Perioperative Cardiac Risk Stratification and Modification in Abdominal Aortic Aneurysm Repair

Cardiovascular complications are important causes of morbidity and mortality following vascular surgery. Adequate preoperative risk assessment and perioperative management may modify postoperative mortality and morbidity and improve long-term prognosis. The objective of this review is to examine the present day knowledge regarding the preoperative evaluation and perioperative management of patients undergoing noncardiac surgery, focusing specifically on abdominal aortic aneurysm (AAA) repair.

Clinical markers combined with ECG and surgical risk assessment can effectively divide patients in a truly low-risk, intermediate and high-risk population. Low-risk patients can probably be operated on without additional cardiac testing. Notably, due to the surgical risk, AAA patients are never low-risk patients. Intermediate-risk and high-risk patients are referred for cardiac testing to exclude extensive stress induced myocardial ischemia, as beta-blockers provide insufficient myocardial protection in this case and preoperative coronary revascularization might be considered. Whether patients at intermediate risk without ischemic heart disease should be treated with statins and/or beta-blockers is still controversial. In high-risk patients, it is strongly advised to administer beta-blockers with heart rate determined dose adjustment, while the effects of preoperative revascularization remain subject to debate.     

Perioperative issues: myocardial ischemia and protection--beta-blockade

Approximately one third of patients undergoing noncardiac surgery have coronary artery disease, and cardiovascular complications are an important cause of perioperative morbidity and mortality. Several algorithms are available to assess the risk for peri-operative cardiac events. Although preoperative risk assessment is useful in identifying patients at greatest risk for cardiac complications, recent investigations have provided additional guidance in choosing interventions to improve perioperative outcomes. These investigations show that perioperative beta-blockers significantly reduce morbidity and mortality in noncardiac surgery and appear to offer the greatest benefit to high-risk patients. Because of the lower complication rate in intermediate- and low-risk patients and the absence of large randomized controlled trials, the role of beta-blockers in this population is less well-defined.     

Preoperative cardiac risk management

Approximately 100 million people undergo noncardiac surgery annually worldwide. It is estimated that around 3% of patients undergoing noncardiac surgery experience a major adverse cardiac event. Although cardiac events, like myocardial infarction, are major cause of perioperative morbidity or mortality, its true incidence is difficult to assess. The risk of perioperative cardiac complications depends mainly on two conditions: (1) identified risk factors, and (2) the type of the surgical procedure. On that basis, different scoring systems have been developed in order to accurately assess the perioperative cardiac risk and to improve the patient management. Importantly, patients with estimated high risk should be tested preoperatively by non-invasive cardiac imaging modalities. According to test results, they can proceed directly to planed surgery with the use of cardioprotective drugs (beta-blockers, statins, aspirin), or to myocardial revascularization prior to non-cardiac surgery. In this review, we discuss the role of clinical cardiac risk factors, laboratory measurements, additional non-invasive cardiac testing, and consequent strategies in perioperative management of patients undergoing noncardiac surgery.     

Strategies in the high-risk cardiac patient undergoing non-cardiac surgery

The risk of perioperative myocardial infarction or cardiac death in patients undergoing non-cardiac surgery may be estimated by clinical risk factor analysis and by myocardial stress testing. While stress testing modalities accurately delineate reversible myocardial ischaemia, their positive predictive value is low, and it is not clear whether their implementation improves outcome when compared to risk stratification alone. Similarly, it remains to be shown that preoperative coronary revascularization is an effective strategy in reducing perioperative risk. Recent reports indicate that surgery undertaken in the first weeks after percutaneous coronary interventions may be associated with a significantly increased rate of major complications. Administration of β-blockers and α₂-adrenergic agonists to high-risk patients reduces surgical morbidity and mortality, and the benefits observed with β-blockers may extend long after the operative period. In high-risk patients undergoing major surgery, pulmonary artery catheter-guided haemodynamic optimization has not been associated with better outcomes, whereas use of regional anesthetic techniques decreases the incidence of postoperative pulmonary, but not cardiac, complications.     

