Prävention perioperativer Myokardischämien – ein Update

Perioperative cardiac morbidity and mortality are a major health care challenge with important individual as well as economic aspects. Up to 30% of all perioperative complications and up to 50% of all postoperative deaths are related to cardiac causes. Perioperative myocardial ischemia, which occurs in more than 40% of patients with or at risk for coronary artery disease and undergoing noncardiac surgery, represents a dynamic predictor of postoperative cardiac complications. Long-duration myocardial ischemia and ischemic episodes associated with myocardial cell damage are particularly of prognostic relevance. In patients suffering from this type of ischemia, the incidence of adverse cardiac outcome is increased up to 20-fold. Reducing the incidence of perioperative myocardial ischemia is associated with a decrease in adverse cardiac outcome. Important issues related to perioperative myocardial ischemia are hematocrit level, body temperature, and hemodynamic variables. In contrast, the choice of anesthetic agents and techniques appears to be less important. Perioperative administration of anti-ischemic drugs in patients at risk, however, leads to a further decrease in the incidence of myocardial ischemia and to an improvement in patient outcome. Recent studies suggest that alpha 2-agonists and particularly beta-adrenoreceptor blocking agents are effective anti-ischemic drugs in the perioperative setting. Perioperative administration of beta-adrenoreceptor blocking agents in coronary risk patients undergoing noncardiac surgery is associated with a reduced rate of postoperative cardiac complications and an improvement in long-term outcome. This is particularly relevant in high risk patients with preoperative stress-induced ischemic episodes. In clinical practice, therefore, chronically administered anti-ischemic drugs should also be administered on the day of surgery and during the postoperative period. In untreated patients with or at risk for coronary artery disease and who have to undergo urgent surgical procedures without the opportunity of preoperative anti-ischemic intervention, perioperative administration of beta-adrenoreceptor blocking agents is mandatory.     

Therapy insight: prophylaxis, monitoring and treatment of perioperative myocardial ischemia with emphasis on urological surgery

Unrecognized or silent perioperative myocardial ischemia is common in patients who undergo high-risk surgery, including cystectomy, and could predict cardiac morbidity and mortality in postoperative patients. This disorder is not merely a marker of extensive coronary disease but has a close association with perioperative myocardial infarction (PMI). In a review of published data, including meta-analyses, in the context of high-risk urological surgery, up to 50% of PMIs were found to go unrecognized if only clinical signs and symptoms are considered. Prevention and treatment of these previously unrecognized cardiac events might significantly reduce long-term morbidity and mortality. The emergence of reliable markers of PMI, such as increased levels of troponin I, could help in the detection of events that would have otherwise remained unnoticed. In this Review we examine the effect of these developments in the context of high-risk urological surgery. Changes to preoperative assessment, perioperative management, and prophylaxis of PMI are critically assessed. We performed a prospective audit using postoperative troponin I levels to assess the rate of silent perioperative myocardial ischemia and infarction. An increasingly proactive attitude towards perioperative monitoring for myocardial ischemia and infarction has evolved, and postoperative serial screening with troponin I might be beneficial in high-risk patients undergoing major urological surgery.     

Best evidence in anesthetic practice

Question  

In patients undergoing major non-cardiac surgery, what is the efficacy and harm of pharmacological interventions in preventing perioperative myocardial ischemia, nonfatal myocardial infarction (MI), or cardiac mortality?     

Perioperative cardiovascular complications in patients with hypertrophic cardiomyopathy

BACKGROUND: The aim of this study was to examine the incidence of cardiac complications in patients with hypertrophic cardiomyopathy (HCM) during noncardiac surgery. METHODS: A retrospective study was made for surgical patients in the period of 1989-2000 at Kitasato University Hospital. RESULTS: Thirty out of 66000 patients were preoperatively diagnosed as HCM. Sixty percent of the HCM patients had one or more perioperative cardiovascular complications. There were perioperative congestive heart failure in 3 patients (10%), and myocardial ischemia in 4 patients (13%). However, there were no myocardial infarction, no life-threatening dysarrthythmia and no cardiac death. Factors which appeared to be associated with the perioperative cardiovascular complications were the type of HCM (HOCM), major surgery, general anesthesia and preoperative medication with a beta-blocker or a calcium channel blocker. CONCLUSIONS: It is suggested that patients with HCM undergoing noncardiac surgery have a high incidence of cardiac complications such as congestive heart failure and myocardial ischemia.     

