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Research Papers

Effect of Hinge Gap Width of a St. Jude Medical Bileaflet Mechanical Heart Valve on Blood Damage Potential—An In Vitro Micro Particle Image Velocimetry Study

[+] Author and Article Information
Brian H. Jun

G. W. Woodruff School
of Mechanical Engineering,
Georgia Institute of Technology,
Atlanta, GA 30318
e-mail: bjun3@gatech.edu

Neelakantan Saikrishnan

Wallace H. Coulter School
of Biomedical Engineering,
Georgia Institute of Technology
and Emory University,
Atlanta, GA 30318
e-mail: neelakantan@gmail.com

Sivakkumar Arjunon

Wallace H. Coulter School
of Biomedical Engineering,
Georgia Institute of Technology
and Emory University,
Atlanta, GA 30339
e-mail: sivakkumar.arjunon@bme.gatech.edu

B. Min Yun

G. W. Woodruff School
of Mechanical Engineering,
Georgia Institute of Technology,
Atlanta, GA 30318
e-mail: min@gatech.edu

Ajit P. Yoganathan

Wallace H. Coulter Department
of Biomedical Engineering,
Georgia Institute of Technology
and Emory University,
Atlanta, GA 30318;
e-mail: ajit.yoganathan@bme.gatech.edu

Manuscript received January 5, 2014; final manuscript received June 19, 2014; accepted manuscript posted July 2, 2014; published online July 16, 2014. Assoc. Editor: Dalin Tang.

J Biomech Eng 136(9), 091008 (Jul 16, 2014) (11 pages) Paper No: BIO-14-1006; doi: 10.1115/1.4027935 History: Received January 05, 2014; Revised June 19, 2014; Accepted July 02, 2014

The hinge regions of the bileaflet mechanical heart valve (BMHV) can cause blood element damage due to nonphysiological shear stress levels and regions of flow stasis. Recently, a micro particle image velocimetry (μPIV) system was developed to study whole flow fields within BMHV hinge regions with enhanced spatial resolution under steady leakage flow conditions. However, global velocity maps under pulsatile conditions are still necessary to fully understand the blood damage potential of these valves. The current study hypothesized that the hinge gap width will affect flow fields in the hinge region. Accordingly, the blood damage potential of three St. Jude Medical (SJM) BMHVs with different hinge gap widths was investigated under pulsatile flow conditions, using a μPIV system. The results demonstrated that the hinge gap width had a significant influence during the leakage flow phase in terms of washout and shear stress characteristics. During the leakage flow, the largest hinge gap generated the highest Reynolds shear stress (RSS) magnitudes (∼1000 N/m2) among the three valves at the ventricular side of the hinge. At this location, all three valves indicated viscous shear stresses (VSS) greater than 30 N/m2. The smallest hinge gap exhibited the lowest level of shear stress values, but had the poorest washout flow characteristics among the three valves, demonstrating propensity for flow stasis and associated activated platelet accumulation potential. The results from this study indicate that the hinge is a critical component of the BMHV design, which needs to be optimized to find the appropriate balance between reduction in fluid shear stresses and enhanced washout during leakage flow, to ensure minimal thrombotic complications.

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References

Figures

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Fig. 1

(a) SJM Bileaflet mechanical heart valve clear housing model [9], (b) general components of BMHV [10], (c) leaflets in fully opened position [9], (d) leaflets in fully closed position [9], and (e) side view of hinge recess [9]

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Fig. 2

Schematic of pulsatile micro-PIV experimental system

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Fig. 3

Aortic flow and pressure waveforms from the three valve types

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Fig. 4

Ensemble averaged flow fields (displaying every other vector) acquired from PIV for the three valves (FLAT plane) at the peak systolic phase. Velocity field from (a) LLP, (b) Standard, and (c) HLP. RSS field from (d) LLP, (e) Standard, and (f) HLP. VSS field from (g) LLP, (h) Standard, and (i) HLP.

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Fig. 5

Ensemble averaged velocity fields (displaying every other vector) acquired from PIV for the Standard valve at the mid-diastolic phase. Measurement plane at (a) flat level, (b) 195 μm above flat level, (c) 390 μm above flat level, and (d) 585 μm above flat level.

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Fig. 6

Ensemble averaged flow fields (displaying every other vector) acquired from PIV for the three valves (FLAT plane) at the mid-diastolic phase. Velocity field from (a) LLP, (b) Standard, and (c) HLP. RSS field from (d) LLP, (e) Standard, and (f) HLP. VSS field from (g) LLP, (h) Standard, and (i) HLP.

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Fig. 7

Ensemble averaged flow fields (displaying every other vector) acquired from PIV for the three valves (390 μm plane) at the mid-diastolic phase. Velocity field from (a) LLP, (b) Standard, and (c) HLP.

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Fig. 8

Comparison of the simulated (CFD) [18] and experimentally (PIV) measured hinge flow structures [9]. Measurement plane at (a) flat level at the peak systolic phase, (b) flat level at the peak systolic phase (CFD), (c) flat level at the mid-diastolic phase (PIV), and (d) flat level at the mid-diastolic phase (CFD).

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