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Eur J Cardiothorac Surg 2001;19:736
© 2001 Elsevier Science NL

Letter to the Editor

Reply to Péterffy and Szentkirályi

Department of Surgery, Kurume University School of Medicine, Kurume, Japan

Received 4 March 2000; accepted 6 March 2001.

Corresponding author. National Kyushu Medical Center Hospital, 1-8-1 Jigyouhama, Chuoku, Fukuoka, 810-8563 Japan. Tel.: +81-92-852-0700; fax: +81-92-846-8485
e-mail: hkawano{at}qmed.hosp.go.jp

We read with great interest the report of Drs Péterffy and Szentkirályi [1] entitled ‘Mechanical valves in tricuspid position: cause of thrombosis and prevention’ and wish to thank them for their suggestion. Our concern is the higher thrombogenicity of mechanical prostheses in the tricuspid position. This can occur despite adequate therapy with oral anticoagulants. Regarding the mechanism of mechanical prostheses thrombosis in the tricuspid position, the morphology of the right ventricle or the structure of mechanical prostheses have been reported to be detrimental to ideal functioning of mechanical prostheses [2]. However, these factors would not be the causes of the higher thrombogenicity of the St. Jude Medical (SJM) prosthesis in the tricuspid position because of its low-profile and bileaflet design with central laminar flow pattern. The reason we have thought that the lower pressure in the right side of the heart may be the cause of the higher thrombogenicity in the tricuspid position is the difference in Doppler echocardiographic inflow wave pattern between both sides of the heart. Compared with an inflow wave pattern in the mitral position, that in the tricuspid position shows the following differences. First, peak velocity of rapid filling flow is lower. Second, pressure half time or deceleration time is prolonged. Third, velocity is liable to variation under the influence of respiration. That is to say, although cardiac output is the same in both sides of the heart, the blood flow going across the prosthesis in the tricuspid position during diastole starts to move slowly and its velocity is not always constant. We believe this has an influence on the higher thrombogenicity in the tricuspid position. Meanwhile, the biochemical explanation for the difference of thrombogenicity of mechanical prostheses in both sides of the heart is of great interest [3]. As Drs Péterffy and Szentkirályi pointed out, prostacyclin may play an important role in preventing mechanical prostheses thrombosis, especially in the mitral position, and platelet-aggregation therapy may decrease the thrombogenicity in the tricuspid position. In our institute, aspirin is usually initiated with a dose of 81 mg in combination with warfarin, however, the platelet-aggregation therapy is discontinued in most patients after leaving the hospital. Therefore, we have no convincing data to clarify the efficiency of platelet-aggregation therapy. In the literature [4], aspirin in combination with oral anticoagulants has been reported to diminish the frequency of thromboemboli and bleeding, however, data are still insufficient to recommend dipyridamole that increases prostacyclin production in the lungs.

The ideal prosthesis is one that is durable with excellent hemodynamic performance. In our series, the excellent hemodynamic performance of the SJM prosthesis without valve-related events is well maintained over 18 years after surgery. If the addition of antiplatelet agents to oral anticoagulation really reduces the possibility of the thrombogenicity of mechanical prostheses in the tricuspid position, we fully agree with Péterffy and Szentkirályi that mechanical prostheses are the choice of valve substitute in special cases in young patients.

References

1. Péterffy A., Szentkirályi I. Mechanical valves in tricuspid position: cause of thrombosis and prevention. Eur J Cardio-thorac Surg 2001;19:735.[Free Full Text]
2. Nakano K., Koyanagi H., Hashimoto A., Ohtsuka G., Nojiri C. Tricuspid valve replacement with the bileaflet St. Jude Medical valve prosthesis. J Thorac Cardiovasc Surg 1994;108(5):888-892.
3. Péterffy A. Surgical management of tricuspid valvular disease. Scand J Thorac Cardivasc Surg 1980;Suppl.26:3-65.
4. Stein P.D., Alpert J.S., Dalen J.E., Horstkotte D., Turpie A.G. Antithrombotic therapy in patients with mechanical and biological prosthetic heart valves. Chest 1998;114(5 Suppl):602s-610s.

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