RVT Ultrasound-Guided Procedures and Intraoperative Assessment — Questions and Answers
Question 1: What is the preferred ultrasound-guided intervention for an iatrogenic femoral pseudoaneurysm that fails compression therapy?
- Surgical ligation under general anesthesia
- Ultrasound-guided thrombin injection into the pseudoaneurysm sac (Correct answer)
- Balloon angioplasty of the puncture site
- Elastic compression bandaging for 72 hours
Correct answer: Ultrasound-guided thrombin injection into the pseudoaneurysm sac
Ultrasound-guided thrombin injection is the first-line treatment for pseudoaneurysms that do not respond to compression. A small volume of thrombin (100–500 units) is injected directly into the sac under real-time imaging, inducing rapid thrombosis while the neck is monitored to prevent inadvertent arterial embolization.
Question 2: During intraoperative TCD monitoring of a carotid endarterectomy, which finding should prompt the surgeon to insert an intraluminal shunt?
- MCA mean velocity increase of 15% after clamping
- MCA mean velocity decrease of more than 50% from pre-clamp baseline (Correct answer)
- Pulsatility index increase of 0.2 units
- Appearance of spectral broadening in the MCA waveform
Correct answer: MCA mean velocity decrease of more than 50% from pre-clamp baseline
A >50% drop in ipsilateral MCA mean velocity after carotid cross-clamping indicates inadequate collateral perfusion and cerebral ischemia risk. This threshold is widely used as the criterion for shunt placement to maintain cerebral blood flow during the endarterectomy.
Question 3: What is the primary duplex role during endovenous thermal ablation (EVTA) of the great saphenous vein?
- Confirming deep venous valve competence before ablation
- Guiding catheter tip placement and detecting endothermal heat-induced thrombosis (EHIT) post-procedure (Correct answer)
- Measuring total venous reflux time along the thigh
- Assessing arterial inflow to the limb
Correct answer: Guiding catheter tip placement and detecting endothermal heat-induced thrombosis (EHIT) post-procedure
Ultrasound guides correct catheter positioning (typically 2 cm distal to the saphenofemoral junction) and monitors tumescent anesthesia placement. Post-ablation, the technologist scans for EHIT — thrombus propagation into the deep system — which can occur in the first few days and requires classification and follow-up.
Question 4: Which intraoperative duplex finding after infrainguinal bypass graft creation most likely warrants immediate surgical revision?
- Graft diameter slightly smaller than the native tibial artery
- Focal peak systolic velocity ratio greater than 3:1 across an anastomotic segment (Correct answer)
- Mild color-flow turbulence immediately distal to the proximal anastomosis
- Phasic (triphasic) flow pattern throughout the graft body
Correct answer: Focal peak systolic velocity ratio greater than 3:1 across an anastomotic segment
A PSV ratio >3:1 across a focal segment indicates a hemodynamically significant stenosis (≥75% diameter reduction). When found intraoperatively before the wound is closed, it signals a technical defect — suture narrowing, intimal flap, or kinking — that should be corrected immediately to prevent early graft failure.
Question 5: Ultrasound-guided compression repair of a femoral pseudoaneurysm is MOST likely to fail or be contraindicated when the patient is:
- Undergoing anticoagulation therapy (Correct answer)
- Post-diagnostic (non-therapeutic) catheterization
- Female with a body mass index under 25
- Older than 70 years of age
Correct answer: Undergoing anticoagulation therapy
Anticoagulation significantly impairs the ability to thrombose the pseudoaneurysm sac during compression, making the procedure much less effective and requiring prolonged compression times. In anticoagulated patients, ultrasound-guided thrombin injection is the preferred alternative because it does not depend on the coagulation cascade.
Question 6: During ultrasound-guided central venous access, the primary advantage of real-time needle visualization over landmark technique is:
- Elimination of the need for post-procedure chest X-ray
- Confirmation of venous (vs. arterial) waveform before catheter insertion
- Direct visualization of needle tip position within the target vessel lumen in real time (Correct answer)
- Automatic calculation of catheter depth required
Correct answer: Direct visualization of needle tip position within the target vessel lumen in real time
Real-time ultrasound guidance allows the operator to see the needle tip entering the vessel lumen, confirming correct placement before guidewire advancement. This directly reduces complications such as inadvertent arterial puncture, pneumothorax, and posterior wall perforation compared to landmark-only technique.
RVT Ultrasound-Guided Procedures and Intraoperative Assessment
What is the preferred ultrasound-guided intervention for an iatrogenic femoral pseudoaneurysm that fails compression therapy?