In AV-fistula there is shunting of blood from arteries directly into vein, bypassing the capillary beds. This causes fall in peripheral vascular resistance. Since Blood pressure is directly proportional to the peripheral vascular resistance, in AV-fistula there is fall in blood pressure and subsequent reflex tachycardia. When the artery proximal to the fistula is compressed, blood is no longer shunted and the peripheral vascular resistance is increased suddenly. This causes relative hypertension within 1 or 2 heartbeats. Bradycardia soon follows due to the activation of the baroreceptors in the Left ventricle (the Bezold-Jarisch reflex) Locally since no blood is being shunted, the swelling reduces and bruit/thrill disappears.
Nicoladoni–Branham sign
Bastian–Bruns sign
Crichton-Browne sign
Froment's sign
Mallet-Guy sign
Rovsing's sign
Hannington-Kiff sign
Hoover's sign 