Symptomatic calcific stenosis of a Toronto stentless porcine valve

European Journal of Cardio-thoracic Surgery 17 (2000) 763±765

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Case report

Symptomatic calci®c stenosis of a Toronto stentless porcine valve Patrick D.T. Tansley*, Mary N. Sheppard, John Pepper Royal Brompton Hospital, London, UK Received 13 December 1999; received in revised form 14 March 2000; accepted 21 March 2000

Abstract We describe the calci®c structural failure of a Toronto stentless porcine valve (TSPV) which had been used to replace a calci®ed bicuspid aortic valve in a 46-year-old man. Against expectations, left ventricular hypertrophy persisted and the transvalvular pressure gradient rose to 125 mmHg by 6 years with the patient becoming symptomatic and requiring redo surgery. On removal the TSPV showed atypical calci®cation of the lea¯et hinges and wall. To our knowledge this is the ®rst case reported and it may have implications for long term durability and future surgery using this prosthesis. q 2000 Elsevier Science B.V. All rights reserved. Keywords: Stentless valve; Calci®cation

1. Case report A 46-year-old man presented with syncope, dyspnoea and chest pain. He had a systolic murmur and echocardiography identi®ed left ventricular hypertrophy with a calci®ed bicuspid aortic valve and peak transvalvular pressure gradient of 10 mmHg. Although lost to follow up, he presented with similar complaints ®ve years later in 1993. He smoked 40 cigarettes per day, had a strong family history of ischaemic heart disease and no known history of hypercalcaemia. On examination, he exhibited signs of aortic stenosis. Cardiac catheterization revealed good left ventricular function with no coronary arterial lesions, a calci®ed aortic valve with reduced lea¯et excursion and a peak transvalvular pressure gradient of 120 mmHg. Echocardiography con®rmed aortic stenosis with left ventricular hypertrophy. As the patient wished to avoid anticoagulation, a 27 mm Toronto stentless porcine valve (TSPV) was implanted freehand in April 1993. Interrupted sutures were used for the proximal suture line, a continuous suture distally and mattress sutures to support each of the three commissures. The out¯ow of this stentless valve is scalloped in all three sinuses. Post-operative echocardiography showed no aortic regurgitation and his recovery was uneventful. At 3 month follow-up he was well and reported an exercise tolerance of 2 miles. By April 1994 however, echocardiogram revealed persistent left ventricular hypertrophy and * Corresponding author. Kirby Lodge, 1 Gullet Lane, Kirby Muxloe, Leicestershire LE9 2BL, UK. Tel.: 144-171-352-8121; fax: 144-171351-8530.

a peak transvalvular pressure gradient of 18 mmHg. By June 1997, despite pharmacological management, echocardiography showed the transvalvular pressure gradient had risen to 36 mmHg. By July 1999, he reported worsening symptoms and echocardiography showed severe calci®c TSPV stenosis with very limited valve movement. Left ventricular function was good, but signi®cant left ventricular hypertrophy remained and peak transvalvular pressure gradient had risen to 125 mmHg. He was admitted for redo aortic valve surgery. Pre-operative cardiac catheterization revealed mild aortic regurgitation and single vessel disease affecting the left anterior descending artery. Echocardiography (August 1999) showed left ventricular hypertrophic progression, a reduction in stroke volume and a peak transvalvular pressure gradient of 85 mmHg. During weekend leave prior to surgery he suffered a myocardial infarct and was transferred back to hospital in left ventricular failure with a raised CK at 309 (25±171) and troponin I at 1.5 (0±0.1). Pre-operative echocardiography (September 1999) revealed further deterioration in left ventricular function along with mild functional mitral regurgitation. At operation, we found the TSPV to be well seated with no paravalvular dehiscence and calci®cation con®ned to the lea¯ets. The sino-tubular junction was preserved with no outward displacement of the TSPV posts. Due to the Dacron sleeve around the Toronto valve, a dissection plane was easily found and followed. The patient's preference was for a biological stentless valve, although a stented valve could easily have been used. Thus, redo aortic valve replacement was performed with a 23 mm free-standing cryopre-

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P.D.T. Tansley et al. / European Journal of Cardio-thoracic Surgery 17 (2000) 763±765

Table 1 Tabulated echocardiographic data Echocardiogram

Peak AV pressure gradient (mmHg)

Left ventricular end systolic diameter (LVESD)

Left ventricular end systolic diameter (LVEDD)

Fractional shortening (FS %)

Pre-operative March 1993 April 1994 June 1997 July 1999 August 1999 Pre-operative September 1999 Post-operative September 1999 Out-patient follow-up November 1999

90±95 18 36 125 85 85 0 8

3.0 3.0 2.5 2.9 4 4.7 2.8 3.1

5.6 5.0 3.5 4.9 5 5.5 4.9 5.1

46 40 29 40 20 15 43 39

served aortic root homograft. A pedicled left internal thoracic artery graft was simultaneously placed on the left anterior descending artery. Post operative trans-oesophageal echocardiography demonstrated normal prosthetic and good left ventricular function. Trans-thoracic echocardiography at fourteen days revealed similar ®ndings with no transvalvular pressure gradient and a striking improvement in left ventricular function. At 6 weeks he remained clinically well and echocardiography suggested normal homograft function (Table 1).

