Selection of the prosthesis for aortic valve replacement: mechanical or bio?

To clarify the effect of the valve selection on the patients' prognosis, long-term outcome of the patients undergone isolated aortic valve replacement (AVR) with the mechanical or bioprosthetic valve in our institution were investigated. In protocol 1, patients of all ages with isolated AVR (n = 472, composed of 166 who received a bioprosthesic valve [group B] and 306 who received a mechanical valve [Group MI) between 1975 and 2004 were investigated. In protocol 2, primary AVR patients aged 50-65 years (n = 184, composed of 47 in group B and 137 in group M) were compared. There were no significant differences in freedom from cardiac death, freedom from bleeding, and freedom from endocarditis in Protocols 1 and 2. Significantly fewer redo AVRs were required in group M in both protocols 1 and 2. However, group M was significantly worse in terms of freedom from thromboembolism in protocol 2. As a result, group M was superior to group B in freedom from valve-related events when redo AVR included. When redo AVR was excluded, there was no difference between the two groups in freedom from valve-related events in both protocols 1 and 2. There may thus be an advantage in selecting bioprosthetic valves in young adult patients who required AVR if they accepts the possibility of redo AVR in future.     

Is a stentless aortic valve superior to conventional bioprosthetic valves for aortic valve replacement?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether a stentless valve is superior to conventional stented valves when tissue aortic valve replacement is performed. Altogether more than 515 papers were found using the reported search, of which 16 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. We conclude that stentless valves allow a larger effective orifice area valve to be implanted with a lower mean and peak aortic gradient postoperatively. At six months several studies and a meta-analysis have shown superior left ventricular mass regression in the stentless valve groups. However, by 12 months the stented valve groups catch up in terms of mass regression and this significance disappears. So the 'eminent speaker from the floor', was right with his statement, that there have been no definitively proven benefits for stentless valves.     

Aortic valve replacement: is the stentless xenograft an alternative to the homograft? Midterm results.

BACKGROUND: This study was performed to assess the midterm clinical results after aortic valve replacement (AVR) with stentless xenograft (SX) compared with cryopreserved aortic or pulmonary homografts (HX). METHODS: In 139 patients (<60 years) undergoing elective AVR, 59 HX and 80 SX were inserted. All patients were followed clinically and by color flow Doppler echocardiography for 45+/-12 months (range 31-58 months). RESULTS: There were 5 in-hospital deaths (3.5%): 4 HX and 1 SX (p = NS). The mean gradient was 6+/-2 mm Hg in HX versus 13+/-6 mm Hg in SX (p<0.001) and remained unchanged during follow-up. Actuarial survival (HX 77%, SX 80%), freedom from endocarditis (HX 91%, SX 99%), freedom from thromboembolic events (HX 98%, SX 90%), and freedom from reoperation (HX 98%, SX 100%) were comparable between groups after 58 months. CONCLUSIONS: Despite slightly higher transvalvular gradients, the stentless aortic valve achieved excellent midterm results, when compared with homografts.     

Aortic valve replacement in children: are mechanical prostheses a good option?

