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Ann Thorac Surg 2005;79:772-775
© 2005 The Society of Thoracic Surgeons
a Heart Center, University of Leipzig, Leipzig, Germany
b Clinic for Cardiac Surgery and Cardiology, Leipzig, Germany
Accepted for publication August 13, 2004.
* Address reprint requests to Dr Walther, Universität Leipzig, Herzzentrum, Klinik für Herzchirurgie, Strümpellstr 39, 04289 Leipzig, Germany (E-mail: walt{at}medizin.uni-leipzig.de).
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Abstract |
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METHODS: Fifty-two patients (68 ± 8.5 years old; 36 female) have been prospectively evaluated since August 1997. The chordally supported SMV (Quattro) was implanted for mitral stenosis (n = 26), severe incompetence (n = 17), or mixed lesion (n = 9). Preoperative New York Heart Association class was 3.1 ± 0.6. Twenty patients received additional intraoperative ablation therapy. Mean follow-up is 37.3 ± 18.7 months (range, 1 to 65).
RESULTS: Surgery was performed using conventional sternotomy (33) or anterolateral minithoracotomy (19). Atrial rhythm was reestablished in 17 of 20 patients. Six patients operated on early in this series required reoperation, 2 for paravalvular leakage, 2 for functional stenosis, 1 with pannus formation due to underlying rheumatoid disease, and 1 for papillary flap rupture after 5.1 years. Mortality was 1 perioperative (1.9%, nonvalve related) and 1 after reoperation due to multiorgan failure. During late follow-up (30 ± 7 months postoperatively) 5 patients died of noncardiac causes. Regular echocardiographic control revealed good SMV function (maximum transmitral blood flow velocity 1.7 ± 0.2 m/s; mean transmitral pressure gradient 3.9 ± 1.2 mm Hg) and well-preserved ejection fraction postoperatively as well as at most recent follow-up.
CONCLUSIONS: The clinical experience after 5.5 years of SMV implantation is promising. Preservation of annuloventricular continuity is advantageous. However, long-term durability remains to be proved.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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The stentless mitral valve (SMV) has been designed to preserve most of the native MV functionality. Ideally, it should match most of the criteria for an optimal prosthetic mitral valve. Those criteria include a relatively easy implantation technique to achieve a low perioperative risk, sufficient durability, no risk of thrombembolic events, no immunologic reaction, possibly endothelialization after implantation, and morphologic features such as a flexible annulus and fixation at the papillary muscles. Furthermore, good hemodynamic function with a sufficient opening area, central blood flow, a low gradient, good leaflet motion, and a sufficient coaptation area to prevent any incompetence are expected.
The aim of this report is to delineate the current clinical experience with SMV implantation. This experience is based on 52 implants at our center that are part of a worldwide feasibility study of 218 implants at present. In this context, the requirements for an ideal mitral prosthesis are evaluated.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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The SMV is made from glutaraldehyde tanned bovine pericardium with an additional Polyol anticalcification treatment, as described before [9–11]. The two papillary flaps are anchored at the patient's papillary muscles, and the three-layered annulus is designed to prevent dilatation. The valve is available in three sizes: large (30 mm), medium (28 mm), and small (26 mm).
Surgery was performed through a median sternotomy (n = 33) or a lateral minithoracotomy (n = 19) on standard cardiopulmonary bypass, moderate hypothermia, and crystalloid cardioplegic arrest. The SMV implantation was performed after complete excision of the diseased MV. Sizing followed direct and echocardiographic measurements. A standard sizer was used to measure the distance between the commissures to give an information about the valve size. Another specially designed rulerlike sizer was then used to measure the distance from the tip of the papillary muscles to the annulus. The latter measurements were correlated with transesophageal echocardiography (TEE) measurements of that distance performed under hemodynamically stable conditions preoperatively. The papillary flaps were implanted using two Teflon armed Tevdek II 3/0 sutures (Deknatel; Genzyme Corp, Fall River, MA) each and the annulus using two or three running sutures (Prolene 3-0; Ethicon, Somerville, NJ). Implantation of the papillary flaps is possible in variable depths for any of the three different valve sizes. Additional left atrial ablation therapy to restore sinus rhythm was performed in selected patients with chronic atrial fibrillation, as described before [12]. Lately, a cryoablation probe has been used.
