[Iatrogenic arteriovenous fistula from the internal mammary artery. Spontaneous closure]

Two cases of arteriovenous fistula arising from the internal mammary artery are described. The detection of the continuous subclavian murmur was preceded by therapeutic procedures in both cases; difficult subclavian vein catheterisation in the first; reoperation of sternotomy for postoperative haemorrhage after open heart mitral commissurotomy in the second. Oxymetry after sampling at, above and below the subclavian vein confirmed the presence of a shunt and allowed estimation of shunt flow, which was minimal in both cases, 11 and 32% of cardiac output respectively. The origin of the fistula at the internal mammary artery and the communicating vein were identified by semi-selective angiography. The latter was superior vena cava in the first case and the internal mammary vein in the second. The low shunt flow probably explains the outcome: spontaneous closure in both cases. This is exceptional in any form of arteriovenous fistula.