Dilated cardiomyopathy (DCM) is a condition in which the heart becomes enlarged and cannot pump blood effectively. [3] Symptoms vary from none to feeling tired, leg swelling, and shortness of breath. [2] It may also result in chest pain or fainting. [2] Complications can include heart failure, heart valve disease, or an irregular heartbeat. [3] [4]
Causes include genetics, alcohol, cocaine, certain toxins, complications of pregnancy, and certain infections. [8] [9] Coronary artery disease and high blood pressure may play a role, but are not the primary cause. [5] [8] In many cases the cause remains unclear. [8] It is a type of cardiomyopathy, a group of diseases that primarily affects the heart muscle. [3] The diagnosis may be supported by an electrocardiogram, chest X-ray, or echocardiogram. [9]
In those with heart failure, treatment may include medications in the ACE inhibitor, beta blocker, and diuretic families. [9] A low salt diet may also be helpful. [5] In those with certain types of irregular heartbeat, blood thinners or an implantable cardioverter defibrillator may be recommended. Cardiac resynchronization therapy (CRT) may be necessary. [9] If other measures are not effective a heart transplant may be an option in some. [9]
About 1 per 2,500 people is affected. [9] It occurs more frequently in men than women. [10] Onset is most often in middle age. [5] Five-year survival rate is about 50%. [9] It can also occur in children and is the most common type of cardiomyopathy in this age group. [9]
Dilated cardiomyopathy develops insidiously, and may not initially cause symptoms significant enough to impact on quality of life. [11] [12] Nevertheless, many people experience significant symptoms. These might include: [13]
A person who has dilated cardiomyopathy may have an enlarged heart, with pulmonary edema and an elevated jugular venous pressure and a low pulse pressure. Signs of mitral and tricuspid regurgitation may be present. [12]
Although in many cases no cause is apparent, dilated cardiomyopathy is probably the result of damage to the myocardium produced by a variety of toxic, metabolic, or infectious agents. In many cases the cause remains unclear. It may be due to fibrous change of the myocardium from a previous myocardial infarction. Or, it may be the late sequelae of acute viral myocarditis, such as with Coxsackie B virus and other enteroviruses [14] possibly mediated through an immunologic mechanism. [15] Specific autoantibodies are detectable in some cases. [16]
Other causes include:
Recent studies have shown that those subjects with an extremely high occurrence (several thousands a day) of premature ventricular contractions (extrasystole) can develop dilated cardiomyopathy. In these cases, if the extrasystole are reduced or removed (for example, via ablation therapy) the cardiomyopathy usually regresses. [20] [21]
Genetic associations with dilated cardiomyopathy | |||
---|---|---|---|
Type | OMIM | Gene | Locus |
CMD1A | 115200 | LMNA | 1q21 |
CMD1B | 600884 | unknown (TMOD1 candidate) | 9q13 |
CMD1C | 601493 | LDB3 | 10q22-q23 |
CMD1D | 601494 | TNNT2 | 1q32 |
CMD1E | 601154 | SCN5A | 3p |
CMD1F | 602067 | 6q23 | |
CMD1G | 604145 | TTN | 2q31 |
CMD1H | 604288 | 2q14-q22 | |
CMD1I | 604765 | DES | |
CMD1K | 605582 | 6q12-q16 | |
CMD1L | 606685 | SGCD | 5q33 |
CMD1M | 607482 | CSRP3 | 11p15.1 |
CMD1N | 607487 | TCAP | 17q12 |
CMD1O | 608569 | ABCC9 | 12p12.1 |
CMD1P | 609909 | PLN | 6q22.1 |
CMD1Q | 609915 | 7q22.3-q31.1 | |
CMD1R | ACTC | 15q14 | |
CMD1S | MYH7 | 14q12 | |
CMD1T | TMPO | 12q22 | |
CMD1U | PSEN1 | 14q24.3 | |
CMD1V | PSEN2 | 1q31-q42 | |
CMD1W | 611407 | VCL | 10q22-q23 |
CMD1X | FCMD | 9q31 | |
CMD1Y | 611878 | TPM1 | 15q22.1 |
