Long-Term Results of Aortic Valve Replacement

– Mechanical Prostheses vs. Bioprostheses –

The annual report of the Japanese Association for Thoracic Surgery 2011 disclosed that valve repair was performed in 11,300 patients and valve replacement was done in 16,500 patients.¹ Implanted prosthetic valves consisted of 5,000 mechanical prostheses (MPs) and 11,500 biological prostheses (BPs). The choice between a MP or BP for a patient undergoing aortic valve replacement (AVR) is still controversial.² There have been at least 2 historical randomized studies in which BPs and MPs were compared. However, the data are unfortunately not applicable to the current situation because the prosthetic valves studied are no longer in clinical use.

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A recent randomization study consisted of 310 patients aged 55–70 years and disclosed a clear trend toward improvement in cardiac-related death with a MP.³ A registry report in the UK⁴ demonstrated that late survival with a MP might be superior to that with a BP among 41,227 patients. That report also showed increased use of BP: 65% in 2004–2005 vs. 78% in 2008–2009.

During the recent decade, there have been some concerns over complications secondary to warfarin anticoagulation. Even younger patients want to have a BP because of fear of bleeding. Another drive toward BPs emerged from the valve-in-valve transcatheter AVR technique becoming an optional treatment for structural valve failure of a BP. The market share for MPs has shrunk throughout in contrast to that of BPs.

In a retrospective comparative study in this issue of the Journal,⁴ as the MPs, CarboMedics valves, St. Jude Medical valves, and ATS valves were used, and Carpentier-Edwards Perimount pericardial valves were solely used as the BP. In patients older than 70 years, both the actuarial survival rate and freedom from valve-related morbidity were greater in the BP group. Among the patients who were 60–69 years old at surgery, anticoagulant-related complications occurred less often in the BP group but there was no significant difference in long-term survival. In patients who were younger than 60 years old, long-term survival was significantly better in the MP group than in the BP group, but freedom from anticoagulant-related complications was similar.

The guidelines published by the Japanese Circulation Society recommend the use of BP for patients 65 years of age or older if the patient does not have risks of thromboembolism, and for younger patients with normal in normal sinus rhythm who agree to the risk of reoperation. The European Society of Cardiology guidelines state that the use of BP is reasonable in patients older than 65 years old. As for patients between 60 and 65 years old, either type of valve can be used after careful analysis of factors other than age. The new guideline of the American Heart Association recommends BP for patients of any age in whom anticoagulant therapy is a contraindication. MPs are a reasonable choice for AVR in patients less than 60 years of age unless they do not have a contraindication to anticoagulation. On the other hand, use of BPs is reasonable in patients more than 70 years old. Either a BP or MP can be used in patients aged between 60 years and 70 years of age. Numerous studies have revealed that the incidence of structural deterioration of BPs and the necessity of redo-surgery are less common in the elderly population. In patients older than 70 years of age, the likelihood of primary structural deterioration of a BP at 15 or 20 years is only 10%. The durability of the BP exceeds the expected years of life of elderly patients. There is also the advantage of avoiding anticoagulant therapy in this age group, which exceeds the possibility of redo-surgery because of structural deterioration of the BP. However, in meta-analyses or propensity score-matched comparisons of the use of MP or BP for AVR in patients younger than 60 years of age, those with a MP have lower mortality rates (HR, 0.234) and better survival despite similar occurrence of valve-related complications (Table).^5–16

