the risk factors considered identify high risk patients. Complex ventricular arrhythmias after coronary artery bypass graft surgery do not indicate a poor prognosis in patients with normal left ventricular function.     

Risk factors for myocardial infarction during coronary artery bypass graft surgery

Patients with a particular thrombotic profile may be at greaterrisk of myocardial infarction during coronary artery bypassgraft surgery. The thrombotic profile of 50 patients admitted to hospital withstable angina pectoris was determined prior to haemodynamicinvestigation. ECG results and determination of cardiac enzymesshowed that 12 patients had suffered a perioperative myocardialinfarction. These patients had a higher mean atheroscleroticscore (42.1 ± 10.5 vs 32.9 ± 13, P<0.02), alonger aortic cross clamp time (59 ± 15.2 vs 45.7 ±16.3 min, P < 0.05), lower serum levels of protein C (101.2±26vs 124.7+ 31.4%, P<0.05) and tissue plasminogen activator(322 ± 580 vs 2307±2830 IU ml^–1, P<0.01). There were no differences between the two groups in Jenkin'scoronary score, the number and type of grafts, ejection fraction,left ventricular end-diastolic pressure, lipid profile or levelsof markers of platelet release. In addition to a more severe distal coronary atheroma and alonger aortic cross-clamp time, patients with impaired endothelialfibrinolytic activity appeared to be at greater risk of myocardialinfarction during coronary artery bypass graft surgery.     

Emergency coronary artery bypass surgery after intracoronary thrombolysis for evolving myocardial infarction.

Sixteen patients underwent emergency coronary artery bypass surgery immediately after intracoronary streptokinase infusion for acute evolving myocardial infarction. Of these, 11 patients had 70% residual stenosis in the recanalised vessel, and in five thrombolysis was unsuccessful. There were no hospital deaths. All the patients sustained myocardial necrosis, the peak activity of creatine phosphokinase correlating with the time to reperfusion. Chest tube drainage (mean 960 ml) was significantly higher than for control patients but did not correlate with the total dosage of streptokinase. No patients had further myocardial infarction or developed recurrent angina. Selected patients may benefit from coronary bypass surgery after intracoronary streptokinase infusion. If necessary this may be performed immediately with low mortality and morbidity.     

冠状动脉搭桥围术期急性心肌梗死紧急再搭桥

目的：回顾性分析冠状动脉搭桥围术期急性心肌梗死急诊再搭桥的临床经验。方法：在510例冠状动脉搭桥患中，5例患在术后4h内因急性心肌梗死需急诊再搭桥，发生率0．98％。5例患中，男女比例为4：1，年龄56－77岁（平均63．6岁），均为冠状动脉三支血管病变（3例伴左主干病变），手术中搭桥3－5支（人均搭桥3．6支），左乳内动脉桥5根，其余为大隐静脉桥。2例在关胸后20min，3例在回重症监护病房后2－4h出现急性心肌缺血表现（明显心电图ST－T变化），伴室颤2例，5例血液动力学均不稳定，药物处理难以稳定血液动力学。全部患均立即送手术室（2例仍在手术室），急诊再次开胸。探查发现，2例患静脉桥（分别搭桥到回旋支第二钝缘支和右冠状动脉后降支）内急性血栓形成；另3例所有静脉桥良好，但左室前壁收缩运动明显减弱，结合心电图变化，诊断为左乳内动脉灌注不良。重新建立体外循环，清除桥内血栓重新搭桥2例（1例在非体外循环心脏跳动下进行）；另取一段静脉搭桥到左乳内动脉－左前降支吻合口远端的左前降支3例。结果：5例患顺利度过手术，均置入主动脉内球囊反搏，支持22－25h（平均42h）。手术后呼吸机支持4h－18d（平均7．3d）合并消化道出血4例，肾功能不全2例，肺部感染2例，切口感染1例。手术后住院时间12－35d，平均21d。全组均痊愈出院。结论：冠状动脉搭桥围术期急性心肌梗死应重在预防。如怀疑桥有问题，急诊再搭桥是良好选择，但手术后并发症发生率明显增加。     

Perioperative myocardial infarction related to coronary bypass surgery.

Frank lead electrocardiograms were recorded from 149 normal and abnormal adult males using four different electrode placements. All chest electrodes were placed at: (1) the fourth intercostal space level, (2) the fifth intercostal space level, (3) the fourth intercostal space level with V₄ substituted for C, and (4) the fifth intercostal space level with V₄ substituted for C.Differences in mean values of many commonly used amplitudes and orientations were not statistically significant among the four recording methods, but amplitude differences for individual subjects were often large and difficult to predict. When V₄ is substituted for C, as commonly done in some laboratories, R_x decreased and R_z increased by more than 10 per cent in about 40 per cent of the cases. In about 70 per cent of the cases, R_x and R_z changed significantly when electrode level was shifted from the fifth to the fourth intercostal space. For these 70 per cent, it does not appear possible to accurately predict increase or decrease of R_x, R_z, or QRS_m.Analysis programs which depend on individual amplitude measurements are likely to be significantly affected by electrode placement. It is suggested that criteria for analysis programs developed using a specified version of the Frank system should ideally be applied only to electrocardiograms recorded in the same manner.     

