Ann Thorac Surg 2002;74:1689-1691
© 2002 The Society of Thoracic Surgeons
Case report
Early bioprosthetic mitral valve "pseudostenosis" after complete preservation of the native mitral apparatus
Dimitris P. Korkolis, MD, PhDa,
Cary S. Passik, MDa*,
Stephen J. Marshalko, MD, PhDb,
George J. Koullias, MDa
a Departments of Cardiothoracic Surgery, Yale–New Haven Hospital, New Haven, Connecticut, USA
b Section of Cardiovascular Medicine, Yale–New Haven Hospital, New Haven, Connecticut, USA
Accepted for publication May 19, 2002.
* Address reprint requests to Dr Passik, Cardiothoracic Surgeons of New Haven, P.C., 2 Church St South, Suite 507, New Haven, CT, 06519, USA.
e-mail: cspassik{at}aol.com
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Abstract
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An advantage of bioprosthetic mitral valve replacement in patients with normal sinus rhythm is avoidance of the need for long-term anticoagulation. Bioprosthetic valve thrombosis is a rare complication, supporting this approach. This case report represents an example of porcine mitral valve stenosis, likely secondary to thrombosis, in which all of the native mitral valve apparatus was left intact. This was successfully treated with standard anticoagulation therapy. This complication should be considered in patients in whom retention of the mitral valve apparatus has been performed. Such patients may benefit from long-term anticoagulation treatment to obviate this event.
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Introduction
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Thrombosis of prosthetic valves, in general, affect mechanical prostheses. There have been several case reports of bioprosthetic mitral valve thrombosis that have led to early valve explantation. Resurrection of the technique of retention of the mitral valve apparatus during mitral replacement may lead to an increased incidence of this unusual complication.
A 76-year-old man was admitted to Yale–New Haven Hospital on March 5, 2001 with weakness, shortness of breath, and exertional chest pain. He had a known history of mitral valve prolapse. Transthoracic echocardiogram showed a flail posterior leaflet with p2 segment ruptured chordae, prolapse of the anterior leaflet, and 3+ mitral regurgitation. The ejection fraction was approximately 50%. Cardiac catheterization revealed critical triple vessel disease. Coronary artery bypass grafting was performed on March 7, 2001. This included a left internal mammary artery to the left anterior descending, and saphenous vein grafts to the distal right coronary, and second and third marginal branches of the circumflex artery. Exploration of the mitral valve disclosed severe myxomatous degeneration of both mitral leaflets, which would necessitate an extensive repair. Because of the patient’s age and the concomitant coronary artery disease, mitral valve replacement with a 27-mm Carpentier-Edwards porcine bioprosthesis was performed. Both leaflets of the mitral apparatus were preserved, with sutures placed in accordion fashion from the annulus to the tip of the leaflets and then through the valve. Postoperatively, the patient did well and was anticoagulated with Coumadin (crystalline warfarin sodium; Dupont Pharmaceuticals, Wilmington, DE). He was discharged on the 6th postoperative day in normal sinus rhythm. A routine echocardiogram at discharge showed a transmitral gradient of approximately 4 mm Hg, a normally functioning valve, and good ventricular performance. He did well in early follow-up. A left upper lobe nodule was found on a routine roentgenogram 3 months after surgery, suspicious for malignancy. Coumadin anticoagulation was discontinued and the patient underwent a thoracoscopic biopsy at another institution. This proved to be a benign granuloma. He was continued thereafter on aspirin. Five months after initial surgery, in August 2001, the patient was readmitted to Yale–New Haven Hospital with abrupt onset of shortness of breath and obvious signs of congestive heart failure. He was found to be in a new onset, rapid atrial fibrillation. His central venous pressure was above 20 mm Hg. On auscultation, he had a variable S1, a prominent pulmonic closure, a II/VI systolic ejection murmur, and no audible definite mitral regurgitation, diastolic rumble, or gallop. No signs of infectious endocarditis were found. There was no underlying coagulation disorder. Significant bilateral pleural effusions and interstitial edema were found on chest roentgenogram. A transesophageal echocardiogram now showed a transmitral gradient of 15.6 mm Hg with calculated pulmonary pressure of 50 to 70 mm Hg, as well as enlarged right heart, right ventricular strain, and bowing of the interventricular septum to the left. There was evidence of severe mitral stenosis. The valve leaflets looked thick, but their motion was only slightly decreased. There was turbulence across the valve, and evidence of smoke in the left atrium with no visible thrombus. Ejection fraction by echo was 45% (Fig 1A).
