Pectus excavatum (PE), often called “sunken chest” or “funnel chest,” is the most common congenital deformity of the chest wall. This condition is characterized by an inward depression of the sternum, which can range from mild to quite severe. Since this structural anomaly alters the thoracic cavity, the potential impact on the heart is a significant clinical question.
Understanding Pectus Excavatum
Pectus excavatum is caused by the abnormal, excessive growth of the costal cartilage connecting the ribs to the breastbone. This overgrowth pushes the sternum inward toward the spine, creating the concave chest appearance. Although present at birth, the condition often becomes more pronounced during periods of rapid growth, especially in early adolescence.
The deformity occurs in approximately one in 300 to 1,000 live births and shows a clear male predominance, affecting males three to five times more frequently than females. While often viewed as an aesthetic concern, the degree of inward sternal displacement permanently alters the thoracic cavity and determines the impact on vital organs.
Mechanical Impact on the Heart
The sternum’s inward displacement reduces the anterior-posterior depth of the chest cavity, compressing the space available for the heart and other mediastinal structures. Because of its position immediately behind the sternum, the right side of the heart bears the brunt of this physical interference. The right ventricle, which is the most anterior chamber, is particularly susceptible to extrinsic compression.
This constant pressure on the right ventricle can cause its shape to become flattened or distorted, a phenomenon visible on imaging studies. The heart is often displaced from its normal position, commonly pushed toward the left side of the chest. This mechanical stress can also induce a rotation of the heart’s axis within the chest. The combination of displacement and compression can hinder the heart’s ability to fill completely with blood.
Specific Cardiac Symptoms and Functional Changes
The physical compression of the heart, especially the right ventricle, translates into measurable physiological changes, particularly under stress. The right ventricle’s main function is to pump deoxygenated blood to the lungs; when compressed, its capacity to fill during diastole is reduced. This reduction in filling volume directly results in a lower stroke volume, which is the amount of blood pumped out with each beat.
This limited stroke volume often leads to a lower overall cardiac output, especially when the body demands more oxygen, such as during physical exertion. Patients with moderate to severe pectus excavatum commonly experience symptoms like exercise intolerance and dyspnea, or shortness of breath, upon exertion. While the heart may function normally at rest, the inability to increase cardiac output adequately during activity causes these functional limitations.
Other common cardiac symptoms include palpitations, which are noticeable irregularities in the heartbeat. In some cases, the structural distortion of the heart can be associated with conditions like mitral valve prolapse. The resulting reduced aerobic capacity and fatigue are not due to a primary heart muscle disease but rather the mechanical restriction placed on the heart’s pumping action by the deformed chest wall.
Assessing Severity and Corrective Measures
The severity of pectus excavatum and its potential impact on the heart are commonly assessed using the Haller Index (HI). The HI is a ratio calculated from a cross-sectional computed tomography (CT) scan, dividing the maximum transverse diameter of the chest by the minimum anteroposterior diameter at the point of greatest sternal depression. A normal chest has an index around 2.5, while an index of 3.25 or greater is often used to define moderate to severe deformity and indicate candidacy for surgical correction.
Diagnostic tools used to evaluate cardiac function include the echocardiogram, which visualizes the heart’s structure and the degree of right ventricular compression. A cardiopulmonary exercise test objectively measures the patient’s functional capacity, often revealing a reduced maximal oxygen consumption (VO2max) and diminished stroke volume during activity.
When the deformity is severe and causes significant symptoms, surgical interventions are considered. The most common corrective procedure is the minimally invasive Nuss procedure, where a curved bar is inserted behind the sternum to push the breastbone outward. The traditional Ravitch procedure involves opening the chest to remove excess cartilage and reposition the sternum. The primary goal is to alleviate physical compression on the heart and lungs, which has been shown to improve cardiac function and exercise tolerance.