An autoimmune disease is a disorder where the body’s immune system mistakenly identifies healthy tissues as foreign invaders and launches an attack against them. This error leads to chronic inflammation and damage in various parts of the body, including organs like the joints, skin, nerves, and kidneys. Although protected by its own surrounding sac and robust muscle, the heart can become a target of these misdirected immune responses. When the heart is affected, the resulting inflammation can compromise its structure and function, leading to a range of cardiovascular complications.
Rheumatic Fever and Subsequent Heart Damage
One of the conditions most historically linked to severe autoimmune damage to the heart follows an untreated infection with Group A Streptococcus, commonly known as strep throat. This initial infection can trigger an abnormal immune response called acute rheumatic fever. The subsequent damage to the heart arises from a biological phenomenon known as molecular mimicry.
Molecular mimicry occurs because proteins on the surface of the strep bacteria share structural similarities with certain proteins found in heart tissue, such as cardiac myosin and proteins within the heart valves. Antibodies designed to fight the bacterial M protein mistakenly cross-react with these self-antigens. This misidentification initiates a powerful inflammatory cascade directly against the heart’s structures.
The inflammation caused by this cross-reaction is known as carditis, and it most frequently targets the heart valves. Over time, repeated cycles of inflammation and repair lead to scarring, thickening, and stiffening of the valves, resulting in Rheumatic Heart Disease (RHD). RHD permanently impairs the valves’ ability to open fully or close tightly, often causing blood flow obstruction or leakage. While antibiotic use has made this disease rare in many developed countries, it remains a major global public health concern.
Chronic Systemic Diseases Targeting the Heart
Beyond post-infectious conditions, numerous chronic systemic autoimmune diseases include the heart as a potential target organ. Systemic Lupus Erythematosus (SLE), often simply called Lupus, is one such disorder known for its widespread inflammatory effects. Lupus can cause inflammation in any of the heart’s layers, including the fluid-filled sac, the muscle, and the inner lining.
Another major connective tissue disease that frequently affects the heart is Scleroderma, or Systemic Sclerosis. This condition is characterized by excessive collagen production, leading to hardening and fibrosis of various organs. When Scleroderma affects the heart, it often causes a primary myocardial disease marked by the replacement of healthy heart muscle with scar tissue.
This fibrosis impairs the heart’s ability to contract and relax, frequently resulting in heart failure and rhythm disturbances. Furthermore, both SLE and Scleroderma can accelerate the development of atherosclerosis, which is the hardening and narrowing of the arteries, and can cause inflammation in the smaller coronary blood vessels.
How Immune Attacks Damage Heart Structures
The body’s autoimmune aggression can be classified by which of the heart’s three main layers is affected, each resulting in a distinct pathology. When the immune system targets the pericardium, the thin sac surrounding the heart, the condition is called pericarditis. This inflammation often leads to a buildup of excess fluid in the sac, known as pericardial effusion, which can restrict the heart’s ability to fill with blood.
An attack on the myocardium, the thick muscular middle layer responsible for pumping blood, is termed myocarditis. Immune cells infiltrate the muscle tissue, causing direct damage to the heart cells and leading to a reduction in the heart’s pumping capacity. Chronic myocarditis frequently results in fibrosis (scarring of the muscle), which can lead to a dilated or weakened heart, known as cardiomyopathy.
The innermost layer of the heart, the endocardium, and its associated valves are also vulnerable, resulting in endocarditis or valvulitis. In diseases like Rheumatic Heart Disease and Lupus, the immune attack causes thickening and distortion of the valve leaflets. This structural damage prevents the valves from functioning correctly, resulting in either regurgitation, where blood leaks backward, or stenosis, where the valve opening narrows, forcing the heart to work harder. The scarring and inflammation across these structures can also disrupt the heart’s electrical conduction system, leading to arrhythmias.
Symptoms, Diagnosis, and General Management
Symptoms
The signs of autoimmune heart involvement can be varied, often mirroring symptoms of other cardiovascular issues. Common patient complaints include chest pain, which may worsen when lying down or taking a deep breath, suggesting pericarditis. Patients may also experience shortness of breath, fatigue, and swelling in the legs, indicating reduced heart function or developing heart failure. Palpitations may signal an electrical conduction issue caused by inflammation.
Diagnosis
Because symptoms are non-specific, diagnosis relies on a combination of methods. Diagnostic procedures typically include an electrocardiogram (ECG) to check for rhythm disturbances and an echocardiogram, which visualizes the heart’s structure, function, and valve integrity. Blood tests detect elevated inflammatory markers (such as C-reactive protein) and identify specific autoantibodies (such as anti-nuclear antibodies, or ANA) that characterize the underlying disease.
General Management
Treatment requires collaboration between cardiologists and rheumatologists, focusing on two main goals: suppressing the immune system and managing heart damage. The autoimmune attack is reduced using anti-inflammatory medications and immunosuppressive drugs, such as corticosteroids or disease-modifying anti-rheumatic drugs. For existing heart damage, treatment involves standard therapies for heart failure, including diuretics or blood pressure medications.