Mean follow-up is 37.3 ± 18.7 months (range, 1 to 65), total follow-up 151.7 patient-years, and no patient was lost to follow-up. Examinations are being performed at our outpatient clinic. Patients living farther than 150 km from the hospital (n = 5) were interviewed by telephone; in addition, physical and echocardiographic examinations were performed by their family physicians. All patients were instructed to contact the hospital immediately in the event of any unexpected deterioration of health conditions.
Transthoracic echocardiographic examinations (TTE) were performed preoperatively, before discharge, and at every follow-up visit. Multiplane TEE was used intraoperatively or whenever information in addition to TTE measurements was required. Cardiac morphology and function as well as valve hemodynamics were assessed using standard measurements.
Absolute and relative frequencies were calculated and results are given as mean ± standard deviation. After assessing for normal distribution the Student t test for matched pairs was applied. A p value less than 0.05 was considered significant. Valve-related morbidity and mortality were evaluated according to standard guidelines [13].
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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After initially uneventful surgery, 3 patients required reexploration for bleeding. One of those (aged 85 years) died perioperatively owing to low cardiac output syndrome (in-hospital mortality 1.9%). Besides standard postoperative therapy, patients were discharged on aspirin 100 mg daily only if they were in sinus rhythm, and received systemic anticoagulation therapy (warfarin) only if additional atrial fibrillation was present.
During follow-up 6 patients—all operated on early in this series—required reoperation with subsequent explantation of the SMV: 1 for posterior paravalvular leakage having a calcified annulus at 10 months, 1 for anterior paravalvular leakage due to constant pressure on the papillary flaps at 7 months, 1 for functional stenosis of a 30-mm SMV (this patient received a 25-mm mechanical valve at 8 months), 1 for functional stenosis at 15 months, 1 for degenerative alterations with pannus ingrowth of the prosthesis in preexisting severe rheumatoid disease at 4 months, and 1 for partial papillary flap rupture 5 years after the initial operation (at explantation, the SMV that had been in place for more than 5 years did not show any signs of calcification and was completely flexible; it was healed in very well with a slight endothelial cover at the annulus). The second of these 6 patients died of multiple organ failure 4 weeks after reoperation; all others were discharged in good condition.
During follow-up, 5 patients died, 1 each of spine fracture and renal failure, stroke without evidence of thrombi, large bowel malignoma, heart failure, and pneumonia. All had had normal SMV function at most recent echocardiographic follow-up. Mean interval since the operation was 30 ± 7 months (range, 12 to 49). These patients were slightly older than the others at SMV implantation (71 ± 5.6 years; range, 62 to 77); the underlying mitral valve disease was stenosis in 3, incompetence in 1, and a combined lesion in 1 patient; body surface area was 1.63 ± 0.1 m2 (p < 0.05 versus all other patients), and preoperative cardiac index had been 1.38 ± 0.1/Lmin/m2 (p < 0.01 versus all other patients).
At discharge, 30 patients were in sinus rhythm, 12 patients were in atrial fibrillation, and 9 patients had a pacemaker. Six of those had a pacemaker preoperatively, and 3 required pacemaker implantation after additional left atrial ablation therapy. Of the 20 patients receiving ablation therapy, 14 were discharged in sinus rhythm and 3 were discharged with an atrioventricular pacemaker; the other 3 had persistent atrial arrhythmia. Intermittent medical therapy was required in 11 and electrical cardioversion in 8 patients. During follow-up, all patients remained in stable sinus rhythm.
