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Ann Thorac Surg 2006;82:735-737
© 2006 The Society of Thoracic Surgeons

Case report

Left Ventricular Outflow Obstruction After Mitral Valve Replacement Preserving Native Anterior Leaflet

Kazuma Okamoto, MD*, Issei Kiso, MD, PhD, Yoshihito Inoue, MD, PhD, Hideki Matayoshi, MD, Ryuichi Takahashi, MD, PhD, Yasuhiro Umezu, MD

Department of Cardiovascular Surgery, Saiseikai Tochigiken Utsunomiya Hospital, Utsunomiya, Tochigi, Japan

Accepted for publication October 10, 2005.

* Address correspondence to Dr Okamoto, Shinanomachi 35, Shinjuku, Tokyo, 160-8582 Japan (Email: kazuma{at}mail.com).


   Abstract
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 Abstract
Introduction
 Comment
 References
 
Left ventricular outflow obstruction may result from preserving the anterior leaflet after mitral valve replacement. A 79-year-old woman, who had a mitral valve replacement with the native mitral leaflets left intact 16 years before, was admitted to our hospital with severe dyspnea due to heart failure. Echocardiography showed systolic anterior motion of preserved anterior mitral leaflet, and continuous wave Doppler detected severe left ventricular outflow tract jets during systole without mitral chordal rupture. Surgical incising of the anterior mitral leaflet through the aortic root relieved the obstruction without removing the prosthetic mitral valve.


   Introduction
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 Abstract
 Introduction
Comment
 References
 
Mitral chordae-sparing procedures in mitral valve replacement have shown good results in maintaining postoperative long-term left ventricular function. However the possibility of complication caused by preserved mitral valve leaflet should not be neglected. We report a rare case of left ventricular outlet tract obstruction by systolic anterior motion of preserved anterior mitral leaflet that occurred 16 years after chordal-sparing mitral valve replacement.

A 79-year-old woman was admitted to our hospital in March 2004, because of suspended dyspnea. Sixteen years earlier she had undergone mitral valve replacement (MVR) with a 25-mm St. Jude Medical prosthesis (St. Paul, MN) due to mitral valve regurgitation by chordal rupture of the posterior mitral leaflet. The native mitral leaflets were preserved along with the mitral apparatus.

Physical examination on admission revealed prominent edema in both legs. A grade IV/VI systolic murmur was audible at the right upper sternal border. The chest roentgenogram showed enlarged cardiac shadow and bilateral massive pleural effusion. The New York Heart Association functional class was IV.

Transesophageal echocardiography and transthoracic echocardiography showed left ventricular outflow tract (LVOT) obstruction due to systolic anterior motion (SAM) of the preserved anterior leaflet of the native mitral valve (Figs 1A–1C). Left ventricular function was moderately depressed (ejection fraction, 47%). Continuous wave Doppler detected significant systolic LVOT jets as 6.1 m/s. The chordae of the anterior mitral leaflet (AML) were not ruptured. The function and position of the prosthetic mitral valve were normal. Aortic valve stenosis was not significant with only trivial aortic regurgitation. A cardiac catheterization showed that the pressure gradient between the left ventricle and the aorta was 129 mm Hg. Despite medical treatment with diuretics, dobutamine, and caripeptide, heart failure did not get better. She had undergone a re-do mitral valve operation for eliminating LVOT obstruction on the 19th hospital date.


Figure 1
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  		Fig 1. (A) The transthoracic echocardiography and (B) the M-mode echocardiography showed left ventricular outflow tract obstruction due to (C) systolic anterior motion of the preserved anterior leaflet of native mitral valve. (AML = anterior mitral leaflet.)

 
Cardiopulmonary bypass was established using single venous cannula and antegrade warm blood cardioplegia was infused through the ascending aorta. The ascending aorta was opened with oblique incision, and intracardiac apparatus was observed via the aortic valve. The mitral prosthesis was normally positioned and its function was good. The chordae of the AML were not ruptured, however the AML could move freely to the LVOT. The native redundant AML was cut off across the aortic valve. The mitral apparatus including chordae of the AML and papillary muscles were preserved. The prosthetic mitral valve was not replaced. Cardiopulmonary bypass was weaned without difficulties using low-dose catecholamine. The postoperative course was uneventful. One week after surgery transthoracic echocardiography showed preserved left ventricular wall motion, pressure gradient in the LVOT was within physiologic ranges, and there was normal functioning of the mitral prosthesis and native aortic valve. Six months after surgery the patient is doing well with cardiac function in the New York Heart Association functional class I.


   Comment
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 Abstract
 Introduction
 Comment
References
 
The continuity between mitral annulus and left ventricular wall through leaflets, chordae tendinea, and papillary muscles plays an important role on the left ventricular function [1]. Preservation of the AML and tensor apparatus during MVR is believed to maintain long-term left ventricular function by maintaining an annular–papillary connection that affects left ventricular torsional deformation. It also reduces left ventricular chamber size and systolic afterload compared with the conventional procedure of excising the entire subvalvular apparatus or the procedure with preservation of only the posterior leaflet [2].

