Radionuclide assessment of aortocoronary bypass surgery.

Rest and exercise thallium 201 myocardial scintigraphy and multiple gated radionuclide angiography were correlated with the results of clinical status, exercise electrocardiography, coronary arteriography, and contrast left ventriculography in a series of 12 prospectively studied consecutive patients before and after aortocoronary bypass operation. Patients were divided into two groups based on a comparison between preoperative and postoperative 201T1 scintigrams. Group 1 (6 patients) demonstrated improved or normal postoperative perfusion scintigrams and excellent correlation between the site of a patent graft and the improvement in myocardial perfusion on the postoperative exercise scintigrams. Regional wall motion remained normal in 3 patients and improved in 3. In Group 2 (6 patients) the postoperative 201T1 scintigrams were unchanged or worse. Each patient demonstrated graft occlusion, graft stenosis, distal disease, or a perioperative myocardial infarction. No improvement in regional wall motion occurred in 4 of these 6 patients. Neither the symptomatic response to aortocoronary bypass operation nor the response to exercise testing successfully predicted graft patency.     

Electrocardiography, cardioenzymes and myocardial imaging to detect perioperative myocardial infarction

Serial electrocardiography, technetium-99m pyrophosphate scintigraphy and measurement of myocardial creatine kinase (CK2) and lactic dehydrogenase isoenzyme activity (specifically the LD1 to LD2 ratio) were evaluated prospectively in 26 patients who underwent aortocoronary bypass grafting and 11 patients who underwent valvular or other thoracic surgery, as methods of diagnosing perioperative myocardial infarction. Of the 26 patients who had aorto coronary bypass grafting, 7 (group 1) had myocardial infarction perioperatively; of these, only 2 had positive results from all four diagnostic tests. The other 19 patients (group 2) had no perioperative myocardial infarction and the only diagnostic method yielding positive results was the LD1 to LD2 ratio, in 7 of the 19. In the 11 patients who did not undergo aortocoronary bypass grafting (group 3), only 1 patient had myocardial infarction perioperatively; results from the measurement of CK2 isoenzyme activity and LD1 to LD2 ratio were positive while electrocardiography and 99mTc pyrophosphate scintigraphy yielded negative results. The respective sensitivity (%) and specificity (%) of the four diagnostic methods were as follows: electrocardiography: 38, 100; 99mTc pyrophosphate scintigraphy: 88, 100; LD1 to LD2 ratio: 100, 68; CK2: 38, 100. When the CK2 criterion was redefined, using patients in group 2 as controls, the sensitivity and specificity of this method became 100 and 90 respectively. The authors conclude that 99MTc pyrophosphate scintigraphy and measurement of myocardial creatine kinase isoenzyme are of comparable value and are the most reliable indicators of perioperative myocardial infarction.     

Myocardial infarction after aortocoronary bypass: etiologic factors.

To ascertain the frequency and probable determinants of myocardial infarction after aortocoronary bypass, two groups of patients were studied: a group of 20 patients who underwent valve replacement of repair of congenital anomalies and a group of 24 patients who underwent aortocoronary bypass. Postoperative myocardial infarction was diagnosed by an increase in serum creatine phosphokinase concentration to a minimum of 1200 IU in two consecutive samples. The frequency of myocardial infarction differed between the groups, being only 5% in group 1 but 20.4% in group 2. In the patients undergoing coronary artery surgery, the duration of bypass, the aortic cross-clamp time and the vent site did not influence the rate of infarction. However, the incidence of myocardial necrosis did correlate with the number of vessels bypassed. In no case was the clinical course influenced by the infarction. Our results suggest that the frequency of perioperative infarction is higher in coronary artery surgery than in other adult cardiac surgery, and that the most important determining factor is the number of diseased vessels.     

