Cardiac sarcoidosis is a rare condition that is challenging to diagnose due to its non-specific symptoms. However, if discovered too late, it can lead to potentially life-threatening arrhythmias and heart failure.

Royal Brompton Hospital is a specialist centre with the largest population of cardiac sarcoidosis patients in the world – in excess of 2000. This has provided us with insights to key diagnostic characteristics of the disease, even at an early stage, as well as features that could predict outcomes in patients with cardiac sarcoidosis.

Dr Vasilis Kouranos, consultant respiratory physician at RB&HH Specialist Care, tells us more about this condition.

What is sarcoidosis

Sarcoidosis occurs when a specific inflammation causes tiny lumps (or granulomas) to develop on the body’s tissues. It mainly affects the lungs, skin and lymph glands but can affect most organs. When the lumps accumulate within one area of the body, it can affect the way the organ functions.

Sarcoidosis is a rare disease, affecting around 1 in every 10,000 people in the UK. Every year in the UK about 3,000 to 4,000 people are diagnosed with sarcoidosis.

Discovering the cause

Many patients have no symptoms and the disease is often diagnosed by chance, following a diagnostic test to rule out another condition. Although there is no definitive cure, patients can benefit from treatments which can significantly improve quality of life.

The cause of the disease is unknown, but research suggests it may be linked to an over-reaction of the immune system to infectious and environmental agents – including allergens. Any age group can be affected, but the majority present between 20 and 45 years of age.

Furthermore, genetics can play a part, with family members of those with sarcoidosis having a five-fold increased risk of being affected. Also, people of African/Caribbean or Northern European (Scandinavian) descent have a higher incidence of the disease, suggesting a genetic predisposition in these ethnic groups.

Sarcoidosis and the heart

There are two ways the heart can be affected by sarcoidosis. Firstly, sarcoidosis can occur in the heart muscle itself, this is known as cardiac sarcoidosis. Secondly, the heart may be indirectly affected due to pulmonary hypertension caused by sarcoidosis in the lungs. Both conditions require expert medical supervision to reduce the risk of serious complications.

Cardiac sarcoidosis occurs when the heart muscle itself is affected. The accumulation of immune cells causes clumps of tissue (granulomas) which can occur in the heart.

The condition can affect any part of the heart muscle, causing a range of symptoms depending on the part of the heart affected. Recent research conducted by the experts, including Dr Kouranos, suggests cardiac sarcoidosis occurs in up to a third of all sarcoidosis patients, but only causes specific symptoms in around 5 to 10 per cent of cases.

In advance cases, cardiac sarcoidosis can lead to an arrhythmia or heart failure. Cardiac involvement is responsible for up to 75 per cent of deaths from sarcoidosis, which is why it is an important condition not to miss.

Understanding cardiac sarcoidosis symptoms

Diagnosing cardiac sarcoidosis can be challenging, particularly as symptoms do not appear until structural changes or rhythm abnormalities have occurred, by which time the outcome of treatment may have already been affected.

Symptoms of cardiac sarcoidosis include irregular heartbeat, dizziness, fainting or loss of consciousness, unexplained shortness of breath, chest pain, and swelling of the legs (in later stages).

The disease can result in a weakened heart or abnormal heart beats which disrupt the heart’s lower chamber, and are caused by a build-up of granulomas in the heart muscle (known as heart block). This is the most common manifestation of the disease seen first, and is reported in 25 to 30 per cent of patients. Heart failure can occur when the granulomas build up in the arteries of the heart, which constrict blood flow.

Further investigations for cardiac sarcoidosis are needed for patients who are less than 60 years of age, with new-onset unexplained heart block. Patients of any age, with unexplained arrhythmias originating from the lower heart chambers of the heart (ventricles), and patients with unexplained new-onset heart failure should be referred for specialist treatment.

Diagnosing cardiac sarcoidosis

Most newly diagnosed sarcoidosis patients will have an electrocardiogram (ECG), continuous recording of the heart rhythm over 24 hours using a holter monitor, and an echocardiogram.

Suspected cardiac sarcoidosis patients may go on to have further diagnostic tests such as Magnetic Resonance Imaging (MRI) to identify involvement of sarcoidosis in the heart affecting its function, and nuclear imaging that can identify any active inflammation within the heart muscle and can help to guide treatments.

Clinical electrophysiology studies can uncover abnormalities which may result in abnormally slow heart rates, as well as any abnormally fast or dangerous heart rhythms which can arise from areas of inflammation or scarring.

A right heart catheter test can also be used to measure the pressures in the heart and in the nearby blood vessels to determine pulmonary hypertension involvement.

A biopsy of the heart is rare and only used when there is a specific reason to do so. Patients who have had a lung biopsy will usually not need a heart biopsy or any further biopsies.

Controlling the disease as early as possible

It is important to start treatment as early as possible because inflammation in the heart can lead to heart failure or life-threatening arrythmias.

Timely diagnosis and treatment with medication is important. Patients can be prescribed specific heart medications to help regulate heart rhythm or to treat any heart failure. An implantable pacemaker or defibrillator (ICD) can also be used to help regulate the heart’s rhythm or treat heart failure. In rear cases a heart transplant may be considered.

Dr Kouranos explains, “Treatment to suppress sarcoidosis activity may effectively control the disease in the long-term and should be continued under expert supervision until the treating clinician is confident that the disease is in remission.”

A multi-disciplinary approach makes the difference

Due to the non-specific symptoms of cardiac sarcoidosis, expertise in multiple areas is needed to make an accurate diagnosis.

This includes experts in echocardiography, MRI and positron emission tomography (PET) imaging, cardiology and respiratory medicine. These specialists come together as part of a multidisciplinary team (MDT) to look at each individual patient in-turn to make an informed, accurate diagnosis utilising all their expertise.

Together, the team can detect not only the presence of the disease, but also features of disease activity, which could be targeted using effective treatment strategies. The combination of cardiology and respiratory expertise allows the design of a precise treatment strategy for each individual patient and prevention of life-threatening complications such as major arrhythmic events.