Preoperative thallium scanning, selective coronary revascularization, and long-term survival after major vascular surgery

Vascular surgery patients: perioperative and long-term risk according to the ACC/AHA guidelines, the additive role of post-operative troponin elevation

AIMS

The objectives of this study are to evaluate the prognostic role of pre-operative stratification in patients undergoing elective major vascular surgery, the timing of adverse outcomes, and the predictive role of troponin (cTn).

METHODS AND RESULTS

Consecutive vascular surgery candidates (n=391) were prospectively stratified and treated according to the ACC/AHA guidelines. The patients were categorized into three groups: (1) with coronary revascularization in the past 5 years, (2) with intermediate clinical risk predictors, and (3) with minor or no clinical risk predictors. cTnI was measured post-operatively. By 18 months, 18.7% of subjects had experienced death or acute myocardial infarction (MI) (by the ACC/ESC criteria). The hazard ratio (HR) was 5.21 (95% CI=2.60-10.43; P<0.0001) in group 1 and 2.58 (95% CI=1.27-4.38; P=0.004) in group 2 when compared with group 3. Most events occurred within 30 days. Elevations of cTnI were associated with adverse outcomes even after multivariable adjustment at long-term (adjusted overall HR=4.73, 95% CI=2.92-7.65; P<0.0001) and at 30 days (adjusted HR=5.52, 95% CI=3.23-9.42; P<0.0001).

CONCLUSION

After pre-operative stratification, patients undergoing elective major vascular surgery remain at high risk of MI and death. Events occur mainly early after surgery. cTnI elevations are frequent and independently associated with increased risk. These findings suggest the need for a major re-evaluation of our approach to these patients.

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.

Complete myocardial revascularization: between myth and reality

Myocardial revascularization in patients with multi-vessel coronary artery disease may be accomplished, by percutaneous interventions or surgery, either on all diseased lesions or directed to selectively targeted coronary segments. The extent of planned revascularization is often a major determinant of treatment strategy. Revascularization of all diseased coronary segments-complete myocardial revascularization-has a potential long-term benefit, but is more complex and may increase in-hospital untoward events. Revascularization may otherwise be incomplete, either because of the operator's inability to treat all diseased coronary segments or by choice of deciding to selectively revascularize only large areas of myocardium at risk. Although incomplete revascularization may negatively affect long-term outcomes, it may be, when wisely chosen, the preferred treatment strategy in selected patient categories because of its lower immediate risks. The patient's clinical status, ventricular function, and the presence of co-morbidities may orient clinical decisions in favour of incomplete revascularization.

Advances in nuclear imaging for preoperative risk assessment

Myocardial perfusion imaging (MPI) is frequently utilized for preoperative risk assessment. Results are pertinent for long-term risk. MPI, though most frequently applied in intermediate-risk patients, may also be valuable in selected low- and high-risk individuals. Coronary stenting may alter the timing of noncardiac surgery, which should be considered when performing preoperative risk assessment.

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 beta-blockers and alpha2-adrenergic agonists to high-risk patients reduces surgical morbidity and mortality, and the benefits observed with beta-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.

A Combination of Statins and Beta-blockers is Independently Associated with a Reduction in the Incidence of Perioperative Mortality and Nonfatal Myocardial infarction in Patients Undergoing Abdominal Aortic Aneurysm Surgery

OBJECTIVE

To investigate the combined beneficial effect of statin and beta-blocker use on perioperative mortality and myocardial infarction (MI) in patients undergoing abdominal aortic aneurysm surgery (AAA).

BACKGROUND

Patients undergoing elective AAA-surgery identified by clinical risk factors and dobutamine stress echocardiography (DSE) as being at high-risk often have considerable cardiac complication rate despite the use of beta-blockers.

METHODS

We studied 570 patients (mean age 69+/-9 years, 486 males) who underwent AAA-surgery between 1991 and 2001 at the Erasmus MC. Patients were evaluated for clinical risk factors (age>70 years, histories of MI, angina, diabetes mellitus, stroke, renal failure, heart failure and pulmonary disease), DSE, statin and beta-blocker use. The main outcome was a composite of perioperative mortality and MI within 30 days of surgery.

RESULTS

Perioperative mortality or MI occurred in 51 (8.9%) patients. The incidence of the composite endpoint was significantly lower in statin users compared to nonusers (3.7% vs. 11.0%; crude odds ratio (OR): 0.31, 95% confidence interval (CI): 0.13-0.74; p=0.01). After correcting for other covariates, the association between statin use and reduced incidence of the composite endpoint remained unchanged (OR: 0.24, 95% CI: 0.10-0.70; p=0.01). Beta-blocker use was also associated with a significant reduction in the composite endpoint (OR: 0.24, 95% CI: 0.11-0.54). Patients using a combination of statins and beta-blockers appeared to be at lower risk for the composite endpoint across multiple cardiac risk strata; particularly patients with 3 or more risk factors experienced significantly lower perioperative events.

CONCLUSIONS

A combination of statin and beta-blocker use in patients with AAA-surgery is associated with a reduced incidence of perioperative mortality and nonfatal MI particularly in patients at the highest risk.

Cardiac Troponin After Major Vascular Surgery

OBJECTIVES

We sought to determine the role of preoperative predictors, particularly ischemia, on preoperative thallium scanning (PTS) and coronary revascularization on low-level and conventional troponin elevations after major vascular surgery.

BACKGROUND

Postoperative cardiac troponin (cTn) elevations have recently been shown to predict both short- and long-term mortality after vascular surgery.

METHODS

The perioperative data, including PTS and subsequent coronary revascularization, continuous perioperative 12-lead ST-segment trend monitoring, cTn-I and/or cTn-T, and creatine kinase-MB fraction in the first three postoperative days, were prospectively collected in 501 consecutive elective major vascular procedures.

RESULTS

Moderate to severe inducible ischemia on PTS was associated with a 49.0% incidence of low-level (cTn-I >0.6 and/or cTn-T >0.03 ng/ml) and 22.4% conventional (cTn-I >1.5 and/or cTn-T >0.1 ng/ml) troponin elevation. In contrast, patients with preoperative coronary revascularization had 23.4% and 6.4% low-level and conventional troponin elevations, respectively, similar to patients without ischemia on PTS. By multivariate logistic regression, ischemia on PTS was the most important predictor of both low-level and conventional troponin elevations (adjusted odds ratios [ORs] 2.5 and 2.7, p = 0.02 and 0.04, respectively), whereas preoperative coronary revascularization predicted less troponin elevations (adjusted ORs 0.35 and 0.16, p = 0.045 and 0.022, respectively). Postoperative ischemia (>10 min), the more so prolonged (>30 min) ischemia was the only independent predictor of troponin elevation if added with the preoperative predictors to the multivariate analysis (ORs 15.8 and 22.8, respectively, p < 0.001).

CONCLUSIONS

Troponin elevations occur frequently after vascular surgery. They are strongly associated with postoperative ischemia, predicted by inducible ischemia on PTS, and reduced by preoperative coronary revascularization.

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.