Tachycardias are viewed by many as the most challenging of ECGs. This is mainly because the mechanism may be difficult to determine and because there may be a lot of information on a single tracing. A systematic approach makes interpretation a lot more easy. The following chapters include almost all known tachycardias and we aim to deliver short and concise answers to increase your understanding. This to make sure that the next time you see a tachycardia in the clinic, you won’t develop one yourself!