Significance of right bundle branch block in the diagnosis of myocardial ischemia in patients undergoing coronary artery bypass grafting.

BACKGROUND: Perioperative diagnosis of myocardial ischemia following cardiac surgical procedures remains a challenging problem. Particularly, the role of new conduction disturbances as markers of postoperative ischemia is still questionable. The goal of this study was to elucidate the diagnostic significance of new postoperative right bundle branch block (RBBB) for the detection of perioperative myocardial ischemia in patients undergoing elective coronary artery bypass grafting (CABG). METHODS: In 169 consecutive patients, three-channel Holter monitoring and serial assessment of serum enzymes were performed for 48 h, and 12-lead ECG repeated for up to 5 days postoperatively. Postoperative events were classified as either myocardial infarction (MI), transient ischemic events (TIE) or various conduction disturbances. RESULTS: Transient (n=9) or permanent (n=4) RBBB occurred in 13 patients (8%); 14 patients (8%) showed signs of perioperative MI and 18 patients (11%) evidence of TIE. Peak activity of creatine-kinase (CK, 561+/-135 vs. 316+/-19, P<0.05) and CK-MB (22.7+/-3.2 vs. 13.4+/-0.8, P<0.01) were higher in patients with RBBB than in patients without perioperative ischemic events. Peak CK-MB levels were significantly higher in patients with MI as compared to those with RBBB (33.4+/-7.6 vs. 22.7+/-3.2, P<0. 05). Patients with TIE had similar perioperative enzyme levels as patients with no events. CONCLUSION: It is concluded that the combined assessment of repeated 12-lead ECG, continuous Holter monitoring and enzyme analysis allows a reliable diagnosis of perioperative myocardial ischemia and conduction disturbances. The occurrence of new RBBB following elective CABG is indicative of perioperative myocardial necrosis and thus serves as a valuable tool for the diagnosis of new, perioperative ischemic events.     

Silent myocardial ischemia in patients undergoing peripheral vascular surgery: incidence and association with perioperative cardiac morbidity and mortality

Atherosclerosis is a systemic disorder and coronary artery disease is highly prevalent in patients treated for lower-extremity obstructive vascular disease. Myocardial ischemia and infarction represent the most frequent and most clinically important complications of surgical procedures for lower-extremity revascularization. Despite attempts in several areas, no practical, sensitive, and specific method for identifying patients at highest risk for myocardial events postoperatively has been found before now. This study reports observations on a consecutive series of 50 patients who underwent continuous perioperative electrocardiographic monitoring with a microprocessor-based electrocardiographic ischemia monitor. Thirty-eight percent of the patients were found to have episodes of ischemia; most of these episodes were painless and would not otherwise have been recognized. Ischemia was most prominent in the postoperative rather than the preoperative or intraoperative phases. Tachycardia was often associated with ischemia. Significantly more cardiac-related morbidity and deaths occurred in patients who were documented to have silent myocardial ischemia. In fact, no cardiac events occurred in the 31 patients without ischemia (p less than 0.02). This type of ischemia monitoring represents a potential method for segregating patients at high risk for cardiac-related morbidity and death during lower-extremity revascularization.     

Effect of clonidine on cardiovascular morbidity and mortality after noncardiac surgery

BACKGROUND: Perioperative myocardial ischemia occurs in 20-40% of patients at risk for cardiac morbidity and is associated with a ninefold increase in risk of cardiac morbidity. METHODS: In a prospective, double-blinded, clinical trial, we studied 190 patients with or at risk for coronary artery disease in two study groups with a 2:1 ratio (clonidine, n = 125 vs. placebo, n = 65) to test the hypothesis that prophylactic clonidine reduces the incidence of perioperative myocardial ischemia and postoperative death in patients undergoing noncardiac surgery. Clonidine (0.2 mg orally as well as a patch) or placebo (tablet and patch) was administered the night before surgery, and clonidine (0.2 mg orally) or placebo (tablet) was administered on the morning of surgery. The patch or placebo remained on the patient for 4 days and was then removed. RESULTS: The incidence of perioperative myocardial ischemia was significantly reduced with clonidine (intraoperative and postoperative, 18 of 125, 14% vs. placebo, 20 of 65, 31%; P = 0.01). Prophylactic clonidine administration had minimal hemodynamic effects. Clonidine reduced the incidence of postoperative mortality for up to 2 yr (clonidine, 19 of 125 [15%] vs. placebo, 19 of 65 [29%]; relative risk = 0.43 [confidence interval, 0.21-0.89]; P = 0.035). CONCLUSIONS: Perioperative administration of clonidine for 4 days to patients at risk for coronary artery disease significantly reduces the incidence of perioperative myocardial ischemia and postoperative death.     

