The role of point-of-care ultrasound in the early recognition of type A aortic dissection
Dr Himanshu Gul Mirani
Case Presentation:
A patient presented following a sudden onset of central chest pain accompanied by transient collapse. The pain was described as sharp in nature and improved after administration of opioid analgesia. Initial observations were stable, with no significant inter-arm blood pressure difference (119/68 mmHg and 117/60 mmHg). Heart rate was 70 beats per minute and oxygen saturation was 98% on room air.
Electrocardiography did not demonstrate acute ischaemic changes. The patient later reported recurrent chest discomfort. Initial laboratory investigations, including cardiac troponin, were within normal limits.
Ultrasound findings suggestive of aortic dissection
Management and Outcome:
Point-of-care ultrasound (POCUS) was undertaken in view of ongoing symptoms and diagnostic uncertainty. This demonstrated a dilated aortic root, the presence of pericardial fluid, and a hyperdynamic left ventricle. The inferior vena cava appeared plethoric, suggesting elevated right-sided filling pressures. No clear intimal flap was visualised within the abdominal aorta.
Given these findings, an urgent CT aortogram was performed, confirming an acute Stanford type A aortic dissection. The patient was referred immediately for cardiothoracic surgical management.
Key Learnings and Points:
Ultrasound findings suggestive of aortic dissection
Bedside ultrasound can provide important early clues in suspected aortic pathology, particularly in unstable patients. Relevant findings include:
Dilatation of the aortic root or proximal ascending aorta
Visualization of an intimal flap within the aorta (although this is operator dependent and not always seen)
Pericardial effusion, which may indicate haemopericardium secondary to dissection extension
Aortic regurgitation on focused cardiac assessment
Regional wall motion abnormalities, if coronary artery involvement has occurred
Plethoric inferior vena cava, suggesting haemodynamic compromise or tamponade physiology
It is important to note that the absence of a visible flap does not exclude dissection, particularly when imaging windows are limited. Ultrasound should therefore be viewed as an adjunct rather than a definitive diagnostic modality.
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Role of D-dimer in aortic dissection
D-dimer testing has been explored as a potential rule-out tool in suspected aortic dissection. Elevated levels reflect activation of coagulation and fibrinolysis, which occurs in acute dissection.
A low D-dimer (typically <500 ng/mL) within the first 24 hours of symptom onset has a high sensitivity and may help exclude dissection in low-risk patients
However, specificity is limited, as D-dimer is elevated in numerous conditions including pulmonary embolism, infection, and malignancy
In patients with a high pre-test probability, D-dimer testing is not recommended as a decision-making tool. Reliance on a negative result in such cases risks false reassurance and diagnostic delay. Current practice favours immediate definitive imaging, such as CT aortography, when clinical suspicion is strong.
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It is worth noting that a plethoric IVC, in isolation, is non-specific. However, when combined with:
Pericardial effusion
Acute chest pain
Aortic root dilatation
it should raise strong concern for tamponade secondary to proximal dissection, which is a surgical emergency.