Short QT syndrome medical therapy
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]
Overview
The efficacy of pharmacotherapy in preventing ventricular fibrillation has only been studies in patients with SQT1. Given the limited number of patients studied, and the limited duration of follow-up, pharmacotherapy as primary or secondary preventive therapy for patients with SQT1 cannot be recommended at this time. AICD implantation remains the mainstay of therapy in these patients. Pharmacotherapy may play an adjunctive role in reducing the risk of events in patients with an AICD as described below in the indications section.
Patients with Short QT Syndrome 1 (SQT1) have a mutation in KCNH2 (HERG). Class IC and III antiarrhythmic drugs do not produce any significant QT interval prolongation [1][2] . Flecainide has not been shown to consistently reduce the inducibility of ventricular fibrillation.[3] Although it does not prolong the QT interval in SQT1 patients, propafenone reduces the risk of recurrent atrial fibrillation in SQT1 patients.[4]
Quinidine in contrast may be effective in patients with SQT1 in so far as it blocks both potassium channels (IKr, IKs, Ito, IKATP and IK1) and the inward sodium and calcium channels. In four out of four patients, Quinidine prolonged the QT interval from 263 +/- 12 msec to 362 +/-25 msec, most likely due to its effects on prolonging the action potential and by virtue of its action on the IK channels. Although Quinidine was successful in preventing the inducibility of ventricular fibrillation in 4 out of 4 patients, it is unclear if the prolongation of the QT interval by quinidine would reduce the risk of sudden cardiac death.
Although pharmacotherapy can be used to suppress the occurrence of atrial fibrillation in patients with SQT1, AICD implantation is the mainstay of therapy, and pharmacotherapy to prevent sudden death should is only indicated if AICD implantation is not possible.
Among patients with SQT1, Qunidine also:
- Prolongs the ST segment and T wave durations
- Restores the heart rate dependent variability in the QT interval
- Decreases repolarization dispersion
Indications for Pharmacologic Therapy
The following are indications for pharmacologic therapy of SQTS[5]:
- In children as an alternate to AICD implantation
- In patients with a contraindications AICD implantation
- In patients who decline AICD implantation
- In patients with appropriate AICD discharges to reduce the frequency of discharges
- In patients with atrial fibrillation to reduce the frequency of symptomatic episodes
References
- ↑ Gaita F, Giustetto C, Bianchi F, Schimpf R, Haissaguerre M, Calo L, Brugada R, Antzelevitch C, Borggrefe M, Wolpert C. (2004). "Short QT syndrome: pharmacological treatment". J Am Coll Cardiol. 43 (8): 1494–1499. doi:10.1016/j.jacc.2004.02.034. PMID 15093889.
- ↑ Wolpert C, Schimpf R, Giustetto C, Antzelevitch C, Cordeiro J, Dumaine R, Brugada R, Hong K, Bauersfeld U, Gaita F, Borggrefe M (2005). "Further insights into the effect of quinidine in short QT syndrome caused by a mutation in HERG". Journal of Cardiovascular Electrophysiology. 16 (1): 54–8. doi:10.1046/j.1540-8167.2005.04470.x. PMC 1474841. PMID 15673388. Retrieved 2012-09-03. Unknown parameter
|month=ignored (help) - ↑ Gaita F, Giustetto C, Bianchi F, Schimpf R, Haissaguerre M, Calò L, Brugada R, Antzelevitch C, Borggrefe M, Wolpert C (2004). "Short QT syndrome: pharmacological treatment". Journal of the American College of Cardiology. 43 (8): 1494–9. doi:10.1016/j.jacc.2004.02.034. PMID 15093889. Retrieved 2012-09-03. Unknown parameter
|month=ignored (help) - ↑ Bjerregaard P, Gussak I. Atrial fibrillation in the setting of familial short QT interval. Heart Rhythm 2004; 1: S165 (abstract).
- ↑ Moreno-Reviriego S, Merino JL.Short QT Syndrome. An article from the E-Journal of the ESC Council for Cardiology Practice. Vol9 N°2, 17 Sep 2010 [1]