Dilated Cardiomyopathy

Overview

Cardiomyopathies are a widely diverse set of heart muscle disorders that induce heart failure. They are characterized by progressive flow and frequently have a protracted and undetected asymptomatic period. Primary cardiomyopathy, particularly dilated cardiomyopathy, is becoming more common (1/2500 population aged 30 to 40 years, and probably more).

Dilated cardiomyopathy(DCM) (a name established by W. Brigden in 1957, and clinical characteristics first described by J.F. Goodwin in 1961) is a chronic, largely irreversible cardiac disease. It is distinguished largely by left ventricular dilatation and systolic failure (remodeling with normal thickness of the walls).

It might be genetic or acquired, hereditary (25 to 50%) or non-inherited, and is classified clinically as primary or secondary. Anamnesis, physical examination, electrocardiography (ECG), ergospirometry, continuous 24-hour ECG Holter monitoring, radiological examination, echocardiography, CT angiography, MRI of the heart, radionuclide ventriculography, and invasive diagnostics (catheterization, endomyocardial biopsy) with genetic analysis are all part of the dilated cardiomyopathy diagnostic protocol.

Endomyocardial biopsy combined with cardiac catheterization may help to clarify the etiology, and in 25-30% of individuals with a clinical presentation of dilated cardiomyopathy, the origin of the disease is a mutation in a number of genes that encode different proteins in the heart muscle (e.g. troponin, myosin, desmin, etc.).

Apart from postmyocardial and ischemic dilatations, the broad etiologic spectrum includes drug-induced dilatation (alpha-interferon, cytostatic drugs), cocaine addiction, severe malnutrition, selenium deficiency (Keshan disease), carnitine deficiency, beriberi, and hereditary muscle diseases (Duchenne and Becker muscular dystrophies, Emery-Dreifuss muscular dystrophies), mitochondriopathy, delayed diseases, and some endocrinological and autoimmune diseases.

Dilated cardiomyopathy is the most common cause of heart failure and the most common indication for heart transplantation. Therapy is demanding, highly sophisticated, extremely complex and multidisciplinary.

DCM can be caused by a variety of factors, each of which has a varied impact on ventricular function. While most DCM patients experience symptoms, a minority may be asymptomatic due to compensatory processes. As the ventricles continue to enlarge, ventricular function declines, which is followed by conduction system anomalies, ventricular arrhythmias, thromboembolism, and heart failure. The sooner these people are discovered and treated, the higher their chances of survival.

 

How common is Dilated Cardiomyopathy?

DCM occurs more frequently in men than in women. Its general population prevalence is predicted to be 36 cases per 100,000 people. DCM is responsible for 10,000 fatalities and 46,000 hospitalizations in the United States each year. Because many individuals are asymptomatic and so go misdiagnosed while having LV failure, these estimates may underestimate the real prevalence.

 

How Dilated Cardiomyopathy develops?

Idiopathic etiology is responsible for many cases of dilated cardiomyopathy (DCM). However, it can also be caused by a variety of cardiac insults. Ventricle enlargement can occur as a result of LV failure or as a result of a primary cardiomyopathic disease, and it can be linked with both systolic and diastolic dysfunctions. Systolic function is thought to be reduced due to cardiac remodeling, which results in an increase in both end-systolic and end-diastolic volumes.

The gradual dilation of the ventricles causes considerable tricuspid and mitral valve insufficiency, lowering the ejection fraction and increasing ventricular wall stress and end systolic volumes. Early compensatory responses include increased heart rate and peripheral vascular system tone. However, these compensatory processes cause geometric remodeling of the ventricles, which eventually worsens the myocardial damage. Simultaneously, there is neurohumoral activation of the renin-angiotensin-aldosterone system and a rise in catecholamine circulation levels. Furthermore, the levels of natriuretic peptides rise. Eventually, these compensating systems are exhausted, and the heart collapses.

Histologic examination of the myocardium often reveals nonspecific fibrosis and hypertrophic alterations. It also shows cardiac damage with a significant infiltration of inflammatory cells.

 

What causes Dilated Cardiomyopathy (DCM)?

