Impact of renal dysfunction on acute coronary syndrome evaluation in observation unit patients

Objectives: The impact of renal disease on risk stratification of patients at low risk for potential acute coronary syndrome has not been well defined. The objective of this study was to document the prevalence of renal dysfunction and assess the association between renal impairment and abnormal cardiac evaluation in observation unit (OU) patients. Methods: Retrospective cohort study at an academic medical center OU. Data were abstracted using predetermined definitions of data outcomes by trained abstractors. Patients had symptoms consistent with acute coronary syndrome and did not have obvious evidence of acute MI or ischemia on electrocardiogram, unstable vital signs, abnormal cardiac markers, serious arrhythmias, or uncontrollable chest pain. Observation patients received serial cardiac markers and electrocardiograms, with the majority receiving stress testing at treating physician discretion. Patients were stratified by glomerular filtration rates (GFR) at cut-off points of less than 60 and less than 90 mL/min per 1.73 m². Odds ratios were calculated for stress test findings of inducible ischemia or hospital admission. Results: Five hundred and twenty-nine out of 545 patients had complete data and were enrolled. Sixty-nine (13%) patients had a GFR of less than 60 and 300 (56%) patients had a GFR of less than 90. An abnormal cardiac evaluation was found in 64 (12%) patients, of whom 31 (49%) had some renal impairment. The odds ratio of an abnormal cardiac evaluation with a GFR of less than 90 is 1.65 (95% confidence interval, 0.95-2.88) and 1.65 (95% confidence interval, 0.83-3.28) for GFR less than 60. Conclusions: Renal dysfunction is common in OU patients. In these patients, renal dysfunction did not confer higher risk for abnormal cardiac evaluation.