Overview

Definition

Myocarditis is an inflammatory disease of the myocardium.

Epidemiology

• Incidence: approximately 10–22 cases per 100,000 people
• About 1%–5% of viral infections involve the myocardium.
• Affects more men than women
• More common in young adults

Etiology

• Idiopathic (50% of cases)
• Infectious organisms:
  • Viral (most common in North America and Europe)
  • Bacterial
  • Protozoal (most common in Africa, Asia, and South America)
  • Fungal
• Immune-mediated disorders:
  • Rheumatic fever Rheumatic fever Acute rheumatic fever (ARF) is an autoimmune inflammatory process that usually follows Streptococcal pharyngitis. Acute rheumatic fever usually occurs 2-4 weeks after an untreated infection and affects the heart, skin, joints, and nervous system. Rheumatic Fever
  • Allergic reactions
  • Transplant rejection
  • Kawasaki disease Kawasaki disease Kawasaki disease (KD), also known as mucocutaneous lymph node syndrome or infantile polyarteritis, is a medium-sized necrotizing febrile vasculitis that affects children < 5 years of age. Multiple systems are involved but the most serious is the predilection of the coronary arteries. Kawasaki Disease
  • Sarcoidosis Sarcoidosis Sarcoidosis is a multisystem inflammatory disease that causes noncaseating granulomas. The exact etiology is unknown. Sarcoidosis usually affects the lungs and thoracic lymph nodes, but it can also affect almost every system in the body, including the skin, heart, and eyes, most commonly. Sarcoidosis
  • Systemic lupus erythematosus Systemic lupus erythematosus Systemic lupus erythematosus (SLE) is a chronic autoimmune, inflammatory condition that causes immune-complex deposition in organs, resulting in systemic manifestations. Women, particularly those of African American descent, are more commonly affected. Systemic Lupus Erythematosus
  • Polymyositis Polymyositis Polymyositis (PM) is an autoimmune inflammatory myopathy caused by T cell-mediated muscle injury. The etiology of PM is unclear, but there are several genetic and environmental associations. Polymyositis is most common in middle-aged women and rarely affects children. Polymyositis
  • Dermatomyositis
  • Scleroderma Scleroderma Scleroderma (systemic sclerosis) is an autoimmune condition characterized by diffuse collagen deposition and fibrosis. The clinical presentation varies from limited skin involvement to diffuse involvement of internal organs. Scleroderma
  • Juvenile idiopathic arthritis Juvenile Idiopathic Arthritis Juvenile idiopathic arthritis (JIA), formerly known as juvenile rheumatoid arthritis, is a heterogeneous group of inflammatory diseases characterized by inflammation of 1 or more joints and is the most common pediatric rheumatic disease. Juvenile Idiopathic Arthritis
  • Vasculitis
• Exogenous agents
• Genetic predisposition:
  • Genetic defects in the structural proteins of myocytes
  • ↑ Susceptibility to myocyte damage
• Environmental causes:
  • Exposure to carbon monoxide
  • Heavy-metal toxicity
  • Black widow venom
• Drugs:
  • Doxorubicin
  • Cyclophosphamide
  • Cocaine
  • Amphetamines
  • Ethanol

Causes of infectious myocarditis

The following table summarizes the infectious causes of myocarditis. Keep in mind that this list is not exhaustive.

Pathophysiology

Inflammation due to various etiologies leads to enlargement of the heart and dilation of all chambers.

• Causes of myocyte injury:
  • Viral: direct viral toxicity, lymphocytic infiltration, and cytokines
  • Bacterial: direct invasion or bacterial toxins
  • Autoimmune: autoantibodies to myocyte components
  • Toxins: hypersensitivity or direct effects
• Myocardial inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and injury → myocardial necrosis
• Severe and prolonged damage → fibrosis → chamber remodeling → dilated cardiomyopathy Dilated Cardiomyopathy Dilated cardiomyopathy (DCM) is the most common type of non-ischemic cardiomyopathy and a common cause of heart failure (HF). The cause may be idiopathic, familial, or secondary to a variety of underlying conditions. The disease is characterized by the enlargement of 1 or both ventricles and reduced systolic function. Dilated Cardiomyopathy
• Consequences:
  • Heart failure
  • Cardiac arrhythmia
  • Extension to the pericardium → pericarditis Pericarditis Pericarditis is an inflammation of the pericardium, often with fluid accumulation. It can be caused by infection (often viral), myocardial infarction, drugs, malignancies, metabolic disorders, autoimmune disorders, or trauma. Acute, subacute, and chronic forms exist. Pericarditis

Clinical Presentation

The clinical presentation can vary based on the severity and temporal progression of symptoms. Most signs and symptoms are related to heart failure.

Classification

Myocarditis is classified based on temporal progression.

• Subclinical: absent or minimal symptoms
• Acute: heart failure develops in < 3 months.
• Chronic: heart failure develops in > 3 months.

Symptoms

• Fever
• Chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain
• Dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea
• Orthopnea
• Loss of appetite
• Abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
• Fatigue
• Decreased exercise tolerance

Physical exam

• Tachycardia
• Arrhythmia
• Peripheral edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema
• Hepatomegaly
• Pulmonary rales
• Jugular venous distention
• Murmur → may indicate chamber enlargement:
  • Mitral regurgitation Mitral regurgitation Mitral regurgitation (MR) is the backflow of blood from the left ventricle (LV) to the left atrium (LA) during systole. Mitral regurgitation may be acute (myocardial infarction) or chronic (myxomatous degeneration). Acute and decompensated chronic MR can lead to pulmonary venous congestion, resulting in symptoms of dyspnea, orthopnea, and fatigue. Mitral Regurgitation
  • Tricuspid regurgitation Tricuspid regurgitation Tricuspid regurgitation (TR) is a valvular defect that allows backflow of blood from the right ventricle to the right atrium during systole. Tricuspid regurgitation can develop through a number of cardiac conditions that cause dilation of the right ventricle and tricuspid annulus. A blowing holosystolic murmur is best heard at the left lower sternal border. Tricuspid Regurgitation
• S3 and S4 gallops
• Pericardial friction rub ( pericarditis Pericarditis Pericarditis is an inflammation of the pericardium, often with fluid accumulation. It can be caused by infection (often viral), myocardial infarction, drugs, malignancies, metabolic disorders, autoimmune disorders, or trauma. Acute, subacute, and chronic forms exist. Pericarditis)

