Dilated Cardiomyopathy

Dilated cardiomyopathy is the most common type of cardiomyopathy which is seen in 90% of all types of cardiomyopathy. 

As the name of cardiomyopathy suggests that there is a dilatation of all the four chambers of heart. So, you can imagine that the dilatation of chambers can stretch the wall of heart which can lead to a thining of the ventricles and that results into a decrease in myocardial contractility of heart. 

A diminished myocardial contractility leads to a systolic dysfunction as myocardial contractility is essential to generate a good systolic force in order to pump the blood into the systemic and pulmonary circulation. 

Due to systolic dysfunction, heart becomes a bag of blood rather than a pump which overtime lead to a mitral and tricupsid regurgitation and later progresses into a congestive heart failure which is a typical mode of presentation in dilated cardiomyopathy. 

When comes to the causes of dilated cardiomyopathy, it is mostly seen due to unknown reason(idiopathic) or it runs in a family due to the mutation of TTN gene in sarcomeric protein titin.

As Protein Titin in the sarcomere is like spring which control the recoil of the sarcomere after being streched, hence if there is a mutation in it then cardiac muscles loses its elastic property leads to overstreching and dilatation of the chambers.

Alcohol abuse and drugs like cocaine with chronic use can also precipitates dilatated cardiomyopathy.

Antitumor antibiotics like doxorubicin can also cause dilated chambers of heart.

Virus like Coxsakie B virus can precipitates myocarditis due to the lymphocytic infiltrate in the myocardium which results into a dilated cardiomyopathy.

Parasite infection like Chagas Disease which is more prevalent in Latin America can cause dilated cardiomyopathy in older children and adults.

Ischemic Disease like Coronary artery disease are the most common cause of systolic heart failure where the myocytes are replaced by scar tissue after infarction lead to dilated cardiomyopathy. 

Certain systemic conditions like Hemochromatosis which is characterised  by iron overload in heart. This iron overload in heart generates a free radicals by Fenton reaction which causes myocardial damage and eventually into the dilated cardiomyopathy. 

A Sarcoidosis which is non-caseating type of inflammatory disease where myocardial fibrosis and scarring is seen in heart that results into a dilated cardiomyopathy 

Thyrotoxicosis where due to toxic level  thyroid hormones (TH) result into altered energy production by myocytes which disrupts the myofibril contractile function of heart. 

Wet Beriberi which is due to thiamine deficiency as thiamine play a role in contraction in our heart muscle. Hence deficiency of thiamine results into a decrease in the myocardial strength and its contractility which progresses into a dilated cardiomyopathy. 

In Peripartum pregnancy, where a women who are pregnant either late in the 3rd trimester or soon after birth can develop heart failure due to the dilated cardiomyopathy, exact cause unknown but most likely multifactorial. 

As we discussed in the earlier slides that due to overstreching and dilatation of Ventricles, the heart muscle looses its contractile function. Hence it results into a systolic dysfunction. 

A dysfunctional systolic pump prevents the blood from exiting the left ventricle into the systemic circulation due to the decreased ejection fraction and that results into the accumulation of blood at ventricles.

As a result of volume overload at ventricles, the cardiac muscle undergo eccentric hypertrophy adaptation where myocytes are growing in size but they are growing longer and not thicker to cover the streched dilated ventricles by adding the sarcomere in series to the existing sarcomeres. 

In patient with Takotsubo cardiomyopathy, there is an apical ballooning of the left ventricle which often occur after severe emotional distress due to loss of the loved ones, hence called broken heart syndrome. 

In response to the stressful situations, there is an increased sympathetic stimulation in patient with Takotsubo cardiomyopathy which lead to apical ballooning of the left ventricle which causes accumulation of blood at the apical portion of ventricles which unables the left ventricle to contract properly results into a markedly reduces left ventricle ejection fraction in Takotsubo cardiomyopathy patient. 

This picture is showing that how during eccentric hypertrophy, sarcomere laid down in series pattern in order to make the muscles longer to cover the enlarged ventricle which is seen in dilated cardiomyopathy

Here the X-ray images shows the ventricular apical ballooning in Takotsubo cardiomyopathy patient. 

When it comes to clinical finding of dilated cardiomyopathy, the first finding is the sign and symptoms of left and right ventricular Heart failure that is Dyspnea on exertion, cough, orthopnea, pulmonary edema, distended jugular venous pressure and pitting edema.

As in dilated cardiomyopathy, heart systolic pump is not up to the mark which creates a back pressure into the pulmonary circulation results into an increased filtration pressure at pulmonary capillaries causing pulmonary edema and difficulty in breathing during exertion and lying flat.

Due to the Right heart failure in dilated cardiomyopathy the blood backs up into the superior and inferior Vena cava. Back up of blood into superior Vena cava creates a distention of jugular veins and a back flow of blood into the inferior Vena cava creates a high pressure into the systemic veins and that results into a pitting edema in a lower extremity due to extravaction of body fluids into the tissue space. 

When performing an auscultation, it gives S3 heart sound which is an early diastolic sign heard when a very high pressure of left atria causes rapid influx of large amount of blood into a compliant left ventricle as seen in dilated cardiomyopathy. 

Systolic regurgitant murmur in also heard due to a mitral and tricupsid regurgitation which is seen as a complication of dilated cardiomyopathy.

Chest X-ray gives a balloon appearance of heart due to biventricular dilatation of heart as seen in dilated cardiomyopathy. 

Here Echocardiogram reveals an dilated heart with low ejection fraction. 

Here is the X-ray images showing the ballooning of heart in dilated cardiomyopathy patient. 

Patient with Heart failure are advised to Restrict their salt intake in diet as it helps in reducing the congestion of blood by relieving the symptoms edema and heart failure in dilated cardiomyopathy. 

Angiotensin converting enzyme inhibitor works by blocking the conversion between angiotensin 1 and angiotensin 2 to prevent the activation of RAAS system which showed to reduce the mortality in dilated cardiomyopathy patient. 

β blocker are beneficial in chronic systolic heart failure in patient with dilatated cardiomyopathy. 

Diuretics like Spironolactone works by excreting sodium and water by kidney which showed to reduce mortality as it reduces the congestion of blood in patient with dilatated cardiomyopathy.

Digoxin works by improving the hearts contractility without increasing the heart rate in patient suffering from systolic heart failure like in dilated cardiomyopathy. 

Implantable cardiac defibrillator is beneficial corrects the heart rhythm by delivering precisely calibrated and timed electrical shocks to restore a normal heartbeat for patient in dilated cardiomyopathy.

And the last option is the heart transplant if nothing works.