Although there is no clear cause in many cases, dilated cardiomyopathy is most likely the result of myocardial damage caused by a number of toxic, metabolic, or viral factors. In many situations, the cause is unknown. It might be caused by fibrous changes in the myocardium as a result of a previous myocardial infarction. It might also be the late effects of acute viral myocarditis, such as Coxsackie B virus and other enteroviruses, which could be mediated by an immunologic mechanism.

Other causes include:

1. Infection: several pathogens can cause inflammatory dilated cardiomyopathy (DCM), including:

• Viruses: adenovirus spp., coronavirus spp., coxsackievirus spp. (groups A and B), cytomegalovirus spp., dengue virus, echovirus spp., Epstein–Barr virus, hepatitis B virus, hepatitis C virus, herpes simplex virus, human herpesvirus 6, HIV, influenza A and influenza B viruses, mumps rubulavirus, parvovirus (B19), poliovirus, rabies virus, respiratory syncytial virus, rubella virus, measles virus and Varicella-zoster virus.
• Bacteria: β-haemolytic streptococci, Borrelia burgdorferi, Brucella spp., Campylobacter jejuni, Chlamydia spp., Clostridium spp., Corynebacterium diphtheriae, Neisseria spp., Haemophilus influenza, Legionella pneumophila, Listeria monocytogenes, Mycoplasma pneumoniae, Neisseria meningitidis, Salmonella (Berta and Typhi), Streptococcus pneumoniae, Staphylococcus spp. and Treponema pallidum.
• Protozoa: Entamoeba histolytica, Leishmania spp., Plasmodium vivax, Plasmodium falciparum, Toxoplasma gondii and Trypanosoma cruzi.
• Helminths: Taenia spp., Echinococcus spp., Schistosoma spp., Toxocara spp. and Trichinella spp.
• Fungi: Actinomyces spp., Aspergillus spp., Candida spp., Coccidioides immitis and Cryptococcus neoformans

 

2. Autoimmunity: autoimmune diseases, including systemic sclerosis, rheumatoid arthritis, systemic lupus erythematosus, dermatomyositis, sarcoidosis, Dressler syndrome, post-cardiotomy syndrome, post-infectious autoimmune disease and post-radiation autoimmune disease

 

3. Toxin exposure: alcohol, amphetamines, anthracyclines, cannabis, catecholamines, cocaine, 5-fluorouracil, lithium, heavy metals (cobalt, lead and mercury) and carbon monoxide.

 

4. Metabolic or endocrine dysfunction: Cushing disease, hypothyroidism, hyperthyroidism, phaeochromocytoma, chronic hypocalcaemia, hypophosphataemia and inborn errors of metabolism such as mitochondrial diseases and nutritional deficiency (carnitine, thiamine and selenium).

 

5. Neuromuscular diseases: various forms of muscular dystrophy and myotonic dystrophy, dystrophinopathies, Friedreich ataxia and myotonic dystrophy.

 

6. Pregnancy and peripartum cardiomyopathy: Peripartum cardiomyopathy is a heart muscle weakening that develops during the last month of pregnancy and lasts for about five months after birth, with no other known cause. It usually happens shortly after birth. It is an uncommon condition with mild to severe symptoms. The ejection fraction, or the proportion of blood the heart pumps out with each beat, is one indication of the severity of the condition. A typical ejection fraction value is around 60%.

 

The extent of the damage does not appear to alter the degree or rate of healing. Patients with a very low ejection fraction, for example, can finally recover entirely from peripartum cardiomyopathy. Some individuals recover just a portion of their cardiac function over a six-month or longer period. In certain cases, the heart can regain full strength in as little as two weeks.

When compared to other forms of cardiomyopathy, peripartum cardiomyopathy has a comparatively good recovery rate. A high percentage of women who develop peripartum cardiomyopathy improve and recover.

 

7. Genetic: About 25–35 % of those afflicted have familial variants of the disease, with the majority of mutations affecting genes encoding cytoskeletal proteins and some affecting other proteins involved in contraction. The condition is genetically diverse, but the most prevalent mode of transmission is autosomal dominant. There is also autosomal recessive (as in Alström syndrome), X-linked (as in Duchenne muscular dystrophy), and mitochondrial inheritance of the condition. Some relatives of dilated cardiomyopathy patients have preclinical, asymptomatic heart-muscle alterations.

Cardiac actin, desmin, and nuclear lamins A and C are other cytoskeletal proteins implicated in DCM. DCM is thought to be caused by mitochondrial deletions and mutations that impair myocardial ATP production.