Echocardiography showed good valve function in all patients intraoperatively. Trivial transvalvular refluxes as caused by the closing volume and seen with most conventional heart valve prostheses were accepted. Comparative echocardiographic results are given for 51, 35, and 23 patients at discharge, at 12 months, and at 48 months (Table 2). During follow-up there was no relevant difference in mitral orifice area index. No relevant increase in mitral incompetence was seen. At most recent follow-up, there was no evidence of SMV calcification in any patient.
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Implantation of the SMV is quite easy and can be performed almost like conventional MV replacement. Severe calcification of the annulus will be problematic, as it is in conventional MV surgery as well. For implantation, standard Prolene sutures can be used with a running technique. Exact sizing, especially of the distance of the papillary flaps, is the crucial part during SMV implantation. This is extremely important to avoid tension on the annulus as well as central valve incompetence due to loose papillary flaps and thus a reduced coaptation area. The tools available for intraoperative measurements are helpful. However, we strongly recommend performing TEE sizing (measurement of the distance between the tips of the papillary muscles and the MV annulus) under hemodynamically stable conditions before cardiopulmonary bypass is initiated.
At present, the durability of the SMV can be regarded as sufficient, but we do not know about long-term results (more than 10 years). The SMV has proven good durability in our older European patients for as long as 5.5 years and in younger South African patients for as long as 6 years. There is hardly any calcification of the device visible at echocardiographic examinations. Furthermore, we did not see any signs of calcification on the recently explanted valve 5.1 years after implantation. Thus, the Polyol treatment seems to safely prevent intrinsic calcification of the device. Rupture of that papillary flap in 1 patient has to be judged as structural dysfunction. Since 1999, however, the fiber orientation of the bovine pericardium has been aligned in a longitudinal way. That will securely prevent any further rupture. Thrombembolic events did not occur in our series at all. Therefore, we think that the SMV carries a very low thrombembolic risk. There were no events despite the fact that the majority of our patients—all who were in sinus rhythm—did not receive systemic anticoagulation therapy. Patients can therefore be safely discharged on aspirin 100 mg daily only, whenever sinus rhythm is present. Immunologic reactions did not occur during the whole series worldwide. As with conventional xenografts, glutaraldhyde is used for crosslinking of the tissue. Thus, as with conventional xenografts, immunologic reactions will not occur. Endothelialization was seen during explantation of the SMV, and no relevant tissue ingrowth was observed. Flexibility of the SMV was seen at all echocardiographic follow-up examinations. Furthermore, the SMV explanted after 5.1 years was completely flexible without any stiffness at all.
Summarizing these aspects, close to physiologic function has been achieved with the SMV. Fixation at the papillary muscles is a basic physiologic principle of MV function and has been preserved by the SMV design. The papillary muscles were sufficient to suspend the SMV in most patients worldwide. It is advantageous to preserve the annuloventricular continuity and thus maintain left ventricular function. This has been proven by our echocardiographic results on stable left ventricular function after as long as 5.5 years of valve implantation.
The hemodynamic function of the SMV is good during current follow-up. Transprosthetic blood flow velocities as well as mean pressure gradients were in the normal range after MV replacement therapy. A uniform transvalvular blood flow profile was seen in most patients with only minimal transvalvular reflux in some. That was equivalent to the closing volume of most conventional heart valves and attributable to the four edges of the valve between the different pieces of pericardium.
In conclusion, the SMV has to be regarded as an alternative to conventional MV xenografts for selected patients in whom mitral valve repair is not possible. It combines physiologic MV principles such as fixation at the papillary muscles, a flexible annulus, and a large coaptation area. For the first time, a prosthesis with a function similar to that of native MV became available in standard sizes. The deaths observed can be attributed to underlying conditions of the patients, as valve function was normal during most recent echocardiographic control. The SMV meets most criteria to become an ideal heart valve. However, long-term follow-up is required.
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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