An intimal flap is a tear in the innermost lining of an artery, most often affecting the aorta, the body’s largest blood vessel. This condition is serious because it frequently accompanies aortic dissection, a life-threatening event where blood surges between the layers of the aortic wall, causing them to separate. Prompt identification and treatment are crucial to prevent severe complications.
Understanding an Intimal Flap
An intimal flap refers to a separation of the intima, the innermost layer of an artery, from the media, the middle layer. This detachment creates a new channel, known as a false lumen, through which blood flows alongside the original, true lumen. While intimal flaps can occur in various arteries, they are most commonly observed in the aorta due to its size and high pressure.
When an intimal flap forms, particularly in the aorta, it often leads to aortic dissection. Blood enters the tear in the intima, forcing its way into the media, splitting the layers apart and creating the false lumen.
There are different presentations of intimal flaps. Focal intimal flaps (FIFs) are small irregularities of the aortic lining, usually less than 4 cm in length, that project into the vessel’s interior without an associated blood clot within the wall or a full dissection. These are often found incidentally in asymptomatic individuals undergoing imaging for other aortic conditions.
In contrast, an intimal tear without hematoma, also known as a limited intimal tear (LIT), involves a localized tear in the intima and superficial media, but without extensive blood accumulation or false lumen formation. These tears can still cause localized bulging of the aortic wall.
Factors Leading to an Intimal Flap
High Blood Pressure
Uncontrolled high blood pressure, or hypertension, is a significant contributor. It places chronic, elevated pressure on arterial walls, leading to their deterioration and making the aorta’s layers more susceptible to tearing.
Atherosclerosis and Smoking
Atherosclerosis, characterized by the hardening and narrowing of arteries due to plaque buildup, also plays a role. Advanced atherosclerosis can lead to penetrating aortic ulcers, which may trigger an intimal tear. Smoking further accelerates atherosclerosis, increasing the risk of intimal flap formation.
Genetic and Congenital Conditions
Certain genetic connective tissue disorders, such as Marfan syndrome, Ehlers-Danlos syndrome, and Loeys-Dietz syndrome, predispose individuals to intimal flaps and aortic dissections. These syndromes weaken the aortic wall’s elastic fibers, making it prone to tearing. Bicuspid aortic valve, a congenital heart defect, and coarctation of the aorta are also associated with increased risk due to structural abnormalities.
Traumatic Injuries
Traumatic chest injuries, such as those sustained in accidents, can directly cause an intimal tear due to sudden, forceful impact on the aorta.
Detecting an Intimal Flap
Computed Tomography (CT)
CT scans, particularly CT angiography (CTA), are often the first-line diagnostic tool due to their widespread availability and rapid image acquisition. CTA clearly shows the intimal flap separating the true and false lumens and can identify associated blood clots within the aortic wall.
Magnetic Resonance Imaging (MRI)
MRI provides detailed images of the aorta and is highly accurate in detecting intimal flaps and assessing the extent of dissection. MRI can differentiate between the true and false lumens and is useful for identifying intramural hematomas (blood collections within the aortic wall without a clear intimal tear).
Echocardiography
Echocardiography, including transthoracic (TTE) and transesophageal (TEE), is another valuable imaging modality. TEE, performed by inserting a probe down the esophagus, offers a detailed view of the aorta, especially the ascending aorta and aortic arch, with high sensitivity. It can assess flap movement and blood flow patterns using color Doppler. However, TEE has a blind spot where the trachea obstructs visualization, making CT or MRI a useful complement for a comprehensive assessment.
Managing an Intimal Flap
Medical Therapy
Initial stabilization involves immediate medical therapy to reduce stress on the aorta. This includes strict control of blood pressure and heart rate with medications like beta-blockers. Pain management is also important.
Conservative Management
For certain types of intimal flaps, particularly focal intimal flaps (FIFs) found incidentally in asymptomatic patients with stable aortic disease, a conservative management approach involving close monitoring is often adopted. These FIFs show little growth and rarely lead to acute aortic events. Regular imaging surveillance tracks any changes in the flap’s dimensions or the development of associated complications.
Surgical Intervention
When an intimal flap is associated with acute aortic dissection, especially involving the ascending aorta (Stanford Type A dissection), urgent surgical intervention is typically recommended due to the high risk of severe complications. Surgical goals include excising the intimal tear, repairing or replacing the damaged aortic segment, and obliterating the false lumen to restore normal blood flow. For dissections involving the aortic root or valve, specialized procedures may be necessary.
Endovascular Repair
Endovascular repair, a less invasive option, involves placing stents to seal the intimal tear or create a re-entry point between the false and true lumens. This can be considered for certain cases, particularly those with complications like compromised branch arteries, to restore adequate blood flow to affected organs without open surgery.