A population-based study of trends in cardiac arrest and sudden death owing to long QT syndrome

Population-based data on long QT syndrome (LQTS) are lacking. New Zealand has a national LQTS registry, molecular autopsy program, and standardized investigation of resuscitated cardiac arrest (RSCA).

This study aimed to describe trends in LQTS detection and presentation with RSCA/sudden cardiac death over 24 years.

Review of data on registry participants who underwent genetic testing for LQTS presenting between 2000 and 2023.

Among 915 diagnosed as having LQTS, 378 probands with a mean corrected QT interval of 512 ± 52 ms presented with sudden cardiac death (26 of 378; 7%), RSCA (82; 21%), syncope or seizure (122; 32%), and incidental/other (148; 40%). Causative genetic variants were found in 165 of 378 probands (44%): 98 KCNQ1 (59%), 41 KCNH2 (25%), 7 SCN5A (4%), and 19 other genes (12%). 593 of 915 participants (65%) were on therapy (beta blocker [565; 62%], implantable cardioverter-defibrillator [134; 16%], and/or left cardiac sympathetic denervation [69; 8%]). 3 likely arrhythmic deaths (0.3%) and 23 appropriate implantable cardioverter-defibrillator shocks (3%) occurred during follow-up (median 12 years). Detections of LQTS/population were 0.5 of 100,000 in 2000, 1.6 of 100,000 in 2009, and 0.4 of 100,000 in 2023. Presentation with RSCA decreased by 10%/y from 2007. Presentation with death decreased by 22%/y from 2014 (P = .026), with no deaths from 2019 to 2023.

Decreasing rates of LQTS detection in recent years suggest that most cases have been discovered in New Zealand. Decreasing cardiac arrest and sudden death owing to LQTS is likely related to the success of the overall program.