Cardiac complications after elective major vascular surgery

Cardiac complications are the major cause of perioperative and late mortality and morbidity in patients undergoing elective major vascular surgery. This review focuses on the pathophysiology of perioperative complications, risk assessment and risk reduction strategies, all related to cardiovascular disease. Patients without cardiac risk factors are considered to be at low risk and no additional evaluation for coronary artery disease is recommended; β-adrenergic blockers may reduce perioperative cardiac events; patients with one or more risk factors represent an intermediate to high-risk population. β-Adrenergic blockers should be prescribed to all patients and coronary revascularization should be reserved for patients who have a clearly defined need for revascularization independent of the need for vascular surgery.     

An Appraisal of Different Cardiac Risk Reduction Strategies in Vascular Surgery Patients

OBJECTIVES: to summarize existing evidence regarding the benefits and the risks of all available interventional and medical means aimed at cardiac risk reduction in patients undergoing vascular surgery. DESIGN: review of the literature. MATERIALS AND METHODS: a critical review of all studies examining the impact of various prophylactic cardiac maneuvers on perioperative outcome following vascular surgery was performed. Overall mortality, cardiac mortality and myocardial infarction rate were used as the outcome measures. RESULTS: coronary artery bypass grafting is associated with a 60% decrease in perioperative mortality in patients undergoing vascular surgery, but in most of the cases this decrease does not outweigh the combined risk of the cardiac and the subsequent noncardiac vascular procedure. Data supporting the cardioprotective effect of percutaneous transluminal angioplasty in the perioperative setting are insufficient. beta-blockade has been shown to decrease perioperative mortality and cardiac morbidity in both high-risk (strong evidence) and low-risk (weak evidence) patients. CONCLUSIONS: coronary revascularization is rarely indicated to simply get the patient through vascular surgery and should be reserved for patients who would need it irrespective of the scheduled vascular procedure. Among all available pharmacological agents, including beta-blockers, alpha-agonists, calcium channel blockers and nitrates, only beta-blockers have been proven to reduce the cardiac risk of vascular surgery.     

Cardiac risk reduction in non-cardiac surgery: the role of anaesthesia and monitoring techniques

Cardiac complications are the major cause of perioperative morbidity and mortality of patients undergoing non-cardiac surgery. This is related to the frequent presence of underlying coronary artery disease. In the last few decades, attention has focused on preoperative cardiac risk assessment that may help to identify patients at increased cardiac risk for whom cardioprotective medication and, when indicated, coronary revascularization may improve perioperative outcome. On the other hand, less attention was given to the role of anaesthesia and monitoring techniques in the cardiac risk management of high-risk patients undergoing non-cardiac surgery. The aim of this review was to summarize the current evidence from published studies on the effect of the type of anaesthesia and monitoring techniques on perioperative cardiac outcome in non-cardiac 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.     

Preoperative cardiac risk assessment prior to noncardiac surgery

Summary. Cardiac complications remain an important cause of perioperative morbidity and mortality with noncardiac surgery, despite improvement in surgical techniques and anaesthetic management. Therefore preoperative cardiovascular risk assessment plays a pivotal role in management of patients prior to noncardiac surgery. Thorough history-taking and careful examination are essential to consider further diagnostic steps in order to predict the patient's individual perioperative cardiac risk as accurately as possible. Besides elaboration of medical therapy, cardiac catherization and even balloon angioplasty or bypass surgery must be considered if indicated by preoperative cardiac testing.      

Preoperative management of the patient with coronary artery disease before abdominal aortic surgery

Coronary artery disease accounts for more than half of the morbidity and mortality associated with abdominal aortic surgery. To improve the results of vascular surgery, the risk of perioperative cardiac ischemia should be evaluated in each patient. Routine coronary angiography demonstrated severe correctable coronary artery disease in 14% of patients who had no history or electrocardiographic evidence of coronary artery disease. Exercise testing before abdominal aortic aneurysm repair will identify patients at high risk of cardiac ischemia. Dipyridamole-thallium imaging will identify high-risk patients before surgery for aortoiliac occlusive disease. Some patients with symptomatic coronary disease who are at extremely high risk should undergo preoperative coronary revascularization. Others should have their vascular surgery deferred, because their cardiac risk may exceed the anticipated benefit of the vascular surgery. Patients at moderate risk may need more intensive intraoperative monitoring. Patients without evidence of cardiac ischemia with stress may undergo vascular surgery with a low risk of perioperative cardiac ischemia. Finally, patients who have evidence of ischemic heart disease should be considered for coronary revascularization following successful vascular repair in order to prolong their survival.     

