From the Guidelines
A balloon test occlusion (BTO) procedure involves a series of steps to evaluate whether a patient can tolerate permanent occlusion of a blood vessel, including obtaining informed consent, baseline neurological examination, cerebral angiography, systemic heparinization, temporary occlusion with a non-detachable balloon, and continuous neurological monitoring. The procedure begins with obtaining informed consent after explaining risks including stroke 1. First, the patient undergoes:
- Baseline neurological examination
- Cerebral angiography to assess vascular anatomy 1. Next, systemic heparinization is administered (typically 5000-7000 units of heparin) to prevent thrombus formation 1. The interventionalist then places a catheter into the target vessel and inflates a non-detachable balloon to temporarily occlude blood flow. Confirmation of complete occlusion is verified with contrast injection 1. During the occlusion period (typically 20-30 minutes), the patient undergoes:
- Continuous neurological monitoring with serial examinations every 2-5 minutes to assess for deficits
- Additional monitoring may include EEG, SSEP, or cerebral perfusion studies like Xenon CT or SPECT 1. Blood pressure is carefully monitored and sometimes deliberately lowered to stress the collateral circulation (hypotensive challenge) 1. If the patient tolerates the test without developing neurological deficits, they are considered to have passed the BTO, suggesting they may tolerate permanent vessel sacrifice 1. The balloon is then deflated and removed, and the patient is observed for post-procedure complications 1. This test is crucial before procedures like parent vessel sacrifice for aneurysms or tumor resections involving major vessels, as it helps predict the risk of ischemic complications 1.
From the Research
Balloon Test Occlusion Procedure Steps
The steps of a balloon test occlusion (temporary endovascular occlusion) procedure are not explicitly outlined in a single study. However, based on the provided evidence, the following steps can be inferred:
- Balloon test occlusion is typically performed under normotensive conditions with distal perfusion of heparinized saline for a specified period, usually 20 minutes, or until a deficit is perceived 2.
- The procedure may involve the use of complementary techniques such as transcranial Doppler (TCD) to monitor cerebral haemodynamics in real-time 3.
- Hypotensive challenge may be induced during the procedure to evaluate the patient's tolerance to occlusion 2.
- The procedure may involve the measurement of stump pressure ratio and venous phase delay to assess collateral flow 4.
- The patient's clinical tolerance to the occlusion is monitored, and the procedure may be terminated if any deficits are perceived.
Indications and Methods
The indications for balloon test occlusion include evaluating whether a patient will be able to tolerate permanent occlusion of an extracranial or intracranial vessel 5. The methods used in balloon test occlusion may vary, but they typically involve the use of a balloon catheter to temporarily occlude the vessel 4, 3, 2. The predictive value of balloon test occlusion is high, but controlled trials are necessary to determine its specificity compared to quantitative imaging 2.
Complications and Safety
The complications of balloon test occlusion may include symptomatic complications, asymptomatic arterial dissections, and ischemic or thromboembolic complications 2, 6. The safety of balloon test occlusion has been evaluated in several studies, and it has been found to be a safe procedure with low complication rates 6.