Dilated Cardiomyopathy - Causes, Symptoms, Diagnosis, and Treatment

Introduction

Dilated cardiomyopathy is a heart muscle disease presenting with dilation or enlargement of one or both ventricles and defective contraction. Such patients have reduced ventricular ejection fraction by less than 40 percent. Few patients have systolic dysfunction, but symptoms of heart failure are absent. In most patients, the disorder progresses into heart failure and death. A heart transplant is an ideal treatment for improving survivability.

What Is Dilated Cardiomyopathy?

Dilated cardiomyopathy is a heart muscle disorder that can cause heart chambers, especially ventricles, to thin and stretch, leading to enlargement. The disease begins in the left ventricle and progresses to the right ventricle. It reduces the heart's efficiency in pumping blood throughout the body. Dilated cardiomyopathy is life-threatening and progresses to heart failure.

The incidence of dilated cardiomyopathy is unknown, as some patients are asymptomatic. However, the disease prevalence is more common in men than women. The disease is often diagnosed in individuals between 20 to 60 years. It is diagnosed with equal frequency among children and the elderly.

• Primary Dilated Cardiomyopathy: It is idiopathic and can be diagnosed by ruling out other heart conditions.

• Secondary Dilated Cardiomyopathy: The disease occurs secondary to underlying systemic disorders.

What Are the Causes of Dilated Cardiomyopathy?

• Idiopathic causes.

• Familial or genetic factors.

• Mutations in genes for Desmin (cytoskeletal), Lamin C (nuclear membrane), or Myosin (contractile protein).

• A virus causes infectious myocarditis (immune response to microbial infection in the heart), Chagas disease (an infectious disease caused by a parasite), or Lyme disease (bacterial disease transported through ticks).

• Ischemic heart disease (damage to heart blood vessels).

• Hypertension (high blood pressure) and diabetes (high blood glucose levels).

• Medications like cancer drugs (Anthracyclines). Illegal drugs like cocaine and Amphetamines (central nervous system stimulants).

• Long-term alcohol abuse.

• Human immunodeficiency virus (HIV).

• Peripartum cardiomyopathy (heart failure with unknown cause occurring during the last phase of pregnancy).

• Stress cardiomyopathy (physical or emotional stress reduces cardiac function) is a rare condition frequently reported as the cause of developing dilated cardiomyopathy.

• Complications caused by late-stage pregnancy.

• Excessive iron in the heart and other organs can cause damage to heart muscles.

• Heart valve diseases like mitral valve and aortic valve regurgitation (improper closure of heart valves).

What Is the Disease Process for Dilated Cardiomyopathy?

Dilated cardiomyopathy of idiopathic or other etiology cause enlargement of ventricles. Enlarged ventricles exhibit systolic and diastolic dysfunction. Reduction in systolic function is caused by myocardium remodeling, resulting in elevated end-systolic and end-diastolic volumes.

It further causes dilatation of ventricles resulting in insufficiency of the tricuspid and mitral valves. This disease process can further reduce ejection fraction (volume of blood ejected from ventricles during each heartbeat), causing increased end-systolic volume and ventricular wall stress.

During the early phase of the disease process, compensatory mechanism form, causing enhanced tone of peripheral vasculature and heart rate. These compensatory mechanisms worsen the myocardial injury by remodeling of ventricles. In addition, neurohumoral activation of renin-angiotensin and aldosterone hormones enhances catecholamine (neurotransmitter) circulation in the blood. There is an increase in the natriuretic peptide (encourages the elimination of sodium from kidneys) levels. All these factors contribute to heart failure.

What Are the Clinical Features of the Disease?

Most patients are clinically asymptomatic. However, patients with left ventricular systolic dysfunction present symptoms such as:

• Chest pain and discomfort.

• Paroxysmal nocturnal dyspnea (shortness of breath that develops 1 to 2 hours after sleep).

• Leg swelling

• Orthopnea (discomfort in breathing while sleeping flat).

• Palpitations of the heart.

• Shortness of breath during lying down and activity.

• Reduced ability to exercise.

• Edema in ankles, feet, legs, and abdomen.

• Non-specific symptoms like weakness, fatigue, and malaise may develop.

• In patients with severe disease, conduction disturbances, thromboembolic complications (blood clots in veins), arrhythmia (irregular heartbeat), and sudden cardiac arrest develop.

