Abstract 18668: Is Functional Capacity a Reliable Predictor in Pre-Operative Cardiac Risk Stratification?
Introduction: Functional capacity has been used both in guidelines and clinical practice as an important predictor of adverse events in pre-operative cardiac risk stratification. It is measured in metabolic equivalents (METs). Current guidelines advise that patients can proceed with surgery if the functional capacity is more than 4 METs with no further investigations. But it is unclear whether a history of good functional capacity is reliable predictor.
Methods: In this retrospective study, we reviewed 614 patients who were evaluated in our pre-operative clinic (IMPACT clinic) and had stress test within 90 days of evaluation. Functional capacity in METs and stress test results were obtained from electronic records. Patients have been divided into ‘good’ and ‘poor’ functional capacity (FC) groups based on patients’ capacity to do more than 4 METs. Revised cardiac risk index (RCRI) was calculated using clinical risk factors. Patients were divided into risk groups based on RCRI. We used chi-square test to compare functional capacity and stress test results.
Results: 84% of patients underwent intermediate risk surgery. 82% of patients had functional capacity of more than 4 METS. 24.8% of patients with ‘poor FC’ had reversible ischemia in stress test, but 14.3% with ‘good FC’ had reversible ischemia as well (p=0.023). When patients with intermediate (1-2 risk factors) and high risk groups (≥ 3 risk factors) are considered, reversible ischemia was present in 12.9% and 22.5% of patients respectively even if they had good functional capacity (> 4 METs). This shows very high number of patients with good functional capacity may have reversible ischemia.
Conclusion: Functional capacity by history may not be a reliable predictor in pre-operative cardiac risk assessment as lot of patients may have undiagnosed cardiac ischemia. This may be more relevant in patients with multiple clinical risk factors. Further studies are warranted before final conclusions can be made.
- © 2013 by American Heart Association, Inc.