Myocardial infarction after vascular surgery: the role of prolonged stress-induced, ST depression-type ischemia

Intense cardiac troponin surveillance for long-term benefits is cost-effective in patients undergoing open abdominal aortic surgery: a decision analysis model

BACKGROUND

Strategies to limit adverse cardiac events after vascular surgery continue to evolve. Early recognition and treatment of myocardial ischemia may be a key to improving postoperative survival rates. Cardiac troponin I (cTnI) screening is an effective means of surveillance for postoperative myocardial ischemic injury and has long-term prognostic value.

METHODS

We designed a Markov-based decision analysis model to determine the cost-effectiveness of routine surveillance with cTnI on postoperative Days 0, 1, 2, and 3, with an aim to institute tight heart rate control (60-65 bpm) with close monitoring and coronary care in the intensive care unit for 5 days in patients with cTnI >1.5 ng/mL. The key input variables obtained from published literature were as follows: probability of myocardial infarction, 0.049; cost of cTnI surveillance, $357; cost and efficacy of interventions, $13,145 and 0.55, respectively. The time horizon was lifetime and the target population being individuals aged 65 yr (median) undergoing elective open abdominal aortic surgery. The perspective for analysis was third-party payer.

RESULTS

The incremental cost-effectiveness ratio for cTnI surveillance was $12,641 per quality-adjusted life year compared with standard care without cTnI surveillance. During one-way sensitivity analysis, probability of myocardial infarction and efficacy of interventions were found to influence the cost-effectiveness. Multivariate sensitivity analysis with second-order Monte Carlo simulation revealed that cTnI surveillance was favored in 90.75% of simulations at a commonly used threshold of $50,000 per quality-adjusted life year.

CONCLUSIONS

In patients presenting for elective open abdominal aortic surgery, intensive surveillance with cTnI and early institution of aggressive beta-blockade is cost-effective.

How to prevent perioperative myocardial injury: the conundrum continues

BACKGROUND

Perioperative myocardial injury (PMI) remains a major cause of perioperative morbidity and mortality but clinical strategies to prevent PMI are still uncertain.

METHODS AND RESULTS

We comprehensively searched PubMed for major research articles concerning clinical strategies to prevent PMI. The key findings are as follows: (1) the American College of Cardiology/American Heart Association guideline update for perioperative cardiovascular evaluation for noncardiac surgery is very useful to stratify cardiac risk preoperatively; (2) cardiac troponin has emerged as a biomarker to diagnose postoperative PMI and to predict clinical outcomes; (3) coronary revascularization before noncardiac surgery probably would provide cardiac protection in select patients, especially in patients with high-risk coronary artery disease; (4) elective noncardiac surgery should be postponed in patients who received coronary stenting recently because of high incidence of serious cardiac complications (minimum 6-8 weeks for bare metal stents and 6-12 months for drug-eluting stents); and (5) beta-blockers and statins are very promising drugs and probably would prevent PMI in a select patient population, especially in patients with intermediate risk and stable coronary artery disease.

CONCLUSIONS

Further studies, especially randomized clinical trials and mechanistic investigation are needed to find the best and effective clinical strategies to prevent/reduce PMI.

Clinical value of multidetector CT coronary angiography as a preoperative screening test before non-coronary cardiac surgery

OBJECTIVE

Myocardial scintigraphy and/or conventional angiography (CA) are often performed before cardiac surgery in an attempt to identify unsuspected coronary artery disease which might result in significant cardiac morbidity and mortality. Multidetector CT coronary angiography (MDCTCA) has a recognised high negative predictive value and may provide a non-invasive alternative in this subset of patients. The aim of this study was to evaluate the clinical value of MDCTCA as a preoperative screening test in candidates for non-coronary cardiac surgery.

METHODS

132 patients underwent MDCTCA (Somatom Sensation 16 Cardiac, Siemens) in the assessment of the cardiac risk profile before surgery. Coronary arteries were screened for > or = 50% stenosis. Patients without significant stenosis (Group 1) underwent surgery without any adjunctive screening tests while all patients with coronary lesions > or = 50% at MDCTCA (Group 2) underwent CA.

RESULTS

16 patients (12.1%) were excluded due to poor image quality. 72 patients without significant coronary stenosis at MDCTCA were submitted to surgery. 30 out of 36 patients with significant (> or = 50%) coronary stenosis at MDCTCA and CA underwent adjunctive bypass surgery or coronary angioplasty. In 8 patients, MDCTCA overestimated the severity of the coronary lesions (> 50% MDCTCA, < 50% CA). No severe cardiovascular perioperative events such as myocardial ischaemia, myocardial infarction or cardiac failure occurred in any patient in Group 1.

CONCLUSIONS

MDCTCA seems to be effective as a preoperative screening test prior to non-coronary cardiac surgery. In this era of cost containment and optimal care of patients, MDCTCA is able to provide coronary vessel and ventricular function evaluation and may become the method of choice for the assessment of a cardiovascular risk profile prior to major surgery.

