Ann Thorac Surg 2004;78:832-836
© 2004 The Society of Thoracic Surgeons
Original article: cardiovascular
Clinical outcomes with the Hancock II bioprosthetic valve
Roy G. Masters, MDa,*,
Michel Haddad, MDa,
Andrew L. Pipe, MDa,
John P. Veinot, MDb,
Thierry Mesana, MDa
a Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Canada
b Pathology and Laboratory Medicine, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
Accepted for publication March 25, 2004.
* Address reprint requests to Dr Masters, University of Ottawa Heart Institute, 40 Ruskin St, Ottawa, ON, Canada, K1Y 4W7
rmasters{at}ottawaheart.ca
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Abstract
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BACKGROUND: The Hancock II bioprosthetic valve, which was first introduced to clinical use in 1978, differs from its predecessor in several ways. This study was designed to evaluate the durability and outcomes with this valve in patients who had isolated aortic or mitral valve replacements.
METHODS: From 1991 to 1999, 459 patients underwent aortic valve replacement and 138 patients underwent mitral valve replacement with the Hancock II bioprosthesis (Medtronic Inc, Minneapolis, MN). The mean age was 73.2 ± 0.4 and 72.6 ± 0.8 years in the aortic and mitral groups, respectively. Most patients were in New York Heart Association Class III or IV (50% aortic group and 69% mitral group) and concomitant coronary artery bypass was performed in 49.4% and 52.8% of patients, respectively. Patients were assessed annually and follow-up was up to 129 months in the aortic group and 100 months in the mitral group.
RESULTS: At 8 years, actuarial survival was 52% ± 5% in the aortic group and 57% ± 8% in the mitral group. Furthermore, the actuarial freedom from structural failure necessitating reoperation was 99% ± 0.5% in the aortic group and 98% ± 2% in the mitral group, and the actuarial freedom from repeat valve surgery due to all causes was 97% ± 2% and 96% ± 2%, respectively. Actuarial freedom from thromboembolic events was 89% ± 2% in the aortic group and 90% ± 5% in the mitral group.
CONCLUSIONS: The Hancock II valve has excellent midterm durability and clinical performance in older patients.
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Introduction
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The Hancock II porcine heart valve (Medtronics Inc, Minneapolis, MN) is a modified version of its predecessor, the Standard Hancock, and was first introduced for clinical use in 1978. Its treatment with the detergent sodium dodecil-sulfate in addition to using low pressure tissue fixation is purported to retard calcification and minimize leaflet collagen structural damage [1]. Furthermore, its Delrin stent (DuPont, Wilmington, DE) was designed to reduce mechanical stresses exerted on the leaflets. These changes are believed to reduce structural valve deterioration and improve patients' outcomes [1]. Despite all these changes, however, only few centers have reported their clinical experience with this valve. This paper reports our experience with this valve for isolated aortic valve replacement (AVR) and isolated mitral valve replacement (MVR) since our first use in 1991.
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Material and methods
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From May 1991 to December 1999 the Hancock II valve was used for isolated AVR in 459 patients and for isolated MVR in 138 patients at the University of Ottawa Heart Institute. Patients having combined aortic and mitral valve replacements were excluded from this study. The valve was implanted by 8 different surgeons using similar techniques and follow-up procedures. The operative technique included cardiopulmonary bypass with moderate hypothermia, topical cardiac cooling, and antegrade cold crystalloid cardioplegia. The implantation technique consisted of interrupted horizontal mattress sutures reinforced with Teflon pledgets.
This is a retrospective study that analyzed prospectively collected data. All valve recipients at our center are registered with the Valve Clinic, where survivors are assessed annually. Information was obtained mainly by clinic visit but occasionally by telephone calls to the patients. Data are presented in accordance with the Guidelines for Reporting Morbidity and Mortality After Cardiac Valvular Operations [2]. Continuous variables are presented as mean ± standard deviation. Actuarial estimates were calculated by means of the life-table technique using the SPSS statistical data analysis software (SPSS Inc, Chicago, IL) and are reported with 95% confidence limits.
