Author: Dr Arun Mahtani Editor: Dr B V Baliga
Before we deal with the topic restrictive cardiomyopathy we shall first briefly discuss about the dynamics of blood flow through a normal heart and the different layers of the heart as well, having a clear picture regarding these two aspects will help us understand about the disease in a better way.
The layers of the heart
1) The outermost layer that we encounter is the epicardium, this is a continuation of the pericardium, a sac or a bag in which the heart is enclosed. The epicardium is a bridge connecting the pericardium with the myocardium. It mainly consists of blood vessels.
2) The second layer is the myocardium, it is the thickest and the bulkiest of all the three layers, it is concentrated with heart musculature which gives the heart the ability to pump blood throughout the body efficiently.
3) The innermost layer is the endocardium, it is the thinnest of all the three layers, it is lined by smooth muscle cells and also is continuous with the lining of the heart valves protecting it from wear and tear due to continuous blood flow.
Now, let us discuss about the dynamics of blood flow through a heart.
1) Before the heart beats, there is filling of blood in the heart from the peripheries, this is called as the diastolic phase.
2) Once the heart fills with blood and expands to a certain level, the blood is ejected out into the peripheries this constitutes the systolic phase.
Now, in a case of restrictive cardiomyopathy, it’s the case of diastolic phase and the myocardium which is affected in the early stages and progresses to involve the systolic phase as well.
What is the physiology in restrictive cardiomyopathy?
There are 2 events that occur in Restrictive Cardiomyopathy:
1. The first would be an increased stiffness of the heart muscle, which will not allow the heart to accommodate blood when it relaxes. Hence, the volume of blood would be significantly less when compared to a normal heart.
2. Another event which could occur would be infiltration of the heart muscle with certain proteins or certain cells like eosinophils which increases the thickness of the myocardium. This occurs in diseases like amyloidosis.
Because of a decrease in the filling of blood in the ventricles at the end of the diastolic phase the amount of blood pumped to the peripheral structures will also be less.
What are the causes of restrictive cardiomyopathy?
The causes of restrictive cardiomyopathy can be classified as follows:
1) It could be because of some unknown reason – this is called ‘idiopathic’.
2) It could be infiltrative, which means that some outside material is being deposited in the myocardium as it was discussed in the previous section. Amyloidosis is an example of one such condition.
3) It could be treatment induced, this usually occurs in individuals who are undergoing long standing radiotherapy. Prolonged exposure of myocardium to radiation causes fibrosis, leading to increase in its stiffness.
4) It could be as a part of a cancerous condition as many of the cancerous cells can metastasise and get deposited in the myocardium.
Restrictive Cardiomyopathy occurs equally in both men and women in terms of incidence and severity. However when compared to children the disease process has a better prognosis.
What are the symptoms?
Symptoms in RCM are related due to three events:
- During the relaxation phase of the heart contraction cycle, the pressures within the heart increase. This in turn increases the ‘back pressure’ in the blood vessels in the lungs. This is called pulmonary hypertension, and can cause breathing difficulty. Over a period of time, this increased pressure can cause damage to the function of the right side of the heart.
- There is a decrease in the amount of blood that is ejected out of the heart into the body (called stroke volume), leading to symptoms like dizziness and tiredness
- Increased thickness of the heart muscle can compress any blood vessels that run through it. This could lead to a heart attack or severe chest pain.
Complications
1) Arrhythmia i.e irregular heart beats
2) Thromboembolism – Blood clot formation in the legs or the lungs
3) Heart Failure – Weakness of the heart muscle
4) Heart Blocks – Problems with the way electricity is conducted through the heart
5) Myocardial Infarction i.e. a heart attack
What are the investigations that will be performed?
1) Blood Investigations
2) Chest X-Ray: shows enlargement of the heart with features of increased pressure in the pulmonary vasculature.
3) Echocardiography: Dilated atria with normal ventricles or with thickened ventricles can be seen, a special feature in case of Amyloidosis is granular speckles of proteins is seen in the myocardium.
4) ECG: Shows very minimal changes except in cases where cardiomyopathy has lead to fibrillation.
5) Biopsy: A biopsy of the ventricle can be taken to localize whether the pathology lies in the myocardium or the endocardium.
Treatment of restrictive cardiomyopathy
Before initiating treatment, with the help of investigations we should come to a conclusion regarding the etiology of the disease, whether it is primary or is it a part of a systemic disease. After which, a plan of treatment can be established.
1) To correct the high filling pressures, beta blockers and calcium channel blockers maybe of some benefit, they increase the filling time and reduce impulse production from the SA Node.
2) A low dose of diuretic could also be commenced to reduce the preload. But dose should be monitored as it could cause hypotension.
3) If patients are suffering from atrial fibrillation then they must be started on anti coagulant therapy to prevent chances of a thrombus formation.
4) In case of amyloidosis, chemotherapeutic drugs like melphalan can be given to reduce production of fibrillar proteins.
5) The last modality of treatment is a cardiac transplantation.