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Impact of Doppler guidewire size and flow rates on intravascular velocity profiles
R Jenni1, M Büchi, H J Zweifel
1Division of Echocardiography, University Hospital, Zurich, Switzerland.
Insights
A small Doppler guidewire does not significantly alter coronary artery blood flow velocity profiles. This finding is crucial for accurate assessment of coronary reserve, ensuring reliable clinical measurements.
Area of Science:
- Cardiovascular physiology
- Medical imaging technology
Background:
- Conventional intravascular Doppler devices are limited by catheter size, affecting coronary blood flow velocity measurements.
- Accurate assessment of coronary reserve is clinically vital and can be impacted by velocity profile changes during hyperemia.
Purpose of the Study:
- To evaluate the influence of a small Doppler guidewire on velocity profiles in simulated epicardial coronary arteries.
- To determine if the guidewire affects coronary reserve assessment at physiological flow rates.
Main Methods:
- An in vitro study using silicone tubes mimicking coronary artery diameters.
- A 0.014" Doppler guidewire was tested with human whole blood perfusion at various flow rates.
- Velocity profiles were analyzed during antegrade and retrograde perfusion to calculate mean velocity (Vm) and average peak velocity (APV).
Main Results:
- The Doppler guidewire showed a constant relationship between APV and Vm, indicating minimal disturbance to velocity profiles.
- The shape factor (fp = Vm/APV) remained consistent, suggesting the guidewire does not substantially alter flow dynamics.
- A slight, flow-dependent increase in experimental fp was observed, differing from theoretical expectations.
Conclusions:
- The small Doppler guidewire minimally impacts velocity profiles in coronary artery-sized vessels.
- This supports the reliability of Doppler guidewires for assessing coronary blood flow and coronary reserve.
- Further investigation into the discrepancy between experimental and theoretical shape factors at higher flows is warranted.
Abstract:
Coronary blood flow velocity measurements by conventional intravascular catheter-based Doppler devices are well known to be affected by catheter size. Moreover, it is of clinical importance that the assessment of maximum vasodilator capacity, i.e., the coronary reserve, might be considerably affected by a shape change of the velocity profile under hyperemia. Therefore, the present in vitro study aimed to assess the impact of a small-size Doppler guidewire on the velocity profiles interrogated in tubes with diameters corresponding to the epicardial coronary arteries at clinically relevant flow rates. A 0.014" guidewire was inserted into four serially connected silicone tubes of known diameter, which were perfused with discarded human whole blood by means of a roller pump. In order to determine the effect of the Doppler guidewire on the velocity profile antegrade and retrograde perfusion were carried out in each vessel segment. Vm, the true mean velocity, was calculated from the time collected flow divided by the corresponding vessel cross-sectional area. Average peak velocity (APV) measurements were obtained by pulling back the Doppler device across each of the four vessel segments with given flow rates ranging from 1.14-5.88 ml/s in antegrade and retrograde direction. The shape factor of the recorded velocity profile (fp) is defined as vm/APV and is generally assumed to be close to 0.5. Antegrade perfusion: APV = 1.63 vm + 5.35 (R2 = 0.98); fp = 0.001 vm + 0.51. Retrograde perfusion: APV = 1.71 vm + 3.33 (R2 = 0.98); fp = 0.001 vm + 0.52. Due to the constant relationship between APV and vm, velocity profiles within vessels of epicardial coronary artery size are not substantially disturbed by the presence of the Doppler guidewire. The slight, but significant increase of experimental fp with increasing flow is at variance with the theoretically expected fp values.