Table. Comparative Study of Cardiac Valve Prostheses: Biological or Mechanical

Author	Study design	Patient group	Outcome	Key results	Comments
Brennan et al, Jacksonville3	Cohort study with STS ACSD	39,199 patients (aged 65–80 years) 605 centers; BP (n=24,410); MP (n=14,789); Mean follow-up 12.7 years	All-cause mortality; Reoperation; Endocarditis; Stroke; Bleeding	BP=MP (BP: 70.5% vs. MP: 60.3%) HR 1.04 (1.01–1.07); BP>MP (BP: 5.2% vs. MP: 2.3%) HR 2.55 (2.14–3.03); BP>MP (BP: 2.2% vs. MP: 1.4%) HR 1.60 (1.31–1.94); BP<MP (BP: 13.8% vs. MP: 14.7%) HR 0.87 (0.82–0.93); BP<MP (BP: 15.5% vs. MP: 21.8%) HR 0.66 (0.62–0.70)	Bioprostheses patients aged 65–69 years had substantially elevated 12-year absolute risk of reoperation (10.5%); Risks varied as a function of patient’s age and comorbidities
Badhwar et al, San Diego5	Retrospective with propensity matching	*55 patients underwent MVR (BP: 17, MP: 38); 172 patients: MP older than BP (P<0.01), mean follow-up 4.0 years; BP (n=103) CEP, Mosaic, mean age 58.6±8.8; MP (n=69) On-X, mean age 52.7±9.8	*INR target of 2.0 for MP, late death/patient- year; Thromboembolic complication rates per patient-year; Late bleeding	BP>MP (BP: 2.35% vs. MP: 1.41%); BP=MP (BP: 0.78% vs. MP: 0.77%, P=0.67); No events occurred	Postoperative liberalized mortality benefit of MP was observed as early as 5 years, reaching significance at 7.5 years (P=0.04); Patients aged ≤65 years with MP and closely monitored anticoagulation displayed non-inferiority to BP for bleeding and thromboembolic complications
Weber et al, Berne6	Retrospective with propensity matching	AVR ≤60 years old; Study group, BP (CEP) (n=103); Control group, MP (St. Jude, ATS) (n=103) with propensity matching; Mean follow-up 33±24 months; Mean echocardiographic follow-up 21.8±19.8 months	Overall survival; Freedom from all valve- related complications; Freedom from reoperation; (Echocardiographic outcome) Mean transvalvular aortic gradient; Peak transvalvular aortic gradient; Left ventricular mass regression; Effective orifice area	BP<MP, BP: 90.3% vs. MP: 98%, P=0.038, HR 0.243 (0.054–0.923); BP=MP, BP: 54.5% vs. MP: 51.6%, P=NS; BP=MP, BP: 100% vs. MP: 98%, P=0.231; BP>MP, P=0.05, BP: 11.2±4.2 mmHg vs. MP: 10.2±6.0 mmHg; BP>MP, P=0.03, BP: 19.9±6.7 mmHg vs. MP: 16.7±8.0 mmHg; BP=MP, P=0.056, BP: 126.5±38.5 g/m2 vs. MP: 118.5±24.9 g/m2; BP<MP, P=0.024, BP: 0.876±0.2 cm2/m2 vs. MP: 1.11±0.4 cm2/m2	Younger than 60 years, BP replacement was associated with reduced mid-term survival compared with survival after MP replacement; Despite similar valve-related event rate, better hemodynamic performance of MP; Transcatheter valve-in- valve intervention as potential treatment of BP degeneration should not be considered the sole bailout strategy for younger patients
Almeida et al, Porto Alegre7	Retrospective	301 patients, mean age 61.4±12.9, *BP>MP P<0.001; BP (n=143, 47.5%) mean age 65.1±11.9, Bicor (n=70), Flumen (n=55), Bioval (n=14), Braile Biomedica (n=4); MP (n=158, 52.5%) mean age 58.0±12.9, St. Jude (n=117), Carbomedics (n=25), Sorin (n=16); Mean follow-up 9.2±4.8 years	All-cause mortality (5, 10, 15 years, %); Free of reoperation (5, 10, 15 years, %); Free of bleeding	BP=MP, P=0.939, BP: 89.3, 70.4, 58.4 vs. MP: 83.9, 70.4, 58.4; BP=MP, P=0.057, BP: 94.6, 91.0, 83.3 vs. MP: 97.9, 95.8, 95.8; BP>MP, P=0.047, BP: 98.6, 97.8, 97.8 vs. MP: 94.5, 91.7, 91.7	Mortality was similar in the groups; Patient characteristics at baseline were a major determinant of late mortality after surgery; Tendency toward reoperation in the BP group; Patients with MP had more bleeding events over time
Ashikhmina et al, Rochester8	Retrospective with propensity matching	≥70 years of age, *subanalysis, 229 pairs of propensity- matched patients	Late survival (5, 10, 15 years, %)	BP=BP, P=0.81 (BP: 71%, 45%, 7% vs. MP: 67%, 49%, 19%)	Insufficient evidence that valve type affected survival
Dunning et al, Middleborough9	Registry with Great Britain and Ireland audit database	41,227 patients (5-year time period); Mean follow-up 2.5 years, *looked at changes in practice over time (2004–2009)	(2004–2005, 2008–2009) Hospital mortality; HR for decreased out-of-hospital mortality, if MP used; Annual number; Mean age, octogenarians; BP <55, 55–60, 60–65, 65–70, >70 years	4.1% (4.4–3.7%), BP<MP (BP: 4.5% vs. 3.1%, P<0.005), HR 1.46 (1.35–1.57); 7,396–9,333 patients; 68.8–70.2 years (13.6–18.4%); 65.4–78.8% (18–25%, 23–38%, 37–55%, 62–78%, 87–91%)	Increase in the proportion of BPs inserted in all age groups; On multivariate analysis there was na increased odds of out- of-hospital mortality with BP
Stassano et al, Naples10	Randomized cohort	310 patients, randomized to received BP or MP, aged 55–70 years; BP (n=155), SAV (n=93), CEP (n=62); MP (n=155), St. Jude (n=107), Carbomedics (n=48); Mean follow-up 106±28 months	Perioperative death; 13-year mortality (%), overall, cardiac-related, valve-related; Valve failures (%); Reoperation (%); MAPE (%)	BP=MP (BP: 3.9% vs. MP: 2.6%, P=0.4); BP=MP, BP: 30.6% vs. MP: 27.5% (P=0.6), BP: 21.7% vs. MP: 16.7% (P=0.3), BP: 28.6% vs. MP: 23.4% (P=0.8); BP>MP (BP: 2.17% vs. MP: 0%, P=0.0001); BP>MP (BP: 2.32% vs. MP: 0.62%, P=0.0003); BP=MP (BP: 28.6% vs. MP23.4%, P=0.4)	At 13 years, both MP and BP had a similar survival rate, as well the same rate of occurrence of thromboembolism, bleeding, endocarditis, and MAPE; Patients with BP valves faced a significantly higher risk of valve failure and reoperation
