Aortic Disease In Marfan Syndrome

Dilatation of the root and ascending aorta affects the majority of adult patients with Marfan syndrome. Aortic root dilatation is noted in 50% of children and as many as 60-80% of adults with Marfan syndrome33. Involvement of

Table 13.1. Dilatation or dissection of the descending thoracic or abdominal aorta below the age of 50

System

Major criteria

Minor criteria

Skeletal system Presence of at least four of the following manifestations:

* Pectus carinatum

* Pectus excavatum requiring surgery

* Reduced upper to lower segment ratio or arm span to height ratio greater than 1.05

* Wrist and thumb signs

* Scoliosis >20d or spondylolis-thesis

Reduced extensions at the elbows (<170d)

Medial displacement of the medial malleolus causing pes planus

Protrusio acetabulae of any degree (ascertained on radiographs)

* Pectus excavatum of moderate severity

* Joint hypermobility

* Highly arched palate with crowding of teeth

* Facial appearance (dolicho-cephaly, malar hypoplasia, enophthalmos, retrognathia, down-slating palpebral fissures)

Ocular system

Cardiovascular system

* Ectopia lentis (dislocated lens)

* Dilatation of the ascending aorta with or without aortic regurgitation and involving at least the sinuses of Valsalva, or

* Dissection of the ascending aorta

* Abnormally flat cornea (as measured by keratometry)

* Increased axial length of globe (as measured by ultrasound)

* Mitral valve prolapse with or without mitral valve regurgitation

* Dilatation of the main pulmonary artery, in the absence of valvular or peripheral pulmonic stenosis or any other obvious cause, below the age of 40

* Calcification of the mitral an-nulus below the age of 40

* Dilatation or dissection of the descending thoracic or abdominal aorta below the age of 50

Pulmonary system

None

* Spontaneous pneumothorax

* Apical blebs (ascertained by chest radiography)

Table 13.1. (Continued)

System

Major criteria

Minor criteria

Skin and integu- None ment

* Stretch marks not associated with marked weight changes, pregnancy, or repetitive stress

* Recurrent incisional hernias

Dura

* Lumbosacral dural ectasia by None

CT or MRI

Family/genetic history

* Having a parent, child, or sib- None ling who meets these diagnos-

tic criteria independently

* Presence of a mutation in FBN1 known to cause the Mar-fan syndrome

* Presence of a haplotype around FBN1, inherited by descent, known to be associated with unequivocally diagnosed Mar-fan syndrome in the family other aortic segments is less common. Typically, the sinuses are effaced. Aortic regurgitation develops as a function of either the enlarging root/annulus diameter or associated prolapse of the thinned and stretched valve leaflets. An-nuloaortic ectasia is an older patho-anatomic term used to describe dilatation confined to the root and sinuses, most often with aortic valve regurgitation. The rate of continued aneurysmal growth in any individual patient is difficult to predict, but application of the LaPlace principle is appropriate. Despite its dilation, the aorta is actually stiffer and less compliant than normal, a characteristic that increases further with age34. Central pulse pressure, as can be estimated from the carotid pulse pressure, is a major determinant of ascending aortic diameter change35.

Although the risk of spontaneous dissection generally increases with increasing aortic diameter, the process can and does occur unpredictably at any aortic size. Pregnancy confers an even higher risk, as does a family history of dissection or rupture36. In an unselected adult Marfan patient population reported by Hirata and colleagues, the aortic root and annular dimensions were significantly larger (4.1 ± 0.8 cm vs. 3.2 ± 0.3 cm, p < 0.01 and 2.9 ± 0.4 cm vs. 2.3 ± 0.3 cm, p < 0.01) than normal controls37. In another series of 113 patients with Marfan syndrome followed over four years, 80% had dilatation

Source: From reference 18.

of the aortic root38. The dilatation was localized to the sinuses in 28% of patients and extended beyond the sinotubular ridge in 51% of patients. Aortic complications occurred in 0 of 23 patients with normal (initial) size, in 6% (2 of 32) of patients with localized dilatation, and in 33% (19 of 58) of patients with generalized dilatation of the root. The extent of aortic root dilatation was the only independent predictor of subsequent aortic complications, including dissection.

The overall prevalence of Marfan syndrome among patients entered prospectively in the International Registry of Aortic Dissection (IRAD) registry was low (~5%)39. Patients with Marfan syndrome, compared with those without Marfan syndrome, were younger and had a higher prevalence of previously known aortic pathology (aneurysm/dissection) or prior aortic or aortic valve surgery. Symptoms associated with the dissection process were similar between the two groups, although it is recognized that Marfan syndrome patients may sometimes present with atypical features. In the IRAD registry, Marfan patients presented far more often with type A than type B dissection and had larger aortic diameters with a higher prevalence of aortic regurgitation but a lower prevalence or intramural hematoma formation. The hospital mortality rate among patients with Marfan syndrome was comparable to the rate among non-Marfan patients, in the range of 20-25%. Thrombosis of the false lumen occurs less commonly among patients with Marfan syndrome, even after successful surgical repair40. These patients are at higher risk for redissection and false lumen aneurysm formation, for which repeat surgery or endovascular grafting is frequently necessary.

A heightened clinical index of suspicion for aortic dissection is appropriate when evaluating patients with Marfan syndrome who report chest or back discomfort. The principles of diagnosis and management of acute aortic dissection are otherwise generally the same for patients with and without Mar-fan syndrome, including the rapid performance of noninvasive imaging, the indications for surgery, and the use of stabilizing pharmacologic agents to reduce heart rate, blood pressure, and its rate of rise (dP/dT). Whereas uncomplicated acute type B dissection in patients without Marfan syndrome is usually managed conservatively, some authorities have argued for primary surgical or endovascular stent graft repair in acute type B patients with Marfan syndrome41.

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