Myocardial Disease: Cardiomyopathy and Myocarditis

Cardiomyopathies are a group of disease that primarily affect the heart muscle and not due to the result of congenital, acquired valvular, hypertension, coronary arterial or pericardial abnormalities. 

Definition and overview

What is a cardiomyopathy?

Cardiomyopathies are a disease of the heart muscle, that causing impaired function, which makes it hard for the heart to deliver blood to the body, and can lead to heart failure.

What are the classic types of cardiomyopathy?

Cardiomyopathies it is of 3 types:

1. Dilated cardiomyopathy (ischemic) 
2. Hypertrophic cardiomyopathy 
   
3. Restrictive cardiomyopathy.
   

 Patients with previous MIs and HF are also now included in this group (ischemic cardiomyopathies).

Clinical Classification of Cardiomyopathies

1. Dilated: Left and/or right ventricular enlargement, impaired systolic function, CHF, arrhythmias, emboli.
2. Hypertrophic: Disproportionate LVH, typically involving the septum more than the free wall, with or without an intraventricular systolic pressure gradient; usually of a nondilated left ventricular cavity.
   
3. Restrictive: Endomyocardial scarring or myocardial infiltration resulting in restriction to left and/or right ventricular filling.

Dilated Cardiomyopathy

What is Dilated Cardiomyopathy?

Dilated cardiomyopathy is a type of heart muscle disease that causes the heart chambers (ventricles) to thin and stretch, growing larger. It typically starts in the heart's main pumping chamber (left ventricle), and most commonly occurs in the setting of ischemic heart disease.

Dilated or (congestive) cardiomyopathy is the most common Types of cardiomyopathy, and It's most common cause for heart transplants.

What is Features of Dilated Cardiomyopathy?

Systolic and diastolic dysfunction due to increased ventricular volume and pressure eventually leads to decreased cardiac output and overt heart failure. It's characterized by diminished myocardial contractility, usually involving both ventricles

Remember - Dilated cardiomyopathy makes it harder for the heart to pump blood to the rest of the body.

What is Causes of Dilated Cardiomyopathy?

Causes of Dilated cardiomyopathy includes: 

1. Idiopathic (MCC) - Approximately one-half of all cases of dilated cardiomyopathy remain idiopathic.
2. Familial (~35%): Genetic autosomal dominant & X-linked cardiomyopathy.
   
3. Infectious myocarditis (10–15%)
   
4. Peripartum - The majority of patients with peripartum cardiomyopathy (approximately 80%) present within 3 months of delivery; 10% present during the last month of pregnancy, and 10% present 4 to 5 months postpartum.
   
5. Immunological: SLE 
   
6. Severe coronary disease or infarctions or chronic aortic/mitral regurgitation. 
   
7. Iatrogenic: Adriamycin, Alcohol, Cocaine, Doxorubicin, Cyclophosphamide 7) Endocrine: Acromegaly, thyrotoxicosis, myxedema, diabetes mellitus. 
   
8. Hematological: Sickle cell anemia. 
   
9. Metabolic: Beriberi (Thiamin deficiency), glycogen storage diseases.
10. Infiltration: Amyloidosis, Sarcoidosis, hemochromatosis. 
11. Nurological: Freidreich's ataxia, Duchenne myopathy, myotonia atrophica.

What is Idiopathic dilated cardiomyopathy?

Idiopathic dilated cardiomyopathy is a term used to describe a dilated left ventricle with a ↓ EF in the absence of systemic hypertension, CAD, chronic alcoholism, congenital heart disease, or other systemic diseases known to cause dilated cardiomyopathy. A genetic predisposition may exist.

Clinical features of Dilated cardiomyopathy:

• Symptoms: Presents with exertional dyspnea, fatigue, syncope, ↓ exercise tolerance, and edema.
• Chest pain can be seen with some etiologies (eg, myocarditis)
  
• Dilated cardiomyopathy may have associated functional mitral or tricuspid regurgitation.
  
• Cerebral or systemic embolic phenomena secondary to mural thrombi occur with complaints of focal weakness, numbness, or a cold, painful extremity.

How Familial dilated cardiomyopathy is diagnosed? 

