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J Thorac Cardiovasc Surg 2006;132:602-609
© 2006 The American Association for Thoracic Surgery

Surgery for Acquired Cardiovascular Disease

Fifteen-year results with the Hancock II valve: A multicenter experience

^a Cardiac Surgery Unit, Ca Foncello Hospital of Treviso, Treviso, Italy
^b Cardiac Surgery Unit, University of Padova, Padova, Italy
^c Cardiac Surgery Unit, Umberto I° Hospital of Venice, Venice, Italy.

Received for publication March 8, 2006; revisions received April 30, 2006; accepted for publication May 17, 2006.

^_* Address for reprints: Giulio Rizzoli, MD, Via Giustiniani 2, Padova, Italy 35121. (Email: giulio.rizzoli{at}unipd.it).

	Abstract

Top Abstract Introduction Patients and Methods Results Discussion References

 
OBJECTIVES: The purpose of this multi-institutional study was to review the 15-year outcome of patients who received isolated aortic or mitral valve replacement with the Hancock II bioprosthesis.

METHODS: From 1983 through 2002, 1274 patients underwent 1293 isolated valve replacements, 809 aortic valve replacements and 484 mitral valve replacements, at hospitals in the Venetian area (Padova, Treviso, and Venice). Mean age was 68 ± 8 years in patients undergoing aortic valve replacement and 66 ± 9 years in patients undergoing mitral valve replacement; 52% of patients undergoing aortic valve replacement and 63% of patients undergoing mitral valve replacement were in New York Heart Association class III or greater. Coronary artery disease was present in 32% of patients who had undergone aortic valve replacement and 18% of patients who had undergone mitral valve replacement. Follow-up included 8520 patient-years, with a median of 12 years, and was 97% complete.

RESULTS: Overall 15-year survival was 39.7% ± 2.4%, similar in both the aortic and mitral positions. Multivariable analysis of late survival showed the incremental risk of male sex, higher New York Heart Association class, coronary artery disease, and mitral position. Freedom from embolism was higher in the aortic position (81% ± 2.9% in aortic vs 72% ± 4.7% in mitral valve replacements). Freedom from endocarditis was similar in the aortic and mitral position (95% ± 1.2% vs 94% ± 1.7%). Freedom from reoperation (82% ± 3.7% vs 71% ± 5.0%) and from valve-related morbidity-mortality (52% ± 3.6% vs 36% ± 4.4%) was higher in patients who had undergone AVR. Actual freedom from structural valve deterioration for patients 60 years and older who had undergone aortic valve replacement was 96.5% ± 1.3% versus 88% ± 3.2% for patients who had undergone mitral valve replacement and 70% ± 7.5% versus 77.5% ± 5.3%, respectively, in younger patients. Multivariable Weibull analysis showed structural valve deterioration related to younger age and preoperative valve incompetence and inversely related to coronary artery disease.

CONCLUSION: Optimal 15-year durability can be expected in male patients 60 years and older who have undergone aortic valve replacement and in male patients 65 years and older who have undergone mitral valve replacement, extending safely the age limits for the use of this valve.

	Introduction

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Drs Valfrè, Mirone, Rizzoli, Gerosa, Bottio, and Salvador (left to right)

The aim of this multicenter study was to assess the long-term performance of isolated Hancock II aortic valve replacement (AVR) and mitral valve replacement (MVR) and compare it with similar North American follow-up^1,2 and to formulate recommendations for the use of this prosthesis.

	Patients and Methods

Top Abstract Introduction Patients and Methods Results Discussion References

 
Patients
From 1983 through 2002, 1274 patients received 1293 isolated aortic (n = 809) or mitral (n = 484) Hancock II prostheses at one of 3 institutions: the Treviso hospital, the University of Padova, or the Venezia hospital. Age, sex, and the distribution of several covariates are summarized in Table 1. Treviso contributed 984 records, Padova contributed 180, and Venezia contributed 129.

Operative Technique
Similar techniques were used in all 3 institutions with buttressed sutures. Prosthetic size was according to the patients' body size, and therefore the smallest aortic prosthesis inserted was 21 mm, and the smallest mitral prosthesis was 27 mm. Coronary artery bypass grafting was performed in patients with coronary artery disease of 70% or greater.

Outcomes
The primary outcomes were all-cause mortality and structural valve deterioration (SVD), which was defined as every clinical worsening caused by an intrinsic disease of the prosthesis (stenosis or incompetence) exclusive of infection or thrombosis and observed at reoperation, autopsy, or echocardiography. Additional outcomes were analyzed according to the guidelines of the American Association for Thoracic Surgery³ and included valve-related mortality; mortality and morbidity; permanent or transitory embolic events and hemorrhagic events requiring hospitalization blood transfusion, or both; prosthetic endocarditis; prosthetic thrombosis; and repeat AVR or MVR.

