Sinus of Valsalva Aneurysms

Introduction

Since its first description in 1840 by Thurman, varying terminologies and classifications have been used to describe the sinus of Valsalva aneurysm (SV aneurysm). Because this lesion lies on a spectrum of other aortic root pathologies, it is important that precise terminology is carefully defined before there can be a meaningful discussion regarding etiology, management, and outcome.

In 1962, Sakakibara and Konno proposed a nomenclature of four types of aneurysm, but this classification did not describe the variation in the site of penetration when these aneurysms rupture. The classic congenital SV aneurysm is defined as the dilation or enlargement of one of the aortic sinuses between the aortic valve annulus and the sinotubular ridge. Multiple sinus dilation is usually considered as a separate entity, namely, as aneurysmal dilation of the aortic root. By definition, the true SV aneurysm arises from above the aortic annulus, in contrast to the prolapsing aortic cusp, which is seen below the annulus ( Fig. 38.1 ). Both of these lesions are known to be associated with the presence of a ventricular septal defect, which may complicate the initial diagnostic workup.

Abbott first suggested the congenital nature of an SV aneurysm in 1919. Edwards and Burchell later described the histologic features, with separation of the media in the sinus from the media adjacent to the aortic annulus. This congenital absence of the elastic lamellae was thought to give rise to focal weakness in the aortic wall, particularly when subjected to increased aortic pressures. This structural deficiency is the precursor of the clinical sequelae of progressive aneurysmal dilation and, finally, rupture.

An acquired lesion very similar to that seen in primary congenital SV aneurysms can be seen in a variety of conditions such as syphilis, tuberculosis, infective endocarditis, trauma, and a group of connective tissue disorders. This includes an association with HLA 27 ankylosing spondylitis. These acquired lesions are often classified as aneurysms of the aortic root to avoid confusion with the congenital SV.

A simplified pictorial representation of the lesions affecting the left ventricular outflow tract and aortic root is shown in Fig. 38.1 .

Recently, a four-level hierarchy of nomenclature has been proposed to encompass SV aneurysms, aortic root aneurysms, and aortic dissections. This nomenclature attempts to supersede the classic aneurysmal descriptions of morphology (fusiform or saccular), histology (true, dissected, or false), and anatomy (root, arch, sinuses) ( Table 38.1 ). Hierarchy 1 describes the aortic aneurysm type. If there are multiple areas of dilation, then the aneurysm is referred to as an “aneurysm of the aortic root.” Hierarchy level 2 describes the location and anatomy of the lesion, for example, the sinus of origin. Level 3 describes the acuity or current clinical status (ruptured or unruptured), and level 4 describes the pathology and chamber of penetration. This nomenclature gives a simple descriptive classification, such as SV defect; right aortic sinus; ruptured; penetrating into right atrium. Other significant modifiers relating to etiology may be added at the end. A similar nomenclature for surgical therapy has also been developed, with the primary aim of standardizing database entry.

Morphology

The morphology of an SV aneurysm can vary from a small isolated enlargement of an aortic sinus (usually the right sinus) to an extended finger-like projection from the body or apex of the sinus. This tubular protrusion may extend into the adjacent structures, causing a myriad of clinical sequelae.

The right coronary sinus is the most common site for aneurysm formation (65% to 85%). The noncoronary sinus and the left sinus account for 10% to 30% and less than 5%, respectively. The rarity of left sinus aneurysms has led several authors to suggest that these may be due to a separate acquired etiology.

Associated Defects

The defects most frequently associated with SV aneurysm are the presence of a ventricular septal defect (30% to 60%), aortic valve regurgitation (20%), bicuspid aortic valve (10%), pulmonary stenosis, coarctation of the aorta, atrial septal defect, and, occasionally, coronary artery anomalies. There is also a known association with subvalvular aneurysms. Congenital weakness of both the aortic and mitral annuli has been implicated in this subgroup.

Epidemiology

SV aneurysms are rare, accounting for only 0.14% of all open-heart surgical procedures. Because they are often clinically silent for many years, autopsy studies may give a more accurate estimation of prevalence, and indicate approximately 0.09% of the general population. SV aneurysms are more common in Asian populations and, in addition, have a marked male preponderance (four times more common in men). The reasons for these racial and sex differences are unclear. To date, little is known about the underlying genetic determination of SV aneurysm. However, there have been a small number of case reports of patients with 22q11 deletions and SV aneurysm. Whether this association is causal or coincidental is not known.

A symptomatic SV aneurysm is particularly uncommon in childhood. In these circumstances, extra care should be taken to avoid overlooking a hereditary connective tissue disorder such as Ehlers-Danlos or Marfan syndrome.

Investigations