Left ventricular outflow tract mean systolic acceleration as a surrogate for the slope of the left ventricular end-systolic pressure-volume relationship.
OBJECTIVE
The goal of this study was to analyze left ventricular outflow tract systolic acceleration (LVOT(Acc)) during alterations in left ventricular (LV) contractility and LV filling.


BACKGROUND
Most indexes described to quantify LV systolic function, such as LV ejection fraction and cardiac output, are dependent on loading conditions.


METHODS
In 18 sheep (4 normal, 6 with aortic regurgitation, and 8 with old myocardial infarction), blood flow velocities through the LVOT were recorded using conventional pulsed Doppler. The LVOT(Acc) was calculated as the aortic peak velocity divided by the time to peak flow; LVOT(Acc) was compared with LV maximal elastance (E(m)) acquired by conductance catheter under different loading conditions, including volume and pressure overload during an acute coronary occlusion (n = 10). In addition, a clinically validated lumped-parameter numerical model of the cardiovascular system was used to support our findings.


RESULTS
Left ventricular E(m) and LVOT(Acc) decreased during ischemia (1.67 +/- 0.67 mm Hg.ml(-1) before vs. 0.93 +/- 0.41 mm Hg.ml(-1) during acute coronary occlusion [p < 0.05] and 7.9 +/- 3.1 m.s(-2) before vs. 4.4 +/- 1.0 m.s(-2) during coronary occlusion [p < 0.05], respectively). Left ventricular outflow tract systolic acceleration showed a strong linear correlation with LV E(m) (y = 3.84x + 1.87, r = 0.85, p < 0.001). Similar findings were obtained with the numerical modeling, which demonstrated a strong correlation between predicted and actual LV E(m) (predicted = 0.98 [actual] -0.01, r = 0.86). By analysis of variance, there was no statistically significant difference in LVOT(Acc) under different loading conditions.


CONCLUSIONS
For a variety of hemodynamic conditions, LVOT(Acc) was linearly related to the LV contractility index LV E(m) and was independent of loading conditions. These findings were consistent with numerical modeling. Thus, this Doppler index may serve as a good noninvasive index of LV contractility.
Bauer
Fabrice
F
Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Jones
Michael
M
Shiota
Takahiro
T
Firstenberg
Michael S
MS
Qin
Jian Xin
JX
Tsujino
Hiroyuki
H
Kim
Yong Jin
YJ
Sitges
Marta
M
Cardon
Lisa A
LA
Zetts
Arthur D
AD
Thomas
James D
JD
D000054:Acceleration; D000704:Analysis of Variance; D000818:Animals; D001022:Aortic Valve Insufficiency / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002302:Cardiac Output; D004195:Disease Models, Animal; D015150:Echocardiography, Doppler / Q000592:standards; D006439:Hemodynamics; D016014:Linear Models; D008955:Models, Cardiovascular; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000503:physiopathology*; D009716:Numerical Analysis, Computer-Assisted; D015588:Observer Variation; D012756:Sheep; D013318:Stroke Volume / Q000502:physiology*; D013599:Systole / Q000502:physiology*; D016277:Ventricular Function, Left / Q000502:physiology*; D017725:Ventricular Pressure / Q000502:physiology*