Short QT syndrome
- Charles Antzelevitch, PhD, FACC, FAHA, FHRS
Charles Antzelevitch, PhD, FACC, FAHA, FHRS
- Professor and Executive Director, Cardiovascular Research Program
- Lankenau Institute of Medical Research, Wynnewood, PA
- Jonathan M Cordeiro, PhD
Jonathan M Cordeiro, PhD
- Research Scientist
- Masonic Medical Research Laboratory
Short QT Syndrome (SQTS) is an inherited channelopathy (disorder which affects the movement of ions through channels with the cell membrane) associated with marked shortened QT intervals and sudden cardiac death (SCD) in individuals with a structurally normal heart. In contrast to long QT syndrome, another channelopathy, ion channel defects associated with SQTS lead to abnormal abbreviation of repolarization, predisposing affected individuals to a risk of atrial and ventricular arrhythmias. (See "Pathophysiology of the long QT syndrome".)
Since its first report in 2000, significant progress has been made in defining the genetic and cellular basis of SQTS as well as in therapeutic approaches to treating this syndrome. SQTS is a genetically heterogeneous disease with six different genes encoding various cardiac ion channels thus far identified. Data regarding genotype-phenotype correlation and genotype-specific treatment are promising but limited, primarily due to the lack of clinical cases.
The clinical presentation, diagnostic approach, and treatment modalities for SQTS will be discussed here. SCD and other channelopathies are discussed separately. (See "Overview of sudden cardiac arrest and sudden cardiac death" and "Clinical features of congenital long QT syndrome".)
HISTORICAL BACKGROUND, INITIAL REPORT, AND DEFINITION
In 1993, it was first proposed that shorter than normal QT intervals (<400 msec) are associated with a 2.4-fold increased risk for SCD . An abnormally short QT interval observed before and after runs of VT/VF has been reported anecdotally [2,3]. Interestingly, certain species of kangaroo, known to have a high incidence of SCD, display an abnormally short QT interval as a normal feature on their electrocardiogram (ECG) [4,5].
SQTS was first described as a clinical entity in a report of four patients with extremely short QT intervals in association with paroxysmal atrial fibrillation and SCD . In 2003, another study further described SQTS in two unrelated European families (six patients total) with a strong family history of sudden death in association with short QT interval on ECG . Since then, over 100 cases of SQTS have been reported, and the existence of this novel channelopathy has been validated.
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- HISTORICAL BACKGROUND, INITIAL REPORT, AND DEFINITION
- PREVALENCE OF A SHORT QT INTERVAL
- GENETIC BASIS
- CELLULAR BASIS OF ARRHYTHMOGENESIS
- CLINICAL PRESENTATION
- Initial presentation by SQTS subtype
- DIAGNOSTIC EVALUATION
- Electrocardiographic findings
- Electrophysiological study
- Genetic testing
- Diagnostic criteria
- Screening family members
- DIFFERENTIAL DIAGNOSIS
- Normal variant
- Acquired causes of short QT interval
- Deceleration-dependent shortening of the QT interval
- MANAGEMENT OF PATIENTS WITH A SHORT QT INTERVAL
- Patients with an isolated short QT interval
- Patients with a short QT interval who have a high probability of SQTS
- - Implantable cardioverter-defibrillator (ICD)
- - Pharmacological therapy
- SUMMARY AND RECOMMENDATIONS