Medical Engineering & Physics
Volume 28, Issue 2 , Pages 122-133, March 2006

Time-dependent analysis of leaflets in mechanical aortic bileaflet heart valves in closing phase using the finite strip method

  • H. Mohammadi

      Affiliations

    • Graduate Program in Biomedical Engineering, University of Western Ontario, London, Ont., Canada N6A 5B9
    • Center of Excellence in Dynamics, Robotics, and Automation, Sharif University of Technology, Tehran, Iran
    • ,
  • M.T. Ahmadian

      Affiliations

    • Center of Excellence in Dynamics, Robotics, and Automation, Sharif University of Technology, Tehran, Iran
    • ,
  • W.K. Wan

      Affiliations

    • Graduate Program in Biomedical Engineering, University of Western Ontario, London, Ont., Canada N6A 5B9
    • Department of Chemical and Biochemical Engineering, University of Western Ontario, London, Ont., Canada N6A 5B9
    • Corresponding Author InformationCorresponding author. Tel.: +1 519 661 2111x88440; fax: +1 519 850 2308.

Received 26 September 2003; received in revised form 5 January 2005; accepted 16 March 2005. published online 09 June 2005.

Abstract 

Background and aims of the study

Mechanical heart valves (MHV) are widely used to replace dysfunctional and failed heart valves. The bileaflet MHV design is very popular due to its superior hemodynamics. Since their introduction in 1977, the hemodynamics of bileaflet prostheses has been extensively studied. In this study the dynamic behaviour during the closing phase of a bileaflet MHV under normal physiological conditions has been investigated.

Methods

Fluid analysis is based on the control volume with moving boundaries in the vicinity of the occluder. Unsteady continuity equation, unsteady momentum equation on the control volume and unsteady Bernoulli's equation have been used to calculate velocity of blood flow and force on the occluder tip. To solve the governing equations for the calculation of pressure and the related force, the finite strips method has been implemented. Only 32 strips are sufficient to calculate the force due to pressure on the leaflets. The equations of motion have been solved using the Runge–Kutta method in the fourth order.

Results

The maximum velocity of the leakage flow in the closing phase falls within the range of 3.5–4.4m/s. The maximum velocity of the occluder tip is in the range of 2.4–3.2m/s. The backflow also exhibits oscillation similar to that of the occluder with net backflow rate in the range of 9.7–12.3ml/beat. The impact force between occluder and its housing is in the range of 80–140N and impact occurs during 33.1–41.0ms and the leaflets are completely settled at 108–115ms in the closing phase.

Conclusion

The finite strip method was implemented to study the closing phase of a bileaflet MHV. Results are consistent with the previous experimental data. This method is of general applicability to study dynamic behaviour of MHVs.

Keywords: Finite strip method, Mechanical heart valve, Aortic pressure, Closing phase, Back flow, Impact force, Ventricular pressure

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PII: S1350-4533(05)00079-2

doi:10.1016/j.medengphy.2005.03.013

Medical Engineering & Physics
Volume 28, Issue 2 , Pages 122-133, March 2006

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