Preoperative cardiac assessment of the candidate for major resective pancreatic surgery.

The risk of perioperative cardiac morbidity and mortality can be predicted based on clinical assessment and noninvasive testing for the detection of myocardial ischemia. Appropriate preoperative interventions in high-risk patients are indicated. Medical intervention with beta blockade is particularly effective.     

Preoperative cardiac assessment for patients with infrarenal abdominal aortic aneurysms: a survey of current practice by vascular surgeons in New South Wales and Australian Capital Territory

Background: The reported mortality rate following open elective repair of abdominal aortic aneurysm (AAA) varies between 0 and 12%. Much of the mortality and major morbidity is caused by cardiac events. The evidence regarding best practice for cardiac assessment and optimization of this patient group is unclear. The aim of the present study was to evaluate current practice of cardiac risk factor assessment by vas­cular surgeons in New South Wales (NSW) and Australian Capital Territory (ACT) for patients undergoing open elective repair of infrarenal AAA. Methods: A postal questionnaire was sent to 46 surgeons in NSW and ACT identified as expressing a principal or major interest in vascular surgery. If no response was received within 3 weeks, a second questionnaire was sent and if no response was received after the second mailing, a telephone survey of non‐responders was conducted. Data were collated regarding the importance of risk factors elicited by clinical history, preoperative investigation, referral for cardiological opinion, use of perioperative beta‐blockade and the timing of aortic surgery in relation to coronary artery revascularization and acute myocardial infarction. Results: The overall response rate was 87% (40/46) and the median (range) response time was 14 (4?109) days. Only 22 of 40 and 23 of 40 surgeons consider diabetes mellitus or renal impairment, respectively, to be important when assessing cardiac risk and 34 of 40 surgeons do not employ a validated risk index in preoperative assessment. Sixteen of 40 surgeons refer all patients needing AAA repair to a cardiologist, while 24 of 40 would initiate cardiac investigations themselves (either stress electrocardiography, scintigraphy or echocardiography). Seventeen surgeons always or usually commenced perioperative beta‐blockade with wide variations in the commencement (1 to > 28 days preoperatively) and duration (< 1 week to > 28 days postoperatively) of treatment. The timing of AAA repair following coronary revascularization ranged from < 1 week to 6 months and delay in surgical repair of AAA following myocardial infarction ranged from < 1 week to > 6 months. Conclusion: Preoperative assessment of cardiac risk in patients for repair of AAA lacks consensus among vascular surgeons in NSW and ACT. The diversity of clinical practice may rest with the paucity of prospective trials published in the medical literature or the influence of local institutional facilities.     

Preoperative risk assessment in vascular surgery patients

The patient scheduled for peripheral vascular surgery is an increased anaesthetic challenge, mainly because of coexisting generalized cardiovascular atherosclerotic involvement leading to a high risk of perioperative cardiac complications. In clinical practice it is of importance preoperatively to predict, as accurately as possible, the potential risk of complications so that proper risk-reducing measures can be taken. Relevant clinical data, which have been included by Goldman and Detsky in multifactorial cardiac risk indices, are of potential value for differentiating between patients at low, intermediate, or high risk of perioperative cardiac morbidity and mortality. Patients with low risk scores can be accepted for surgery without further testing, thereby allowing more extensive cardiac testing, such as ambulatory ECG monitoring, exercise stress testing, echocardiography, dipyridamole thallium imaging, or coronary angiography, to be reserved for patients with higher risk scores or overt cardiac problems. The risk stratification is of importance not only for decisions on preoperative prophylactic therapeutic measures (e.g. optimization of medical therapies, coronary artery revascularization), but also for decisions on intraoperative anaesthetic management and postoperative care.     

Anaesthesia for patients with cardiac disease undergoing non-cardiac surgery

Cardiovascular comorbidities are amongst the most important modifiable risk factors in patients undergoing non-cardiac surgery. Likewise, cardiac complications are a leading cause of all perioperative morbidity and mortality. Major adverse events include acute myocardial ischaemia, infarction, congestive cardiac failure, arrhythmias, and cardiac arrest. Preoperative assessment and planning aims to minimize these risks. Although testing is important, it must be rationalized lest resources are misused and undue delays ensue. Current thinking in preoperative therapy, intraoperative management and postoperative care is discussed. Although most patients with cardiac disease have ischaemic heart disease, other specific cardiac conditions and principles of their management are briefly considered.     

