Quantification of mitral regurgitation by automated cardiac output measurement: experimental and clinical validation.
OBJECTIVE
To develop and validate an automated noninvasive method to quantify mitral regurgitation.


BACKGROUND
Automated cardiac output measurement (ACM), which integrates digital color Doppler velocities in space and in time, has been validated for the left ventricular (LV) outflow tract but has not been tested for the LV inflow tract or to assess mitral regurgitation (MR).


METHODS
First, to validate ACM against a gold standard (ultrasonic flow meter), 8 dogs were studied at 40 different stages of cardiac output (CO). Second, to compare ACM to the LV outflow (ACMa) and inflow (ACMm) tracts, 50 normal volunteers without MR or aortic regurgitation (44+/-5 years, 31 male) were studied. Third, to compare ACM with the standard pulsed Doppler-two-dimensional echocardiographic (PD-2D) method for quantification of MR, 51 patients (61+/-14 years, 30 male) with MR were studied.


RESULTS
In the canine studies, CO by ACM (1.32+/-0.3 liter/min, y) and flow meter (1.35+/-0.3 liter/min, x) showed good correlation (r=0.95, y=0.89x+0.11) and agreement (deltaCO(y-x)=0.03+/-0.08 [mean+/-SD] liter/min). In the normal subjects, CO measured by ACMm agreed with CO by ACMa (r=0.90, p < 0.0001, deltaCO=-0.09+/-0.42 liter/min), PD (r=0.87, p < 0.0001, deltaCO=0.12+/-0.49 liter/min) and 2D (r=0.84, p < 0.0001, deltaCO=-0.16+/-0.48 liter/min). In the patients, mitral regurgitant volume (MRV) by ACMm-ACMa agreed with PD-2D (r= 0.88, y=0.88x+6.6, p < 0.0001, deltaMRV=2.68+/-9.7 ml).


CONCLUSIONS
We determined that ACM is a feasible new method for quantifying LV outflow and inflow volume to measure MRV and that ACM automatically performs calculations that are equivalent to more time-consuming Doppler and 2D measurements. Additionally, ACM should improve MR quantification in routine clinical practice.
Sun
J P
JP
Cardiovascular Imaging Center, Department of Cardiology, The Cleveland Clinic Foundation, Ohio 44195, USA.
Yang
X S
XS
Qin
J X
JX
Greenberg
N L
NL
Zhou
J
J
Vazquez
C J
CJ
Griffin
B P
BP
Stewart
W J
WJ
Thomas
J D
JD
D000328:Adult; D000818:Animals; D001021:Aortic Valve / Q000000981:diagnostic imaging; D002302:Cardiac Output; D004285:Dogs; D018618:Echocardiography, Doppler, Color; D018619:Echocardiography, Doppler, Pulsed; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000000981:diagnostic imaging; D008944:Mitral Valve Insufficiency / Q000175:diagnosis* / Q000000981:diagnostic imaging; D015588:Observer Variation; D015203:Reproducibility of Results