(234KB)Fleck T, Czerny M, Wolner E, Grabenwoger M. Interventional
treatment methods in patients with Marfan Syndrome. Images Paediatr Cardiol
2004;19:1-11
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(234KB) |
Fleck T, Czerny M, Wolner E, Grabenwoger M. Interventional
treatment methods in patients with Marfan Syndrome. Images Paediatr Cardiol
2004;19:1-11
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Dept Cardiothoracic Surgery, University of Vienna Medical School, 1090 Vienna, Austria |
The leading cause of premature death in these patients is progressive dilatation and subsequent dissection of the ascending thoracic aorta resulting in cardiac tamponade, and left ventricular failure due to aortic regurgitation. Life expectancy is primarily determined by the severity of cardiovascular involvement, and has improved substantially over the last 20 years due to the advances in surgical and medical management.
The optimum management of Marfan patients includes a lifelong surveillance
with particular emphasis placed on aortic behaviour. Preventive replacement
of various portions of the aorta has been a major contribution for improved
life expectancy in these patients. The different surgical and interventional
treatment options currently available will be further outlined in this
review.
MeSH
| Marfan syndrome | Surgical techniques | Thoracic Surgery |
| Long term outcome | Cardiovascular complications |
During the 20th century, additional components of this syndrome became apparent, particularly the cardiovascular involvement with dilatation of the aortic root and the high risk of subsequent aortic dissection which was first reported in 1943.1 Diagnosis mainly relied on clinical criteria, until recently when the underlying gene defect on chromosome 15q21 was discovered in 1990.²
Cardiothoracic surgery, has become an accepted and proven treatment for elective as well as emergency surgery for aortic aneurysm and dissection, and thereby can be considered as the major contributing factor for the increased life expectancy in patients with Marfan syndrome (MFS).
Pathophysiolgy and genetics
By immunhistochemical studies of Marfan patients it was shown, that
most of the patients with MFS display an abnormal pattern of microfibrils
in the extracellular matrix. Further studies revealed a 350 kD protein
named Fibrillin which was characterised to be the main component of the
extracellular microfibrils, to be responsible for these abnormalities.³
Subsequently the fibrillin gene could be mapped to the long arm of chromosome
15 and in situ hybridisation assigned the gene locus to 15q15-21.²
However, genetic testing proved to be less reliable than expected, with
only 66% mutation detection rate of patients diagnosed with MFS by the
Ghent nosology. The reason for these fair results are based on the fact
that there are a variable number of mutations, which precludes broad spectrum
genetic screening. Furthermore Fibrillin mutations have also been detected
in Marfan related disorders.³
Diagnosis
In 1986 the Berlin nosology of heritable connective tissue disorder
was published which classified certain organ manifestations into groups
with major and minor criteria.4 Further refinements were
included in the Gent criteria and recently revised by De Paepe et al in
1996.5 The criteria are subdivided into the following
organ systems: skeletal, ocular, cardiovascular, pulmonary, skin, dura
and family respectively genetic history. For a clinical diagnosis of MS,
in the absence of a positive family history, a person suspected to have
MS should at least display major criteria in two organ systems and involvement
of a third organ system. When patients have a positive family history,
major criteria in one and minor criteria in another organ system is required.5
Particular emphasis should be placed on the predominance of skeletal features in childhood, as this can lead to earlier diagnosis and more appropriate surveillance, of cardiovascular status. In younger patients with a family history of MFS who do no fulfil the diagnostic criteria as well as young patients who fail to meet criteria in one organ system are required to repeat evaluations on a regular basis until the age of 18.
Cardiovascular complications usually do not occur before the age of 16 years. A this point the aortic root dimensions approached the adult size so that one can refer to the recommendations for the adult population regarding aortic root dimensions which should be always measured in relation to body surface area.6
Infrequently, the infantile form of Marfan syndrome occurs, which is characterised by mitral valve regurgitation and aortic root dilatation which become apparent during the first three months of life. Mortality is substantial with 14% of affected children dying during the first year of life.7
Conservative and surgical considerations
Cardiovascular manifestations in MFS include mitral valve prolapse
and regurgitation, left ventricular dilatation, pulmonary artery dilatation,
and aortic valve regurgitation secondary to aortic root dilatation which
can be regarded the most common cause of morbidity through the increased
risk of dissection and rupture when the aortic root diameter exceeds 5.5
cm. Obviously the outcome of prophylactic aortic root surgery is superior
over emergency surgery in the case of aortic dissection.
Dissection involving the ascending aorta is an absolute indication for operation with the intention to replace the sinus of Valsalva and the ascending aorta and eventually, if affected, the aortic arch (figures 1-3). Treatment options regarding the aortic valve are outlined below.
The exact timing of operation is crucial in a Marfan patient. The following parameters should be taken into consideration when planning surgery:
Surgical techniques
A recent survey of 10 major Marfan surgical centres reported an overall
operative mortality rate of 1.5% in patients undergoing elective root replacement.