2. Pathology The excised TSPV was found to be very heavily calci®ed in a nodular manner throughout the wall and at the hinge points of attachments of the valve lea¯ets (see Fig. 1). There was no evidence of infection or paravalvular dehiscence, lea¯et calci®cation, tears or perforations. 3. Discussion Stentless bioprosthetic valves offer the advantages inher-

Fig. 1. Macoscopic appearance of excised TSPV.

P.D.T. Tansley et al. / European Journal of Cardio-thoracic Surgery 17 (2000) 763±765

ent to homografts/autografts but have the added bene®ts of greater availability and size range. Although technically more dif®cult to implant and requiring longer ischaemic and cardiopulmonary bypass times, their principal advantage comprises superior haemodynamic function when compared to mechanical valves and stented prostheses. This is thought to be due to elimination of the rigid stent and insertion therefore of a bioprosthesis relatively larger in diameter. In addition, the aorta functions as a physiological `stent' thus allowing greater ¯exibility in response to the dynamic changes of the cardiac cycle and leading to reduced mechanical lea¯et stress. Resulting transvalvular blood ¯ow is laminar and smoother in nature, contrasting with the turbulence found across the more rigid stented prostheses [1]. However, despite the haemodynamic advantages of stentless porcine valves, the glutaraldehyde-preserved porcine tissue remains subject to intense calci®cation. Interestingly, stentless bioprostheses in animal studies have been shown as less likely to calcify than stented bioprostheses [2]. Glutaraldehyde ®xation denatures tissue by molecular cross-linkage, aiming to preserve tissue and minimize immunological reaction in vivo. Nevertheless, this process has been implicated in tissue calci®cation itself and therefore must be viewed with caution. Anti-mineralization treatments continue to be developed and aim to protect both the valve lea¯ets and the aortic wall, a task complicated by their differing histological tissue types. In addition to standard glutaraldehyde ®xation, methods to avoid calci®cation at the cellular level, surfactant usage and tissue engineering of the prosthetic valve matrix are being researched as additional approaches to these dif®cult problems [1]. The durability of stented bioprosthetic valves is known to be limited by structural degeneration as a result of mechan-

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ical stress, tissue calci®cation, lea¯et tears and rupture[3,4]. In contrast, the durability of stentless bioprostheses remains unknown, but it had been reasoned that they would generate less mechanical stresses with expected improved durability [2]. Stentless bioprostheses have only been commonly implanted since the early part of the last decade [5] and are therefore just beginning to approach the length of follow up at which long term durability may be realistically considered. Results of the TSPV pre-approval trial showed no cases of primary tissue failure at six years [5]. Twentynine stentless porcine bioprosthetic implants, similar to TSPV's have shown similar durability to stented bioprostheses during an 11 year period [5]. We believe this report to be the ®rst to demonstrate TSPV failure at 6 years due to calci®cation of the lea¯et hinges and bioprosthetic wall rather than the more typical pattern of lea¯et calci®cation seen in stented bioprosthetic valves. This type of structural calci®c failure needs to be closely observed in future as a potential cause for long term TSPV failure. References [1] Huysmans HA, David TE, Westaby S. Stentless bioprostheses, 2nd ed. Plymouth, UK: Isis Medical Media, 1999. [2] David TE, Feindel CM, Bos J, Sun Z, Scully HE, Rakowski H. Aortic valve replacement with a stentless porcine aortic valve-a six year experience. J Thorac Cardiovasc Surg 1994;108:1030±1036. [3] O'Brien MF, Gardner MAH, Garlick RB, Davison MB, Thomson HL, Burstow DJ. The Cryolife-O'Brien stentless aortic porcine xenograft valve. J Card Surg 1998;13:376±385. [4] David TE. Aortic valve replacement with stentless porcine bioprostheses. J Card Surg 1998;13:344±351. [5] David TE. The Toronto SPV bioprosthesis: clinical and haemodynamic results at 6 years. Ann Thorac Surg 1999;68:S9±S13.