Asian Cardiovasc Thorac Ann 1998;6:265-269
© 1998 Asia Publishing EXchange Pte Ltd
Three-Year Experience With the Ultracor Valve Prosthesis
Atilay Ta
delen, MD,
Cokun Ikizler, MD,
Sait Alamaci, MD,
Afshin Yavari, MD,
Enver Ekici, MD,
Gülnaz Arslan, MD
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Department of Cardiovascular Surgery Bakent University Hospital Bahçelievler Ankara, Turkey
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For reprint information contact: Atilay Tadelen, MD Department of Cardiovascular Surgery Bakent University Hospital Bahçelievler Fevzi Çakmak Caddesi 10 Sokak No. 45 Bahçelievler Ankara 06490, Turkey Tel:90 312 212 6868 Fax: 90 312 223 7333
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ABSTRACT
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From February 1992 to October 1995, 504 patients aged 3 to 69 years (median, 36 years) received 663 Ultracor prostheses (103 aortic, 259 mitral, 12 tricuspid, and 130 multiple). Early mortality was 2.77% with a rate of 3.88% for aortic valve replacement, 3.47% for mitral, 0% for tricuspid, and 0.99% for double valve replacement. Follow-up was 100% (719.5 patient-years) and the overall mortality (early and late deaths) was 3.76% with a rate of 4.85% after aortic valve replacement, 3.85% after mitral valve replacement, 8.33% after tricuspid valve replacement, and 2.97% after double valve replacement. There were no deaths among 29 patients who had triple valve replacement. All patients including 33 children (3.5 to 18 years of age) received sodium warfarin. The linearized risk per patient-year for all embolic events (major and minor) was 0.69%, 1.11%, and 0.69% for aortic, mitral, and multiple valve replacement respectively. When only major events were considered, the linearized risks were 0.27%, 0.13%, and 0% per patient-year respectively. Freedom from major systemic embolism was 99% ± 0.07% after aortic valve replacement, 99% ± 0.07% after mitral valve replacement, and 99% ± 0.06% after multiple valve replacement. Five patients suffered valve thrombosis, 4 of whom definitely received inadequate anticoagulation therapy. Sixteen patients had 25 episodes of anticoagulant-related hemorrhage. No structural failure was recorded and no significant hemolysis was found in the absence of periprosthetic leak. This experience encourages us to continue using the Ultracor prosthesis.
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INTRODUCTION
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Although heart valve replacement is a safe and commonly performed procedure, all available prostheses are associated with valve-related complications that influence their clinical use. With the introduction of a new prosthetic valve, it behoves surgeons and cardiologists to monitor its performance carefully and compare it with other prostheses. We introduced the Ultracor Prosthesis (AorTech Europe Ltd., Strathclyde, Scotland, UK) into our clinic in February 1992. We were particularly interested in its mechanical features that suggested the possibility of better hemodynamic performance: a 73-degree opening angle in the aortic prosthesis and a 68-degree opening angle in the mitral prosthesis, which give large effective orifice areas. This wide disc movement might facilitate flow through the prosthesis thus reducing the rate of thromboembolism. The orifice ring is machined from a solid block of titanium, eliminating welds. Flow-impeding structures are avoided in the lesser orifice by the single-strut design. Increased laminar blood flow results from the central location of the disc pivot axis. The prosthesis can be rotated within the knitted Teflon sewing cuff.
The purpose of this study was to analyze our clinical results with the Ultracor valve prosthesis in patients followed up for up to 3 years postoperatively. The preoperative, operative, and postoperative clinical findings are reviewed.
