- Email: [email protected]
Simplified correction of outflow obstruction after mitral valve replacement
Simplified Correction of Outflow Obstruction After Mitral Valve Replacement Mark K. Reed, MD, and Leigh I. G. Iverson, MD Department of Surgery, David Grant USAF Medical Center, Travis Air Force Base, California; and East Bay Heart Surgery, Oakland, California
Left ventricular outflow tract obstruction after mitral valve replacement may occur when a retained native anterior leaflet prolapses between prosthetic struts. Existing reports of left ventricular outflow tract obstruction by this mechanism lack emphasis on its surgical treatment. We obtained definitive relief of left ventricular
outflow tract obstruction by transaortic exposure, division, and partial excision of the obstructing leaflet. This approach minimizes the complexity and potential morbidity of the correction.
S
mitral leaflet stretched between struts of the prosthesis. A resection limited to this portion along with corresponding chordae was accomplished. Subsequent echo studies have documented normal prosthetic valve function without outflow tract obstruction, although the rhythm remains atrial fibrillation.
urgical treatment of mitral valve dysfunction preferentially preserves native tissue [l].When the anatomic exigencies mandate replacement, the mitral apparatus ought to be left intact to preserve left ventricular function [2, 31. Valve preservation, however, harbors the potential for postoperative ”sailing” of the native anterior leaflet with resultant left ventricular outflow tract obstruction (LVOTO). Previous reports of this complication have concerned its diagnosis more than its surgical treatment [4-61. We describe an expedient operative approach successfully used for 2 patients, 1 with severe acute postoperative LVOTO and the other with milder chronic LVOTO and secondary atrial fibrillation.
Case Reports Patient 1 A 74-year-old man was admitted with atrial fibrillation and congestive failure. Echocardiography showed left atrial and ventricular dilatation (6.9 and 5.9 cm enddiastolic dimensions, respectively) with mild aortic and severe mitral valve insufficiency. Catheterization revealed normal coronary arteries. At operation the native mitral valve was found to have myxomatous, billowing leaflets and ruptured chordae of the posterior leaflet. A portion of the excessive posterior leaflet with associated chordae fragments was removed, whereas the remaining valvular structures were left unaltered. A No. 33 CarpentierEdwards porcine heterograft was secured in the supraannular position with the valve sutures plicating the redundant anterior leaflet. Postoperatively, atrial fibrillation and a prominent systolic murmur prompted echocardiography showing systolic LVOTO with a gradient of 4.5 m/s (80 to 90 mm Hg). The patient was managed medically for 21 months but refractory atrial fibrillation and progressive exersional dyspnea mandated reoperation. Dissection was limited to that needed for exposure of the right atrium and the ascending aorta. The aorta was opened, and through the retracted aortic valve could be seen the anterior native Accepted for publication Feb 14, 1992. Address reprint requests to Dr Iverson, East Bay Heart Surgery, 365 Hawthorne Ave, Suite 301, Oakland, CA 94609-3102.
0 1992 by The Society of Thoracic Surgeons
(Ann Thorac Surg 1992;54:985-6)
Patient 2 A 69-year-old man with known aortic and mitral regurgitation was admitted with unstable angina and congestive heart failure. Echocardiography showed dilatation of the left atrium and left ventricle (5.3 and 6.0 cm end-diastolic dimensions, respectively) with a normal ejection fraction. The septum was 2.0 cm thick without abnormal motion. Catheterization showed severe mitral regurgitation and two-vessel coronary stenosis. At operation, saphenous vein grafts to the left anterior descending and right coronary arteries were performed. The mitral leaflets were highly redundant with greatly elongated chordae. A No. 31 Carpentier-Edwards porcine valve was placed in the supraannular position without excision of native valve structures. Anchoring sutures were directed through part of the extraneous anterior leaflet as we intended them to plicate it against the annulus. Postoperatively there was a harsh systolic murmur and a state of low cardiac output. Echocardiography and catheterization demonstrated severe systolic LVOTO prompting the patient’s return to the operating room. The aorta was opened below the grafts. Through the aortic valve, prosthetic struts were seen pressing the native anterior mitral leaflet against the septum. Transaortic resection of the obstructing tissue eliminated LVOTO. At 2 years’ follow-up, although remaining in atrial fibrillation, he is asymptomatic.
