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Diagnosis

Dobutamine stress echocardiography was effective for identifying patients at low risk for cardiac events after noncardiac surgery

ACP J Club. 1993 Sept-Oct;119:50. doi:10.7326/ACPJC-1993-119-2-050


Source Citation

Poldermans D, Fioretti PM, Forster T, et al. Dobutamine stress echocardiography for assessment of perioperative cardiac risk in patients undergoing major vascular surgery. Circulation. 1993 May;87:1506-12.


Abstract

Objective

To assess the predictive value of dobutamine stress echocardiography (DSE) for identifying cardiac risks in patients scheduled for elective noncardiac vascular surgery.

Design

A blinded cohort study.

Setting

A university hospital in the Netherlands.

Patients

136 consecutive patients (mean age 68 y, 116 men), unable to have exercise testing and scheduled for elective noncardiac vascular surgery (abdominal aortic aneurysm resection, aortobifemoral bypass, infrainguinal arterial reconstruction).

Description of tests and diagnostic standard

Electrocardiograms (ECGs) and cardiac risk assessments were done. DSE used 2-dimensional, precordial, standard apical and parasternal views to detect new or worsened left ventricular wall-motion abnormalities. Dobutamine was given intravenously starting at 10 µg/kg per min for 3 minutes and was increased by the same amount every 3 minutes, 3 times and was continued for 6 minutes. If the age-predicted maximal heart rate was < 85%, atropine was given, starting at 0.25 mg and increased to 1 mg. Postoperative ECGs and cardiac isoenzyme determinations were done. Outcomes were cardiac death, laboratory-confirmed myocardial infarction (MI), unstable angina, sustained ventricular dysrhythmias, and pulmonary edema.

Main outcome measures

Sensitivity, specificity, and predictive values (PVs) for DSE and risk factors for cardiac events using univariate and multivariate analysis.

Main results

1 patient had ventricular fibrillation during DSE. 15 patients had cardiac events after surgery (5 patients had fatal MIs, 9 had unstable angina, and 1 had pulmonary edema). DSE had a {sensitivity of 100%, specificity of 83%, positive likelihood ratio of 5.8, negative likelihood ratio of 0}* positive PV of 43%, and negative PV of 100%. Univariate analysis predictors of cardiac events were history of angina (odds ratio [OR] 5.1, 95% CI 1.4 to 18) and previous MI (OR 4.0, CI 1.1 to 14.4). Chest pain, clinical index based on the Detsky modification of the Goldman cardiac risk index, and ST-segment change were not predictive. Multivariate analysis showed that age > 70 years (OR 6.0, CI 1.28 to 27.9) and new wall-motion abnormality (positive DSE) (OR 95, CI 11 to 822) were independent predictors of cardiac events.

Conclusions

Dobutamine stress echocardiography identified patients at low risk for cardiac events after elective noncardiac vascular surgery. Approximately one half of patients with positive test results had cardiac events.

Sources of funding: European Society of Cardiology and Al-Azhar University.

For article reprint: Dr. P.M. Fioretti, Thoraxcenter, Ba 300, Academisch Ziekenhuis Rotterdam, Dr. Molewaterplein 40, 3015 GD Rotterdam, Netherlands. FAX 31-10-436-2995.

* Numbers calculated from data in article.


Commentary

Studies of the assessment of operative cardiovascular risk are numerous. Oddly, few studies have addressed noncardiac risk, although it may constitute 50% to 75% of the total risk for perioperative death even in patients with coronary artery disease. Remarkably, whatever noninvasive strategy is used to assess cardiovascular risk, whether it be thallium scintigraphy, stress or pharmacological echocardiography, stress ECG, or clinical stratification, the results are similar. One can identify a high-risk group with a sensitivity of 80% to 100%, but because of the rarity (3% to 8%) of postoperative MI even in those at high risk, the positive PV of these strategies for MI is between 5% and 25%. The study by Poldermans and colleagues deviates little from this script, except for the finding of a slightly higher specificity of pharmacologic stress echocardiography (positive PV of 14% for MI and 43% for MI with the less clear end points of unstable angina and pulmonary edema).

From these studies, it seems that we can identify patients with flow-limiting coronary stenoses, but we cannot predict who will have postoperative infarction because we cannot identify those patients in whom surgery will initiate the events leading to the development of an overlying thrombus. Further, revascularization may not reduce this risk for MI, because thrombosis of a coronary artery may be just as likely to develop at a noncritical stenosis. Postoperative MI is rare even in those at high risk, and no preoperative intervention has been rigorously shown to allay that risk. Thus, perhaps the best strategy is to monitor patients with any of several clinical risk factors (including age ≥ 70 years, history of hypertension, diabetes, or coronary artery disease) for the prolonged postoperative ischemia (> 2 to 4 h) that may represent the beginning of an MI. Intervention at that point may represent a reasonable strategy.

John S. Kizer, MD
University of North CarolinaChapel Hill, North Carolina, USA