Severe chronic obstructive pulmonary disease leads to cor pulmonale , characterised by elevated pulmonary vascular resistance and secondary reductions in left ventricular filling, stroke volume, and cardiac output.  However, whether similar changes occur in more moderate emphysematous disease is unknown.  In order to investigate this question the authors of this papar studied 2816 people between the age of 45 to 84 years who are enrolled in the large scale prospective population based cohort study, MESA (The Multi-Ethnic Study of Atherosclerosis), designed to examine the prevalence, correlates and progression of sub-clinical cardiovascular disease in a multi-ethnic North American population with no history of clinical cardiovascular disease.

Left ventricular structure and function were assessed using 1.5T cardiac MRI and correlated with percent emphysema seen on the lung windows of cardiac CT scans.  In addition, all subjects underwent spirometry to test lung function.  The results demonstrated a linear association between emphysema severity and a variety of ventricular measures; a 10 percentage-point increase in emphysema, for example, showed highly significant correlations with LV end-diastolic volume (-4.1ml; P<0.001), stroke volume (-2.7ml; P<0.001) and cardiac output (-0.19 litres per min; P<0.001).  These associations were stronger for current and former smokers but also held true for those who had never smoked, suggesting a true effect of pulmonary emphysema on cardiac function rather than a sub-clinical effect of smoking.  The extent of airflow obstruction on spirometry was similarly associated with LV structure and function but there was no effect of either of these parameters on LV ejection fraction.

The study was unable to shed light on the mechanisms behind its main finding but speculates that it may be due to changes in the pulmonary circulation and endothelial function leading to reduced LV filling.  It provides a powerful insight into the interaction between the pulmonary and vascular systems and demonstrates that even seemingly minor perturbations in one sphere may have consequential effects on ostensibly disparate physiological systems.

Conclusions:

Increasing emphysema was linearly related to impaired left ventricular filling, reduced stroke volume, and lower cardiac output – without changes in ejection fraction.  These findings were seen even in early stage emphysema.

• Barr RG, Bluemke DA, Ahmed FS, Carr JJ, Enright PL, Hoffman EA, Jiang R, Kawut SM, Kronmal RA, Lima JA, Shahar E, Smith LJ and Watson KE.  Percent Emphysema, Airflow Obstruction, and Impaired Left Ventricular Filling N Engl J Med. 2010 Jan 21;362(3):217-27.