Table 2.
Yakes Classification for peripheral arteriovenous malformations (AVMs).
| Type of AVMs | Angiographic manifestations |
|---|---|
| Ⅰ (arteriovenous fistula) | A direct artery to vein fistula connection |
| Ⅱ a | Multiple arteries and arterioles connecting to a typical “nidus” interconnecting vascular tubular structures that then drain into out-flow veins |
| Ⅱ b | Same as Type IIa except the “nidus” drains into an aneurysmal vein single out-flow vein |
| Ⅲ a | Multiple in-flow arteries and arterioles shunting into an enlarged aneurysmal vein that has a single vein out-flow. Fistulae are in the vein wall |
| Ⅲ b | Multiple in-flow arterioles shunting into an aneurysmal vein with multiple out-flow veins. The fistulae (nidus) are in the vein wall |
| Ⅳa | Multiple arteries and arterioles that branch in en passage fashion to form innumerable microfistulae that diffusely infiltrate the affected tissue. |
a
Because the tissue is viable and not devitalized, capillary beds must also be present among the innumerable arteriovenous fistulae. The innumerable micro fistulae drain into multiple veins. The tissues normal post-capillary venous drainage competes with the arterialized vein out-flow for drainage causing venous hypertension in tissue.