Pericardial diseases

Dr Harry Brown explains the common causes, symptoms and management of pericardial diseases.

Pericardial diseases are less common than heart diseases. They are often missed or diagnosed late as they have a lower profile than primary cardiac diseases such as IHD.

pericardial effusion

Anatomy and physiology
The pericardium comprises up to 50ml of pericardial fluid (an infiltrate of plasma) within the pericardial cavity, which is sandwiched between an inner visceral layer that is apposed to the cardiac surface and an outer parietal layer.

The pericardium is composed mainly of collagen and elastin fibres. The pericardial cavity allows the heart to move slightly relative to other structures and alter shape, as it is not fully fixed to surrounding structures. In addition, this helps to reduce friction due to cardiac motion but at the same time anchors the heart relative to nearby anatomical structures.

We know it is not an essential structure, as it can be surgically removed and its absence does not confer any obvious disadvantage. However, it can act as a barrier to the passage of infection. There is also metabolic activity from the pericardium that may impact on cardiac function.

Pathology
The pericardium can become vulnerable to malignancy, infection, connective tissue disorders, metabolic disorders and trauma, but because the pericardium is a relatively simple structure the responses to pathological insults are relatively limited.

Pericarditis is a response to multiple pathological states and can lead to complications such as cardiac tamponade and constriction.

Acute pericarditis
As the name suggests, acute pericarditis is an inflammatory response from the pericardium to a number of insults.

Common causes include viral infections, such as Coxsackie B, SLE and following an acute MI. Viral causes rarely last for a long time or cause any significant persisting problems. Pericarditis is often associated with a sharp, retrosternal chest pain, worsened by inspiration, swallowing, coughing and lying flat. The pain may be dull, sharp or burning and may be confused with myocardial pain.

The pain may be made easier by sitting up.

An important clinical sign is the pericardial friction rub, heard by auscultation.

Diagnosis
A diagnosis of acute pericarditis is suggested by an ECG with saddle-shaped ST elevation, or even first suggested by an ECG during investigations for chest pain. However, these changes can be easily confused with the ST changes seen during an acute MI. The ECG changes are widespread.

Generally speaking, a chest X-ray and echocardiogram are unhelpful in uncomplicated acute pericarditis, unless a significant volume of pericardial fluid exists, which will be detected by echocardiography. Cardiac enzymes and troponin levels should be checked, while inflammatory markers are usually raised.

Further investigations are often performed to determine an underlying cause of pericarditis.

Management
Pharmacological interventions include NSAIDs, steroids and colchicine. Sometimes the condition can relapse and recurrent pericarditis can occur, which can require reducing dosages of steroids and NSAIDs, and may require the introduction of immunosuppressive drugs, such as azathioprine, and sometimes the use of colchicine.

Occasionally a pericardectomy may have to be considered.

The prognosis will depend on the aetiology. Most viral and idiopathic cases follow a self-limiting course within one to three weeks.

Not unexpectedly, pericarditis associated with neoplasm, purulent effusion or TB has a complicated course and worse outcome.

Pericardial effusion
Pericardial effusion is the accumulation of fluid within the pericardial sac. This is a relatively common manifestation of pericardial disease and of acute pericarditis, so anything that can cause acute pericarditis can cause a pericardial effusion.

If there is a large volume of fluid within the pericardial sac, cardiac tamponade can result. This haemodynamic situation can lead to a compromise of critical cardiac functions and can be either acute or chronic, mild to severe, and may even be life-threatening.

When large volumes of fluid accumulate within the pericardial sac, this results in a raised intrapericardial pressure. This can lead to circulatory failure as the heart becomes compressed by the fluid surrounding it.

Symptoms can include breathlessness and chest discomfort, although an effusion can be painless. On ECG, QRS voltage is often decreased, a chest X-ray will show an enlarged heart, while echocardiography can prove very useful in detecting the fluid. The impact of tamponade can be wide ranging.

Pericardiocentesis
Removal of the pericardial fluid can be useful for both therapeutic and diagnostic purposes. Pericardiocentesis can be performed by needle, with haemodynamic and echocardiography monitoring, or by surgical means. Sometimes a drain may have to be left in place if there is a risk of re-accumulation of fluid. Fluid obtained may be sent for cytology and an infection screen (including TB).

Constrictive pericarditis
Some disease processes of the pericardium, such as acute pericarditis, radiation exposure and intrathoracic malignancy, can result in a thickened, scarred, inelastic and calcified pericardium. This may result in problems with diastolic cardiac filling, resulting in a reduced cardiac output.

It is not always easy to differentiate a restrictive cardiomyopathy from a constrictive pericarditis. These conditions present similarly and extensive and detailed specialist investigations may be needed to differentiate one from the other.

Symptoms include dyspnoea and lethargy, although signs can be similar to congestive cardiac failure. They include oedema, ascites and hepatomegaly, and investigations include standard procedures such as ECG, chest X-ray and echocardiography.

Cardiac catheterisation may be required and endomyocardial biopsy may be considered if restrictive pathology is suspected, to differentiate restrictive pathology from pericardial constriction.

This differentiation is important, not just to establish the diagnosis, as the cardiomyopathy may not always be amenable to treatment whereas the constrictive pericarditis may be a more treatable condition.

If the diagnosis of constrictive pericarditis is confirmed then the likely treatment is surgical removal of the pericardium. However, if the patient has advanced cardiac disease this may be too risky a procedure.

  • Dr Brown is a GP in Leeds

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