Pectus excavatum is a common congenital chest wall deformity where the breastbone and connecting rib cartilages grow inward, creating a sunken or caved-in appearance in the chest. This structural abnormality, sometimes called funnel chest, is the most frequently seen chest wall malformation, affecting approximately one in 400 to 1,000 births. While the condition is often considered a cosmetic issue, its impact extends beyond appearance, especially in more severe cases. The primary concern is whether this inward sternal pressure can physically interfere with the function of the heart. The relationship between a sunken chest and the heart is complex, but the deformity can indeed affect the heart’s position and function, particularly during physical activity.
Understanding Pectus Excavatum and Severity Assessment
Pectus excavatum is characterized by a dorsal deviation of the sternum and the third to seventh rib cartilages. The defect may be present at birth or develop and worsen during rapid growth periods, such as adolescence. Since the external appearance of the chest does not always reflect the true extent of the internal compression, objective measurements are required to assess the deformity’s severity. This quantification is typically performed using cross-sectional imaging, such as a Computed Tomography (CT) scan or Magnetic Resonance Imaging (MRI).
The most widely accepted metric for assessing the degree of the defect is the Haller Index (HI). The Haller Index is a ratio calculated by dividing the maximum transverse diameter of the chest by the shortest anteroposterior distance between the sternum and the spine. A normal chest has an HI of 2.5 or less. An index value greater than 3.2 is generally considered severe and often serves as a threshold for considering surgical intervention.
The Physical Mechanism of Cardiac Displacement and Compression
The anatomical problem created by pectus excavatum is a reduction in the space between the sternum and the spine, which houses the heart and lungs. When the sternum sinks inward, it directly impinges upon the mediastinum, leading to mechanical interference with the organs inside. The physical pressure from the sunken chest wall forces the heart to shift out of its normal position, most often displacing it toward the left side of the chest. This displacement can also cause the heart to rotate within the chest cavity.
The inward sternum can directly compress the heart chambers, especially the right ventricle, which is the most anterior chamber. The right ventricle is particularly susceptible to this external pressure due to its location directly behind the breastbone. This physical compression reduces the available volume for the right ventricle to fill with blood during the relaxation phase of the heart cycle, known as diastole. The heart must then work harder to compensate for this restricted filling, a problem that is amplified during periods of increased physical exertion.
Specific Cardiovascular Consequences and Symptoms
The mechanical compression and displacement of the heart can lead to measurable functional consequences, particularly when the patient is active. The most common functional issue is a reduction in the heart’s stroke volume and overall cardiac output, especially during strenuous exercise. This inability to pump blood efficiently under load manifests as patient symptoms like exercise intolerance and easy fatigue.
The external pressure can also cause several specific cardiovascular symptoms:
- Shortness of breath (dyspnea), occurring because the compressed heart and sometimes the lungs cannot meet the body’s oxygen demands during exertion.
- Electrical abnormalities, with some patients experiencing palpitations or a fast, fluttering heart rate due to cardiac arrhythmias.
- Mitral Valve Prolapse (MVP), which can occur if the heart’s displacement stretches the mitral valve apparatus.
- A heart murmur may also be detected.
Criteria for Surgical Intervention Based on Cardiac Impact
Not all cases of pectus excavatum require surgical correction, and the decision to operate often depends on the physiological impact of the deformity, not just its appearance. When the condition causes significant cardiopulmonary compromise that affects the patient’s quality of life, surgical repair is frequently recommended. One of the most important objective criteria for intervention is a high Haller Index, specifically a value of 3.25 or greater, when combined with functional symptoms.
The need for surgery is strongly supported by diagnostic tests that confirm heart impairment. These tests often include echocardiograms to visualize cardiac compression and rotation, and cardiac stress tests to document reduced cardiac output or exercise capacity. Procedures like the Nuss procedure or the Ravitch technique aim to relieve the pressure on the heart and lungs by repositioning the sternum. Successful surgical correction has been shown to improve cardiac function and enhance a patient’s exercise tolerance by physically decompressing the heart.