Geldorp et al, Rotterdam11	Cohort	3,934 patients; BP (n=2,860), CE porcine (56.5%), CEP (23.0%), Mosaic (20.5%), mean age 70 years, mean follow- up 6.1 years; MP (n=1,074), St. Jude (53.3%), Carbomedics (46.7%), mean age 58 years, mean follow-up 8.5 years	(60-year-old man) Simulated life expectancy; Event-free life expectancy; Reoperation-free life expectancy; Lifetime risk of reoperation (%); Lifetime risk of bleeding (%)	BP=MP (BP: 11.9 years vs. MP: 12.2 years); BP=MP (BP: 9.9 years vs. MP: 9.3 years); (BP: 10.5 years vs. MP: 11.9 years); BP: 25% vs. MP: 3%; BP: 12% vs. MP: 41%	Even for patients aged 60 years, event-free life expectancy is better with a BP; Chance of reoperation is higher, the lifetime risk of bleeding is lower compared with MP
Vicchio et al, Naples12	Retrospective	Octogenarians underwent AVR (n=160), mean age 82.3±2.3 years; *BP group was older (P=0.003); *MP for patients with life expectancy >10 years; BP (n=62), mean age 82.9±2.7 years; MP (n=98), mean age 81.8±1.8 years	Hospital mortality; Actuarial survival rate (1, 3, 5, 8 years, %); Freedom from valve- related complications (8 years)	8.8%, BP=MP (BP: 10.3% vs. MP: 7.6%, P=0.75); BP<MP (P=0.025), BP: 86.4%, 76.9%, 58.1%, 46.5% vs. MP: 91.3%, 88.6%, 81.6%, 70%; BP=MP (BP: 82.6% vs. MP: 87%, P=0.55)	Long-term survival after AVR in selected octogenarians was similar to that of the general elderly population; Device type exerted no influence on NYHA QOL scores
Silberman et al, Jerusalem13	Retrospective	352 patients, *BP group was older than MP; BP (n=163), mean age 71±11 years, Hancock II (n=35), CEP (n=25), Mitroflow (n=1), *stentless valve (n=102); MP (n=189), mean age 65±13 years, St. Jude (n=117), Hall (n=40), Bicarbon (n=27), ATS (n=3), Carbomedics (n=2); Mean follow-up 61±40 months	Operative mortality; Long-term survival (3, 5, 10 years, %); Event-free survival (3, 5, 10 years, %); Bleeding; Reoperation	6.8%, no difference; BP=MP (BP: 90%, 86%, 71% vs. MP: 92%, 86%, 69%, P=NS); BP=MP (BP: 79%, 68%, 44% vs. MP: 79%, 68%, 41%, P=NS); BP<MP (BP: 0.6% vs. MP: 4%, P=0.03); BP=MP (BP: 2.7% vs. MP: 3.7%, P=NS)	*102 stentless valves in BP group; Survival was better for the MP and stentless groups in comparison with the stent group; Survival and event-free survival similar for patients receiving a MP or BP
Brown et al, Rochester14	Retrospective with propensity matching	440 patients (age 50–70 years), *BP was 0.9 years higher than MP (P<0.1); BP (n=220) CEP, mean age 66.6 years, follow-up 8.6 years; MP (n=220) St. Jude, mean age 65.7 years, follow-up 6.3 years	Perioperative mortality; Overall survival (5, 10 years); Freedom from reoperation; Late stroke, other embolic events and endocarditis; Hemorrhagic complication; Adjusted risk for late mortality	BP>MP (BP: 5.5% vs. MP: 1.8%, P=0.04); BP<MP (BP: 72%, 50% vs. MP: 87%, 68%, P<0.1); BP=MP (BP: 91% vs. MP: 98%, P=0.06); BP=MP; BP<MP (BP: 7% vs. MP: 15%, P=0.01); MP<BP HR 0.46 (P<0.01)	Aged 50–70 years with MP had survival advantage relative to matched patients who received BP
Schelbert et al, lowa15	Cohort	307,054 patients (aged ≥65 years), *BP was older than MP (77 vs. 75 years, P<0.001); BP (n=111,151), MP (n=195,903)	Death (HR of BP); Readmission for hemorrhage, stroke or embolism; Reoperation-free survival; Reoperation	BP<MP (BP: 10.0% vs. MP: 9.6%, P<0.001); HR 0.97 (0.95–0.98); BP<MP (BP: 4.0% vs. MP: 4.2%, P<0.001); HR 0.90 (0.88–0.92); BP<MP (BP: 10.3% vs. MP: 9.8%, P<0.001); HR 0.97 (0.96–0.98); BP>MP (BP: 0.33% vs. MP: 0.31%, P=0.03); HR 1.25 (1.16–1.35)	In older patients, BP recipients had slightly lower risks of death and complications, but higher risk of reoperation
Ruel et al, Ottawa16	Cohort	*Study contained both AVR and MVR patients, focusing on AVR (n=314) data Age ≤60 years; BP (n=170), Ionescu- Shiley (n=136), Hancock (n=24), Homograft (n=8), CEP (n=2); MP (n=144), Harken (n=67), Lillehei Kaster (n=31), Hall (n=22), St. Jude (n=17), Carbomedics (n=5), Bjork- Shiley (n=2); Mean follow-up 24.0±3.1 years	Survival (20, 25 years, %); Freedom from reoperation (at 20 years); Freedom from death attributable to ischemic or hemorrhagic stroke (at 20 years)	BP=MP (BP: 65.5%, 51.7% vs. MP: 52.3%, 41.2%, P=NS); BP<MP (BP: 11.4% vs. MP: 73.0%, P<0.001), HR 3.9 (2.6–6.3); BP>MP (BP: 97.9% vs. MP: 83.9%), HR 7.0 (P<0.02) *HR of MP use	Independent risk factors for mortality were age, coronary disease, atrial fibrillation, and earlier year of surgery; Use of BP vs. MP at initial implantation was not associated with a significant difference in long-term survival, despite higher reoperation rates with BP; MP may not necessarily be warranted in the younger adult patient

