Aortic root complications in Marfan's syndrome: identification of a lower risk group

Mechanisms of aortic valve incompetence: finite-element modeling of Marfan syndrome

OBJECTIVES

Progressive aortic root dilatation and an increased aortic root elastic modulus have been documented in persons with Marfan syndrome. To examine the effect of aortic root dilatation and increased elastic modulus on leaflet stress, strain, and coaptation, we used a finite-element model.

METHODS

The normal model incorporated the geometry, tissue thickness, and anisotropic elastic moduli of normal human roots and valves. Four Marfan models were evaluated, in which the diameter of the aortic root was dilated by 5%, 15%, 30%, and 50%. Aortic root elastic modulus in the 4 Marfan models was doubled. Under diastolic pressure, regional stresses and strains were evaluated, and the percentage of leaflet coaptation was calculated.

RESULTS

Root dilatation and stiffening significantly increased regional leaflet stress and strain compared with normal levels. Stress increases ranged from 80% to 360% and strain increases ranged from 60% to 200% in the 50% dilated Marfan model. Leaflet stresses and strains were disproportionately high at the attachment edge and coaptation area. Leaflet coaptation was decreased by approximately 20% in the 50% root dilatation model.

CONCLUSIONS

Increasing root dilatation and root elastic modulus to simulate Marfan syndrome significantly increases leaflet stress and strain and reduces coaptation in an otherwise normal aortic valve. These alterations may influence the decision to use valve-sparing aortic root replacement procedures in patients with Marfan syndrome.

Natural history of cardiovascular manifestations in Marfan syndrome

AIMS

To investigate the natural history of mitral valve and aortic abnormalities in patients with Marfan syndrome during childhood and adolescence.

METHODS

Fifty two patients with Marfan syndrome were followed for a mean of 7.9 years. Occurrence of adverse cardiovascular outcomes was measured clinically and by ultrasound examination.

RESULTS

Mitral valve prolapse (MVP) was diagnosed in 46 patients at a mean age of 9.7 years, more than 80% of whom presented as "silent MVP". Mitral regurgitation (MR) occurred in 25 patients, aortic dilatation in 43, and aortic regurgitation (AR) in 13. Both MVP and aortic dilatation developed at a constant rate during the age period 5-20 years. In 23 patients MVP was diagnosed before aortic dilatation, in 18 the reverse occurred, and in 11 patients the two abnormalities were diagnosed simultaneously. During follow up, 21 patients showed progression of mitral valve dysfunction; progression of aortic abnormalities occurred in 13. Aortic surgery was performed in 10; two died of subsequent complications. Mitral valve surgery was performed in six. In sporadic female Marfan patients the age at initial diagnosis of MVP, MR, aortic dilatation, and AR was lowest, the grade of MR and AR most severe, the time lapse between the occurrence of MVP and subsequent MR as well as between dilatation and subsequent AR shortest, and the risk for cardiovascular associated morbidity and mortality highest.

CONCLUSIONS

During childhood and adolescence in Marfan syndrome, mitral valve dysfunction as well as aortic abnormalities develop and progress gradually, often without symptoms, but may cause considerable morbidity and mortality by the end of the second decade, especially in female sporadic patients.

Surgically treated aortic root aneurysm following aortic valve replacement

A 65-year-old man with aortic regurgitation underwent aortic valve replacement with a St. Jude Medical prosthetic valve about 6 years ago. At that time, the aortic root was slightly dilated at about 40 mm in diameter and the ascending aorta was within the normal range. This year, the man was diagnosed with an aortic root aneurysm in regular follow-up echocardiography. Chest-enhanced computed tomography and chest aortography at our hospital demonstrated a pear-like aortic root aneurysm about 60 mm in diameter. Elective operation for the aortic root aneurysm was conducted September 29, 1999, based on the Bentall procedure. Composite graft replacement with coronary reconstruction was conducted using a 28-mm Hemashield prosthetic graft and a 23-mm St. Jude Medical prosthetic valve under cardiopulmonary bypass. An 8-mm Hemashield graft was interposed on the left main coronary artery and the right coronary artery was directly anastomosed using a Carrel patch method. The postoperative course was uneventful and post-operative examination demonstrated good surgical results. Histological findings of the aortic aneurysm wall showed cystic medial necrosis. Surgical cases of aortic root aneurysm after aortic valve replacement are rare, but serious complications with the possibility of rupture or dissection warrant surgical intervention.

