Cardiomyopathy

Cardiomyopathy refers to a group of diseases that affect the heart muscle (myocardium), making it harder for the heart to pump blood to the rest of the body. Over time, cardiomyopathy can lead to heart failure, a condition where the heart can’t pump enough blood to meet the body’s needs. It can also cause other serious complications like blood clots, arrhythmias (irregular heartbeats), and sudden cardiac death. Cardiomyopathy can be acquired (developed due to other conditions) or inherited (passed down through families), and its specific type influences its symptoms, progression, and treatment.

Types of Cardiomyopathy:

Cardiomyopathy is primarily classified into several types based on how the heart muscle is affected.

• Dilated Cardiomyopathy (DCM):
  • The most common type. The heart’s main pumping chamber (left ventricle) becomes enlarged (dilated) and weakened, leading to reduced pumping ability.
  • Can be idiopathic (unknown cause), inherited, or caused by chronic alcohol abuse, viral infections, uncontrolled high blood pressure, or coronary artery disease.
• Hypertrophic Cardiomyopathy (HCM):
  • The heart muscle, especially the walls of the ventricles, becomes abnormally thick (hypertrophied). This thickening makes it harder for the heart to pump blood and can block blood flow out of the heart.
  • Often inherited.
• Restrictive Cardiomyopathy (RCM):
  • The heart muscle becomes stiff and less elastic, meaning it can’t relax properly and fill with blood between beats. The pumping ability may be normal initially, but filling is impaired.
  • Often caused by infiltrative diseases like amyloidosis, hemochromatosis, or sarcoidosis.
• Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC/ARVD):
  • A rare genetic disorder where the muscle tissue in the right ventricle is replaced by fatty and fibrous tissue. This disrupts the heart’s electrical signals and leads to arrhythmias and sudden cardiac arrest.
• Unclassified Cardiomyopathies: Other types that don’t fit into the main categories.

Causes:

The causes of cardiomyopathy vary by type and can include inherited genetic defects, infections, toxins, and other medical conditions. In many cases, the cause remains unknown (idiopathic).

• Inherited Genes:
  • Many types, especially hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy, are inherited from parents.
  • Genetic mutations can affect the proteins that build heart muscle or organize its electrical activity.
• Coronary Artery Disease (CAD) and Heart Attack:
  • CAD can lead to dilated cardiomyopathy by reducing blood flow to the heart muscle, weakening it over time.
  • A prior heart attack can cause scarring that weakens a portion of the heart muscle.
• Chronic High Blood Pressure (Hypertension):
  • Uncontrolled hypertension forces the heart to work harder, leading to thickening (hypertrophy) and eventual weakening.
• Long-Term Alcohol Abuse: Can directly damage heart muscle cells, leading to dilated cardiomyopathy.
• Viral Infections:
  • Certain viral infections (e.g., coxsackievirus B, parvovirus B19, HIV) can cause myocarditis (inflammation of the heart muscle), which can lead to dilated cardiomyopathy.
• Diabetes: Poorly controlled blood sugar can contribute to heart muscle damage.
• Obesity: Increases the workload on the heart and is linked to metabolic syndrome, which contributes to heart disease.
• Thyroid Disease: Both hyperthyroidism and hypothyroidism can affect heart function.
• Infiltrative Diseases (for Restrictive Cardiomyopathy):
  • Amyloidosis: Abnormal protein deposits in the heart muscle.
  • Hemochromatosis: Iron overload in the heart muscle.
  • Sarcoidosis: Inflammatory cells infiltrate the heart.
• Certain Medications:
  • Some chemotherapy drugs (e.g., anthracyclines).
  • Some cancer drugs, like certain targeted therapies or immune checkpoint inhibitors.
  • Certain illicit drugs (e.g., cocaine, amphetamines).
• Pregnancy (Peripartum Cardiomyopathy): A rare form of dilated cardiomyopathy that develops during the last month of pregnancy or within five months after delivery.

Symptoms:

Symptoms of cardiomyopathy often worsen as the condition progresses and the heart’s pumping ability declines. Many people, especially in early stages, may be asymptomatic.

• Shortness of Breath (Dyspnea): Especially with exertion or when lying flat (orthopnea), or waking up with shortness of breath (paroxysmal nocturnal dyspnea).
• Fatigue: Persistent tiredness.
• Swelling (Edema): In the legs, ankles, and feet, and sometimes the abdomen (ascites) due to fluid retention.
• Coughing or Wheezing: Due to fluid buildup in the lungs.
• Chest Pain or Pressure: Especially in hypertrophic cardiomyopathy with exertion.
• Dizziness, Lightheadedness, or Fainting (Syncope): Due to reduced blood flow to the brain or arrhythmias.
• Heart Palpitations: Sensations of a rapid, pounding, or fluttering heartbeat.
• Bloating or Fullness in the Abdomen: Due to fluid retention.
• Weight Gain: Due to fluid retention.

