Patients with pulmonary hypertension are at risk of developing fatal right heart failure after heart transplantation. To evaluate this risk potential, candidates for heart transplantation are screened by measuring rest right heart pressures and the response to nitroprusside. To test the validity of this approach, the influence of pretransplantation right heart catheterization data on outcome after transplantation was analyzed in 293 of 301 consecutive patients. Patients with a pulmonary vascular resistance greater than 2.5 Wood units measured at baseline study had a 3-month mortality rate of 17.9% compared with 6.9% in patients with resistance less than or equal to 2.5 units (p less than 0.02). Patients with a pulmonary vascular resistance greater than 2.5 units at baseline study could be differentiated further according to their hemodynamic response to nitroprusside; those whose resistance could be reduced to less than or equal to 2.5 units with a stable systemic systolic pressure greater than or equal to 85 mm Hg had a 3-month mortality rate of only 3.8%. In contrast, patients whose pulmonary vascular resistance could not be reduced to less than 2.5 units, and those whose resistance could be reduced to less than or equal to 2.5 units but only at the expense of systemic hypotension (systolic pressure less than or equal to 85 mm Hg) had a 3-month mortality rate of 40.6% and 27.5%, respectively. Furthermore, all 10 patients who died of right heart failure belonged to the latter two groups.(ABSTRACT TRUNCATED AT 250 WORDS)