Chronic obstructive pulmonary disease, pulmonary function and cardiovascular disease
McAllister, David Anthony
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Cardiovascular disease is common in Chronic Obstructive Pulmonary Disease (COPD), and forced expiratory volume in one second (FEV1) independently predicts cardiovascular morbidity and mortality. Pathological changes in the systemic vasculature have been proposed as potential mechanisms linking COPD to cardiovascular disease, and patients with COPD may be at increased risk of acute myocardial infarction during acute exacerbations. Notwithstanding causation, FEV1 may be a useful prognostic marker in patients undergoing cardiac surgery. This thesis examined these three aspects of cardiovascular co-morbidity in relation to COPD and FEV1. In 2,241 consecutive cardiac surgery patients, FEV1 was associated with length of hospital stay (p<0.001) and mortality (p<0.001) adjusting for age, sex, height, body mass index, socioeconomic status, smoking, cardiovascular risk factors, chronic pulmonary disease, and type/urgency of surgery. In a survey of Scottish Respiratory Consultants there was no consensus regarding the investigation and management of acute coronary syndrome in exacerbation of COPD. In a case-series of 242 patients with exacerbations 2.5% (95% CI 1.0 to 5.6%) had chest pain, raised serum troponin and serial electrocardiogram changes suggestive of acute coronary syndrome. However, over half reported chest pain, while raised troponin was not associated with chest pain or serial ECG changes. Carotid-radial pulse wave velocity (PWV), aortic distensibility, and aortic calcification were measured to assess the relationship of the systemic vasculature to FEV1 and emphysema severity on CT. In adjusted analyses, emphysema was associated with PWV in patients with COPD (p = 0.006) and, in population based samples, with extent of distal aortic calcification (p=0.02) but not with aortic distensibility (p=0.60). This thesis found that FEV1 was associated with mortality and length of hospital stay in patients undergoing cardiac surgery, and that chest pain and raised troponin were common but unrelated in exacerbation of COPD. In the vascular studies distal but not proximal vascular pathology was associated with FEV1, and if COPD is truly related to systemic arterial disease, the distal arterial tree is implicated.