Perioperative myocardial infarction and changes in left ventricular performance related to coronary artery bypass graft surgery

Recent advances in perioperative management and surgical technique have been associated with low operative mortality and a high incidence of symptomatic relief in patients undergoing coronary artery bypass graft (CABG) operations. The frequency and importance of perioperative myocardial infarction (MI) and immediate as well as long-term changes in left ventricular (LV) performance are factors of considerable current interest in any critical analysis of the effectiveness of CABG surgery. The present review describes the effects of patient selection, anesthetic techniques, and newer methods of myocardial protection as they relate to perioperative MI and LV performance. In addition, newer tests useful in the diagnosis of perioperative MI are discussed. The application of noninvasive techniques for the serial determination of LV performance and myocardial perfusion in CABG operations is also described.     

Perioperative myocardial infarction in patients undergoing myocardial revascularization surgery

Introduction

Perioperative myocardial infarction adversely affects the prognosis of patients undergoing coronary artery bypass graft and its diagnosis was hampered by numerous difficulties, because the pathophysiology is different from the traditional instability atherosclerotic and the clinical difficulty to be characterized.

Objective

To identify the frequency of perioperative myocardial infarction and its outcome in patients undergoing coronary artery bypass graft.

Methods

Retrospective cohort study performed in a tertiary hospital specialized in cardiology, from May 01, 2011 to April 30, 2012, which included all records containing coronary artery bypass graft records. To confirm the diagnosis of perioperative myocardial infarction criteria, the Third Universal Definition of Myocardial Infarction was used.

Results

We analyzed 116 cases. Perioperative myocardial infarction was diagnosed in 28 patients (24.1%). Number of grafts and use and cardiopulmonary bypass time were associated with this diagnosis and the mean age was significantly higher in this group. The diagnostic criteria elevated troponin I, which was positive in 99.1% of cases regardless of diagnosis of perioperative myocardial infarction. No significant difference was found between length of hospital stay and intensive care unit in patients with and without this complication, however patients with perioperative myocardial infarction progressed with worse left ventricular function and more death cases.

Conclusion

The frequency of perioperative myocardial infarction found in this study was considered high and as a consequence the same observed average higher troponin I, more cases of worsening left ventricular function and death.     

Aortocoronary graft flow and reactive hyperaemia in relation to postoperative myocardial infarction.

Blood flow through aortocoronary venous grafts and its response to a brief period of arterial occlusion--reactive hyperaemia--were studied in relation to the development of postoperative myocardial infarction. In 40 patients with intractable angina due to obstructive coronary artery disease, 72 aortocoronary venous grafts were constructed. In 18% of the grafts there was no response to the flow to temporary occlusion, due to absence of reactive hyperaemia. In the remaining grafts the flow increased from 17% to 26%. In 17-5% of the patients postoperative myocardial infarction was diagnosed. No relation could be established between this control flow through aortocoronary grafts and postoperative myocardial infarction. A significant difference was found in the magnitude of the reactive hyperaemia following occlusion of the graft between patients who developed myocardial infarction (13-0%) and those who did not (26-8%). Some of our observations suggest that the myocardium is in a state of reactive hyperaemia after coronary surgery. With certain technical precautions the flow changes caused by reactive hyperaemia can be used as an indicator of the result to be expected from bypass surgery.     

Preoperative coronary artery bypass grafting in patients undergoing abdominal aortic reconstruction

The effect of preoperative aortocoronary bypass grafting on the operative mortality of patients undergoing elective abdominal aortic reconstruction was examined by reviewing a series of 224 consecutive patients (1980 to 1983) (Group I) in whom selective preoperative noninvasive and invasive cardiac screening was used to identify patients with significant coronary stenoses. One patient died during cardiac catheterization. Twenty-seven patients (12 percent) underwent aortocoronary bypass grafting with one operative death (3.7 percent) and one nonfatal myocardial infarction (3.7 percent). These 26 patients subsequently underwent abdominal aortic reconstruction with no mortality and no postoperative myocardial infarction. One hundred ninety-six patients (88 percent) underwent aortic reconstruction without prior aortocoronary bypass grafting with four operative deaths (2 percent), including two fatal myocardial infarctions. The combined operative mortality for Group I patients was 2.3 percent. Three hundred twenty-six patients (Group II) who underwent abdominal aortic reconstruction at this institution from 1970 to 1976 had an 8 percent operative mortality, of which 50 percent of the deaths were due to myocardial infarctions (Group I versus Group II, p less than 0.01). Selective preoperative screening for coronary artery disease in patients undergoing elective abdominal aortic reconstruction with aortocoronary bypass grafting in selected patients is safe and may help reduce the operative mortality.     

