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. Patients typically present with symptoms of HF such as shortness of breath, fatigue, weakness, and 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. Blood tests, 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), X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays, echocardiography, and other cardiac studies and procedures are typically done to obtain the diagnosis. Treatment includes medications used to reduce volume overload (e.g., diuretics) and manage HF (e.g., beta-blockers). Devices such as pacemakers and cardioverter-defibrillators may also be needed. In severe cases, a heart transplant is required. Complications include thromboembolic events and sudden cardiac death.

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Overview

Definition

Dilated cardiomyopathy (DCM) is a disease of the cardiac muscle associated with electrical and mechanical dysfunction causing impaired systolic function and featuring the dilatation of 1 or both ventricles.

Epidemiology

  • Most common type of non-ischemic cardiomyopathy
  • Annual incidence: 6 per 100,000
  • 10,000 deaths and 46,000 hospitalizations yearly in the United States
  • Affects men > women
  • Occurs in all ages, most common in those 20–60 years old
  • Most common indication for heart transplant

Etiology

  • Idiopathic in approximately 50% of cases 
  • Familial DCM:
    • Caused by a multitude of gene mutations
    • 20%–35% of cases initially diagnosed as idiopathic are later found to have a familial component after additional family screening.
    • Typical inheritance pattern is autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance; however, all inheritance patterns have occurred.
  • Ischemic heart disease Ischemic heart disease Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease/coronary artery disease (CAD)
  • Untreated hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension 
  • Long-standing valvular disease (e.g., mitral or aortic regurgitation Aortic regurgitation Aortic regurgitation (AR) is a cardiac condition characterized by the backflow of blood from the aorta to the left ventricle during diastole. Aortic regurgitation is associated with an abnormal aortic valve and/or aortic root stemming from multiple causes, commonly rheumatic heart disease as well as congenital and degenerative valvular disorders. Aortic Regurgitation)
  • Arrhythmias (particularly those that cause sustained tachycardia, e.g., 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)
  • Infections:
    • Viral infections causing myocarditis Myocarditis Myocarditis is an inflammatory disease of the myocardium, which may occur alone or in association with a systemic process. There are numerous etiologies of myocarditis, but all lead to inflammation and myocyte injury, most often leading to signs and symptoms of heart failure. Myocarditis (e.g., coxsackievirus Coxsackievirus Coxsackievirus is a member of a family of viruses called Picornaviridae and the genus Enterovirus. Coxsackieviruses are single-stranded, positive-sense RNA viruses, and are divided into coxsackie group A and B viruses. Both groups of viruses cause upper respiratory infections, rashes, aseptic meningitis, or encephalitis. Coxsackievirus, influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza, or HIV)
    • Chagas disease Chagas disease Chagas disease is an infection caused by the American trypanosome Trypanosoma cruzi. This parasitic protozoan is transmitted in the feces of reduviid bugs in South and Central America. Acute infection may present with inflammation at the inoculation site (chagoma), fever, and lymphadenopathy. Untreated, chronic infection can progress to severe complications. Trypanosoma cruzi/Chagas disease (protozoan infection due to Trypanosoma cruzi Trypanosoma cruzi Chagas disease is an infection caused by the American trypanosome Trypanosoma cruzi. This parasitic protozoan is transmitted in the feces of reduviid bugs in South and Central America. Acute infection may present with inflammation at the inoculation site (chagoma), fever, and lymphadenopathy. Untreated, chronic infection can progress to severe complications. Trypanosoma cruzi/Chagas disease)
  • Endocrine disorders (e.g., hyperthyroidism Hyperthyroidism Thyrotoxicosis refers to the classic physiologic manifestations of excess thyroid hormones and is not synonymous with hyperthyroidism, which is caused by sustained overproduction and release of T3 and/or T4. Graves' disease is the most common cause of primary hyperthyroidism, followed by toxic multinodular goiter and toxic adenoma. Thyrotoxicosis and Hyperthyroidism or diabetes)
  • Autoimmune or inflammatory conditions (e.g., lupus or 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)
  • Neuromuscular genetic conditions (e.g., Duchenne muscular dystrophy Duchenne muscular dystrophy Duchenne muscular dystrophy (DMD) is an X-linked recessive genetic disorder that is caused by a mutation in the DMD gene. The mutation leads to the production of abnormal dystrophin, resulting in muscle-fiber destruction and replacement with fatty or fibrous tissue. Duchenne Muscular Dystrophy or Friedreich’s ataxia)
  • Deposition diseases (e.g., hemochromatosis or amyloidosis Amyloidosis Amyloidosis is a disease caused by abnormal extracellular tissue deposition of fibrils composed of various misfolded low-molecular-weight protein subunits. These proteins are frequently byproducts of other pathological processes (e.g., multiple myeloma). Amyloidosis)
  • Medications that cause cardiotoxicity:
    • Chemotherapeutic medications (classically an anthracycline, e.g., doxorubicin, or a monoclonal antibody, e.g., trastuzumab)
    • Antiretrovirals (most classically azidothymidine; also known as zidovudine)
    • Hydroxychloroquine 
  • Radiation treatment (particularly to the chest)
  • Peripartum cardiomyopathy:
    • Secondary to hemodynamic changes associated with pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-hCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care
    • Occurs in the last month of pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-hCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care or the 1st months after giving birth 
  • Toxins:
    • Alcohol abuse
    • Cocaine and other illicit drug use
    • Exposure to heavy metals (e.g., cobalt, arsenic, mercury, or lead)
  • Nutritional deficiencies (e.g., thiamine, selenium, or carnitine)

