Relative effectiveness of four preoperative tests for predicting adverse cardiac outcomes after vascular surgery: a meta-analysis.

Various noninvasive tests have been proposed to stratify perioperative cardiovascular risk, including dipyridamole thallium scintigraphy (DTS), ejection fraction estimation by radionuclide ventriculography (RNV), ischemia monitoring by ambulatory electrocardiography (AECG), and dobutamine stress echocardiography (DSE). Which of these tests is most effective for predicting adverse perioperative cardiac outcome? To answer this question, and also to stimulate future studies, we evaluated 56 studies examining one or more of the four tests. We conducted meta-analysis on 20 studies that met the inclusion criteria. Outcome measures evaluated were cardiac death or myocardial infarction occurring during hospital stay or within 1 mo after surgery. Relative risk (RR), which is the probability of adverse cardiac outcome when the test is positive divided by the probability of adverse outcome when the test is negative, was used to combine evidence from different studies. An empirical Bayes procedure with a normal-normal hierarchic model was then used to obtain a meta-analytic confidence interval for the overall median of the relative risks. The between-study variance was estimated using the method of moments approach described by DerSimonian and Laird (Controlled Clin Trials 1986;7:177-88). Combined (median) RR [95% confidence interval (CI)] and the number of studies included in our meta-analysis for different evaluative tests were as follows: DTS 4.6 (2.1-10.4) (n = 6); RNV 3.7 (1.6-8.3) (n = 5); AECG 2.7 (1.4-5.1) (n = 6), and DSE 6.2 (1.7-22.8) (n = 3). We conclude that while DTS, RNV, AECG, and DSE are effective (the 95% CIs are greater than 1.0) in predicting the cardiac outcome after vascular surgery, the data are not definitive in determining the optimal test (95% CIs for RR overlap). Future studies should include DSE, as this test shows great promise for predicting adverse cardiac events after vascular surgery.