Background: Low risk patients with suspected coronary ischemic syndrome (CIS) undergo hospital procedures despite unclear benefit. False negative evaluations can contribute to unnecessary testing that increases cost. This analysis stratified the likelihood of non-obstructive disease at time of coronary angiography (CA) to determine predictors of a negative study and assessed subsequent costs resulting from negative CA.
Methods: 564 coronary angiograms were performed during 2013 at a single institution. Patients with ST-segment elevation myocardial infarction, cardiac arrest, multiple angiograms, or a clear non-CIS indication for CA (i.e. pre valve surgery) were excluded. 171 patients were included for retrospective chart review and categorized by age, race, gender, body mass index, blood pressure, chest pain quality, biomarker elevation, electrocardiographic findings, and clinical features that include hypertension, lipid status, diabetes, chronic kidney disease, psychiatric disease and substance abuse. These data were then analyzed by univariate assessment and logistic regression models for the multivariate predictors of factors associated with negative CA. Cost analysis was performed using a consumer based average cost database and direct hospital laboratory expense data.
Results: Of the 171 patients studied, nearly half (47%) did not have obstructive coronary artery disease. The adjusted odds of negative CA were significantly elevated, in order of predictability, with the absence of chest pain (odds ratio (OR) 7.28, p = 0.0004), atypical chest pain (OR 7.13, p < 0.0001), African American race (OR 4.87, p = 0.0033), no diabetes (OR 4.25, p = 0.0026), female gender (OR 3.70, p = 0.0038), normal Troponin-I level (OR 3.16, p = 0.0208), no hyperlipidemia (OR 2.96, p = 0.0107), and low troponin level 0.033 - 0.1 ng/mL (OR 2.96, p = 0.0025). The total cost of negative CA was $749,088, or $9,363 per patient. Total avoidable direct catheterization laboratory expense was $251,000, or $3,137 per patient.
Conclusion: In the evaluation of CIS, a large number of patients that undergo CA have no evidence of obstructive disease. Further study of characteristics that predict the absence of obstructive disease would help reduce the frequency and substantial cost of unnecessary invasive procedures.