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PATIENTS AND METHODS
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Between February 1992 and October 1995, 504 patients received 663 Ultracor heart valves. Patients who underwent double valve replacement in which the second valve was not an Ultracor prosthesis were excluded from the study. The mean age of the patients in this study was 39 years; range, 3 to 69 years; 207 (41%) were male and 297 (59%) were female. Follow-up data were obtained at 3-month intervals. Most of the patients were in New York Heart Association functional class III or IV before the operation. Valvular disease was rheumatic in the majority of patients (Table 1
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Combined surgical procedures were carried out in 31 patients who required coronary artery bypass grafting as shown in Table 2. Myocardial revascularization was performed before mitral valve replacement to avoid raising the heart after the mitral prosthesis had been inserted thus decreasing the risk of myocardial rupture. Operative techniques included standard cardiopulmonary bypass with a disposable bubble or hollow fiber membrane oxygenator and moderate hypothermia (26°C to 30°C). Cold crystalloid cardioplegia and topical cooling were used for myocardial protection. Cardiopulmonary bypass was established using ascending aortic and bicaval cannulation employing systemic hypothermia and hemodilution. After meticulous debridement of the valve annulus, all prostheses were inserted using interrupted sutures of 2/0 Ethibond (Ethicon, Somerville, NJ, USA) and Teflon pledgets were used when needed in the aortic position. A continuous suture technique using 2/0 Ethibond was used in the mitral position. In the tricuspid position, 5 or 6 2/0 braided interrupted pledgetted sutures plus continuous suturing techniques were used. Valve sizes ranged from 19 to 33 mm. Cases of severe pulmonary hypertension were treated with a continuous infusion of nitroglycerine via a transventricular pulmonary artery catheter. This infusion was continued during the early postoperative period. At the same time, monitoring of pulmonary artery pressure was available using this catheter.
Sodium warfarin therapy was started either 48 hours after operation or as soon as the chest drains were removed, unless clinically contraindicated. We attempted to maintain the prothrombin time at approximately twice the normal control for patients with mitral valve or multiple valve replacements. In aortic valve replacements, the prothrombin time was prolonged to approximately 1.5 times normal. Antibiotic prophylaxis consisted of procaine penicillin (800,000 units), crystalline penicillin (1,000,000 units), and amikacin sulfate (500 mg) administered preoperatively and 5 days postoperatively.
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RESULTS
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Single valve replacement was performed in 374 patients; 259 had an Ultracor valve implanted in the mitral position, 103 had aortic valve replacement, and 12 had tricuspid valve replacement. Multiple valve replacement was performed in 130 patients of whom 96 had a double implant in the aortic and mitral positions, 4 had mitral and tricuspid valve replacement, and one had aortic and tricuspid valve replacement. Triple valve replacement (aortic, mitral, and tricuspid) was performed in 29 patients.
MORTALITY
Overall mortality was 3.76% (19/504). Fourteen patients died within 30 days of surgery and a further 5 died later. Causes of mortality are shown in Table 3. There was no mortality from thromboembolic complications. Four of the cases of late mortality were attributed to the prosthesis, resulting in a valve-related mortality of 7.9%.
Mortality rates according to valve position are shown in Table 4. Of the 259 patients who underwent mitral valve replacement, 10 died; 9 early and 1 late mortality. In the 103 patients who had aortic valve replacement, there were 4 early deaths and 1 late death. In the 12 patients who underwent tricuspid valve replacement, there was 1 late death. In the 101 patients who underwent double valve replacement, there was 1 early and 2 late mortalities. There were no deaths among the 29 patients who underwent triple valve replacement. Mortality among 31 patients who had concomitant coronary artery bypass grafting and valve replacement comprised 2 patients in early period (6.45%).
Complications were observed in 50 patients (9.9%) as listed in Table 5. Of the 8 patients who suffered a paravalvular leak, 2 had an aortic valve replacement and 6 had a mitral prosthesis. Reoperation was performed in all 8 patients. Five patients were found to have periprostatic dehiscence due to noninfectious causes, although one case had a fever with negative blood cultures in the initial postoperative period. Two patients had dehiscence several months after discharge from the hospital, that was probably due to poor quality of the annular tissue. The remaining patients will shortly undergo reoperation. The linearized incidence of complications was 0.33% per patient-year.
