SQTS

Auteur: Louise R.A. Olde Nordkamp Supervisor: Arthur A.M. Wilde

The short QT syndrome is a very rare syndrome characterized by an abnormally short QT interval and increased risk of ventricular fibrillation and cardiac death.

Clinical diagnosis

The diagnosis is based on the presence a short QT interval, in which the upper limit is mostly set on 330 ms. Males are more often affected than women. A history of cardiac arrest is present in one-third. Patients are at risk for both atrial arrhythmias (AF) and ventricular arrhythmias (VT/VF).

Physical examination

Patients can present with symptoms of arrhythmias:

• Out-of-hospital-cardiac-arrest
• Syncope, pre-syncope (weakness, lightheadedness, dizziness)

ECG tests

The ECG demonstrates a corrected QT interval significantly below the limit of normal (<330 ms). Additionally, notable ECG findings are the presence of a sharp T-wave beginning at the end of the QRS complex, preceded by a brief or absent ST-segment. Exercise electrocardiographic studies in SQTS patients also characteristically reveal a non-physiologic lack of QT shortening at increased heart rates.

Genetic diagnosis

In a quarter of the patients a mutation is found, predominantly in the KCNH2 gene (SQTS1). This gain-of-function mutation causes an increase in the potassium efflux and, subsequently, to a decrease of the myocyte refractory period. Mutations in the KCNQ1, KCNJ2 and possibly CACNxxx genes are also associated with the SQTS.

Risk Stratification

Risk stratification in SQTS is still ill-defined and should be done by a specialized cardio-genetic cardiologist.

Treatment

Hydroquinidine is suggested for normalization of the QT interval in patients with a KCNH2 mutation. ICD therapy is advised in SQTS patients for secondary prevention of sudden cardiac death and could be considered

References

1. Giustetto C, Di Monte F, Wolpert C, Borggrefe M, Schimpf R, Sbragia P, Leone G, Maury P, Anttonen O, Haissaguerre M, and Gaita F. Short QT syndrome: clinical findings and diagnostic-therapeutic implications. Eur Heart J. 2006 Oct;27(20):2440-7. DOI:10.1093/eurheartj/ehl185 |
2. Giustetto C, Schimpf R, Mazzanti A, Scrocco C, Maury P, Anttonen O, Probst V, Blanc JJ, Sbragia P, Dalmasso P, Borggrefe M, and Gaita F. Long-term follow-up of patients with short QT syndrome. J Am Coll Cardiol. 2011 Aug 2;58(6):587-95. DOI:10.1016/j.jacc.2011.03.038 |
3. Patel C, Yan GX, and Antzelevitch C. Short QT syndrome: from bench to bedside. Circ Arrhythm Electrophysiol. 2010 Aug;3(4):401-8. DOI:10.1161/CIRCEP.109.921056 |