Statistical Analyses
Patients were censored when the valve was replaced, unless they were dead at the time of reoperation. The STATA statistical package was used (STATA Corp).

Univariate analysis
Prognostic variables were evaluated by using t tests and the Fisher exact test, and timed events were evaluated with the Kaplan-Meier method. Linearized rates were used for practical advantage unless clearly inappropriate.⁴ Simultaneous decrement analysis of survival with the original prosthesis was performed according to the method of Anderson⁵ by subtracting the cumulative incidences of death and SVD.

Multivariable analysis
Variables tested for their association with outcome were valve position (mitral and aortic), demographics (age and sex), valve pathology (insufficiency, mixed lesion, stenosis, active endocarditis, healed endocarditis, rheumatic, degenerative, ischemic, prosthetic pathology, and other pathology), preceding SVD event, preceding Hancock valve insertion, clinical factors (New York Heart Association [NYHA] class, atrial fibrillation, pacemaker, operative date, ascending aorta replacement, coronary artery bypass grafting, left internal thoracic artery use, emergency operation, operative center), and associated risk factors (hypertension, chronic renal failure, diabetes, previous cardiac surgery, coronary artery disease, critical coronary artery disease). Variables affecting late survival were evaluated by means of the Cox semiparametric model, and variables affecting SVD were evaluated by means of the Weibull parametric model. Variable choice, by means of stepwise backward and forward algorithm (P to enter = .19, P to retain = .2), was supported by bootstrap analysis, with 1000 repetitions of randomly selected samples with replacement.

	Results

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Thirty-day Mortality
There were 44 early deaths after AVR (5.5%; 95% confidence interval, 4%-7.2%) and 32 after MVR (6.6%; 95% confidence interval, 4.5%-9.2%).

Patient Survival
Aortic mortality occurred in 280 patients, and mitral mortality in 197 patients. Actuarial survival at 5, 10, and 15 years was 79.9% ± 1.5%, 59% ± 2.2%, and 39.7% ± 3.5% in the AVR group and 77.4% ± 2%, 56.7% ± 2.8%, and 39% ± 3.5% in the MVR group. The cause of late death was unknown in 17 mitral and 27 aortic patients.

Valve-related Deaths
Valve-related deaths occurred in 112 patients in the AVR group and 82 patients in the MVR group. Fifteen-year freedom from valve-related mortality was 71% ± 3% in the AVR group and 68% ± 3.8% in the MVR group (P = .33, Figure E1), and the linearized rates were 2.2% versus 2.5% per patient-year for AVR and MVR, respectively.

View larger version (12K): [in this window] [in a new window]   Figure E1. Freedom from valve-related death according to mitral valve replacement or aortic valve replacement.

Freedom From Valve-related Mortality and Morbidity
Actuarial freedom from valve-related mortality and morbidity is summarized in Table 2. The linearized rates were 3.7% per patient-year and 5.2% per patient-year in the AVR and MVR groups, respectively (P = .008, Figure E2). Cardiac death was the most frequent cause of death and accounted for 169 (60%) deaths in the AVR group and 143 (73%) deaths in the MVR group; 109 (39%) deaths in the AVR group and 54 (28%) deaths in the MVR group were unrelated to the cardiovascular system.

View larger version (12K): [in this window] [in a new window]   Figure E2. Freedom from valve-related mortality and morbidity according to mitral valve replacement or aortic valve replacement. VRMM, valve-related mortality and morbidity.

View larger version (12K): [in this window] [in a new window]   Figure E3. Freedom from embolism according to mitral valve replacement or aortic valve replacement.

Hemorrhage
Patients in the MVR group had 26 hemorrhagic events versus 25 events in patients in the AVR group, resulting in a higher hemorrhage rate 0.8% versus 0.5% per patient-year (P = .06, Figure E4). Fifteen-year freedom is reported in Table 2. Mitral-related hemorrhage was fatal in 11 (37%) patients, whereas aortic-related hemorrhage was fatal in 14 (56%) patients. Most hemorrhagic episodes (83%) occurred in patients receiving anticoagulant treatment. The operative age of patients with hemorrhage was similar for the MVR (60 ± 14 years) and AVR (58 ± 13 years) groups (P = .18).

View larger version (11K): [in this window] [in a new window]   Figure E4. Freedom from hemorrhage according to mitral valve replacement or aortic valve replacement.

View larger version (11K): [in this window] [in a new window]   Figure E5. Freedom from endocarditis according to mitral valve replacement or aortic valve replacement.

