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Key Concepts

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  • Thoracic aortic aneurysm syndromes are due to genetic disorders inherited as autosomal dominant traits with reduced penetrance and incomplete expression. Hence, clinical phenotype is complex and highly variable with often no genotype-phenotype correlation.

  • Altered TGF-β signaling and proteolytic metabolism involving the entire aortic wall are now challenging old pathophysiologic models by which aortic aneurysms were solely caused by extracellular matrix structural protein deficiency in the media.

  • Indications for surgery are still mainly based on aortic diameter as well as aortic growth rate and family history of early rupture/dissection. However, efforts are made to identify circulating markers associated with early complications to guide risk stratification.

  • Surgery is the only treatment that can modify the natural history of pediatric patients with thoracic aortic aneurysm syndromes. Although promising, medical treatment has not yet been validated.

  • Aortic valve-sparing root replacement (AVSRR) is currently the favored surgical approach, whereas the Bentall operation should be reserved for patients with acute aortic dissection, unrepairable leaflet damage, or failed AVSRR. Early and midterm results of AVSRR in pediatric patients are excellent and comparable to those obtained with composite valve graft root replacement. Long-term event-free survival in this particular group of patients has yet to be assessed.

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Introduction

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Arterial aneurysms in children are typically due to a genetic abnormality and represent the most lethal clinical feature observed in the setting of connective tissue disorders. The most prevalent sites of vascular catastrophe in these young patients are the aortic root and the ascending aorta.

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Pediatric aortic surgery for patients affected by connective tissue disorders is a rapidly evolving field. As a better understanding of the underlying aortic wall pathology is achieved, diagnosis is improved and treatment objectives, surgical indications, operative strategies, and expected outcomes change.

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Although over the past 20 years treatment goals have shifted from life-saving measures to preemptive surgery in the hopes of achieving long-term event-free survival, risk stratification and surgical decision-making are still imperfect. Surgical indications are mostly based on clinical diagnosis, aneurysm size, and family history. The absence of biomarkers predictive of malignant clinical course, along with the lack of a large body of data on natural history and true long-term treatment outcomes impact our ability to predict the aortic size at which vascular complications may occur in each patient. Aortic root pathology and aneurysms are described in detail in Chapter 39. We will hereby expand on the topic by focusing on patients in the pediatric age group.

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Pathophysiology

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Thoracic aortic aneurysm in the setting of connective tissue disorder is a syndromic disease with multiple, complex phenotypes. Within each disease, clinical heterogeneity due to mosaicism, incomplete penetrance, and age-dependence of the phenotype is common. These features account for the lack of a complete understanding of the pathophysiology underlying thoracic aneurysm syndromes.

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Historically, pathogenetic models of ascending aortic aneurysm were centered on abnormalities of ...

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