AbstractHigh sensitivity troponin T levels and electrocardiographic signs of myocardial injury in patients with clinically stable chronic obstructive pulmonary disease
Background: Chronic obstructive pulmonary disease (COPD) is a common disease worldwide. Smoking is the most important risk factor for developing COPD, and most COPD patients are current or former smokers. Thus, this patient population has an increased likelihood of developing other smoking-related diseases like ischemic heart disease, a common cause of death among COPD patients. We hypothesized that non-hospitalized subjects with stable COPD have a higher prevalence of myocardial injury, assessed by the Cardiac Infarction Injury Score (CIIS), than non-COPD subject. In addition we hypothesized that stable COPD patients have higher levels of the myocardial necrosis marker, cardiac troponin T (cTnT), measured by a new high-sensitive (hs) assay, than control subjects.Methods and material: 30,000 individuals, 30-65 years of age, were invited to join The Akershus Sleep Apnea Project (ASAP). Among these, 541 subjects had physical exams, electrocardiograms, and blood samples drawn. Hs-TnT was measured in 525 patients. CIIS was scored manually in 51 subjects (17 COPD cases and 34 control subjects) included in the current analysis. COPD was defined as FEV1% <70 and 40 years of age. Four of these had known coronary artery disease (CAD). The non-COPD group consisted of 34 subjects: FEV1%> 70; >40 years of age; lack of CAD and at least ten years of smoking. We studied the differences in CIIS-scores and hs-cTnT levels between the COPD (n=17) and the non-COPD (n=34) patients. The differences in hs-cTnT levels between the COPD group and the remaining participants (n=508) were also evaluated. Results: Mean age of the whole study population was 48.4 years, and 45.5 % were female. 10.4% had a history of prior myocardial infarction, percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG). Among the subjects drawn for CIIS-scoring (n=51), the mean age was 52.0 years and 49.0 % were female. Five had known COPD, whereas 17 had COPD shown by FEV1 % < 70. Among the 525 subjects in whom hs-cTnT was available, 56, 2% had levels below the detection limit (<3 ng/L). Hs-cTnT was significantly higher in stable COPD subjects (n=17) than in non-COPD subjects (n=508; p=0.029). This difference remained significant after the 4 subjects with a history of CAD were excluded from the analysis (p=0.019). In the subset of subjects with CIIS values available, COPD subjects (n=17) had higher hs-cTnT values than control subjects (n=34) (9.17ng/L (±11.0) vs. 2.78ng/L (±4.38); p=0.033). Again, after exclusion of the 4 patients with prior CAD, the difference remained significant (p=0.026). Both Pearson correlation (r=0.374, p=0.007) and Spearman`s rho (r=0.476, p=<0001) showed positive correlation between hs-cTnT and age. The mean (SD) CIIS score in the two groups were 14.62 points (±14.47) in the case group and 10.16 points (±7.10) in the control group (p=0.24).Conclusions: We found that stable COPD patients have higher levels of troponin T, shown by the high-sensitive assay, compared to both the control group and the remaining participants. There was no significant difference in CIIS-score between the COPD and control group.