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Interact CardioVasc Thorac Surg 2007;6:379-383. doi:10.1510/icvts.2006.145193 © 2007 European Association of Cardio-Thoracic Surgery
Stuck leaflet of bileaflet prosthesis in mitral position – five cases to make us thinkCentre of Thoracic Surgery, S.João Hospital, 4202-451, Oporto, Portugal Received 21 September 2006; received in revised form 19 January 2007; accepted 23 January 2007
*Corresponding author. Centro de Cirurgia Torácica, Hospital de S.João, 4202-451, Porto, Portugal. Tel.: +351-2-5502417; fax: +351-2-5502254.
Objective: We present five cases of mitral bileaflet prosthesis dysfunction as a result of a stuck leaflet in closed position, diagnosed at surgery or during the first postoperative year. Methods and results: The diagnosis was made by echocardiography and could be confirmed by fluoroscopy in three patients. All cases had in common an early occurrence and the presence of a clean prosthesis by transesophageal echocardiography (TEE). In one patient the diagnosis was made by intraoperative TEE, and the problem could be solved by rotation of the occluding device. In the other four patients the diagnosis was made postoperatively and different strategies of treatment were taken. All but one case were reoperations, one had a dysfunctional biological prosthesis and three had been submitted to mitral valvoplasty (two rheumatic and one degenerative valves). According to our policy, patients started sodium warfarin therapy 24 h after surgery in order to keep International normalized ratio (INR) values between 2.5–3.5. Only in one case the presence of thrombus/pannus could be confirmed. Conclusions: We call the attention to causes other than thrombosis that can provoke leaflet block and to the importance of performing intraoperative TEE in patients submitted to mitral valve replacement. We also emphasize the fact that a stuck leaflet in a clean prosthesis can evolve without major symptoms or cardiac events.
Key Words: Prosthesis dysfunction; Stuck leaflet
Nowadays, bileaflet prostheses are the most used mechanical valves in the Western world as a result of their superior hemodynamic behavior and low incidence of valve complications, compared to the other mechanical models. Because of their peculiar design, the block of only one disk allows a near normal flow through the unimpeded leaflet with a low hemodynamic compromise [1]. According to literature, bileaflet prosthesis dysfunction is very uncommon [2–5]. However, despite being unusual, we ought to be attentive to the possibility of valve malfunction and be able to recognize this potential life-threatening complication by echocardiography and/or fluoroscopy [6, 7]. Although thrombosis is recognized as the main cause of a stuck leaflet [8–10], there are other mechanisms that can interfere with leaflet mobility. We present five cases of mitral bileaflet prosthesis dysfunction as a result of a stuck leaflet in closed position. According to our policy, patients started sodium warfarin therapy 24 h after surgery in order to keep International normalized ratio (INR) values between 2.5–3.5.
2.1. Case 1 A 61-year-old woman with mitral regurgitation due to a dysfunctional biologic prosthesis implanted in 1988 for rheumatic disease, was operated on at our Surgical Department on 3rd October 1995. She underwent mitral prosthesis replacement with a bileaflet St. Jude® 31 device implanted in anti-anatomic position and correction of tricuspid regurgitation with a Duran ring. The postoperative course was complicated by poor hemodynamics and TEE performed on the 15th postoperative day showed prosthesis dysfunction due to immobilization of the antero-lateral leaflet, without evidence of thrombus, normal function of both ventricles and mild tricuspid regurgitation. Because of her critical condition, the patient was immediately reoperated on. On inspection of the prosthesis, there was no evidence of thrombus or of an extrinsic cause for the leaflet immobility, so it was decided to replace the prosthesis for a new one (Carbomedics® 29). Unfortunately, the patient could not be weaned from cardiopulmonary (CP) bypass. A 35-year-old woman submitted to open mitral commissurotomy in 1984 and reoperated on at our Surgical Department on 27th October 1995 for severe calcified mitral stenosis. She underwent mitral valve replacement with a bileaflet Carbomedics® 27 prosthesis implanted in anti-anatomic position. The patient was easily weaned from bypass, the postoperative course was uneventful, and she was discharged on the 6th day under warfarin therapy. Nine months later, prosthesis obstruction was suspected because of high Doppler gradients (max-25, med-13 mmHg), and low functional valve area (1.6 cm2), by transthoracic echocardiography (TTE). INR on admission was 2.8. TEE was performed and showed a clean prosthesis with immobilization of the postero-medial leaflet; diagnosis confirmed by fluoroscopy. As the patient was NYHA class II, it was decided not to reoperate the patient, keeping a close follow-up performing TTE and fluoroscopy every six months and TEE biannually. Although the prosthesis functional parameters stayed