---

CARDIOMYOPATHY - Complete Exam Answer

---

DEFINITION

• The term cardiomyopathy should be restricted to conditions that primarily affect the myocardium.
• It does NOT include myocardial involvement due to congenital, acquired valvular, hypertensive, coronary arterial, or pericardial abnormalities.

---

CLASSIFICATION

A. Etiologic Classification (Box 1.52)

• Idiopathic (D, R, H)
• Familial (D, R, H)
• Eosinophilic endomyocardial fibrosis (R)
• Endomyocardial fibrosis (R)

• Infective (D): Viral, bacterial, fungal, protozoal, metazoal, rickettsial, spirochetal myocarditis
• Metabolic (D): Glycogen storage disease, mucopolysaccharidosis, hemochromatosis, Fabry's disease
• Deficiency (D): Electrolytes, nutritional
• Autoimmune: SLE, polyarteritis nodosa, rheumatoid arthritis
• Infiltrations & granulomas (R, D): Amyloidosis, sarcoidosis, malignancy
• Neuromuscular: Muscular dystrophy, myotonic dystrophy, Friedreich's ataxia (H, D)
• Sensitivity/Toxic (D): Alcohol, drugs, radiation
• Peripartum heart disease
• Takotsubo (stress) cardiomyopathy

---

B. Clinical Classification (Fig. 1.52 & Table 1.97)

---

C. Pathological Findings

---

---

1. DILATED (CONGESTIVE) CARDIOMYOPATHY (DCM)

Definition/Key Features

• Characterized by dilatation/enlargement of the ventricular chambers and systolic dysfunction (impaired contraction of left and/or right ventricle) with preserved wall thickness.
• Left ventricular mass is increased but wall thickness is normal or reduced.
• Dilatation of valve rings may cause functional incompetence of mitral and tricuspid valves.
• Most common of all cardiomyopathies.
• Responsible for about 1 in 3 cases of heart failure; 3rd most common cause of heart failure.

Etiology

• 1/5 to 1/3 of patients have familial forms.
• Inherited as autosomal dominant.
• Associated with >20 varieties of single-gene mutations.
• Mutations involve genes encoding the cytoskeleton of the myocyte (dystrophin, lamin A and C, emerin, metavinculin).
• X-linked skeletal muscular dystrophies (Becker and Duchenne) are associated with cardiomyopathy.

• Myocarditis: Coxsackie, adenoviruses, HIV, bacteria, fungal, mycobacteria, parasitic (Chagas disease)
• Toxins: Alcohol, chemotherapy (adriamycin, trastuzumab, cyclophosphamide), metals (cobalt, lead, mercury, arsenic)
• Autoimmune diseases: SLE, systemic sclerosis, dermatomyositis
• Endocrine: Diabetes mellitus, thyrotoxicosis, hypothyroidism
• Neuromuscular: Muscular dystrophies, Friedreich's ataxia, myotonic dystrophy
• Nutritional: Thiamine and selenium deficiencies
• Peripartum cardiomyopathy
• Stress induced (Takotsubo)
• Tachycardia mediated
• Hemochromatosis, amyloidosis, sarcoidosis

Clinical Features

• 3x more common in men than women; peak incidence in middle age.
• Symptoms may be gradual OR cause sudden cardiac death due to arrhythmias.
• Thromboembolism, conduction defects, and sporadic chest pain may be present.

• Fatigue and weakness
• Left heart failure: Pulmonary congestion, dyspnea (rest/exertional/nocturnal), orthopnea
• Right heart failure: Systemic congestion, edema, nausea, abdominal pain, nocturia
• Low cardiac output
• Hypotension, tachycardia, tachypnea
• Narrow pulse pressure
• Elevated JVP
• Arrhythmia: Atrial fibrillation, conduction delays, complex PVCs, sudden death

Investigations

• Chest X-ray: Generalized enlargement of heart, features of CHF
• ECG: Tachycardia, conduction abnormalities (AV block, LBBB), diffuse nonspecific ST and T wave changes, arrhythmias (AF, VPCs, VT)
• 24-hour Holter monitor: If lightheadedness, palpitation, syncope
• Echocardiogram/CTI/CMRI: Left ventricular dilation with normal or minimally thickened/thinned walls, global hypokinesia, low EF
• Elevated BNP
• Cardiac catheterization to rule out coronary artery disease
• Myocardial biopsy (rarely necessary)

Treatment

• Control/conventional management of heart failure: Salt restriction, fluid restriction, standard treatment of CHF
• Medical therapy: ACE inhibitors, diuretics, digoxin, hydralazine/nitrate combination
  • L-carnitine, antioxidants, and chelating agents have been tried
  • All patients with dilated cardiomyopathy regardless of cause should be treated with beta-blocker AND ACE inhibitors
  • Aldosterone antagonist and ARNI to be added if still symptomatic
• Anticoagulation prophylaxis
• Implantation of cardiac defibrillator and/or cardiac resynchronization therapy in some patients
• Cardiac transplantation in certain patients

Prognosis

• Majority particularly >50 years die within 4 years of onset.
• Spontaneous improvement or stabilization occurs in 25% of cases.
• Death is due to progressive heart failure, ventricular tachycardia.
• Sudden cardiac death (SCD) is a constant threat.
• Reversible causes (favorable prognosis): Alcohol-induced, trastuzumab, tachycardia-induced, peripartum cardiomyopathy.
• Poor prognosis: Anthracyclines or HIV-induced cardiomyopathy.

