pectus excavatum etiology and evaluation

1/19/12 Pectus excavatum: Etiology and evaluation

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AuthorOscar H Mayer, MD

Section EditorGregory Redding, MD

Deputy EditorAlison G Hoppin, MD

Pectus excavatum: Etiology and evaluation

Disclosures

Last literature review version 19.3: January 2012 | This topic last updated: May 25, 2011

INTRODUCTION — Pectus excavatum (PE), or "funnel chest", is a deformity of the chest wall

characterized by a sternal depression typically beginning over the midportion of the manubrium and

progressing inward through the xiphoid process.

The clinical significance of PE depends on three issues:

Severity of the chest wall defect

Cardiopulmonary morbidity

Psychosocial impact of the defect, and its appearance on the patient

Despite decades of experience with surgical and nonsurgical treatment, and efforts to quantify

outcomes in each of these areas, the decision of when and how to treat PE remains controversial.

These issues are discussed in a separate topic review. (See "Pectus excavatum: Treatment".)

This topic review will discuss the epidemiology, clinical features, and evaluation of PE.

The diagnosis and treatment of pectus carinatum and other chest wall deformities are reviewed

separately. (See "Pectus carinatum" and "Diseases of the chest wall".)

EPIDEMIOLOGY — PE accounts for 90 percent of anterior chest wall disorders [1]. The incidence

of pectus excavatum is 1 in every 400 to 1000 live births [1,2]. It is three to five times more

prevalent in males than females.

ETIOLOGY — While there is no consensus for what causes PE, there have been a number of

hypotheses, ranging from disproportionate muscular force putting abnormal stress and strain on the

sternum and costal cartilages, to defective cartilage structure and growth, or combinations thereof.

An early theory that PE is caused by abnormal diaphragmatic connections was discarded, because

surgical interventions to release the central tendon and substernal ligament in early childhood were

not effective [3]. (See "Pectus excavatum: Treatment", section on 'Historical approaches'.)

PE is usually sporadic [1], but it has been associated with connective tissue disorders (particularly

Marfan syndrome, Ehlers Danlos syndrome, and osteogenesis imperfecta) [4] and neuromuscular

disease (eg, spinal muscular atrophy). It also can be seen in a variety of other genetic conditions,

including Noonan syndrome, Turner syndrome, and multiple endocrine neoplasia type 2b [5]. (See

"Genetics, clinical features, and diagnosis of Marfan syndrome and related disorders".)

The increased prevalence of PE in connective tissue disorders suggests the possibility that it is

caused by abnormal cartilage development [6]. In particular, some authors have hypothesized that

the deformity is caused by abnormalities of cartilage remodeling due to an imbalance between

cartilage growth-promoting and growth-inhibiting genes [1]. Genetic contributors to PE seem likely,

and familial patterns of inheritance have occasionally been reported [7,8]. Several different genes



affecting cartilage growth are associated with syndromic causes of PE (eg, fibrillin1 gene in Marfan

syndrome and genes in the RasMAPK pathway in Noonan syndrome). However, no specific genetic

triggers for abnormal cartilage growth in nonsyndromic (isolated) PE have been identified [9].

Cartilage samples from patients with pectus excavatum have normal histology [6].

PE may also occur in response to underlying pulmonary conditions. Patients with a repaired

congenital diaphragmatic hernia are prone to PE, presumably because the axis of contraction of the

diaphragm is more horizontal than vertical, and therefore pulls the lower edge of the sternum inward

[6]. Patients with spinal muscular atrophy type 1 are also prone to developing PE, presumably

because the chest wall is highly compliant and unable to resist intrapleural pressure variation during

respiration; these forces gradually deform the sternum over time. PE also can occur in children with

subglottic stenosis and bronchopulmonary dysplasia. (See "Congenital diaphragmatic hernia in the

neonate" and "Spinal muscular atrophy".)

NATURAL HISTORY

Information on the evolution of untreated PE is based upon limited retrospective data and reports of

clinical impressions [10-12]. The following observations are generally accepted:

About one third of cases of PE present in infancy [6].

Spontaneous regression of PE in infancy is rare [2]. The frequency of spontaneous

improvement decreases further after one year of age, and no spontaneous improvement can

be expected after six years of age.

After 12 years of age, the PE deformity worsens in one-third of patients during the

adolescent growth spurt, and remains the same in two-thirds [10,13]. There are no reliable

markers to predict progression.

As PE worsens, simple symmetrical lesions may progress to more complex asymmetric

deformities [13-16].

No debilitating physiologic disabilities or deaths have been attributed to PE in children or young

adults [10]. In adults, complaints of exercise intolerance are common; no deaths have been

attributed to the isolated deformity.

CLINICAL FEATURES

Cosmetic concerns — Concerns about physical appearance are common among patients with PE

who seek medical attention [1,2]. Female patients are more likely to express concern over their

appearance than male patients (68 versus 40 percent) [17]. However, there is poor correlation

between the severity of PE and concern about appearance [17]. One longitudinal study suggests

that cosmetic concerns subside over time: among patients with mild PE who did not undergo

surgery, the concern about appearance usually subsided by 18 to 20 years of age [18].