Predictors of Electrocardiographic Change, Cardiac Troponin Elevation, and Survival after Major Vascular Surgery: A Community Hospital Experience

Cardiovascular disease is the leading cause of perioperative morbidity and mortality after vascular surgery. The purpose of this study was to identify risk factors for myocardial ischemia after vascular surgery and to investigate a potential association of ischemia with mortality in a community hospital setting. A retrospective review was conducted after 190 major vascular procedures. Electrocardiogram (ECG) results and troponin I levels were obtained serially during the first 24 postoperative hours. Outcomes analyzed were ischemic ECG changes, troponin I level more than 2 ng/mL, 6-month mortality, and overall survival. The authors investigated any association of these outcomes with each other and the type of operation, history of coronary artery disease, diabetes, recent coronary intervention, age older than 70 years, or postoperative symptoms. Twenty-seven (14%) patients experienced ischemic ECG changes. Twenty-one (11%) patients experienced troponin I elevation. Univariate analysis revealed a history of coronary artery disease, diabetes, concerning symptoms, and troponin elevation to be predictive of ECG change ( P < 0.05). ECG change and symptoms were predictive of troponin elevation ( P < 0.01). Cox multivariate analysis revealed only infrainguinal bypass to predict 6-month mortality (odds ratio = 2.92, P = 0.02). Diabetes was the sole predictor of overall mortality (odds ratio = 1.94, P = 0.001). Nonsustained ischemic postoperative ECG changes during the first 24 postoperative hours do not independently influence 6-month or overall mortality after major vascular surgery. Postoperative troponin elevation likely conveys a mortality risk in the subsequent 6 months. In the community hospital setting, midterm survival rates after vascular surgery equivalent to those in higher volume centers can be achieved. Patients undergoing infrainguinal bypass and diabetics continue to be the most moribund vasculopaths.

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.

Ischemic heart disease

Because of changing demographics, increasing numbers of patients with IHD are presenting for noncardiac surgery, and the risks of perioperative morbidity and mortality are significant. The Lee Cardiac Risk Index is applicable in defining perioperative cardiac risk: however, ACC/AHA guidelines may not be applicable comprehensively. The role of biomarkers in risk stratification still needs to be defined. Structured management protocols that help assess, diagnose, and treat patients with IHD preoperatively are likely to help decrease postoperative morbidity and mortality, but clearly are not applicable to all patients. Augmented hemodynamic control with beta-blockers or alpha-2 agonists and modulating inflammation by statins can play an important role in improving outcomes in many patients with IHD; preoperative coronary revascularization may be of limited value. Intraoperative anesthetic management that minimizes hemodynamic perturbations is important; however, the choice of a particular technique typically is not critical. Of critical importance is the postoperative management of the patient. Postoperative myocardial injury should be identified, evaluated, and managed aggressively. Secondary stresses such as sepsis, extubation, and anemia, which can increase demand on the heart, should be treated or minimized. Clearly, optimal care of the patient with IHD entails closely coordinated assessment and management throughout the preoperative, intraoperative, and postoperative phases, if one is to optimize short- and long-term outcomes.

[Infarction in the per-operative period: check-up, results, treatment, surveillance]

Peroperative infarction (POI) is a frequent and serious event, which is associated with an increase in morbidity and mortality; the risk is aggravated to varying degrees by the techniques of anaesthesia and surgery used. The preoperative evaluation of risk, which combines clinical and paraclinical criteria is described in the algorithm of the new AHA/ACC guidelines. In order to avert these ischemic episodes, beta-blockers must be continued or introduced during vascular surgery. In other types of surgery, they must be considered. It is difficult to diagnose MI in a per-operative context. The electrocardiogram print out and troponin kinetics will identify patients in the postoperative phase that should be oriented towards cardiovascular evaluation and therapy.

Perioperative cardiac risk: pathophysiology, assessment and management

Cardiac complications are the leading cause of perioperative morbidity and mortality following noncardiac surgery. The annual cost of perioperative cardiovascular events exceeds 20 billion US dollars. A strategic preoperative evaluation holds the potential to reduce perioperative cardiac events and healthcare costs; however, our current understanding of the pathophysiological basis of postoperative acute coronary syndromes is limited. Although significant advances continue to facilitate early and reliable noninvasive detection of high-risk coronary anatomy, the most appropriate interventions remain unclear. Pharmacotherapy, revascularization, safer anesthesia and early detection of perioperative heart failure may all reduce perioperative morbidity and mortality, although the evidence base is incomplete and controversial. A close working relationship between the primary care physician, cardiologist, surgeon and anesthesiologist will facilitate rational, tailored and optimized management decisions that constitute our best opportunity to reduce perioperative cardiovascular risk.

Vascular surgery critical care: perioperative cardiac optimization to improve survival

OBJECTIVE

To review the literature on perioperative cardiac management of patients who are scheduled to undergo vascular surgery.

DATA SOURCE

MEDLINE- and PubMed-based review of literature published from 1965 to 2005.

CONCLUSIONS

Perioperative cardiac events (myocardial infarction, heart failure) remain the leading cause of morbidity and mortality in vascular surgery patients. Existing guidelines allow physicians to cost-effectively streamline preoperative cardiac risk assessment and stratification. Perioperative optimization of volume status and cardiac function and the routine use of perioperative beta-blockers can significantly improve outcomes after major vascular surgery. Perioperative addition of statins to beta-blockers in high-risk patients undergoing vascular surgery merits further evaluation. Preoperative coronary revascularization should be restricted to patients with unstable cardiac symptoms.

Management of Perioperative Myocardial Infarction in Noncardiac Surgical Patients

Perioperative myocardial infarction (PMI) is a major cause of morbidity and mortality in patients undergoing noncardiac surgery. The incidence of PMI varies depending on the method used for diagnosis and is likely to increase as the population ages. Studies have examined different methods for prevention of myocardial infarction (MI), including the use of perioperative beta-blockers, alpha(2)-agonists, and statin therapy. However, few studies have focused on the treatment of PMI. Current therapy for acute MI generally involves anticoagulation and antiplatelet therapy, raising the potential for surgical site hemorrhage in this population. This article reviews the possible mechanisms, diagnosis, and treatment options for MI in the surgical setting. We also suggest algorithms for treatment.

