Late diastolic mitral regurgitation studied by pulsed Doppler echocardiography. 
To evaluate the usefulness of pulsed Doppler echocardiography in assessing late diastolic mitral regurgitation (MR) and to clarify the pathophysiology of MR, 226 consecutive patients who had undergone left ventriculography were studied.  By investigating blood flow patterns at the left atrial outflow tract, late diastolic disturbed flow suggesting MR was detected in 15 patients (7%), including 10 (4%) with positive left ventriculographic findings.  Among these 15 patients, 14 (93%) had atrial fibrillation and had late diastolic MR in the cardiac cycle with prolonged RR interval.  The limitation in number of cardiac cycles that could be analyzed and the rapid heart rate eliminating appearance of the beat with prolonged RR interval may be the reasons for the paucity of late diastolic MR by left ventriculography.  Ten patients (66%) with late diastolic MR, including 1 with sinus rhythm, had aortic regurgitation, 3 had high-grade systolic MR and 2 had atrial septal defect.  Simultaneous recording of pulmonary artery wedge pressure and left ventricular pressure in 3 patients showed a reversal of pressure gradient in late diastole when the RR interval was prolonged.  In conclusion, pulsed Doppler echocardiography was useful for detecting late diastolic MR and in reducing overestimation of systolic MR in left ventriculography induced by erroneous addition of late diastolic MR.  The difference of the incidence of this flow between left ventriculography and Doppler examination indicated that this flow depends primarily on heart rate and may come and go in a patient.