A ventilation/perfusion scan was negative for pulmonary embolism. Because of the rapid change in the appearance and function of a recently placed bioprosthetic mitral valve, the absence of a visible clot, and the lack of evidence for endocarditis, a conservative treatment plan was utilized with intravenous heparin anticoagulation, as well as with aspirin, aggressive diuresis, and pulmonary toilette. Four days after admission, while anticoagulated, the patient spontaneously converted to normal sinus rhythm with gradual clearing of congestive heart failure. A repeat echocardiogram showed almost complete flexibility of the prosthetic mitral valve leaflet tips and seemingly less bulk to the valve apparatus. The mean gradient had decreased to 4.4 mm Hg (Fig 1B). He was discharged on Coumadin with an international normalized ratio target of 2.5 to 3.5. At present, 1-year postoperatively, he continues to be well and free of cardiac failure.
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Fig 1. (A) Transesophageal echocardiogram depicting abnormally diffuse thickening of the bioprosthetic mitral valve leaflets (MV VTl) and increased mean gradient (Mn Grad) of 15.6 mm Hg. (B) Following intravenous heparin therapy, comparable transesophageal image depicting resolution of leaflet thrombus and normalization of mean gradient. (HR= heart rate.)
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Comment
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Bioprosthetic valves remain an attractive therapeutic option for many patients because long-term anticoagulation can, in most cases, be avoided with an extremely low risk of postoperative thrombosis [1]. Retention of both the anterior and posterior subvalvular apparatus in mitral valve replacement surgery has been demonstrated to play an important role in preserving left ventricular regional wall motion and global left ventricular function [2]. In addition, maintaining the tension-like effect of an intact mitral valve annulus-leaflet complex may prevent the rare but dreaded complication of myocardial rupture [3, 4]. Despite the absence of pathologic documentation in our case, the early onset of the disease, in a non-anticoagulated patient, as well as the clinical and echocardiographic findings, suggest an acute thrombo-obstructive etiology. In this patient, no known predisposing factors for valve thrombosis, such as an underlying coagulopathy, low ejection fraction, left ventricular dysfunction, or preexisting paroxysmal atrial fibrillation, were seen. The patient remained well during the immediate postoperative phase, during which time he received the traditionally accepted 3-month period of anticoagulation treatment. The preservation of both the anterior and posterior leaflets of the mitral valve may have potentially contributed to this presumed thrombotic "pseudostenosis." It may be assumed that mild abnormalities in blood rheology and the local turbulence, caused by the retained leaflets, might have a thrombogenic effect. The possibility of this complication should lead to consideration of a more aggressive trimming of the leaflets maintained, leaving only islands of tissue to preserve the underlying chordae [3]. This pathophysiologic mechanism and potential prevention have been proposed in the article of Fasol and Lakew [3], in which a mitral valve replacement had been performed with preservation of the posterior leaflet and complicated by an acute early thrombotic occlusion, leading to reoperation on the 8th postoperative day. Nevertheless, this complication was also seen in the case described by Thomas and colleagues [4], in a patient who underwent complete excision of the mitral apparatus. Although immediate reoperation has classically been the standard procedure for valvular thrombosis [5], it carries a high mortality rate, particularly in the mitral position. Thrombolytic therapy is a reasonable alternative option to surgical treatment [6]. However, the risk of acute cerebral thromboembolism, during thrombolysis for left-sided valve thrombosis, remains significant [6]. In contrast, the successful use of heparin in our patient, as well as the immediate resolution described by others [4], suggest that conventional anticoagulation treatment with intravenous heparin administration should be considered as the first therapy in patients with early bioprosthetic valve stenosis. In conclusion, patients who are seen with acute early valvular dysfunction and new onset congestive heart failure, particularly in bioprosthetic mitral valves with retention of the valvular apparatus, should be considered at risk for this thrombotic complication. These patients may potentially benefit from longer-term anticoagulation.
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References
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- Stein P.D., Alpert J.S., Dalen J.E., et al. Antithrombotic therapy in patients with mechanical and biological prosthetic heart valves. Chest 1998;114(Suppl 5):602S.[Free Full Text]
- Lillehei C.V., Levy M.J., Bounabeau R.C., Jr Mitral valve replacement with preservation of papillary muscles and chordae tendinae. J Thorac Cardiovasc Surg 1964;57:532-543.
- Fasol R., Lakew F. Early failure of bioprosthesis by preserved mitral leaflets. Ann Thorac Surg 2000;70:653-654.[Abstract/Free Full Text]
- Thomas B., Carreras F., Borras X., et al. An unusual case of bioprosthetic mitral valve thrombosis. Ann Thorac Surg 2001;72:259-261.[Abstract/Free Full Text]
- Akins C.W. Results with mechanical cardiac valvular prostheses. Ann Thorac Surg 1995;60:1836-1844.[Abstract/Free Full Text]
- Lengyel M., Fuster V., Keltai M., et al. Guidelines for management of left-sided prosthetic valve thrombosis: a role for thrombolytic therapy. J Am Coll Cardiol 1997;30:1521-1526.[Abstract]
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Abstract
Introduction