Patients with positive preoperative stress tests undergoing vascular surgery

OBJECTIVE: To examine the perioperative cardiac morbidity and mortality in patients undergoing major vascular surgery with beta-blockade after a positive stress test or cardiac catheterization. DESIGN: Retrospective review of a quality assurance database. SETTING: A university teaching hospital. PARTICIPANTS: A consecutive series of 31 patients undergoing peripheral vascular or aortic surgery after a positive stress test or catheterization between November 2001 and September 2003. INTERVENTION: None. MEASUREMENTS AND MAIN RESULTS: All 31 patients had a preoperative positive stress test and/or cardiac catheterization, with 12 having multiple areas at risk for myocardial ischemia. None had an intervening coronary revascularization. Twenty-seven had at least one of the intermediate clinical predictors as defined by the American College of Cardiology and 7 had a left ventricular ejection fraction < 40%. Twenty-three patients had been on a beta-blocker and continued on it, while the remainder started on it de novo perioperatively. None of the patients suffered from myocardial infarction, congestive heart failure, or cardiac death perioperatively. CONCLUSIONS: This case series reports on the authors' experience with patients undergoing high-risk vascular surgery after a positive stress test or catheterization, but without an intervening coronary intervention. All patients received perioperative beta-blockade and had a very low adverse cardiac event rate. With reduction of adverse events by beta-blockade, the likelihood of a positive event may be reduced and the utility of the test in risk stratification may be questioned.     

Preoperative cardiac assessment in patients undergoing major vascular surgery

The aim of this study was to evaluate the effectiveness of a preoperative standardized cardiac assessment in patients undergoing major vascular surgery. From January 2005 to December 2006, 1446 elective interventions for major vascular diseases (carotid stenosis, CS; abdominal aortic aneurysm, AAA; peripheral arterial obstructive disease, PAOD) were performed; 1090 out of these patients underwent preoperative diagnostic assessment on an outpatient basis. Thirty-day results in terms of cardiac mortality and morbidity rates were recorded. Patients suffered from a CS in 578 cases (53%), an AAA in 303 cases (27.8%) and a PAOD in 209 cases (19.2%). Four hundred thirty-two patients (39.6%) underwent further evaluation of cardiac functional capacity with non-invasive stress testing. Sixteen patients were successfully treated prior to vascular surgery. Thirty-day cardiac mortality and morbidity rates were 0.2% and 3.9%, respectively. A positive preoperative non-invasive stress testing did not affect 30-day cardiac outcomes. In conclusion, the use of an accurate preoperative cardiac assessment allowed us to obtain satisfactory perioperative results in patients undergoing major vascular surgery. Routine preoperative evaluation with non-invasive stress testing did not seem to improve perioperative cardiac results.     

Preoperative cardiac risk assessment: an updated approach.

HYPOTHESIS: We provide an updated algorithm for approaching preoperative cardiac risk assessment in patients undergoing noncardiac surgery. DESIGN: A National Library of Medicine PubMed literature search was performed dating back to 1985 using the keywords "preoperative cardiac risk for noncardiac surgery." This search was restricted to English language articles involving human subjects. RESULTS: Patient-specific and operation-specific cardiac risk can be determined clinically. Patients with major cardiac risk factors have a high incidence of perioperative cardiac complications, whereas the risk is less than 3% for low-risk patients. For intermediate-risk patients, no prospective randomized studies demonstrate the efficacy of noninvasive stress testing (dipyridamole thallium or dobutamine echocardiography) or of subsequent coronary revascularization for preventing perioperative cardiac complications. Recent studies demonstrate that perioperative beta-blockade significantly reduces the adverse cardiac event rate in intermediate-risk patients. CONCLUSIONS: Most patients with high cardiac risk should proceed with coronary angiography. Patients with low cardiac risk can proceed to surgery without noninvasive testing. For intermediate-risk patients, consideration may be given to further stress testing prior to surgery; however, in most patients, proceeding to surgery with perioperative beta-blockade is an acceptable alternative.     