Familial dilated cardiomyopathy can be diagnosed in an individual with known idiopathic dilated cardiomyopathy and at least one of the following: at least 1 relative also diagnosed with idiopathic dilated cardiomyopathy, or at least 1 first-degree relative with an unexplained sudden death under 35 years of age

Diagnosis & Investigations of Dilated Cardiomyopathy 

• ECG: Can be normal. If abnormal, look for evidence of left ventricular enlargement, conduction disorders (wide QRS, LBBB), or arrhythmias (AF, nonsustained VT).
• Echo (key diagnostic study): LV dilatation, ↓ EF, the globally impaired contraction (transesophageal echo is more sensitive and specific than transthoracic) is hallmark of Dilated cardiomyopathy.
  
• CXR: moderate to marked cardiomegaly, ± pulmonary edema & pleural effusions.
  
• Laboratory evaluation: Can be helpful in diagnosing specific etiologies (e.g., HIV).
  
• Endomyocardial biopsy: Not routinely recommended and generally low yield.

Treatment for patients with Dilated Cardiomyopathy 

Treatment is Similar to that of systolic heart failure. 

1. Revascularization: Appropriate for patients with ischemic dilated cardiomyopathy.
2. Neurohormonal blockade: β-blockers, ACEIs (or angiotensin receptor blockers), spironolactone (for patients with stage III or IV heart failure). Disease progression is controlled by the use of ACE-inhibitors.
3. Symptom control: Diuretics, nitrates.
   
4. Anticoagulation: Controversial; generally used only in patients with a history of systemic thromboembolism, AF, or evidence of an intracardiac thrombus.
   
5. Other: Hemofiltration (for patients with oliguria or renal dysfunction), cardiac resynchronization, ventricular assist devices, cardiac transplantation, ICD for malignant arrhythmias (e.g., VT). Implantable defibrillator may decrease risk of sudden death when the ejection fraction is <35%.
6. Cardiac transplantation remains the standard treatment in refractory cases.

What is Prognosis of Dilated cardiomyopathy? 

Prognosis differs by etiology: postpartum (best), ischemic/GCM (worst). Patients typically have a progressively downhill course; death usually occurs within 2 years of symptom onset unless cardiac transplantation is attempted.

Hypertrophic Cardiomyopathy (HCM)

Definition and overview of Hypertrophic Cardiomyopathy (HCM)

Hypertrophic cardiomyopathy is characterized by muscular hypertrophy of a nondilated left ventricle. Most patients have regional variations in the extent of hypertrophy, but the majority demonstrate disproportionate septal hypertrophy.

- Previously it was called hypertrophic obstructive cardiomyopathy (HOCM), but left ventricular outflow obstruction is found only in 1/3rd patients.

- Hypertrophic Cardiomyopathy (HCM) is the most common cause of sudden death in young athletes, and may be the first manifestation of disease

- HCM is a common type of cardiomyopathy. Prevalence is 1:500 to 1:1000, inherited as autosomal dominant. About half of the patients have a positive family history. First degree relatives should be screened.

The Role of genetics & Pathogenesis of Hypertrophic Cardiomyopathy (HCM)

Although hypertrophic obstructive cardiomyopathy (HOCM) can apparently develop sporadically, it is hereditary in >60% of cases and is transmitted as an autosomal dominant trait. An abnormality on chromosome 14 has been identified in the familial form of the disease.

The main problem is diastolic dysfunction due to a stiff, hypertrophied ventricle with elevated diastolic filling pressures. These pressures increase further with factors that increase HR and contractility (such as exercise) or decrease left ventricular filling (e.g., the Valsalva maneuver).

The heart is hypercontractile, and systole occurs with striking rapidity. As a result of the hypertrophy, left ventricular compliance is reduced, but systolic performance is not depressed. Diastolic dysfunction is characteristic, resulting in decreased compliance and/or inability for the heart to relax. 

Ejection fractions are often 80–90% (normal is 60%, ±5%), and the left ventricle may be virtually obliterated in systole.

Clinical Features of Hypertrophic Cardiomyopathy (HCM)

Most patients are asymptomatic or mildly symptomatic.

• Symptoms: Dyspnea (MC), Palpitations, Chest pain (angina), Syncope. Dyspnea on exertion is the most common symptom. Syncope occurs in 30% of patients.
• Sudden death may be the first clinical manifestation and is more common in children or young adults. 
  
