Assessment of perioperative risk: have we put the cart before the horse

Managing patients undergoing non-cardiac surgery: need to shift emphasis from risk stratification to risk modification

Many patients undergo non-invasive testing for the detection of coronary artery disease before non-cardiac surgery. This is despite the low predictive value of positive tests in this population and the lack of any evidence of benefit of coronary revascularisation before non-cardiac surgical procedures. Further, this strategy often triggers a clinical cascade exposing the patient to progressively riskier testing and intervention and results in increased costs and unnecessary delays. On the other hand, administration of beta blockers, and more recently statins, has been shown to reduce the occurrence of perioperative ischaemic events. Therefore, there is a need for a shift in emphasis from risk stratification by non-invasive testing to risk modification by the application of interventions, which prevent perioperative ischaemia--principally, perioperative beta adrenergic blockade and perhaps treatment with statins. Clinical risk stratification tools reliably identify patients at high risk of perioperative ischaemic events and can guide in the appropriate use of perioperative medical treatment.

Age and history of cardiac disease as risk factors for cardiac complications after peripheral vascular surgery in diabetic patients

OBJECTIVE

To examine the relationship of age and clinical factors to postoperative cardiovascular events in a cohort of diabetic patients undergoing peripheral vascular surgery.

PATIENTS AND METHODS

In this cohort study, 316 diabetic patients were followed up prospectively after femoral-to-distal artery bypass surgery. The major end points of the study were all-cause mortality and cardiac morbidity (cardiac events defined as nonfatal myocardial infarction, unstable angina, and congestive heart failure).

RESULTS

The overall postoperative cardiac event rate was 17.1% (54/316), with a 7.6% (24/316) rate of postoperative death or nonfatal myocardial infarction. Older diabetic patients (> or = 65 years) had a complication rate of 19.9% (43/216) compared with an 11.0% (11/100) complication rate in younger diabetic patients (< 65 years) (P = .02). Younger diabetic patients with a clinical history of coronary artery disease had an event rate of 18.2% (39/216) compared with an event rate of 2.4% (1/42) in younger diabetic patients without known cardiac disease (P = .02). In contrast, event rates were similar (20.7% [150/208] vs 18.2% [66/108]) in older diabetic patients with or without prior evidence of cardiac disease.

CONCLUSION

Advanced age and clinical evidence of coronary artery disease are important determinants of postoperative outcome in diabetic patients undergoing peripheral vascular surgery.

Angiographic correlates of cardiac death and myocardial infarction complicating major nonthoracic vascular surgery

In a case-control study of 63 patients undergoing major nonthoracic vascular surgery with prior cardiac catheterization, we found total coronary occlusion serving viable myocardium and "nonobstructive" lesions to be the most common proximate cause of perioperative myocardial infarction or death. The extent of coronary disease by several measures was significantly correlated with adverse outcome, and prior bypass surgery appeared to be protective.

Last-minute preoperative cardiology consultations: epidemiology and impact

To identify clinical predictors of last-minute preoperative cardiology consultations and to evaluate the impact of these consultations on patient care, we performed a retrospective case-control study including all 166 patients who received unscheduled cardiology consultations at the preadmission testing center (PATC) of an urban teaching hospital. Control subjects were 166 patients matched by date and category of surgical procedure. Significant (p < 0.05) independent predictors of last-minute consultations included history of myocardial infarction (odds ratio [OR] = 23.7; 95% confidence interval [CI] = 1.5 to 373), history of chest pain (OR = 15.3; 95% CI = 3.7 to 62.9), history of chronic obstructive lung disease (OR = 5.9; 95% CI = 1.1 to 32.9), prior echocardiography (OR = 3.4; 95% CI = 1.2 to 9.8), and age (OR per decade = 1.1; 95% CI = 1.04 to 1.1). Thus among patients undergoing elective noncardiac surgery, last-minute preoperative consultations are common and are usually precipitated by an abnormal electrocardiogram or history of cardiovascular disease. Last-minute consultations may be preventable if those patients with risk factors for consultation are identified in advance of the preadmission evaluation and referred for elective consultation.

Improved cardiac risk stratification in major vascular surgery with dobutamine-atropine stress echocardiography

OBJECTIVES

This study sought to optimize preoperative cardiac risk stratification in a large group of consecutive candidates for vascular surgery by combining clinical risk assessment and semiquantitative dobutamine-atropine stress echocardiography.

BACKGROUND

Dobutamine-atropine stress echocardiography has been used for the prediction of perioperative cardiac risk in a small group of patients scheduled for elective major vascular surgery on the basis of the presence or absence of stress-induced regional left ventricular wall motion abnormalities.