Symptoms — Among a large group of patients evaluated for PE, most of whom were in the

pediatric age range, the following symptoms were reported [19]:

Exertional intolerance — 82 percent

Chest pain — 68 percent

Poor endurance — 67 percent

Shortness of breath — 42 percent

In a separate study, similar frequencies of these problems were reported in a group of 50 adults

with PE [18]. While young children are less likely to display these symptoms, they may develop



during adolescence, sometimes in as little as six months [19].

EVALUATION — Patients with PE should be evaluated to estimate the severity of the deformity,

and whether there are associated anomalies.

Patients with moderate or severe PE, or with complaints suggesting cardiorespiratory compromise,

should be evaluated by computed tomography (CT) to quantify the severity of PE. They should also

undergo pulmonary function testing to assess for restrictive lung disease, and exercise testing to

assess for cardiopulmonary limitation. If there is significant displacement of the heart or

cardiopulmonary limitation, we suggest performing echocardiography and electrocardiography. (See

'Cardiac Function' below.)

For patients not deemed to be candidates for surgical correction after the initial evaluation, it is

important to repeat the examination periodically. This is especially important during periods of rapid

growth, such as adolescence, because the deformity and associated symptoms may increase

markedly [20]. (See 'Natural History' above.)

Physical examination

Sternal depression — The sternal depression can be qualitatively assessed on visual

examination (figure 1). The depression can be measured quantitatively using calipers to

compare the distance between the point of maximal sternal depression and the spine, with

similar measurements laterally in each mid clavicular line [21]. One author suggested that a

difference between the two measurements (the depth of depression) of >2.5 cm constitutes

a moderate to severe defect [21]. Caliper measurements can also be useful in assessing

asymmetry and describing the chest wall contortion [22].

Thoracic abnormalities — In addition to the sternal depression, patients with PE often have a

narrowed chest wall diameter and a flat, broad, and kyphotic chest [23]. Between 10 and 39

percent of patients with PE also have associated scoliosis, which may be severe

[2,6,19,24,25]. Scoliosis may present early or late in the course of pectus excavatum, and it

is unclear whether chest wall repair affects the onset or progression of scoliosis.

Respiratory function — Resting tachypnea has been reported by up to 98 percent of patients

and can be more prominent in adolescence [2]. Patients with more severe forms of pectus

excavatum are much more likely to have reduced aerobic capacity. Although laryngomalacia

has been reported in infants with pectus excavatum, upper or lower respiratory abnormalities

are uncommon findings on physical exam [4].

Cardiac examination — Abnormalities of the cardiac examination may be seen in patients with

associated syndromes (eg, Noonan or Marfan), because these syndromes are associated with

cardiovascular anomalies, but are unusual in patients with isolated PE. (See "Genetics, clinical

features, and diagnosis of Marfan syndrome and related disorders" and "Causes of short

stature", section on 'Noonan syndrome'.)

Patients with severe PE can have tachycardia due to a reduced stroke volume, depending on the

distortion and displacement of the heart [22]. Functional systolic murmurs are heard in about 18

percent of patients, probably due to compression of the left ventricular outflow tract [2]. Mitral

valve prolapse has been reported in 7 to 20 percent of patients with pectus excavatum [2,4].

Imaging — Plain radiographs in the anteroposterior and lateral planes have limited value in

assessing the pectus defect, but they can be useful in evaluating for coincident kyphoscoliosis or

lung disease.



CT scan — CT scans are useful to accurately determine the severity of the pectus defect and

its impact on the lungs, heart, and large vessels [6]. Three-dimensional reconstructions can be

performed to assess the defect from a variety of different angles [26]. The pectus severity index

(PSI), also known as the Haller index, describes the depth of the pectus defect by comparing the

ratio of the lateral diameter of the chest to the distance between the sternum and spine, at the

point of maximal depression (figure 2) [27]. A normal chest has a PSI of 2.5 [28]. Among patients

referred for surgery based on clinical criteria (ie, without consideration of CT scan results), all

patients had a PSI of >3.25, whereas patients with PE who were not referred for surgery had PSI

<3.25 [27].

Other protocols have been developed to assess the pectus defect at different levels through the

thorax, evaluating asymmetry by comparing the anteroposterior diameter at each mid axillary line to

the lateral diameter [29]. Other indices have been proposed to measure thoracic and cardiac

distortion in an effort to quantify the severity of PE and define thresholds for surgical intervention

(figure 3) [30,31]. Magnetic resonance imaging also has been successfully used for this purpose

and has the advantage of avoiding radiation exposure [32].

Pulmonary Function — Abnormalities on pulmonary function testing are two to three times less

common than subjective pulmonary complaints in patients with PE, and the correlation between the

two is weak [18]. Forced vital capacity (FVC) is normal in the vast majority of patients [6,28,33-

35]. Interestingly, the total lung capacity (TLC), residual volume (RV), and RV/TLC results are more

variable [1,34,35]. However, normal pulmonary function tests do not exclude the possibility of

cardiopulmonary limitation during exercise. (See 'Exercise Testing' below.)

