ABSTRACT
The sample volume of pulsed Doppler must be carefully placed in the LV outflow close to the aortic valve, but before flow acceleration occurs. The disadvantage of this measure is that the velocity may vary if placement is not carefully attended to. This measurement is reproducible in most laboratories, but others prefer the use of continuous-wave Doppler to assess stroke volume. A disadvantage of continuous wave Doppler is that the maximum velocity along the entire beam is represented. Continuous-wave Doppler may not accurately represent volumetric
stroke volume in situations where the crosssectional area through the aortic valve is not represented by the cross-sectional area of the measured aortic annulus in low-flow states where the valve leaflets do not separate fully. Accordingly, the pulsed Doppler method may be advantageous in the assessment of heart failure patients with diminished stroke volume. The relative advantages and disadvantages of pulsed versus continuous-wave Doppler become less important when patients are assessed before and acutely after CRT, where one assesses changes from baseline and individual patients serve as their own controls. Another important factor is the presence of heart rate changes that may affect results. Acute increases in Doppler measures of stroke volume following CRT have been predicted by the presence of longitudinal dyssynchrony by tissue Doppler velocities and also radial dyssynchrony by either tissue Doppler or speckle tracking measures of radial strain.5-7 In a group of 29 patients studied by longitudinal color-coded tissue Doppler – known as tissue synchronization imaging – CRT was associated with acute favorable effects on LV function for the entire study group: stroke volume by pulsed Doppler increased from 56 ± 12 ml to 63 ± 12 ml (p < 0.001).5
