Myocarditis: Causes, Pathophysiology, Symptoms, Diagnosis and Treatment.

Myocardial Infarction (Heart Attack) or Myocarditis? Check out our new Alila Academy - AlilaAcademy.com - complete video courses with quizzes, PDFs, and downloadable images. Purchase a license to download a non-watermarked version of this video on AlilaMedicalMedia.com Join this channel to get access to member-only videos and other perks:    / @alilamedicalmedia   ©Alila Medical Media. All rights reserved. Voice by: Jacob Glass All images/videos by Alila Medical Media are for information purposes ONLY and are NOT intended to replace professional medical advice, diagnosis or treatment. Myocarditis is inflammation of the myocardium – the heart wall’s muscle layer responsible for its pumping action. Myocarditis is very difficult to diagnose because of its highly variable clinical presentation, which also often overlaps with other cardiovascular conditions. Symptoms range from mild palpitations, chest pain, to life-threatening heart failure, arrhythmias, and cardiogenic shock. The condition occurs most frequently in young adults. Myocarditis has many causes, both infectious and non-infectious. Among the infectious group, viral causes are most common, with numerous viruses involved. Non-infectious etiologies include autoimmune disorders and systemic diseases such as sarcoidosis, lupus, and exposure to certain drugs or toxins. An infectious myocarditis may also progress to autoimmune myocarditis at a later stage, after the infectious agent is cleared. A triphasic model has been proposed to describe the disease: phase 1: direct injury by the causative agent, phase 2: damage brought about by the innate and adaptive immune responses, and phase 3: resolution of the disease, or progression to a chronic state. In viral myocarditis, for example, virus-infected cells trigger an innate immune response that brings immune cells and inflammatory cytokines to the site of infection. While inflammation is a protective mechanism meant to fight the pathogen, it can damage the body’s own tissues if it fails to stop after the pathogen is cleared. This EXCESSIVE inflammatory response is more likely to occur in patients with genetic predispositions to inflammation. The progression from acute to chronic state often involves molecular MIMICRY, in which viral antigens resemble cardiac self-antigens, such as cardiac myosin, provoking the adaptive immune system to produce anti-heart antibodies. Chronic inflammation eventually leads to formation of scar tissues within the myocardium, disrupting cardiac electrical conduction, increasing the risk of arrhythmias and other abnormalities. Over time, the heart wall undergoes structural remodeling, becoming stiffer, thinner, and chronic dilated cardiomyopathy may result. Symptoms of myocarditis are non-specific and vary widely. Common signs include chest pain, shortness of breath and fever, but patients may also present with acute or chronic heart failure, dilated cardiomyopathy, ventricular arrhythmias, or cardiogenic shock. A common ECG finding is ST-segment elevation, which might cause the condition to be MISDIAGNOSED as myocardial infarction or pericarditis. In addition, respiratory and/or gastrointestinal symptoms may precede cardiovascular symptoms in many cases. Prognosis is also variable. While some patients recover spontaneously without permanent damage, others may progress to sudden cardiac arrest or chronic cardiomyopathy. Myocarditis must be suspected in younger patients with signs of myocardial infarction but without its conventional risk factors, especially in those with recent fever/infection, or connective tissue disease. Diagnostic tests include: Electrocardiogram; Blood tests for evidence of infection, inflammatory markers, and cardiac markers; Echocardiography, to assess myocardial damage, and to rule out structural heart disease; Coronary angiography or computed tomography angiography to rule out coronary artery disease; Cardiac MRI to detect inflammation and scarring; and the invasive Endomyocardial Biopsy (EMB). EMB remains the diagnostic gold standard as it allows histological and immunohistological assessment of cardiac myocyte damage and composition of immune cell infiltration, as well as detection of viral genomes with PCR. Autoimmune myocarditis is diagnosed when there is immunohistological evidence of myocarditis in EMB, but viral PCR is negative. Treatment is generally supportive. Heart failure and arrythmias are managed with standard guidelines. Mechanical circulatory support may be required for severe cases. Immunosuppression therapy may be considered in immune-mediated myocarditis with negative viral PCR.