LAUSR

BACKGROUND There is a growing interest in exploring the concept of right ventricular functional reserve in patients with pulmonary arterial hypertension. However, it is still unclear how it should be assessed. Aim of the study was to investigate the determinants of the changes in cardiac output and in pulmonary pressure during dobutamine stress echocardiography in pulmonary arterial hypertension. METHODS Low-dose dobutamine stress echocardiography was performed in 55 patients and 28 controls. Tricuspid annular plane systolic excursion, its ratio to systolic pulmonary artery pressure, right ventricular area change, degree of tricuspid regurgitation, right ventricular end-systolic pressure-area ratio, cardiac output were assessed at rest and at peak stress. RESULTS According to the stress induced increase in cardiac output, patients were classified into 2 groups: above/equal to the median of 2.8 L/min (high cardiac output) or below the median (low cardiac output). High cardiac output patients were characterized by a greater increase in heart rate (+45.1 ± 17.5 vs +21.3 ± 17.7 bpm), a greater improvement in tricuspid annular plane systolic excursion (+4.2 ± 3.3 vs +1.9 ± 2.6 mm, P = 0.005) and a decrease in tricuspid regurgitation (P = 0.010) as compared to low cardiac output patients. Changes in pulmonary pressure were not associated with changes in indicators of right ventricular function but only with changes in heart rate. CONCLUSIONS The increase in cardiac output during dobutamine is associated with an improvement in longitudinal right ventricular function, a decrease in tricuspid regurgitation and an increase in heart rate. Changes in pulmonary pressure only reflect the changes in heart rate.