---

---

SPECIAL SUBTYPES OF DCM

Alcoholic Cardiomyopathy

• Individuals who consume >80 g/day of alcohol for many years
• Clinical picture resembles idiopathic or familial DCM
• Partially genetically predetermined (ALDH2 gene)
• Abstention may halt progression or even reverse it (important exam point)

Peripartum Cardiomyopathy

• Cardiac dilatation with CHF develops during last trimester or within 6 months of delivery
• Typically present in multiparous women of age >30 years
• Unknown cause; inflammatory myocarditis, immune activation, multiple gestations have been incriminated
• Symptoms, signs, and management are that of IDCM (Idiopathic DCM)
• Further pregnancy should be discouraged

---

---

2. HYPERTROPHIC CARDIOMYOPATHY (HCM)

Definition/Key Features

• Characterized by left ventricular hypertrophy, typically of a nondilated chamber, without any obvious cause.
• Any portion of the LV wall >1.5 cm thick on echocardiogram is considered HCM.
• Familial; transmitted as an autosomal dominant trait.

1. Asymmetric myocardial hypertrophy of the LV with greater hypertrophy of the interventricular septum.
2. A dynamic LV outflow tract pressure gradient related to narrowing of the subaortic area, which may produce LV outflow tract obstruction.

• HCM in old adults is associated with a sigmoid interventricular septum with a knob of cardiac muscle below the aortic valve.

Clinical Features

• Asymptomatic: Echocardiographic finding only; family history may be positive.
• Symptomatic: Dyspnea in 90%; also effort-related angina, breathlessness, arrhythmia, and sudden death.

Signs (High-yield exam content)

• Rapidly rising carotid pulse ("jerky" / "spike and dome") / bisferiens pulse (two systolic peaks)
• Double apical impulse
• Reversed pulsus paradoxus on arterial pulse with Bernheim "a" wave in JVP
• Harsh ejection systolic murmur at lower-left sternal border and apex (due to LVOTO):
  • Increases with: Standing, Valsalva maneuver (reduces preload)
  • Decreases with: Squatting, sustained hand grip (increases afterload), leg raising (increases preload)
• Pansystolic murmur at mitral area due to mitral regurgitation

Investigations

• ECG: Abnormal in 85-90% of cases; LV hypertrophy, abnormal ST-Ts, giant T-wave inversions, abnormal Q' waves, bundle branch block (BBB)
• Chest X-ray: Normal or mild-to-moderate cardiac enlargement
• Echocardiography (diagnostic): Increased LV wall thickness ≥15 mm, systolic anterior motion (SAM) of the mitral valve, dynamic LV outflow tract obstruction
• Genetic testing for evaluation of family members
• Note: Apical nonobstructive cardiac hypertrophy = Yamaguchi syndrome (rare form)

Treatment

• Drug therapy: Beta-adrenergic blockers, calcium channel blockers (verapamil, diltiazem), disopyramide, antiarrhythmics (amiodarone)
• ICD (Implantable Cardiac Defibrillator)
• Myectomy (Morrow Procedure) - partial surgical resection of septum; improves outflow tract obstruction
• Septal ablation - iatrogenic infarction of basal septum using catheter-delivered alcohol solution
• Transplantation

Prognosis

• Risk of SCD higher in children; clinical deterioration is usually slow
• Poor prognosis factors: Males, young age of onset, family history of SCD, history of syncope, exercise-induced hypotension (worst)
• Progression to DCM occurs in 10-15%

---

---

3. RESTRICTIVE (OBLITERATIVE) CARDIOMYOPATHY

Definition

• A rare condition in which ventricular filling is impaired because of stiff ventricles.
• Hallmark is abnormal diastolic function.
• Resembles constrictive pericarditis - important to differentiate because constrictive pericarditis is an operable disease.
• Much less common than DCM or HCM outside the tropics, but a frequent cause of death in Africa, India, South and Central America, and Asia due to high incidence of endomyocardial fibrosis.

