CAQ-CVTS common mistakes
CAQ-CVTS · Understand the traps and how to avoid them.
Reporting a carotid stenosis category from peak systolic velocity (PSV) alone while ignoring the end-diastolic velocity, the ICA/CCA ratio, the spectral waveform shape, and the presence of a tandem or contralateral lesion.
Most published criteria are memorized as single PSV cutoffs, and candidates treat the velocity table as the answer rather than as one input into an integrated interpretation.
What to do instead
Build a habit of recording four numbers for every carotid: ICA PSV, ICA end-diastolic velocity, ICA/CCA ratio, and the contralateral ICA PSV, then state whether the waveform is low-resistance or high-resistance. Practice writing full impression lines that cite all four values and explain any discordance (for example, a high PSV with low EDV suggesting a distal obstruction or a cardiac cause).
Calling a 50-69% stenosis a 70-99% stenosis when velocities are elevated but the waveform distal to the plaque remains low-resistance with brisk diastolic flow, or the converse when velocities are dampened by a proximal or cardiac cause.
Velocity thresholds shift with blood pressure, heart rate, aortic valve disease, and contralateral disease, and candidates apply a single fixed cutoff without checking whether the hemodynamics fit.
What to do instead
Always obtain a contralateral comparison and a distal waveform. If velocities and waveform disagree, report the discordance explicitly and recommend correlation rather than forcing a category. Rehearse the classic mimickers: aortic stenosis or low cardiac output lowering velocities, and contralateral occlusion or a tandem lesion raising them.
Misidentifying which vessel is being sampled on a lower-extremity arterial duplex, assigning a velocity to the superficial femoral artery when the sample gate sits in the profunda femoris or a collateral.
Anatomy is taught from diagrams, but on real patients the vessels overlap, collaterals mimic main vessels, and candidates chase color flow without confirming the vessel by its course and its relationship to the femur and the adductor canal.
What to do instead
Before sampling, trace the vessel proximally and distally in grayscale and confirm continuity with the expected anatomic course. Use named landmarks (femoral bifurcation, adductor hiatus, popliteal trifurcation) and document the segment, not just the velocity. Practice on the machine with a normal volunteer until vessel identification is automatic.
Interpreting an ankle-brachial index without confirming that the cuff and Doppler are correctly placed, that the patient rested supine for the required time, and that the higher of the two ankle pressures was used for each leg.
The ABI is treated as a simple calculation, so technique errors (cuff too small, Doppler over a calcified vessel, measuring after exercise, averaging instead of taking the highest pressure) go unnoticed and produce a wrong category.
What to do instead
Write a fixed checklist into your routine: rest period documented, correct cuff size, Doppler signal confirmed as arterial, highest ankle pressure per leg, and both brachial pressures. Recalculate the index by hand once per study to verify the machine. Know that a falsely high ABI in diabetes or renal disease should prompt a toe-brachial index.
Performing a venous reflux study with the patient supine, without a tourniquet or with the wrong cuff, and calling a segment competent because reflux was not provoked.
Reflux is a dynamic finding that depends on patient position and provocation, and candidates reproduce the protocol from a textbook without understanding that gravity and the provocation maneuver create the reflux being measured.
What to do instead
Standardize on the standing or reverse-Trendelenburg position with a distal compression or Valsalva maneuver appropriate to the segment, and document the provocation used. State the reflux threshold you applied and the duration measured. If the patient cannot stand, document the limitation and interpret cautiously rather than reporting competence.
Reporting a deep vein as thrombosed on the basis of non-compressibility alone when the vessel is not fully visualized, or reporting it as normal when color fill is present but compression was not performed.
Color Doppler can create false confidence, and candidates substitute color fill for the mandatory compression maneuver, or accept an incomplete study as complete.
What to do instead
Treat compression as the primary criterion and color as an adjunct. For every segment, document whether it was fully compressible, partially visualized, or not visualized. If a segment cannot be assessed (body habitus, cast, tenderness), state it in the report and recommend follow-up imaging rather than implying a negative study.
Measuring a dialysis access fistula flow volume or stenosis without accounting for the access configuration, the needle or catheter location, and the effect of the brachial artery steal on the feeding artery.
Access evaluation is taught as a set of numbers, and candidates report a flow volume without relating it to the access type, the feeding artery diameter, or the downstream limb perfusion.
What to do instead
Describe the access anatomy first (radiocephalic, brachiocephalic, graft, catheter), then measure feeding artery diameter and flow, the anastomosis, the outflow vein, and the deep draining veins. Interpret flow in the context of the access type and the clinical question (maturation failure, recirculation, steal). Include the brachial artery distal to the anastomosis when steal is suspected.
Preoperative vein mapping that reports only vein diameter and ignores compressibility, continuity, valves, depth, and the presence of a usable segment for the planned bypass or access.
Candidates treat mapping as a measurement exercise and forget that the surgeon needs a usable conduit, not a number, and that a non-compressible or deep vein changes the operative plan.
What to do instead
Report each vein segment by length and diameter, compressibility, depth from skin, continuity, and the presence of any focal narrowing or thrombosis. Mark the skin and note the best segment for the planned procedure. State limitations explicitly, such as a vein that is too deep or too small for the intended use.
Applying renal artery criteria to a transplanted kidney or to an accessory renal artery without adjusting for the different hemodynamics, and calling a normal transplant a stenosis.
Transplant and accessory arteries have different flow patterns and velocities than native main renal arteries, and candidates reuse native criteria without checking the literature or the anatomy.
What to do instead
Confirm the number and origin of renal arteries before interpreting velocities, and use transplant-specific thresholds for the transplant renal artery and its anastomosis. Measure the intrarenal waveform (resistive index, parvus-tardus) as supporting evidence. When uncertain, say so and recommend cross-sectional correlation rather than assigning a stenosis grade.
Ignoring infection control, machine settings, and patient safety details: reusing gel, not cleaning the probe between patients, leaving the output power high in obstetric or ocular scanning, or failing to document informed consent and patient identification.
Candidates focus entirely on the diagnostic content and treat safety and professional standards as background knowledge that will not be tested in a case-based way.
What to do instead
Memorize the practical rules you will be asked about: probe cleaning and high-level disinfection between patients, ALARA and output display indices, electrical safety around wet environments, and correct patient identification and consent documentation. Practice stating, in one sentence, what you would do differently in a given safety scenario, because the exam asks for behavior, not definitions.