Giant aneurysm of saphenous vein graft to coronary artery compressing the right atrium.

Aneurysm of reverse aortocoronary saphenous vein graft is a known complication of coronary artery bypass grafting. In this report we present a case of a 60-year-old man who presented 12 years after coronary artery bypass grafting with a giant graft aneurysm of the reverse aortocoronary saphenous vein graft to the right coronary artery, compressing the right atrium. Spiral computed tomography was used to identify the aneurysm measuring 7 x 6 x 7 cm. We also reviewed the English-language literature and found reports of 50 patients with similar aneurysms of which 30 (61%) were identified as true aneurysms and 17 (33%) were identified as pseudoaneurysms. Three patients could not be identified into either group. We reviewed the presenting symptoms, diagnostic tools, and treatment options for this rare entity. An understanding of the pathophysiology of reverse aortocoronary saphenous vein graft aneurysm is important to prevent the possibility of aneurysm rupture, embolization, myocardial infarction, or death.     

Activation of hemostasis and perioperative ischemia]

The prevention of perioperative myocardial ischemia is one of the cornerstones of anesthetic techniques. From the perspective of anesthesiologists, the traditional relation between oxygen supply and demand is improved mainly by reducing demand. Cardiologists, however, look at the problem from the other side of the equation.For the cardiologist, myocardial infarction is an entirely thrombotic event caused by changes in procoagulants, regardless of increased demand for oxygen. It is conceivable that signs of perioperative myocardial ischemia, which are related to increased oxygen demand, are equivalent to stable angina. Rarely do they cause myocardial infarction. However, transient occlusion or embolization from an unstable plaque can cause ischemia unrelated to increased demand.Cardiac morbidity during the perioperative period is insufficiently explained by the traditional concept of increased myocardial oxygen demand during surgery. On the contrary, evidence suggests that infarction depends on changes in oxygen supply secondary to transient or permanent episodes of thrombotic vascular occlusion. Our data suggest that these thrombotic events are dependent on hypercoagulability.It may be that anesthesiologists should focus on preventing rupture of the atherosclerotic plaque or on examining changes in coagulation, given that such events might facilitate the appearance of thrombosis in coronary arteries with unstable plaques.     

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.     

Cardiac protection by volatile anesthetics. A review

All volatile anesthetics have cardiac depressant effects that decrease myocardial oxygen demand and may thus improve the myocardial oxygen balance during ischemia. Recent experimental evidence has clearly demonstrated that, in addition to these indirect effects, volatile anesthetic agents also directly protect from ischemic myocardial damage. Implementation of these effects during clinical anesthesia can provide an additional tool for treatment or prevention of ischemic cardiac dysfunction during the perioperative period. A recent meta-analysis showed that desflurane and sevoflurane reduce postoperative mortality and the incidence of myocardial infarction following cardiac surgery, with significant advantages in terms of postoperative cardiac troponin release, need for inotropic support, and time on mechanical ventilation, as well as in time spent in the intensive care unit and overall hospital stay. Multicenter, randomized clinical trials previously demonstrated that desflurane could reduce the postoperative release of cardiac troponin I, the need for inotropic support, and the number of patients requiring prolonged hospitalization following coronary artery bypass graft surgery, either with or without cardiopulmonary bypass. However, evidence in non-coronary surgical settings is contradictory and will be reviewed in this paper, together with the mechanism of cardiac protection by volatile agents.     