CMD1Z | 611879 | TNNC1 | 3p21.3-p14.3 |
CMD1AA | 612158 | ACTN2 | 1q42-q43 |
CMD2A | 611880 | TNNI3 | 19q13.4 |
CMD3A | 300069 | TAZ | Xq28 |
CMD3B | 302045 | DMD | Xp21.2 |
ALPK3 | 15q25.3 |
About 25–35% of affected individuals have familial forms of the disease, [14] with most mutations affecting genes encoding cytoskeletal proteins, [14] while some affect other proteins involved in contraction. [22] The disease is genetically heterogeneous, but the most common form of its transmission is an autosomal dominant pattern. [14] Autosomal recessive (as found, for example, in Alström syndrome [14] ), X-linked (as in Duchenne muscular dystrophy), and mitochondrial inheritance of the disease is also found. [23] Some relatives of those affected by dilated cardiomyopathy have preclinical, asymptomatic heart-muscle changes. [24]
Other cytoskeletal proteins involved in DCM include α-cardiac actin, desmin, and the nuclear lamins A and C. [14] Mitochondrial deletions and mutations presumably cause DCM by altering myocardial ATP generation. [14]
Kayvanpour et al. performed 2016 a meta-analysis with the largest dataset available on genotype-phenotype associations in DCM and mutations in lamin (LMNA), phospholamban (PLN), RNA Binding Motif Protein 20 (RBM20), Cardiac Myosin Binding Protein C (MYBPC3), Myosin Heavy Chain 7 (MYH7), Cardiac Troponin T 2 (TNNT2), and Cardiac Troponin I (TNNI3). They also reviewed recent studies investigating genotype-phenotype associations in DCM patients with titin (TTN) mutations. LMNA and PLN mutation carriers showed a high prevalence of cardiac transplantation and ventricular arrhythmia. Dysrhythmias and sudden cardiac death (SCD) was shown to occur even before the manifestation of DCM and heart failure symptoms in LMNA mutation carriers. [25]
The progression of heart failure is associated with left ventricular remodeling, which manifests as gradual increases in left ventricular end-diastolic and end-systolic volumes, wall thinning, and a change in chamber geometry to a more spherical, less elongated shape. This process is usually associated with a continuous decline in ejection fraction. The concept of cardiac remodeling was initially developed to describe changes that occur in the days and months following myocardial infarction. [26]
As DCM progresses, two compensatory mechanisms are activated in response to impaired myocyte contractility and reduced stroke volume: [12]
These responses initially compensate for decreased cardiac output and maintain those with DCM as asymptomatic. Eventually, however, these mechanisms become detrimental, intravascular volume becomes too great, and progressive dilatation leads to heart failure symptoms.[ citation needed ]
Cardiac dilatation is a transversely isotropic, irreversible process resulting from excess strains on the myocardium. [27] A computation model of volumetric, isotropic, and cardiac wall growth predicts the relationship between cardiac strains (e.g. volume overload after myocardial infarction) and dilation using the following governing equations:[ citation needed ]
where is elastic volume stretch that is reversible and is irreversible, isotropic volume growth described by:[ citation needed ]
where is a vector, which points along a cardiomyocyte's long axis and is the cardiomyocyte stretch due to growth. The total cardiomyocyte growth is given by:
The above model reveals a gradual dilation of the myocardium, especially the ventricular myocardium, to support the blood volume overload in the chambers. Dilation manifests itself in an increase in total cardiac mass and cardiac diameter. Cardiomyocytes reach their maximum length of 150 m in the endocardium and 130 m in the epicardium by the addition of sarcomeres. [27] Due to the increase in diameter, the dilated heart appears spherical in shape, as opposed the elliptical shape of a healthy human heart. In addition, the ventricular walls maintain the same thickness, characteristic of pathophysiological cardiac dilation.[ citation needed ]