AVR, aortic valve replacement; BP, bioprosthesis; CEP, Carpentier-Edwards Perimount; MAPE, major adverse prosthesis-related events; MP, mechanical prosthesis; MVR, mitral valve replacement; QOL, quality of life; HR, hazard ratio.

Analyzing their study group by age, Weber et al reported that 20-year survival was better with MPs in patients younger than 60 years old.⁷ Contrary to that, Ruel et al¹⁶ reported no significant difference in terms of 25-year survival in patients younger than 60 years old. They also stated that freedom from reoperation was significantly worse with BPs than with MPs, and that freedom from life-threatening bleeding and embolic events was worse with MPs than with BPs in the same age groups.

As for the elderly patients, Brennan et al reported that long-term survival after AVR was similar between the BP and MP patients aged 65–80 years.⁵ Quite contrary to the current study’s results, Vicchio et al reported that 5-year survival was inferior in patients who had BPs than in those who had MPs, despite freedom from valve-related complications being similar in both groups.¹¹

With respect to the cause of death, this analysis reported that in the case of redo-operation, hospital mortality was 3.0% for the BP group, and the rate of life-threatening bleeding/embolic events among those with MPs was 1.9%. Badhwar et al⁶ reported that both types of prosthesis showed no difference in the rate of late thromboembolic events. The long-term survival rate was similar in both groups. In patients aged 65 years or younger with a MP, a closely monitored anticoagulation displayed non-inferiority to BP for bleeding and thromboembolic complications.

From the reports published after 2005, we have not found a unanimous conclusion regarding selection of MP or BP in the aortic position. However, daring to take the risk of roughly summing up, BPs have a higher risk of reoperation than MPs, but there is less possibility of bleeding/embolism events than with MPs.

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