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ORIGINAL ARTICLE |
Department of Cardiothoracic Surgery John Radcliffe Hospital Oxford, UK
Ravi Pillai, FRCS Tel: +44 1865 220240 Fax: +44 1865 220244 Email: ravi.pillai{at}nds.ox.ac.uk, Department of Cardiothoracic Surgery, John Radcliffe Hospital, Headley Way, Headington, Oxford, OX3 9DU, UK.
ABSTRACT
Stentless aortic bioprostheses have been successfully used for over a decade. The 3f bioprosthesis is a new equine pericardial stentless valve, unique in its tubular design, preserving the native aortic sinuses post-implant. Forty-six consecutive aortic valve replacements with the 3f bioprosthesis were performed between June 2003 and January 2005. The patients were prospectively assessed and echocardiography was performed at 6 months, 12 months, and annually thereafter. The median follow-up was 2.1 ± 0.9 years. There was one early and 4 late deaths; none were valve-related. The 2-year mean transvalvular gradient was 8.8 ± 3.8 mm Hg, the mean echocardiographic aortic regurgitation grade was 0.4 ± 0.7 (grade 1 being trivial). Echocardiographic sizing of the aortic annulus before surgery accurately predicted prosthesis size. The 3f bioprosthesis is easy to implant. Early clinical results are favorable, with hemodynamic profiles consistent with those of other stentless prostheses. Longer follow-up is required to confirm its durability.
Key Words: Aortic Valve • Heart Valve Prosthesis Implantation
INTRODUCTION
The 3f aortic valve prosthesis (ATS Medical, Minneapolis, MN, USA) is a stentless equine pericardial valve. The model 1000 is made of 3 equal pieces of fixed equine pericardium, preserved in low-concentration glutaraldehyde, and sutured together to maintain a tubular structure with a thin polyester suture ring along its inflow aspect. The outflow orifice is supported by 3 commissural tabs at the distal junction of the leaflets. These tabs are sewn onto the patient’s aortic wall, thereby maintaining the tubular integrity of the prosthesis. Our experience to date has raised several points of technical interest, which could facilitate the safe implantation of this prosthesis and optimize its hemodynamic benefit.
PATIENTS AND METHODS
This prospective study was approved by the United Kingdom Medical Devices Agency and the ethics committee of the Oxford Radcliffe Hospitals NHS Trust. Patients with a congenitally abnormal aortic valve or dilated ascending aorta extending to the sinotubular junction were excluded. Forty-six consecutive aortic valve replacements with the 3f bioprosthesis were performed between June 2003 and January 2005, as part of the USA Food and Drug Administration approval study in Oxford. The median age of the patients was 74.6 ± 6.0 years (range, 60–81 years), and 34 (73.9%) were males. The median logistic EuroSCORE was 6.2 ± 6.6 (range, 1.8–31.1). The indication for valve replacement was calcified aortic stenosis in 43 (93.5%) patients, mixed degenerative disease in 2 (4.4%), and degenerative regurgitant aortic valve in one. Patients were assessed prospectively and followed up both clinically and echocardiographically at 6-monthly intervals for the first year and annually thereafter. Hemodynamic parameters on echocardiography included transvalvular gradients (mean and peak), degree of residual regurgitation, the valvular effective orifice area, and valvular effective orifice area indexed to body surface area. We also prospectively recorded the echocardiographically predicted prosthetic size for comparison with the intraoperatively measured aortic annulus and the actual size of the implanted prosthesis.
Drawing upon our experience with aortic homograft implantation as well as a wide spectrum of porcine stentless valves, we opted to use the technique of interrupted simple 4/0 Ethibond sutures for the proximal suture line (aortic annulus).1–5 The 3f prosthesis sewing ring is scalloped to mirror the coronet of the aortic annulus. Despite this, the proximal suture line in practice is orientated in a horizontal plane, with commissural sutures placed across the base of the commissural triangles. Cardiopulmonary bypass was established using an aortic cannula and a 2-stage venous cannula. The pericardial reflection at the top of the ascending aorta was divided to allow for distal aortic cannulation. The distal position of the aortic cannula provided ample room for application of the aortic crossclamp, facilitated retraction following aortotomy, and aided exposure. The heart was arrested with antegrade cold crystalloid cardioplegia. Routine cardiopulmonary bypass was maintained with moderate hypothermia, and the left ventricle was vented.