Thromboembolism was seen in 8 patients. Retinopathy was confirmed in 2 of these patients by computed tomography and another patient suffered a sudden occlusion of the superior mesenteric artery requiring partial resection of the jejunum. The other embolic events comprised 2 lower extremity arterial emboli and 4 cerebral emboli. All of these patients are currently alive and doing well. The linearized risk per patient-year for all embolic events (major and minor) was 0.69%, 1.11%, and 0.69% for aortic, mitral, and multiple valve replacement respectively. When only major events were considered, the linearized risks were 0.27%, 0.13%, and 0% per patient-year respectively. Freedom from major systemic embolism was 99% ± 0.07% after aortic valve replacement, 99% ± 0.07% after mitral valve replacement, and 99% ± 0.06% after multiple valve replacement.
Three of the 5 patients who suffered valve thrombosis have undergone mitral valve replacement and the other 2 had tricuspid valve replacement. Prothrombin times were very low in 3 of these patients because of poor compliance with anticoagulant therapy (sodium warfarin). One patient underwent reoperation one year after receiving a 25-mm Ultracor mitral valve prothesis for replacement with the same type and size of valve. Another patient who had been given a 25-mm Ultracor mitral valve to replace a 25-mm Carbomedics valve was readmitted one month later in deep circulatory collapse. Emergency surgery was successfully performed to replace the mitral valve with another 25-mm Ultracor prosthesis. This patient is currently doing well but she is still reluctant to comply with anticoagulant therapy. The third patient, who had an Ultracor valve implanted in the tricuspid position, required reimplantation two months later because of intermittent disc impingement, probably due to suboptimal positioning of the prosthesis during the first implant. The other 2 patients were operated successfully and given Ultracor valves of the same type and size.
Valvular dysfunction due to pannus formation was noted in 5 patients. One had the mitral valve replaced after one year, another in whom double valve replacement (mitral and tricuspid) had been performed, required mitral valve replacement after 2 years. The other 3 patients underwent mitral valve replacement after 3 to 4 years. All of these patients are doing well. Inspection of the pannus tissue revealed it did not result from ingrowth but rather from a healed minor infection.
Anticoagulant-related hemorrhage was seen in 16 patients including the 2 cases of fatal cerebral hemorrhage. Mild hematuria was observed in 8 patients who are now doing well. The other 6 patients had minor hemorrhages and are currently well.
Prosthetic valve endocarditis was observed in 6 patients. Four of these patients died as a result of the infection and account entirely for the valve-related mortality of this series. The other 2 patients were successfully treated and are doing well.
The functional status of surviving recipients of the Ultracor valve was favorable when compared to the status before the operation. Whereas 80.6% were in New York Heart Association functional class III or IV preoperatively, 96.04% were in class I or II by 6 months postoperatively. Furthermore, the profile did not change significantly at 1 year or 3 years after operation.
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DISCUSSION
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We began using the Ultracor valve in 1992. We are now able to examine our 3-year experience with this valve but we are as yet unable to report long-term survival or to compare the results with other studies.
Thromboembolism was the major complication after prosthetic valve replacement. According to Nakano and colleagues1 the linearized rate of thromboembolism for aortic, mitral, and double valve replacement was 1.35%, 1.63%, and 0.79% per patient-year respectively. Akins2 reported the performance characteristics and complications of 4 mechanical valves approved for use in the United States. For the St. Jude Medical valve, the composite linearized rate of thromboembolism calculated from the available data in 4823 patients was 1.6% per patient-year (range, 0.7% to 2.8%) for aortic valve replacement alone and 2.4% per patient-year (range, 0.4% to 4%) for mitral valve replacement alone. Our results show a similar or lower incidence than these previous reports.
The rates of thromboembolic complications in our series (0.69% to 1.1% per patient-year) also compare favorably with other studies where the rates ranged from 1.1% to 2.9% per patient-year for mechanical valves in different positions.3–5 Our thromboembolic rates also compare favorably with those reported by Daenen and colleagues6 for aortic valve replacement with a ball valve prosthesis (2.8%), tilting-disc prosthesis (2.5%), and porcine prosthesis (3.8%) as well as for mitral valve replacement with a ball valve prosthesis (3.2%), tilting-disc prosthesis (3.5%), and porcine prosthesis (3.8%). The fact that the Ultracor prosthesis has an almost central flow led us to speculate that the incidence of thromboembolism might be reduced. We found that the incidence of thromboembolism was low and comparable to the best results reported. In addition, the low incidence of thromboembolism in multiple valve recipients is of note because it is counterintuitive, that is, the population with the greatest amount of prosthetic material ought to be at greater risk.
