NEUROIMAGING / DSA
Balloon Test Occlusion (BTO)
Created 29/04/2021, last revision 16/04/2022
- acute internal carotid artery (ICA) occlusion is associated with a high risk of ischemic neurological deficit (20-49%) (Seet, 2012)
- in a metanalysis of 20 studies on patients with ICA occlusion, the annual stroke risk was 5.5% (2.1% ipsilateral). Those with hemodynamic compromise on functional imaging had a stroke risk of 12.5% (9.5% ipsilateral)
- the clinical course of ICA occlusion is variable, from asymptomatic lesions to devastating strokes (Klijn, 1997)
- the balloon test occlusion (BTO) is performed to see whether an artery can be temporarily or permanently closed without significantly affecting the brain perfusion
- if the BTO is well tolerated, the risk of subsequent ischemia is considerably lower
- pharmacologically induced hypotension during BTO further increases the test sensitivity
- pharmacologically induced hypotension during BTO further increases the test sensitivity
Indications
- functional test in patients scheduled for ICA occlusion (inoperable aneurysms, glomus tumor, intracranial tumors, tumors in the ENT region)
- the Matas test was performed earlier (external CCA compression during angiography); it was replaced by more sensitive balloon test occlusion (BTO)
Procedure
Patient preparation
- allergy premedication (if required)
- premedication with NIMOTOP 60mg (2 tablets) every 4h
- insert a urinary catheter and intravenous cannula
- start Normal saline solution at 150 mL/h at least 4h before the procedure
- ensure anesthesiologist supervision
- i.v. heparinization at the beginning of the procedure
- bolus of 5000-7000 IU of undiluted HEPARIN (1 – 1.4 ml)
- dilute heparin – 4ml (1ml = 5000jj) + 16ml of NS (20ml solution = 20 000jj)
- followed by i.v. diluted HEPARIN 1-3 ml/h (1000-3000 IU/h) with the target APTT 2-3x
- flush the distal catheter section above the balloon with the normal saline + low dose of heparin
- HEPARIN 0.5 ml (500IU) + 500 ml of NS (1ml=1IU) – cont. 60ml/h (1IU/min) [Standard, 1995]
Clinical and TCCD evaluation during procedure
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Assessment of collateral circulation
- assess ACA (A1-A4 segments) and MCA (M1-M4 segments) contrast filling on the occluded side (Kikuchi, 2014]
- assess the anatomy of the circle of Willis (especially the presence and quality of ACoA and PCoA, A1 and P1 portions bilaterally)
Complications
- neurological complications: 0-8.3% (average complication rate according to various studies ~ 2.2%) → more here