Left ventricular filling may be studied non-invasively by Doppler echocardiographic recording of transmitral blood flow. This study reports the variations in this flow induced by changing cardiac preload by administering trinitrin or by vascular filling in 27 patients undergoing catheterisation. Left ventricular end diastolic pressure (LVEDP) was measured by the pig-tail catheter used for ventriculography. Transmitral flow was recorded by pulsed Doppler using the apical view. The parameters studied were those of the early diastolic E wave and the end diastolic A wave. The hemodynamic and echocardiographic measurements were performed under basal conditions, after trinitrin and after vascular filling. Trinitrin was given to 14 patients and led to a fall in LVEDP from 17.6 +/- 4.5 to 6.7 +/- 1.4 mmHg (p less than 0.001). The amplitude of the mitral E wave decreased and the E/A ratio fell from 0.93 +/- 0.37 to 0.71 +/- 0.32 (p less than 0.001). Thirteen patients underwent vascular filling which increased LVEDP from 10.9 +/- 5 to 27 +/- 4 mmHg (p less than 0.001). The mitral E wave increased and the E/A ratio rose from 0.96 +/- 0.32 to 1.27 +/- 0.23 (p less than 0.01). The patients received trinitrin and then underwent vascular filling. The LVEDP decreased from 16 +/- 3.9 to 8 +/- 2.9 mmHg (p less than 0.001) and then rose to 28.3 +/- 3.5 mmHg (p less than 0.001). The E/A ratio fell after trinitrin from 0.91 +/- 0.40 to 0.58 +/- 0.30 (p less than 0.01) and then rose to 1.42 +/- 0.60 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)