Progressive Dilatation of the Main Pulmonary Artery Is a Characteristic of Pulmonary Arterial Hypertension and Is Not Related to Changes in Pressure

Background Pulmonary artery (PA) dilatation is one of the consequences of pulmonary arterial hypertension (PAH) and is used for noninvasive detection However, it is unclear how the size of the PA behaves over time and whether it is related to pressure changes The aim of this study was to evaluate PA size during follow-up in treated patients with PAH and whether it reflects pulmonary vascular hemodynamics Methods Fifty-one patients with PAH who underwent at least two right-sided heart catheterizations (RHCs) together with cardiac MRI (CMR) were included in this study Another 18 patients who had normal pressure at RHC were included for comparison at baseline From RHC, we derived PA pressures and cardiac output From the CMR images we derived PA diameter (PAD) and the ratio of the PAD and ascending aorta diameter Results The PAD was significantly larger in patients with PAH than in patients without PAH (P < 001) A ratio of the PAD and ascending aorta diameter >1 had a positive predictive value of 92% for PAM Mean follow-up time was 942 days, and there was a significant dilatation during this period (P < 001) The change of the PAD did not correlate with the changes in pressure or cardiac output A moderate correlation with follow-up time was found (r =0 56, P < 001) Conclusions A dilatated PA is useful for identifying patients with PAM However, during patient follow-up, progressive dilatation of the PA is independent of the change m PA pressure and cardiac output and might become independent from hemodynamics CHEST 2010, 138(6) 1395-1401