[Late diastolic mitral regurgitation: pulsed Doppler echocardiographic study]

Since the description of late diastolic mitral regurgitation (MR) detected by left ventriculography, the risk of overestimating systolic MR has been pointed out. However, it has not been well studied by pulsed Doppler echocardiography, though this method is thought to be extremely useful to analyze systolic MR. The purpose of this study was to evaluate the usefulness of pulsed Doppler echocardiography in assessing late diastolic MR and to clarify the pathophysiology of this MR. With the probe in the apical position, the blood flow pattern at the left atrial outflow tract was investigated in 226 consecutive cases who underwent left ventriculography. Late diastolic MR, which could not be attributed to ventricular premature contraction, was observed in 10 cases (4.4%) by left ventriculography. Meanwhile, by pulsed Doppler echocardiography, late diastolic disturbed flow directing towards the left atrial cavity in late diastole was detected in 15 cases (6.6%) including 10 cases with positive left ventriculographic MR. Among these 15 cases, 14 (93%) had atrial fibrillation and exhibited this MR only in the cardiac cycle with prolonged R-R intervals. The limitation in number of cardiac cycles which could be analyzed and the rapid heart rate eliminating the appearance of the beat with prolonged R-R intervals may be the reasons for the paucity of late diastolic MR by left ventriculography. Ten cases (66%) of late diastolic MR, including one with sinus rhythm, had aortic regurgitation, three cases showed high-grade systolic MR, and two had atrial septal defect. The simultaneous recording of pulmonary arterial wedge pressure and left ventricular pressure in three patients show a reversal of pressure gradient across the mitral valve in late diastole when the R-R interval was prolonged. In conclusion, pulsed Doppler echocardiography is useful in detecting late diastolic MR, and in reducing overestimates of systolic MR by ventriculography which was induced by erroneous addition of late diastolic MR, because Doppler method has better time resolution in phase analysis. We believe that incomplete premature mitral valve closure caused by a delay in left ventricular contraction following prolonged R-R intervals, and the reversal of left atrial-left ventricular pressure gradient induced by left ventricular over-filling played important roles in the occurrence of late diastolic MR.