Comment Left ventricular outflow tract obstruction is a wellrecognized, albeit uncommon complication, of prosthetic valve placement in the mitral position. In years past, when the standard procedure for mitral valve replacement included excision of the native mitral leaflets and chordae, an oversized prosthetic valve relative to the receiving annulus was the typical cause of LVOTO after 0003-4975/92/$5.OO
986
Ann Thorac Surg
CASE REPORT REED AND IVERSON LEFT VENTRICULAR OUTFLOW OBSTRUCTION
mitral valve replacement [7, 81. Although it is now generally believed that the optimal left ventricular systolic pump function requires an intact mitral subvalvular apparatus [2, 31, an unaltered redundant anterior leaflet is liable to prolapse between prosthetic struts during systole with resultant LVOTO. Undoubtably, prevention is the best treatment. Techniques such as those described by David [9] preserve ventricular function while minimizing the likelihood of prosthetic-valve-associated LVOTO. These entail partial excision of excessive leaflet tissue, resuspension of the commissural edges, and the use of smaller valves with central flow. With these operative refinements, the occurrence of prosthetic-valve-associated LVOTO should become a rarity. Nonetheless, LVOTO needs to be considered in patients with a wide range of hemodynamic disturbances and an unexpected murmur after mitral valve replacement. Previous descriptions of interstrut prolapse of the mitral septa1 leaflet have aptly depicted its clinical variations and echocardiographic features but have not emphasized its surgical treatment [%5]. At one extreme, exemplified by our second case, is severe acute low output failure. Much milder, yet not inconsequential obstruction was manifested by refractory atrial fibrillation in the first case. Survival of patients in the former category clearly requires prompt surgical intervention. On the other hand, those whose obstruction is less severe may have insidious development of left ventricular failure with the long-term risks and functional impairment of chronic atrial fibrillation. In either case, we advocate transaortic exposure with division and excision of the obstructive mitral leaflet, which has proved to be an expeditious corrective procedure. Particularly advantageous for minimizing the morbidity of reoperation is the avoidance of dissection other than that needed to establish bypass. Without atriotomy,
1992;54:985-6
mechanical trauma to the previously operated heart is further diminished. Although such a limited approach raises serious concerns regarding de-aeration and venting, in practice these proved not to be difficulties. Should there yet be patients receiving medical management of this complication, we recommend they be considered candidates for surgical treatment using the approach we have outlined.
References 1. Livesay JJ, Talledo OJ. The current preference for mitral valve reconstruction. Tex Heart Inst J 1991;18:87-92. 2. Spence PA, Peniston CM, David TE, et al. Toward a better understanding of left ventricular dysfunction after mitral valve replacement: an experimental study with possible clinical implications. Ann Thorac Surg 1986;41:363-71. 3. Yun KL, Fann JI, Rahill SC, et al. Importance of the mitral subvalvular apparatus for left ventricular segmental systolic mechanics. Circulation 1990;82(Suppl 5):89-104. 4. 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;43:561-3.
5. Jacobs LE, Kotler MN, Ioli A. Left ventricular outflow tract obstruction following mitral valve replacement with Carpen-
tier-Edwards prosthesis. Echocardiography 1990;7:147-53.
6. Roberts WC, Dollar AL. Extreme obstruction to left ventricular outflow bv a biourosthesis in the mitral valve position. Am Heart J 1!991;121:;07-8. 7. lett GK, lett MD, Barnhart GR, van Riik-Swikker GL, Tones M, Clark RE. Left ventricular outflow tract obstruction with mitral valve replacement in small ventricular cavities. Ann Thorac Surg 1986;41:70-4. 8. Cohn LH. Complications related to mitral valve surgery. In: Waldhausen JA, Orringer MB, eds. Complications in car-
diothoracic surgery. St. Louis: Mosby-Year Book, 1991:251.
9. David TE. Mitral valve replacement with preservation of chordae tendinae: rationale and technical considerations.Ann Thorac Surg 1986;41:68&2.
INVITED COMMENTARY As mentioned by Reed and Iverson in their article, I agree that "prevention is the best treatment" of left ventricular outflow tract obstruction after mitral valve replacement with preservation of chordae tendineae. The operative technique they described to manage those 2 patients is logical, and it is simpler, safer, and more economical than mitral valve rereplacement. However, I believe that the important message in their article is to avoid this complication. A triangular resection of the anterior leaflet of the mitral valve with resuspension of the chordae tendineae is all that is required to prevent this problem (see reference [9]). The mitral apparatus is pulled toward the ventricular cavity during systole in patients with intact chordae tendineae because of contraction of the walls subtended by the papillary muscles. Consequently, the leaflets of the mitral valve may cause dynamic obstruction of the outflow tract in certain patients. This may occur after mitral valve repair for mitral regurgitation or after mitral valve
replacement with preservation of the anterior leaflet. Malorientation of a porcine bioprosthesis during mitral valve replacement may also cause obstruction of the outflow tract. Avoidance of plication of the mitral annulus in a single area after partial resection of a prolapsing segment of the posterior leaflet prevents outflow tract obstruction after mitral valve repair; partial resection of the anterior leaflet and correct orientation of a bioprosthetic valve prevent this complication after mitral valve replacement.
