Intravenous fluid loading is commonly used for the treatment of low cardiac output (CO) syndrome complicating severe right ventricular infarction (RVMI). We prospectively evaluated the effectiveness of this method in 11 consecutive patients (age 66 +/- 14 years) with severe RVMI, using a newer thermodilution method with rapid response thermistors. Volume loading was performed until pulmonary wedge pressure (PWP) reached 18 to 24 mmHg. Right atrial pressure (RAP), pressures of the right ventricle (RV) and pulmonary artery (PA), PWP, RV volumes, RV ejection fraction (RVEF), stroke volume (SV), CO, pulmonary vascular resistance (PVR) and RAP/PWP ratio were measured before and after volume loading. RAP rose from 12 +/- 4 to 19 +/- 5 mmHg (P < 0.0001) and its tracing showed a non-compliant pattern in all patients. RV end-diastolic pressure rose from 13 +/- 4 to 20 +/- 5 mmHg (P < 0.0001) and PWP from 14 +/- 3 to 20 +/- 6 mmHg (P < 0.0001). Mean PA pressure rose from 20 +/- 3 to reach 25 +/- 6 mmHg (P < 0.001), while PVR did not change significantly (117 +/- 39 vs 101 +/- 49 dyn.s.cm-5, P ns). RAP/PWP ratio rose from 0.85 +/- 0.14 to 1.05 +/- 0.07 (P < 0.01). The end-diastolic RV volume increased from 95 +/- 26 to 113 +/- 24 ml.m-2 (P < 0.001); however, RV end-systolic volume increased from 65 +/- 28 to 83 +/- 29 ml.m-2 (P < 0.01), thus SV did not change significantly (30 +/- 6 vs 30 +/- 8 ml.beat-1.m-2, P ns). RVEF decreased from 32 +/- 11 to 28 +/- 11% (P < 0.001). CO did not improve significantly (2.3 +/- 0.42 vs 2.4 +/- 0.62 l.min-1.m-2, P ns) neither did the clinical status.(ABSTRACT TRUNCATED AT 250 WORDS)