Early increases in cardiac troponin levels after major vascular surgery is associated with an increased frequency of delayed cardiac complications

OBJECTIVE

To evaluate changes in cardiac troponin-I levels after major vascular surgery and their association with early and late postoperative cardiac complications.

DESIGN

Prospective, observational investigation.

SETTING

University teaching hospital.

PATIENTS

75 consecutive patients undergoing major vascular surgery.

INTERVENTIONS

All patients received a standard sevoflurane-fentanyl anesthesia during the procedure. Blood levels of creatine kinase with MB subtype and cardiac troponin-I were assessed before surgery and then everyday for the first 3 days after surgery. At the same time, 12-lead electrocardiography was also performed, and occurrence of any cardiac adverse event was recorded. Patients were then followed up for 1 month after surgery.

MEASUREMENT AND MAIN RESULTS

Troponin-I levels increased in 25 patients (33%) during the first 3 days after surgery; 9 of these patients (12%) had myocardial infarction. At univariate analysis, uncontrolled hypertension was the only risk factor for perioperative infarction (odds ratio, 16; (95% confidence interval, 3-74); however, multivariate logistic regression analysis failed to show statistically significant associations. Increases in troponin-I had a 100% sensitivity and 75% specificity in detecting myocardial ischemia with a 36% positive and 100% negative predictive values. Severe cardiac complication 1 month after surgery was reported in 5 patients (6.6%). The increase of cardiac troponin-I levels during the first 3 postoperative days was associated with an increased frequency of major cardiac complication at 1-month follow-up (P = 0.003), with a 100% sensitivity, 71% specificity, and 100% negative predictive value.

CONCLUSIONS

Myocardial infarction after major noncardiac vascular surgery occurs in up to 12% of cases. Perioperative monitoring of troponin-I plasma levels may help to identify patients at increased risk for cardiac morbidity not only early after surgery but also during the first postoperative month.

Beta-blockade in the perioperative period: where do we stand after all the trials?

Perioperative myocardial infarction following noncardiac surgery is a complex process with a variety of proposed etiologic factors. Perioperative beta-blockade has been reported to reduce perioperative myocardial infarction and cardiac death, with possible direct effects on longer-term outcome, particularly after vascular surgery. Despite two high-profile studies that have pushed this topic into the mainstream of medicine, the number of patients studied and outcomes observed remains limited, especially for a therapy recommended for widespread adoption in millions of patients globally. Observational analyses, small meta-analyses, and newer randomized trial data (primarily in abstract format) suggest the therapy is of benefit in high-risk patients, whereas in patients at intermediate or low risk, it is either mildly efficacious or neutral in effect. Adverse effects appear to be limited to the expected primary hemodynamic side effects of bradycardia and hypotension, although a suggestion of increased mortality has been reported in one observational analysis in the lowest-risk group. beta-Blockade may be associated with reduction in length of stay and reduced analgesic requirements, although these effects remain controversial. A single mega-trial being conducted outside of the United States with a target goal of 10,000 patients is ongoing and promises to provide definitive data within the next few years. Ongoing research into various etiologies of perioperative myocardial infarction and other medications with potential efficacy in this setting, including the important antiplatelet agents, must also be considered in developing recommendations for widespread adoption of perioperative beta-blockade.

[Preoperative cardiac assessment using dobutamine stress echocardiography]

Postoperative myocardial ischaemia is the leading cause of life expectancy impairment after high cardiac risk surgical procedures. Preoperative identification of patients at high risk for such complication helps reducing its postoperative incidence through therapeutic adjustments. The former relies upon preoperative selection of patients who are candidates for cardiac testing using dobutamine stress echocardiography, according to ACC/AHA guidelines. This exam evaluates echographic myocardial response to a pharmacological stress induced by dobutamine infusion. Its aim is to reproduce part of the stress the myocardium will undergo during surgical procedure. A stress induced myocardial ischaemia suggests such a complication could occur postoperatively. A positive dobutamine stress echocardiography justifies to prescribe preoperative anti-ischaemic treatment in order to reduce the cardiac risk of the further surgical procedure. Moreover, it justifies clear definition of perioperative haemodynamic objectives. Whatever the result of the dobutamine stress echocardiography, cardiac ischaemia should be monitored up to the third postoperative day on the basis of a daily 12-lead electrocardiogram recording and daily plasmatic troponin Ic measurement.

Anesthésie et réanimation pour chirurgie réglée de l'anévrisme de l'aorte abdominale

OBJECTIVES

Patient scheduled for infrarenal abdominal aortic aneurysm surgery carries a high risk of cardiac or respiratory comorbidity. To outline the perioperative management for these patients.

METHODS

Review of the literature using MesH Terms "abdominal aortic aneurysm", "anesthesia", "analgesia" "critical care" and/or "surgery" in Medline database.

RESULTS

Cardiac preoperative evaluation and management have recently been reviewed. Intermediate and high-risk patients should undergo non-invasive cardiac testing to decide between a preoperative medical strategy (using betablocker+/-statin and aspirin) and an interventional strategy (coronary angioplasty or cardiac surgery). Perioperative myocardial ischaemia should also be investigated by clinical, electrocardiographic and biologic monitoring such as plasmatic troponin Ic dosage. Specific score could also assess the respiratory failure risk preoperatively. Epidural analgesia decreases this risk. There is no evidence that a pharmacological treatment decreases the incidence of acute renal failure after aortic surgery. Endovascular repair is actually recommended for older, higher-risk patients or patients with a hostile abdomen or other technical factors that may complicate standard open repair.