OBJECTIVE: The choice of the most appropriate substitute in children with irreparable aortic valve lesions remains controversial. The aim of this study was to assess early and late outcomes following aortic valve replacement (AVR) with mechanical prostheses in children. PATIENTS: Fifty-six patients (42 male, 14 female, mean age 11.2, range 1-16 years) undergoing AVR with mechanical prostheses between October 1972 and January 1999 were evaluated. Thirty-six patients (64.2%) underwent previous cardiac surgery. Disease aetiology was congenital in 47 patients (congenital aortic stenosis in 33, and other congenital abnormalities in 14) (83.9%), infective in four (7. 1%), rheumatic in two (3.4%), and three (5.3%) had connective tissue disorders. Haemodynamic indication for AVR was aortic regurgitation (AR) in 24 (42.8%), aortic stenosis (AS) in 22 (39.2%) and mixed disease in ten (17.8%). Twenty-eight patients (50.0%) were in New York Heart Association (NYHA) class III-IV before surgery. Concomitant procedures were performed in 31 patients (55.3%), including aortic root enlargement in 28 (50%). The mean size of implanted valves was 22.4 mm (range 17-27 mm). All patients received long-term anticoagulation treatment with sodium warfarin, aiming to maintain an international normalized ratio (INR) between 2.5-3.0. The mean follow-up was 7.3 years (range 0-26, total 405 patient-years). RESULTS: Operative mortality was 5.3% (three patients). Three patients developed complete heart block requiring pacing, two of them permanently. Late events included valve thrombosis (one), transient stroke (one), paravalvular leak of a mitral prosthesis (one), aneurysm of sinus of Valsalva (one) and pannus ingrowth (one). There was no major haemorrhagic event. Five patients required re-operation (8.9%), but none due to outgrowth of the valve. Regarding actuarial freedom from thrombo-embolism, any valve-related event and re-operation at 20 years was 93, 86.6 and 86. 4%. There were three late deaths. Actuarial survival, including operative mortality, at 10 and 20 years was 91 and 84.9%. The actuarial survival for the group of the patients with congenital AS (n=33) at 10 and 20 years was 93.5%, whereas for the children with other congenital heart problems (n=14) this was 85.7 and 64.3% (P=0. 09). At the latest clinical evaluation, 44 children were in NYHA class I and six were in class II. The mean gradient across the aortic prosthetic valve on echocardiography was 17.9 mmHg (range 0-47 mmHg). CONCLUSIONS: Mechanical AVR, with enlargement of the aortic root if necessary, remains an excellent treatment option in children. It is associated with acceptable operative mortality, low incidence of late events and re-operation, and provides good long-term survival. It clearly represents a good alternative to available biological substitutes, including the pulmonary autograft (Ross procedure).     

Do heart valve bioprostheses degenerate for metabolic or mechanical reasons?

Although heart valve bioprostheses provide a normal quality of life, their durability is still of great concern. Their durability failure is defined as "degeneration," which is considered to be a consequence of metabolic factors. In this study, we demonstrate that mechanical and design factors can also be responsible for bioprosthesis failure. Large numbers of porcine and pericardial bioprostheses were tested in a fatigue-testing system in which the test conditions were proved to be reproducible and accurate by a laser Doppler anemometer. The results have allowed us to define causes of failure, previously insufficiently stressed, in each type of valve tested. There is a clear difference in factors influencing tissue disruption between porcine and pericardial valves. We have compared these in vitro results with in vivo clinical findings. The main inferences are as follows: (1) Bioprostheses rupture and fail in the same fashion in both in vitro and in vivo studies. (2) Mechanical and design factors are involved in tissue failure. (3) The in vitro/in vivo durability ratio is not 1:1. This ratio depends on the test conditions. (4) Pericardial valves fail because of damage during closure, whereas porcine valves are damaged during both opening and closing (mostly opening) because of design features. (5) Once one cusp fails and prolapses, the other cusps will fail in an accelerated fashion. (6) In vitro durability of 100 X 10(6) cycles can be considered excellent and is an achievable goal. (7) Variability is the key impediment to predicting the durability of bioprostheses. Valves can fail within 2 to 3 million cycles or can last more than 100 million cycles. Similarly, bioprostheses may require explantation within a few months or can last 10 to 13 years in patients. (8) Fatigue testing is an excellent and valuable tool to elucidate the mechanical factors responsible for this variability.     

Polyurethane: material for the next generation of heart valve prostheses?

OBJECTIVES: The prospects for a durable, athrombogenic, synthetic, flexible leaflet heart valve are enhanced by the recent availability of novel, biostable polyurethanes. As a forerunner to evaluation of such biostable valves, a prototype trileaflet polyurethane valve (utilising conventional material of known in vitro behaviour) was compared with mechanical and bioprosthetic valves for assessment of in vivo function, durability, thromboembolic potential and calcification. METHODS: Polyurethane (PU), ATS bileaflet mechanical, and Carpentier-Edwards porcine (CE) valves were implanted in the mitral position of growing sheep. Counting of high-intensity transient signals (HITS) in the carotid arteries, echocardiographic assessment of valve function, and examination of blood smears for platelet aggregates were undertaken during the 6-month anticoagulant-free survival period. Valve structure and hydrodynamic performance were assessed following elective sacrifice. RESULTS: Twenty-eight animals survived surgery (ten ATS; ten CE; eight PU). At 6 months the mechanical valve group (n=9) showed highest numbers of HITS (mean 40/h, P=0.01 cf. porcine valves), and platelet aggregates (mean 62.22/standard field), but no thromboembolism, and no structural or functional change. The bioprosthetic group (n=6) showed low HITS (1/h) and fewer aggregates (41.67, P=1.00, not significant), calcification and severe pannus overgrowth with progressive stenosis. The PU valves (n=8) showed a small degree of fibrin attachment to leaflet surfaces, no pannus overgrowth, little change in haemodynamic performance, low levels of HITS (5/h) and platelet aggregates (17.50, P<0.01 cf. mechanical valves, P=0.23 cf. porcine valves), and no evidence of thromboembolism. CONCLUSIONS: In the absence of valve-related death and morbidity, and retention of good haemodynamic function, the PU valve was superior to the bioprosthesis; lower HITS and aggregate counts in the PU valve imply lower thrombogenicity compared with the mechanical valve. A biostable polyurethane valve could offer clinical advantage with the promise of improved durability (cf. bioprostheses) and low thrombogenicity (cf. mechanical valves).     

