The apex beat is the outermost and lowermost position that you can feel the heart beating - the most inferior and lateral point of cardiac impulse. It's actually where you can feel the heart beating most clearly, and it's a really useful point of reference.
The actual beat which you can feel is the very tip of the left ventricle pushing against the chest wall as the left ventricle contracts and the heart is pushed against it. As you feel the apex beating it should be in time with the carotid pulse (if it's not, you're probably not feeling the apex beat or the pulse correctly!)
Normally the apex beat is in the 5th intercostal space in the mid-clavicular line on the left side. (If it can't be found here, it doesn't always suggest something is wrong; it might be that the patient is too fat for you to be able to feel it - this is certainly and clearly true in morbidly obese patients; there's also the possibility that everything is the opposite way round in that patient's chest, such that they have what is known as dextrocardia).
As with the pulse and the JVP, the apex beat has a character, which means sometimes it can have particular features which can make it stand out. In the same way that you might be able to recognise someone because of their outgoing or shy character, you can recognise certain illnesses or conditions from the character of the apex beat.
- A double impulse should cause you to wonder what's going on, because it's inevitably not normal! It's one of those signs which should make you think straight away of a particular disease: in this case, hypertrophic cardiomyopathy.
- A sustained apex happens when the heart is enlarged or working hard to pump blood out, so you'll feel the impulse for longer than you normally would expect to. This happens in left ventricular hypertrophy (or enlargement), aortic stenosis, hypertrophic cardiomyopathy or hyperkinesia.
- A forceful apex beat might suggest that the circulation is particularly excited or 'hyperdynamic'. This happens in lots of situations, such as when there is a widespread infection throughout the body (sepsis) or when there aren't enough red blood cells (anaemia).
- A tapping apex - this is the name given when you can feel the apex beat but it's not quite the same as normal. The subtle difference is that you can feel a slight tapping, which is actually where you're actually feeling the first heart sound. This happens in mitral stenosis, when the high pressure system causes the mitral valve to be shut sharply - imagine the heart aggressively banging the door shut in frustration because it's not opening properly.
If the apex beat is more difficult to feel, then it could be normal (as mentioned above), or it could be because there's some kind of problem. A 'diffuse' apex beat is where it's difficult to locate exactly where you feel it, and this will happen if the left ventricle starts to balloon out (a left ventricular aneurysm). It can also be hard - or impossible - to feel the beat if the patient is overweight, has emphysema, fluid around the heart, or if the heart isn't beating in the first place!! And for the purpose of medical exams, it's always worth remembering dextrocardia, where the thorax is flipped around - which means you won't feel the heart on the left anyway.