Preoperative evaluation and treatment of stable CAD in patients scheduled for major elective vascular surgery

One of the most controversial topics in clinical cardiology is the extent of preoperative studies that is required among patients scheduled for major elective noncardiac operations. Patients in need of an elective operation for either an expanding aortic aneurysm or lower limb ischemia have the highest risk of postoperative cardiac complications because of the high prevalence of coronary artery disease and the hemodynamic stresses associated with the vascular procedures. The decision to perform preoperative coronary angiography should be reserved for only those patients who are deemed clinically unstable or are functionally limited by cardiac symptoms. Among patients with minimal symptoms, preoperative coronary artery revascularization with either coronary artery bypass graft surgery or percutaneous coronary interventions delays the needed operation and does not improve short-term outcomes or long-term survival.

The pharmacoeconomics of peri-operative beta-blocker therapy

It is widely recommended that beta-blockade be used peri-operatively as it may reduce the incidence of postoperative cardiovascular complications including death. However, there are few data concerning the cost-effectiveness of such strategies. We have analysed the pharmacoeconomics of acute beta-blockade using data from eight prospective peri-operative studies in which patients underwent elective non-cardiac surgery, and in which the incidence of adverse side-effects of treatment, as well as clinical outcomes, have been reported. The costs of treatment were based on the NHS reference costs for 2004. From these data, the number-needed-to-treat (NNT) to prevent a major cardiovascular complication (including cardiovascular death) in high-risk patients was 18.5. This is comparable to the NNT for peri-operative statin therapy. The incremental cost of peri-operative beta-blockade (costs of drug acquisition and of treating associated adverse drug events) was 67.80 pounds sterling per patient. This results in a total cost of 1254.30 pounds sterling per peri-operative cardiovascular complication prevented. However, there is evidence that in patients at lower cardiovascular risk, beta-blockers may be potentially harmful, since their adverse effects (hypotension, bradycardia) may outweigh their potential cardioprotective effects.

Perioperative myocardial infarction in non-cardiac surgery. Pathophysiology and clinical implications

Advances in surgical and anaesthetic techniques and an aging patient population have resulted in more complex procedures being performed in greater numbers of aged subjects and in patients with a high likelihood of significant cardiovascular disease. Nearly one fourth of non-cardiac surgical procedures (major intra-abdominal, thoracic, vascular, and orthopaedic procedures) performed in persons older than 65 years have been found to be associated with significant perioperative cardiovascular morbidity and mortality. During previous years the main attempt was to define strategies to accurately estimate perioperative cardiovascular risk based either on the characteristics of surgery and on patient characteristics. More recently preventive medical strategies have been proposed. Therefore, the physician has to be aware of the key elements useful to calculate the perioperative cardiovascular risk, and of the medical preventive treatment or further interventions to adopt in patients candidate to surgery.

Perioperative cardiac events in patients undergoing noncardiac surgery: a review of the magnitude of the problem, the pathophysiology of the events and methods to estimate and communicate risk

This is the first of 2 articles evaluating cardiac events in patients undergoing noncardiac surgery. In this article, we review the magnitude of the problem, the pathophysiology of these events, approaches to risk assessment and communication of risk. The number of patients undergoing noncardiac surgery worldwide is growing, and annually 500,000 to 900,000 of these patients experience perioperative cardiac death, nonfatal myocardial infarction (MI) or nonfatal cardiac arrest. Although the evidence is limited, a substantial proportion of fatal perioperative MIs may not share the same pathophysiology as nonoperative MIs. A clearer understanding of the pathophysiology is needed to direct future research evaluating prophylactic, acute and long-term interventions. Researchers have developed tools to facilitate the estimation of perioperative cardiac risk. Studies suggest that the Lee index is the most accurate generic perioperative cardiac risk index. The limitations of the studies evaluating the ability of noninvasive cardiac tests to predict perioperative cardiac risk reveals considerable uncertainty as to the role of these popular tests. Similarly, there is uncertainty as to the predictive accuracy of the American College of Cardiology/American Heart Association algorithm for cardiac risk assessment. Patients are likely to benefit from improved estimation and communication of cardiac risk because the majority of noncardiac surgeries are elective and accurate risk estimation is important to allow informed patient and physician decision-making.

Intermittent Cardiac Troponin-I Screening is an Effective Means of Surveillance for a Perioperative Myocardial Infarction

OBJECTIVE

Several studies suggest that cardiac troponin-I (cTn-I) is a more sensitive indicator of cardiac injury compared with other biochemical markers of injury, but the strategy with the highest diagnostic yield (true positive and true negative) for perioperative surveillance is unknown. The authors undertook a prospective evaluation of the perioperative incidence of myocardial infarction (MI) and evaluated surveillance strategies for the diagnosis of MI.

DESIGN

Prospective, cohort study.

SETTING

Two university hospitals.

PARTICIPANTS

Four hundred sixty-seven high-risk patients requiring noncardiac surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The diagnosis of myocardial injury was determined by cardiac protein markers combined with either postoperative changes on 12-lead electrocardiography or 1 of 3 clinical symptoms consistent with MI (chest pain, dyspnea, requirement for hemodynamic support). A receiver operating characteristic curve evaluating troponin in the diagnosis of MI revealed a value of 2.6 ng/mL as having the highest sensitivity and specificity. The sensitivity and specificity of cTn-I value > or =2.6 ng/mL, troponin > or =1.5 ng/mL, total creatine kinase (CK) > or =170 IU/L with MB > or =5%, and CK-MB > or =8 ng/mL were compared. Surveillance strategies were determined on a subset of patients (n = 257). The incidence of MI was 9.0% by cTn-I > or =2.6 ng/mL criteria, 19% by cTn-I > or =1.5 ng/mL, 13% by CK-MB mass, and 2.8% by CK-MB%. The specificity of cTn-I > or =2.6 ng/mL as an indicator of MI was 98%, and its positive predictive value (PPV) was 85%. Cardiac troponin-I > or =2.6 ng/mL had equal specificity but greater PPV than the cTn-I > or =1.5 ng/mL (specificity 98% and PPV 79%). If surveillance of cTn-I > or =2.6 ng/mL was used to detect MI, then the strategy with the highest diagnostic yield was surveillance on postoperative days 1, 2, and 3.