Are bicuspid aortic valves a limitation for aortic valve repair?

Objective: To compare the mid-term results after aortic valve (AV) repair in bicuspid AVs with those in tricuspid AVs. Methods: Between 2000 and 2010, 100 patients (mean age 47.2 years) underwent AV repair procedures for insufficient bicuspid AV (n = 43) and tricuspid AV (n = 57). Aortic regurgitation (AR) more than moderate was present in 31/43 and 21/57 patients in the bicuspid AV and the tricuspid AV group, respectively. Concomitant root replacement by either the reimplantation or the remodeling technique was performed in 42 patients (bicuspid AV 17/43, tricuspid AV 25/57). All patients were prospectively studied with postoperative and further annual clinical assessment and echocardiography. Follow-up was 99% complete with a mean follow-up time of 22 months. Results: Three patients died during the initial hospitalization, all due to postoperative cardiac failure. Overall actuarial 3 years’ survival was 93 ± 4.2% without significant differences between the two groups. Overall actuarial 3 years’ freedom from AV-related reoperation was 86 ± 5.1% without significant differences between the groups (85 ± 9.7% for bicuspid AV, 86 ± 6.0% for tricuspid AV; log-rank test: p = 0.98). Overall actuarial 3 years’ freedom from recurrent AR ≥ moderate was 100% and AR > trace was 71.3 ± 8.2% without significant differences between the groups (76.5 ± 11.7% for bicuspid AV, 71.4 ± 9.4 for tricuspid AV; log-rank test: p = 0.97). Conclusions: The mid-term outcome in terms of survival, freedom from reoperation or recurrent AR is similar for both groups of patients after AV repair procedures. Therefore, we advocate valve repair also in patients presenting with an insufficient bicuspid AV.     

Is prophylactic aortic valve replacement indicated during mitral valve surgery for mild to moderate aortic valve disease?

BACKGROUND: Determining the need for surgical treatment of coexisting mild to moderate aortic valve disease in patients referred for mitral valve surgery is often difficult. The purpose of this study was to assess long-term clinical outcome and the need for subsequent aortic valve replacement in patients with mild to moderate rheumatic aortic valve disease at the time of mitral valve surgery. METHODS: A total of 275 patients (90 men and 185 women, mean age 43 years) with rheumatic disease who underwent mitral valve surgery were followed up for an average of 9 years. Patients were classified into two groups: those with coexisting mild to moderate aortic valve disease at the time of mitral valve surgery (141 patients, group A) and those without (134 patients, group B). Primary outcomes (death and subsequent aortic valve surgery) were compared between the two groups. RESULTS: At the time of mitral valve surgery, 104 patients (74%) in group A had mild aortic regurgitation, 37 (26%) had moderate aortic regurgitation, 5 had (4%) mild aortic stenosis, and 2 (1%) had moderate aortic stenosis. At the end of follow-up, no patient had severe aortic valve disease. In all, 12 patients (5%) in group A had primary events (eight deaths and four subsequent aortic valve replacements), and 12 patients (9%) in group B had such events (12 deaths). According to Kaplan-Meier analysis, neither the survival rate nor the event-free survival rate differed significantly over the follow-up period between the two groups. CONCLUSIONS: In most patients who have mild to moderate rheumatic aortic valve disease at the time of mitral valve surgery, the long-term outcome is comparable to that of subjects without aortic valve disease at the time of mitral valve surgery. Subsequent aortic valve replacement is rarely needed after a long follow-up period.