Ankle Brachial Index As A Predictor For Abnormal Cardiovascular Stress Test And Cardiovascular Outcomes

Background: The combination of ankle brachial index (ABI) and other risk stratification tools has been evaluated previously. However baseline ABI in patients admitted for chest pain prior to stress testing to predict increased probability of abnormal stress test and MACE (major cardiovascular adverse events) has not been studied. Methods: Patients (n= 342) admitted for chest pain with normal or unchanged electrocardiogram and negative troponin T who were referred for myocardial perfusion study were enrolled in this prospective observational study and followed for one year. The first part of the study was to assess if an abnormal ABI increases the probability of an abnormal stress test and the second part was to measure one-year outcome for MACE (Angina, MI, CHF, TIA/Stroke and deaths) based on their stress test and ABI results. Multivariable logistic regression modeling is used to interpret the data. Results: In our study population 83% of the patients had Framingham risk score less than 20. Twenty-nine percent of the patients with normal ABI and 40% of the patients with abnormal ABI had abnormal stress test. The difference is statistically insignificant. After adjusting for different variables abnormal ABI was found to have stronger correlation with MACE (Odds ratio 2.9, p 0.01, CI 1.2 - 6.7) as compared to abnormal stress test (Odds ratio 0.92, p 0.84 CI 0.3 - 2.1). Conclusion: In our study cohort an abnormal ABI, irrespective of the stress test results, was an independent predicator of MACE at one year. We can conclude that there is very weak temporal relationship between abnormal ABI and abnormal stress test in low risk population and asymptomatic peripheral vascular disease is a strong independent predictor of MACE, even in this low risk population. We can also conclude that ABI during stress testing can be used for risk stratification. Future studies may need more power in this low risk population.