CONCLUSIONS

Perioperative cardiac injury continues to occur frequently after noncardiac surgery, as detected by cTn-I. Serial monitoring of cardiac troponin-I on postoperative days 1, 2, and 3 provides the strategy with the highest diagnostic yield for surveillance of MI.

Perioperative myocardial infarction—aetiology and prevention

Perioperative myocardial infarction (PMI) is one of the most important predictors of short- and long-term morbidity and mortality associated with non-cardiac surgery. Prevention of a PMI is thus a prerequisite for an improvement in overall postoperative outcome. The aetiology of PMI is multifactorial. The perioperative period induces large, unpredictable and unphysiological alterations in coronary plaque morphology, function and progression, and may trigger a mismatch of myocardial oxygen supply and demand. With many diverse factors involved, it is unlikely that one single intervention will successfully improve cardiac outcome following non-cardiac surgery. A multifactorial, step-wise approach is indicated. Based on increasing knowledge of the nature of atherosclerotic coronary artery disease, and in view of the poor positive predictive value of non-invasive cardiac stress tests, and the considerable risk of coronary angiography and coronary revascularization in high-risk patients, the paradigm is shifting from an emphasis on extensive non-invasive preoperative risk stratification to a combination of selective non-invasive testing and aggressive pharmacological perioperative therapy. Perioperative plaque stabilization by pharmacological means may be as important in the prevention of PMI as an increase in myocardial oxygen supply or a reduction in myocardial oxygen demand.

[Preoperative evaluation and perioperative management of patients with increased cardiovascular risk]

Due to the increasing age in western countries, combined with high rates of major surgical interventions in high-risk patients, perioperative reduction of cardiovascular complications becomes increasingly more important for perioperative physicians. After identifying patients with increased perioperative risk, specific interventions need to be considered to reduce their risk for cardiovascular complications, either by perioperative medical therapy or specific treatment options (e.g. coronary intervention). Several trials have demonstrated an effect of perioperative beta-blocker-therapy in reducing cardiovascular complications among high-risk patients. Additionally, several monitoring techniques are effective in detecting cardiovascular complications. Nevertheless, it remains unclear whether they are associated with a measurable improvement of outcome. Based on the ACC/AHA-guidelines, the present review describes a stepwise approach to surgical patients to identify perioperative risks, based on specific patient related risk factors, the kind of surgery and on the specific setting (emergency versus elective surgery). In addition, strategies to reduce perioperative cardiovascular complications are discussed.

Myocardial ischemia, cardiac troponin, and long-term survival of high-cardiac risk critically ill intensive care unit patients*

OBJECTIVES

To determine the incidence and association of myocardial ischemia with troponin elevation and survival in high-cardiac-risk intensive care patients.

DESIGN

Prospective observational study.

SETTING

Intensive care unit of a tertiary hospital.

SUBJECTS

One-hundred one general intensive care unit patients having a history of coronary artery disease or at least two risk factors for coronary artery disease.

INTERVENTIONS

Continuous 12-lead electrocardiographic monitoring with on-line ST-trend analysis, daily cardiac troponin measurements, clinical and physiologic assessment, and up to 2-yr follow-up for survival.

MEASUREMENTS AND MAIN RESULTS

During 8,988 hrs or a mean +/- sd of 95 +/- 85 hrs/patient of continuous 12-lead electrocardiographic monitoring, 21 patients (21%) had ischemic ST-segment changes, characterized in most (19) by ST depression and lasting >60 mins in 15 (71.4%). Of the 38 patients (38%) with troponin elevation, myocardial infarction was clinically suspected in four and myocardial ischemia on continuous 12-lead electrocardiographic monitoring was observed in 14 (36.8%). Fourteen (66.7%) of the patients with ischemic ST changes and 12 (75%) of those with prolonged (>60 mins) ischemia had troponin elevation. The sensitivity, specificity, and positive and negative predictive values of prolonged (>60 mins) ischemia predicting troponin elevation were 31.6%, 95.2%, 80.0%, and 69.8%, respectively. Prolonged (>60 mins) ischemia was significantly associated with troponin elevation by both univariate and multivariate analyses (odds ratio = 9.0; p = .008). Acute Physiology and Chronic Health Evaluation II score, renal failure, and the use of norepinephrine also independently predicted troponin elevation. Troponin but not ischemia predicted increased 1-month, 6-month, and 2-yr mortality (odds ratio = 6.0, 3.2, and 2.99, respectively; p < .001).

CONCLUSIONS

Silent ischemia is strongly associated with troponin elevation in high-cardiac-risk intensive care unit patients, and troponin elevation predicts both early and late mortality.