Recent research has indicated that those who have a high frequency of premature ventricular contractions (extrasystole) (many thousands per day) can develop dilated cardiomyopathy. In these circumstances, significantly reducing extrasystole (for example, by ablation treatment) frequently causes the cardiomyopathy to reverse.

 

What medical history and physical exam can reveal?

The majority of dilated cardiomyopathy (DCM) cases occur between the ages of 20 and 60; however, DCM can occur in children or the elderly. A considerable proportion of DCM patients may have a protracted latent phase during which they are clinically asymptomatic. When symptoms do appear, they are caused by LV systolic dysfunction. A complete evaluation is recommended in addition to a focused cardiac history and examination to identify any systemic diseases or secondary causes.

Paroxysmal nocturnal dyspnea, orthopnea, leg edema, and shortness of breath are all classic symptoms. Nonspecific symptoms such as fatigue, malaise, and weakness may also occur. In more severe situations, thromboembolic consequences, conduction abnormalities, arrhythmias, or even sudden cardiac death may occur. Physical examination findings are mainly unrelated to other causes of cardiomyopathy and are typical of congestive heart failure.

Crackles in the lung fields, high jugular venous pressures, peripheral edema, and an S3 gallop are all findings. The point of greatest impulse, or PMI, is traditionally moved laterally. As a result of ventricular enlargement and annular dilatation, tricuspid or mitral regurgitation murmurs are fairly uncommon. A jugular venous distension, A-wave, big V waves, and positive hepatojugular reflux may be discovered during a neck examination.

 

How is Dilated Cardiomyopathy (DCM) evaluated?

Prior to making the diagnosis of idiopathic DCM, secondary causes of dilated cardiomyopathy (DCM) should always be investigated. The workup is aimed at finding any potentially reversible reasons. Thyroid function tests, HIV serology, electrolytes, and iron studies are all recommended laboratory tests (to rule out hemochromatosis). When substance misuse is suspected, a urine toxicology screen and alcohol level might be performed. Genetic testing should be considered in some family instances. In circumstances when the diagnosis is ambiguous, serum B-type natriuretic peptide (BNP) levels can be obtained. Low levels of BNP can help rule out CHF. Furthermore, BNP levels can help with prognosis.One should also rule out hypothyroidism and anemia.

A chest X-ray may reveal cardiomegaly as well as pulmonary effusions and venous congestion. Nonspecific ST segment and T wave abnormalities may be seen on an electrocardiogram (ECG). Atrial fibrillation can also be detected with an ECG.

A consumption of less than 14 ml/kg/min of oxygen per minute implies a dismal prognosis.

Echocardiography, which gives an objective evaluation of ventricular size, function, and any associated valve anomalies, is critical in the diagnosis of DCM. An echocardiogram can also detect the existence of a mural thrombus. Finally, echocardiography can aid in the distinction of DCM from hypertrophic and restrictive cardiomyopathy.

Coronary angiography should be done in patients who have no history of CAD to better characterize coronary architecture and rule out occult ischemia disease as the etiology of DCM. When storage disorders or infiltrative causes are suspected, a myocardial biopsy is very seldom required. As previously stated, histologic findings of idiopathic DCM are vague, and biopsy subjects patients to needless risk.

 

Treatment of Dilated Cardiomyopathy

Medical therapy:

Drug therapy can reduce the evolution of the cardiac problem and, in some situations, even improve it. Salt restriction, ACE inhibitors, diuretics, and beta blockers are examples of standard treatment. Anticoagulants can also be used to treat thrombosis. There is some evidence that coenzyme Q10 can help treat heart failure.

 

Electrical treatment:

Patients with intraventricular conduction delay may benefit from artificial pacemakers, while those at risk of arrhythmia may benefit from implanted cardioverter-defibrillators. These types of therapy have been demonstrated to minimize hospitalization, alleviate symptoms, and avoid sudden cardiac death in people with systolic heart failure. Furthermore, in patients with a confirmed LMNA mutation responsible for dilated cardiomyopathy disease phenotype and clinical risk factors, an implanted cardioverter-defibrillator should be investigated as a treatment option for the main prevention of sudden cardiac death. A unique risk score calculator has been created to calculate the likelihood of persistent ventricular arrhythmia in DCM patients during the next 5 years.