A partial transverse aortotomy distal to the sinotubular junction inline with the consistently found aortic fat pad is essential (Figure 1A
). The transverse incision was perpendicular to the direction of axial blood flow, taking into account the normal right laterally convex and anteroposterior curvature of the ascending aorta. The posterior end of the incision was slightly cranial for ease of aortotomy closure. The native valve leaflets were excised completely with total decalcification of the aortic annulus confirmed by finger palpation. The valve annulus was sized using the disc-shaped 3f valve sizers. It is imperative to avoid over-sizing. Should uncertainty arise, the smaller prosthesis should be implanted. Shoe-horning inappropriately large valves causes increases transvalvular gradient as well as regurgitation. Interrupted simple 4/0 Ethibond sutures were initially placed through the prosthetic sewing ring and passed along the left coronary annulus 3 mm apart, starting from the noncoronary cusp and left coronary cusp commissure (Figure 1B). This annular suture line was continued in a clockwise fashion. Annular sutures were then taken backhanded along the noncoronary annulus. The prosthesis was parachuted down before the outer holder was cut free (Figure 1C). The valve may be invaginated into the left ventricular outflow to ease tying-in. Upon completion, the prosthesis was evaginated and the commissural tabs orientated. The 120° commissural tab separation maintained by the inner holder is crucial to both the systolic and diastolic function of the valve. At this stage, the aorta was pulled cranially to compensate for the natural elastic recoil of the aortic root. This aided orientation and estimation of the appropriate height of the commissural tabs. We prefer to site the tab between the left coronary cusp and right coronary cusp first. The commissural tab was attached to the aortic wall using 2 vertical mattress sutures with a small Teflon pledget on the outer wall (Figure 1D). Excessive distal traction of these tabs was avoided because a taut cusp hinders the prosthetic leaflets from opening fully. Furthermore, leaflet apposition may be compromised as the aortic root fills, causing regurgitation. Postoperative antiplatelet therapy with aspirin 75 mg alone was used.
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RESULTS
Eighteen (39.1%) patients underwent concomitant coronary artery bypass grafting with 1.8 ± 0.8 (range, 1–3) grafts pre patient. The median aortic crossclamp and cardiopulmonary bypass times were 78.0 ± 9.5 min and 88.0 ± 20.7 min, respectively, for isolated valve replacement. Permanent pacemaker implantation was required in a patient with symptomatic bradycardia, and in another with complete heart block with sick sinus syndrome, which was planned for preoperatively. There were no other major operative complications. There was one (2.2%) early death and 4 further deaths after median follow-up of 2.1 ± 0.9 years; none were valve-related. The early death was due to multiorgan failure secondary to sepsis. Two of the late deaths were due to malignancy: a patient with cerebral glioma died after 3 months, and another with sigmoid cancer died at 17 months postoperatively. The other 2 deaths were due to bronchopneumonia with concomitant progressive pulmonary fibrosis associated with amiodarone, and chronic obstructive lung disease. The mean New York Heart Association functional class improved after 2 and 5 years of clinical follow-up: 1.18 ± 0.45 (n = 39), and 1.15 ± 0.37 (n = 20) compared to 2.28 ± 0.89 preoperatively (p < 0.001); 84.6% (33/39) of patients at 2 years, and 85% (17/20) at 5 years were in New York Heart Association functional class I. The mean echocardiographic follow-up was 2.0 ± 0.2 years (range, 1.8–2.9 years). Median 3f prosthesis size was 25 ± 2 mm (range, 21–29 mm). The mean transvalvular gradient was 8.9 ± 4.7 mm Hg at discharge, and 7.4 ± 3.4 mm Hg at 6 months. Forty patients completed the scheduled 2-year echocardiographic review; their mean systolic and diastolic arterial blood pressures were 133.6 ± 18.7 and 60.7 ± 10.7 mm Hg, respectively. Transvalvular pressure gradients were maintained at 2 years postoperatively, with improved effective orifice area and left ventricular mass regression (Table 1). Mean residual aortic regurgitation grade was 0.4 ± 0.7 (grading scale: 0 = none, 1 = trivial, 2 = mild, 3 = moderate, 4 = severe). Preoperative echocardiographic measurement of the aortic annulus correlated well with the actual implanted prosthesis size. Echocardiography underestimated the size by 1.1 ± 0.2 mm (p>0.05).
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The tubular design of the 3f aortic bioprosthesis replaces the native aortic cusps whilst preserving the native aortic sinuses. The role of diastolic flow vortices in the aortic sinuses in aortic leaflet closure and leaflet stress distribution has been well described.6–8 The benefits of the 3f prosthesis may be twofold: firstly the larger leaflet surface coaptation may explain the low incidence of central prosthetic regurgitation, and secondly the preserved aortic sinuses may reduce leaflet stresses.9 Predictability, this may contribute to long-term prosthetic durability. The larger leaflet coaptation surfaces may also afford a greater margin of error, particularly in patients with progressive sinotubular dilatation. Nevertheless, it remains critical that the 120° commissural tab separation be maintained at implantation.
The mean gradient across the valve was comparable to that of other stentless valves at the same stage of follow-up.3,10,11 This prosthesis behaves hemodynamically like other established stentless prosthesis, with a low transvalvular gradient and early left ventricular mass regression.12–16 Preoperative and intraoperative echocardiographic sizing of the aortic annulus (and hence the predicted prosthesis size) allowed us to anticipate the need for a higher aortotomy (well above the fat-pad line) in patients requiring a 27-mm or larger prosthesis. Our findings indicate that preoperative echocardiographic measurement of the aortic annulus diameter is accurate in predicting the prosthetis size, with insignificant differences amounting to less than one valve size. The ATS 3f valve is easy to implant and the early results are encouraging. The novel valve design with preservation of the normal functioning aortic root sinuses may have an impact on long-term function.
REFERENCES
Asian Cardiovasc Thorac Ann 2010;
18:13-16
© 2010 by SAGE Publications
DOI: 10.1177/0218492309355489
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