Minor micro-rheological alterations in the presence of an artificial saphenous arteriovenous shunt, as an arteriovenous malformation model in the rat.

BACKGROUND: Arteriovenous malformations (AVMs) are vascular anomalies characterized by abnormal shunting between arteries and veins. The progression of the AVMs and their hemodynamic and rheological relations are poorly studied, and there is a lack of a feasible experimental model. OBJECTIVE: To establish a model that cause only minimal micro-rheological alterations, compared to other AV models. METHODS: Sixteen female Sprague Dawley rats were randomly divided into control and AVM groups. End-to-end anastomoses were created between the saphenous veins and arteries to mimic AVM nidus. Hematological and hemorheological parameters were analyzed before surgery and on the 1st, 3rd, 5th, 7th, 9th, and 12th postoperative weeks. RESULTS: Compared to sham-operated Control group the AVM group did not show important alterations in hematological parameters nor in erythrocyte aggregation and deformability. However, slightly increased aggregation and moderately decreased deformability values were found, without significant differences. The changes normalized by the 12th postoperative week. CONCLUSIONS: The presented rat model of a small-caliber AVM created on saphenous vessels does not cause significant micro-rheological changes. The alterations found were most likely related to the acute phase reactions and not to the presence of a small-caliber shunt. The model seems to be suitable for further studies of AVM progression.

A Microsurgical Arteriovenous Malformation Model on Saphenous Vessels in the Rat.

Arteriovenous malformation (AVM) is an anomaly of blood vessel formation. Numerous models have been established to understand the nature of AVM. These models have limitations in terms of the diameter of the vessels used and the impact on the circulatory system. Our goal was to establish an AVM model that does not cause prompt and significant hemodynamic and cardiac alterations but is feasible for follow-up of the AVM's progression. Sixteen female rats were randomly divided into sham-operated and AVM groups. In the AVM group, the saphenous vein and artery were interconnected using microsurgical techniques. The animals were followed up for 12 weeks. Anastomosis patency and the structural and hemodynamic changes of the heart were monitored. The hearts and vessels were histologically analyzed. During the follow-up period, shunts remained unobstructed. Systolic, diastolic, mean arterial pressure, and heart rate values slightly and non-significantly decreased in the AVM group. Echocardiogram results indicated minor systolic function impact, with slight and insignificant changes in aortic pressure and blood velocity, and minimal left ventricular wall enlargement. The small-caliber saphenous AVM model does not cause acute hemodynamic changes. Moderate but progressive alterations and venous dilatation confirmed AVM-like features. The model seems to be suitable for studying further the progression, enlargement, or destabilization of AVM.