EVIDENCE OF ISCHEMIC HEART DISEASE AMONG CHRONIC LUNG DISEASE PATIENTS ATTENDING A PULMONARY REHABILITATION PROGRAM

Abstract

Ischemic heart disease (IHD) has emerged as a contributor to morbidity and mortality in individuals with chronic lung diseases (CLD). There is also evidence that IHD, in particular myocardial infarction (MI), remains commonly unrecognized and/or undiagnosed in this population. This is an important observation because IHD requires precautionary measures during pulmonary rehabilitation program (PRP) in order to ensure participants’ safety and training effectiveness. The purpose of this study is (1) to determine the Cardiac Infarction Injury Score (CIIS) in CLD patients attending a PRP, and (2) to investigate the association between CIIS, history of MI, and functional capacity (6 minute walk distance test) in this population. A retrospective chart review study was conducted in a population of consecutive CLD patients that were enrolled in a comprehensive PRP at the St. Paul’s Hospital during 2009-2013. Subjects with normal sinus rhythm on resting ECGs, recorded prior to a cardiopulmonary exercise test, were included in the analysis. Twelve ECG features were converted to a score according to the CIIS algorithm, and a CIIS greater than 20 was used to discriminate between the presence and absence of past MI. Pulmonary rehabilitation outcomes were retrieved from the patients’ medical records along with confirmed MI diagnosis. 114 patients with CLD attending a PRP between 2009 and 2013 were identified in the St Paul’s Hospital database. A total of 47 patients with a mean age of 64.6±10.3 years (53% males) met the eligibility criteria. 19 patients (40%) had restrictive lung disease (FVC% predicted 66.8±10.2; FEV1/FVC% predicted 94.6 ±10.3) and 28 patients (60%) had obstructive lung disease (FEV1% predicted 47.6±12.0; FEV1/FVC% predicted 56.5±10.7). The overall mean CIIS was 14.0±8.9 with a lower (nonsignificant) CIIS in the restrictive group (12.1±9.4) compared to the obstructive group (15.3±8.4). 14 patients (30%) had a CIIS ≥ 20, out of whom only three (6%) had a recognized history of MI. CIIS was significantly and negatively correlated with 6 minute walk distance test (6MWD) in both restrictive (r = -0.5; p = 0.02) and obstructive group (r = -0.4; p = 0.04), respectively. Unrecognized ischemic heart disease is not negligible among CLD patients attending PRP, and a higher cardiac infarction injury score is associated with a lower functional capacity in this population. More research is needed to explore the potential of PRP to prevent IHD in CLD patients.