Perioperative cardiac complications of surgical repair of infrarenal aortic aneurysms

From 1985 to 1987, 261 patients (241 male, 20 female; mean age 66.5 years, range 38-90 years) were hospitalized for elective repair of infrarenal aortic aneurysms. One-hundred forty seven patients (56%) had coronary artery disease, attested to by past history of myocardial infarction or angina pectoris, electrocardiographic signs at rest, or abnormalities of dipyridamole thallium scintigraphy (performed in 72 patients). Ten patients had coronary arteriography and one patient then underwent aortocoronary bypass. Only two patients were not offered operation. All patients operated on had perioperative monitoring using Swan-Ganz catheters. Forty-five patients (17.5%) had a total of 62 postoperative events related to coronary artery disease. These included 40 cases of myocardial ischemia (15%), 16 cases of left heart failure (6%), and six myocardial infarctions (2%). There were nine (3.4%) postoperative deaths, four of which were due to cardiac causes (1.5%). In spite of the frequency of preexisting coronary artery disease and of intra- or postoperative myocardial ischemia, surgical repair of abdominal aortic aneurysm was not responsible for increased perioperative cardiac morbidity or mortality. In this population of aged patients, abdominal aortic aneurysm repair does not necessitate extending the indications for preoperative coronary arteriography or aortocoronary bypass.     

围术期心肌缺血和心肌梗死研究进展

背景 围术期多种因素可能导致心肌缺血和心肌梗死,了解其发生机制,有效预防,可降低围术期心脏事件发生率.目的 探讨围术期心肌缺血和心肌梗死的发生机制及有效预防措施.内窖冠状动脉粥样硬化后冠脉内皮对交感神经、副交感神经兴奋的反应性发生改变以及围术期特殊的病理生理状态是围术期心肌缺血和心肌梗死发生的主要机制.对于冠心病患者加...     

围术期心肌缺血和心肌梗死研究进展

背景 围术期多种因素可能导致心肌缺血和心肌梗死,了解其发生机制,有效预防,可降低围术期心脏事件发生率.目的 探讨围术期心肌缺血和心肌梗死的发生机制及有效预防措施.内窖冠状动脉粥样硬化后冠脉内皮对交感神经、副交感神经兴奋的反应性发生改变以及围术期特殊的病理生理状态是围术期心肌缺血和心肌梗死发生的主要机制.对于冠心病患者加强围术期心肌缺血和心肌梗死的监测与诊断,加强围术期药物治疗维持斑块稳定性、维持氧供需平衡,并完善术后镇痛、加强保温、避免血糖过高可减少围术期心肌缺血和心肌梗死的发生.趋向 冠心病患者非心脏手术前常规预防性药物的治疗时间与获益的关系以及术前冠脉重建的价值尚需进一步探讨.     

Perioperative myocardial protection in severe coronary artery and valvular heart diseases with impaired ventricular function

One hundred patients with severe coronary artery disease, and impaired left ventricular function were studied. Thirteen of these required valve replacements. Eight required repair of a left ventricular aneurysm. In addition, all these patients had three or more coronary artery diseases. The patients underwent aortocoronary bypass using saphenous vein grafts. For myocardial protection, general and topical hypothermia was used during the procedure, along with perfusion of the root of the aorta, with a cardioplegic solution. Additional cardioplegic perfusion was achieved by perfusing the vein graft anastomosed to the left anterior descending coronary artery below the obstruction, or other vein grafts anastomosed to the circumflex artery or the right coronary artery (or its branches if dominant), during total aortic clamping. No mortality occurred in these patients. Only two patients developed perioperative myocardial infarction, but they recovered. The authors believe that this method can offer further myocardial protection during ischemic arrest.     

Congenital atresia of the left main coronary artery ostium.

