Isthmus

Isthmus

The Common Vein Copyright 2007

Ashley Davidoff MD

The isthmus is a slight constriction (approximately 3 mm) of the aorta just proximal to the point of attachment of the ductus arteriosus and distal to the origin of the left subclavian. It is characterized structurally by minimal narrowing of the tubular segment at that point. It serves as a marker for the site of the ductus arteriosus in fetal circulation and for the ligamentum arteriosum, a fibrous remnant in the child and adult. The narrowing of the aorta is simply the remnant of the embryologic structure.  Common diseases at this include atherosclerosis, coarctation of the aorta and patent ductus arteriosus. Diagnostic studies include CT imaging, aortography, MRI and echocardiography.  Surgical treatment is most common.

Ligamentum Arteriosum and Isthmus

47680 right ventricle heart cardiac right ventricular outflow tract ligamentum arteriosum ductus arteriosus aorta isthmus Davidoff art Davidoff MD

Aortic Isthmus

35324b04 thoracic aorta ascending aortic valve sinus of Valsalva normal Courtesy of Laura Feldman MD code aorta arch artery ascending descending normal thorax

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Minor Isthmic Narrowing as Seen on the MRI

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Ductus Diverticulum

72871.800 aorta thorax abdomen arch ascending descending abdominal progressive and gradual size change ductus diverticulum normal anatomy CTscan Courtesy Ashley Davidoff MD

Applied Biology

Patent Ductus Arteriosus

PDA is a congenital persistence of an emryolog shunt  – cause unknown sometimes in isolation sometimes in association with other congenital lesions results in left to right shuny increased blood flow to lungs relative decrease in flow to body with most clinical manifestations relating to increase fow  Left untreated the iolated lesion will usuallyprogress to pulmonary hypertension and eventually Eisenmenger physiology meaning shunt goes right to left with subsequent cyanosis

dx echocardiography rx Non invasive chemical and surgical intervention are all options

Patent Ductus Arteriosus

42326.800 aorta pulmonary artery finding PDA patent ductus arteriosus left to right shunt arteriovenous malformation CTscan Courtesy Ashley Davidoff MD

Coarctatation of the Aorta

Congenital – may be in isolation part of the HLHS or in association with other congenital heart diseases dx imaging echo sometimes MRI rx Non invasive techniques and surgical

Few types – most common is at the level of the istmus

Aortic Valve Atresia in the Setting of Hypoplastic Left Heart Syndrome

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Coartcation of the Aorta

00254c04 This combination of an angiogram and MRI show a focal coarctation of the aorta distal to the dilated left subclavian artery. Note the large internal mammary artery in the angiogram (a) Courtesy Ashley Davidoff MD 00254c02 CVS aorta thorax thoracic aorta coarctation

Aortic Interruption

Congenital – may be in isolation part of the HLHS or in association with other congenital heart diseases dx imaging echo sometimes MRI rx Non invasive techniques and surgical

Aortic Interruption at the Level of the Isthmus

The most obvious finding in this CXR (a) with pleuro-parenchymal changes is not the most significant. In image (b) the highlighted ribs reveal rib notching characteristic of coarctation of the aorta. The lateral examination (c) in this instance is not helpful. In the early phase of the angiogram(d), there appears to be complete interruption of the aorta with a large left subclavian artery acting as a collateral pathway. The sbsequent images e, and f, show progressive filling of the isthmus and distal thoracic aorta. The coarcatation becomes apparent characterised by a “3” sign. 35107c Courtesy Laura Feldman MD code CVS artery aorta thorax coarctation rib notching bone collateral

Aortic Trauma

already did this in ascending tubular portion Acute traumatic – cause deceinjury MVA dx imaging CT scan rx surgery – evlving  minimally invasive techniques

Few types – most common is at the level of the isthmus

Traumatic Pseudoaneurysm at the Level of the Isthmus

35260 Courtesy of Laura Feldman MD. code aneurysm aorta artery pseudoaneurysm thorax trauma traumatic anerusym