Aortic dissection is a serious medical emergency requiring immediate and precise attention. Prompt and accurate diagnosis is critical, as delays can lead to severe, life-threatening complications.
What is Aortic Dissection?
Aortic dissection occurs when a tear develops in the innermost lining of the aorta, the body’s largest artery. This tear allows blood to surge between the layers of the aortic wall, creating a “false lumen” alongside the original “true lumen.” This separation can disrupt normal blood flow to various organs or lead to fatal aortic rupture.
Aortic dissections are categorized by the Stanford classification system into two main types based on the affected aortic segment. Stanford Type A dissections involve the ascending aorta, the section closest to the heart, with or without involvement of the descending aorta. Stanford Type B dissections are confined to the descending aorta. Type A dissections carry a higher risk of complications like cardiac tamponade or coronary artery obstruction due to their proximity to the heart.
Patients experiencing aortic dissection report sudden, severe chest or back pain, often described as a tearing or ripping sensation. Symptoms also include a difference in blood pressure between the arms, or neurological symptoms if the dissection extends into arteries supplying the brain.
Chest X-rays: A First Look
A chest X-ray is a common imaging test that uses radiation to create images of the heart, lungs, and blood vessels. In an emergency, it is often one of the first tests performed when aortic dissection is suspected, providing a quick initial overview.
While a chest X-ray can offer clues, it is not a definitive diagnostic tool for aortic dissection. Suspicious findings include a widened mediastinum (broadening of the space between the lungs where the aorta resides), an abnormal aortic contour, inward displacement of aortic wall calcification, or a pleural effusion (fluid around the lungs). A left-sided pleural effusion may indicate blood leakage.
Despite these findings, chest X-rays have limitations in diagnosing aortic dissection. A normal chest X-ray does not rule out the condition, as a dissection can be present even with unremarkable findings. Sensitivity for detecting aortic dissection is estimated at 60-90%, meaning many dissections may be missed. Furthermore, chest X-ray signs are often non-specific and can be caused by other conditions. Therefore, a chest X-ray should not delay more accurate imaging when aortic dissection is strongly suspected.
Pinpointing the Diagnosis
Definitive diagnosis of aortic dissection relies on advanced imaging techniques. Computed Tomography Angiography (CTA) is the gold standard, providing detailed, cross-sectional images of the aorta. CTA involves injecting a contrast dye, highlighting blood vessels for visualization of the tear, true and false lumens, and dissection extent.
CTA offers exceptional sensitivity and specificity, reliably confirming the presence and characteristics of a dissection. This detailed visualization helps determine if branch arteries are affected or if there is bleeding into surrounding tissues. While non-contrast CT may show subtle signs like a high-density mural hematoma, contrast enhancement is needed for a comprehensive evaluation.
Magnetic Resonance Imaging (MRI) provides comprehensive images of the aorta, showing the intimal flap, true and false lumens, and blood flow patterns. MRI is useful for long-term follow-up and avoids radiation exposure, but takes longer. Transesophageal Echocardiography (TEE), using an esophageal probe, assesses the aortic valve and coronary artery involvement, especially in emergencies or when CT is unavailable.
Urgent Care and Treatment
Once diagnosed, aortic dissection requires immediate medical attention due to its rapid progression and high mortality if untreated. Initial management stabilizes the patient by controlling blood pressure and pain. Intravenous medications, such as beta-blockers, are administered to reduce heart rate and lower systolic blood pressure. Pain management, often with narcotics, is also part of initial care.
Treatment approaches for aortic dissection vary by Stanford classification. Stanford Type A dissections, which involve the ascending aorta, require emergency surgical intervention. During surgery, the damaged aortic section is resected and replaced with a synthetic graft. If the aortic valve is compromised, it is repaired or replaced.
Stanford Type B dissections, involving only the descending aorta, are often managed medically unless complications arise. Medical management involves blood pressure control and pain relief. However, if a Type B dissection becomes complicated by rapid aortic expansion, persistent pain, organ malperfusion, or signs of impending rupture, surgical or endovascular intervention is necessary. Endovascular repair, involving stent placement, is a treatment option for Type B dissections.