Diagnosis:

Diagnosing cardiomyopathy involves a thorough medical history, physical examination, and various diagnostic tests to assess heart structure and function, and identify the underlying cause.

• Medical History and Physical Exam: The doctor will ask about symptoms, family history of heart disease or sudden death, and risk factors. The exam may reveal heart murmurs, abnormal heart sounds, lung crackles (fluid), or leg swelling.
• Echocardiogram (Echo):
  • The most common and important test. Uses sound waves to create moving images of the heart.
  • Shows heart size, chamber function, thickness of heart walls, valve function, and pumping efficiency (ejection fraction). Essential for classifying the type of cardiomyopathy.
• Electrocardiogram (ECG/EKG): Records electrical signals in the heart. Can detect abnormal heart rhythms, signs of heart muscle damage, or thickening.
• Chest X-ray: Can show if the heart is enlarged or if there is fluid in the lungs.
• Blood Tests:
  • BNP (B-type Natriuretic Peptide): Elevated levels can indicate heart failure.
  • Cardiac Enzymes: To rule out a heart attack.
  • Thyroid Function Tests.
  • Iron Studies (for hemochromatosis), genetic tests (for inherited forms), viral studies, etc.
• Cardiac MRI (Magnetic Resonance Imaging): Provides detailed images of the heart muscle structure, scar tissue, and function. Very useful for diagnosing specific types and causes.
• Cardiac Catheterization and Coronary Angiography:
  • Invasive procedure to measure pressures in the heart chambers and visualize coronary arteries to rule out blockages as a cause of heart muscle weakness.
• Genetic Testing: Recommended for inherited forms of cardiomyopathy, both for diagnosis and family screening.
• Myocardial Biopsy (Heart Muscle Biopsy): (Rarely used) A small piece of heart muscle is taken for examination, usually when infiltrative diseases or myocarditis are suspected.

Treatment:

Treatment for cardiomyopathy aims to manage symptoms, prevent progression of heart failure, reduce complications, and treat the underlying cause. Strategies vary significantly based on the type of cardiomyopathy.

• Medications:
  • ACE Inhibitors or ARBs (Angiotensin Receptor Blockers): Reduce blood pressure and the heart’s workload, improving pumping ability.
  • Beta-Blockers: Slow heart rate, reduce blood pressure, and improve heart function.
  • Diuretics (“Water Pills”): To reduce fluid retention and swelling.
  • Aldosterone Antagonists: (e.g., spironolactone, eplerenone) Help remove excess fluid and may improve heart function.
  • Digoxin: Can improve the pumping ability of the heart and slow the heart rate in heart failure.
  • Blood Thinners (Anticoagulants): (e.g., warfarin, DOACs) To prevent blood clots, especially in dilated cardiomyopathy with reduced ejection fraction or atrial fibrillation.
  • Antiarrhythmics: To control irregular heart rhythms.
  • Specific Medications for Hypertrophic Cardiomyopathy: (e.g., mavacamten, disopyramide) Reduce obstruction or improve heart muscle relaxation.
• Implantable Devices:
  • Pacemaker: For slow heart rates or to synchronize heart contractions (Cardiac Resynchronization Therapy – CRT).
  • Implantable Cardioverter-Defibrillator (ICD): For high-risk patients to prevent sudden cardiac death by delivering an electrical shock to correct dangerous arrhythmias.
• Procedures/Surgery:
  • Septal Myectomy: (For obstructive HCM) Surgical removal of a small part of the thickened heart muscle to relieve obstruction.
  • Alcohol Septal Ablation: (For obstructive HCM) Injecting alcohol into an artery supplying the thickened septum to thin the muscle.
  • Ventricular Assist Devices (VADs): Mechanical pumps implanted in the chest to help the heart pump blood, as a bridge to transplant or destination therapy.
  • Heart Transplant: For end-stage cardiomyopathy that is severe and unresponsive to other treatments.
• Lifestyle Modifications:
  • Sodium Restriction: To manage fluid retention.
  • Fluid Management: As advised by doctor.
  • Regular, Moderate Exercise: As tolerated and advised by doctor.
  • Weight Management.
  • Avoid Alcohol and Illicit Drugs.
  • Manage Underlying Conditions: (e.g., blood pressure, diabetes, thyroid disease).

Living with cardiomyopathy requires ongoing care from a cardiologist, often with a specialized heart failure team, to optimize treatment and improve long-term outcomes.