However, differences became apparent when emergency procedures were performed
for acute dissection which resulted in an eight fold increased mortality
rate (11.6%) in contrast to elective surgery.8
Ascending thoracic aorta
In 1968 the composite graft technique with replacement of the aortic
valve, the sinus of Valsalva and the ascending aorta was introduced by
Bentall and de Bono.9 Briefly, this technique
consists of a composite graft consist of a mechanical valve inserted into
a gelatine impregnated Dacron graft that comes preassembled. The coronary
arteries are reimplanted as buttons on to the graft. However, in
order to avoid life long anticoagulation, subsequent efforts were directed
towards preserving the aortic valve and thereby obviating the need for
continuous anticoagulation. Valve sparing aortic root replacements were
subsequently introduced by Yacoub as remodelling techniques in 1979 and
by David with the reimplantation procedure in 1988.10,11
Preservation of the aortic valve has many advantages namely preservation
of the dynamic structure of the outflow tract which influences left ventricular
function, coronary flow and cardiac output.12 A recent
study by de Oliviera and colleagues compared aortic valve reimplantation
versus remodelling of the aortic root technique; the reimplantation group
emerged as more appropriate for prevention of further root dilatation.13
Even though some concern had been raised concerning the durability
of this procedure as the aortic leaflets are involved in fibrillin deficiency,
long term results have been encouraging (figures 4,5).13
Furthermore as most patients with MFS necessitate subsequent vascular or orthopaedic interventions, the avoidance of anticoagulation results in a diminished risk of bleeding complications.
Descending thoracic aorta
The risk of additional aneurysm formation after intervention on the
ascending aorta is around 50%. The majority of patients need further surgery
in the remaining aorta followed by the iliac and subclavian artery. In
a previous study by Finkbohner and colleagues, it was determined that the
presence of aortic dissection, hypertension and history of smoking are
risk factors for the development of secondary aneurysms. Moreover, patients
with a dissection at the time of first surgery were more likely to require
subsequent surgery on the remaining aorta as outlined in the current study.
The ascending thoracic aorta was the site of first operation in 84% of
their patients, followed by the descending thoracic aorta and the abdominal
aorta. Median age at the time of first operation was 32 years.14
A recent publication by Coselli et al reported a favourable experience of replacement of the ascending thoracic aorta with contemporary techniques in 50 Marfan patients with an overall complication rate of 5% and 96% 30 day survival.15
Endovascular stent grafting (ESG) of the descending aorta emerged as promising less invasive alternative for conventional open surgical repair.16 Particularly in patients with MFS conservative treatment as usually advocated in an uncomplicated acute aortic dissection type B seems less reliable because of the fragility of the aortic wall. Therefore more aggressive treatment methods are warranted. With the implementation of ESG it became feasible to treat those patients, who would otherwise have to undergo emergency surgery with an increased risk of complications. Moreover the presence of ESG does not preclude further surgery on the aorta, as the can be easily removed.
However, long term results for ESG are still limited. In our series
of 80 patients treated with ESG for thoracic aortic disease 4 (5%) needed
further open surgical repair. Particularly, we do not recommend ESG for
descending aortic aneurysm in MFS as through the decreased elasticity of
the aortic wall, the radial forces generated by the expanded stent graft
may result in endoleak formation or potential rupture. Longer follow up
is definitely needed to predict more accurately the long term durability
of these devices (figure 6).
Open repair of the thoracoabdominal aorta with Left heart bypass
and selective visceral perfusion
Aneurysms of the thoracoabdominal aorta (TAAA) are mainly the long
term result of a chronic dissected aorta (figures 7,8).
Extended repair of a TAAA was associated with high mortality and complication rates until Coselli developed a technique with the aid of left heart bypass, sequential clamping and selective visceral perfusion to obviate the need for cardiopulmonary bypass and the associated bleeding problems and on the other hand improve end organ perfusion, especially of the spinal cord in order to reduce the incidence of postoperative paraplegia.15
Conclusions
The primary life threatening complication in MFS patients is rupture
of an aortic aneurysm. In the era before cardiac surgery over 90% of patients
died from aneurysm rupture. Through refinements, particular in cardiovascular
surgery, life expectancy has substantially increased during the last 20
years. Whereas in 1972 the median life expectancy was 32 years, these numbers
rose to 45 years in 1998.17 This was mainly accomplished
through elective replacement of the aortic root which prolonged survival
in MFS patients as reported previously.17 The presence
of dissection and hypertension emerged to be a significant predictor of
subsequent aneurysm operation. It has to be stressed that prophylactic
surgery does not decrease the risk of sudden death from aneurysm rupture
but decreases the risk of subsequent vascular complications. The presence
of dissection is considered a risk factor for future vascular complications
most probably through the underlying severe pathology.
A typical pattern of aneurysm formation has been observed, with the ascending thoracic aorta being the first vascular event followed by the descending thoracic aorta. Notably, peripheral vascular arteries are usually not affected. As more than 50% of Marfan patients require subsequent surgery on their vascular system, recurrent evaluation of the entire aorta by computed tomography or magnetic resonance imaging is crucial to the clinical follow up, before and after aortic root surgery.
References
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