When I started my training, if you had asked me what the QTc was, I would probably have told you it was one of those funny shopping channels on cable TV.
Then cisapride came along (Google it, kids) and changed all that. Nowadays every colleague who asks me to review an ECG tells me the QTc. In fact, in many cases, it’s the first thing I’m told about. Not the rhythm, or the rate, but the QTc.
If I’m feeling mischievous I’ll ask why they’ve measured the QTc and what normal is. This often gets met with a nervous shuffling of the ECG.
So to rectify this and avoid further awkward silences I decided to produce the infographic below  – attempting to summarise everything you need to know about prolonged QT in one handy picture.
Well, never was qtc this interesting, thanks Ian !
Thanks for the great infographic, Ian.
Keep in mind that in toxicology the QT interval in conjunction with the QT interval nomogram is now used to assess risk of drug-induced torsades de pointes given a lower false positive rate than QTc.
[1] Chan A, Isbister GK, Kirkpatrick CM, Dufful SB. Drug-induced QT prolongation and torsades de pointes: evaluation of a QT nomogram. QJM 2007;100(10):609-15
https://www.ncbi.nlm.nih.gov/pubmed/17881416
[2] Waring S, Graham A, Gray J, Wilson A, Howell C, Bateman N. Evaluation of a QT nomogram for risk assessment after antidepressant overdose. Br J Clin Pharmacol. 2010 Dec; 70(6): 881–885.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3014071/
Cheers
Pete