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Results
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Long-term follow-up was up to 129 months in the aortic group (86% complete) and 100 months in the mitral group (97% complete). Mean age in the AVR group was 73.2 ± 0.4 years compared to 72.6 ± 0.8 years in the MVR group. Preoperative characteristics of these two groups are displayed in Table 1. While there was a preponderance of males in the AVR group, MVR patients had more advanced New York Heart Association (NYHA) functional class symptoms and had more frequent prior cardiac surgical procedures. All AVR patients having a reoperation had previous aortic valve replacements and all redo MVR patients had previous mitral valve repairs. Table 2 displays the operative details for both groups. Concomitant surgical procedures were frequent in both groups with 61% of AVR patients and 67% of MVR patients having an additional procedure, most frequently coronary artery bypass grafting (49.4% and 52.8%, respectively). Hospital mortality rates for patients who had isolated valve replacements were 5.6% and 4.6% in the AVR and MVR groups, respectively. This mortality rate was 10.6% in patients who had combined AVR and coronary artery bypass grafting (CABG). The mortality rate was higher in patients who had combined MVR and CABG (19.2%). The majority of those patients had advanced NYHA symptoms or shock (14 of 17 patients). Most causes of early deaths were cardiac in origin including low flow states, myocardial infarctions, ventricular arrhythmias, atrioventricular disruptions, and congestive heart failure leading to multiorgan system failure (Table 3).
Long-term survival
Figure 1 shows the actuarial survival for both groups. Actuarial survival at 8 years was 52% ± 5% and 57% ± 8% for the AVR and MVR groups, respectively. Table 3 displays the causes of late mortality in these patients. Most patients died of noncardiac causes during follow-up. Unfortunately, the causes of late deaths were unknown in 46% of AVR patients and 60% of MVR patients.
Reoperation
In the AVR group 5 patients required reoperation during follow-up. Reasons for reoperation included endocarditis in 1 patient (at 36 months postoperatively), structural valve failure in 2 patients (at 6 and 80 months postoperatively), and thromboembolism in 1 patient (at 18 months postoperatively). One further patient required a heart transplant for persistent heart failure following AVR. In the MVR group 3 patients underwent reoperation during follow-up. Endocarditis accounted for reoperation in 1 patient at 24 months postoperatively, while structural valve failure and paravalvular leak accounted for the other 2 (36 months and 2 months, respectively). The all cause actuarial freedom from reoperation for the AVR group at 8 years was 97% ± 2% compared to 96.0% ± 2.3% for the MVR group (Fig 2).
Stuctural valve deterioration
Two patients in the AVR group developed valve structural failure requiring reoperation at 6 and 80 months postoperatively. In the MVR group only one of the reoperations was for structural valve failure diagnosed at 15 months postoperatively. Consequently, the actuarial freedom from structural valve failure necessitating reoperation was 99% ± 0.5% in the AVR group at 8 years compared to 98% ± 2% for the MVR group (Fig 3).
Thrombosis
One episode of early valve thrombosis occurred in the AVR group leading to a fatal stroke in the hospital.
Thromboembolism
In the AVR group 34 thromboembolic events occurred in 31 patients (6.8%) during the follow-up period. Of these, 17 were transient ischemic attacks (TIAs) that occurred in 17 patients and 16 were cerebrovascular accidents (CVAs) that occurred in 14 patients. Many of these patients were taking coumadin at the time of their event (8 patients in each group). In addition, one patient with normal coronary arteries suffered a myocardial infarction 5 months after surgery. In the MVR group 4 patients (2.9%) had thromboembolic events including 1 with a TIA at 30 months and 3 with a CVA at 1, 3, and 38 months postoperatively. The patient who had a TIA was not on coumadin, while two of the CVA patients were taking coumadin. Actuarial freedom from thromboembolic events in the AVR group was 89% ± 2% at 8 years compared to 90% ± 5% in the MVR group.
Hemorrhage
Serious bleeding episodes necessitating hospitalization or blood transfusion affected 3.7% of patients in the AVR group over the follow-up period. All of these patients were anticoagulated with warfarin sodium. Of discharged AVR patients, 17.4% were on warfarin sodium mostly for atrial fibrillation (13.9%). Only one serious bleeding episode (0.7%) occurred in the MVR group during follow-up in a patient who was anticoagulated. Of discharged MVR patients, 38% were on warfarin sodium. The incidence of atrial fibrillation in the MVR group was 14.5% at hospital discharge. However, anticoagulation of MVR patients for 3 months was routine for some surgeons.