Reoperation
Eighty patients, 42 in the MVR group and 38 in the AVR group, required reoperation. The cause was SVD in 51 cases (19 in the AVR and 32 in the MVR groups). The second most common cause was endocarditis in 21 patients (12 in the AVR and 9 in the MVR groups). Two patients in the AVR group underwent reoperations for valve thrombosis, and 6 patients underwent reoperations for miscellaneous reasons, including 1 heart transplantation, 3 new valve involvements, 1 aortic aneurysm, and 1 aortic pseudoaneurysm. Patients undergoing reoperation were younger at the time of the original operation than those not undergoing reoperation (58 ± 1.14 versus 68 ± 0.2 years, P < .0001). Fifteen-year actuarial freedom is recorded in Table 2 for all patients and according to operative age. Actual freedom from reoperation is summarized in Table 3, according to operative age.

View larger version (20K): [in this window] [in a new window]   Figure 1. Actuarial freedom from SVD according to valve position. SVD, structural valve deterioration; CL, confidence limit.

View larger version (35K): [in this window] [in a new window]   Figure E6. Actuarial freedom from structural valve deterioration (SVD) according to age between 60 and 65 years or 65 or greater years.

View larger version (10K): [in this window] [in a new window]   Figure 2. Predicted probability of freedom from SVD according to operative age and to the mean of the covariates in the mitral and aortic position from the Weibull multivariable model. SVD, structural valve deterioration.

View larger version (14K): [in this window] [in a new window]   Figure 3. Simultaneous decremental analysis of the events of SVD, death, and survival with the original prosthesis based on their cumulated incidence for the Mitral Hancock II valve in patients with an operative age of 60 years or greater. SVD, structural valve deterioration.

View larger version (13K): [in this window] [in a new window]   Figure 4. Simultaneous decremental analysis of the events of SVD, death, and survival with the original prosthesis based on their cumulated incidence for the Aortic Hancock II valve in patients with an operative age of 60 years or greater. SVD, structural valve deterioration.

	Discussion

Top Abstract Introduction Patients and Methods Results Discussion References

 
Second-generation tissue valves have been engineered to enhance their durability. Results of multicenter investigations with reasonable groups at risk after a follow-up of 15 to 20 years are desirable to support a policy of prosthetic valve choice.⁶ At 15 years, we compared 26 aortic and 27 mitral second-generation Hancock II valves with 18 aortic and 9 mitral valves reported in 2001 by David and colleagues² and with 43 aortic and 8 mitral valves reported at 14 years by the Medtronic Multi-Center Clinical Investigation of 8 US hospitals.¹ Indication for use of this valve were similar, and ages of our patients were close to those reported by David and colleagues² and by the Medtronic study,¹ permitting unconfounded comparisons. The overall survival rate at 5 and 10 years was similar to that in the series by David and colleagues² and Medtronic.¹ At 15 years, survival was 33% in the Medtronic study,¹ 40% in the present study, and 47% in the study by David and colleagues.² In the mitral series our results were generally better than those reported in the studies by David and colleagues² and Medtronic¹ (39% vs 30% vs 25%), although this was likely due to differences in clinical presentation and NYHA class prevalence. Operative mortality is unrelated to prosthetic devices, with the exception of the incremental risk of small aortic prostheses.⁷ In this respect a 21-mm size was used in only 2.2% of our patients compared with in 19.9% of patients in the Medtronic series¹ and in 7% of patients in the series by David and colleagues,² and we did not use the 25-mm valve mitral prostheses. Long-term outcome after prosthetic valve replacement⁸ is affected by prosthetic complications, which, at 15 years, have been few and similar in the 3 series. A single exception is the 15-year freedom from valve-related deaths: in AVR this estimate was 92% in the series by David and colleagues² versus 71% in our series and 72% in the Medtronic series,¹ and in MVR this was 86% versus 68% versus 63%, respectively. The difference is due to the bias from inclusion of unknown causes of death, which were only 4 in the series by David and colleagues.² Freedom from embolism in AVR ranged from 83% to 78% and in MVR from 87% to 67%. Freedom from hemorrhage was 90% in the MVR group and 95% in the AVR group, which is similar to results seen in the Medtronic series.¹ Freedom from endocarditis was close to 95% in both AVR and MVR, which is similar to the rates observed in both of the other series. Endocarditis occurred mostly in the first postoperative year and randomly thereafter. Primary valve thrombosis in 4 valves was mostly caused by previous endocarditis. The Medtronic series¹ reported 3 cases of aortic valve thrombosis, and there were none in the series by David and colleagues.² Composite end points exaggerate differences in data reporting, and therefore overall freedom from valve-related mortality and morbidity compared with that seen in the series by David and colleagues² was 52% versus 59% in patients in the AVR group and 36% versus 48% in patients in the MVR group.