Initial Report of the Working Group on Frontiers in Perioperative Myocardial Management

An informal working group on perioperative myocardial management has been formed, which is predominantly composed of cardiac surgeons and anesthesiologists. The first meeting was introduced with a reminder that perioperative ischemia is still an important component of cardiac operations when sophisticated tools are used to monitor its presence and physiological effects. Moreover, perioperative ischemia is associated with adverse outcomes in many instances. The discussion touched upon generalized problems that included leukocyte tivation, oxidant stress, warm cardioplegia, warm heart surgery, echocardiographic assessment of coronary blood flow, vascular endothelial responses to cardiac operations and cardiopulmonary bypass, myocardial stunning, substrate enhancement of cardioplegic solutions, tools for assessing perioperative ventricular performance, and detection of perioperative myocardial ischemia. It was agreed that a highly focused program on the agenda of myocardial stunning would be the topic for the next meeting of the group, with the results to be published in a future issue.     

Volatile anesthetics and cardiac function

All volatile anesthetics have been shown to induce a dose-dependent decrease in myocardial contractility and cardiac loading conditions. These depressant effects decrease myocardial oxygen demand and may, therefore, have a beneficial role on the myocardial oxygen balance during myocardial ischemia. Recently, experimental evidence has clearly demonstrated that in addition to these indirect protective effects, volatile anesthetic agents also have direct protective properties against reversible and irreversible ischemic myocardial damage. These properties have not only been related to a direct preconditioning effect but also to an effect on the extent of reperfusion injury. The implementation of these properties during clinical anesthesia can provide an additional tool in the treatment or prevention, or both, of ischemic cardiac dysfunction in the perioperative period. In the clinical practice, these effects should be associated with improved cardiac function, finally resulting in a better outcome in patients with coronary artery disease. The potential application of these protective properties of volatile anesthetic agents in clinical practice is the subject of ongoing research. This review summarizes the current knowledge on this subject.     

An assessment of the positive predictive value and cost-effectiveness of dipyridamole myocardial scintigraphy in patients undergoing vascular surgery

Purpose: The approach to cardiac risk stratification of patients undergoing vascular surgery continues to be controversial. The success of algorithms that use clinical risk factors to determine cardiac risk have been inconsistent. Dipyridamole myocardial scintigraphy (DMS) has been accepted as a sensitive, noninvasive approach to risk stratification with excellent negative predictive value. Low positive predictive value (PPV) of abnormal DMS scans is a shortcoming that contributes to extensive preoperative cardiac evaluation and intervention with associated morbidity, mortality, and cost in most patients who undergo uncomplicated vascular procedures, regardless of DMS results.Methods: Over 6 years, 237 patients underwent DMS before surgical management of infrarenal aortic aneurysm, aortoiliac, or infrainguinal occlusive disease. The value of multiple clinical factors and DMS were assessed retrospectively for the prediction of perioperative myocardial infarction (MI), heart-related death, or preoperative selection for myocardial revascularization. Only congestive heart failure and two or more reversible defects on DMS were statistically significant on logistic regression analysis.Results: The PPV of DMS was 19% for all patients with reversible defects, 12% for patients with one reversible defect, and 36.7% for patients with two or more reversible defects. The rates of cardiac death and MI were 1.3% and 5.9%, respectively. Perioperative echocardiography revealed unchanged postinfarction ejection fraction in most patients who experienced MI. Cost-effectiveness of DMS screening was evaluated.Conclusions: The costs per MI and cardiac death averted suggest a decline in cost-effectiveness of screening with DMS over time, assuming improving cardioprotective strategies of patient care. Clinical risk factors were minimally useful in the prediction of perioperative MI, heart-related death, or need for myocardial revascularization. The PPV of DMS is low, and the majority of MIs may be clinically insignificant. The cost-effectiveness of cardiac screening with DMS may not be justifiable given current trends of health care reform. (J VASC SURG 1994;19:112-24.)     

