Arrhythmias & electrophysiology
Polymorphic ventricular tachycardia, ischaemic ventricular fibrillation, and torsade de pointes: importance of the QT and the coupling interval in the differential diagnosis
Authors' conclusion
The coupling interval helps discriminate between polymorphic VT that occurs despite a long QT interval (pseudo-TdP) and polymorphic arrhythmias striking because of a long QT (true TdP).
Study context
- Population
- Patients with polymorphic ventricular tachycardia (VT) events with available onset305 polymorphic VT events
- Participants
- 190 patients
- Exposure
- Pseudo-TdP vs polymorphic VT with normal QT vs true TdP
- Pseudo-TdPn = 32
- True TdPn = 53
- Ischaemic ventricular fibrillation (VF)n = 50
- Outcome
- ECG characteristics: QTc and coupling interval of the ectopic beat triggering the arrhythmia
Main finding
As reported in the abstract
| Group | QTc | Coupling interval |
|---|---|---|
| Pseudo-TdP | 491.4 ± 25.2 ms | 359.1 ± 38.1 ms |
| Polymorphic VT with normal QT | 447.3 ± 55.6 ms | 356.6 ± 39.4 ms |
| True TdP | 564.6 ± 75.6 ms | 581.2 ± 95.3 ms |
QTc
Pseudo-TdP491.4 ± 25.2 ms
Polymorphic VT with normal QT447.3 ± 55.6 ms
True TdP564.6 ± 75.6 ms
Coupling interval
Pseudo-TdP359.1 ± 38.1 ms
Polymorphic VT with normal QT356.6 ± 39.4 ms
True TdP581.2 ± 95.3 ms
- Pseudo-TdP vs Polymorphic VT with normal QT: P < 0.001 — QTc longer
- Pseudo-TdP vs True TdP: P < 0.001 — QTc shorter
- Pseudo-TdP vs Polymorphic VT with normal QT: P = 0.467 — coupling interval similar
- Pseudo-TdP vs True TdP: P < 0.001 — coupling interval much shorter
Observational data: associations, not effects.
Original publication
Polymorphic ventricular tachycardia, ischaemic ventricular fibrillation, and torsade de pointes: importance of the QT and the coupling interval in the differential diagnosis. Eur Heart J. Published 10 March 2021. doi:10.
Summarised from the published abstract; every number is checked against it