Background
- Prolonged ventricular re-polarisation = prolongation of the QT interval
- Risk of Torsade de pointes and sudden death
- Congenital or acquired
Acquired
- Class IA and III antiarrhythmics, TCAs, antihistamines.
- Phenothiazines (Haloperidol)111 ( and quinolone antibiotics).
- Electrolytes e.g. ↓K+ ↓Mg++, ↓Ca++.
- Cocaine ± myocardial ischaemia.
- Acute MI, hypothermia.
Congenital
- Romano-Ward syndrome - autosomal dominant.
- Lange-Nielsen syndrome - autosomal recessive (assoc congenital deafness.
- F > M, usually childhood or adolescence.
- Once identified, first degree relatives should be screened.
Normal QTc |
Prolonged QTc |
|
|---|---|---|
| Males or females <15 years old | <0.44 s |
>0.46 s |
| Males > 15 years | <0.43 s |
>0.45 s |
| Females > 15 years | <0.45 s |
>0.46 s |
Clinical Presentation
- Palpitations, syncope or near syncope, seizures, or cardiac arrest.
-
ECG findings
- QTc = QT/R-R-2. >0.45 sec abnormal
- Abnormal T-wave (notched or biphasic)
- T-wave alternans
Treatment
- "lifestyle modifications," (avoidance competitive sports and of all drugs known to prolong QT interval) (list).
- Treat with β-blockers (shorten the QT interval, reduce risk of Torsade and sudden death).
- High risk patients - implantable cardioverter-defibrillators (ICDs)
- Left cervicothoracic sympathectomy (block sympathetic to heart so reduce event rate).