Assignment Answers Flashcards
List 6 technical factors and other causes of turbulent flow related to spectral broadening besides stenosis
- A large Doppler sample volume (gate) that includes all or most of the artery lumen
- High gain settings
- Increased vessel wall motion
- High velocities contralateral to a severely diseased or occluded ICA
- Tortuous vessels
- Post CEA
Changes in the appearance of the carotid artery Doppler waveform can indicate alterations in cardiac function. List 4 examples of when this occurs
- active intra-aortic balloon pumps
- left ventricular assist devices
- patients with a low cardiac output
- aortic valvular disease
What two techniques can be used in cases where calcified plaque obscures the lumen of the vessel?
Changing the angle of insonation and using power Doppler.
Soft plaque that is anechoic will be difficult to detect unless color Doppler_ is applied and the vessel lumen is evaluated in relation to the wall of the vessel. What will happen if the color gain is set too high?
It will obscure the plaque with color
Bleeding?
List two reasons the ECA receives less attention than the ICA.
It is not associated with stroke and stenoses are less common in the ECA
TCD and its usage
Noninvasive method for assessing cerebral hemodynamics and evaluating intracranial cerebrovascular disease
Define TCCS and its usage
Transcranial color-coded duplex sonography; allows for angle corrected measurements of velocities at defined depths
What are the 2 prerequisites that should be fulfilled before performing a TCD examination?
Status of extracranial arteries has to be known
Patient must lie still to avoid carbon dioxide fluctuations and motion artifacts
Why do transcranial instruments have a lower bandwidth?
They require a large signal to noise ratio
For TCDs,
Describe the sample volume
Describe the Doppler device
Larger and less defined sample volume compared to other pulsed Doppler devices
2 MHz, pulsed, range gate Doppler device with good directional resolution
TCD - which vessel using the Transtemporal approach has the highest velocities and what is the range
MCA
55 +/- 12 cm/s
Which vessel using the suboccipital approach is at the deepest reference depth and what is the velocity range?
Basilar trunk;
41+ 10 cm/s
3 features of a stenosis seen with TCD
Increased flow velocity; disturbed flow (spectral broadening); covibration phenomenon (vibration of vessel wall and surrounding tissue)
TCDs: What 3 observations are made when there is an occlusion suspected
Absence of arterial signals;
signal in communicating vessels of the occluded artery;
altered flow in communicating vessels signifying collateralization
With carotid stenosis > 80% or occlusion (extracranial), what changes are seen in the ipsilateral MCA?
Velocity and pulsatility index decreases as a result of vasodilation
In the vertebrobasilar system, briefly describe what occurs in the case of severe obstruction of the proximal subclavian artery?
Blood to the affected arm will flow retrograde through the ipsilateral VA and may be stolen from the contralateral VA and basilar-SSS
What flow pattern is seen in the basilar artery if the contralateral VA is diseased or hypoplastic:
Becomes reduced with a to and fro flow pattern
What does the current dialysis outcome quality initiative (DOQI) guidelines encourage and why?
Placement of AVF’s rather than grafts
They have greater longevity and decreased incidence of infection
What proportion of AVF’s fail despite preoperative mapping?
60%
Briefly describe a native AVF:
What is the option if an AVF creation is not possible?
Surgically created direct anastomosis between and artery and a vein in either the forearm or upper arm
Artificial graft of polytetraflourine
List the minimum diameter criteria for AVF and graft creation:
minimum cephalic and basilica vein and brachial artery diameter:
AVF vein 2.5mm
Graft vein 4.0mm
Artery (for graft of AVF) 2.0mm
CV 2.5mm
BA 2mm
Bas V 4mm
List 3 things that must be ruled out when assessing the subclavian and IJ veins:
Stenosis, occlusions, thrombus
3 complications grafts
Stenosis, infection and pseudoaneurysm
