Congestive heart failure due to traumatic arteriovenous fistula--two case reports.

Arteriovenous fistulas are abnormal connections between the high-pressure and high-resistance arterial system and the venous system with opposite features. Due to its lower resistance, the blood preferentially flows via the fistula rather than through the capillary bed. The amount of shunt flow depends on its size and proximity to the heart. Due to the increase in circulating volume, progressive dilation develops in the whole vascular system proximal to the shunt. Cardiomegaly and venous distention may return to normal after surgical repair of this vascular abnormality. Two cases are presented of heart failure due to traumatic arteriovenous fistula, one of which was between the right renal artery and inferior vena cava and the other between the left renal artery and renal vein.