A 42-year-old woman from Mumbai undergoes femoral artery catheterization for coronary angiography. During the procedure, the interventional cardiologist notes that the femoral artery puncture is slightly medial to the usual site. Post-procedure, the patient develops a pulsatile mass in the groin with a continuous 'machinery' murmur on auscultation. Duplex ultrasound confirms an arteriovenous fistula. Which vein was most likely injured during the arterial puncture?

Explanation

## Iatrogenic Arteriovenous Fistula in the Femoral Triangle ### Pathophysiology of AVF Formation An arteriovenous fistula (AVF) forms when a needle or catheter simultaneously punctures an artery and an adjacent vein, creating a direct communication. The continuous flow of high-pressure arterial blood into the venous system produces the characteristic **'machinery' murmur** and a palpable thrill. ### Anatomical Relationships in the Femoral Triangle | Vessel | Location | Relationship to Femoral Artery | Proximity | |--------|----------|--------------------------------|----------| | Femoral vein | Posteromedial | Immediately posterior and medial | **Very close** | | Great saphenous vein | Medial, superficial | Medial but enters vein below ligament | Distant | | Profunda femoris vein | Deep, lateral | Lateral and deep | Distant | | Lateral circumflex femoral vein | Deep, lateral | Lateral, within profunda system | Distant | **Key Point:** The femoral vein lies in **intimate anatomical proximity** to the femoral artery within the femoral sheath. During catheterization, a medial puncture of the femoral artery can easily traverse the arterial wall and penetrate the adjacent femoral vein, creating an AVF. ### Clinical Features of Femoral AVF **High-Yield:** The classic triad of iatrogenic femoral AVF: 1. **Pulsatile mass** (pseudoaneurysm or dilated vein from arterial shunting) 2. **Continuous 'machinery' murmur** (turbulent flow from artery → vein) 3. **Dilated, pulsatile veins** on ultrasound **Clinical Pearl:** Femoral AVF is the most common vascular complication of femoral artery catheterization, accounting for 0.5–2% of procedures. The risk is higher with larger sheaths, multiple punctures, and anticoagulation. ### Why This Location? A **medial puncture** of the femoral artery is more likely to injure the femoral vein because: - The vein lies posteromedial to the artery - A needle angled medially will pass through both the arterial and venous walls - The vein is immediately adjacent (separated by only the arterial wall and minimal tissue) **Mnemonic:** **VAN** (Vein, Artery, Nerve) — from medial to lateral in the femoral sheath. A medial puncture hits the vein. [cite:Harrison 21e Ch 297; Sabiston Textbook of Surgery 21e Ch 60]