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Eur J Cardiothorac Surg 2006;29:1008-1013
© 2006 Elsevier Science NL

Turbulent stress measurements downstream of three bileaflet heart valve designs in pigs

^a Department of Cardiothoracic and Vascular Surgery, Aarhus University Hospital, Skejby Sygehus, Brendstrupgaardsvej, 8200 Aarhus, Denmark
^b Institute of Clinical Medicine, Aarhus University Hospital, Skejby Sygehus, Brendstrupgaardsvej, 8200 Aarhus, Denmark
^c The Engineering College of Aarhus, Dalgas Avenue, 8000 Aarhus, Denmark

Received 7 December 2005; received in revised form 21 February 2006; accepted 3 March 2006.

^_* Corresponding author. Address: Department of Cardiothoracic and Vascular Surgery, Aarhus University Hospital, Skejby Sygehus, Brendstrupgaardsvej, 8200 Aarhus N, Denmark. Tel.: +45 89495481; fax: +45 89496016. (Email: hasenkam{at}ki.au.dk).

Objective: Mechanical heart valves can cause thromboembolic complications, possibly due to abnormal flow patterns that produce turbulence downstream of the valve. The objective of this study was to investigate whether three different bileaflet valve designs would exhibit clinically relevant differences in downstream turbulent stresses. Methods: Three bileaflet mechanical heart valves (Medtronic Advantage^®, CarboMedics© Orbis^TM Universal and St. Jude Medical^® Standard) were implanted into 19 female 90 kg pigs. Blood velocity was measured during open chest conditions in the cross sectional area downstream of the valves with 10 MHz ultrasonic probes connected to a modified Alfred^® Pulsed Doppler equipment. As a measure of turbulence, Reynolds normal stress (RNS) was calculated at three different cardiac output ranges (3–4, 4.5–5.5, 6–7 L/min). Results: Data from 12 animals were obtained. RNS correlated with increasing cardiac outputs. The highest instantaneous RNS observed in these experiments was 47 N/m², and the mean RNS taken spatially over the cross sectional area of the aorta during systole was between 3 N/m² and 15 N/m². In none of the cardiac output ranges RNS values exceeded the lower critical limit for erythrocyte or thrombocyte damage for any of the valve designs. Conclusions: Reynolds normal stress values were below 100 N/m² for all three valve designs and the difference in design was not reflected in generation of turbulence. Hence, it is unlikely that any of the valve designs causes flow induced damage to platelets or erythrocytes.

Key Words: Animal model • Aortic valve • Hemodynamics • Ultrasound • Mechanical heart valve