METHODS

Clinical risk assessment and dobutamine-atropine stress echocardiography were performed in 302 consecutive patients presenting for major vascular surgery. The extent and severity of stress wall motion abnormalities and the heart rate at which they occurred, in addition to the presence of wall motion abnormalities at rest, were assessed.

RESULTS

The absence of clinical risk factors (angina, diabetes, Q waves on the electrocardiogram, symptomatic ventricular tachyarrhythmias, age > 70 years) identified a low risk group of 100 patients with a 1% cardiac event rate (unstable angina). Dobutamine-atropine stress echocardiographic findings were positive in 72 patients. Twenty-seven patients had a perioperative cardiac event (cardiac death in 5, nonfatal infarction in 12, unstable angina pectoris in 10); all 27 patients had positive stress test results (positive predictive value 38%, negative predictive value 100%). The semiquantitative assessment of the extent and severity of ischemia did not provide additional prognostic information in patients with positive test results. In contrast, the heart rate at which ischemia occurred defined a high risk group with a low ischemic threshold (38 patients with 20 events [53%]) and an intermediate risk group with a high ischemic threshold (34 patients with 7 events [21%]). All 5 patients with a fatal outcome and 8 of 12 with a nonfatal myocardial infarction were in the high risk group with a low ischemic threshold.

CONCLUSIONS

Clinical variables identify 33% of patients at very low risk for perioperative complications of vascular surgery in whom further testing is redundant. In all other candidates, dobutamine-atropine stress echocardiography is a powerful tool that identifies those patients at intermediate risk and a small group at very high risk. Risk stratification with a combination of clinical assessment and pharmacologic stress echocardiography has the potential to facilitate clinical decision making and conserve resources.

Routine coronary arteriography before abdominal aortic aneurysm repair

BACKGROUND

As cardiac complications constitute the principal cause of early and late morbidity and mortality after the surgical treatment of abdominal aortic aneurysm (AAA), a prospective study was planned to evaluate the effects of revascularization of coronary arteries on survival after AAA repair during early and long-term follow-up periods.

PATIENTS AND METHODS

A total of 125 patients underwent elective repair of AAA between 1986 and 1994. Coronary arteriography was performed in all cases. All cases with critical left anterior descending artery (LAD) lesions underwent a coronary artery bypass operation either simultaneously or shortly before AAA repair. In addition, percutaneous transluminal coronary angioplasty (PTCA) was performed for symptomatic and critical stenosis of arteries other than the LADs, or if noncritical but symptomatic stenosis of the LADs existed. Early and late follow-up data were obtained for all cases, and late-term cumulative survival rates were calculated.

RESULTS

Coronary artery lesions were found in 66 (53%) cases. In 24 cases, AAA repairs were performed 2.3 (mean) months after coronary artery bypass grafting (CABG), whereas in 4 cases both procedures were performed simultaneously. PTCA was performed in 4 cases 3 to 4 days prior to the abdominal surgery. Even though the coronary artery lesions were found inoperable in 7 cases, these patients underwent repair of AAA because of rapidly expanding and painful aneurysms. Early mortality rate was 4% (5 cases), in which 3 of these were from the group inoperable for CABG. A mean follow-up of 3.17 years (3 to 87 months) was achieved for all discharged patients. Cumulative survival rates for 6 months and 1, 2, 3, and 6 years were 99%, 99%, 95%, 93%, and 89%, respectively.

CONCLUSIONS

The results of this study emphasize the importance of coronary artery revascularization for early, and especially for late, survival after AAA repair.

Requirements for controlled clinical trials of preoperative cardiovascular risk reduction

Although controlled clinical trials have had a major impact in many areas of cardiovascular disease management, they have had little influence on preoperative cardiac risk reduction. Over the past 2 years, we have conducted the Reduction of Cardiac Operative Risk (RCOR) Trial, a pilot study designed to determine enrollment and event rates for a definitive trial evaluating a strategy to reduce cardiac risk associated with noncardiac surgery. This experience indicates that a successful, definitive trial will require recognition of the multiple questions to be answered, accurate identification of the study population, a large sample size, cooperation between internists, surgeons, and anesthesiologists, and strategies to minimize cost. The high costs and difficulties of such a trial are likely to be outweighed by the enormous benefit of identifying the proper strategy for the use of the expensive testing methods that are currently employed.

Coronary artery disease in patients with peripheral vascular disease

For patients requiring peripheral vascular surgery, coronary artery disease is the major determinant of perioperative mortality and long-term survival. The management of coronary artery disease in these patients is controversial as no randomized blinded prospective studies have been conducted. Data on the prevalence, diagnosis and management are reviewed.