unchanged for two years, because of the increase in the pulmonary systolic pressure from 40–60 mmHg, it was decided to intervene. The patient was operated on the 13th October 1998; there was evidence of thrombus/pannus material covering the immobilized leaflet and the prosthesis was replaced by a new Carbomedics® 29. Intraoperative TEE showed normal prosthesis function. The postoperative course was uneventful and the patient was discharged on the 7th day, after TTE and fluoroscopy confirmed normal prosthesis function. A 61-year-old woman submitted to open mitral commissurotomy in 1973 and reoperated on at our Surgical Department on 6th January 2000 for severe calcified mitral stenosis. She underwent mitral valve replacement with a bileaflet Carbomedics® 27 prosthesis implanted in anti-anatomic position. Because of technical difficulties related to heavy calcified ring and valve apparatus, an intraoperative TEE was requested and immobilization of the antero-lateral leaflet was observed. As the hemodynamic state was good we decided to optimize loading conditions but the leaflet remained immobilized and CP bypass was resumed. The inspection of the prosthesis did not disclose any problem and the two leaflets could be easily opened with a cotton-tipped swab. We hypothesized that a discrete subvalvar tissue could be interfering with the prosthetic mechanism and therefore, in an attempt to solve the problem, the occluding device was rotated to anatomic position. The patient could once again be easily weaned from bypass; the TEE was repeated and then normal mobility of both leaflets was shown. The postoperative course was uneventful and the patient was discharged on the 8th day, after TTE and fluoroscopy confirmed normal prosthesis function. A 59-year-old man submitted to quadrangular resection of the mitral posterior leaflet in 1993 and reoperated on at our Surgical Department on 28th April 2000 for severe regurgitation. The mitral valve was replaced by a Carbomedics® 29 prosthesis implanted in anti-anatomic position with preservation of the posterior leaflet. The patient was easily weaned from bypass, the postoperative course was uneventful, and he was discharged on the 7th postoperative day under warfarin therapy. Reevaluated two months later, the patient had no symptoms for daily activity, last INR was 3.4 but prosthesis obstruction was suspected because of the turbulent diastolic flow with slightly increased Doppler gradients (max-19, med-11 mmHg) and a low functional area (1.5 cm2) detected by TTE. TEE was performed and a clean prosthesis with immobilization of the postero-medial leaflet was shown; diagnosis confirmed by fluoroscopy.As a first approach, based on other experiences [5, 6], fibrinolysis with tPA was tried without success. Considering the risk of a new operation, because of a decreased ejection fraction, we decided to keep the patient under close follow-up performing TTE and fluoroscopy every six months and TEE biannually. Unexpectedly, the TTE performed in April 2004 showed normal mobility of both leaflets with a decrease in Doppler gradients (max-11, med-6 mmHg) and an increase in valve area to 1.8 cm2. The full mobility of both discs was confirmed by TEE and fluoroscopy (Fig. 1) and has been as such in posterior examinations. At the last consultation (24th May 2006) the patient was doing well, reporting improvement on exercise capacity, and the echocardiographic prosthesis parameters remained stable (mean gradient-6 mmHg, valve area 2 cm2).
2.5. Case 5 A 58-year-old woman with severe rheumatic mitral valve stenosis was operated on 15th April 2005. The heavily calcified mitral valve was replaced by a Carbomedics® 29 implanted in anti-anatomic position. The patient was easily weaned from CP bypass and stayed only for 24 h in the ICU. However, because of rhythm disturbance (atrial fibrillation with low ventricular rate) demanding temporary pacing, she was discharged from the hospital on the 25th postoperative day under warfarin therapy. Reevaluated two months later, she had no symptoms for daily activities, INR on admission was 2.9, but the transthoracic echo showed immobilization of the postero-medial leaflet with abnormal Doppler parameters (gradient mx-25, med-33 mmHg, functional area 1.4 cm2). This diagnosis was confirmed by TEE and fluoroscopy. As first therapeutic approach, fibrinolysis with tPA was proposed but the patient refused to accept the risks of any new intervention. One year later she is on NYHA class II, the leaflet remains immobilized with identical functional area (1.5 cm2) and the prosthesis remains clean (Fig. 2).
Few cases of one stuck leaflet of mitral bileaflet prosthesis, without evidence of prosthesis thrombosis on TEE, have been published. To the best of our knowledge, the first reported case was by Jaggers et al. [11] who described the intraoperative diagnosis by TEE of one leaflet immobilization of a St. Jude mitral prosthesis; on the suspicion of structural failure the valve was replaced. Since then, other cases have been referred and different mechanisms have been suggested as being responsible: extrinsic obstruction [11] and/or sub-optimal orientation [12–14].