Cardiac Function — Patients with PE commonly have cardiac displacement to the left. In one large

series of female patients, 68 percent had electrocardiographic evidence of right ventricular strain

[36]. Electrocardiographic evidence of right axis deviation and ST segment depression in patients

with severe PE usually reflects rotation and compression of the heart rather than an intrinsic

myocardial abnormality [2].

Echocardiography has demonstrated subtle right ventricular outflow obstruction and reduced right

ventricular systolic function in patients with severe PE [37,38], and these measures improve after

surgical treatment [39,40]. (See "Pectus excavatum: Treatment", section on 'Outcomes'.) The

cardiac distortion may be associated with conduction abnormalities, such as bundle branch block,

which were present in 16 percent of patients in one series [6].

Exercise Testing — For detecting cardiopulmonary abnormalities, exercise testing is more sensitive

than spirometry or thoracic gas volume measurements performed at rest [1,41]. This may be

because exercise testing evaluates the interplay between the cardiac and pulmonary systems.

Exercise testing demonstrates mild impairment in some patients with severe PE, and the degree of

impairment correlates with the severity of the defect. This exertional limitation is due to

cardiovascular dysfunction rather than ventilatory limitation or physical deconditioning, as

illustrated by the following studies:

In one series, patients with PE exhibited mildly reduced maximum oxygen uptake (VO2max 75

percent of predicted) [28]. The threshold for lactate accumulation was abnormally low,

particularly in patients with severe PE (pectus index >4). Total lung capacity, residual

volume, and ventilatory reserve volume were normal.

In another series, the increase in tidal volume (Vt), Vt/FVC, and respiratory rate during

exercise were normal, indicating that exercise was not restricted by the chest wall deformity

[35].



By contrast, a third series found that the Vt/FVC was lower, and the respiratory rate higher

during exercise testing in patients with PE as compared to normal controls, perhaps indicating

a higher metabolic cost of breathing in an mechanically inefficient system [42].

SUMMARY AND RECOMMENDATIONS — Pectus excavatum (PE), is a deformity of the chest wall

characterized by a sternal depression beginning over the midportion of the manubrium and

progressing inward toward the xiphoid process.

PE is usually sporadic, but it has been associated with connective tissue disorders, such as

Marfan syndrome and Ehlers Danlos syndrome, neuromuscular disease, and a variety of other

genetic conditions, including Noonan syndrome and Turner syndrome. The pathogenesis of PE

and reasons for these associations are not well established. (See 'Etiology' above.)

PE can be present at birth, and in some cases may resolve. However, it tends to worsen

during the rapid growth of adolescence. (See 'Natural History' above.)

Patients with PE typically present with cosmetic concerns, but many patients also report

exercise intolerance and shortness of breath. (See 'Clinical features' above.)

Evaluation of a patient with moderate or severe PE includes quantification of the sternal

depression using measurements from chest CT scanning (known as the pectus severity index,

PSI). A typical candidate for surgery usually has a PSI of >3.25. (See 'Imaging' above.)

Candidates for surgical intervention should undergo electrocardiography and

echocardiography, as well as pulmonary function testing and exercise testing, if available.

(See 'Evaluation' above.)

Lung volumes are typically normal. (See 'Pulmonary Function' above.)

Electrocardiography may demonstrate right axis deviation and ST segment depression,

which reflects rotation and compression of the heart. Some patients have conduction

abnormalities, such as bundle branch block. Echocardiography may demonstrate subtle

right ventricular outflow obstruction and reduced right ventricular systolic function in

patients with severe PE. (See 'Cardiac Function' above.)

Exercise testing demonstrates mild impairment in many patients with PE. The impairment

correlates with the severity of the defect, and is consistent with cardiovascular

dysfunction rather than ventilatory limitation or physical deconditioning. (See 'Exercise

Testing' above.)

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GRAPHICS

Pectus excavatum

Pectus excavtum in an adolescent patient demonstratingsevere invagination of the lower sternum. The patient hadsignificant exercise intolerance. Reproduced with permission from:

Chung, EK. Visual Diagnosis in Pediatrics. Philadelphia: Lippincott Williams

& Wilkins, 2006. Copyright © 2006 Lippincott Williams & Wilkins.



Measurement of the pectus severity index

Pectus severity index (PSI) in a normal chest (PSI = 2.0) andin a patient with severe pectus excavatum (PSI = 3.5). Courtesy

of Dr. Oscar H Mayer.



Pectus excavatum cardiac distortion

CT scan of the chest in a patient with pectus excavatum andsignificant cardiac distortion represented as the cardiaccompression index (H/M) and as the cardiac asymmetry index(P/M) at the xiphoid process. Reproduced with permission from:

Haller, JA, Scherer, LR, Turner, CS, et al. Evolving management of pectus

excavatum based on a single institutional experience of 664 patients. Ann

Surg 1989; 209:578. Copyright © 1989 Lippincott Williams & Wilkins.



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pectus excavatum etiology and evaluation

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