Restrictive Cardiomyopathy - Imaging and Diagnosis

Introduction

Restrictive cardiomyopathy (RCM) is a rare form of cardiomyopathy and is less common among the other types of cardiomyopathy. Restrictive cardiomyopathy occurs due to increased stiffness and lack of flexibility of the walls of ventricles affecting their expansion while filling with blood. The systolic (pumping) function of the ventricle might be normal, but the diastolic (filling) function of the ventricle is affected. The muscles of the heart may be normal or slightly enlarged. Over time, the pumping capacity of the ventricles becomes affected and does not provide enough blood to other body parts such as the lungs, liver, etc.

Cardiomyopathy is a medical condition in which the heart fails to pump enough blood to the other parts of the body. Cardiomyopathy is classified into:

• Dilated cardiomyopathy.

• Hypertrophic cardiomyopathy.

• Restrictive cardiomyopathy.

• Arrhythmogenic right ventricular dysplasia.

• Transthyretin amyloid cardiomyopathy (ATTR-CM).

What Are the Causes of Restrictive Cardiomyopathy?

Restrictive cardiomyopathy has various causes. They are:

• Infiltrative Diseases - Amyloidosis (build-up of amyloid proteins in the body organs), sarcoidosis (abnormal collection of inflammatory cells in different body parts), primary hyperoxaluria (high level of oxalate in the urine), and hereditary hemochromatosis (excessive iron in the body).

• Storage Diseases - Gaucher disease, Anderson-Fabry disease, Niemann-Pick, Hurler cardiomyopathy, glycogen storage disease, Danon disease, and Friedrich ataxia.

• Systemic Disease - Diabetes, myofibrillar myopathies, scleroderma, Werner syndrome, carcinoid cardiomyopathy, leukemia fibrosis, hypereosinophilic fibrosis, and metastatic malignancy.

• Idiopathic Causes - Radiation therapy, medications such as Anthracycline, Ergotamines, Busulfan, mercurial agents, and serotonin-containing agents.

What Are the Signs and Symptoms of Restrictive Cardiomyopathy?

The signs and symptoms of cardiomyopathy include:

• Fatigue (tiredness).

• Cough.

• Shortness of breath (initially with heavy activities and over time it occurs with rest).

• Exercise intolerance.

• Orthopnea (difficulty in breathing while lying flat).

• Cardiac cachexia (wasting of body tissues such as muscle, fat, and bone due to heart failure).

• Abdominal swelling.

• Palpitations (pounding or skipping of a heartbeat).

• Chest pain.

• Loss of appetite.

• Swelling of the feet and ankle.

• Inability to concentrate.

What Are the Findings of Restrictive Cardiomyopathy in the Physical Examination?

The findings of restrictive cardiomyopathy in the physical examination include:

• Increased jugular venous pressure.

• Ascites (abnormal collection of fluid in the abdominal cavity).

• Pitting edema (collection of fluid) of the lower extremities.

• Decreased pulse volume.

• Macroglossia (abnormal increase in the size of the tongue).

• Periorbital purpura (purplish spots around the eye due to leakage of small blood vessels).

• Enlarged liver.

• Enlarged neck veins.

• Crepitations (crackling sounds) are rarely heard.

• Decreased breath sounds due to pleural effusions (collection of fluid between the lining of the chest and lungs).

Cardiac Findings:

• Loud S3 (early diastolic filling sound).

• Normal S1 and S2 sounds with normal S2 split.

• S4 is absent (fourth heart sound).

• Heart murmurs due to tricuspid valve regurgitation.

What Are the Complications of Restrictive Cardiomyopathy?

The complications of restrictive cardiomyopathy are:

• Heart failure.

• Abnormal heart rhythms.

• Stroke (damage to the brain cells due to decreased or interrupted blood supply).

• Thromboembolism (blockage of the blood vessels due to blood clot).

• Cardiac cirrhosis (liver disorders that occur secondary to cardiac dysfunction such as valvular disease).

What Are the Diagnostic Tools Used in the Diagnosis of Restrictive Cardiomyopathy?

The diagnostic tools used in the diagnosis of restrictive cardiomyopathy include:

• Complete blood cell (CBC) count (detect eosinophilia).