When the diagnosis of one stuck leaflet was made by intraoperative TEE the problem could be easily solved in the majority of patients by simple rotation of the occluding device [13–15]. These data suggest prosthesis mismatch or interference of remnants of the native valve with leaflet's mobility, as possible causes of one leaflet immobilization. When diagnosed after surgery, different treatment strategies have been undertaken. In the absence of overt thrombosis (clean prosthesis or Our patients have in common an early occurrence of stuck leaflet (diagnosis at surgery or along the first postoperative year) and the presence of a clean prosthesis on TEE: absence of a distinct mass of echoes attached to the prosthesis clearly seen throughout the cardiac cycle [16] or of filamentous strands [17]. Only in Case 2 was thrombus/pannus confirmed as the mechanism of leaflet immobilization. Because pannus is more difficult to be detected by TEE than thrombus [16] it could have passed unnoticed. The possibility that tissue ingrowths could be the consequence, and not the cause of stuck leaflet, should also be considered as the surgical procedure occurred two years after prosthesis dysfunction diagnosis. In Cases 1 and 3, thrombosis could be ruled out by direct inspection of the valve, calling our attention for other causes of leaflet blockage. The behavior of Case 4 is puzzling. Full recovery of leaflet motion four years after surgery, when early thrombolysis did not succeed, is more in favor of remodeling of left ventricular geometry than spontaneous lyses as the reason for leaflet release. Our last patient refused any treatment, so the only information we can give is that the prosthesis remains clean on TEE one year after stuck leaflet diagnosis. Since 8th August 1986, when the first bileaflet valve was implanted, until 31st July 2006, 1024 mitral valves [730 Carbomedics (CM) and 294 St. Jude (SJ)] and 1285 aortic (853 CM and 432 SJ) have been implanted at our Center. Although not all patients are followed up at our Echo Lab, most of them performed a postoperative TTE in the first year after surgery. Looking at our data, blocking of a leaflet of a bileaflet prosthesis, without evidence of thrombus or strands on TEE, ought to be considered uncommon as in a twenty-year period we have only registered five cases. Like Shapira [9], we never observed a stuck leaflet in aortic position. In all patients the mitral prosthesis was implanted in anti-anatomic position because of greater leaflet clearance and to prevent the interference of the subvalvular mitral apparatus on leaflet mobility. However, as four cases were reoperations and the native valve was heavily calcified in the other, we admit that entrapment could have played a major role in leaflet immobility in most of our patients. The fact that four in five cases of stuck leaflet occurred with CM prosthesis, could be explained because this is the most frequently implanted valve in our institution. Nevertheless, during the same period we have also registered a greater incidence of reoperations for mitral bileaflet thrombosis with the CM prosthesis (13 CM vs. 1 SJ). These figures agree with the major data analysis published, comparing the two prosthesis models' performance, which reports a trend for a higher rate of complications with the CM in mitral position and with SJ in aortic position [18]. Differences in model design between the two prostheses that can justify a worse performance of CM in mitral position were reported. In the open position the CM valve leaflets protrude 2 mm further than the St. Jude's beyond the orifice level and that can make the interference of the ventricular wall or subvalvular apparatus on leaflets mobility easier [19]. Higher leakage velocities and turbulent shear stresses registered with the CM prosthesis, can explain a higher trend towards thrombotic events of this prosthesis [20]. Although most of the cases reported in the literature of intraoperative stuck leaflet are anecdotal, four cases were reported by Masiello et al. [13]. Once detected, this complication could be solved during surgery by simple rotation of the prosthesis [13–15] as happened with our patient (Case 3). It was our policy to perform routine intraoperative TEE only in patients programmed for mitral valve reconstruction, now we share the opinion of most of the experts that recommend routine intraoperative TEE in all patients submitted to mitral valve surgery [21]. When the diagnosis of stuck leaflet occurs after surgery, thrombolysis should be tried as an attempt to resume the normal leaflet mobility. We endorse this view because of the high success rate and low risk of complications reported by others [8–10], in spite of the fact that only in one of our patient's thrombus/pannus was the probable mechanism and in another one thrombolysis was ineffective. If this treatment does not succeed, we do not recommend rushing into surgery in high-risk patients if the prosthesis remains clean on TEE and the patient is in NYHA class I–II with a systolic pulmonary pressure <60 mmHg. We are in favor of this policy taking into consideration the risk of reoperations and the low probability of critic valve occlusion or systemic embolism in the absence of thrombus or strands on TEE. The possibility of spontaneous recovery of leaflet mobility, as happened in Case 4, strengthens our point of view. The question to be answered is how long should we wait?
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Abstract
1. Introduction
5 mm thrombus visualized), most of the authors agree on thrombolytic therapy as the first approach