Causes

• Idiopathic
• Myocardial:
  • Noninfiltrative: Idiopathic, scleroderma
  • Infiltrative: Amyloidosis, sarcoidosis, Gaucher's disease, Hurler disease
  • Storage disease: Hemochromatosis, Fabry disease, glycogen storage diseases
• Endomyocardial: Tropical endomyocardial fibrosis, hypereosinophilic syndrome, carcinoid, metastatic malignancies, radiation, anthracycline drugs

Clinical Features

• Symptoms of right and left heart failure: Exercise intolerance, dyspnea, peripheral edema, ascites, enlarged tender liver
• Systemic embolism in about 25% of cases
• JVP may be raised with diastolic collapse and positive Kussmaul's sign
• Mild cardiac enlargement; cardiac apex is easily palpable; mitral regurgitation murmur may be heard (NOT found in constrictive pericarditis - key differentiator)
• Heart sounds are soft; 3rd and 4th heart sounds may be heard

Investigations

• ECG: Nonspecific ST-T wave changes, low voltage, arrhythmias
• Chest X-ray: Mild cardiomegaly
• Doppler echocardiography: Abnormal mitral inflow pattern, symmetrically thickened LV walls, systolic dysfunction, prominent E wave (rapid diastolic filling), reduced deceleration time (increased left atrial pressure)
• Cardiac MRI and CT: Show symmetrically thickened LV wall, normal or slightly reduced ventricular volumes and systolic function; useful in differentiating from constrictive pericarditis
• Technetium pyrophosphate imaging: Noninvasive imaging of choice for diagnosing transthyretin amyloidosis - can identify amyloid deposition in the myocardium
• Cardiac catheterization: Shows increased ventricular filling pressures with dip-and-plateau pattern

Treatment

• No satisfactory medical therapy
• Drug therapy with caution:
  • Diuretics for extremely high filling pressures
  • Chronic anticoagulation is often recommended
  • Vasodilators may decrease filling pressure
  • Calcium channel blockers to improve diastolic compliance
  • Digitalis and other inotropic agents are NOT indicated
• Transplantation may be indicated

---

---

4. STRESS (TAKOTSUBO) CARDIOMYOPATHY

Key Features

• Clinical syndrome characterized by acute and transient (<21 days) LV systolic (and diastolic) dysfunction often related to an emotional or physical stressful event
• First described in Japan in 1990; also called Takotsubo cardiomyopathy, broken heart syndrome, apical ballooning syndrome
• Prevalence: 1-2% of patients with suspected acute coronary syndrome
• Exact pathophysiology unknown; most accepted hypothesis: norepinephrine and NPY stored at postganglionic sympathetic system terminations
• Risk factors: Female sex, menopausal, psychiatric illness, diabetes mellitus, obstructive airway disease, substance abuse disorder

Clinical Presentation

• Typical patient: Postmenopausal woman presenting with chest pain (>75%) and/or shortness of breath (~50%), dizziness (>25%), occasional syncope (5-10%)
• Most patients have experienced an emotional or physical stress
• Physical examination: Features of acute decompensated left-sided heart failure + a systolic murmur when there is LV outflow tract obstruction
• Diagnosis based on RWMA beyond territory supplied by single coronary artery, with reversible changes and associated with physical/emotional stress
• ECG abnormal in >95% patients: Ischemic ST segment and T wave changes; T wave inversion is usually deep and wide with prolonged QTc (occurring after 24-48 hours)

Treatment

• Management is mainly supportive therapy and prevention of complications until recovery
• Treatment of heart failure with or without cardiogenic shock as per guideline-directed heart failure management
• Anticoagulation considered for apical thrombus (up to 3 months) or large area of akinesis (until LVEF improves)
• Recurrence: Seen in 2-4% of patients; in-hospital mortality up to 5%
• Recovery of LVEF is seen from 48 hours up to 6 weeks

---

QUICK COMPARISON TABLE (for rapid exam revision)

---

KEY EXAM MNEMONICS & HIGH-YIELD POINTS

1. DCM: Most common CMP; "NINJA-STAR nuclei" on histology; 3x more common in men.
2. HCM: "BOX-CAR nuclei"; SAM on echo is diagnostic; murmur INCREASES with Valsalva/standing, DECREASES with squatting.
3. RCM: "DIP-AND-PLATEAU" on cath; must differentiate from constrictive pericarditis (operable!); Kussmaul's sign positive.
4. Takotsubo: Post-menopausal women + stress event; reversible; prolonged QTc on ECG.
5. Peripartum CMP: Last trimester or within 6 months; discourage future pregnancy.
6. Alcoholic CMP: >80 g/day; abstention can REVERSE it (unlike most other CMPs).
7. AVOID in HCM: Digitalis, diuretics, vasodilators, dihydropyridines (they worsen LVOTO by reducing preload/afterload).
8. AVOID in RCM: Digitalis and inotropes are NOT indicated.