The Marfan syndrome

The Marfan syndrome (MFS), initially described just over 100 years ago, was among the first conditions classified as a heritable disorder of connective tissue. MFS lies at one end of a phenotypic continuum, with people in the general population who have one or another of the features of MFS at the other end, and those with a variety of other conditions in between. Diagnosis of MFS and these other conditions remains based on clinical features. Mutations in FBN1, the gene that encodes fibrillin-1, are responsible for MFS and (in a few patients) other disorders in the continuum. In addition to skeletal, ocular, and cardiovascular features, patients with MFS have involvement of the skin, integument, lungs, and muscle tissue. Over the past 30 years, evolution of aggressive medical and surgical management of the cardiovascular problems, especially mitral valve prolapse, aortic dilatation, and aortic dissection, has resulted in considerable improvement in life expectancy.

Aortic root asymmetry in marfan patients; evaluation by magnetic resonance imaging and comparison with standard echocardiography

BACKGROUND

Patients with Marfan syndrome may develop aortic root dissection despite only mild aortic root dilation as shown by standard echocardiography, which may be due to aortic root asymmetry. Purpose of the present study was to investigate aortic root asymmetry by magnetic resonance (MR) imaging in patients with Marfan syndrome and to compare these measurements with standardly performed echocardiography.

METHODS

Eighty-seven Marfan patients (mean age 31 +/- 8 years) underwent MR imaging. From this population, 15 patients (mean age 29 +/- 3 years) were selected in whom both echocardiography and MR imaging had been performed within 3 months. With echocardiography, the aortic root was measured according to the recommendations of the American Society of Echocardiography. With MR imaging, a short axis view of the aortic root was obtained to measure distances between the noncoronary, right coronary and left coronary cusps and the aortic root area. Correlations between aortic root area and diameters were assessed, and 95% confidence intervals (95% CIs) calculated.

RESULTS

No difference in the standardly measured noncoronary to right coronary cusp diameter between MR imaging and echocardiography was shown (42 +/- 6 mm). Largest aortic root diameter on the MR images was the right to left coronary cusp diameter (46 +/- 7 mm, p < 0.02). For a given noncoronary to right coronary cusp diameter, 95% confidence intervals revealed a variation of -20 to +20% in the aortic root area.

CONCLUSIONS

The majority of Marfan patients show asymmetric dilation of the aortic root by MR imaging. This phenomenon may go unnoticed when standard echocardiography is performed. The asymmetry of the aortic root might be of clinical importance in unexpected aortic root dissection.

Etiologic factors of acute aortic dissection in children and young adults

Current concepts in the pathophysiology and predisposing conditions of acute aortic dissection in children, adolescents, and young adults are presented. Timely diagnosis is required for this life-threatening condition. Most children and adolescents with aortic dissection have congenital cardiovascular anomalies. Certain heritable disorders involving connective tissue also predispose to this disorder. Newer associations include cocaine abuse and weight lifting. To facilitate early diagnosis, the salient physical findings of the known predisposing conditions are reviewed. Clinical presentation and diagnostic imaging of aortic dissection are briefly summarized. Physicians working in an acute care setting, particularly in the emergency room, should be aware of disorders predisposing to acute aortic dissection in the pediatric and young adult population. Practitioners conducting school or college preparticipation sports evaluations can make use of such information in their assessment of risk for sudden death.

Survival and complication free survival in Marfan's syndrome: implications of current guidelines

OBJECTIVE

To evaluate survival and complication free survival in patients with Marfan's syndrome and to assess the possible influence of recently revised guidelines for prophylactic aortic root replacement in these patients.