Complications

• Cardiogenic shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock
• Myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction
• Dilated cardiomyopathy
• Cardiac arrhythmias
• Mural thrombus with systemic emboli
• Sudden cardiac arrest Cardiac arrest Cardiac arrest is the sudden, complete cessation of cardiac output with hemodynamic collapse. Patients present as pulseless, unresponsive, and apneic. Rhythms associated with cardiac arrest are ventricular fibrillation/tachycardia, asystole, or pulseless electrical activity. Cardiac Arrest

Management

General principles

Management for myocarditis is generally supportive, but often includes:

• Heart failure management
• Arrhythmia management
• Treating the underlying etiology (when possible)

Heart failure management

Medical therapy for heart failure:

• Diuretics
• ACE inhibitors
• Beta-adrenergic blockers
• Angiotensin II receptor blockers
• Aldosterone antagonists

For fulminant heart failure:

• Inotropic support
• Intraaortic balloon pump
• Left ventricular assist device
• Cardiac transplantation

Arrhythmia management

• Antiarrhythmic therapy
• Cardioversion
• Temporary or permanent pacing

Other considerations

• Anticoagulants Anticoagulants Anticoagulants are drugs that retard or interrupt the coagulation cascade. The primary classes of available anticoagulants include heparins, vitamin K-dependent antagonists (e.g., warfarin), direct thrombin inhibitors, and factor Xa inhibitors. Anticoagulants are indicated for:
  • Intracardiac thrombi
  • Evidence of systemic embolism
  • Atrial fibrillation Atrial fibrillation Atrial fibrillation (AF or Afib) is a supraventricular tachyarrhythmia and the most common kind of arrhythmia. It is caused by rapid, uncontrolled atrial contractions and uncoordinated ventricular responses. Atrial Fibrillation
• Avoidance of:
  • NSAIDs
  • Alcohol consumption
  • Exercise

Long term follow-up

Most patients will have a partial or full recovery. However, long-term follow-up and monitoring are recommended.

• Gradual resumption of physical activities
• Serial echocardiography monitoring
• Re-evaluation and titration of medications, as appropriate

Differential Diagnosis

• Pericarditis: an inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the outer lining of the heart resulting from infection, autoimmune disease, radiation, surgery, or myocardial infarction. Pericarditis clinically presents with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and pleuritic chest pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain that increases with lying supine, and pericardial rub on auscultation. An ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG) with diffuse ST-segment elevation and an echocardiogram showing pericardial effusion can confirm the diagnosis. Management is supportive.
• Myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction: ischemia of the myocardium due to partial or complete obstruction of the coronary arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries. Patients present with acute onset chest pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain. As in the case of myocarditis, heart failure can develop, which is usually accompanied by elevated troponins and typical ischemic ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG) changes (ST elevations or depressions). Wall-motion abnormalities can be diagnosed based on a transthoracic echo. Management is with antiplatelet medications, nitrates Nitrates Nitrates are a class of medications that cause systemic vasodilation (veins > arteries) by smooth muscle relaxation. Nitrates are primarily indicated for the treatment of angina, where preferential venodilation causes pooling of blood, decreased preload, and ultimately decreased myocardial O2 demand. Nitrates, beta blockers, and revascularization.
• Pericardial effusion Pericardial effusion Pericardial effusion is the accumulation of excess fluid in the pericardial space around the heart. The pericardium does not easily expand; thus, rapid fluid accumulation leads to increased pressure around the heart. The increase in pressure restricts cardiac filling, resulting in decreased cardiac output and cardiac tamponade. Pericardial Effusion and Cardiac Tamponade and tamponade: the presence of fluid in the pericardial sac, which can cause compression of the heart and lead to tamponade physiology. Tamponade physiology prevents the heart from filling and results in hemodynamic collapse. Beck’s triad of distended neck veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins, hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension, and muffled heart sounds Heart sounds Heart sounds are brief, transient sounds produced by valve opening and closure and by movement of blood in the heart. They are divided into systolic and diastolic sounds. In most cases, only the first (S1) and second (S2) heart sounds are heard. These are high-frequency sounds and arise from aortic and pulmonary valve closure (S1), as well as mitral and tricuspid valve closure (S2). Heart Sounds is often noted on physical exam. Diagnosis is confirmed using transthoracic echocardiography, and management involves drainage of the pericardium.
• Pulmonary embolism: obstruction of the pulmonary arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries, which is most often due to thrombus migration from the deep venous system. Signs and symptoms include pleuritic chest pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, dyspnea, tachypnea, and tachycardia. Severe cases of pulmonary embolism Pulmonary Embolism Pulmonary embolism (PE) is a potentially fatal condition that occurs as a result of intraluminal obstruction of the main pulmonary artery or its branches. The causative factors include thrombi, air, amniotic fluid, and fat. In PE, gas exchange is impaired due to the decreased return of deoxygenated blood to the lungs. Pulmonary Embolism can result in hemodynamic instability or cardiopulmonary arrest. A chest CT with angiography is the primary method of diagnosis. Management includes oxygenation, and anticoagulant and thrombolytic therapies for unstable patients.