How to Diagnose Dilated Cardiomyopathy?

Physical examination and medical history are essential for diagnosing dilated cardiomyopathy. The following test is necessary for the evaluation.

• Echocardiogram: The test can detect blood flow in the heart and valves. The enlargement of the ventricles can be identified.

• Blood Tests: They can detect infections, substances, or diseases that can cause dilated cardiomyopathy.

• Chest X-ray: It can reveal the condition and shape of the heart and lungs. Fluids around the lungs can be detected.

• Electrocardiogram (ECG): The test records the heart's electrical activity. The test can analyze heart rate, rhythm, and volume of blood flow.

• Holter Monitor: It is a portable ECG device worn throughout the day to record heart activity.

• Exercise Stress Test: The test involves riding a stationary bike or running on a treadmill. ECG is used to monitor the heart's response to physical activity.

• Heart CT (Computed Tomography) Or MRI (Magnetic Resonance Imaging) Scan: The imaging study reveals the size and function of the heart's pumping chamber.

How Is Dilated Cardiomyopathy Treated?

Reversible underlying causes must be immediately treated. In individuals with acute congestive heart failure exacerbation with hypervolemia (increased blood volume), intravenous loop diuretics are administered. Chronic and stable diseases require only oral diuretics to reach normal blood volume. In dilated cardiomyopathy patients with heart failure and reduced ejection fraction, angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARB) are helpful in treatment. Patients with class II to IV heart failure and systolic dysfunction are treated by blocking aldosterone receptors with Spironolactone (hypertensive medication) and Eplerenone (used in treating high blood pressure).

In all patients with heart failure and reduced ejection fraction, beta-blockade (reduces heart rate) is achieved with Carvedilol, Bisoprolol, and long-acting Metoprolol if there are no contraindications.

Individuals with advanced disease stages are treated with Isosorbide nitrate (heart failure medication) and Hydralazine (medicine to treat high blood pressure). Anticoagulants are administered if artificial valves, fibrillation (irregular heart rate), or mural thrombus (thrombi attaching to the wall of a blood vessel) are present.

Heart failure patients are recommended for resynchronization therapy (treatment to correct heart rhythm) and implanted cardioverter defibrillators (battery-supported devices to stop irregular heartbeat).

Individuals that do not respond to medical therapy require heart transplantation. LVAD (left ventricle assist device) may be considered if heart transplantation is not recommended. Indications for heart transplant are:

• Refractory cardiogenic shock (reduced tissue blood supply due to low cardiac output).

• Ventricular arrhythmias.

• High levels of inotropes (medicine that alters the heart's force of contraction).

• Dependence on IABP (intra-aortic balloon pump) and ventricular assist devices.

What Are the Complications of Dilated Cardiomyopathy?

Patients with dilated cardiomyopathy are at risk of developing -

• Congestive Heart Failure: The heart cannot pump enough blood to meet body requirements. If the condition is untreated, it can become life-threatening.

• Valvular Heart Disease: Cardiomyopathy causes incomplete closure of valves, causing leakage in heart valves. Blood tends to flow back through heart valves.

• Abnormal Cardiac Rhythms: The condition is also known as cardiac arrhythmias. Changes in heart size and shape cause irregular heart rhythms.

• Sudden Cardiac Arrest: Sudden stoppage of the heart occurs in dilated cardiomyopathy.

• Blood Clots: Blood pooling in the left ventricle causes blood clot formation. The clot entering the bloodstream blocks blood flow to the heart, brain, and other organs.

What Is the Differential Diagnosis for Dilated Cardiomyopathy?

• Cardiac tamponade is when a fluid sac around the heart is filled with blood or other fluids leading to pressure build-up in the heart.

• Acute pericarditis is a painful disorder caused by redness and swelling of the fluid sacs around the heart.

• Hypertrophic cardiomyopathy is a condition where the heart muscles become abnormally thickened.

• Restrictive cardiomyopathy is a disorder in which the lower heart muscle stiffens, resulting in insufficient blood filling.

Conclusion

Dilated cardiomyopathy is a heart disorder that worsens gradually and cannot be cured. Most patients progress into heart failure or mortality within five years of diagnosis. Though treatments are available, they provide symptomatic and supportive care and are inefficient in mitigating the disease. Heart transplantation must be done if necessary to improve the patient's health. Adequate medication and exercise can improve symptoms in most patients.