THE USE OF XE-133 FOR MEASUREMENT OF BLOOD-FLOW THROUGH SYSTEMIC ARTERIOVENOUS-MALFORMATIONS BEFORE AND AFTER THERAPEUTIC EMBOLIZATION

Embolization is increasingly used to treat systemic arteriovenous (AV) shunts although its success, as judged by either angiographic or clin ical means, is difficult to quantify. The aim of the study was to quan tify blood flow through AV shunts with Xe-133, which, because of its r elatively long transit time through peripheral tissues, behaves like m icrospheres. Following arterial injection, Xe-133 entering an AV shunt rapidly arrives in the lung and can be quantified with a scintillatio n probe. In 17 patients with systemic AV shunts, the reduction in shun t flow following therapeutic embolization was quantified in the angiog raphy theatre by comparing the initial count rates in the lung, record ed by probe, following injection of identical quantities of Xe-133 int o a supplying artery before and after embolization. By comparing the l ung counts with those given by an intravenous injection of Xe-133, the fraction of flow at the catheter tip entering the shunt was also quan tified. Tissue perfusion in the vascular territory distal to the shunt was measured at the same time by recording the clearance of non-shunt ed Xe-133 with a second probe over the extremity. Control injections o f Xe-133 were given in the contralateral limb in order to assess Xe-13 3 transit in the absence of shunting and to compare tissue perfusion b etween the two sides. Shunt flow ranged from 40% to 100% (of that at t he tip of the catheter) (n = 14), while the reduction in shunt flow fo llowing embolization ranged from 15% to 96% (n = 19). Tissue perfusion distal to the shunt and in the contralateral limb was about 5 ml 100 ml(-1) min(-1) Contrast medium had no consistent effect on tissue perf usion in either limb, or on shunt flow. There was no difference in per ipheral perfusion between the abnormal and control sides, nor any sign ificant difference in perfusion in the distal tissue on the abnormal s ide before and after embolization. There was, however, a consistent in crease in the fraction of the injected Xe-133 delivered to the distal tissue after embolization (median increase 93%, p < 0.001). The techni que is relatively simple and merits further development as a means of continuous quantification of systemic AV shunt flow in the angiography theatre at the time of embolization.