Testing for pulmonary hypertension

This short film explains what you can expect when are referred to the Royal Free Hospital for pulmonary hypertension testing (duration 5:32).

Six minute walking distance

The distance a person can walk in six minutes is a rough measure of a patient's cardiovascular fitness, although all sorts of other things, such as pain or weakness, can also affect the distance a person can walk. We regularly measure the six minute walking distance in the corridor behind our clinic. Generally speaking, a distance of over 500 metres is expected in healthy individuals.

NT-pro-BNP

This blood test measures a protein which is released by the heart in response to strain. Normal values are below 15pmol/l.

ECG

The ECG (electrocardiogram) is often normal in patients with pulmonary hypertension, but it may show signs of heart strain which can point towards the diagnosis. It also checks that the rhythm is regular and normal.

Echocardiography

Echocardiography utilises ultrasound to assess the heart. It can check the size of the chambers and how well each chamber is pumping. In pulmonary hypertension, the right sided chambers, the right atrium and the right ventricle, which pump blood through the lungs may become enlarged and pump less well over time.

Right heart catheterisation

This test is carried out as a day case in the Interventional Radiology and Cardiology Unit (“IRCU”) on the ground floor of the Royal Free Hospital. This is a well equipped and well staffed, purpose built facility where we perform all the right heart catheterisations. This is where we measure the pressure in the pulmonary arteries to check if a person has pulmonary hypertension and to assess how they are responding to treatment.

When you arrive, the nurses will show you to your bay where you can change into a hospital gown. They will run through a check list with you. The doctors will then come to explain the procedure in more detail and seek signed consent.

The procedure usually takes about 15-30 minutes. Some local anaesthetic is injected into the skin of the groin and a tube is inserted into the blood vessel. This initial bit can be uncomfortable but should not hurt much. After that, the procedure should be entirely pain free. Pressures are measured in the heart and pulmonary arteries.

Understanding the results of right heart catheterisation is complicated. First we measure the average “mean”) pressure in the pulmonary arteries. Normally this is under 20 millimetres of mercury (abbreviated “mmHg”). If it is above 25 there is pulmonary hypertension. However, pulmonary hypertension can occur for several reasons.

We always measure the backpressure from the left heart (“pulmonary capillary wedge pressure”). This should be under 15 mmHg. If it is higher than that, there may be some stiffness of the left heart.