To study the relationship between the hemodynamic characteristics and prognosis in PPH, we analyzed the data on patients whose prognosis was well documented from the time of hemodynamic monitoring. Our subjects were 87 patients obtained from a nationwide survey in Japan. PCWPs were obtained in 44 patients and COs were measured in 59 patients. The average age was 33 years (range 14 to 69). Patients were followed prospectively for up to 100 months and were categorized based on the survival period from the time of catheterization. Hemodynamic variables that showed significant differences or prognostic trends were RVedp, pulmonary artery diastolic pressure, PCWP, CI, PVR, and PVR/SVR ratio. The CI correlated with the number of survival months (r = 0.583; p less than 0.01). The hemodynamic state of patients who died suddenly within 1 year from the time of catheterization was no different from those who died of clinical right-sided heart failure. The partial pressure of oxygen of arterial blood was the only variable discriminating sudden deaths from right-sided heart failure deaths (54 +/- 2 vs 66 +/- 4 mm Hg; p less than 0.05). The results of this study indicate that the major determinant of prognosis is right ventricular function and that the CI might be used as a prognostic indicator. In addition, sudden death is more likely to occur in patients with severe hypoxia.