Understanding ECGs: Minding your Ps and Qs
- By: Dominic Cox, Hamish Dougall
- Published: 01 October 2001
- DOI: 10.1136/sbmj.0110374
- Cite this as: Student BMJ 2001;09:357–398
In the second article in our series Dominic Cox and Hamish Dougall discuss what you need to learn and what you need to understand
In this series of articles on electrocardiograms (ECGs) we hope to convey the basic concepts of reading and using this simple clinical tool. We re-emphasise that a grasp of only a few rudimentary concepts will allow all of us, not just the cardiologists, to understand the majority of clinically important ECGs. In the first article we explained how the heart works as an engine and outlined the power supply (coronary arteries), control (electrical supply), and how that in an ECG, the electrical supply is recorded as it moves across the heart by a series of detectors placed strategically around the body.
An ECG is a two dimensional recording of a three dimensional process. A cardiac electrical impulse does not travel in a single direction down a