We also found a low incidence of anticoagulant-related hemorrhage, which may be attributed to the relatively low level of anticoagulation giving approximately twice the control prothrombin time after mitral and multiple valve replacement and 1.5 times control level after aortic valve replacement. Although occasional reports of structural failure of the St. Jude valve have appeared, to our knowledge, none of our 504 patients has sustained this complication. The incidence of prosthetic valve endocarditis in this series is quite low (1.1%) and comparable to findings with the St. Jude Medical prosthesis.3–5 We attribute a low incidence of valve endocarditis to complete tissue ingrowth of the cloth sewing ring providing protection from bacterial invasion.
Operative mortality may be more strongly influenced by preoperative patient characteristics and operative factors (such as myocardial protection, operative techniques, and treatment of pulmonary hypertension) than by valve performance. Our overall operative mortalities for isolated mitral or aortic valve replacements (0.79% to 1.78%) compare favorably to those reported by the groups of Arom3 (5.2% to 11.9%) and Kratz5 (3.5% to 3.9%) and our multiple valve replacement mortality is markedly low (0.59%). Most deaths in this series were from non-prosthesis-related causes. The strongest risk factor re ported for death after valve replacement is the presence and extent of associated coronary artery disease; other independent risk factors include advanced age (greater than 70 years), advanced preoperative New York Heart Association functional class (III or IV), and the presence of malignant ventricular ectopic beats.7–9 Thus, a series with a relatively low proportion of high-risk patients may be expected to have a low operative mortality and a high survival rate.
Long-term survival is related to both underlying cardiac function and age as well as to valve performance. We have no objective hemodynamic data available from this series. However, a large proportion (46/103) of our aortic valve replacement patients received small (19-mm or 21-mm) prostheses and, significant and sustained functional improvement was noted.
In our experience, the Ultracor valve was found to be a reliable prosthesis. One of the major advantages of this valve is its low profile, making it especially useful in children and adults with small ventricles, particularly women. The results of this study encourage us to continue using the Ultracor prosthesis with its excellent hemodynamic performance and absence of structural failure over 3 years.
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REFERENCES
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Nakano K, Imamura E, Hashimoto A, Aosaki M, Endo M, Hayashi H, et al. Six-year experience with the St. Jude Medical prosthesis: early and late results of 540 valves in 462 patients. Jpn Circ J
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Akins CW. Mechanical cardiac valvular prosthesis. Ann Thorac Surg
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Czer LS, Chaux A, Matloff JM, DeRobertis MA, Nessim SA, Scarlata D, et al. Ten-year experience with the St. Jude Medical valve for primary valve replacement. J Thorac Cardiovasc Surg
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Kratz JM, Crawford FA Jr, Sade RM, Crumbley AJ, Stroud MR. St. Jude prosthesis for aortic and mitral valve replacement: a ten-year experience. Ann Thorac Surg
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Daenen W, Nevelsteen A, van Cauwelaert P, de Maesschalk E, Willems J, Stalpaert G. Nine years experience with the Björk-Shiley prosthetic valve: early and late results of 932 valve replacements. Ann Thorac Surg
1989;48:280–3.[Abstract]
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Gabbay S, Yellin EL, Frishman WH, Frater RWM. In vitro hemodynamic comparison of St. Jude, Björk-Shiley and Hall-Kaster valves. Trans Am Soc Artif Intern Organs
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Baudet EM, Oca CC, Roques XF, Laborde MN, Hafez AS, Collot MA, et al. A 5-year experience with the St. Jude Medical cardiac valve prosthesis. Early and late resultsof 737 valve replacements in 671 patients.J Thorac Cardiovasc Surg
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Duncan MJ, Cooley DA, Reul GJ, Ott DA, Hallman GL, Frazier OH, et al. Durability and low thrombogenicity of the St. Jude Medical valve at 5-year follow-up. Ann Thorac Surg
1986;42:500–5.[Abstract]
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ABSTRACT
INTRODUCTION
