Aortic dissection is the detachment of the inner wall layer of the aorta, the intima, from the middle wall layer known as the media. In most cases, aortic dissection originates from an injury or tear to the intima, which forms the portal of entry for hemorrhage. The hemorrhage can lead to widening of the dissection and avulsion of branching arteries, with all the resulting consequences.
What is aortic dissection?
Aortic dissection is a splitting of the three-layered vessel walls of the aorta. The starting point for the development of an aortic dissection is usually a tear or lesion of the inner wall, the intima. The tear or lesion forms the gateway for hemorrhage between the intima and adventitia, the outer vessel wall, and into the middle layer, the media, respectively. Because of the bleeding between the wall layers associated with the dissection, aortic dissection is also aptly called aneurysm dissecans aortae or burrowing hemorrhage. The immediately life-threatening dissection affects about 60 percent of the ascending branch of the aorta. In rarer cases, however, aortic dissection can occur in all sections of the aorta. The hemorrhage results in a double lumen, which can cause branching arteries to tear off. As a result, their target areas can no longer be supplied with arterial blood and are at risk of acute oxygen starvation (ischemia). Due to the hemorrhage pulsating with the heartbeat, the aortic dissection can spread further within the aortic walls and cause the most severe damage. In principle, dissection can extend over a few millimeters to several centimeters or, in extreme cases, over the entire length of the aorta.
Causes
The most common cause of aortic dissection is thought to be arteriosclerotic changes in the intima or degenerative weakness of the media. The elasticity of the intima is reduced by arteriosclerotic changes. This causes narrowing of the aorta in the course of its windkessel function. Thus, in extreme cases, the vasodilatations, which constantly occur in rhythm with the heartbeat, can rupture. Another complex of causes is mediadegeneration, which can result from untreated chronic high blood pressure or, in rarer cases, from a congenital weakness of the connective tissue of the media. Genetic mediadegeneration leads to loss of its elasticity, so that the aorta no longer constricts properly after passive vasodilatation during ventricular systole. The media acts as if “worn out” so that the intima is subjected to severe stretching stresses, which can cause rupture with subsequent hemorrhage.
Symptoms, complaints, and signs
Symptoms and complaints of aortic dissection cover a wide range from not noticeable to sudden death. Sudden death can result from a tear in the ascending portion of the aorta or from occlusion of a coronary artery. In the vast majority of cases of aortic dissection, there is a sudden onset of severe pain. These are usually described as tearing or stabbing and are perceived by the affected person as extremely threatening. The localization of the pain provides the first clues to the section of the aorta affected by dissection. Often, the acute pain is so severe that unconsciousness occurs. Other symptoms such as shortness of breath, pain in the extremities, signs of a stroke, and paralysis may occur in addition to the leading symptoms.
Diagnosis and course
After initial suspicion based on leading symptoms that have occurred, x-ray and ultrasound examinations, especially transesophageal echocardiography (TEE), can provide further insight. Computed tomography (CT) and magnetic resonance imaging (MRI) provide even more detailed images. The disease course of aortic dissection is unpredictable. In some cases, blood between the walls finds its way back into the “proper” lumen through another opening in the intima, reducing the acute risk of widening of the dissection. In other cases, the dissection progresses episodically, affecting other areas of supply such as the extremities, kidneys, and digestive organs. There are also known cases in which a thrombus closes the opening in the intima, leading to apparent self-healing.The most dangerous course occurs when the outer layer of the wall, the adventitia, is so dilated by the bulge between the walls that it ruptures, allowing almost all of the blood of the great circle of the body to escape from the aorta, leading to fatal bleeding to death within a very short time.
Complications
Untreated aortic dissection can cause a number of serious complications, including sudden death. The type of aortic dissection is critical to the type of complications that occur as a sequelae. The least serious complications occur when the bleeding into the space between the inner wall (intima) and the media, the elastic middle wall of the aorta, finds its way back into the “proper” lumen of the aorta after only a short distance. In this case, the cascade of mutually reinforcing symptoms and complications is initially interrupted. It is possible for a very small aortic dissection to remain asymptomatic and complication-free in exceptional cases. In the vast majority of cases, aortic dissection is accompanied by stabbing pain that may be severe enough to cause temporary unconsciousness. The development of further complications depends on the course of the dissection. In cases where it causes high-grade stenosis, further complications result from reduced blood flow to internal organs such as the liver, kidneys, and intestines, as well as to the lower body. Particularly serious and immediately life-threatening complications can arise if the aortic dissection takes a progressive course. Under certain circumstances, the entire length of the aorta is affected by the hemorrhage. There is then also an increased risk of rupture of the aorta with the risk of internal hemorrhage resulting in death.
When should you see a doctor?
