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Research Papers

Surface Strains of Porcine Tricuspid Valve Septal Leaflets Measured in Ex Vivo Beating Hearts

[+] Author and Article Information
Keyvan Amini Khoiy

Department of Biomedical Engineering,
The University of Akron,
Akron, OH 44325
e-mail: ka67@zips.uakron.edu

Dipankar Biswas

Department of Mechanical Engineering,
The University of Akron,
Akron, OH 44325
e-mail: db76@zips.uakron.edu

Thomas N. Decker

Department of Biomedical Engineering,
The University of Akron,
Akron, OH 44325
e-mail: tnd14@zips.uakron.edu

Kourosh T. Asgarian

Cardiothoracic Surgery,
St. Joseph's Regional Medical Center,
Paterson, NJ 07503
e-mail: ktacardiac@aol.com

Francis Loth

Department of Mechanical Engineering,
The University of Akron,
Akron, OH 44325
e-mail: loth@uakron.edu

Rouzbeh Amini

Mem. ASME
Department of Biomedical Engineering,
The University of Akron,
260 S Forge Street,
Olson Research Center Room 301F,
Akron, OH 44325
e-mail: ramini@uakron.edu

1Corresponding author.

Manuscript received May 22, 2016; final manuscript received August 23, 2016; published online October 21, 2016. Assoc. Editor: Jessica E. Wagenseil.

J Biomech Eng 138(11), 111006 (Oct 21, 2016) (9 pages) Paper No: BIO-16-1216; doi: 10.1115/1.4034621 History: Received May 22, 2016; Revised August 23, 2016

Quantification of the tricuspid valve (TV) leaflets mechanical strain is important in order to understand valve pathophysiology and to develop effective treatment strategies. Many of the traditional methods used to dynamically open and close the cardiac valves in vitro via flow simulators require valve dissection. Recent studies, however, have shown that restriction of the atrioventricular valve annuli could significantly change their in vivo deformation. For the first time, the porcine valve leaflets deformation was measured in a passive ex vivo beating heart without isolating and remounting the valve annuli. In particular, the right ventricular apexes of porcine hearts (n = 8) were connected to a pulse-duplicator pump that maintained a pulsatile flow from and to a reservoir connected to the right atrium and the pulmonary arteries. This pump provided a right ventricular pressure (RVP) waveform that closely matched physiological values, leading to opening and closure of the tricuspid and pulmonary valves (PVs). At the midsection of the valve leaflets, the peak areal strain was 9.8 ± 2.0% (mean±standard error). The peak strain was 5.6 ± 1.1% and 4.3 ± 1.0% in the circumferential and radial directions, respectively. Although the right ventricle was beating passively, the leaflet peak areal strains closely matched the values measured in other atrioventricular valves (i.e., the mitral valve (MV)) in vivo. This technique can be used to measure leaflet strains with and without the presence of valve lesions to help develop/evaluate treatment strategies to restore normal valve deformation.

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References

Figures

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Fig. 1

(a) The schematic circulation loop and (b) the ex vivo apparatus

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Fig. 2

The T-shaped pipefitting connected to the right atrium through a straight barbed hose fitting (1). The Luer Lok assembly was connected to the other side of the T-shaped pipe fitting to support the pressure sensor. The other straight barbed hose fitting (2) connected the right ventricle to the pump. Crystal wires came out through the inferior vena cava. The umbilical clamp was used to prevent leakage from the inferior vena cava.

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Fig. 3

Umbilical clamps, cable ties, and worm-drive clamps were used for sealing

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Fig. 4

Crystals are numbered on the leaflet. The straight lines connecting the numbered crystals show the triangular elements used for strain calculation. The radial direction was defined by a vector connecting crystal 4 to crystal 7.

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Fig. 5

Right heart pressure during the cardiac cycle averaged over all of the hearts. The bars are standard errors (n = 8). The vertical lines show the opening and closure of the pulmonary valve (PV) and tricuspid valve (TV): TV closed at 0.2 s and opened at 0.54 s; the pulmonary valve opened at 0.29 s and closed at 0.44 s.

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Fig. 6

Average peak areal, maximum principal (Max Princ), circumferential (Circ), and radial strains at the leaflet midpoint measured with respect to reference 1 (Ref1, minimum RAP) and reference 2 (Ref2, end diastole). The error bars are standard error (n = 8).

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Fig. 7

The temporal strain variations during the cardiac cycle. (a) The areal, (b) maximum principal, (c) circumferential, and (d) radial strains at the leaflet midpoint averaged over all of the hearts. The shaded area shows the standard error (n = 8). Vertical lines show the time points for TV closing, PV opening, maximum RVP, PV closing, and TV opening, respectively, from left to right.

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Fig. 8

The areal, maximum principal, circumferential, and radial strains at maximum RVP. The strains are averaged over all the hearts (n = 8) and are presented on a typical septal leaflet. Minimum RAP is used as the reference for strain calculation. The arrows are showing the direction of the strains at the center of each triangular surface.

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Fig. 9

Distribution of the maximum principal strain over the leaflet during the septal entire cardiac cycle. Maximum principal strain is averaged over all of the hearts (n = 8) and showed over a typical septal leaflet during the cardiac cycle.

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