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Pectus excavatum - pathophysiology, clinical presentation, surgical repair

Pectus excavatum, also known as funnel chest, is the most common congenital defect of the chest wall, accounting for 90 percent of all congenital chest wall defects (others include pectus carinatum, bifid sternum, Cantrell's syndrome and Poland's syndrome).[1-3] Until now, most family physicians, internists and pediatricians have regarded pectus excavatum as principally a cosmetic problem, and it is discussed as such in standard texts.[1,4-8] However, recent studies have shown that impairment of cardiac and respiratory function with associated exercise intolerance can result from the abnormal chest wall of pectus excavatum.[1,7-14] In addition, studies have shown improvement in cardiac and respiratory function and exercise tolerance after surgical repair.[1,9,12,15-17] Because the estimated incidence of pectus excavatum is between one in 127[3] and one in 167,[10] most family physicians will encounter several patients with this condition.



The underlying cause of pectus excavatum is unknown. Most authorities currently believe the condition is the result of an unbalanced overgrowth of the rib cartilages, which pushes the sternum inward.[1,3,7,18] The older theory implicating a short subxiphoid tendon (central tendon of the diaphragm) as the cause has been discounted.[7,8,10] It is now understood that the short subxiphoid tendon is the result, not the cause, of pectus excavatum.[1,8]

The sternal depression most commonly begins at the attachment of the third rib to the sternum, but occasionally it is noted at other positions.[9,15] The defect is usually present at birth but progression is variable.[8-10,15,19] In some relatively mild cases, the severity of the condition may worsen with the pubertal growth surge.[2,3,8-10] The ratio of boys to girls affected has been estimated to be between 2:1[9,10] and 3:1.[3,9] A familial distribution through a nonsexlinked gene has been suggested,[3] although some authorities believe the condition occurs in a sporadic fashion.[8-10,15]

A characteristic abnormal respiratory pattern may occur on exertion, causing retraction of the sternum and lateral movement of the chest wall.[1,8,15] Increased oxygen uptake during maximal exertion is thought to occur as a result of a greater expenditure of energy due to the abnormal chest architecture.[7,11,13] Decreased pulmonary and cardiac function on heavy exertion have been documented over the past 15 years in adolescents and adults with pectus excavatum and more recently in children with severe cases.[1,7-9,12,15,20]

The posterior displacement of the lower sternal segment moves the heart and middle mediastinal contents posteriorly and to the left, and creates a rotational effect in severe cases.[2,4,8,9,12,15,17] This causes cardiopulmonary dysfunction due to elevated right atrial pressure and impaired diastolic filling of the right atrium and ventricle,[8,9,15,20] resulting in decreased stroke volume and cardiac output during upright exercise.[20]

Many patients with pectus excavatum have heart murmurs and abnormal electrocardiograms, which may be due to the indentation of the heart and its lateral displacement and rotation. These abnormalities usually disappear postoperatively.[8,9,15,16]

Clinical Presentation

The depression of the sternum associated with pectus excavatum is usually noted at birth,[1,10,15] indicating that the condition originates in utero. Although reports of pectus excavatum appeared in the medical literature for hundreds of years,[1,15] Ravitch[14] published the first detailed description of pectus excavatum in 1949. He noted five characteristics: depressed sternum, rounded shoulders, slight dorsal kyphosis, prominent potbelly and abnormal retraction of the sternum on deep inspiration[1,14] Figures 1 and 2).

Pectus excavatum may occur in otherwise normal children or may be associated with minor congenital anomalies, such as pes planus and scoliosis. It may also occur in more severe forms as part of such conditions as Marfan's syndrome and certain cardiac defects.[3,8-10,15]

Infants and young children with this condition are often brought to the physician by their parents because of concern about the appearance of the chest. Since pectus excavatum diagnosed in the first year of life may improve or completely disappear without treatment in a significant number of cases, close observation is indicated. If improvement does not occur by age three, spontaneous remission is unlikely; it virtually never occurs after age six.[9,19]

Adolescents often have a rapid growth surge that accentuates the defect,[2,3,8-10] heightening concerns in this already emotionally vulnerable age group. Patients with pectus excavatum are often self-conscious; hence, many authorities recommend early repair, before the patient's peers are old enough to notice the defect.[2,3,7-10,15] Ages four to six, when the child is ready for a hospital experience, are frequently recommended as the optimal ages for surgical repair. However, in cases in which a relatively mild defect worsens during puberty, the defect may be surgically corrected at that time.[2,3,7-10,15] In a few cases, the defect has been corrected in adulthood.[7,10,12,15,17,21]

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