• Signs: (Jerky) Double carotid arterial pulse, Double apical beat, Loud S4 
• Systolic ejection murmur: Best heard at left lower sternal border (LLSB), decreases with squatting, lying down, straight leg raise, or sustained handgrip; increases with Valsalva and standing

 An S4 and a sustained apical impulse are characteristic. 

What is Risk factors for sudden death in HCM?

1. A history of previous cardiac arrest or sustained VT 
2. Recurrent syncope 
   
3. An adverse genotype and/or family history of sudden cardiac death (< 50 years old) 
   
4. Failure of blood pressure to rise during exercise (no change or hypotension) 
   
5. Non-sustained VT on 24 hour Holter monitoring 
   
6. Marked increase in left ventricular wall thickness (> 30 mm on echocardiography) 
   
7. Delayed gadolinium enhancement on cardiac MRI.
   

The following HCM patients should undergo risk stratification (electrophysiologic testing) and possible ICD placement: those with a family history of sudden death, syncope (especially if recurrent orexertional), nonsustained VT on Holter monitoring, > 3 cm thickness of interventricular septum, or decreased BP with exercise.

Diagnosis & Investigations of Hypertrophic Cardiomyopathy 

• Chest X-ray: May show mild to moderate cardiac shadow, but (x-ray) usually unremarkable.
• ECG: LV hypertrophy with ST and T wave changes and prominent septal (Q waves) in leads I, AVL, V5-6 due to septal hypertrophies. 
  
• NB: In the presence of asymmetric septal hypertrophy large septal Q waves on the EKG may be mistaken for evidence of MI.
  
• ECHO: LV hypertrophy-often with asymmetric septal hypertrophy, vigorously contracting ventricle. The distinctive hallmark of the disease is unexplained myocardial hypertrophy, usually with thickening of the interventricular septum.
• Holter monitor: Detects ventricular arrhythmias as the cause of syncope.
  
• Genetic testing: Not routinely done, but has the potential to identify the genotype (which has prognostic value) and screen family members.

Treatment options for Hypertrophic Cardiomyopathy (HCM)

Asymptomatic patients generally do not need treatment, but this is controversial.

1) All patients should avoid strenuous exercise, including competitive athletics.

2) Medical: There is no pharmacological treatment that improve prognosis. 

1. B- Blockers and CCB (e.g. verapamil) reducer symptoms can help to relieve angina and sometimes prevent syncopal attacks. 
2.  Disopyramide can be added to either β-blocker or CCB to improve symptoms.
   
3. Amiodarone may be helpful in arrhythmia.

 Digoxin, Diuretics and Vasodilators are contraindicated.

3) Electrophysiologic study and implantable cardioverter-defibrillator (ICD) placement: Indicated for patients with syncope or a family history of sudden cardiac death.

4) Surgical: Myomectomy has a high success rate for relieving symptoms. It involves the excision of part of the myocardial septum. And It is reserved for patients with severe disease.

Surgical myectomy: Removes tissue from hypertrophic septum and relieves outflow tract obstruction. Improves symptoms but does not ↓ the rate of sudden cardiac death.

4) Percutaneous alcohol septal ablation: Has the same objective as surgical myectomy by injection of alcohol into hypertrophic septum, causing local infarction.

5) Endocarditis prophylaxis: Patients with dynamic outflow obstruction or mitral regurgitation should receive endocarditis prophylaxis.

Restrictive or (Oblitrative) Cardiomyopathy

Introduction to Restrictive or (Oblitrative) Cardiomyopathy

Restrictive Cardiomyopathy is a myocardial disorder characterized by rigid noncompliant ventricular walls. It is the least common of the causes of cardiomyopathy, and is usually caused by myocardial fibrosis (idiopathic) or infiltration of myocardium (e.g., by amyloid, hemosiderin, or glycogen deposits)

What are the characteristics of Restrictive cardiomyopathy?

• The progressively rigid ventricle leads to impedance of filling, high filling pressures, and persistently elevated venous pressure.
• Increase myocardial stiffness due to fibrosis or myocardial infiltration, which impaired diastolic ventricular filling due to decreased ventricular compliance --> Increase diastolic ventricular pressures (Diastolic HF). Systolic dysfunction is variable and usually occurs in advanced disease.
  