Pathophysiology

  • Ventricular dilation caused by:
    • Left ventricle (LV) failure
    • Primary injury of heart muscle 
  • Ventricular dilatation leads to:
    • Thinning of heart muscle wall 
    • Weakening and enlargement of heart
    • Systolic failure:
      • Cardiac muscle does not contract efficiently when deformed.
      • Cardiac output decreases.
    • Diastolic failure: valvular insufficiency due to distortion of cardiac architecture 
    • Heart failure (HF)

Clinical Presentation

Symptoms may develop and progress slowly over time, or develop abruptly. Symptoms are similar to those seen with HF.

Symptoms

  • 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/shortness of breath (especially with exertion)
  • Orthopnea (shortness of breath when lying down)
  • Edema of lower extremities and abdomen
  • Weight gain
  • Dizziness
  • Syncopal episodes
  • 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
  • Palpitations
  • Fatigue 
  • Weakness

Physical exam findings

  • Cardiac:
    • Systolic heart murmur (from mitral or aortic regurgitation Aortic regurgitation Aortic regurgitation (AR) is a cardiac condition characterized by the backflow of blood from the aorta to the left ventricle during diastole. Aortic regurgitation is associated with an abnormal aortic valve and/or aortic root stemming from multiple causes, commonly rheumatic heart disease as well as congenital and degenerative valvular disorders. Aortic Regurgitation)
    • S3 gallop
  • Abdominal: ascites Ascites Ascites is the pathologic accumulation of fluid within the peritoneal cavity that occurs due to an osmotic and/or hydrostatic pressure imbalance secondary to portal hypertension (cirrhosis, heart failure) or non-portal hypertension (hypoalbuminemia, malignancy, infection). Ascites
  • Pulmonary:
    • Rales or crackles over lung fields (secondary to pulmonary edema Pulmonary edema Pulmonary edema is a condition caused by excess fluid within the lung parenchyma and alveoli as a consequence of a disease process. Based on etiology, pulmonary edema is classified as cardiogenic or noncardiogenic. Patients may present with progressive dyspnea, orthopnea, cough, or respiratory failure. Pulmonary Edema)
    • Respiratory distress
    • Low oxygen saturation
  • Vascular: jugular venous distention
  • Extremity:
    • Pitting 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 in lower extremities
    • Signs of venous stasis with discoloration in lower extremities

Diagnosis

Diagnosis is primarily through history and physical examination, laboratory examination, 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), and imaging (confirmatory or to exclude other etiologies).