METHODS

130 patients who had been attending one institution over 14 years were evaluated. Kaplan-Meier analysis was performed in 125 patients who did not present with aortic root dissection as the first sign of Marfan's syndrome, with the end points: death, aortic root dissection, and prophylactic aortic root replacement after diagnosis. In the patients developing aortic root dissection, current guidelines for prophylactic aortic root replacement were retrospectively applied to investigate the number of dissections that could theoretically have been prevented. The guidelines were: (1) aortic root diameter >/= 55 mm, (2) positive family history of aortic dissections and aortic root diameter >/= 50 mm, and (3) aortic root growth >/= 2 mm/year. Outcomes following emergency surgery (15 patients) and prophylactic surgery of the aortic root (30 patients) were compared.

RESULTS

Five and 10 year survival after diagnosis was 95% and 88%, and the five and 10 year complication free survival was 78% and 66%, respectively. Thirteen patients developed dissection, 30 underwent prophylactic repair, and 82 had an uncomplicated course. Eleven dissections could theoretically have been prevented by application of the current guidelines. Five year survival following emergency and prophylactic repair of the aortic root was 51%, and 97%, respectively.

CONCLUSIONS

Survival in the Marfan's syndrome in the past 14 years seems satisfactory; with application of current guidelines, it has probably even improved. However, because of the high fatality rate in Marfan patients developing aortic root dissection, more extensive screening for Marfan's syndrome and a search for additional risk factors are desirable.

Importance of dural ectasia in phenotypic assessment of Marfan's syndrome

BACKGROUND

Early identification of Marfan's syndrome is fundamental in the prevention of aortic dilatation, but the wide phenotypic expression of the disorder makes the clinical diagnosis very difficult. Dural ectasia has been classified as a major diagnostic criterion; however, its prevalence is not known. We aimed to identify the true prevalence of dural ectasia in Marfan's syndrome, and to investigate its relation to aortic pathology.

METHODS

A magnetic-resonance-imaging (MRI) study of the thoracic aorta and of the lumbosacral spine was done in an inclusive series of 83 patients with Marfan's syndrome to assess the presence and degree of dural ectasia and aortic involvement; 12 patients were younger than 18 years. 100 individuals who underwent MRI of the lumbar spine for routine clinical indications represented the control group; none of them had any potential causes for dural ectasia.

FINDINGS

Dural ectasia was identified in 76 (92%) patients and none of the control group. The severity of dural ectasia was related to age; the mean (SD) age of patients with mild dural ectasia was 26 years (14) whereas that of those with severe disease (meningocele) was 36 years (9) (p=0.038). 11 of 12 patients younger than 18 years had dural ectasia. No association was found between aortic dilatation and dural ectasia.

INTERPRETATION

Dural ectasia is a highly characteristic sign of Marfan's syndrome, even at an early age.

Surgical treatment of the dilated ascending aorta: when and how?

BACKGROUND

The aorta is considered pathologically dilated if the diameters of the ascending aorta and the aortic root exceed the norms for a given age and body size. A 50% increase over the normal diameter is considered aneurysmal dilatation. Such dilatation of the ascending aorta frequently leads to significant aortic valvular insufficiency, even in the presence of an otherwise normal valve. The dilated or aneurysmal ascending aorta is at risk for spontaneous rupture or dissection. The magnitude of this risk is closely related to the size of the aorta and the underlying pathology of the aortic wall. The occurrence of rupture or dissection adversely alters natural history and survival even after successful emergency surgical treatment.

METHODS

In recommending elective surgery for the dilated ascending aorta, the patient's age, the relative size of the aorta, the structure and function of the aortic valve, and the pathology of the aortic wall have to be considered. The indications for replacement of the ascending aorta in patients with Marfan's syndrome, acute dissection, intramural hematoma, and endocarditis with annular destruction are supported by solid clinical information. Surgical guidelines for intervening in degenerative dilatation of the ascending aorta, however, especially when its discovery is incidental to other cardiac operations, remain mostly empiric because of lack of natural history studies. The association of a bicuspid aortic valve with ascending aortic dilatation requires special attention.