• Restrictive cardiomyopathy Usually affects the right ventricle (peripheral edema > pulmonary edema; Diuretics “refractoriness”)
• Symptom & signs: Patients present with dyspnea, fatigue, and peripheral edema. Elevated filling pressures cause dyspnea and exercise intolerance. Right-sided signs and symptoms are present for the same reason.

What is the Causes of Restrictive Cardiomyopathy?

1. Myocardial fibrosis (idiopathic). 
2. Infiltrative disease (Amyloidosis, Sarcidosis, hemochromatosis, Scleroderma, glycogen storage disease, esinophilic disorders). 
   
3. Fabry's disease: X-linked disorder (alpha-glycosidase deficiency)--> increase deposition of glycolipid. 
   
4. Fibroelastosis: idiopathic Endomyocardial fibrosis in child in first 2 years. 
   
5. Carcinoid syndrome 
   
6. Chemotherapy or radiation induced

How Restrictive cardiomyopathy is diagnosed?

• ECG: Shows conduction system disease, low QRS voltage, and nonspecific ST-T-wave changes.
• Echo: typically reveals symmetric thickening of the ventricular walls with normal or mildly reduced systolic function.
  
• CXR: pulmonary vascular congestion with a normal cardiac silhouette.
  
• Right heart catheterization: Dip-and-plateau ventricular filling pressure (“square root sign”), pulmonary hypertension, respiratory concordance of the right and left ventricles.
  
• Endomyocardial biopsy may be diagnostic: Detects infiltrative diseases such as amyloidosis and sarcoidosis.

Role of emergency medical services in the management of Restrictive Cardiomyopathy

There is no good therapy; ultimately results in death from CHF or arrhythmias

1) Treat underlying disorder 

• Hemochromatosis: Phlebotomy or deferoxamine 
• Sarcoidosis: Glucocorticoids for acute flares
• Amyloidosis: Treat underlying cause of amyloidosis, consider organ transplantation if severe end-organ disease (i.e., heart, kidney, liver if transthyretin amyloidosis)
• Treat according to EF (HFrEF therapy or HFpEF therapy)

2) Standard therapy of CHF & anticoagulants: Use diuretics and vasodilators (for pulmonary and peripheral edema) cautiously, because a decrease in preload may compromise cardiac output

3) Anti-arrhythmic drugs only for symptomatic sustained arrhythmia. 

4) Cardiac transplantation remains the standard treatment in refractory cases.

Myocarditis

General Information 

• Definition: Myocarditis is an inflammatory process of the myocardium, caused by infection, autoimmune disease (e.g. lupus) or toxins (e.g. cocaine).
• Features: Pathologically, myocarditis is characterized by focal inflammatory infiltration. The process frequently extends to the pericardium, causing a pericarditis.
• Causes: Viral infection is the most common cause, particularly Coxsackie B and influenza viruses A and B. 
• Other causes include: Lyme disease, Chagas’ disease, acute rheumatic fever, SLE, and medications (e.g., sulfonamides); can also be idiopathic.

Types & Clinical features of Myocarditis 

Generally Clinical features of myocarditis is Precordial chest pain with signs of CHF

1. Fulminant myocarditis: Follows a viral illness, causing severe heart failure or cardiogenic shock. 
2. Acute myocarditis: Presents more gradually with heart failure; it can lead to dilated cardiomyopathy. 
   
3. Chronic active myocarditis: Rare, with chronic myocardial inflammation. 
   
4. Chronic persistent myocarditis: Can cause chest pain and arrhythmia, sometimes without ventricular dysfunction.

Diagnosis & Investigations 

• Look for elevations in cardiac enzyme levels and erythrocyte sedimentation rate. Troponins and CK are elevated in proportion to the extent of damage.
• Consider the diagnosis of myocarditis in young patients who present after a viral illness. They commonly have no coronary risk factors and have cardiac enzymes but normal coronary arteries on cardiac catheterization.
• Definitive diagnosis made by Myocardial biopsy

Treatment & Prognosis

• Treatment is supportive. In most patients, the disease is self-limiting and the immediate prognosis is good; however, death may occur due to ventricular arrhythmia or rapidly progressive heart failure.
• Treat underlying causes if possible, and treat any complications (Treat heart failure)
  
• Cardiac transplantation for severe cases.

 Acute myocarditis is a common cause of “idiopathic” dilated cardiomyopathy.