Cardioprotection in anesthesia

Ischemic heart disease is the major cause of morbidity and mortality in the Western world. With the advancing age of the surgical population, anesthesiologists increasingly have to treat patients with known or suspected ischemic heart disease in the perioperative period. Over the years various strategies have been developed to prevent myocardial ischemia in the perioperative period and/or to minimize the extent of myocardial damage after perioperative ischemia. This review summarizes the current knowledge on the subject and focuses on the more recent data concerning perioperative cardioprotection by anesthetic agents.     

Clinical Predictors of Intraoperative Myocardial Ischemia in Patients with Coronary Artery Disease Undergoing Non-Cardiac Surgery

In order to detect the incidence of myocardial ischemia during the perioperative period and to determine during which situation it ocurred, continuous monitoring of the electrocardiogram by the Holter method was used in 51 patients with coronary artery disease who were undergoing a vascular surgical procedure. Clinical parameters measured preoperatively were evaluated as predictors of the occurrence of myocardial ischemia during the perioperative period. Twenty of 51 patients demonstrated 36 episodes of myocardial ischemia, which started in 11 cases during induction. Fourteen of 16 patients with disabling angina pectoris (Class III and IV) developed myocardial ischemia, whereas only six patients out of 35 with Class II or less or no angina experienced preoperative ischemic episodes ( P < 0.001). All the patients without or with only mild angina who experienced perioperative ischemia showed ST-T abnormalities at the preoperative resting electrocardiogram. Our data suggest that the risk of intraoperative myocardial ischemia can be predicted during the preoperative period by the degree of disability exhibited by patients with coronary artery disease.     

QTc dispersion is prolonged in patients with early postoperative adverse cardiovascular events and those with silent myocardial ischemia

OBJECTIVE: To determine if increased QT interval dispersion (corrected and not corrected for heart rate) is associated with perioperative silent myocardial ischemia or postoperative adverse cardiovascular events. DESIGN: Blinded retrospective observational study. SETTING: University hospital. PARTICIPANTS: One hundred eighty-one perioperative patients receiving general anesthesia for elective major vascular or orthopedic surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: QT dispersion, corrected and uncorrected for heart rate, was prolonged in patients suffering significant myocardial ischemia up to 48 hours assessed by Holter ECG monitoring, for early cardiac morbidity and all early cardiac events (including mortality) up to 1 month postoperatively. There were no significant changes in patients showing early cardiovascular mortality or late cardiac morbidity or mortality between 1 and 12 months postoperatively. Morbidity and mortality were determined from clinical notes, laboratory investigations, and autopsy when available. QT dispersion performed poorly as a screening test to identify those who subsequently developed early adverse cardiovascular outcomes. CONCLUSIONS: QT dispersion is prolonged in those at risk of early adverse cardiovascular events but is a poor screening tool.     

围术期心肌梗塞的诊疗进展

迄今越来越多的存在心脏高危疾病的患者进行各种手术治疗．由此产生的围术期心肌梗塞（PMI）日益受到关注。依据导致PMI的病理生理机制可以将PMI分为两种类型;1型为围术期出现急性冠脉综合征．2型则是由于在稳定的冠脉病变的基础上（在围手术期间）出现过长时间供氧与耗氧的不平衡而发生的。在围术期对心肌缺血细致严密的监护、在保证血压的基础上严格的控制心率,降低心输出置及预防心脏失代偿的发生,对PMI的预防具有积极的意义。而冠脉血管的外科干预治疗并不是推荐的预防PMI的治疗手段,常规的抗血栓治疗可能加重围术期出血。     

Beta-adrenergic blocking drugs in the perioperative period

During the last years increasing evidence has indicated that patients at risk for coronary artery disease may benefit from beta-adrenergic blocking therapy in the perioperative setting. It has been demonstrated that even a relatively brief treatment with beta-adrenergic blocking drugs decreases the incidence of perioperative myocardial ischemia. Even more important is the observation that this reduction in perioperative ischemic events ultimately results in a decrease in long term cardiac morbidity and mortality. Despite overwhelming evidence on the beneficial effects of beta-adrenergic blocking in patients with coronary artery disease, many clinicians still feel some reluctance to use this type of drugs in the perioperative period. We organized a meeting to search for the major objectives that keep anesthetists from implementing prophylactic beta blocking therapy in their daily clinical practice. In this brief review we summarize the results of this meeting and discuss the current knowledge on this subject.     