Indications for myocardial revascularization before endovascular aortic repair

Due to the strong relationship between abdominal aortic aneurysm (AAA) and coronary morbidity and mortality, it seems mandatory to spend some more time investigating about coronary risk of our endovascular aortic repair (EVAR) patients. Physical examination, basic laboratory testing and ECG will allow us to determine whether the surgical risk for a patient is low, moderate or high. In general a patient who is at low risk will not need any further evaluation. Those at who are at high risk usually will undergo coronary angiography. Patients who are at intermediate risk, probably the largest subgroup of patients candidate to EVAR, will often need additional testing like assessment of resting left ventricular function, exercise stress testing, pharmacological stress testing, ambulatory ECG monitoring, and coronary angiography as well as exercise echocardiography or exercise myocardial perfusion imaging should be considered. Patients undergoing an EVAR procedure, who are found to have prognostic high-risk coronary anatomy and in whom long-term outcome would likely be improved by coronary revascularization, should generally undergo revascularization first. In conclusion, we recommend to evaluate the cardiac status of EVAR's patients in order to reduce the most common serious morbidity related to this new therapeutic modality.     

The role of coronary artery disease in complications of abdominal aortic aneurysm surgery

Coronary artery disease (CAD) is a major cause of morbidity and mortality after elective surgical repair of abdominal aortic aneurysm (AAA). The aim of this study was to determine the relationship between the extent of CAD observed in coronary angiograms (more than 50% stenosis) and the frequency of postoperative myocardial ischemic complications in a consecutive series of 84 patients who underwent elective AAA repair. Ninety-four percent of the patients with clinical evidence of CAD had significant disease as observed in coronary angiograms and eight patients had left main CAD. Seventy-two patients underwent AAA repair with a mortality rate of 1.4%; five patients had preliminary myocardial revascularization, and AAA surgery was not recommended for four patients because of severe cardiac disease. Postoperative myocardial ischemic complications occurred in 13.4% of the patients who had undergone surgery--almost exclusively in patients with clinical evidence of CAD. Both myocardial ischemia and preoperative intervention were more frequent in patients with double- or triple-vessel disease than in patients with less extensive disease. Patients with symptoms and with double- or triple-vessel CAD have a high risk of developing myocardial ischemia after AAA surgery. Preliminary myocardial revascularization may be beneficial in this group of patients.     

Critical appraisal of cardiac risk stratification before elective vascular surgery

This study was undertaken to evaluate the efficacy of the cardiac risk stratification protocol proposed by the American College of Cardiology/American Heart Association (ACC/AHA) in predicting cardiac morbidity and mortality associated with elective, major arterial surgery. Cardiac risk stratification using ACC/AHA guidelines was done on 425 consecutive patients before 481 elective cerebrovascular (n = 146), aortic/inflow (n = 166), or infrainguinal (n = 169) procedures at an academic Veterans Affairs Medical Center. Cardiac risk was stratified as low, intermediate, or high based on clinical risk factors, such as, Eagle criteria, history of cardiac intervention, patient functional status, results of noninvasive cardiac stress testing, and coronary angiography with coronary revascularization performed when appropriate. Outcomes (myocardial infarction, unstable angina, congestive heart failure, ventricular arrhythmia, cardiac death, and mortality) within 30 days of surgery were compared between the various risk stratification groups. Univariate and multivariate analyses were used to identify clinically useful prognostic variables from the preoperative cardiac evaluation algorithm. Overall mortality (1.7%), cardiac death (0.4%), and adverse cardiac event (4.8%) rates were low, but cardiac death and morbidity were increased (p < 0.05) in high-risk stratified patients (3.4%, 11.9%) compared to intermediate (0%, 2.8%) and low (0%, 4.0%) cardiac risk groups. The presence of 3-vessel angiographic coronary artery occlusive disease was an independent predictor of cardiac morbidity, while inducible ischemia by cardiac stress imaging was not. Previous coronary revascularization was associated with increased mortality as was the development of a non-cardiac complication. Cardiac risk assessment identified 78 (18%) patients with indications for coronary angiography. Angiographic findings resulted in coronary artery intervention (9-angioplasty; 4-bypass grafting) in 13 (3%) patients who experienced no adverse cardiac events after the planned vascular surgery (15 procedures). Cardiac risk stratification using ACC/AHA guidelines can predict adverse cardiac events associated with elective vascular surgery; however, protocol modification by increased reliance on Eagle criteria and less use of cardiac stress testing can improve identification of the "highest risk" patients who may benefit from prophylactic coronary intervention.