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Technical Briefs

A Novel Method to Measure Mitral Valve Chordal Tension

[+] Author and Article Information
Zhaoming He1

Department of Mechanical Engineering, Texas Tech University, 7th Street and Boston Avenue, P.O. Box 41021, Lubbock, TX 79409zhaoming.he@ttu.edu

Christopher Jowers

Department of Mechanical Engineering, Texas Tech University, 7th Street and Boston Avenue, P.O. Box 41021, Lubbock, TX 79409

1

Corresponding author.

J Biomech Eng 131(1), 014501 (Nov 20, 2008) (4 pages) doi:10.1115/1.3005160 History: Received September 25, 2007; Revised September 16, 2008; Published November 20, 2008

Proper leaflet coaptation of the mitral valve is vital for a healthy functioning heart. Chordal tension directly affects leaflet coaptation. The C-shaped transducer used previously to measure chordal tension was too big for tension measurement of multiple chordae and their branches. A new method is needed to measure chordal tension with minimum interference with chord and leaflet motion. The method was to extrapolate longitudinal chordal tension from transverse chordal fibril force measured by inserting a small elliptical AIFP4 sensor from MicroStrain Inc. (Williston, VT) through a chord. Sensitivity of the method has been tested with the sensor implanted in chordae, and error of the method has been estimated at various sensor deviation angles. Intact porcine and ovine hearts were used to measure mitral valve strut and marginal chordal tensions at static transmitral pressures of 120mmHg and 160mmHg under an in vitro condition. The results obtained from the AIFP4 sensor were similar to the results obtained previously by C-shaped transducers in the porcine mitral valves. The sensor output errors increased with the increase in sensor deviation angle in the chord at a peak systolic tension. Strut chordal tensions of four ovine mitral valves of Edwards ring size M 28 were 0.29±0.06N at the transmitral pressure of 120mmHg. The tension of 18 porcine strut chordae of porcine mitral valves of Edwards ring size M 32 was 1.00±0.42N at the transmitral pressures of 120mmHg. The tension of 22 anterior leaflet marginal chordae from porcine mitral valves of Edwards ring size M 32 was 0.10±0.04N at the transmitral pressure of 120mmHg. A new method using an AIFP4 miniature force sensor to measure mitral valve chordal tension indirectly is successfully developed. This force sensor works well in measuring mitral valve chordal tension at an in vitro hydrostatic transmitral pressure. The size and simple fixation of the sensor make it favorable for chordal tension measurement of multiple chordae and their branches under in vitro or in vivo conditions with minimal interference with chordal geometry and dynamics.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 4

Porcine strut and marginal chordal tensions under transmitral pressures of 120mmHg and 160mmHg

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Figure 3

Two AIFP4 sensors were implanted in anterior leaflet marginal and strut chordae originating from the posteromedial papillary muscle

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Figure 2

Measurement error in (a) strut and (b) marginal chordal tensions increased with the increase in misalignment angle of the sensor

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Figure 1

(a) The AIFP4 sensor has an elliptical cross section with a minor axis of 1.4mm and a major axis of 1.8mm and is 5mm in length and (b) schematic of sensor implantation and chordal tension measurement from transverse force

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