RESULTS

There are a number of current techniques for surgical restoration of the functional and anatomical integrity of the aortic root. The choice of procedure is influenced by careful consideration of multiple factors, such as the patient's age and anticipated survival time; underlying aortic pathology; anatomical considerations related to the aortic valve leaflets, annulus, sinuses, and the sino-tubular ridge; the condition of the distal aorta; the likelihood of future distal operation; the risk of anticoagulation; and, of course, the surgeon's experience with the technique. Currently, elective root replacement with an appropriately chosen technique should not carry an operative risk much higher than that of routine aortic valve replacement. Composite replacement of the aortic valve and the ascending aorta, as originally described by Bentall, DeBono and Edwards (classic Bentall), or modified by Kouchoukos (button Bentall), remains the most versatile and widely applied method. Since 1989, the button modification of the Bentall procedure has been used in 250 patients at Mount Sinai Medical Center, with a hospital mortality of 4% and excellent long-term survival. In this group, age was the only predictor of operative risk (age > 60 years, mortality 7.3% [9/124] compared with age < 60, mortality 0.8% [1/126], p = 0.02).

CONCLUSIONS

This modification of the Bentall procedure has set a standard for evaluating the more recently introduced methods of aortic root repair.

Marfan syndrome in children and adolescents: predictive and prognostic value of aortic root growth for screening for aortic complications

OBJECTIVE

To assess and measure the diagnostic and prognostic value of individual aortic root growth in children and adolescents with Marfan syndrome.

DESIGN

From 1983 to 1996, 250 children were screened for Marfan syndrome. Serial echocardiographic aortic root measurements of 123 children (57 Marfan, 66 control) were available for evaluation of aortic root growth. Aortic root diameters were correlated with body surface area. Based on individual growth of the aortic root a discrimination formula was derived to distinguish Marfan patients from control subjects.

RESULTS

Sensitivity and specificity of this method, which were dependent on the number of measurements, were 84% and 73%, respectively, for three serial measurements. The discrimination score also predicted a five year complication free survival in all patients.

CONCLUSIONS

In children and adolescents with Marfan syndrome, aortic root growth differs significantly from subjects in whom Marfan syndrome was definitely ruled out during screening. Measurement of individual aortic root growth may serve to establish diagnosis at an early stage and is of prognostic value for occurrence of aortic complications.

Marfan syndrome in children and adolescents: an adjusted nomogram for screening aortic root dilatation

OBJECTIVE

To construct an adjusted nomogram for the echocardiographic screening of aortic root diameter in children with possible Marfan disease.

DESIGN

In 91 children (42 boys, 49 girls, age range 3.2 to 18.4 years) undergoing Marfan screening from 1983 until 1996, the diagnosis Marfan syndrome and any other aortic pathology was definitely ruled out. These served as a control population to set appropriate reference standards.

RESULTS

Compared with a standard Dutch reference population, body surface area of the control subjects (mean (SD)) was above the 50th centile (boys 0.09 (0.20) m2, range -0.28 to 0.69 m2; girls 0.09 (0.17) m2, range -0.17 to 0.69 m2). Echocardiographically determined aortic root diameter and body surface area showed a linear relation and a greater variability of aortic root diameter in these relatively tall subjects (n = 91, R2 = 0.62) than in the standard nomogram (n = 56, R2 = 0.93). In 24% of cases (n = 22), the aortic root exceeded the upper limit of normal in the standard nomogram, by 2.2 (2.0) mm. An adjusted nomogram was constructed with a higher upper limit.

CONCLUSIONS

A Marfan screening population differs from the unselected population in body surface area and aortic root size variability. An adjusted nomogram should therefore be used to detect a truly enlarged aortic root.