Guidance for Deadly Thoracic Aortic Diseases

Most clinicians are familiar with the typical symptoms of dissection of the thoracic aorta: severe, tearing pain of sudden onset, beginning in the anterior chest and then radiating to the back and often associated with extreme exertion or emotion. Unfortunately, patients have a habit of not reading medical texts and present with less dramatic and classic complaints. They sit in waiting rooms, then have electrocardiograms and chest radiographs that, if normal, lead to reassurance. The resultant delays in making the diagnosis and initiating appropriate medical and surgical treatment precipitate many deaths and lawsuits each year. These unfortunate situations are even more poignant when the patient is young and is evaluated only for costochondritis, pleurisy, or a myocardial infarction, which are ruled out, and is discharged from the emergency department, only to die at home. Some of these undiagnosed patients will have an unexplored family history of aortic aneurysm or dissection or will have overlooked physical signs of a syndrome that predisposes to thoracic aortic disease, but these vital clues are missed.

Aortic dissection is often the result of aortic dilatation but does not need to be. Nonetheless, detection of dilatation of any region of the thoracic aorta should lead to initiation of regular monitoring, medication, and referral to cardiothoracic surgery to prevent the occurrence of dissection. Few areas of cardiovascular medicine have enjoyed such an explosion of new understanding over the recent past as have diseases of the aorta. Mutations in more than a dozen genes are now known to predispose to thoracic aortic disease, even in people without any outward manifestations of a syndrome. This latter category, familial thoracic aortic aneurysm, is proving to be relatively common and necessitates a careful family history involving three generations in any person detected with disease. Equally important has been the evolution of surgical techniques, especially various approaches to resuspending the native aortic valve inside a conduit, thereby rendering it competent and sparing the patient an artificial valve. As one success story, the life expectancy of people with Marfan syndrome has increased by approximately 30 years over the past three decades.[1] New approaches to medical therapy, exemplified by the ongoing trial of angiotensin receptor blockade versus beta-adrenergic blockade in Marfan syndrome, hold promise for greatly reducing the risk of dissection in some conditions.[2]

How is the busy clinician, especially in primary care and emergency medicine, expected to keep up with the rapid evolution of important knowledge in this group of diseases? Among the options are literature searches, textbooks, and review articles. But these require time, which is limited in the heat of battle, or become outdated. A good solution is a set of clinical practice guidelines, which are generally concise, have been constructed by recognized experts, and have been vetted by professional societies. Increasingly, guidelines are available electronically and can be searched by key words or topics, even on handheld devices. The 2010 Guidelines for the Diagnosis and Management of Patients with Thoracic Aortic Disease represent such a resource.[3] Contained therein are 26 sets of guidelines, each containing multiple recommendations accompanied by references and the level of supportive evidence. None has resulted from multiple randomized clinical trials (level of evidence A), and most are level C (consensus expert opinion). Thus, it is indeed fortunate that the authors and reviewers constituted an outstanding and eclectic group of experienced clinicians.

Based on my own clinical experience, there are several crucial points, emphasized by these guidelines, which need to enter the medical mainstream.

• Congenital bicuspid aortic valve is frequently associated with dilatation of the ascending aorta and this may also involved a primary aortopathy; the aortic dilatation above the sinotubular junction is not simply due to the hemodynamics of a regurgitant or stenotic valve.
• Women with the Turner syndrome need lifelong monitoring for ascending aortic dilatation.[4]
• People with Marfan syndrome and other conditions that cause dilatation primarily in the sinuses of Valsalva can undergo implantation of a conduit that spares the native aortic valve, greatly reduces the risk of dissection, and obviates the need for anticoagulation.
• Anyone presenting with noninflammatory causes of thoracic aortic disease under the age of 50 years old needs careful scrutiny for an underlying cause and a detailed family history; in most instances, close relatives (children, siblings, parents) should undergo screening by imaging or, if a genetic mutation can be defined in the patient (proband), by testing the relatives' DNA.
• Young people with thoracic aortic disease require lifelong imaging; even though computed tomography angiography may offer some advantages in quality, the considerable radiation exposure should give pause and lead to consideration of magnetic resonance imaging.

It will be important to update these guidelines on a regular basis. Already, recent publications report results that will call into question some of the recommendations.[5] Similarly, additional disorders not covered by the guidelines clearly predispose to thoracic aortic disease (e.g., hereditary hemorrhagic telangiectasia, Fabry disease, tetralogy of Fallot). One national resource that is beginning to provide answers to important questions unaddressed or poorly supported by these guidelines is the Registry of Genetically Transmitted Thoracic Aortic Aneurysms and Cardiovascular Diseases.[6]

The level of progress made in this group of diseases is truly outstanding, and perhaps best exemplified by a quote from Osler's Principles and Practice of Medicine, 1903 edition: "Aneurism (sic) of any part of the thoracic aorta is a very hopeless disease." Furthermore, one of the most common causes of thoracic aortic aneurysm in Osler's day, syphilis, is not mentioned in the executive summary of the new guidelines.