We studied the influence of bathing on cardiac function and hemodynamics in patients with myocardial infarction (MI) using Swan-Ganz catheter, and using Doppler echocardiography noninvasive indices to assess the increase in pulmonary arterial pressure or pulmonary capillary wedge pressure during bathing were also studied. Fifty-four patients with MI (mean age 56.0 years) were examined (19 with extensive anterior MI, 13 with anterior, 17 with inferior and 5 with anterior and inferior MI). Bathing was conducted with patient in the supine position using tap water at 42 degrees C for 5 min in the Hubbard tank. The patients were classified into 2 groups; one with an increase in the pulmonary capillary wedge pressure (delta PCWP) above 10 mmHg (Group A), and the other with pressure below 10 mmHg (Group B). The hemodynamic data and echocardiographic indices such as peak velocities of blood flow (PV) at the right and left ventricular outflow tracts (RVOT and LVOT) and blood flow pattern at the left ventricular inflow tract (LVIT) were compared between these 2 groups using Doppler echocardiography. In Group A, extensive anterior MI was more frequent (p < 0.05). The exercise duration time was significantly short (6.3 +/- 1.6 min vs 10.2 +/- 2.8 min, p < 0.001) in the exercise tolerance test by bicycle ergometer. The left ventricular end-diastolic pressure was significantly high (17.8 +/- 8.2 mmHg vs 14.8 +/- 4.4 mmHg, p < 0.05) and the left ventricular ejection fraction was lower (39.8 +/- 19.6% vs 56.2 +/- 16.8%, p < 0.01) in cardiac catheterization. This indicated that they had cardiac dysfunction. In Group A, there were marked increases in pulmonary arterial pressure and right atrial pressure during bathing. PV at the RVOT was significantly increased in both Groups A and B (110.3 +/- 5.8%, 112.7 +/- 11.8%, both, p < 0.001). The ratio between 2 peak velocities (A and R) (A/R) at the LVIT in Group A was significantly increased compared with Group B (110.0 +/- 24.5% vs 98.1 +/- 14.5%, p < 0.01), while PV at the LVOT decreased significantly in Group A (92.0 +/- 14.6%, p < 0.01) and increased in Group B (115.0 +/- 17.7%, p < 0.001).(ABSTRACT TRUNCATED AT 400 WORDS)