Genetically altered mice provide a mechanism to define the in vivo phenotype of individual genes. This is especially relevant to genes implicated in producing myocardial diseases leading to congestive heart failure. The classic method to assess the hemodynamic phenotype in larger animals is through left ventricular (LV) pressure-volume (PV) analysis. However, determining absolute and instantaneous volume in the murine LV has been plagued by its small size and rapid heart rate. Conductance measurements offer an attractive solution to this problem by generating an instantaneous LV volume signal compatible with any myocardial size or heart rate. Unfortunately, the first generation conductance instrument generates an instantaneous conductance (volume) signal composed of blood and myocardium even at a single lower frequency. Only the blood component is desired for PV analysis. A mechanism to overcome this limitation is proposed by measuring admittance (complex conductance). Admittance is composed of both the magnitude of LV blood and myocardial conductance, and the phase angle of myocardial conductance. Traditional single frequency conductance measures only the magnitude of the conductance signal, which includes both the blood and myocardial components. Because measurable phase angle is unique to muscle, admittance offers a better method to determine and remove the instantaneous myocardial contribution to the combined LV conductance (volume) signal. The GOAL of this grant application is to develop, calibrate, and validate an INSTRUMENT to measure both the magnitude and the phase angle of the admittance signal in real time. To accomplish this goal, we will - 1) Develop both analog hardware and digital data acquisition Admittance Instruments, 2) Develop a more accurate method to derive LV volume from admittance measurements using FEM, and 3) Demonstrate that an Admittance Instrument is superior to traditional single frequency with MRI. ? ?

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21HL079926-01A1
Application #
7038599
Study Section
Bioengineering, Technology and Surgical Sciences Study Section (BTSS)
Program Officer
Baldwin, Tim
Project Start
2006-09-01
Project End
2008-05-31
Budget Start
2006-09-01
Budget End
2007-05-31
Support Year
1
Fiscal Year
2006
Total Cost
$189,211
Indirect Cost
Name
University of Texas Health Science Center San Antonio
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
800772162
City
San Antonio
State
TX
Country
United States
Zip Code
78229
Elahi, Sahar; Milner, Thomas E; Rapoza, Richard J et al. (2014) Flare spots in intravascular optical coherence tomography images of bioabsorbable stents. JACC Cardiovasc Imaging 7:1174-5
Raghavan, Karthik; Feldman, Marc D; Porterfield, John E et al. (2011) A bio-telemetric device for measurement of left ventricular pressure-volume loops using the admittance technique in conscious, ambulatory rats. Physiol Meas 32:701-15
Porterfield, John E; Larson, Erik R; Jenkins, James T et al. (2011) Left ventricular epicardial admittance measurement for detection of acute LV dilation. J Appl Physiol (1985) 110:799-806
Trevino, Rodolfo J; Jones, Douglas L; Escobedo, Daniel et al. (2010) Validation of a new micro-manometer pressure sensor for cardiovascular measurements in mice. Biomed Instrum Technol 44:75-83
Pearce, John A; Porterfield, John E; Larson, Erik R et al. (2010) Accuracy considerations in catheter based estimation of left ventricular volume. Conf Proc IEEE Eng Med Biol Soc 2010:3556-8
Raghavan, Karthik; Porterfield, John E; Kottam, Anil T G et al. (2009) Electrical conductivity and permittivity of murine myocardium. IEEE Trans Biomed Eng 56:2044-53
Porterfield, John E; Kottam, Anil T G; Raghavan, Karthik et al. (2009) Dynamic correction for parallel conductance, GP, and gain factor, alpha, in invasive murine left ventricular volume measurements. J Appl Physiol 107:1693-703