• Blood gas analysis (detect hypoxia).

• Liver function profile.

• Blood urea nitrogen level.

• Serum electrolyte level.

• Creatinine level.

• Serum brain natriuretic peptide levels.

• Ventricular biopsy.

• Serum iron concentration (detect hemochromatosis).

• Liver biopsy (detect hemochromatosis).

What Are the Imaging Techniques Used in the Diagnosis of Restrictive Cardiomyopathy?

The imaging techniques used in the diagnosis of restrictive cardiomyopathy are:

1. Chest Radiography:

• In restrictive cardiomyopathy, chest radiography shows the findings of congestive cardiac failure without cardiomegaly.

• An increased cardiothoracic ratio resulting from atrial dilation is seen, and the ventricular size seems normal.

• Constrictive pericarditis appears as pericardial calcification in the chest radiograph. However, a chest radiograph alone cannot be used to evaluate restrictive cardiomyopathy, particularly when the patient has constrictive pericarditis.

2. Computed Tomography:

• Cardiac computed tomography is used in diagnosing restrictive cardiomyopathy. They are used to distinguish RCM from constrictive pericarditis.

• Constrictive pericarditis shows pericardial calcification and pericardial thickening. Sometimes, pericardial calcification is absent in constrictive pericarditis in which a pericardial thickening of more than 4 mm is present.

3. Echocardiography:

• Echocardiography is the standard imaging tool used in the diagnosis of restrictive cardiomyopathy.

• Doppler echocardiography and two-dimensional echocardiography are helpful in detecting diastolic dysfunction and distinguishing restrictive cardiomyopathy from constrictive pericarditis.

• In echocardiography, due to inadequate echo lucent windows, the pericardial thickness may be missed.

• Thickened valves, biatrial dilatation, and pericardial effusion are suggestive of cardiac amyloidosis.

• Atrial enlargement with normal left ventricular end-diastolic dimensions is seen in restrictive cardiomyopathy.

• Mid-diastolic reversal flow across tricuspid and mitral valves are seen.

• Non-dilated, non-hypertrophied ventricles with marked dilation of both atriums are seen.

• In constrictive pericarditis, the ventricles are in normal size, and pericardial effusion might be present.

• In infiltrative RCM, echocardiography shows increased left ventricular wall thickness, reduced chamber size, left atrial thrombi, and interatrial septal thickening which is due to amyloid deposition.

4. Cardiac Catheterization:

• Cardiac catheterization is the insertion of a flexible tube called a catheter into the vessels or chambers of the heart to diagnose abnormalities in the heart.

• In cardiac catheterization, restrictive cardiomyopathy appears as increased right heart pressure, typical venous pattern, and dip-and-plateau.

• There is a variation in right and left ventricular diastolic pressure, which is more than 5 mm of Hg, and the right ventricular diastolic pressure is one-third less than the right ventricular systolic pressure. Right ventricular systolic pressure is greater than 50 mm of Hg.

5. Magnetic Resonance Imaging (MRI):

• MRI is a noninvasive imaging tool used to detect the function and morphology of the heart. In RCM, the pericardial thickness of fewer than four millimeters is a key finding in MRI. Based on the thickness of the pericardium, MRI can exclude constrictive pericarditis from RCM.

What Are the Differential Diagnoses of Restrictive Cardiomyopathy?

The differential diagnoses of restrictive cardiomyopathy include:

• Constrictive pericarditis.

• Acute or chronic heart failure.

• Hypertensive heart disease.

• Hypertrophic cardiomyopathy.

• Acute or chronic pericarditis.

Conclusion

Radionuclide imaging in restrictive cardiomyopathy shows diffuse radioactive tracers such as technetium-99m pyrophosphate or indium-111 anti-myosin are indicative of cardiac amyloidosis. Though computed tomography has less role in the diagnosis of restrictive cardiomyopathy, it helps in differentiating RCM from constrictive pericarditis. MRI shows high specificity (100 percent) and 88 percent sensitivity in excluding constrictive pericarditis from RCM. When compared to other types of cardiomyopathy, restrictive cardiomyopathy has a poor prognosis and shows only a two to five-year survival rate.