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Technical Briefs

In Vitro Comparison of Doppler and Catheter-Measured Pressure Gradients in 3D Models of Mitral Valve Calcification

[+] Author and Article Information
Andrew W. Siefert

The Wallace H. Coulter Department of Biomedical Engineering,
Georgia Institute of Technology and Emory University,
Atlanta, GA 30332

Gregg S. Pressman

Einstein Medical Center,
Department of Internal Medicine,
Division of Cardiology,
Philadelphia, PA 19141

Ajit P. Yoganathan

e-mail: ajit.yoganathan@bme.gatech.edu
The Wallace H. Coulter Department of Biomedical Engineering,
Georgia Institute of Technology and Emory University,
Atlanta, GA 30332

1Corresponding author.

Contributed by the Bioengineering Division of ASME for publication in the JOURNAL OF BIOMECHANICAL ENGINEERING. Manuscript received December 29, 2012; final manuscript received May 6, 2013; accepted manuscript posted May 16, 2013; published online July 10, 2013. Assoc. Editor: Kevin D. Costa.

J Biomech Eng 135(9), 094502 (Jul 10, 2013) (5 pages) Paper No: BIO-12-1638; doi: 10.1115/1.4024579 History: Received December 29, 2012; Revised May 06, 2013; Accepted May 16, 2013

Mitral annular calcification (MAC) involves calcium deposition in the fibrous annulus supporting the mitral valve (MV). When calcification extends onto the leaflets, valve opening can be restricted. The influence of MAC MV geometry on Doppler gradients is unknown. This study describes a novel methodology to rapid-prototype subject-specific MAC MVs. Replicated valves were used to assess the effects of distorted annular-leaflet geometry on Doppler-derived, transmitral gradients in comparison to direct pressure measurements and to determine if transmitral gradients vary according to measurement location. Three-dimensional echocardiography data sets were selected for two MAC MVs and one healthy MV. These MVs were segmented and rapid prototyped in their middiastolic configuration for in vitro testing. The effects of MV geometry, measurement modality, and measurement location on transmitral pressure gradient were assessed by Doppler and catheter at three locations along the MV's intercommissural axis. When comparing dimensions of the rapid-prototyped valves to the subject echocardiography data sets, mean relative errors ranged from 6.2% to 35%. For the evaluated MVs, Doppler pressure gradients exhibited good agreement with catheter-measured gradients at a variety of flow rates, though with slight systematic overestimation in the recreated MAC valves. For all of the tested MVs, measuring the transmitral pressure gradient at differing valve orifice positions had minimal impact on observed gradients. Upon the testing of additional normal and calcific MVs, these data may contribute to an improved clinical understanding of MAC-related mitral stenosis. Moreover, they provide the ability to statistically evaluate between measurement locations, flow rates, and valve geometries for Doppler-derived pressure gradients. Determining these end points will contribute to greater clinical understanding for the diagnosis MAC patients and understanding the use and application of Doppler echocardiography to estimate transmitral pressure gradients.

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References

Figures

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Fig. 1

Mitral valve segmentation methodology

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Fig. 2

Qualitative comparison of the patient 3D echocardiography mitral valves and the resultant segmented models; image pairs are shown from an en face atrial view

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Fig. 3

Left experimental steady flow loop setup with the left atrium (LA), left ventricle (LV), and rapid-prototyped mitral valve (MV); right: en face view of the rapid-prototyped MV with the centerline, 1-cm anterior, and 1-cm posterior transmitral pressure measurement locations identified

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Fig. 4

Comparison of direct measurements and those derived from Doppler echocardiography (for flow rates of 10–30 l/min in 5 l/min intervals) based on data collected at the anterior commissure, centerline, and posterior commissure of each valve

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