Arrhythmias & electrophysiologyCohort study
Circadian pattern of ventricular fibrillation-terminating shocks among patients with diagnosed and treated congenital long QT syndrome
- retrospective study
Authors' conclusion
VF in LQTS, mainly driven by LQT1, is not uniformly distributed throughout the day but concentrates in a mid-afternoon "torsadogenic window." These results align with a previously published "QT clock" and circadian activity of ion channel expression and may influence future management.
Study context
- Population
- Long QT syndrome (LQTS) patients with an implantable cardioverter-defibrillator (ICD) evaluated from 1999 to 2025 in the Mayo Clinic Windland Smith Rice Genetic Heart Rhythm ClinicLQTS patients with an ICD, 224 were female, mean implant age 21 ± 15 years · LQT1 96 · LQT2 161 · LQT3 64
- Participants
- 321 patients
- Exposure
- LQT1 vs LQT2 vs LQT3
- LQT1n = 96
- LQT2n = 161
- LQT3n = 64
Main finding
As reported in the abstract
VF-terminating shocks
Patients who experienced ventricular fibrillation (VF)-terminating shocks
85 patients (26%)
VF-terminating shocks
199
Observational data: associations, not effects.
Further findings
| Outcome | LQT1 | LQT2 | LQT3 |
|---|---|---|---|
| Circadian clustering by genotype (Rayleigh test) | Z = 10.9; P < .001 | Z = 1.2; P = .3 | Z = 7; P < .001 |
- Circadian clustering by genotype (Rayleigh test): LQT3 clustering not maintained by per-patient analysis
Circadian timing of VF-terminating shocks
- 2-harmonic regression predominance of events
- 15:01 (LRT = 30.6; P < .001)
- Rayleigh test clustering
- 14:58 (Z = 14.1; P < .001)
- Per-event and per-patient analysis demonstrated clustering in the midafternoon
- per-patient analysis correcting for patients with many events
Activity analysis
- Similar clustering for times of events for daily and exercise/stress-related activities
Original publication
Circadian pattern of ventricular fibrillation-terminating shocks among patients with diagnosed and treated congenital long QT syndrome. Heart Rhythm. Published 6 July 2026. doi:10.1016/j.hrthm.2026.07.002
Summarised from the published abstract; every number is checked against it