Preoperative Cardiac Evaluation: Mechanisms, Assessment, and Reduction of Risk

The changing paradigm in cardiovascular disease in which atherosclerotic lesions exist in a spectrum of stable to unstable, the lack of a perfect prediction tool, and the paucity of randomized controlled data on appropriate intervention make protection of cardiac patients undergoing thoracic surgery challenging. Nociception-related sympathetic drive combines with inflammatory stimuli and the cardiodepressant effects of anesthesia to create a window of maximum risk in the early postoperative period (8-24 hours), and although multivariate models have shown that a combination of surgery-specific risk, patient-specific cardiovascular history, and estimated functional capacity best determine the need for further investigation, the optimal choice of investigation is unclear. Exercise or dobutamine stress echocardiography provide the best validated investigations, and in the case of poor images, dobutamine MR imaging is increasingly used. When disease is found, medical and interventional options are available. PCI is often used, but the risk of converting a stable flow-limiting lesion into a less stable non-flow-limiting lesion must be considered, along with a delay for anti-platelet therapy and endothelialization of the stent. Alternatively, medical protection with acute beta-blockade or alpha2-agonists reduces risk (although beta-blockade often is avoided in chronic lung disease, even nonselective agents are safe in patients with non-airways reactive COPD). In addition, it is likely that statin use reduces risk, probably by stabilizing plaques, but patients with cardiac risk are increasingly likely to be taking this medication already. The assessment and management of cardiac risk in the perioperative thoracic surgery patient is challenging. With focused, rational, and individually tailored management; tight monitoring of postoperative pain; and a close working relationship between the surgeon, anesthesiologist, and cardiologist, patient care can be optimized, and risk can be effectively controlled.

Silent myocardial ischemia: Recent developments

Silent myocardial ischemia is now in its fourth decade of recognition as a clinical syndrome within the spectrum of coronary artery disease. Prior decades have seen important research into the pathophysiology, detection, prevalence, prognosis, and therapy of this syndrome. More recent developments have continued to add data to each of these areas, with particular emphasis on the comparative value of various diagnostic procedures and the effect of therapy on prognosis. While controversy still exists concerning proper screening guidelines for the asymptomatic population, there is a growing consensus that some form of stress testing in high-risk individuals (ie, those with multiple coronary risk factors) is appropriate.

Impact of prolonged elevated heart rate on incidence of major cardiac events in critically ill patients with a high risk of cardiac complications

OBJECTIVE

To assess the incidence of major cardiac events in critically ill patients with a high risk of cardiac complications presenting with an elevated heart rate.

DESIGN AND SETTING

Observational, retrospective study in a 15-bed medical/surgical Intensive Care Unit (ICU) at a university hospital for a period of 12 months.

PATIENTS

We studied patients with a high risk of cardiac complications, according to the revised Goldman index, who were treated for at least 36 hrs in the ICU. Patients presenting with prolonged elevated heart rate, defined as a heart rate >95 beats/min for >12 hrs in at least one 24-hr period of their ICU stay, were investigated. Cardiac high-risk patients not developing this criterion served as controls. Major cardiac events, defined as nonfatal myocardial infarction, nonfatal cardiac arrest, and cardiac related death, were the primary outcome measures.

RESULTS

From a total of 791 patients, 69 patients were assessed as cardiac high-risk patients. Of 39 patients with prolonged elevated heart rates, 19 (49%) sustained major cardiac events, whereas in the control group of 30 patients, only four patients (13%) had a major cardiac event (p = .002; odds ratio, 6.2). Patients with elevated heart rate had to be treated 4.5 days longer in the ICU (p = .01), whereas the ICU and 30-day post-ICU discharge survival rates did not differ significantly.

CONCLUSIONS

In this study, we provide evidence for an increased incidence of major cardiac events in critically ill, cardiac high-risk patients with a prolonged elevated heart rate during their ICU stay. In addition, elevated heart rate was associated with a significantly longer ICU stay.

Noncardiac surgery following percutaneous coronary intervention

Patient with coronary artery disease (CAD) undergoing major noncardiac surgery (NCS) are at increased risk of serious perioperative cardiac complications. At the same time, safety of percutaneous coronary intervention (PCI) before noncardiac surgery has been questioned. This paper reviews the available literature regarding the safety of PCI before NCS. At the same time, cardiac evaluation before NCS, perioperative medical management of patients undergoing NCS, and percutaneous coronary intervention and timing of NCS is also discussed.

Postoperative 12-lead ECG predicts peri-operative myocardial ischaemia associated with myocardial cell damage

Peri-operative myocardial ischaemia is the single most important risk factor for an adverse cardiac outcome after non-cardiac surgery. The present study examines whether intermittent 12-lead ECG recordings can be used as an early warning tool to identify patients suffering from peri-operative myocardial ischaemia and subsequent myocardial cell damage. Fifty-five vascular surgery patients at risk for or with a history of coronary artery disease were monitored for peri-operative myocardial ischaemia using intermittent 12-lead ECG recordings taken pre-operatively and at 15 min, 20 h, 48 h, 72 h and 84 h postoperatively. The effectiveness of the 12-lead ECG was gauged by examining concordance with continuous 3-channel Holter monitoring and capturing peri-operative myocardial ischaemia by serial analyses of creatine kinase myocardial band isoenzyme and cardiac troponin T and I. The incidence of peri-operative myocardial ischaemia detected by 12-lead ECG was 44% and was identifiable in most patients (88%) 15 min after surgery. The incidence of peri-operative myocardial ischaemia detected by continuous monitoring was 53%, with the most severe episodes occurring intra-operatively and during emergence from anaesthesia. The concordance of the 12-lead method with continuous monitoring was 72%. The concordance of creatine kinase myocardial band isoenzyme activity with the 12-lead method was 71% and with Holter monitoring 57%. The concordance of mass concentration of creatine kinase myocardial band with 12-lead ECG recordings was 75%, and the corresponding value for Holter monitoring was 68%. The concordance of cardiac troponin T and I levels with the 12-lead method was 85% and 87%, respectively, and concordance with Holter monitoring was 72% and 66%, respectively. The postoperative 12-lead ECG identified peri-operative myocardial ischaemia associated with subsequent myocardial cell damage in most patients undergoing vascular surgery.

