Underdiagnosis of myocardial infarction in COPD – Cardiac Infarction Injury Score (CIIS) in patients hospitalised for COPD exacerbation

Abstract

Patients with chronic obstructive pulmonary disease (COPD) are usually former or current smokers, and are at increased risk of ischemic heart disease. We used Cardiac Infarction Injury Score (CIIS) to assess the prevalence of prior myocardical infarction (MI) in COPD patients and compared this to clinicians' previous diagnosis of MI. From the hospital database, 897 patients (mean age 70.9 years, 50.8% female) discharged after treatment for COPD exacerbation in the years 2000-2003 were identified. Disease history was established from medical records and the hospital patient database. Electrocardiograms from the day of admission were available in 827 patients, and were coded according to the CIIS algorithm by an investigator blinded to clinical and outcome data. The CIIS score was validated using follow-up data for the first year after discharge. Two hundred and twenty-nine patients had CIIS > or = 20, out of whom only 30% (95% confidence interval: 24-36%, n=68) had a recognised history of MI. Female patients had a lower probability of diagnosis despite ECG evidence. Validation of CIIS using multivariate Cox regression analysis showed that a score > or = 20 had independent prognostic value for the first year after discharge, with an adjusted HR of 1.52 (1.14-2.03). Unrecognised MI is common in patients hospitalised with COPD exacerbation. Less than one-third of patients with ECG evidence of previous MI by the CIIS system actually have the diagnosis in their medical records.