Effectiveness of different anticalcification treatments for stentless aortic bioprostheses

Glycidyl methacrylate-crosslinked fish swim bladder as a novel cardiovascular biomaterial with improved antithrombotic and anticalcification properties

At present, commercial artificial biological valves are mostly prepared by crosslinking bovine or porcine pericardia with glutaraldehyde. Swim bladder has similar components and lower immunogenicity compared to bovine or porcine pericardium. In this study, we used a glycidyl methacrylate (GMA)-based radical polymerization method to crosslink decellularized swim bladders. Amino and carboxyl groups in the swim bladder were reacted with epoxy groups on GMA to introduce carbon-carbon double bonds to the swim bladder. The results showed that the platelet adhesion of GMA-crosslinked swim bladders (GMA-SBs) decreased by 35%, as compared to that of glutaraldehyde-crosslinked swim bladders (GLUT-SBs). Moreover, the superior anticoagulant property was further verified by the ex vivo arteriovenous shunt assay. Meanwhile, the subcutaneous implantation in rats showed that GMA-SBs were able to effectively inhibit the calcification compared with GLUT-SBs. In conclusion, GMA-SBs showed improved antithrombotic and anticalcification properties compared to GLUT-SBs.

Stentless valves treated by the L-hydro process in the aortic position in sheep

Calcification of glutaraldehyde-treated bioprosthetic heart valves is a major cause of long-term failure. We studied porcine aortic valves treated by the L-Hydro process and implanted into 14 juvenile sheep (group 1). Another 10 sheep were implanted with glutaraldehyde-treated porcine bioprostheses (group 2). The animals were sacrificed after 150 days and the explanted valves were analyzed for calcification. Hemodynamic measurements by echocardiography and angiography were carried out prior to sacrifice. Macroscopic analysis showed calcification and loss of mobility of the leaflets in all group 2 implants and in one group 1 implant. Light microscopy showed foci of calcification in all group 2 implants and in 3 valves from group 1. A significant reduction in the level of calcification was found in porcine bioprostheses treated by the L-Hydro process and implanted into the juvenile sheep model.

Hemodynamic performance of the Medtronic Mosaic porcine bioprosthesis up to ten years

BACKGROUND

The Mosaic bioprosthesis (Medtronic, Minneapolis, MN) is a third-generation stented porcine bioprosthesis combining physiologic fixation and amino oleic acid antimineralization treatment to improve hemodynamic performance and durability. The findings of this single-center experience with this valve were evaluated to determine the clinical and hemodynamic performance.

METHODS

Between February 1994 and October 1999, we enrolled 255 patients with aortic valve replacement (AVR) with a mean age of 67 years (range, 23 to 82 years) and 47 patients with mitral valve replacement (MVR) with a mean age of 67 years (range, 41 to 84 years) in this post-United States Food and Drug Administration approval prospective and nonrandomized clinical trial. Patients were followed-up, including serial echocardiographic assessment, within 30 days, at 6 months, and annually thereafter. The cumulative follow-up was 1540 patient-years for AVR (mean, 6.1 years; maximum, 10 years) and 250 patient-years for MVR (mean, 5.4 years, maximum; 10 years).

RESULTS

Early mortality after AVR (<30 days) was 0.8%; late mortality per patient-year was 3.5%, including a valve-related/unexplained mortality of 1.1%. Early mortality after MVR (<30 days) was 0.0%; late mortality per patient-year was 2.8%, including a valve-related/unexplained mortality of 1.2%. Median postoperative gradient and effective orifice area for all valves after AVR were (early, n = 252; 5 years, n = 161; 9 years, n = 43) 13.7, 12.3, and 11.7 mm Hg and 1.9, 1.8, and 1.8 cm2 at early, 5 years, and 9 years, respectively. With MVR respective data were (early, n = 46; 5 years, n = 25; 7 years, n = 13) 4.6, 4.1, and 3.9 mm Hg and 1.8, 2.2, and 2.3 cm2. At 10 years, freedom from adverse events in the AVR group and MVR group was, respectively, thromboembolism, 86.6% +/- 6.6% and 86.3% +/- 9.8%; permanent neurologic event, 91.2% +/- 6.8% and 90.9% +/- 8.7%; valve thrombosis, 98.2% +/- 0.8% and 100%; structural valve deterioration, 87.1% +/- 6.7% and 100%.

CONCLUSIONS

Our midterm results demonstrate clinical safety and good performance of the Mosaic bioprosthesis. Continued follow-up will determine if this new design will provide increased durability.

Clinical Experience With Stentless Mitral Valve Replacement

BACKGROUND

Our aim is to describe the clinical experience with stentless mitral valve (SMV) replacement with special focus on the functionality of the SMV.

METHODS

Fifty-two patients (68 +/- 8.5 years old; 36 female) have been prospectively evaluated since August 1997. The chordally supported SMV (Quattro) was implanted for mitral stenosis (n = 26), severe incompetence (n = 17), or mixed lesion (n = 9). Preoperative New York Heart Association class was 3.1 +/- 0.6. Twenty patients received additional intraoperative ablation therapy. Mean follow-up is 37.3 +/- 18.7 months (range, 1 to 65).

