Cardiac mass and function decrease in bronchiolitis obliterans syndrome after lung transplantation: Relationship to physical activity?

Rationale: There is a need to expand knowledge on cardio-pulmonary pathophysiology of bronchiolitis obliterans syndrome (BOS) following lung transplantation (LTx). Objectives: The purpose of this study was to assess MRI-derived biventricular cardiac mass and function parameters as well as flow hemodynamics in patients with and without BOS after LTx. Methods: Using 1.5T cardiac MRI, measurements of myocardial structure and function as well as measurements of flow in the main pulmonary artery and ascending aorta were performed in 56 lung transplant patients. The patients were dichotomized into two gender matched groups of comparable age range: one with BOS (BOS stages 1-3) and one without BOS (BOS 0/0p). Measurements and Main Results: Significantly lower biventricular cardiac mass, right and left ventricular end-diastolic volume, biventricular stroke volume, flow hemodynamics and significant higher heart rate but preserved cardiac output were observed in patients with BOS 1-3 compared to the BOS 0/0p group (p<0.05). In a stepwise logistic regression analysis global cardiac mass (p50=046) and days after LTx (p50=0001) remained independent parameters to predict BOS. In a second model an indicator for the physical fitness level - walking number of stairs - was added to the logistic regression model. In this second model, time after LTx (p50=005) and physical fitness (p50=01) remained independent predictors for BOS. Conclusion: The observed changes in biventricular cardiac mass and function as well as changes in hemodynamic flow parameters in the pulmonary trunk and ascending aorta are likely attributed to the physical fitness level of patients after lung transplantation, which in turn is strongly related to lung function.