Laboratory studies

  • BNP: marker for heart failure (↑)
  • Troponin: marker for MI MI 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 (↑)
  • CK-MB: another marker for MI MI 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 (↑ in 1st 24 hours, then returns to normal by 48–72 hours)
  • 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): may show sinus tachycardia, left atrial enlargement, ventricular arrhythmias, or 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

Imaging

  • Chest X-ray: may show enlarged heart and effusions (accumulation of fluid)
  • Echocardiography:
    • Assess: 
      • Cardiac size
      • Structure
      • Function
      • Differentiates other forms of cardiomyopathy
    • Shows:
      • Enlarged ventricular diameter (dilation)
      • Normal or decreased wall thickness
      • Decreased inward endocardial systolic motion
      • Reduced left ventricular ejection fraction (LVEF)
    • Evidence of dilation of 1 or both ventricles and reduced systolic dysfunction necessary for diagnosis of dilated cardiomyopathy
  • Cardiac MRI: helps determine extent of myocardial damage and fibrosis
  • Coronary angiography: 
    • Helps rule out CAD
    • May show dilated, hypokinetic LV, normal 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, and some degree of 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
  • Endomyocardial biopsy with histologic examination: 
    • Done in select cases: 
      • Uncertain cause 
      • New-onset HF with associated hemodynamic compromise, ventricular arrhythmias, Mobitz type II atrioventricular (AV) block, 3rd-degree AV block AV block Atrioventricular (AV) block is a bradyarrhythmia caused by delay, or interruption, in the electrical conduction between the atria and the ventricles. Atrioventricular block occurs due to either anatomic or functional impairment, and is classified into 3 types. Atrioventricular Block, or HF refractory to typical treatments
  • Obtain comprehensive family history and genetic testing if familial DCM suspected.

Management

Treatment

  • Medications:
    • Angiotensin-converting enzyme inhibitors/angiotensin receptor blockers: improve systolic function
    • Beta-blockers: increase ejection fraction
    • Diuretics: treat volume overload
    • Vasodilators
  • Oral anticoagulation (vitamin K antagonists, e.g., warfarin) if LVEF < 35%
  • Device therapies (e.g., pacemaker or implanted cardioverter-defibrillator) if:
    • LVEF < 35%
    • Arrhythmias or other conduction disorders
    • LVEF > 35% with family history of sudden cardiac death or gene mutations (e.g., LMNA) associated with a high risk for sudden cardiac death
    • Syndromic diseases (e.g., muscular dystrophy)
  • Heart transplant warranted in severe cases

Complications

  • Arrhythmias
  • Thromboembolic events (e.g., 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 or cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke)
  • Sudden cardiac death

Prognosis

Prognosis is generally poor for individuals with this condition. 

