Heart murmurs in adults – part 1

What does it mean when the heart is making extra sounds? If your doctor hears an extra blowing sound, should we be worried? Acclaimed cardiologist Dr Allan Harkness is here to answer all questions in the first part of his series on heart murmurs in adults.

What sound does a heart make?

When a doctor listens to your heart, normally there are two distinct sounds that are heard – the lub-dub of a heartbeat.

Your heart has veins carrying blood into its chambers and arteries taking the blood out and round your body. There are four valves in the heart that make sure the blood only flows in one direction. One pair of valves closing is associated with the lub sound and the second pair closing makes the dub sound.

Heart sounds can alter in heart disease – for example, if the pumping action is weak, the valves are damaged or the pressure inside the heart increases. A poorly heart can sometimes have extra sounds, called third and fourth heart sounds.

What are heart murmurs?

Heart murmurs are extra sounds coming from the heart in addition to the normal heart sounds. An efficient heart makes little extra noise, like a well-oiled machine. Blood flows smoothly from the veins to the chambers and then to the arteries. Extra sounds suggest turbulence.

What causes heart murmurs?

Some people just have a noisy heart. This is more common in children and young adults. A soft, quiet murmur may be picked up incidentally when a doctor listens and further tests, such as an echocardiogram, will show the heart is quite normal. These are called innocent or physiological murmurs.

There are three main causes of murmurs that signify heart disease:

1. Blood leaking backward

Heart valves are very good at preventing blood from leaking backward. When a valve is abnormal, it can let a lot of blood flow backward. This leaking causes a blowing noise. When the mitral or tricuspid valves leak, the noise is like a long “Shhh” – as you might make at children being noisy at the cinema. When the aortic or pulmonary valves leak, the noise is like a short sigh – like the satisfied “Ahhh” you might make after slipping into a warm bath.

2. Blood struggling to flow forward

Heart valves can become thickened and hardened over many years. This can restrict the blood flow through them. Some people are born with abnormal valves that are more prone to thickening than others.

The commonest valve to become thickened is the aortic valve. A normal aortic valve opens with a hole about the size of a pound coin. A severely narrowed valve could have a hole smaller than a shirt button.

When the aortic valve becomes narrowed, blood flowing through it makes a coarse noise, like clearing your throat.

In the last century, rheumatic fever was common in the UK and this would often cause narrowing of the aortic or mitral valves. Rheumatic fever is still seen in other countries, such as in Eastern Europe or Africa. A narrowed mitral valve causes a low rumbling noise which can be difficult to hear.

In a condition called hypertrophic cardiomyopathy, the heart muscle becomes thickened and blood can struggle to flow out of the heart into the aorta – in effect, when the heart pumps it simultaneously strangles itself. This murmur is a harsh blowing noise.

3. Blood flowing between two heart chambers when it shouldn’t

This is usually due to a gap in the walls of the heart chambers that was present at birth – a congenital heart defect. These are often corrected when the patient is still a baby or child.

Some holes do not put the heart under strain and can be left – the commonest of these is a ventricular septal defect (VSD). This is a hole between the two bottom chambers of the heart. A small hole can make a very loud blowing noise.

Occasionally congenital heart defects are picked up later in life, for instance at a work medical.