Why is it difficult to detect an embolic stroke on an angiogram (Angiography)?

From the Guidelines

It is difficult to detect an embolic stroke on an angiogram because the imaging modality has limitations, including a lower sensitivity for detecting certain types of plaque ruptures and occlusions, particularly those that are small or have undergone early spontaneous clot lysis 1.

Limitations of Angiography

• The sensitivity of angiography for detecting complex plaques and plaque ruptures is lower compared to other imaging modalities such as intravascular ultrasound (IVUS) and optical coherent tomography, with approximately 10% of plaque ruptures depicted on IVUS being undetectable by angiography 1.
• Angiography may not be able to detect microvessel occlusions or early spontaneous clot lysis, which can result in a negative angiogram in up to 20% of patients with suspected cerebral ischemia 1.
• The presence of aortic arch disease or other concomitant pathologies can also make it challenging to interpret angiogram results and detect embolic strokes.

Importance of Comprehensive Angiogram

• A complete diagnostic cerebral angiogram of the affected territory, including a three or four-vessel pre-intervention diagnostic cerebral angiogram, is recommended to evaluate concomitant pathologies and anatomic variations, and to assess collateral flow from all possible sources 1.
• The use of additional imaging modalities, such as IVUS or optical coherent tomography, may be necessary to confirm the diagnosis of an embolic stroke and to guide treatment.

From the Research

Difficulties in Detecting Embolic Stroke on Angiogram

• The detection of embolic stroke on an angiogram can be challenging due to various factors, including the limitations of the imaging modality itself 2.
• Angiography may not always be able to show the occluded artery or the anastomotic pathways for cerebral circulation, making it difficult to confirm the diagnosis of embolic stroke 2.
• The use of non-ECG-gated computed tomographic angiogram may not provide diagnostic quality images of the heart and thoracic aorta, which can be a potential source of embolism 3.
• Cardiac computed tomographic angiography (CCTA) has been shown to be a useful modality for detecting high-risk cardiac sources of embolism in stroke patients, but it may not be able to detect all types of cardiac sources, such as patent foramen ovale or atrial septal aneurysm 4.

Risk Factors for Embolic Stroke on Angiogram

• The risk factors for incidental embolism after cerebral angiography include age, past history of cerebral infarction, anti-platelet therapy, neuro-intervention, and total amount of contrast medium used 5.
• The performance of the procedure by a resident operator has also been shown to be a significant risk factor for embolic complications 5.
• The use of MRI and magnetic resonance angiography (MRA) may be useful in evaluating cardiac sources of embolic stroke, but it has its own limitations and may not be able to detect all types of cardiac sources 6.

Limitations of Angiography in Detecting Embolic Stroke

• Angiography may not be able to detect embolic stroke in all cases, especially if the occluded artery is not visible or if the anastomotic pathways are not well-developed 2.
• The use of contrast medium may also be a limitation, as it can cause nephropathy or other adverse reactions 3, 5.
• The interpretation of angiogram results requires expertise and experience, and the accuracy of the diagnosis may depend on the skill of the operator 5.