ECG

An ECG or electrocardiogram is a way of evaluating the electrical activity of the heart. It is regularly used and can detect many heart abnormalities at the bedside. However, it takes time to learn how to interpret in and a systematic approach is helpful. ECG physics is more complicated and is on a seperate page.

Basics

If you want more detail than this, see ECG physics but this is what you can probably get away with in terms of physiology. The ECG is split into big boxes, each made of 5x5 little boxes. Each little box is 1mm (big box is 5mm). Going across the page, you have time, down the page you electrical activity. In terms of time:

• 1 little box (1mm) - 0.04ms
• 1 big box (5mm) - 0.2s

In terms of electrical activity:

• 1 little box (1mm) - 0.1mV
• 1 big box (5mm) - 0.5mV

These numbers come in useful later. Essentially, the normal ECG looks like this:

Rate and rhythm

Rate is relatively easy to measure. As long as the rhythm is regular, you can simply divide the number of big boxes between each QRS complex