 

Surgical treatment:

Heart transplantation may be considered in individuals with advanced disease who have failed medical treatment. One-year survival rates for these persons exceed 90%, and more than half live for more than 20 years.

 

Complications of dilated cardiomyopathy

Complications from dilated cardiomyopathy include:

1. Heart failure: If you have dilated cardiomyopathy, your heart may be unable to supply your body with the blood it requires to function correctly, potentially leading to heart failure. Fluid accumulation can occur in the lungs, belly, legs, ankles, and feet.
2. Heart valve regurgitation: Enlargement of the left ventricle may make it more difficult for your heart valves to seal, resulting in a backward flow of blood and a less efficient heart pump.
3. Heart rhythm problems: Changes in the structure of your heart, as well as changes in the pressure in your heart's chambers, can result in the development of irregular cardiac rhythms (arrhythmias).
4. Sudden cardiac arrest: Dilated cardiomyopathy can cause your heart to suddenly stop beating.
5. Blood clots (emboli): Blood clots can form as a result of blood pooling in the left ventricle and enter the circulation, cutting off blood flow to essential organs. These blood clots can result in a stroke, a heart attack, or organ damage. Blood clots can also be caused by arrhythmias.

 

How Dilated Cardiomyopathy can be prevented?

Dilated cardiomyopathy is a hereditary disease that cannot be prevented. Healthy living practices, on the other hand, can help you avoid or lessen the problems of dilated cardiomyopathy. If you have dilated cardiomyopathy or are at risk for it, you should do the following:

• Don't smoke.
• Don't drink alcohol, or drink in moderation.
• Don't use cocaine or other illegal drugs.
• Eat a healthy diet that is low in salt (sodium).
• Maintain a healthy weight.
• Follow an exercise program recommended by your doctor.
• Get enough sleep and rest.
• Manage stress.

 

Outcome of Dilated Cardiomyopathy

Overall, people with dilated cardiomyopathy have a bleak outlook. The majority of people eventually develop chronic heart failure. Many become candidates for a heart transplant or a mechanical assist device, which adds to their morbidity. The ejection fraction and origin of the illness influence the progression to heart failure. Almost half of all patients die within 5 years.

Advanced NYHA classification, male sex, severe CHF, and renal failure are all negative prognostic markers. Individuals with symptoms at rest and/or who are unable to exercise typically have the worst prognosis. Peak V02 levels are now frequently used to predict mortality; people with high levels have a much better outlook than those with low levels. Patients with moderate CHF can have a relatively high quality of life with proper medical care.

Cardiomyopathy-related mortality was predicted to be 5.9 per 100,000 worldwide populations in 2010, equating to 403,000 fatalities — an increase from 5.4 per 100,000 in 1990. These estimates may be influenced by bias caused by misclassification, missing or incomplete data, and other factors. Furthermore, worldwide consortia are needed to group patient cohorts in order to address the issue of a low number of occurrences during follow-up.

 

Conclusion

Dilated cardiomyopathy (DCM) is a disorder in which the heart becomes enlarged and unable to properly pump blood. Symptoms range from no symptoms to fatigue, limb edema, and shortness of breath. It can also cause chest pain or fainting. Cardiac failure, heart valve problems, or an irregular heartbeat can all be complications.

Genetics, alcohol, cocaine, some poisons, pregnancy problems, and certain infections are all potential causes. Coronary artery disease and high blood pressure may be factors, although they are not the major reason. In many situations, the cause is unknown. It is a kind of cardiomyopathy, which is a group of disorders affecting the heart muscle. An ECG, chest X-ray, or echocardiography may be used to confirm the diagnosis.

Treatment for heart failure may include drugs from the ACE inhibitor, beta blocker, and diuretic groups. A low-salt diet may also be beneficial.  Blood thinners or an implanted cardioverter defibrillator may be indicated for those who have specific forms of irregular heartbeats. CRT (cardiac resynchronization treatment) may be required. If other procedures fail, a heart transplant may be a possibility in rare cases.

One in every 2,500 persons is impacted. It is more common in men than in women. The most common age of onset is middle age. The five-year survival rate is around 50%. It is also frequent in youngsters and is the most common kind of cardiomyopathy in this age range.