Mortality in patients undergoing coronary artery bypass surgery after myocardial infarction

Data on 1,700 patients who underwent coronary artery bypass surgery without additional cardiovascular procedures at the Texas Heart Institute were analyzed, relating the interval between myocardial infarction and operation to early mortality (within 30 days after operation). Patients who underwent coronary artery bypass surgery after a recent infarction (within 2 months before operation) had a higher rate of early mortality (14.5 percent) than patients who had an old infarction (6.9 percent) or no previous infarction (4.1 percent). The interval between recent infarction and operation was most significant. Mortality in patients who underwent operation within the first 7 days after acute infarction (38.1 percent) was more than six times greater than in patients who were operated on 31 to 60 days after infarction (5.8 percent). Mortality of those operated on 8 to 30 days after infarction was 16.4 percent. Elective coronary artery bypass surgery after recent infarction is best accomplished after the first 30 days, when there is no increased risk to the patient. Emergency coronary artery bypass after complicated acute myocardial infarction may be a lifesaving procedure, but it is associated with increased early mortality and should be reserved for those whose condition has not responded to aggressive medical therapy.     

Myocardial infarction during coronary artery bypass surgery — benign event or prognostic omen?

Our observations and experience suggest that an adverse outcome from perioperative infarction occurs predominantly in a defined population of patients. A worsened prognosis and special postoperative interventions need not be anticipated in patients who have simply developed new Q waves after bypass surgery and are free of malignant ventricular arrhythmias and severe degrees of myocardial dysfunction. Furthermore, our data indicates that repeat throacotomy because of bleeding or tamponade early after sustaining a perioperative infarction will adversely affect the outcome of that infarction.     

Perioperative myocardial infarction in coronary bypass surgery

Thirteen of 199 consecutive patients undergoing coronary artery bypass surgery revealed definite perioperative myocardial infarction (PMI) in electrocardiography (ECG). The occurrence of PMI was not higher in the group of 44 patients who had intermittent aortic cross-clamping than in those patients treated with cold chemical cardioplegia. In 83 patients serum MB isoenzyme of creatine kinase (CK) and LD1 isoenzyme of lactic dehydrogenase were determined. Patients with unchanged ECG had peak CK-MB levels of 0 to 49 U/l (mean 18.7 U/l +/- 2.6 SEM) at 18 hours postoperatively while patients with PMI showed CK-MB levels of 64-350 U/l (mean 207 +/- 53 U/l); the difference was significant (p less than 0.01). In patients with unchanged ECG, LD1 was 139 +/- 19 U/l and 594 +/- 95 U/l in those with PMI (p less than 0.01). Risk factors for PMI were: age greater than or equal to 60 years, coronary endarterectomies, or cardiopulmonary bypass time greater than or equal to 100 minutes. One patient died of PMI while the remaining patients had postoperative courses comparable to those patients without PMI.     

Myocardial infarction after aortocoronary saphenous vein bypass. Vectorcardiographic study.

Vectorcardiograms and scalar electrocardiograms were recorded in 30 patients before and after aortocoronary saphenous vein bypass surgery to determine whether vectorcardiograms are helpful in making the diagnosis of perioperative transmural infarction. The vectorcardiogram indicated inferior infarction in 2 cases and anterior infarction in 1 case when the diagnosis was not apparent on the electrocardiogram. In the solitary case of anterior infarction diagnosed by the electrocardiogram, anterior infarction was already present on the preoperative vectorcardiogram. The study indicates that the recording of vectorcardiograms before and after aortocoronary bypass surgery facilitates the diagnosis of perioperative anterior and inferior infarction and may reveal perioperative infarction about a previously infarcted area.     

Myocardial infarction after aortocoronary saphenous vein bypass. Vectorcardiographic study.

Vectorcardiograms and scalar electrocardiograms were recorded in 30 patients before and after aortocoronary saphenous vein bypass surgery to determine whether vectorcardiograms are helpful in making the diagnosis of perioperative transmural infarction. The vectorcardiogram indicated inferior infarction in 2 cases and anterior infarction in 1 case when the diagnosis was not apparent on the electrocardiogram. In the solitary case of anterior infarction diagnosed by the electrocardiogram, anterior infarction was already present on the preoperative vectorcardiogram. The study indicates that the recording of vectorcardiograms before and after aortocoronary bypass surgery facilitates the diagnosis of perioperative anterior and inferior infarction and may reveal perioperative infarction about a previously infarcted area.