Three patients with the rare anomaly of congenital absence of the ostium of the left main coronary artery are presented. In two of the patients, aged 50 and 52 respectively, the diagnosis was established during selective coronary cineangiography for a severe anginal syndrome. The third patient, a 16-year-old-girl, underwent cardiac catheterization for investigation of a congenital heart malformation, when a single right coronary artery was demonstrated with absence of the main coronary artery ostium. Two patients underwent successful aortocoronary bypass grafting. In view of the occurrence of sudden death and massive myocardial infarction in adult patients shown to have severe or complete obstruction of the left main coronary artery, it is suggested that adult patients with this condition, who require open-heart surgery for any other cardiac disorder, should undergo aortocoronary bypass grafting concurrently even prior to the development of anginal symptoms. Children shown to have this anomaly should be subjected to long-term follow-up and have an aortocoronary bypass graft performed when symptoms of coronary insufficiency develop.     

Hemodynamic effect of calcium channel blockade during anesthesia for coronary artery surgery.

Because the choice of anesthetic technique does not influence the incidence of perioperative myocardial ischemia, reduction of ischemic risk may require specific antianginal therapy. Calcium entry blockers are effective drugs in antianginal therapy. Diltiazem reduces myocardial oxygen demand through decreases in heart rate, inotropy, and systolic function, while increasing myocardial oxygen delivery through coronary vasodilation. These potentially beneficial effects of diltiazem were evaluated in 15 of 29 patients (diltiazem v placebo, double-blind study) scheduled for coronary artery bypass graft surgery. Continuous infusion of diltiazem (0.15 mg/kg bolus followed by 2 micrograms/kg/min), during anesthesia and surgery before cardiopulmonary bypass, significantly reduced the major MVO2 determinants during anesthesia with moderate doses of fentanyl and a benzodiazepine (midazolam in 8 of 14 control patients and 9 of 15 treated patients, or flunitrazepam in the others). Heart rate, mean arterial pressure, and inotropy were decreased during the most stressful events of surgery when plasma diltiazem concentrations were in the therapeutic range (greater than 96 ng/mL). The number of patients with perioperative ischemia was 2 of 15 in the treated group and 4 of 14 in the control group. Provided that diltiazem plasma concentrations are sufficient, it can contribute to lowering the ischemic burden during anesthesia for coronary artery surgery.     

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 enddiastolic pressure ≥ 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.     

Approaches to the prevention of perioperative myocardial ischemia

Goals for the perioperative management of patients with coronary artery disease include: * Prevent increases in sympathetic nervous system activity: reduce anxiety preoperatively; prevent stress response and release of catecholamines by appropriate use of opioids or volatile anesthetics and beta-adrenoceptor antagonists; beta-blocker therapy should be initiated before and continued during and after the surgical procedure. * Decrease heart rate: reduction in heart rate increases oxygen supply to ischemic myocardium and reduces oxygen demand; the use of beta-blockers is the most effective means to reduce or attenuate deleterious increases in heart rate. * Preserve coronary perfusion pressure: decreases in diastolic arterial pressure in the presence of severe coronary artery stenoses will lead to decreases in blood flow; preservation of perfusion pressure by administration of fluid or phenylephrine or a reduction in anesthetic concentration may be critical. * Decrease myocardial contractility: reduces myocardial oxygen demand and can be accomplished with beta-adrenoceptor antagonists or volatile anesthetics. * Precondition myocardium against stunning and infarction: in the future, this may accomplished by stimulating the adenosine triphosphate- dependent potassium channel with agents such as volatile anesthetics and opioid delta1-receptor agonists.     

Successful excision of a saphenous vein graft aneurysm with different methods

Aneurysm of an aortocoronary saphenous vein graft (SVG) is a rare but potentially fatal complication after coronary artery bypass grafting (CABG). Prevention of cerebral infarction or myocardial infarction due to the intraluminal debris from the SVG aneurysm is an important issue during surgical procedures. We report two patients with SVG aneurysms located in the proximal and distal portions of the SVG body, respectively. The surgical strategy for each case was determined according to the location of the aneurysm. We used low-flow cardiopulmonary bypass without aortic clamping in one patient and cardiac arrest with aortic clamping in the other. Both patients were discharged without sequelae.