Diastolic Mitral Regurgitation
A67-year-old man underwent transthoracic echocardiography for the evaluation of heart failure. The echocardiographic examination demonstrated significant dilatation of all cardiac chambers with marked global left ventricular (LV) systolic dysfunction (LV ejection fraction of 10% to 15%). Color flow imaging revealed a mild-to-moderate degree of mitral regurgitation (MR). Diastolic as well as systolic MR was detected by multiple Doppler modalities (Figures 1 to 3⇓⇓⇓). Diastolic MR resulted from the combination of first-degree atrioventricular (AV) block and severe elevation of LV filling pressures.
Effective ventricular contraction is mandatory for complete mitral valve closure. Diastolic MR is commonly observed during AV block of any degree, when atrial contraction is not followed by adequately synchronized LV contraction. Under these conditions, the AV pressure gradient reverses during atrial relaxation (ventricular pressures higher than atrial), resulting in diastolic MR in the presence of an incompletely closed mitral valve. Diastolic MR in the absence of AV block may occur secondary to significant elevation of LV end-diastolic filling pressures in the presence of restrictive ventric-ular hemodynamics or severe aortic regurgitation, primarily acute regurgitation. Diastolic tricuspid regurgitation, which commonly accompanies diastolic MR, may result from similar right-sided pathophysiological mechanisms.
Diastolic MR has not been studied quantitatively. As a result of the low diastolic ventriculoatrial pressure gradient, diastolic regurgitant volume is probably small, despite a potentially large regurgitant orifice of the incompletely closed mitral valve. Diastolic MR due to AV block is, in general, a benign phenomenon devoid of diagnostic or therapeutic clinical implications. However, the presence of diastolic MR in patients with significant LV dysfunction (systolic and diastolic dysfunction), as in the patient described, highlights the significance of adequately timed AV synchrony in optimal diastolic filling of the failing ventricle. In the presence of first-degree AV block and severe LV dysfunction, dual-chamber pacing at a shorter AV interval may improve LV filling dynamics by optimization of mechanical atrial and ventricular synchrony, prolongation of the effective LV diastolic filling period, and elimination of diastolic MR. The combination of these effects may lower LV filling pressures and elevate cardiac output, thus offering an additional therapeutic option in a subset of patients with severe LV dysfunction.
The editor of Images in Cardiovascular Medicine is Hugh A. McAllister, Jr, MD, Chief, Department of Pathology, St Luke’s Episcopal Hospital and Texas Heart Institute, and Clinical Professor of Pathology, University of Texas Medical School and Baylor College of Medicine.
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