Effect of Clonidine on Cardiovascular Morbidity and Mortality after Noncardiac Surgery

Background: Perioperative myocardial ischemia occurs in 20-40% of patients at risk for cardiac morbidity and is associated with a ninefold increase in risk of cardiac morbidity.

Methods: In a prospective, double-blinded, clinical trial, we studied 190 patients with or at risk for coronary artery disease in two study groups with a 2:1 ratio (clonidine, n = 125 vs. placebo, n = 65) to test the hypothesis that prophylactic clonidine reduces the incidence of perioperative myocardial ischemia and postoperative death in patients undergoing noncardiac surgery. Clonidine (0.2 mg orally as well as a patch) or placebo (tablet and patch) was administered the night before surgery, and clonidine (0.2 mg orally) or placebo (tablet) was administered on the morning of surgery. The patch or placebo remained on the patient for 4 days and was then removed.

Results: The incidence of perioperative myocardial ischemia was significantly reduced with clonidine (intraoperative and postoperative, 18 of 125, 14% vs. placebo, 20 of 65, 31%; P = 0.01). Prophylactic clonidine administration had minimal hemodynamic effects. Clonidine reduced the incidence of postoperative mortality for up to 2 yr (clonidine, 19 of 125 [15%] vs. placebo, 19 of 65 [29%]; relative risk = 0.43 [confidence interval, 0.21-0.89]; P = 0.035).     

Postoperative prophylactic administration of beta-adrenergic blockers in patients at risk for myocardial ischemia

Perioperative myocardial ischemia (MI) is associated with postoperative cardiac morbidity. Postoperative sympatholysis may reduce the incidence of MI. This study evaluated such a reduction postoperatively with the administration of prophylactic beta-blockers in patients undergoing elective total knee arthroplasty with epidural anesthesia and postoperative epidural analgesia. One hundred seven patients were preoperatively randomized into two groups, control and beta-blockers, who received postoperative esmolol infusions on the day of surgery and metoprolol for the next 48 h to maintain a heart rate less than 80 bpm. Patients were followed for ST segment depression by using a Holter monitor and adverse cardiac outcomes. Postoperative electrocardiographic ischemia was significantly more prevalent in the control group compared with the beta-blocker group during esmolol blockade (0 of 52 vs 4 of 55; P = 0.04) and tended to be more common in the control group the next two days (8 of 55 vs 3 of 52; P = 0.135). In addition, the number of ischemic events (control, 50; beta-blockers, 16) and total ischemic time (control, 709 min; beta-blocker, 236 min) were also significantly different from the control group. Myocardial infarctions and cardiac events were more common in the control group, but these differences were not significant. Our results suggest that the use of prophylactic beta-blocker therapy may reduce the incidence of postoperative MI. Implications: Prophylactic beta adrenergic blockade administered after elective total knee arthroplasty was associated with a reduced prevalence and duration of postoperative myocardial ischemia detected with Holter monitoring.     

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 ischemia in patients undergoing elective hip arthroplasty during lumbar regional anesthesia.

Perioperative myocardial ischemia predicts unfavorable outcomes and occurs in as many as 41% of patients with coronary artery disease or cardiac risk factors undergoing noncardiac surgery. To determine the prevalence of myocardial ischemia, we studied 52 consecutive unselected patients undergoing elective hip arthroplasty during lumbar regional anesthesia. Patients were continuously monitored for 6 days using a three-channel Holter monitor. Ninety-nine episodes of myocardial ischemia occurred in 16 patients (31%), six of whom were considered preoperatively to be at low risk for coronary artery disease. Forty-four percent of the ischemic episodes were preceded or accompanied by a heart rate greater than or equal to 100/min and 56% by a heart rate greater than or equal to 90 beats/min. Ninety-six percent of the ischemic episodes were clinically silent, and 82% were not related to patient care events. Thirteen episodes of myocardial ischemia occurred preoperatively, 1 intraoperatively, and 85 postoperatively. The incidence of postoperative ischemic episodes showed a circadian variation: 44% occurred between 6 AM and noon, 33% between noon and 6 PM, 17% between 6 PM and midnight, and 6% between midnight and 6 AM. Six adverse cardiac events occurred during hospitalization (three of the six among patients with perioperative ischemia) and an additional four events during a follow-up period of 12 months (all four events occurred among patients with perioperative ischemia). Patients with perioperative myocardial ischemia had a relative risk of 2.6 (95% confidence interval 1.3-5.2) to develop an adverse cardiac event postoperatively.