Arrhythmias & electrophysiology
Circadian pattern of ventricular fibrillation-terminating shocks among patients with diagnosed and treated congenital long QT syndrome
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
- Outcome
- VF-terminating shocks
Main finding
As reported in the abstract
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.
Summarised from the published abstract; every number is checked against it