Restrictive Cardiomyopathy

How restrictive cardiomyopathy affects the heart

A healthy ventricle relaxes easily between beats, filling with blood at low pressure. In RCM, the muscle is infiltrated or scarred, so filling requires higher pressure. The atria enlarge, pressure backs up into the lungs (causing breathlessness) and into the veins of the body (causing leg swelling, liver congestion and abdominal fluid). Because the stiff heart cannot increase its filling, it struggles to raise output during exercise.

Causes

Cardiac amyloidosis

The most common cause in adults. Misfolded proteins deposit in the heart:

• Wild-type ATTR amyloidosis: mainly men over 65; increasingly recognized as a cause of heart failure with preserved pumping function.
• Hereditary ATTR: due to TTR gene variants; one variant (V122I) is carried by about 3 to 4% of Black Americans.
• AL amyloidosis: caused by an abnormal plasma cell producing light chains; can progress rapidly and needs urgent treatment.

Symptoms

• shortness of breath, first with exertion, later at rest and lying flat
• fatigue and reduced exercise tolerance
• swelling of the legs, ankles and abdomen
• palpitations from atrial fibrillation
• fainting, especially with exertion
• loss of appetite and early fullness from liver and gut congestion
• low blood pressure, particularly in amyloidosis

Restrictive cardiomyopathy vs constrictive pericarditis

Constrictive pericarditis, a stiff, thickened sac around the heart, causes almost identical symptoms but is often curable by surgically removing the pericardium. Distinguishing them is essential and may require echocardiography, cardiac MRI or CT, and cardiac catheterization measuring pressures in both ventricles.

Diagnosis

• ECG: may show low voltage (typical of amyloid), conduction problems or atrial fibrillation.
• Echocardiogram: normal or mildly reduced pumping, thick or normal walls, large atria and impaired relaxation.
• Cardiac MRI: characterizes the muscle and patterns typical of amyloidosis, sarcoidosis or iron.
• Blood and urine tests: BNP, troponin, and serum and urine light chain tests to look for AL amyloidosis.
• Technetium pyrophosphate (PYP) bone scan: can diagnose ATTR amyloidosis without biopsy when AL is excluded.
• Genetic testing for hereditary ATTR or other genetic causes.
• Heart or other tissue biopsy when needed.

Treatment

Managing symptoms

• Diuretics to reduce fluid; doses must be balanced carefully, as stiff hearts depend on adequate filling.
• Salt and fluid limits as advised.
• Rate or rhythm control for atrial fibrillation; anticoagulants to prevent stroke, as clot risk is high.
• Pacemakers or defibrillators for conduction disease or dangerous rhythms.
• Some standard heart failure drugs, such as beta-blockers and ACE inhibitors, may be poorly tolerated, especially in amyloidosis.

Treating the cause

• ATTR amyloidosis: stabilizer medicines (tafamidis, acoramidis) slow progression and improve survival; gene-silencing therapies are used for hereditary forms and some cardiomyopathy.
• AL amyloidosis: chemotherapy and immunotherapy targeting the abnormal plasma cells, sometimes with stem cell transplant.
• Hemochromatosis: regular blood removal (phlebotomy) or iron chelation.
• Sarcoidosis: immunosuppressive treatment.
• Fabry disease: enzyme replacement or chaperone therapy.

Advanced options

Heart transplantation, sometimes combined with other treatment, for selected people with advanced disease, including children with idiopathic RCM.

Outlook

The outlook depends heavily on the cause and how early it is found. Untreated AL amyloidosis with heart involvement has a poor prognosis, while modern treatments for ATTR amyloidosis and hemochromatosis have significantly improved outcomes. Regular follow-up with a cardiomyopathy or amyloidosis specialist is important.

Frequently asked questions

What is restrictive cardiomyopathy?

It is a rare disease in which the heart muscle becomes stiff and cannot relax properly to fill with blood. The heart's squeezing may be normal, but pressure builds up behind it, causing heart failure symptoms like breathlessness and swelling.

What causes restrictive cardiomyopathy?

In adults, the most common cause is cardiac amyloidosis, where abnormal proteins build up in the heart. Other causes include sarcoidosis, hemochromatosis, radiation, Fabry disease and genetic mutations, which are the main cause in children.

How is restrictive cardiomyopathy treated?

Treatment includes diuretics to control fluid, managing heart rhythm problems and preventing clots, plus treating the underlying cause, such as tafamidis for ATTR amyloidosis or chemotherapy for AL amyloidosis. Heart transplant is an option for some people.

What is the difference between restrictive cardiomyopathy and constrictive pericarditis?

Both prevent the heart from filling properly and cause similar symptoms. In restrictive cardiomyopathy the heart muscle is stiff; in constrictive pericarditis the sac around the heart is thickened. Constrictive pericarditis can often be cured with surgery, so telling them apart is important.