Valve position was not significant in our multivariable analysis of durability, and durability estimates converge in older patients (Figure 2). This is similar to the finding of the same grade of calcification in pairs of aortic and mitral bioprostheses simultaneously explanted from the same patient in the study by Bortolotti and associates.⁹ Our durability estimate (including patients not undergoing reoperation) for MVR in patients 60 years and older shows 15-year freedom of 88%, which is similar to the 89% freedom reported by David and colleagues.²

In AVR our data show 96.5% freedom from SVD versus 94% and 100% freedom observed by Medtronic¹ and David and colleagues,² respectively. These results are similar to those with another second-generation porcine valve, the Carpentier-Edwards SAV, for which Jamieson and coworkers¹⁰ reported 95% freedom from SVD in 100 patients older than 60 years. At 10-year follow-up, our results compare favorably with the Biocor valve results recently published by Myken.¹¹ In fact, this large series of a recently US Food and Drug Administration (FDA)–approved valve has only 5 patients who underwent AVR and no patients who underwent MVR who are older than 60 years of age and who are at risk at 15 years. It has been recently suggested by Rahimtoola⁶ that "the pericardial aortic valve may be the bioprosthesis of choice in older people." Indeed, Gao and associates¹² recently reported that the Perimount pericardial aortic valve was superior to the Edwards porcine valve. However, in these instances the comparisons are with first-generation porcine valves and not the second-generation Hancock II valve reported here. Gao and associates' Perimount durability of 99% freedom from explants for SVD at 10 years, with 6 valves at risk, is similar to our 98.7% freedom from all SVD, with 180 valves at risk. The analysis by Banbury and coworkers¹³ of the 267 Perimount aortic valves with comparable age (65 years) and mean follow-up (12 years) reveals a freedom of explants for SVD of 77% at 15 years versus 92.5%, 90%, and 97% freedom from SVD for the Hancock II valve reported by Medtronic¹ and David and colleagues² and in the present study, respectively. Our MVR freedom from SVD results also compare favorably with those reported for the Perimount mitral valve: Marchand and colleagues¹⁴ note a freedom from SVD of 66.3% at 14 years with 11 patients at risk versus our observation of 70.8% at 15 years with 27 patients at risk.

Jamieson and Madani¹⁵ commented that durability at 20 years will be the important milestone. Although 5% of our valves have been followed beyond 16 years, it is difficult for us to make accurate projections up to 20 years. Nonetheless, according to the 2002 Italian life tables,¹⁶ the life expectancy of a 60-year-old male is 20.8 years (25.2 years for a woman) versus a 19-year median durability of the aortic and 18-year median durability of the mitral Hancock II valve. Therefore given the AVR data observed here and the significantly reduced hemorrhage^17-19 and thromboembolic risk¹⁷ provided by the bioprosthesis, the data encourage use of this valve in males 60 years and older, particularly if coronary artery disease is also present. Observation of accumulated mitral SVD probability higher than 10% in patients 65 years and older and the prevalence of female sex with a 5-year longer expected survival balanced against the good freedom from all valve complications of the St Jude Medical mechanical valve reported by Khan and coworkers²⁰ might warrant a more prudent attitude for valve choice in MVR. The trend to provide total treatment for mitral valve disease, including atrial fibrillation ablation and left appendage removal, will require reassessing the pros and cons of biologic versus mechanical substitutes in this setting.

In conclusion, our results, with reasonable groups at risk, compare favorably with those of other reports and other bioprostheses and confirm the excellent durability of the Hancock II valve, particularly in patients 60 years and older undergoing AVR and patients 65 years and older undergoing MVR.

Limitations of the study include center bias (76% of the operations at a single center) and recall bias caused by ad hoc follow-up. A biased estimate of valve-related death and valve-related mortality and morbidity is also possible due to 44 (11%) untraced cause of late deaths.

	Footnotes

 
Supported by Ministry of University and Scientific Research, 2003 project "Meta-analisi degli studi comparativi dei risultati a distanza delle protesi biologiche e meccaniche." [Meta-analysis of the studies comparing long-term results of biologic and mechanical prostheses]

	References

Top Abstract Introduction Patients and Methods Results Discussion References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Giulio Rizzoli Salvatore Mirone Paolo Ius Elvio Polesel Tomaso Bottio Loris Salvador Claudio Zussa Gino Gerosa Carlo Valfrè Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Rizzoli, G. Articles by Valfrè, C. Search for Related Content PubMed PubMed Citation Articles by Rizzoli, G. Articles by Valfrè, C. Related Collections Valve disease