Tirone E . David, M D Division of Cardiovascular Surgery The Toronto Hospital 200 Elizabeth Street, 13 EN - 222 Toronto, Ontario M5G 2C4, Canada
Left ventricular outflow tract obstruction after mitral valve replacement may occur when a retained native anterior leaflet prolapses between prosthetic struts. Existing reports of left ventricular outflow tract obstruction by this mechanism lack emphasis on its surgical treatment. We obtained definitive relief of left ventricular
outflow tract obstruction by transaortic exposure, division, and partial excision of the obstructing leaflet. This approach minimizes the complexity and potential morbidity of the correction.
S
mitral leaflet stretched between struts of the prosthesis. A resection limited to this portion along with corresponding chordae was accomplished. Subsequent echo studies have documented normal prosthetic valve function without outflow tract obstruction, although the rhythm remains atrial fibrillation.
urgical treatment of mitral valve dysfunction preferentially preserves native tissue [l].When the anatomic exigencies mandate replacement, the mitral apparatus ought to be left intact to preserve left ventricular function [2, 31. Valve preservation, however, harbors the potential for postoperative ”sailing” of the native anterior leaflet with resultant left ventricular outflow tract obstruction (LVOTO). Previous reports of this complication have concerned its diagnosis more than its surgical treatment [4-61. We describe an expedient operative approach successfully used for 2 patients, 1 with severe acute postoperative LVOTO and the other with milder chronic LVOTO and secondary atrial fibrillation.
Case Reports Patient 1 A 74-year-old man was admitted with atrial fibrillation and congestive failure. Echocardiography showed left atrial and ventricular dilatation (6.9 and 5.9 cm enddiastolic dimensions, respectively) with mild aortic and severe mitral valve insufficiency. Catheterization revealed normal coronary arteries. At operation the native mitral valve was found to have myxomatous, billowing leaflets and ruptured chordae of the posterior leaflet. A portion of the excessive posterior leaflet with associated chordae fragments was removed, whereas the remaining valvular structures were left unaltered. A No. 33 CarpentierEdwards porcine heterograft was secured in the supraannular position with the valve sutures plicating the redundant anterior leaflet. Postoperatively, atrial fibrillation and a prominent systolic murmur prompted echocardiography showing systolic LVOTO with a gradient of 4.5 m/s (80 to 90 mm Hg). The patient was managed medically for 21 months but refractory atrial fibrillation and progressive exersional dyspnea mandated reoperation. Dissection was limited to that needed for exposure of the right atrium and the ascending aorta. The aorta was opened, and through the retracted aortic valve could be seen the anterior native Accepted for publication Feb 14, 1992. Address reprint requests to Dr Iverson, East Bay Heart Surgery, 365 Hawthorne Ave, Suite 301, Oakland, CA 94609-3102.
0 1992 by The Society of Thoracic Surgeons
(Ann Thorac Surg 1992;54:985-6)
Patient 2 A 69-year-old man with known aortic and mitral regurgitation was admitted with unstable angina and congestive heart failure. Echocardiography showed dilatation of the left atrium and left ventricle (5.3 and 6.0 cm end-diastolic dimensions, respectively) with a normal ejection fraction. The septum was 2.0 cm thick without abnormal motion. Catheterization showed severe mitral regurgitation and two-vessel coronary stenosis. At operation, saphenous vein grafts to the left anterior descending and right coronary arteries were performed. The mitral leaflets were highly redundant with greatly elongated chordae. A No. 31 Carpentier-Edwards porcine valve was placed in the supraannular position without excision of native valve structures. Anchoring sutures were directed through part of the extraneous anterior leaflet as we intended them to plicate it against the annulus. Postoperatively there was a harsh systolic murmur and a state of low cardiac output. Echocardiography and catheterization demonstrated severe systolic LVOTO prompting the patient’s return to the operating room. The aorta was opened below the grafts. Through the aortic valve, prosthetic struts were seen pressing the native anterior mitral leaflet against the septum. Transaortic resection of the obstructing tissue eliminated LVOTO. At 2 years’ follow-up, although remaining in atrial fibrillation, he is asymptomatic.
