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. 2021 May 26;108(5):332–338. doi: 10.1136/heartjnl-2020-318259

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© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY. Published by BMJ.

This is an open access article distributed in accordance with the Creative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits others to copy, redistribute, remix, transform and build upon this work for any purpose, provided the original work is properly cited, a link to the licence is given, and indication of whether changes were made. See: https://creativecommons.org/licenses/by/4.0/.

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Schematic representation of the effects of genetic and environmental factors in LQTS. (A) LQTS-associated mutation causes prolongation of the QT interval on the ECG. (B) Environmental factors such as certain drugs (which decrease repolarisation reserve) or hypokalaemia, or genetic factors (ie, deleterious alleles) act in a conjoint manner with the LQTS-associated mutation to further prolong the QT interval. (C) Protective alleles counteract the effects of the mutation and reduce the extent of QT prolongation. The presence of deleterious and/or protective alleles may underlie, at least partially, the variable expressivity in LQTS. LQTS, long QT syndrome.