MRCP revision battle 7.1: cardiac action potentials

I've got that Friday feeling so I've decided to indulge in a cardiology fest.  Today's revision battles will therefore be:

MRCP revision battle 7.1: cardiac action potentials
MRCP revision battle 7.2: the Vaugham-Williams classification system
MRCP revision battle 7.3: long QT
MRCP revision battle 7.4: adenosine
MRCP revision battle 7.5: cause of the broad complex tachycardia

Now I know that may look like a lot but quite a few of the battles are short and almost sweet, so lets get stuck in!




MRCP revision battle 7.1: cardiac action potentials


Understanding the basics of the cardiac action potential is essential to grasp how antiarrhythmic drugs work.  The basic cardiac action potential looks like this:

                                                                                                            thanks to http://commons.wikimedia.org for the image

In stage 0, there is a rapid influx of sodium
Stage 1 is then an efflux of potassium, followed by
Stage 2, which is an influx of calcium.  Finally in
Stage 3 the efflux of pottasium continues, terminating the action potential.


Try and keep this image in mind as we move on to the fabulous world of Vaughan-Williams classification...