An 82-year-old grandmother falls and cannot move her legs. A 33-year-old computer programmer with no medical problems suddenly develops severe back pain. A 24-year-old daycare worker suddenly cannot breathe.
These are all patients with very different clinical scenarios but have one explanation. They are affected by acute thoracic aortic syndrome. In most cases, this syndrome is related to an undiagnosed thoracic aortic aneurysm.
The aorta is the largest artery in the human body and is the source for every other arterial branch. While aneurysms can occur in any arterial branch, aneurysms that directly involve the thoracic aorta can remain silent for years until they develop catastrophic complications.
These aneurysms occur in about one in 10,000 people a year and most commonly involve the first two segments of the aorta: the root and ascending. Often patients become aware of an aneurysm through imaging studies performed for completely unrelated reasons. This often results in confusion and fear, as management and treatment options are less well known than for other more common cardiovascular conditions.
The risk factors for aneurysmal degeneration of the thoracic aorta are common to other cardiovascular diseases. Smoking, hypertension and hypercholesterolemia can all contribute to aneurysm formation. Although the vast majority of thoracic aortic aneurysms are spontaneous, some patients will have forms that are inherited and possibly even related to congenital and genetic syndromes that can be identified through testing.
Some of the specific genetic syndromes, such as Marfan syndrome, will have physical characteristics that can be screened for by many physicians, while other syndromes may have much more subtle physical findings. Patients with congenital abnormalities such as bicuspid aortic valves can also be at risk for thoracic aortic aneurysms. There is also an association between thoracic aortic aneurysms and abdominal and cerebral aneurysms.
The natural history of thoracic aortic aneurysms is one of slow, asymptomatic growth. Aneurysms that reach over 4 centimeters are more likely to develop acute aortic syndrome, and the greater the size of the aneurysm the higher the risk.
Acute aortic syndrome includes aortic pathology in which there is a breach of the aortic wall. This includes aortic ruptures, aortic dissections, intramural hematomas and penetrating aortic ulcers.
The risk of acute aortic syndrome increases with the size of the aorta, but this is proportional to patient size. Traditionally, the aortic size could be indexed to body surface area. However, it is now thought that body weight has little impact on aortic size, and indexes based on height have been shown to have acceptable correlation to risk of complications.
Therapy for thoracic aortic aneurysms is focused on prevention of growth and reduction in risk of complications. The most widely used medication in the setting of thoracic aortic aneurysm is a beta blocker. In studies of Marfan patients, beta blockers have been shown to reduce the rate of growth. Given their mechanism as anti-impulse therapy, beta blockers are thought to reduce sheer stress on the aortic wall by lowering both heart rate and blood pressure.
The optimal threshold for blood pressure is not known, but current guidelines for patients with cardiovascular disease recommend reduction of the systolic blood pressure to less than 130 mmHg and diastolic to less than 80 mmHg. There is also limited data to suggest an additional benefit with a systolic blood pressure target of less than 120 mmHg.
In studies of Marfan patients, therapy with angiotensin receptor blockers has shown a benefit in slowing the rate of aortic growth. The rate of reduction was similar to that found with beta blockers. There is mixed data on the combination of beta blockers and angiotensin receptor blockers, but these are often used in patients with elevated cardiovascular risk and who require multidrug therapy for treatment of their hypertension.
As many patients with thoracic aortic aneurysms share other cardiovascular risk factors, it is important to address all aspects, not just hypertension, to maximize risk reduction. Smoking cessation should be managed, and patients with evidence of atherosclerotic disease should be placed on statin therapy. Appropriate patients should be placed on high-intensity therapy, and, if not tolerated, moderate intensity therapy should be tried.
The benefits of statin therapy may extend beyond the control of atherosclerosis and lowering of LDL. In modifying matrix metalloproteinases, statin therapy can stabilize thoracic aneurysms and reduce preoperative and postoperative complications.
Continued surveillance is an important adjunct to medical therapy. All patients with thoracic aortic aneurysms should have transthoracic echocardiography to assess the aortic root and aortic valvular anatomy and function. Additionally, dedicated imaging with CT or MRI is necessary for precise measurements of aortic diameters and to establish baseline sizes.
A subsequent imaging study, preferably the same type as the initial study, should be repeated in six to 12 months to establish stability. Wellstar prefers thin-slice CT with contrast as appropriate for all studies as they are widely available, well tolerated and easily reproducible and comparable. Once stability has been established, further studies can be performed in six to 24-month intervals as dictated by the clinical scenario.
Despite maximal medical therapy (MMT), there are patients who require surgical intervention. The decision to proceed to surgery is based primarily on aortic size for each given aortic segment. The rate of growth and factors such as family history of aortic complications or connective tissue disorders are also carefully evaluated to determine the optimal time for surgical intervention.
The techniques for surgery have evolved significantly over the last few decades and have resulted in marked reductions in perioperative morbidity and mortality. Hybrid and totally endovascular procedures are becoming more common and add to less invasive options for patients in need of interventions.
The diagnosis and management of thoracic aortic aneurysms often spans multiple specialties and requires integrated information systems and a coordinated effort by all involved practitioners. This is reflected in the most recent update to the American College of Cardiology and American Heart Association guidelines in which care by an integrated aortic team is described and used to determine appropriate intervention thresholds as a reflection of the improved outcomes in these settings.
As more is learned about the individual genetic characteristics and overall risk factors for aortic complications, the appropriate therapy can become more tailored to each patient. Shared decision-making is paramount in caring for patients with thoracic aortic aneurysms. Often this is best accomplished in a dedicated aortic clinic with resources that span from genetic testing to surgical intervention. With appropriate management, patients with thoracic aortic aneurysms can lead full and productive lives.
Dr. James Burke
Dr. Burke is a cardiothoracic surgeon with Wellstar Center for Cardiovascular Care. He received his medical degree from the Emory University School of Medicine. Dr. Burke is board certified by the American Board of Thoracic Surgery and sees patients in Marietta and LaGrange.
References
- 2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines. Isselbacher, et al., Circulation. 2022; 146:e334-e482
