Cardiopulmonary Manifestations of Pectus Excavatum - Page 3

Cardiopulmonary Manifestations

Although the majority of individuals experience minimal to no symptoms, pectus excavatum can be associated with numerous cardiopulmonary manifestations. Patients tend to become symptomatic during adolescence or early adulthood as pectus deformities become more prominent. The inward concavity of the anterior chest wall can displace mediastinal structures, compromise cardiac output, or impair normal pulmonary function. These can significantly alter a patient's functional capacity and exercise tolerance. As such, the most commonly reported symptom among patients with pectus excavatum is exertional dyspnea.

Patients may experience some degree of functional limitations or exercise intolerance. The reduced exercise capacity is primarily related to exertional dyspnea caused by a diminished stroke volume and ventilatory restrictions. However, there is no clear consensus as to the extent of cardiopulmonary limitations associated with pectus excavatum or the functional benefits of corrective surgery.

In a study of Air Force recruits, those with pectus excavatum were found to have a diminished exercise tolerance and reduced maximum voluntary ventilation compared with those without this defect .^[10] In a study by Rowland and associates,^[11] patients with pectus excavatum demonstrate a lower level of aerobic fitness and endurance compared with controls. The degree of exercise intolerance was not predicted by the severity of deformity as measured by the Haller index.

Cardiopulmonary exercise testing has also established the functional limitation resulting from pectus deformities.^{[11,12,13,14]} The most commonly identified cardiac limitation is a reduced stroke volume, which may occur at rest or with submaximal exertion.^{[11,12,13,14,15]} This may become exaggerated with strenuous exertion, leading to a diminished exercise capacity. A depressed breathing capacity and tidal breathing during exertion has been observed.^[11,15,16] However, the minute ventilation is typically preserved. Patients may also experience a reduced maximum oxygen consumption (VO₂max). In one series, the mean VO₂max was reduced to 75% of predicted .^[11] A reduced O₂ pulse may be seen, reflecting a diminished stroke volume with exercise. Other abnormalities seen on exercise testing include an earlier anabolic threshold and increased VO₂ for a given work rate.^[12,13,14]

Cardiac manifestations result from the posterior displacement of the sternum, producing an anterior indentation and deformity of the right ventricle. In severe cases, the heart may become rotationally displaced into the left hemithorax. This displacement can cause mechanical compression and obstruction to normal outflow which may impede normal stroke volume, especially during exercise. This diminished cardiac stroke volume has been well established, especially in a seated or upright position. Of note, stroke volume tends to normalize while supine.

Valvular abnormalities are common among patients with pectus excavatum, particularly mitral valve prolapse. In one series, systolic murmurs were auscultated in 46% of cases not associated with an underlying connective tissue disorder.^[5] The prevalence of murmurs was independent of the degree of deformity in this study. Mitral valve prolapse is a well-recognized association and is thought to result from deformities of the mitral annulus produced by anterior compression of the heart. It occurs in 20% of patients with pectus excavatum.^[17] Resolution occurs in over 50% of individuals following corrective surgery .^[17]

The chest wall and thoracic cage are significant components of normal pulmonary physiology. Deformities of these structures can lead to restrictive lung defects and impaired ventilation-perfusion matching, resulting in dyspnea or exercise limitations. The concaved sternum and anterior displacement seen in pectus excavatum reduces the intrathoracic volume, resulting in a restrictive ventilatory defect with reductions in both total lung capacity and vital capacity.^[10,18] This restriction is usually mild but may be more pronounced with more severe displacements of the sternum. Lung compliance, however, is typically normal. The restrictive defect and abnormal chest wall mechanics lead to increased work of breathing, further contributing to the diminished exercise capacity observed in these patients.

Parenchymal compression from pectus deformities may result in the development of other anatomic abnormalities. External compression of the airways may produce airflow obstruction and clinical asthma. Patients may experience recurrent lower respiratory tract infections with a predilection for nontuberculous mycobacterial infections.^[19] These recurrent infections lead to the subsequent development of bronchiectasis, typically involving the right middle lobe and lingula, often referred to as "Lady Windermere's syndrome."

While the atypical appearance of the chest wall is purely cosmetic in the majority of cases, it can have a profound psychosocial impact, particularly in young women. This often represents more significant impairments than the underlying cardiopulmonary manifestations. Difficulties with self-esteem and body image perception are common, especially among teenagers. In a study by Eisiedel and Clausner,^[20] the authors found that pectus excavatum resulted in significant psychological or psychosocial impairments, with over two thirds of adolescents experiencing some negative emotional trait(s) related to their deformity. As such, cosmetic repair is the most frequent reason for surgical correction.