RESULTS

Surgery was performed using conventional sternotomy (33) or anterolateral minithoracotomy (19). Atrial rhythm was reestablished in 17 of 20 patients. Six patients operated on early in this series required reoperation, 2 for paravalvular leakage, 2 for functional stenosis, 1 with pannus formation due to underlying rheumatoid disease, and 1 for papillary flap rupture after 5.1 years. Mortality was 1 perioperative (1.9%, nonvalve related) and 1 after reoperation due to multiorgan failure. During late follow-up (30 +/- 7 months postoperatively) 5 patients died of noncardiac causes. Regular echocardiographic control revealed good SMV function (maximum transmitral blood flow velocity 1.7 +/- 0.2 m/s; mean transmitral pressure gradient 3.9 +/- 1.2 mm Hg) and well-preserved ejection fraction postoperatively as well as at most recent follow-up.

CONCLUSIONS

The clinical experience after 5.5 years of SMV implantation is promising. Preservation of annuloventricular continuity is advantageous. However, long-term durability remains to be proved.

Prevention of Calcification of Bioprosthetic Heart Valve Cusp and Aortic Wall With Ethanol and Aluminum Chloride

BACKGROUND

Calcification is frequently associated with device failure of bioprostheses fabricated from either glutaraldehyde pretreated porcine aortic valves or bovine pericardium. It was hypothesized that differential pretreatment with ethanol-aluminum chloride will prove safe and efficacious for inhibiting the calcification of both the porcine aortic valve bioprosthetic cusp and the aortic wall.

METHODS

Glutaraldehyde-fixed porcine aortic valves were subjected to differential aluminum chloride (AlCl3) and ethanol pretreatment; aortic wall segments were treated exclusively with AlCl3 (0.1 moles/L) for 45 minutes, 6 hours, or 8 hours (groups 3A, B, and C, respectively), followed by valve cusp incubations in ethanol (80%, pH 7.4). Nontreated control bioprosthetic valves were either stent-mounted porcine aortic valve bioprostheses (Carpentier-Edwards, group 1) (Edwards, Santa Anna, CA) or St. Jude Toronto SPV valves (St. Jude Medical, St. Paul, MN) (group 2). Mitral valve replacements were carried out in juvenile sheep for 150 days.

RESULTS

Calcium in cusps from group 3A was 2.84 +/- 0.62 mg calcium/g tissue versus control, 22.79 +/- 8.46 mg calcium/g tissue, p = 0.04. Valves pretreated with AlCl3 for 45 minutes, 6 hours, and 8 hours had significantly lower levels of calcium in the aortic wall compared to controls (40.38 +/- 5.66, 26.77 +/- 4.02, and 28.94 +/- 8.25 mg calcium/g tissue for groups 3A, 3B, and 3C, respectively, vs 95.47 +/- 17.14 mg calcium/g tissue for group 1, p < 0.001, and 133.42 +/- 3.96 mg calcium/g tissue for group 2, p < 0.001).

CONCLUSIONS

Differentially applied ethanol and aluminum chloride pretreatment significantly inhibited calcification of both the glutaraldehyde-fixed porcine aortic valve bioprosthetic cusp and the aortic wall.

Midterm results after stentless mitral valve replacement

BACKGROUND

To analyze the midterm clinical results after stentless mitral valve (SMV) replacement.

METHODS AND RESULTS

Fifty one patients (68.3+/-8.4 years, 35 female) with severe mitral valve disease (stenosis 25, incompetence 17, mixed lesion 9) received a chordally supported SMV (Quattro, St. Jude Medical Inc.) since August 1997. Preoperative New York Heart Association class was 3.1+/-0.6; left ventricular ejection fraction 64+/-13%, and cardiac index 2.1+/-0.8 l/min/m2. Additional intraoperative ablation therapy was performed on 19 patients with chronic atrial fibrillation. Mean follow-up is 35.4+/-19.2 months (range 5 to 63). SMV implantation was performed using a conventional (32) or a minimally invasive (19) approach, valve size was 29+/-1.5 mm, cross-clamp duration was 81+/-33 minutes. Atrial rhythm was reestablished in 16 of 19 patients. Five patients required reoperation early in this series, two for paravalvular leakage, two for functional stenosis, and one with underlying rheumatoid disease. Mortality was one perioperative (1.96%, non-valve-related), one after reoperation as a result of multiple organ failure (MOF), and five during late follow-up (30+/-7 months postoperatively) for noncardiac causes. Regular echocardiographic control revealed good SMV function (Vmax 1.7+/-0.2m/s, P(mean) 3.9+/-1.2 mm Hg) and well-preserved ejection fraction postoperatively and at most recent follow-up.

CONCLUSIONS

Midterm results after SMV implantation are promising. Preservation of the annuloventricular continuity leads to stable left ventricular function and combined with ablation therapy to physiological hemodynamics. Long-term durability remains to be proven.