Background Short QT syndrome ( SQTS ) is a rare inheritable disease associated with sudden cardiac death. Data on long‐term outcomes of families with SQTS are limited. Methods and Results Seventeen patients with SQTS in 7 independent families (48% men; median age, 42.4 years; corrected QT interval, 324.9±40.8 ms) were followed up for 13.5±2.5 years. A history of sudden cardiac death was documented in 71% of families. A large number of them showed sudden cardiac deaths at a younger age, with a predominance of men (67%). Five patients had syncope (29%) and 9 (53%) had atrial fibrillation or atrial flutter. An SQTS ‐related gene was found in 76% of the patients as follows: KCNH 2 ( SQTS 1) in 4, CACNA 1C ( SQTS 4) in 3, and CACN b2 ( SQTS 5) in 6. Five patients (29%) received an implantable cardioverter‐defibrillator and 5 patients received long‐term prophylaxis with hydroquinidine. During follow‐up, 1 patient received an appropriate implantable cardioverter‐defibrillator shock attributable to ventricular fibrillation. The patient received no further implantable cardioverter‐defibrillator shocks after treatment with hydroquinidine. Conclusions The risk of sudden cardiac death in SQTS families is high. However, after appropriate risk assessment and individualized treatment options (hydroquinidine and/or implantable cardioverter‐defibrillator), the long‐term outcome is relatively benign when patients are seen at a reference center.

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Short QT syndrome (SQTS) is associated with sudden cardiac arrest. There are limited data on the impact of antiarrhythmic drugs on the outcome of SQTS. Materials and Methods: We studied data that describe the clinical outcome of 62 SQTS patients treated with antiarrhythmic drugs, who were recruited from a pool of patients diagnosed in our institution and also from known databases after a systematic search of the published literature. Results: Sixty-two SQTS patients treated with antiarrhythmic drugs were followed up over a median timeframe of 5.6 years (interquartile range 1.6–7.7 years). Six patients, in particular, received multiple drugs as a combination. Of the 55 patients treated with hydroquinidine (HQ), long-term prophylaxis was documented in 41 patients. Fourteen patients stopped treatment due to the following reasons: gastrointestinal intolerance (n = 4), poor compliance (n = 8), and no QTc prolongation (n = 2). Of the 41 patients treated with HQ, the QTc interval increased from 313.5 ± 17.2 to 380.1 ± 21.2 ms. Thirteen of the 41 patients suffered from at least one or more ventricular tachyarrhythmias (VAs) before HQ initiation. VAs are reduced in incidence after HQ treatment (13/41: 31% versus 3/41: 7.3%, p < 0.001). Conclusion: HQ increases the corrected QT interval and prevents VAs in the majority of the patients in this cohort. HQ is safe for use in SQTS patients, particularly due to its low rate of side effects. Other antiarrhythmic drugs might be useful, but the data justifying their use are sparse.