COPD and stiff arteries

COPD is increasingly prevalent, and an increasingly common cause of death. It is currently the fourth leading cause of death in the USA. Patients with COPD often die of other diseases, such as cardiac disease - which is currently the leading cause of death in that country and ours. In the last 10 years there has been increasing recognition that COPD is a disease with systemic effects, beyond the lungs. Death from ischaemic heart disease has been associated with lowered FEV1 (a fivefold in death from AMI as FEV1 fell from 109 to 88% of predicted in a US population). However, establishing how COPD may be a discrete risk factor in cardiovascular disease, distinct from the common risk factor of cigarette smoking, is proving difficult.

A paper in the September 15th edition of the AJRCCM (180 pp513-520) has shed some light on this subject, and scored an accompanying editorial. In this study 18 men with COPD were matched (smoking history and age) with 17 controls who did not have COPD. Pulse wave velocity and pulse wave analysis at carotid, radial and femoral arteries indicate significantly increased arterial stiffness in the subjects with COPD. A complicated array of tests of endothelial function did not indicate any difference between the groups.

Central arterial stiffness is, according to the article and the editorial, a predictor of cardiovascular mortality. It is usually due to either smooth muscle or endothelial dysfunction or elastin loss - or a combination of all three. Given the equivalent endothelial function between the groups in this study, the authors surmised that COPD may lead to elastin degradation in arterial walls. This may be a means by which COPD leads to increased cardiovascular risk independent of other risk factors.

Other studies have suggested that there is endothelial dysfunction in COPD, and that it is worse in patients with lower FEV1 or more extensive emphysema - evidence which is not in agreement with that presented in the recent study. Obviously more work - much more work -needs to be done (I hate hearing that line at conferences, but there it is!)

Anyway, the most tantalising part of the picture is the question of clinical relevance. All of this cardiovascular science is news to me, but it turns out that simvastatin has been shown to reduce arterial stiffness in patients with rheumatoid arthritis. There is also some evidence that statins reduce lung parenchymal destruction and pulmonary vascular remodelling in smoking-related lung disease. So although this is far from being evidence based medicine, we might have some reason to anticipate statins becoming part of routine respiratory medicine in the future.

Andrew