Normal asynchrony of left ventricular long and short axes: their relationship with aortic hemodynamics.
BACKGROUND
The relationship between left ventricular (LV) long and short axes, aortic pressure (P), flow velocity (U) and wave intensity is not well established.


METHODS
Eleven dogs were anaesthetized and mechanically ventilated and LV long and minor axes shortening velocities were calculated using ultrasound crystals. P and U were measured in the ascending aorta using a high fidelity pressure catheter and ultrasonic flow transducer.


RESULTS
Pre-ejection: The LV minor axis began to shorten as the long axis lengthened creating LV shape change. Early ejection: The aortic valve opened 83+/-20 ms after the ECG Q-wave. Aortic P and U simultaneously increased; peak aortic velocity and maximum minor axis shortening velocity (M(max)) occurred at 152+24 and 147+24 ms, respectively; p=0.66, intra-class correlation ICC 0.93). M(max) also corresponded to the time when the reflected compression wave arrived back to the heart (ICC 0.75). Late ejection: LV long axis reached its peak shortening velocity 28+21 ms later than the minor axis at 175+/-33 ms, coinciding with peak LV pressure (187+25 ms; p=0.77, ICC 0.65) and onset of the forward expansion wave (177+28 ms, p=0.88, ICC 0.89). Both axes then continued to slow until 210+/-30 ms when an increased rate of decline of shortening velocity corresponded with peak aortic pressure.


CONCLUSIONS
Long axis peak shortening velocity lagged consistently behind the minor axis, representing a degree of normal asynchrony. The arrival of the reflected wave appears to bring about the slowing down of the minor axis.
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Chloe M L
CM
Brunel Institute for Bioengineering & School of Engineering and Design, Brunel University, Uxbridge, Middlesex UB8 3PH, UK.
Khir
Ashraf W
AW
Hughes
Alun D
AD
Chung
Robin
R
Henein
Michael Y
MY
D000818:Animals; D001011:Aorta / Q000502:physiology* / Q000503:physiopathology; D001021:Aortic Valve / Q000502:physiology* / Q000503:physiopathology; D001783:Blood Flow Velocity / Q000502:physiology; D004285:Dogs; D006439:Hemodynamics / Q000502:physiology*; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000503:physiopathology; D016277:Ventricular Function, Left / Q000502:physiology*