What is LQTS?
Long QT syndrome (LQTS) is delayed ventricular repolarization, seen as a prolonged QT on ECG, predisposing to torsades de pointes, syncope, seizures, or sudden cardiac arrest. It can be congenital (channelopathies such as LQT1–3) or acquired (medications, low K+/Mg2+/Ca2+, ischemia, hypothermia, severe bradycardia).
Rule of thumb In men, QTc > 470 ms is prolonged; > 500 ms is clearly abnormal/high‑risk and merits urgent clinical correlation.
Do leadless pacemakers cause LQTS?
No. Leadless pacemakers (e.g., Aveir VR, Micra) do not cause LQTS. RV pacing widens QRS and can make the measured QT appear longer, but the repolarization problem of LQTS isn’t created by the pacemaker. In paced rhythms, clinicians often assess JT (QT − QRS) or use pacing-aware formulas. Pacemakers may even be protective in congenital LQTS by preventing pauses/bradycardia that can trigger torsades.
Why “avoid swimming” in LQT1? Is rowing the same?
Swimming
In LQT1 (KCNQ1 / IKs), adrenergic surges markedly prolong repolarization. Swimming combines cold water immersion + intense exertion + emotional/startle stress — a signature trigger for malignant arrhythmias in LQT1.
Rowing
Rowing is vigorous and adrenergic, so risk isn’t zero in LQT1, but it lacks the cold-shock/startle element. It is not the “classic” trigger. Decisions are individualized with therapy (e.g., beta‑blockers) and shared decision‑making.
Swimming vs Rowing by Subtype
| Subtype | Main trigger(s) | Swimming | Rowing |
|---|---|---|---|
| LQT1 (KCNQ1 / IKs) | Adrenergic exercise; especially in water | 🚨 High risk — classic trigger | ⚠️ Moderate risk — adrenergic stress without cold shock |
| LQT2 (KCNH2 / IKr) | Startle, sudden noise, postpartum | ⚠️ Risk present but not signature | ⚠️ Similar to other intense sports |
| LQT3 (SCN5A / Na+) | Rest, sleep, bradycardia | ✅ Usually low risk during exercise | ✅ Not a typical trigger |
Your ECG & QTc Numbers
Office 12‑lead ECG shows sinus bradycardia (~50 bpm). Visually measured QT ≈ 530 ms (lead II / V5). Using HR ≈ 50 bpm (RR ≈ 1200 ms):
| Formula | Equation | QTc |
|---|---|---|
| Bazett | QT / √(RR) | 484 ms |
| Fridericia | QT / (RR)^(1/3) | 485 ms |
| Hodges | QT + 1.75 × (HR − 60) | 513 ms |
At low heart rates, Bazett can underestimate; Fridericia/Hodges are preferred. Your true QTc likely sits around 490–510 ms (borderline-to-prolonged).
What to Discuss with Your Cardiologist
- Re‑measure QT and QTc on a calibrated 12‑lead ECG (consider averaging ≥3 beats in II/V5).
- Check electrolytes: K+, Mg2+, Ca2+; replete to high‑normal.
- Review all medications/supplements against a trusted QT‑risk list.
- Consider Holter or exercise ECG to assess dynamic QT behavior.
- Discuss sports participation (e.g., rowing) under therapy (often beta‑blockers) and shared decision‑making.
Clinician Handover Note
Patient: 71y. Current ECG: sinus bradycardia ~50 bpm; QRS narrow; measured QT ≈ 530 ms in II/V5. QTc: Bazett 484 ms; Fridericia 485 ms; Hodges 513 ms. Interpretation: QTc borderline–prolonged (likely 490–510 ms in bradycardia). Please correlate with meds, electrolytes, and phenotype/family history; consider ambulatory/exercise testing and pacing-aware repolarization assessment (JT if paced).
Safety & Red Flags
- Syncope during exercise/startle/rest (subtype‑specific) or seizure‑like episodes with rapid recovery.
- Family history of sudden death < 40–50 years.
- QTc persistently > 500 ms or torsades de pointes.
Emergency: If you experience chest pain, severe palpitations, fainting, or seizure‑like activity, seek emergency care immediately.