Dilated Cardiomyopathy (DCM)

It is a disease of unknown etiology, affecting myocardium. Its diagnosis is established by presence of left ventricular dilatation and systolic dysfunction in absence of congenital, valvular,hypertensive, coronary or pericardial heart disease. 

Prominent ventricular dilatation is apparent It’s prevalence rate is 0.04 per cent. Although the cause is not definable, more than 75 specific disease of heart muscle can result in a picture of DCM. It represents a final common pathway that is the end result of myocardial damage, produced by a variety of agents.

Clinical Manifestations

1) Asymptomatic, when the diagnosis is made by 2D Echocardiography.

2) Enlargement of LV. Apex is shifted down and out. The apex impulse is not forceful.Presystolic gallop (S 4 ) may precede the development of failure. Ventricular gallop (S 3 ) is common during decompensation. Regurgitant murmurs are common. Mitral regurgitation is due to enlargement and abnormal motion of mitral annulus and distortion of the geometry of subvalvar apparatus. Ventricular dilatation plays a lesser role. 2nd sound may show reverse split, if LBBB occurs. They present with symptoms and signs of heart failare, as follows:

a)Pulmonary Congestion
Dyspnoea on exertion or at rest, paroxysmal nocturnal dyspnoea. Tachypnoea,pulmonary rales, bronchial spasm and occasional rhonci.

b) Systemic Congestion

Distended neck veins, palpable tender liver and edema of legs and at times ascites, and pleural effusion.

c)Fall in Cardiac Output and Poor Peripheral Perfusion 

Fatigue, weakness, Narrowing of pulse pressure, hypotension, Cold and pale extremities with constricted peripheral veins and delayed capillary refill.

d) Arrhythmias

Palpitations, light headedness, syncope etc.

Electrocardiogarm

Poor R-wave progression, in precordial leads, or q-waves in anterior leads. Intraventricular conduction defects, esqecially LBBB are common. There is LA enlargement. Sinus tachycardia and atrial/ventricular arrhythmias are common. Complex ventricular arrhythmias, including VT/NSVT may predict sudden death.

X-Ray Chest

It shows cardiomegaly with left ventricle (LV) and left atrium (LA) enlargement. There may be signs of pulmonary venous hypertension viz. pulmonary venous redistribution, interstitial edema,alveolar edema and pleural effusion. Systemic venous hypertension may cause dilatation of azygos and Superior Vena Cava (SVC).

2D Echocardiography

 It shows left sided or 4 chamber enlargement with reduced EF. The wall thickness is usually normal. There is generalized hypokinesis. Occasionally segmental wall abnormalities are present Mitral and tricuspid incompetence is seen on Doppler.
 

Coronary Angiography
It shows normal arteries or insignificant coronary artery disease.

Complications

Left and ventricular failure, hypotension. Arrhythmias (both atrial and ventricular) and embolic episodes from LV thrombi. Certain clinical and echo features suggest adverse outcome (Table)

Adverse Outcome in Dilated Cardiomopathy

4)Management

Diagnostic Studies
They are necessary to establish diagnosis, evaluate prognosis and help in medical therapy. They include chest X-Ray, ECG, 2D Echocardiography with Doppler. Coronary angiography is indicated in patients above 40 or when there is history suggestive of ischaemic heart disease. 24 hours ambulatory ECG is necessary when arrhythmias are suspected. Exercise testing is done for assessment of functional capacity. Endocardial biopsy is hardly useful. However, some recent reports have suggested inflammatory etiology in almost 50 per cent with immunohistological methods.

Medical Therapy
Many reversible causes of, cardiomyopathy should always be kept in mind (Table )

i) In asymptomatic stage, preventive therapy with ACE-I/ARBs/β- blockers may help.

ii) If on special diagnostic methods, viral load and/or inflammation is seen, a course of interferon, corticosteroids and azothiaprine may help.

iii) Treatment of cardiac failure viz., ACE-I/ARBs, β-Blockers, digitalis, diuretics are needed.Biventricular Pacing/resynchronization therapy may be useful in patents with wide QRS (>150 msec), LBBB and LV dysfunction. LV assist devices, and cardiac transplant are other methods but as yet, they are not widely available. Adjunctive therapy includes anticoagulation in subjects with low EF to prevent thromboembolic complications,amiodarone to treat symptomatic arrhythmias, maintaining potassium in high normal range(4.3–5mg/ml ), to prevent sudden death and frequent visits to clinic for proper adjustment of drug dosages, particularly β- Blockers.

Potential Reversible Cause of Dilated Myopathy

Few Specific Dilated Cardiomyopathies
1)Anthracycline Cardiomyopathy

It is due to anticancer agent doxorubion (Adriamycine), when the cumulative dose exceeds 450 mg/m 2 in subjects with normal hearts. In presence of heart disease or other risk factors viz. prior mediastinal radiation or when radiation treatment follows chemotherapy, the cardiomyopathy can occur at lower dosage.

2)Postpartum Cardiomyopathy

It is defined as presentation of LV Systolic dysfunction and heart failure in last trimester of pregnancy or within 6 months of delivery. The treatment is like that of dilated cardiomyopathy. Majority will improve and 50 per cent recover completely. Subsequent pregnancy is absolutely contraindicated even if recovery is complete.

3) Alcoholic Cardiomyopathy
In a case of dilated cardiomyopathy alcohol cardiomyopathy is suspected if there is history of alcohol intake of 100g/day for more than 10 years and when patient presents with high cardiac output.The cause is alcohol toxicity and thiamine (B 1 ) deficiency.

4) Cardiomyopathy due to Persistent Tachycardia

In occasional cases, particularly in children recurrent or incessant episodes of supraventricular or ventricular tachyarrhythymias are actually the cause of and not the result of ventricular dysfunction. Restoration of sinus rhythm or slowing of the heart rate will reverse LV dysfunction. Thus this becomes curative and should not be missed.

5) Chagas’ Cardiomyopathy

It is common in south and Central America and is caused by Trypanosoma cruzi.

6)Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)
It is marked by myocardial cell loss with partial or total replacement of RV muscle by adipose and fibrous tissue. The clinical manifestations are seen in adolescence or earlyadulthood, predominantly in males. Physical examination is normal. ECG shows inverted T in right precordial leads. They develop reentrant ventricular tachyarrhythmias of RV origin.LBBB configuration, usually precipitated by exercise. Sudden death is common.Management includes β-blockers, sotalol and amiodarone. Radiofrequency ablation, ICD and cardiac transplant are other options.