As the ventricles enlarge, both the mitral and tricuspid valves may lose their ability to come together properly. This loss of coaptation may lead to mitral and tricuspid regurgitation. As a result, those with DCM are at increased risk of atrial fibrillation. Furthermore, stroke volume is decreased and a greater volume load is placed on the ventricle, thus increasing heart failure symptoms. [12]
Generalized enlargement of the heart is seen upon normal chest X-ray. Pleural effusion may also be noticed, which is due to pulmonary venous hypertension. [28]
The electrocardiogram often shows sinus tachycardia or atrial fibrillation, ventricular arrhythmias, left atrial enlargement, and sometimes intraventricular conduction defects and low voltage. When left bundle-branch block (LBBB) is accompanied by right axis deviation (RAD), the rare combination is considered to be highly suggestive of dilated or congestive cardiomyopathy. [29] [30] Echocardiogram shows left ventricular dilatation with normal or thinned walls and reduced ejection fraction. Cardiac catheterization and coronary angiography are often performed to exclude ischemic heart disease. [28]
Genetic testing can be important, since one study has shown that gene mutations in the TTN gene (which codes for a protein called titin) are responsible for "approximately 25% of familial cases of idiopathic dilated cardiomyopathy and 18% of sporadic cases." [31] The results of the genetic testing can help the doctors and patients understand the underlying cause of the dilated cardiomyopathy. Genetic test results can also help guide decisions on whether a patient's relatives should undergo genetic testing (to see if they have the same genetic mutation) and cardiac testing to screen for early findings of dilated cardiomyopathy. [28]
Cardiac magnetic resonance imaging (cardiac MRI) may also provide helpful diagnostic information in patients with dilated cardiomyopathy. [32]
Drug therapy can slow down progression and in some cases even improve the heart condition. Standard therapy may include salt restriction, ACE inhibitors, diuretics, and beta blockers. [12] Anticoagulants may also be used for antithrombotic therapy. There is some evidence for the benefits of coenzyme Q10 in treating heart failure. [33] [34] [35]
Artificial pacemakers may be used in patients with intraventricular conduction delay, and implantable cardioverter-defibrillators in those at risk of arrhythmia. These forms of treatment have been shown to prevent sudden cardiac death, improve symptoms, and reduce hospitalization in patients with systolic heart failure. [36] In addition, an implantable cardioverter-defibrillator should be considered as a therapeutic option for the primary prevention of sudden cardiac death in patients with a confirmed LMNA mutation responsible for dilated cardiomyopathy disease phenotype and clinical risk factors. [37] A novel risk score calculator has been developed that allows calculation of risk of sustained ventricular arrhythmia in the next 5 years in patients with DCM. [38] https://www.ikard.pl/SVA/
In patients with advanced disease who are refractory to medical therapy, heart transplantation may be considered. For these people, 1-year survival approaches 90% and over 50% survive greater than 20 years. [36]
Although the disease is more common in African-Americans than in Caucasians, [39] it may occur in any patient population.