[Preoperative betablockers use in vascular and thoracic surgery]

OBJECTIVE

The aim of this study was to evaluate betablockers use and effect in the preoperative period in vascular and thoracic surgery.

PATIENTS AND METHODS

Retrospective study concerning patients scheduled for high or intermediate surgical risk procedure (n = 321) in a French vascular and thoracic surgery department during 2002. Eligibility for betablocker therapy was defined as previously described for inclusion criteria in Mangano's Study (N Engl J Med 1996;335:1713-20). Therapy effect was evaluated with heart rate in the operating room.

RESULTS

Forty-six percent (99/213) of eligible patients for betablockers were really treated in the preoperative period. In patients treated with betablockers, 40% appeared in the operating room with the most favorable heart rate (55-65 b/min). During surgical procedure, heart rate over 80 b/min was observed in more than 30% of patients with betablocker therapy. In patients eligible for betablocker therapy but untreated with these drugs, only 12% have received betablockers in the preoperative period.

CONCLUSION

Betablockers underuse is important in the preoperative period, and effect on heart rate is rarely optimal. This fact should encourage physicians to apply protocols for perioperative betablockers administration.

Effect of chronic β-blockade on peri-operative outcome in patients undergoing non-cardiac surgery: an analysis of observational and case control studies*

Little is known about the effect of chronic beta-adrenoceptor antagonist therapy during the peri-operative period in patients undergoing non-cardiac surgery. We conducted a literature review to identify studies examining the relationship between chronic therapy and adverse peri-operative outcome. Eighteen studies were identified in which it was possible to ascertain the incidence of adverse cardiac outcomes in those patients who were and were not receiving chronic beta-blocker therapy. None of the studies demonstrated a protective effect of chronic beta-blockade. The results of these studies were then combined and a cumulative odds ratio calculated for the likelihood of myocardial infarction, cardiac death and major cardiac complications. Patients receiving chronic beta-blocker therapy were more likely to suffer a myocardial infarction (p < 0.05). These findings differ from the published effects of acute beta-blockade. Reasons for this discrepancy are considered.

Assessment and management of patients with ischemic heart disease

OBJECTIVE

Review the perioperative management of patients who are scheduled for noncardiac surgery.

DATA SOURCE

Review of literature (PubMed, MEDLINE).

CONCLUSIONS

Patients with ischemic heart disease who undergo noncardiac surgery are at significant risk of perioperative cardiac morbidity and mortality. Recent joint guidelines from the American College of Cardiology and American Heart Association have significantly streamlined the preoperative evaluation processes. Augmented hemodynamic control with intensive perioperative pharmacologic therapy with beta-blockers and possibly alpha-2 agonist has been shown to improve perioperative cardiovascular outcomes. However, translating this information to clinical practice continues to be a challenge and requires a multi- disciplinary approach. A particular intraoperative anesthetic technique is unlikely to influence perioperative cardiac morbidity and mortality. Postoperative management with goals of decreasing hemodynamic stress is important in patients with ischemic heart disease. Diagnosis and management of perioperative myocardial infarction continues to be a challenge. However, use of cardiac specific biomarkers should improve the diagnostic process.

Frequency and Outcomes of Transient Myocardial Ischemia in Critically Ill Adults Admitted for Noncardiac Conditions

• Background Critically ill adults admitted for noncardiac conditions are at risk for acute myocardial ischemia.

• Objectives To detect myocardial ischemia and injury in patients admitted for noncardiac conditions and to examine the relationship of myocardial ischemia, injury, and acuity to cardiac events.

• Methods Transient myocardial ischemia, acuity, elevations in serum troponin I, and in-hospital cardiac events were examined in 76 consecutive patients. Transient myocardial ischemia, determined by using continuous electrocardiography, was defined as a 1-mm (0.1-mV) change in ST level from baseline to event in 1 or more leads lasting 1 or more minutes. Acuity was determined by scores on Acute Physiology and Chronic Health Evaluation II.

• Results A total of 37 ischemic events were detected in 8 patients (10.5%); 32 (86%) were ST-segment depressions, and 35 (96%) were silent. Twelve patients (15.8%) had elevated levels of troponin I. Transient myocardial ischemia, elevated troponin I levels, and advanced age were significant predictors of cardiac complications (R2 = 0.387, F = 15.2, P &lt; .001). Acuity correlated only modestly with increased length of stay in the intensive care unit (r = 0.26, P = .02) and elevated troponin I levels (r = 0.25, P = .03). Patients with transient myocardial ischemia had significantly higher rates of elevations in troponin I (P &lt; .001) and cardiac events (P &lt; .001) than did patients without.

• Conclusions Transient myocardial ischemia and advanced age are predictors of cardiac events and may indicate patients at risk for cardiac events.

Sensitivity of routine intensive care unit surveillance for detecting myocardial ischemia*

OBJECTIVE

To assess the effectiveness of routine intensive care unit surveillance compared with frequent 12-lead electrocardiogram monitoring for detecting electrocardiogram evidence suggestive of prolonged myocardial ischemia in vascular surgery patients.

DESIGN

Prospective cohort trial.

SETTING

Intensive care unit.

PARTICIPANTS

We studied 149 patients undergoing elective infrainguinal or aortic vascular surgery who were admitted to the intensive care unit postoperatively.

