Scoliosis, a three-dimensional, lateral curvature of the spine, can affect the body beyond musculoskeletal structure. While most mild and moderate cases do not cause serious internal organ issues, severe spinal deformity can compromise the function of the heart and lungs. The connection is usually not a direct defect of the heart muscle, but a secondary complication resulting from physical changes in the chest cavity. This risk is generally confined to the most severe and progressive forms of the condition.
How Severe Spinal Curvature Restricts the Chest Cavity
The primary mechanism by which severe scoliosis impacts cardiopulmonary health is through the deformation of the rib cage and a reduction in chest volume. The sideways curve of the thoracic spine causes the ribs to twist and become crowded. This twisting physically reduces the total space available inside the chest cavity.
The lungs require sufficient space to fully expand during inhalation, and this restriction directly impairs their ability to inflate. This limitation is known as a restrictive ventilatory defect, meaning the lungs cannot hold a normal volume of air. A significant reduction in lung capacity sets the stage for respiratory and cardiac complications.
The Development of Cardiopulmonary Complications
The mechanical restriction of the lungs leads to chronic underventilation, causing oxygen levels in the blood to decrease, a state called chronic hypoxemia. The body attempts to compensate by constricting the small arteries within the lungs. This constriction, known as pulmonary hypertension, increases the resistance to blood flow.
The right side of the heart pumps deoxygenated blood into the lungs against this increased resistance. Over time, the right ventricle must work harder to push blood through the constricted vessels. This sustained workload causes the right ventricle walls to thicken and eventually weaken, resulting in right-sided heart failure. This specific type of heart failure caused by chronic lung disease is termed Cor Pulmonale.
Cardiopulmonary complications are typically associated with severe, progressive curves. However, recent research suggests an increased lifetime risk of major adverse cardiovascular events even in adults with milder scoliosis. Direct mechanical compression of the heart by a distorted rib cage can also impact function, leading to changes in heart rhythm or reduced efficiency.
Key Factors Determining Risk in Scoliosis Patients
The likelihood of developing cardiopulmonary issues depends strongly on specific characteristics of the spinal curve. The most important measurement is the Cobb angle, which quantifies the degree of curvature. Generally, a curve must exceed 70 to 80 degrees before it causes a substantial limitation in lung capacity.
The location of the curve is also a major determinant, with thoracic spine curves posing a much higher threat than those only in the lower lumbar region. Thoracic curves directly distort the rib cage, while lumbar curves do not affect chest cavity geometry. Early-onset scoliosis developing before age ten also plays a significant role, as it interferes with the crucial growth and development of the lungs and chest wall. This interference can lead to pulmonary hypoplasia, which dramatically increases the long-term risk of breathing and heart problems.
Screening and Management of Associated Heart Issues
For patients identified as high-risk, ongoing monitoring of cardiopulmonary function is essential to detect complications early. Diagnostic tools include Pulmonary Function Tests (PFTs), which measure lung volumes such as forced vital capacity (FVC) and forced expiratory volume (FEV1). A significantly reduced FVC value, often below 70% of the predicted value, indicates serious restrictive lung impairment.
To evaluate the heart, an echocardiogram is commonly used to visualize the heart’s structure and performance, checking the function of the right ventricle and looking for signs of pulmonary hypertension. Treatment aims to reduce the mechanical burden and manage resulting cardiac conditions. In cases of severe curvature, surgical correction of the spine may be performed to restore chest volume and prevent further progression of restrictive lung disease. Medical management of established pulmonary hypertension may involve specific medications, such as vasodilators, to relax constricted lung vessels and reduce the heart’s workload.