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Dilated Cardiomyopathy: A Tale Of An Enlarged Heart



What is Dilated Cardiomyopathy?


Dilated cardiomyopathy (DCM) is a heart condition that causes the heart chambers (ventricles) to progressively stretch and enlarge over time. It is characterized by the impaired ability of the left ventricle to contract and pump blood out of the heart to the rest of the body. The estimated prevalence of dilated cardiomyopathy ranges between 1:2500 and up to 1:250-400 in the general population, and is more common in men than in women. It is a common cause of heart failure and heart transplantation worldwide. 


What are the causes of dilated cardiomyopathy?


Most cases of dilated cardiomyopathy are idiopathic, or due to an unknown cause. 

Approximately 30-40% of cases are due to genetic causes, with the TTN gene (a gene encoding for the protein, titin) being a commonly identified genetic mutation. Other key congenital causes include muscular dystrophy, other neuromuscular diseases, and metabolic disorders. 


Acquired causes of this condition are due to certain infections, diseases, and substances, which include:

  • Infections - HIV, viral hepatitis, coxsackievirus, echovirus, bacteria (Borrelia), protozoa (Trypanosoma cruzi)

  • Substances - Alcohol and other drugs, such as cocaine or methamphetamine

  • Diseases - Systemic lupus erythematosus, heart attack, thyroid disease, obstructive sleep apnea

  • Other causes - Radiation therapy, chemotherapy, toxins, heavy metals, pregnancy


What are the symptoms of dilated cardiomyopathy?


As the ventricles of the heart stretch out in this condition, the heart cannot pump blood effectively to the other organs systems of the body. This can lead to fluid retention in the lungs, legs, and abdomen, causing difficulty of breathing and swelling. The enlargement of the ventricles and stretching of the heart muscle can also lead to heart valve problems and abnormal heart rhythms. Heart failure is a common complication of this disease.


Symptoms of dilated cardiomyopathy include:

  • Shortness of breath with exertion (dyspnea)

  • Fatigue

  • Chest pain

  • Palpitations

  • Swelling of the lower legs, feet, or ankles (edema)


How is dilated cardiomyopathy diagnosed? 


After taking a patient’s medical history and performing a physical exam, a physician may order several tests to diagnose dilated cardiomyopathy. These include:


  • Blood tests - to evaluate for signs of inflammation, infection, or cardiac muscle damage

  • Electrocardiogram (ECG) - to monitor for abnormal heart rhythms 

  • Chest xray - to visualize and assess the size of heart

  • Echocardiography or MRI - to visualize and assess the function of the ventricles

  • Exercise stress test - to determine impact of exercise on the heart

  • Genetic testing - to determine if the condition is inherited 


How is dilated cardiomyopathy treated?


The treatment of dilated cardiomyopathy can involve a combination of medication and lifestyle changes to prevent the progression of the disease and improve survival. Medications can help to slow down the structural changes of the heart, improve blood flow, decrease fluid retention, and control high blood pressure that likely strains the heart. These include: 


  • ACE inhibitors

  • Angiotensin receptor/neprilysin inhibitors

  • Aldosterone antagonists

  • Beta blockers/calcium channel blockers

  • Diuretics

  • Nitrates


Additionally, employing lifestyle changes such as engaging in moderate physical activity during the week or enrolling in a cardiac rehabilitation program is encouraged to preserve the strength and function of the heart muscle. Limiting salt intake to 3000 mg/day (and up to 2000 mg/day in patients with chronic heart failure) and fluids can help to prevent fluid retention and swelling in patients experiencing these symptoms.


Advanced therapies for this condition may be needed in patients with severe dilated cardiomyopathy that is not responsive to medical therapy. These include:


  • Left ventricular assist devices

  • Biventricular pacemaker/Cardiac resynchronization therapy

  • Automatic implantable cardioverter-defibrillators

  • Heart transplantation


Course


Dilated cardiomyopathy is a progressive heart condition with an overall poor prognosis. The severity and course of the disease depend on several factors such as ventricular wall thickness, medication compliance, dietary and lifestyle modifications. With no cure for this condition, most patients will progress to heart failure with a mortality rate of up to 50% within five years.  Interventions such as implantable cardio-defibrillators, cardiac resynchronization therapy, and heart transplantation can improve such outcomes. These patients will need to be managed by an interdisciplinary team of healthcare professionals that may include cardiologists, cardiac surgeons, dietitians, and critical care physicians. It is important that these patients regularly seek professional medical care to improve their quality of life and support their medical needs. 



References:








Sweet, M., Taylor, M. R., & Mestroni, L. (2015). Diagnosis, prevalence, and screening of familial dilated cardiomyopathy. Expert opinion on orphan drugs, 3(8), 869–876. https://doi.org/10.1517/21678707.2015.1057498


Mahmaljy, H., Yelamanchili, V. S., & Singhal, M. (2023, April 7). Dilated cardiomyopathy. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK441911/


Reichart D, Magnussen C, Zeller T, Blankenberg S (University Heart Center Hamburg, Hamburg, Germany). Dilated cardiomyopathy: from epidemiologic to genetic phenotypes. J Intern Med 2019; 286: 362–372.


Naso P, Falco L, Porcari A, et al. Epidemiology. 2019 May 18. In: Sinagra G, Merlo M, Pinamonti B, editors. Dilated Cardiomyopathy: From Genetics to Clinical Management [Internet]. Cham (CH): Springer; 2019. Chapter 2. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553847/ doi: 10.1007/978-3-030-13864-6_2


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