Transfemoral Digital Subtraction Angiography for Assessment of Vertebral Artery Occlusion in Rats
To the Editor:
The major disadvantage in rat models of global cerebral ischemia1 2 3 is the difficulty of occluding the vertebral artery through the alar foramina because the electrocoagulations are done “blind.” This mode of vertebral vessel occlusion is often unsatisfactory, and while postoperative selection on the basis of righting responses, EEG, and pupillary size is used in cerebral 4-vessel occlusion models,1 2 3 there is no substitute for demonstrating the completeness of the vascular occlusion . This “blind” vertebral occlusion technique might also explain the wide variation in cerebral blood flow measurements after brain 4-vessel occlusion.4 5 Furthermore, in the case of cerebral 2-vessel occlusion of the vertebral arteries, no validation parameter is available for confirmation that complete vertebral artery occlusion has been achieved. For all these reasons, we suggest the method of transfemoral digital subtraction angiography (DSA), which can be used for validation of successful vertebral artery electrocoagulation in rat models of global cerebral ischemia. DSA is the gold standard for the assessment of vascular occlusion. The DSA technique offers many advantages: it is a minimally invasive technique (5% mortality rate of 20 rats investigated), with high morphological resolution (Figures 1⇓ and 2), which can be used repeatedly. When a DSA catheter (Tracker 10; Boston Scientific) was used with radiographic guidance, no traumatic disruptions of the arterial blood vessel system were obtained in any of the rats examined. The use of a maximum of 1.5 mL of contrast solution (Solutrast; Byk Gulden) had no marked influence on rat arterial blood gases, mean arterial blood pressure, or heart rate. After DSA, some animals adopted a hunchbacked posture after femoral artery ligation and walked with extended paws for about 1 week. However, rapid collateralization of vessels in the area of occluded arteries into the rat groin area leads to partial recovery of the blood supply to the paws.
In the present study, assessment of adequate rat vertebral vessel electrocoagulation was demonstrated with transfemoral DSA. In 33% of the animals (6 of 20), only an incomplete vertebral vessel occlusion was achieved (Figure 1⇓). In contrast, Figure 2⇓ demonstrates a complete rat vertebral vessel occlusion in an earlier phase of vessel filling (1a) and a later state of contrast medium injection (1b).
In summary, transfemoral DSA seems to be a reliable technique for the validation of the completeness of vertebral artery occlusion in rat models of global cerebral ischemia (2- or 4-vessel occlusion).
The present study was financially supported in part by the Medical Faculty of the University of Heidelberg (FSP Geriatrie). The authors wish to thank Roland Galmbacher and Stephanie Schöppenthau for technical assistance.
- Copyright © 2000 by American Heart Association
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