Symptoms of aortic dissection range from barely noticeable to sudden death because the extent of bleeding between the inner wall of the aorta (intima) and the middle wall (media) can vary widely. A diagnosed aortic dissection requires immediate action because progression and thus further complications are unpredictable. The progression of the disease depends primarily on the causative factors of the aortic dissection. There is always a risk that the separation of the intima from the media will dilate in minutes due to the pulsatile change in blood pressure between systole and diastole, leading to an immediately life-threatening situation. A slight relaxation is only called for when the blood entering between the intima and media can re-enter the “proper” lumen of the aorta through a second tear in the intima. The risk of unpredictable widening of the aortic dissection is significantly reduced by the backflow of blood. Postponing any necessary further diagnostic testing by imaging techniques such as MRI can be life-threatening, because in some situations only rapid, surgical intervention can save lives. There is no conceivable single clinical picture that could justify postponing treatment in an appropriately equipped clinic. The clinic should have the necessary diagnostic procedures- and invasive or minimally invasive treatment options.
Treatment and therapy
Once acute aortic dissection has been diagnosed, the most important measure is to prevent imminent rupture of the aorta. This means that initially, antihypertensive measures should reduce systolic pressure to 110 mmHg. In parallel, pain-relieving drugs are used. If the dissection is localized in the ascending branch of the aorta, surgical replacement in this area with an artificially created vascular prosthesis is usually urgently indicated. If the dissection is confined to the descending branch of the aorta and is therefore less threatening, treatment initially consists of drug therapy. If the dissection is precisely analyzed and localized, so-called percutaneous intimal membrane fenestration (PFA) may also be used. Stents are inserted via percutaneously inserted catheters and the intimal tears are virtually glued to the stents. Frequently, blocked or sheared arterial branches are also attempted to be dilated, repositioned and made functional again during the procedure.
Outlook and prognosis
The prognosis for aortic dissection carries a high risk of death in all its forms, although this has improved markedly in recent decades. Whereas nearly 50 years ago the disease was almost always fatal, today less than 20% of people die from the defect within a month of onset. Without medical care and surgical intervention, a fatal outcome occurs in about half of those affected. The likelihood of survival from an aortic dissection increases if immediate medical care is initiated when the health condition is acute. In addition, it is helpful if blood pressure and general condition are checked at regular intervals and precautions are taken. This reduces mortality. With increasing age, the risk of disease from aortic defect increases significantly due to age. Most sufferers are over the age of 65 on average. With a vascular prosthesis and drug treatment, sufferers have a comparatively good prognosis. However, approximately 10% of sufferers still die within the first year after dissection. In addition, patients face life-limiting measures. They are physically and emotionally less resilient. Excitement, stress, and hectic activity increase the risk, and there is an increased risk of further vascular damage as well as recurrence of aortic dissection.
Prevention
There are few preventive measures that cannot completely eliminate the risk of aortic dissection, but at least reduce it. It is particularly important to maintain systolic blood pressure at a normal level of 120 to 140 mmHg and to examine by ultrasound at regular intervals of one to two years (depending on age), for example, the carotid arteries for possible deposits (plaques). This is especially true if one of the genetic defects is present that leads to degeneration of the middle layer of the vessels, the media, and increases the risk of aortic dissection in the longer term.
Follow-up
For patients suffering from aortic dissection, regular follow-up is extremely important. Intervals between three and six months are recommended, after which a follow-up examination should be performed annually. During this examination, blood pressure is checked or, if necessary, adjusted to values around 120/80 mmHG. In addition, a KM-CT examination is performed to check the aorta and to be able to document the course of the disease. An overall view of the aorta is very important in order to be aware of any changes in diameter or newly added hematomas. If necessary, this can also detect a dilated aorta at an early stage and enable rapid treatment. In about one-third of patients, the disease progresses within five years or they suffer an aortic rupture (tear in the aortic wall), requiring further surgical treatment. Affected individuals with implanted coronaries (coronary arteries) must undergo regular ergometric follow-up. If stenosis (narrowing of a blood vessel) is suspected, coronary angiography (radiological imaging of the vessel) must be performed. In patients whose heart valves have been reconstructed, echocardiography should be performed annually. In addition, regular organ checks, neurologic checks, and pulse status checks are also recommended.
Here’s what you can do yourself
For patients after aortic dissection, there are a few things to keep in mind. The procedure not only affects cardiac output and, consequently, fitness, but also the surrounding chest muscles. Therefore, it is appropriate to strengthen them. However, it is important that this is done gently in the first period. For this purpose, a Theraband can be used, which is wrapped around the wrists and, through slight external rotation of the wrists, strengthens the upper arm muscles and thus also indirectly the chest muscles. More forced muscle training of the direct chest muscles is only appropriate after about six to eight months. Boxing and punching movements must be avoided at all costs in the first period, as these may cause stimulus transmission that can jump from the chest muscles to the heart muscle, which can lead to overstressing of the heart. Furthermore, heavy lifting and press breathing should be avoided, as these also place unnecessary stress on the heart.Likewise, coughing should be modified into coughing, if possible, to relieve pressure in the chest area. Individual adherence to these restrictions should always be discussed with the attending physician and physiotherapist. Later, modified push-ups on the wall and light water gymnastics can be started to increase the general condition and thus the fitness.