INTERVENTIONS

Patients were simultaneously monitored with a 10-electrode/12-lead electrocardiogram obtained every 2 mins (criterion standard) and routine intensive care unit surveillance that included standard monitoring (five-electrode/two-lead electrocardiogram with ST segment trends and routine 12-lead electrocardiogram) and clinical assessment for detecting myocardial ischemia. The results of the criterion standard were not available to the caregivers.

MEASUREMENTS AND MAIN RESULTS

We measured the ability of routine intensive care unit surveillance to detect the first 20 mins of electrocardiogram evidence suggestive of myocardial ischemia, defined as ST segment depression or elevation of >/=1 mm in two consecutive leads, during the first postoperative day. Seventeen patients (11%) had electrocardiogram evidence suggestive of prolonged myocardial ischemia, the majority of which occurred in leads V2-V4. The sensitivity of routine intensive care unit surveillance for detecting the first episode of electrocardiogram evidence suggestive of prolonged myocardial ischemia in a patient was 12% (95% confidence interval, 7-17%), and the specificity was 98% (95% confidence interval, 95-100%) with a positive predictive value of 40% (95% confidence interval, 32-48%), a negative predictive value of 90% (95% confidence interval, 85-94%), a positive likelihood ratio of 6, and a negative likelihood ratio of 1. The sensitivity of routine intensive care unit surveillance for detecting all episodes was 3% (95% confidence interval, 2-3%) and the specificity 99% (95% confidence interval, 99-100%) per 20-min monitoring interval, with a positive predictive value of 17% (95% confidence interval, 16-18%), negative predictive value of 95% (95% confidence interval, 95-96%), positive likelihood ratio of 3, and negative likelihood ratio of 1.

CONCLUSIONS

Routine intensive care unit surveillance has low sensitivity for detecting electrocardiogram evidence suggestive of prolonged myocardial ischemia compared with frequent 12-lead electrocardiograms. Because detecting electrocardiogram evidence suggestive of prolonged postoperative myocardial ischemia is important, physicians should consider alternative strategies to detect myocardial ischemia.

A comparison of intrathecal opioid and intravenous analgesia for the incidence of cardiovascular, respiratory, and renal complications after abdominal aortic surgery

Major surgery evokes a stress response that can produce deleterious consequences, especially in a population at high risk for those complications. We tested the hypothesis that decreasing or eliminating one of the sources of stress by providing intense analgesia in the immediate postoperative period via application of neuraxial opioids would decrease major nonsurgical complications. Two-hundred-seventeen patients scheduled to undergo abdominal aortic surgery were randomly allocated to receive either general anesthesia alone (control) or general anesthesia combined with intrathecal opioid (1 micro g/kg sufentanil with 8 micro g/kg preservative-free morphine injected at the L4-5 interspace). Postoperative care was identical in the two groups, including patient-controlled analgesia. Each patient provided an assessment of postoperative pain using a visual analog scale. Postopera-tive complications were recorded according to criteria established a priori. The administration of intrathecal opioid provided more intense analgesia than patient-controlled analgesia during the first 24 h postoperatively (P < 0.05). There was no difference between groups for the incidence of combined major cardiovascular, respiratory, and renal complications (P > 0.05) or mortality (P > 0.05). The incidence of myocardial damage or infarction, as defined by abnormal plasma concentration of troponin I, did not differ between the two groups (P > 0.05). In patients undergoing major abdominal vascular surgery, decrease of one contributor to postoperative stress, by provision of intense analgesia for the intraoperative and initial postoperative period, via application of neuraxial opioid, does not alter the combined major cardiovascular, respiratory, and renal complication rate.

IMPLICATIONS

Provision of intense analgesia for the initial postoperative period after major abdominal vascular surgery, via the administration of neuraxial opioid, does not alter the combined incidence of major cardiovascular, respiratory, and renal complications.

Dexmedetomidine decreases perioperative myocardial lactate release in dogs

The sympatholytic effect of the alpha(2)-adrenergic agonist dexmedetomidine may decrease emergence-related myocardial ischemic load in patients. However, a direct measure of myocardial ischemia, such as myocardial lactate release, is difficult to obtain in patients. Therefore, we studied mongrel dogs and measured myocardial lactate release, myocardial oxygen supply, hemodynamic variables, and neurohumoral indices of the stress response. After the induction of a standardized degree of borderline myocardial ischemia, either dexmedetomidine (dexmed group, n = 9) or normal saline (control group, n = 9) was infused. Measurements were repeated at the end of the anesthetic period and every 10 min during the 90-min emergence period. In the dexmed group, the cumulative emergence-related lactate release was 46% less than in the control group (95% confidence interval, 20%-80%; P = 0.02). Simultaneously, dexmedetomidine increased the endo-/epicardial blood flow ratio by 35% (control group, 0.4 +/- 0.1; dexmed group, 0.6 +/- 0.1; P = 0.03). These antiischemic effects of dexmedetomidine were accompanied by reduced plasma concentrations of norepinephrine (126 versus 577 pg/mL) and epinephrine (158 versus 1909 pg/mL) and a slower heart rate (123 +/- 6 versus 160 +/- 10 bpm, dexmed versus control). The antiischemic effect of dexmedetomidine started before emergence, as evidenced by a decreased prevalence of myocardial lactate release at that time (zero of eight dogs in the dexmed group and four of seven dogs in the control group had lactate release before emergence; P = 0.03).

IMPLICATIONS

Dexmedetomidine decreases plasma catecholamines and heart rate during emergence from anesthesia. In dogs with a coronary stenosis, these sympatholytic effects decrease myocardial lactate release and, therefore, minimize emergence-related myocardial ischemia.