Therapies that support reverse remodeling have been investigated, and this may suggests a new approach to the prognosis of cardiomyopathies (see ventricular remodeling). [26] [40]
In some types of animals, both a hereditary and acquired version of dilated cardiomyopathy has been documented.[ citation needed ]
Dilated cardiomyopathy is a heritable disease in some dog breeds, including the Boxer, Dobermann, Great Dane, Irish Wolfhound, and St Bernard. [41] Treatment is based on medication, including ACE inhibitors, loop diuretics, and phosphodiesterase inhibitors.[ citation needed ]
An acquired variation of dilated cardiomyopathy describing a link between certain diets was discovered in 2019 by researchers at University of California, Davis School of Veterinary Medicine who published a report on the development of dilated cardiomyopathy in dog breeds lacking the genetic predisposition, particularly in Golden Retrievers. [42] The diets associated with DCM were described as "BEG" (boutique, exotic-ingredient, and/or grain-free) dog foods, [43] as well as legume-rich diets. [44] For treating diet-related DCM, food changes, taurine and carnitine supplementation may be indicated even if the dog does not have a documented taurine or carnitine deficiency although the cost of carnitine supplementation may be viewed as prohibitive by some [45]
Dilated cardiomyopathy is also a disease affecting some cat breeds, including the Oriental Shorthair, Burmese, Persian, and Abyssinian. In cats, taurine deficiency is the most common cause of dilated cardiomyopathy. [46] As opposed to these hereditary forms, non-hereditary DCM used to be common in the overall cat population before the addition of taurine to commercial cat food.[ citation needed ]
There is also a high incidence of heritable dilated cardiomyopathy in captive golden hamsters (Mesocricetus auratus), due in no small part to their being highly inbred. The incidence is high enough that several strains of Golden Hamster have been developed to serve as animal models in clinical testing for human forms of the disease. [47]
Cardiology is the study of the heart. Cardiology is a branch of medicine that deals with disorders of the heart and the cardiovascular system. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease, and electrophysiology. Physicians who specialize in this field of medicine are called cardiologists, a specialty of internal medicine. Pediatric cardiologists are pediatricians who specialize in cardiology. Physicians who specialize in cardiac surgery are called cardiothoracic surgeons or cardiac surgeons, a specialty of general surgery.
Cardiomyopathy is a group of primary diseases of the heart muscle. Early on there may be few or no symptoms. As the disease worsens, shortness of breath, feeling tired, and swelling of the legs may occur, due to the onset of heart failure. An irregular heart beat and fainting may occur. Those affected are at an increased risk of sudden cardiac death.
Cardiac arrest, also known as sudden cardiac arrest, is when the heart suddenly and unexpectedly stops beating. As a result, blood cannot properly circulate around the body and there is diminished blood flow to the brain and other organs. When the brain does not receive enough blood, this can cause a person to lose consciousness. Coma and persistent vegetative state may result from cardiac arrest. Cardiac arrest is also identified by a lack of central pulses and abnormal or absent breathing.
Ventricular fibrillation is an abnormal heart rhythm in which the ventricles of the heart quiver. It is due to disorganized electrical activity. Ventricular fibrillation results in cardiac arrest with loss of consciousness and no pulse. This is followed by sudden cardiac death in the absence of treatment. Ventricular fibrillation is initially found in about 10% of people with cardiac arrest.
A premature ventricular contraction (PVC) is a common event where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the sinoatrial node. PVCs may cause no symptoms or may be perceived as a "skipped beat" or felt as palpitations in the chest. PVCs do not usually pose any danger.
Palpitations are perceived abnormalities of the heartbeat characterized by awareness of cardiac muscle contractions in the chest, which is further characterized by the hard, fast and/or irregular beatings of the heart.
Myocarditis, also known as inflammatory cardiomyopathy, is an acquired cardiomyopathy due to inflammation of the heart muscle. Symptoms can include shortness of breath, chest pain, decreased ability to exercise, and an irregular heartbeat. The duration of problems can vary from hours to months. Complications may include heart failure due to dilated cardiomyopathy or cardiac arrest.
An implantable cardioverter-defibrillator (ICD) or automated implantable cardioverter defibrillator (AICD) is a device implantable inside the body, able to perform defibrillation, and depending on the type, cardioversion and pacing of the heart. The ICD is the first-line treatment and prophylactic therapy for patients at risk for sudden cardiac death due to ventricular fibrillation and ventricular tachycardia.
Arrhythmogenic cardiomyopathy (ACM), arrhythmogenic right ventricular dysplasia (ARVD), or arrhythmogenic right ventricular cardiomyopathy (ARVC), most commonly is an inherited heart disease.
Hypertrophic cardiomyopathy is a condition in which muscle tissues of the heart become thickened without an obvious cause. The parts of the heart most commonly affected are the interventricular septum and the ventricles. This results in the heart being less able to pump blood effectively and also may cause electrical conduction problems. Specifically, within the bundle branches that conduct impulses through the interventricular septum and into the Purkinje fibers, as these are responsible for the depolarization of contractile cells of both ventricles.