Comment Left ventricular outflow tract obstruction is a wellrecognized, albeit uncommon complication, of prosthetic valve placement in the mitral position. In years past, when the standard procedure for mitral valve replacement included excision of the native mitral leaflets and chordae, an oversized prosthetic valve relative to the receiving annulus was the typical cause of LVOTO after 0003-4975/92/$5.OO
986
Ann Thorac Surg
CASE REPORT REED AND IVERSON LEFT VENTRICULAR OUTFLOW OBSTRUCTION
mitral valve replacement [7, 81. Although it is now generally believed that the optimal left ventricular systolic pump function requires an intact mitral subvalvular apparatus [2, 31, an unaltered redundant anterior leaflet is liable to prolapse between prosthetic struts during systole with resultant LVOTO. Undoubtably, prevention is the best treatment. Techniques such as those described by David [9] preserve ventricular function while minimizing the likelihood of prosthetic-valve-associated LVOTO. These entail partial excision of excessive leaflet tissue, resuspension of the commissural edges, and the use of smaller valves with central flow. With these operative refinements, the occurrence of prosthetic-valve-associated LVOTO should become a rarity. Nonetheless, LVOTO needs to be considered in patients with a wide range of hemodynamic disturbances and an unexpected murmur after mitral valve replacement. Previous descriptions of interstrut prolapse of the mitral septa1 leaflet have aptly depicted its clinical variations and echocardiographic features but have not emphasized its surgical treatment [%5]. At one extreme, exemplified by our second case, is severe acute low output failure. Much milder, yet not inconsequential obstruction was manifested by refractory atrial fibrillation in the first case. Survival of patients in the former category clearly requires prompt surgical intervention. On the other hand, those whose obstruction is less severe may have insidious development of left ventricular failure with the long-term risks and functional impairment of chronic atrial fibrillation. In either case, we advocate transaortic exposure with division and excision of the obstructive mitral leaflet, which has proved to be an expeditious corrective procedure. Particularly advantageous for minimizing the morbidity of reoperation is the avoidance of dissection other than that needed to establish bypass. Without atriotomy,
1992;54:985-6
mechanical trauma to the previously operated heart is further diminished. Although such a limited approach raises serious concerns regarding de-aeration and venting, in practice these proved not to be difficulties. Should there yet be patients receiving medical management of this complication, we recommend they be considered candidates for surgical treatment using the approach we have outlined.
References 1. Livesay JJ, Talledo OJ. The current preference for mitral valve reconstruction. Tex Heart Inst J 1991;18:87-92. 2. Spence PA, Peniston CM, David TE, et al. Toward a better understanding of left ventricular dysfunction after mitral valve replacement: an experimental study with possible clinical implications. Ann Thorac Surg 1986;41:363-71. 3. Yun KL, Fann JI, Rahill SC, et al. Importance of the mitral subvalvular apparatus for left ventricular segmental systolic mechanics. Circulation 1990;82(Suppl 5):89-104. 4. 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;43:561-3.
5. Jacobs LE, Kotler MN, Ioli A. Left ventricular outflow tract obstruction following mitral valve replacement with Carpen-
tier-Edwards prosthesis. Echocardiography 1990;7:147-53.
6. Roberts WC, Dollar AL. Extreme obstruction to left ventricular outflow bv a biourosthesis in the mitral valve position. Am Heart J 1!991;121:;07-8. 7. lett GK, lett MD, Barnhart GR, van Riik-Swikker GL, Tones M, Clark RE. Left ventricular outflow tract obstruction with mitral valve replacement in small ventricular cavities. Ann Thorac Surg 1986;41:70-4. 8. Cohn LH. Complications related to mitral valve surgery. In: Waldhausen JA, Orringer MB, eds. Complications in car-
diothoracic surgery. St. Louis: Mosby-Year Book, 1991:251.
9. David TE. Mitral valve replacement with preservation of chordae tendinae: rationale and technical considerations.Ann Thorac Surg 1986;41:68&2.
INVITED COMMENTARY As mentioned by Reed and Iverson in their article, I agree that "prevention is the best treatment" of left ventricular outflow tract obstruction after mitral valve replacement with preservation of chordae tendineae. The operative technique they described to manage those 2 patients is logical, and it is simpler, safer, and more economical than mitral valve rereplacement. However, I believe that the important message in their article is to avoid this complication. A triangular resection of the anterior leaflet of the mitral valve with resuspension of the chordae tendineae is all that is required to prevent this problem (see reference [9]). The mitral apparatus is pulled toward the ventricular cavity during systole in patients with intact chordae tendineae because of contraction of the walls subtended by the papillary muscles. Consequently, the leaflets of the mitral valve may cause dynamic obstruction of the outflow tract in certain patients. This may occur after mitral valve repair for mitral regurgitation or after mitral valve
replacement with preservation of the anterior leaflet. Malorientation of a porcine bioprosthesis during mitral valve replacement may also cause obstruction of the outflow tract. Avoidance of plication of the mitral annulus in a single area after partial resection of a prolapsing segment of the posterior leaflet prevents outflow tract obstruction after mitral valve repair; partial resection of the anterior leaflet and correct orientation of a bioprosthetic valve prevent this complication after mitral valve replacement.
Tirone E . David, M D Division of Cardiovascular Surgery The Toronto Hospital 200 Elizabeth Street, 13 EN - 222 Toronto, Ontario M5G 2C4, Canada