Rahul K. Khare, MD Institute for Healthcare Studies Department of Emergency Medicine

1. Sixty-Four-Slice Computed Tomography of the Coronary Arteries: Cost-Effectiveness Analysis of Patients Presenting to the ED with Low Risk Chest Pain Rahul K. Khare, MD Institute for Healthcare Studies Department of Emergency Medicine Feinberg School of Medicine Northwestern University rkhare@northwestern.edu

3. Chest Pain In the Emergency Department • “Chest Pain” • Most common Emergency Department diagnosis in patients 50 years or older • Over 50% will not be diagnosed with coronary artery disease • The identification of chest pain patients with significant coronary artery disease remains a challenge

4. Strategies • One strategy is the use of chest pain observation units (OU) in the ED • EDs have developed OUs to efficiently and safely manage low risk chest pain patients with serial cardiac enzymes and subsequent cardiac stress testing • There is still a significant cost and time investment involved

5. Current Management of Low-Risk Chest Pain in the ED • 54 year old male complains of chest pain • Patient smokes & has high blood pressure • ED course • Near normal ECG • First cardiac enzymes are within normal • He is now chest pain free

6. Current Strategy • 7.7% of missed myocardial infarctions die • You cannot send this patient home • Admit to the observation unit • Continuous telemetry monitoring • Serial cardiac enzymes • Either a stress echo or stress ECG

7. New Potential Management • 64-slice multidetector computed tomography of the coronary arteries (MDCT) - new modality for evaluation of CAD • Some advocate use of MDCT in the ED for low risk chest pain patients as an alternative to Observation Unit and stress testing. • Not current standard of care in the ED setting

8. Rationale • MDCT may become a first-line screening instrument for detecting significant CAD in low risk patients presenting to the ED with chest pain • It is unclear whether the increased cost of the MDCT test is associated with better patient outcomes

9. Objective • To estimate the cost-effectiveness of MDCT in the ED compared to the current standard of care for the evaluation of low risk chest pain patients presenting to the ED

10. Study Design • Decision analytic model • Compare the health outcomes and costs that result from different risk-stratification strategies for ED patients with low risk chest pain

11. Population • 54 year old male, low risk chest pain • Reflects the average age and most prevalent gender • 3 Scenarios • 1) OU care followed by stress ECG testing • 2) OU care followed by stress echocardiography • 3) No OU care, MDCT done in ED

13. OU + Stress Echo Tree

14. MDCT Tree

17. Healthcare Costs • All costs were adjusted to 2007 U.S. dollars using the Medical Care component of the Consumer Price Index. • No discounting was necessary as costs and cost-effectiveness were examined for a 30-day period after adjustment to 2007 dollars.

18. Sensitivity Analysis • Test robustness of the results to changes in model assumptions and estimates • Threshold sensitivity analysis • To determine at which point these input parameters resulted in a substantial impact on cost, effectiveness, or cost-effectiveness of each modality

19. Probabilistic Sensitivity Analysis • Conducted a Monte Carlo analysis to evaluate uncertainty by varying all of the input model variables simultaneously to assess the overall variability of the model • Each scenario was simulated 10,000 times using Monte Carlo simulation • This method accounts for variability among individuals and tests, which more closely resembles reality. The 95% confidence intervals of the ICERs were determined

20. Results Dominant: Less Costly, More Effective

21. Sensitivity Analysis • MDCT remained dominant to the other strategies because it had better outcomes and lower costs • Five input parameters that resulted in the MDCT having higher costs than OU + Stress Echo • cost of MDCT > $2,097 Base case ($1500) • cost of OU care < $1,092 Base case ($1712) • prevalence of CAD > 70% Base case (6%) • specificity MDCT < 65% Base case (84%) • indeterminate rate MDCT > 30% (3.8%)

22. Limitations • Our analysis relies heavily on published assessments • We use sensitivity and specificity of the MDCT from of studies with a CAD prevalence of 64%. • All input parameters taken from the literature may be over- or understated in this low risk OU population • Radiation from a 64-slice scanner evaluating the coronary arteries has a lifetime risk of cancer • Patients who have significant CAD on MDCT do need to get another catheterization. • This requires another dye load, renal pathology is not modeled

23. Conclusions • MDCT strategy is less costly and more effective than both OU based strategies in chest pain patients presenting to the ED • Largely due to the diagnostic test performance of MDCT and the avoidance of OU costs