Ventricular tachycardia is a cardiovascular disorder in which fast heart rate occurs in the ventricles of the heart. Although a few seconds of VT may not result in permanent problems, longer periods are dangerous; and multiple episodes over a short period of time are referred to as an electrical storm. Short periods may occur without symptoms, or present with lightheadedness, palpitations, shortness of breath, chest pain, and decreased level of consciousness. Ventricular tachycardia may lead to coma and persistent vegetative state due to lack of blood and oxygen to the brain. Ventricular tachycardia may result in ventricular fibrillation (VF) and turn into cardiac arrest. This conversion of the VT into VF is called the degeneration of the VT. It is found initially in about 7% of people in cardiac arrest.
Flecainide is a medication used to prevent and treat abnormally fast heart rates. This includes ventricular and supraventricular tachycardias. Its use is only recommended in those with dangerous arrhythmias or when significant symptoms cannot be managed with other treatments. Its use does not decrease a person's risk of death. It is taken by mouth or injection into a vein.
Ventricular hypertrophy (VH) is thickening of the walls of a ventricle of the heart. Although left ventricular hypertrophy (LVH) is more common, right ventricular hypertrophy (RVH), as well as concurrent hypertrophy of both ventricles can also occur.
Tachycardia-induced cardiomyopathy (TIC) is a disease where prolonged tachycardia or arrhythmia causes an impairment of the myocardium, which can result in heart failure. People with TIC may have symptoms associated with heart failure and/or symptoms related to the tachycardia or arrhythmia. Though atrial fibrillation is the most common cause of TIC, several tachycardias and arrhythmias have been associated with the disease.
Disopyramide is an antiarrhythmic medication used in the treatment of ventricular tachycardia. It is a sodium channel blocker and is classified as a Class 1a anti-arrhythmic agent. Disopyramide has a negative inotropic effect on the ventricular myocardium, significantly decreasing the contractility. Disopyramide also has an anticholinergic effect on the heart which accounts for many adverse side effects. Disopyramide is available in both oral and intravenous forms, and has a low degree of toxicity.
Loeffler endocarditis is a form of heart disease characterized by a stiffened, poorly-functioning heart caused by infiltration of the heart by white blood cells known as eosinophils. Restrictive cardiomyopathy is a disease of the heart muscle which results in impaired diastolic filling of the heart ventricles, i.e. the large heart chambers which pump blood into the pulmonary or systemic circulation. Diastole is the part of the cardiac contraction-relaxation cycle in which the heart fills with venous blood after the emptying done during its previous systole.
Noncompaction cardiomyopathy (NCC) is a rare congenital disease of heart muscle that affects both children and adults. It results from abnormal prenatal development of heart muscle.
Alcoholic cardiomyopathy (ACM) is a disease in which the long-term consumption of alcohol leads to heart failure. ACM is a type of dilated cardiomyopathy. The heart is unable to pump blood efficiently, leading to heart failure. It can affect other parts of the body if the heart failure is severe. It is most common in males between the ages of 35 and 50.
The following outline is provided as an overview of and topical guide to cardiology, the branch of medicine dealing with disorders of the human heart. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians who specialize in cardiology are called cardiologists.
Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults – is called tachycardia, and a resting heart rate that is too slow – below 60 beats per minute – is called bradycardia. Some types of arrhythmias have no symptoms. Symptoms, when present, may include palpitations or feeling a pause between heartbeats. In more serious cases, there may be lightheadedness, passing out, shortness of breath, chest pain, or decreased level of consciousness. While most cases of arrhythmia are not serious, some predispose a person to complications such as stroke or heart failure. Others may result in sudden death.
Tachycardia-induced cardiomyopathy is a reversible cause of heart failure and dilated cardiomyopathy. Tachycardia-induced cardiomyopathy should be considered in all patients with a dilated cardiomyopathy of uncertain origin and who have tachycardia or atrial fibrillation with a fast ventricular rate.