Endocarditis
Only 1 patient in each group developed endocarditis necessitating reoperation. These events occurred late after surgery (30 and 24 months in the AVR and MVR groups). None of these patients had endocarditis as the time of initial valve replacement. The actuarial freedom from endocarditis necessitating reoperation for AVR patients was 99% ± 0.5% at 8 years compared to 99% ± 1% for the MVR patients.
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Comment
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It is evident from our results that the midterm performance of this valve is excellent. Survival in both the AVR and MVR groups was compatible with that of other bioprosthetic valve patients. Cardiac causes accounted for the majority of early deaths. Of note, the higher than average mortality rate in the combined MVR and CABG group was likely due to the fact that most of those patients were in advanced NYHA class or in shock at the time of operation. Unlike data on early mortality, noncardiac causes such as cancer and stroke accounted for a greater proportion of late deaths. This was not surprising given the fact that most of our patients were elderly. Long-term survival in this patient group, however, compared favorably to patients in other studies.
Poirier and colleagues [3] reported their long-term experience with the Carpentier-Edwards (CE) pericardial valve in patients with a mean age of 65 years. The actuarial survival at 8 years for their AVR and MVR groups was approximately 70% ± 3% and 67% ± 7%, respectively. Cosgrove and colleagues [4 reported their experience with the CE pericardial valve in the aortic position in patients with a mean age of 64 ± 11 years. Actuarial survival at 8 years was approximately 64% ± 2% but this rate dropped to 46% ± 3% at 10 years. Corbineau and colleagues [5] reported their experience with the CE supraannular porcine valve in the aortic position in 278 patients. Actuarial survival at 8 years for patients aged 70 years and above was approximately 50 ± 4 years but this rate dropped to 41 ± 4 at 10 years. In 2001, David and colleagues [6] reported their long-term experience with the Hancock II valve in a patient population with a mean age of 65 ± 12 years. The actuarial survival at 8 years was reported to be approximately 70% ± 2% and 65% ± 3% for the AVR and MVR groups, respectively. These rates decreased to 65% ± 2% and 55% ± 3% for the AVR and MVR groups, respectively, at 10 years. Furthermore, Legarra and colleagues [7] reported their experience with the Hancock II valve in a patient population with a mean age of 62 ± 13 years. The survival probability at 10 years was reported to be approximately 68% ± 5% and 65% ± 6% for the AVR and MVR groups, respectively. This rate dropped to 45% ± 9% and 33% ± 12% at 18 years for the AVR and MVR patients, respectively. Recently, Rizzoli and colleagues [8] reported their results with the Hancock II valve in a small series of patients. Actuarial survival at 8 years was approximately 61% (confidence interval 51% to 71%) in the AVR group and approximately 62% (confidence interval 50% to 72%) in the MVR group. Actuarial survival at 10 years was 54% (confidence interval 41% to 65%) in the AVR group and 43% (confidence interval 38% to 58%) in the MVR group. Of note, our patients were on average 6 to 10 years older than those in the above studies, which might account for the slight discrepancy in survival rates. Furthermore, none of our late deaths were valve related, albeit some late deaths were due to unknown causes.
Valve related morbidity was also examined in this report. The incidence of structural valve dysfunction (SVD) necessitating reoperation was low in our study. This compares favorably with other published studies. David and colleagues [6] reported actuarial freedom from SVD at 8 years to be approximately 96% ± 1% and 92% ± 3% for the AVR and MVR groups, respectively, using the Hancock II valve. These results were very similar at 10 years with 97% ± 1% and 86% ± 3% freedom from SVD for the AVR and MVR groups, respectively. The results continued to be favorable at 15 years with 81% ± 5% and 66% ± 6% freedom from SVD in the AVR and MVR groups, respectively. The report by Legarra and colleagues [7] on their experience with this valve revealed an 8 year freedom from SVD of approximately 90% ± 5% for both the AVR and MVR groups. These results continued to be excellent at 10 years with 78% ± 5% freedom from SVD for both the AVR and MVR groups. Moreover, Rizzoli and colleagues [8] reported a 100% freedom from SVD at 8 and 10 years for the AVR group using the Hancock II valve. Freedom from SVD was also found to be good in the MVR group with 100% and 86% freedom from SVD at 8 and 10 years, respectively. In addition, our results also compare favorably with the CE pericardial data. Poirier and colleagues [3] reported 8 year freedom from SVD of approximately 98% ± 2% and 89% ± 7% for the AVR and MVR groups, respectively, using the CE pericardial valve. These rates decreased slightly to 93% ± 2% and 81% ± 7% at 10 years. The experience of Cosgrove and colleagues [4] with this valve implanted in the aortic position demonstrated a freedom from SVD of approximately 97% ± 1% and 91% ± 3% at 8 and 10 years, respectively. Our results could be attributed to the older age of our patient population. It has been reported that bioprosthetic valves remain free from SVD for a longer time in older patients, which might account for the observed differences among the studies. Jamieson and colleagues [9] demonstrated this clearly with their experience with the CE porcine valve. Freedom from SVD in that study for patients older than 70 years was reported to be 98% ± 1% and 82% ± 5% for the AVR and MVR groups, respectively, at 10 years. This was in sharp contrast to the 80% ± 6% and 64% ± 8% freedom from SVD in AVR and MVR groups, respectively, in patients younger than 40 years of age.