However, the danger of LVOT obstruction caused by SAM of preserved AML should not be ignored. Cases in which MVR without resection of AML cause severe LVOT obstruction were reported. Waggoner and colleagues [3] reported that SAM of the native AML, as seen in dynamic LVOT obstruction, was observed in 6 of 7 patients with the native mitral leaflets left intact. Esper and colleagues [4] also reported a case of LVOT obstruction caused by SAM that had occurred 8 weeks after MVR with anterior and posterior leaflets left untouched. In this case the tensor apparatus seemed positioned quite anteriorly, clearly projecting into the LVOT. In our report we showed a case that became symptomatic 16 years after MVR. It is a very rare case because of its late development of LVOT obstruction.

The mechanisms responsible for LVOT obstruction are multifactorial. Patients with redundancy of the chordal apparatus, such as mitral valve prolapse with mitral regurgitation preoperatively, can develop LVOT obstruction after MVR and preservation of the valve leaflets. This has been explained on the basis of decreases in LV size after valve replacement and apparent reduction or slackening of chordal support. In this setting the native anterior mitral leaflet may be pulled toward the LVOT by a Venturi effect in which there is a pressure drop distal to a restriction with systolic emptying [5]. The drop of pressure immediately beyond the restriction pulls the mitral valve into the LVOT. This effect, coupled with anterior displacement of the native anterior leaflet with prosthesis insertion, may lead to LVOT obstruction.

The mechanism of SAM has been discussed related to mitral valve repair. Systolic anterior motion of the mitral valve causing LVOT obstruction occurs in 1% to 2% of patients having mitral valve repair. Lee and colleagues [6] reported that 22 of 1,045 patients having mitral valve repair were found to develop significant SAM of the mitral valve requiring a second pump run. Left ventricular outflow tract obstruction takes place when the redundant leaflet tips push into the left ventricular outflow tract and the mitral coaptation line is displaced anteriorly. When SAM occurs, reduction of the amount of annuloplasty or use of the posterior leaflet sliding procedure may eliminate this problem. Kreindel and colleagues [7] described that the development of SAM is related to insertion of the semi-rigid ring, persistence of redundant AML, narrowing of the LVOT, and the Venturi effect.

David [8] recommended some techniques to reduce this complication and suggested that preservation of the anterior leaflet chordae should be accomplished in patients by excising central, trapezoidal attachments, which would eliminate the risk of LVOT obstruction. In addition to his suggestion, folding back of the anterior mitral leaflet to be sutured to the annulus, with or without splitting leaflet centrally, is recommended to avoid LVOT obstruction [4]. In our case, as the nature of the mitral valve was myxomatous and redundant, the central portion of the AML should be resected in the first operation of MVR with prediction of SAM in the future.

Preservation of the AML may cause LVOT after MVR. It may be due to reducing ventricular volume and systolic ventricular emptying.


   References
Top
 Abstract
 Introduction
 Comment
 References
 

  1. David TE, Uden DE, Strauss HD. The importance of the mitral apparatus in left ventricular function after correction of mitral regurgitation Circulation 1983;68(Suppl II):76-82.[Free Full Text]
  2. Yun KL, Sintek CF, Miller DC, et al. Randomized trial comparing partial versus complete chordal-sparing mitral valve replacementeffects on left ventricular volume and function. J Thorac Cardiovasc Surg 2002;123(4):707-714.[Abstract/Free Full Text]
  3. Waggoner AD, Perez JE, Barzilai B, Rosenbloom M, Eaton MH, Cox JL. Left ventricular outflow obstruction resulting from insertion of mitral prostheses leaving the native leaflets intactadverse clinical outcome in seven patients. Am Heart J 1991;122(2):483-488.[Medline]
  4. Esper E, Ferdinand FD, Aronson S, Karp RB. Prosthetic mitral valve replacementlate complications after native valve preservation. Ann Thorac Surg 1997;63:541-543.[Abstract/Free Full Text]
  5. Come PC, Riley MF, Weintraub RM, et al. Dynamic left ventricular outflow tract obstruction when the anterior leaflet is retained at prosthetic mitral valve replacement Ann Thorac Surg 1987;43:561-563.[Abstract]
  6. Lee KS, Stewart WJ, Lever HM, Underwood PL, Cosgrove DM. Mechanism of outflow tract obstruction causing failed mitral valve repairanterior displacement of leaflet coaptation. Circulation 1993;88(5 Pt 2):II24-II29.[Medline]
  7. Kreindel MS, Schiavone WA, Lever HM, Cosgrove D. Systolic anterior motion of the mitral valve after Carpentier ring valvuloplasty for mitral valve prolapse Am J Cardiol 1986;57(6):408-412.[Medline]
  8. David TE. Mitral valve replacement with preservation of chordae tendinaerationale and technical considerations. Ann Thorac Surg 1986;41:680-682.[Abstract]



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Ryuichi Takahashi
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