Differential Diagnosis

  • Restrictive cardiomyopathy Restrictive Cardiomyopathy Restrictive cardiomyopathy (RCM) is a fairly uncommon condition characterized by progressive stiffening of the cardiac muscle, which causes impaired relaxation and refilling of the heart during diastole, resulting in diastolic dysfunction and eventual heart failure. Restrictive Cardiomyopathy: a condition secondary to scarring and/or infiltration of the heart muscle ( amyloidosis Amyloidosis Amyloidosis is a disease caused by abnormal extracellular tissue deposition of fibrils composed of various misfolded low-molecular-weight protein subunits. These proteins are frequently byproducts of other pathological processes (e.g., multiple myeloma). Amyloidosis most common cause) characterized by a stiffening of the ventricles resulting in diastolic dysfunction and eventual HF. Presentation includes signs and symptoms of HF. Similar studies as DCM are used to help determine the diagnosis. Treatment is also similar, including medications and implantable devices such as pacemakers and cardioverter-defibrillators. A heart transplant may be needed when symptoms become severe and no longer responsive to treatments. Prognosis and survival are worse than with DCM. 
  • Hypertrophic cardiomyopathy Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy (HCM) is the most commonly inherited cardiomyopathy, which is characterized by an asymmetric increase in thickness (hypertrophy) of the left ventricular wall, diastolic dysfunction, and often left ventricular outflow tract obstruction. Hypertrophic Cardiomyopathy (HCM): Gene mutations affect the contractile components of the heart (sarcomeres) resulting in LV asymmetrical wall thickening, diastolic dysfunction, and LV outflow tract obstruction. Patients may be asymptomatic or suffer sudden cardiac death as the 1st sign of disease. Symptomatic individuals have dyspnea on exertion, chest pain, presyncope, or syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope. Diagnosis is made via 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), echocardiogram, stress test, and cardiac MRI. Treatment involves beta-blockers as 1st-line therapy with additional management depending on the presence of arrhythmias and LV outflow tract obstruction. 
  • Takotsubo cardiomyopathy Takotsubo Cardiomyopathy Takotsubo cardiomyopathy (also known as stress cardiomyopathy, or "broken heart syndrome") is a type of non-ischemic cardiomyopathy in which there is transient regional systolic dysfunction of the left ventricle. Patients present with symptoms of acute coronary syndrome, including chest pressure and shortness of breath. Takotsubo Cardiomyopathy: a type of non-ischemic cardiomyopathy occurring due to extreme psychological or physical stress; also known as stress-induced cardiomyopathy or “broken heart syndrome.” Takotsubo cardiomyopathy Takotsubo Cardiomyopathy Takotsubo cardiomyopathy (also known as stress cardiomyopathy, or "broken heart syndrome") is a type of non-ischemic cardiomyopathy in which there is transient regional systolic dysfunction of the left ventricle. Patients present with symptoms of acute coronary syndrome, including chest pressure and shortness of breath. Takotsubo Cardiomyopathy is characterized by transient, regional systolic dysfunction of the LV. Patients present with symptoms of acute coronary syndrome, including chest pressure and shortness of breath, and 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) may show ST-segment elevation. Coronary angiography can help to differentiate this condition from MI MI 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. An echocardiogram can confirm the diagnosis by demonstrating characteristic apical wall motion abnormalities. Treatment includes the removal of inciting stressors and beta-blockers.

References

  1. (2021). Dilated Cardiomyopathy Cardiomyopathy Cardiomyopathy refers to a group of myocardial diseases associated with structural changes of the heart muscles (myocardium) and impaired systolic and/or diastolic function in the absence of other heart disorders (coronary artery disease, hypertension, valvular disease, and congenital heart disease). Overview of Cardiomyopathies. Medline Plus. Retrieved February 3, 2021, from https://medlineplus.gov/ency/article/000168.htm
  2. Schaufelberger M. (2019). Cardiomyopathy Cardiomyopathy Cardiomyopathy refers to a group of myocardial diseases associated with structural changes of the heart muscles (myocardium) and impaired systolic and/or diastolic function in the absence of other heart disorders (coronary artery disease, hypertension, valvular disease, and congenital heart disease). Overview of Cardiomyopathies and pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-hCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care. Heart. 105:1543-1551. Retrieved February 3, 2021, from https://heart.bmj.com/content/105/20/1543.info
  3. Weigner, M. & Morgan, J. P. (2019). Causes of dilated cardiomyopathy. UpToDate. Retrieved February 4, 2021, from https://www.uptodate.com/contents/causes-of-dilated-cardiomyopathy
  4. Cooper, L.T. (2019). Definition and classification of the cardiomyopathies. UpToDate. Retrieved February 4, 2021, from https://www.uptodate.com/contents/definition-and-classification-of-the-cardiomyopathies
  5. Hershberger, R.E. (2020). Familial dilated cardiomyopathy: Prevalence, diagnosis, and treatment. UpToDate. Retrieved February 4, 2021, from https://www.uptodate.com/contents/familial-dilated-cardiomyopathy-prevalence-diagnosis-and-treatment

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