Myocardial Scar
Myocardial scar is an area of damaged or replaced tissue in the heart muscle (myocardium), most often the result of a prior heart attack, but also caused by inflammation, infection, infiltrative diseases, or certain genetic conditions. Scarred tissue does not contract normally and can affect heart function and electrical signaling. Cardiac MRI is the most sensitive imaging tool for identifying and characterizing myocardial scar, providing important information about cause, severity, and risk of complications such as arrhythmias.
What is it?
The heart muscle (myocardium) is responsible for the rhythmic contraction that pumps blood throughout the body. When part of the heart muscle is damaged—most often by a lack of blood supply during a heart attack, but also by inflammation, infection, or other conditions—the affected tissue may be permanently replaced by scar (fibrous) tissue. Myocardial scar is the term used to describe these areas of damaged or replaced tissue. Unlike healthy muscle, scarred tissue does not contract and may also disrupt the normal electrical signals that coordinate the heartbeat.
There are many possible causes of myocardial scar. Prior heart attack (myocardial infarction) is by far the most common cause and typically produces scar in a pattern that follows the territory of a coronary artery. Inflammatory conditions—including viral or autoimmune myocarditis—can leave patchy scar after the inflammation resolves. Infiltrative and storage diseases such as cardiac sarcoidosis and amyloidosis produce characteristic patterns of scar and tissue change. Genetic cardiomyopathies, such as hypertrophic cardiomyopathy and certain forms of arrhythmogenic cardiomyopathy, are also associated with characteristic scar patterns. Other contributors include long-standing high blood pressure, valve disease, congenital heart disease, prior radiation, cardiotoxic medications (such as some chemotherapies), and infections such as Chagas disease in endemic regions. Scar can also develop at sites of prior cardiac procedures, surgery, or ablation.
The location, size, and pattern of myocardial scar provide important clues to its cause and to the patient’s risk. Ischemic scar (related to coronary artery disease) typically begins at the inner layer of the heart muscle (the subendocardium) and may extend through the wall, following the distribution of a specific coronary artery. Non-ischemic scar—from causes such as myocarditis, sarcoidosis, or genetic cardiomyopathies—often appears in different patterns, such as mid-wall or beneath the outer surface of the heart, and may not match any single coronary artery distribution. These patterns help guide further diagnostic evaluation and management.
Many small or limited areas of myocardial scar cause no symptoms and are discovered incidentally on cardiac imaging. When symptoms occur, they depend on how much heart muscle is scarred, where the scar is located, and whether it is affecting heart function or electrical activity. Possible symptoms include shortness of breath, fatigue, reduced exercise tolerance, palpitations, lightheadedness, fainting, chest discomfort, or signs of heart failure (such as leg swelling and difficulty lying flat). Patients with larger or more extensive scar are at higher risk of heart failure and arrhythmias, including potentially serious rhythms such as ventricular tachycardia or fibrillation.
Cardiac MRI is the most sensitive and specific imaging test for identifying and characterizing myocardial scar. With a contrast agent (gadolinium), MRI can show areas of “late gadolinium enhancement” that correspond to scar, providing detailed information about location, extent, and pattern. Cardiac MRI is also highly accurate at measuring heart chamber sizes and function. Echocardiography is widely used to assess overall heart structure and function and can show regional contraction abnormalities suggestive of scarred muscle, particularly with techniques such as strain imaging. Nuclear imaging (such as PET or SPECT) provides functional and metabolic information and may identify areas of viable versus scarred myocardium. ECG can suggest prior infarction or other causes of scar. Blood biomarkers, electrophysiologic studies, and, in selected cases, endomyocardial biopsy can add further information.
Important to Know
Management of myocardial scar focuses on treating the underlying cause, optimizing heart function, reducing the risk of further damage, and preventing complications such as arrhythmias and sudden cardiac death. The intensity of treatment is individualized and depends on the size and cause of scar, the patient’s symptoms, and overall cardiovascular risk.
For ischemic scar related to coronary artery disease, treatment includes statins and other lipid-lowering medications, antiplatelet therapy, blood pressure and diabetes control, beta-blockers, ACE inhibitors or ARBs, and other heart failure or anti-anginal medications as appropriate. Lifestyle measures—not smoking, regular physical activity (with appropriate cardiac rehabilitation), heart-healthy diet, weight management, stress reduction, good sleep, and treatment of sleep apnea—are foundational. Revascularization with PCI or CABG may be considered for ongoing ischemia or high-risk anatomy.
Non-ischemic causes of scar require treatment directed at the underlying condition. Myocarditis often involves supportive care and treatment of any underlying cause; sarcoidosis may require corticosteroids or other immunosuppressive therapy; amyloidosis has specific therapies depending on subtype; genetic cardiomyopathies are managed by specialized programs with a focus on monitoring, family screening, and arrhythmia prevention. Heart failure related to scar is treated with standard guideline-directed medical therapy.
Arrhythmia prevention is an important consideration. Patients with significant scar and reduced heart function—or with specific high-risk scar patterns—may benefit from implantable cardioverter-defibrillators (ICDs) to prevent sudden cardiac death. Catheter ablation may be considered to treat scar-related ventricular tachycardia. Pacemakers and cardiac resynchronization therapy may be helpful in selected patients.
Care is typically coordinated by primary care clinicians and cardiologists, with input from heart failure specialists, electrophysiologists, interventional cardiologists, cardiothoracic surgeons, imaging cardiologists, and others. In familial conditions, genetic counseling and screening of relatives may be appropriate.
Red flag symptoms include severe or worsening shortness of breath, chest pain, fainting, sustained palpitations or rapid heart rate, severe leg swelling, fatigue out of proportion to activity, or signs of stroke or shock. These warrant prompt or urgent medical evaluation, as they may indicate progression of heart failure, arrhythmia, or another serious complication.