CLINICAL STUDIES
Effects of afterload reduction on vena contracta width in mitral regurgitation
Ali M. Kizilbash, MDa,
DuWayne L. Willett, MD, FACCa,
M. Elizabeth Brickner, MD, FACCa,
Sheila K. Heinle, MD, FACCa and
Paul A. Grayburn, MD, FACCa
a Department of Internal Medicine, Division of Cardiology, University of Texas Southwestern Medical Center and Department of Veterans Affairs Medical Center, Dallas, Texas, USA
Manuscript received January 6, 1998;
revised manuscript received March 27, 1998,
accepted April 17, 1998.
Address for correspondence: Paul A. Grayburn, MD, Division of Cardiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75235-9047 grayburn{at}ryburn.swmed.edu
Objectives. We used color Doppler flow mapping to determine whether vena contracta width (VCW) is a load-independent measure of the severity of mitral regurgitation.
Background. VCW has been proposed to be a relatively load-independent measure of mitral regurgitation severity in flow models using a fixed orifice. However, in patients with mitral regurgitation, VCW may not be load independent because of a dynamic regurgitant orifice.
Methods. VCW, effective regurgitant orifice area and regurgitant volume were measured by quantitative Doppler mapping in 31 patients with chronic mitral regurgitation at baseline and during nitroprusside infusion. Patients with rheumatic heart disease, annular calcification or endocarditis were considered to have a fixed regurgitant orifice, whereas patients with mitral valve prolapse, dilated cardiomyopathy or ischemia were considered to have a dynamic regurgitant orifice.
Results. Systolic blood pressure (148 ± 27 to 115 ± 25 mm Hg) and end-systolic wall stress (121 ± 50 to 89 ± 36) decreased with nitroprusside (p < 0.05). Although nitroprusside did not significantly change mean values for VCW (0.5 ± 0.2 to 0.5 ± 0.2 cm), regurgitant volume (69 ± 47 to 69 ± 56 ml) or effective regurgitant orifice area (0.5 ± 0.4 to 0.5 ± 0.6 cm2), individual patients exhibited marked directional variability. Specifically, VCW decreased in 16 patients (improved mitral regurgitation), remained unchanged in 7 patients and increased in 8 patients (worsened mitral regurgitation) with nitroprusside. Also, the VCW response to nitroprusside was concordant with changes in effective regurgitant orifice area and regurgitant volume, and was not different between dynamic and fixed orifice groups.
Conclusions. Contrary to the results from in vitro studies, VCW is not load independent in patients with mitral regurgitation caused by dynamic changes in the regurgitant orifice. The origin of mitral regurgitation does not predict accurately whether the regurgitant orifice is fixed or dynamic. Finally, short-term vasodilation with nitroprusside may significantly worsen the severity of mitral regurgitation in some patients.
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Abbreviations and Acronyms
| | BP | = blood pressure | | EROA | = effective regurgitant orifice area | | HR | = heart rate | | MR | = mitral regurgitation | | RgV | = regurgitant volume | | ROA | = regurgitant orifice area | | VCW | = vena contracta width |
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