From the Guidelines
The Modified Allen Test (MAT) is no longer considered a useful tool for assessing the risk of hand ischemia before procedures involving the radial artery, such as arterial line placement or radial artery harvesting for coronary artery bypass grafting. The purpose of the MAT has been reevaluated in recent years, and the most recent evidence suggests that it is not necessary to perform this test before radial artery access 1. The test was previously used to assess the patency and collateral circulation of the radial and ulnar arteries in the hand, but its utility has been called into question by recent studies 1.
Historical Context
Historically, the MAT was used to assess the adequacy of ulnar artery flow to the hand, which is essential for maintaining perfusion if the radial artery is compromised 1. The test involved a series of steps to evaluate the color return to the hand after occlusion of the radial and ulnar arteries. However, recent evidence suggests that this test is no longer necessary and may even be considered of historical interest only 1.
Current Recommendations
Current recommendations suggest that the MAT is not a reliable predictor of hand ischemia and should not be used to determine the suitability of radial artery access 1. Instead, other factors such as the presence of a radial pulse, the patient's overall vascular health, and the specific procedure being performed should be taken into account when deciding on the approach to use.
Key Points
- The MAT is no longer considered a useful tool for assessing the risk of hand ischemia
- Recent evidence suggests that the test is not necessary before radial artery access 1
- Other factors should be considered when deciding on the approach to use, such as the presence of a radial pulse and the patient's overall vascular health 1
From the Research
Purpose of the Modified Allen Test (MAT)
The Modified Allen Test (MAT) is used to assess the adequacy of blood supply to the hand through the ulnar artery 2, 3. The test is performed to evaluate collateral circulation prior to arterial cannulation, particularly when intravascular access to the radial artery is planned 2, 4.
Key Aspects of the MAT
- The test involves compressing both the ulnar and radial arteries while the patient makes a fist, causing the hand to blanch 3.
- The patient is then asked to extend their fingers, and the examiner releases the ulnar artery while maintaining pressure on the radial artery 3.
- A return of normal color to the hand indicates adequate collateral circulation 3.
Clinical Applications
- The MAT is used to assess the risk of ischemic complications in patients undergoing transradial cardiac coronary angiography 4.
- The test can help determine the suitability of the radial or ulnar artery for grafting purposes, such as coronary angiosurgery 5.
- The MAT can also be used to evaluate the arterial supply of the hand in left- and right-handed individuals, and in both left and right hands 5.