TY - JOUR
T1 - Early left ventricular diastolic function quantitation using directional impedances
AU - Ghosh, Erina
AU - Kovács, Sándor J.
N1 - Funding Information:
The assistance of the staff of the Cardiovascular Procedure Center at Barnes-Jewish Hospital at Washington University Medical Center and Peggy Brown for expert echocardiographic data acquisition is gratefully acknowledged. This work was supported in part by the Alan A. and Edith L. Wolff Charitable Trust (St. Louis, MO) and the Barnes-Jewish Hospital Foundation. E. Ghosh is a recipient of a Heartland Affiliate Predoctoral Fellowship Award from the American Heart Association.
PY - 2013/6
Y1 - 2013/6
N2 - Impedance has been used in vascular biology to characterize the frequency dependent opposition the circulatory system presents to blood flow in response to a pulsatile pressure gradient. It has also been used to characterize diastolic function (DF) via the early, diastolic left ventricular (LV) pressure-flow relation. In a normal LV, early filling volume is accommodated primarily by wall-thinning and ascent of the mitral annulus relative to the spatially fixed apex (longitudinal chamber expansion). Simultaneously, the endocardial (transverse or short axis) dimension also increases while epicardial (transverse) external dimension remains essentially constant. To quantify these directional filling attributes, we compute longitudinal (Z L) and transverse (Z T) impedances during early rapid-filling (Doppler E-wave). Z L and Z T were calculated from 578 cardiac cycles of simultaneous transmitral flow and high fidelity LV pressure data in 17 subjects with normal LV function. Average Z L was 0.7 ± 0.4 mmHg s/cm4 and average Z T was 238 ± 316 mmHg s/cm2. Direct comparison, in the same units is achieved by computing Z T over the ≈10 cm2 cross-sectional area of LV (denoted ŽT) revealing that Z L is ≈34 times smaller than ŽT. This quantifies the physiologic preference for longitudinal LV volume accommodation. Lowest Z L and Z T values occurred in the first harmonic with monotonically increasing values with higher harmonics. We conclude that Z L and Z T characterize longitudinal and transverse chamber properties of DF and therefore, diastolic dysfunction can be viewed as a state of impedance mismatch.
AB - Impedance has been used in vascular biology to characterize the frequency dependent opposition the circulatory system presents to blood flow in response to a pulsatile pressure gradient. It has also been used to characterize diastolic function (DF) via the early, diastolic left ventricular (LV) pressure-flow relation. In a normal LV, early filling volume is accommodated primarily by wall-thinning and ascent of the mitral annulus relative to the spatially fixed apex (longitudinal chamber expansion). Simultaneously, the endocardial (transverse or short axis) dimension also increases while epicardial (transverse) external dimension remains essentially constant. To quantify these directional filling attributes, we compute longitudinal (Z L) and transverse (Z T) impedances during early rapid-filling (Doppler E-wave). Z L and Z T were calculated from 578 cardiac cycles of simultaneous transmitral flow and high fidelity LV pressure data in 17 subjects with normal LV function. Average Z L was 0.7 ± 0.4 mmHg s/cm4 and average Z T was 238 ± 316 mmHg s/cm2. Direct comparison, in the same units is achieved by computing Z T over the ≈10 cm2 cross-sectional area of LV (denoted ŽT) revealing that Z L is ≈34 times smaller than ŽT. This quantifies the physiologic preference for longitudinal LV volume accommodation. Lowest Z L and Z T values occurred in the first harmonic with monotonically increasing values with higher harmonics. We conclude that Z L and Z T characterize longitudinal and transverse chamber properties of DF and therefore, diastolic dysfunction can be viewed as a state of impedance mismatch.
KW - Characteristic impedance
KW - Diastolic function
KW - Echocardiography
KW - Input impedance
KW - Longitudinal impedance
KW - Transverse impedance
UR - http://www.scopus.com/inward/record.url?scp=84886730951&partnerID=8YFLogxK
U2 - 10.1007/s10439-013-0756-z
DO - 10.1007/s10439-013-0756-z
M3 - Article
C2 - 23370721
AN - SCOPUS:84886730951
SN - 0090-6964
VL - 41
SP - 1269
EP - 1278
JO - Annals of biomedical engineering
JF - Annals of biomedical engineering
IS - 6
ER -