Freedom from reoperation in our experience also compares favorably with other published reports. David and colleagues [6] reported an 8 year freedom from reoperation of approximately 97% ± 1% and 96% ± 3% for the Hancock II valve in the aortic and mitral positions, respectively. These results continued to be good at 10 and 15 years postoperatively. Freedom from reoperation in the AVR group was 94% ± 1% and 77% ± 5% at 10 and 15 years, respectively; freedom from reoperation in the MVR group was 85% ± 3% and 68% ± 6% at 10 and 15 years, respectively. Poirier and colleagues [3] reported their reoperation rate at 8 years to be approximately 98% ± 2% and 82% ± 7% for the AVR and MVR groups, respectively, using the CE pericardial valve and 91% ± 2% and 76% ± 7% at 10 years.
Our results also demonstrated that the incidence of other valve related complications, such as valve thrombosis, embolism, and bleeding were low. We only had one reported case of valve thrombosis, which occurred perioperatively leading to a fatal embolic stroke. Many of our MVR patients were discharged home on warfarin while only 17.4% of the AVR patients received warfarin on discharge. David and colleagues [6] reported a 15 year freedom from embolic events of 83% ± 3% and 87% ± 3% for the AVR and MVR groups, respectively, with no cases of valve thrombosis. All of their MVR patients were discharged home on warfarin for 3 months. As for the AVR group, only patients who had their surgery before 1990 were discharged home on warfarin for 3 months, a practice that was terminated after 1990. The experience of Poirier and colleagues [3] with the CE pericardial valve revealed a freedom from thromboembolic events of 92% ± 2% and 93% ± 3% for the AVR and MVR groups, respectively, at 8 and at 10 years. Cosgrove and colleagues [4] reported the 8 and 10 year freedom from thromboembolic events using the CE pericardial to be 90% ± 2% and 89% ± 2%, respectively. All patients in that study received warfarin for 3 months postoperatively. In addition, 54% of the patients were on warfarin on last follow-up for various reasons. Any differences in thromboembolic rates could be attributed to discrepancies in the use of long-term anticoagulation, anticoagulation levels, or patient ages. The incidence of infective endocarditis and hemorrhage in our patients was extremely low and compared very favorably with other published studies [3–7].
It is clear from our experience that the Hancock II valve has a midterm durability and clinical performance profile that is similar to other widely utilized porcine and pericardial bioprosthetic valves. The rates of adverse events were quite low and compared very favorably with other available valves. This valve has been in clinical use for more than two decades in Europe and Canada and, as more experience is gained, longer term data should become available about its durability and performance.
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References
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- Wright JTM, Eberhardt CE, Gibbs ML, Saul T, Gilpin CB. Hancock II: an improved bioprosthesis. Cohn LH, Gallucci V. Cardiac Bioprosthesis. New York: Yorke Medical Books; 1982. p. 424–444
- Edmunds LH, Clark RE, Cohn LH, et al. Guidelines for reporting morbidity and mortality after cardiac valvular operations. Ann Thorac Surg. 1996;62:932–935[Abstract/Free Full Text]
- Poirier NC, Pelletier LC, Pellerin M, Carrier M. 15-Year experience with the Carpentier-Edwards pericardial bioprosthesis. Ann Thorac Surg. 1998;66:S57–61
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Top
Abstract
Introduction
= AVR; 
= MVR.)
