In order to evaluate the usefulness of echocardiography in detection and characterization of pulmonary arterial hypertension (PAH) in scleroderma patients, we performed M-mode, two-dimensional, and Doppler echocardiography in 71 patients with progressive systemic sclerosis (PSS) and related syndromes: mixed connective tissue disease (MCTD) and overlap syndromes. We estimated systolic pressure gradients across the tricuspid valve from the peak velocity of tricuspid regurgitation (TR) by color-flow guided continuous wave Doppler. TR velocities of analyzable quality for gradient estimation were obtained in 28 patients (39%), of whom 12 showed PAH (peak TR velocity > or = 2.5 m/sec). In comparison, analyzable TR was recorded in 19 (35%) of 55 patients with left-sided cardiac disease. None of the 12 with Doppler-estimated PAH showed left ventricular dilatation or decreased fractional shortening by M-mode and two-dimensional measurements. Nonsimultaneous cardiac catheterization confirmed PAH in 8 of 9 with Doppler-estimated PAH and in 3 of 12 without analyzable TR who had hemodynamic study. Doppler-estimated right ventricular systolic pressures (RVSP) correlated well with catheterization-measured pulmonary arterial systolic pressures (PASP) (< 0.01). Our results indicate that Doppler echocardiography is useful in detecting subclinical PAH and estimating PASP in patients with collagen vascular disease. The results of pulmonary function studies suggest that PAH in MCTD is mainly caused by pulmonary vasculopathy.