Scoliosis is an abnormal, three-dimensional lateral curvature of the spine, most often diagnosed during adolescence. While the condition primarily affects the musculoskeletal system, the spine’s proximity to the chest cavity raises questions about its impact on internal organs. Scoliosis can affect the heart, but this consequence is rare and generally only occurs in cases of severe, untreated curvature. The connection is indirect, mediated first by restricted lung function, which then burdens the cardiovascular system.
How Severe Spinal Curvature Reduces Thoracic Space
The spine’s abnormal sideways curve and rotational twist in severe scoliosis distort the entire thoracic cage, which houses the heart and lungs. This structural change significantly reduces the available volume within the chest cavity. The lateral curvature causes the ribs on one side to become compressed and crowded, while the ribs on the opposite side are widely separated, creating an uneven and restricted space.
This mechanical restriction prevents the lungs from expanding fully during inhalation. The result is a restrictive ventilatory defect, diminishing the total amount of air the lungs can hold (vital capacity). The chest wall also becomes stiffer due to the fixed deformity, further limiting the movement needed for deep breathing.
The reduced lung volume forces respiratory muscles to work harder to achieve adequate airflow. Over time, this chronic underinflation can alter the properties of the lung tissue, making expansion more difficult. This mechanical compression and resulting decline in lung function is the primary factor leading to cardiovascular complications.
The Resulting Strain on the Cardiovascular System
The compromised lung function initiates events that affect the heart. When the lungs are chronically under-ventilated, the body struggles to maintain adequate oxygen levels, resulting in chronic hypoxemia. This low oxygen state triggers a reflex where the small blood vessels in the lungs, the pulmonary arteries, constrict.
This widespread constriction of the pulmonary arteries drastically increases pressure within the vessels leading to the lungs, a serious condition called pulmonary hypertension. The right ventricle is responsible for pumping blood through these pulmonary arteries. As resistance increases, the right ventricle must exert significantly more force to push blood forward.
The right ventricle is not built to sustain this high-pressure workload and eventually begins to strain and weaken. This prolonged overexertion leads to right-sided heart failure, clinically known as Cor Pulmonale. The heart complication is not a direct result of the spine pressing on the heart, but a secondary consequence of the severe lung disorder created by the spinal deformity.
Identifying the Threshold for Cardiopulmonary Risk
The risk of developing cardiopulmonary complications correlates directly with the severity of the spinal curvature, measured using the Cobb angle. A Cobb angle of 10 to 25 degrees is considered mild, and the cardiorespiratory system is almost always unaffected. Curves measuring 25 to 45 degrees are classified as moderate; pulmonary function may show slight changes but typically does not lead to clinical symptoms or cardiac strain.
Significant heart and lung impairment occurs only in cases of severe scoliosis, usually when the Cobb angle exceeds 70 to 80 degrees. At this level, the mechanical distortion of the chest cavity is profound enough to cause chronic respiratory failure, leading to pulmonary hypertension and Cor Pulmonale. For most patients, the cardiorespiratory system remains functional and healthy, making severe complications uncommon in the overall scoliosis population.
Interventions Focused on Protecting Heart and Lung Function
Medical intervention in severe scoliosis aims to protect the heart and lungs from strain. The definitive treatment for curves approaching or exceeding the 70-degree threshold is surgical correction, typically involving spinal fusion and the placement of corrective rods. The goal of this surgery is to reduce the spinal curve, increasing the thoracic volume and relieving mechanical compression on the lungs.
A successful surgical correction can lead to a significant increase in vital capacity, alleviating the underlying cause of pulmonary hypertension. Before or in conjunction with surgery, non-surgical support is used to manage existing cardiopulmonary symptoms. This may include oxygen therapy to counteract chronic hypoxemia and ventilatory support to assist with breathing.
Pulmonary rehabilitation, which includes targeted breathing exercises, improves chest wall mobility and lung function. These exercises teach patients how to breathe into the collapsed areas of the chest cavity. The combination of surgical correction to fix the anatomy and supportive care to manage the physiology offers the best path to reversing the negative strain on the cardiovascular system.