Restrictive Cardiomyopathy

The word "Restrictive" in Medical Terminology is used when there is some kind of pathological condition due to the deposition of substance at organ level that restrict or prevents the organ from doing it's normal function. 

Restrictive cardiomyopathy is the least common cause of cardiomyopathy in which the heart restricts from filling blood during diastole.

The inability of the heart to accept the blood in restrictive cardiomyopathy is due to the fact that there is a “proteineus deposition at the endomyocardium of the heart which prevents the heart from receiving the blood during diastole. 

As a result heart becomes a rigid noncompliance heart which causes a backflow of blood into the pulmonary and peripheral circulation which then starts to show the typical symptoms of heart failure i.e Dyspnea on exertion, pulmonary edema, peripheral edema. 

Here in this picture you can see that the ventricles of heart in a restrictive cardiomyopathy is thick as compared with the normal heart due to the proteineus deposition at ventricles. 

Let's go through the forms of junk which disrupts the diastolic function of heart in restrictive cardiomyopathy. 

Postradiation fibrosis, where patient who had heavy radiation to the chest can develop fibrosis at heart. Radiotherapy has been used in most of the cancers as a loco-regional treatment but it can also cause a damage to cells of heart via various routes like free radicals, coagulation system activation by cytokines and growth factors, inflammation induced damage, epithelial alteration with regeneration, scarring and healing processes which ultimately leads to Restrictive Cardiomyopathy.

Loeffler syndrome, which is seen in parasitic infection where there is an infiltration of eosinophils at the heart's muscular layer that leads to three progressive clinical stages. The first stage involves acute inflammation and subsequent death of heart muscle cells. In the second stage, the endomyocardium of the heart forms blood clots which break off and then travel and block various arteries.The third stage is a fibrotic stage, i.e. Loeffler endocarditis, wherein a damaged heart muscle tissue replaces with scar to cause a poor contraction and expansion of heart that ultimately lead to Restrictive Cardiomyopathy. 

Endocardial fibroelastosis is the uncommon cause of Restrictive Cardiomyopathy that occurs in young children where the innermost lining of the heart chambers (the Endocardium ) becomes thick due to an increase in the amount of supporting connective tissue and elastic fibres which then shows the symptoms of Restrictive Cardiomyopathy.

Amyloidosis is a classic cause of restrictive heart disease where the amyloid protein deposites in the heart. The Amyloid are a misfolded proteins which is characterised by β-pleated sheet configuration that shows Congo red on staining and apple-green birefringence when shown under polarised light. 

One of the Amyloid protein is a Serum transthyretin where the non-mutated serum transthyretin deposits in heart that mostly seen in older age individuals called Senile Cardiac Amyloidosis.

Whereas the mutated Serum transthyretin can also deposites in heart and can run in a family causes restrictive cardiomyopathy. Hence, named Familial Amyloid Cardiomyopathy. 

Sarcoidosis involves non-caseating granuloma formation at the wall of heart making it difficult for the heart to expand resulting in a restrictive cardiomyopathy. 

Hemochromatosis where due to the  excessive deposition of iron at the heart makes the heart susceptible to Free Radical Damage and Fibrosis leading into a Restrictive Cardiomyopathy. Although Hemachromatosis is most commonly seen in Dilated Cardiomyopathy.

Here is the histological image of amyloid deposition at the endomyocardium of the heart. 

The Pathophysiology behind Restrictive cardiomyopathy is that heart becomes less complaint due to the deposition of proteineus substance. This non-compliant ventricles restricts the heart from relaxing during the diastolic phase of cardiac cycle. 

As a result there is a rise in cardiac filling pressure which prevents the blood from filling the heart and that causes a backflow of blood into the pulmonary and peripheral circulation which brings the sign and symptoms of Heart failure in Restrictive Cardiomyopathy. 

Ejection fraction in restrictive cardiomyopathy is usually normal or mildly decreased because there is no problem in contractility of the heart.     

The classic sign of restrictive heart disease is Kussmaul's sign where the JVP (Jugular Venous Pressure) rises on inspiration due to stiff non-compliant ventricles which prevents the venous return into the right ventricle and causes back flow of blood into the venous system. Hence, Jugular Venous Distension (JVD) is seen.

Normally, the JVP falls with inspiration because we know that inspiration promotes right ventricular volume expansion during diastole due to the reduced pressure in the thoracic cavity. 

Therefore, a positive Kussmaul sign suggests an impaired filling of the right ventricle due to a poor compliant heart. 

Another Clinical finding seen in Restrictive Cardiomyopathy especially during amyloidosis that there is a low voltage ECG is seen despite of thick myocardium.

Reason behind low voltage ECG in Amyloid associated Restrictive cardiomyopathy is that a thick myocardium here is not thick due to Hypertrophy but gets thick due to deposition of amyloid proteins.        

                                                  

Here the Electrocardiogram shows a low voltage ECG. 

Treatment of restrictive cardiomyopathy is based on treating the underlying cause.

Like if its due to Hemochromatosis then we treat them with phlebotomy or deforoxamine to rid the body of excess iron and maintain normal iron stores. 

To treat Sarcoidosis associated restrictive cardiomyopathy we prefer to give them glucocorticoid to reduce the inflammation. 

Amyloid associated Restrictive cardiomyopathy needs to transplant the Heart if heart gets an end stage damage. Amyloid can't be removed from the Heart.