Discussion

The short QT syndrome is a recently defined gene-related arrhythmogenic syndrome, which was described as a new electrocardiographic pattern associated with atrial and ventricular tachyarrhythmias in structurally normal heart due to pathological shortening of duration of action potential. The age of onset of the disease is highly variable like the clinical manifestations which ranges from asymptomatic to recurrent syncope and sudden cardiac death which may be the first symptom of the disease. Electrocardiography is the primary tool for diagnosis but electrocardiogram findings may be easily ignored especially among children because the shortness of the QT interval becomes apparent only at heart rates less than 80 beats/minute. The diagnostic criteria for short QT syndrome are a QTc ≤ 330 ms usually accompanied by characteristic tall, peaked T-waves and with an interval from J point to T wave peak (Jp-Tp) measured in the precordial lead with the T wave of greatest amplitude <120 ms.^{Reference Campuzano, Sarquella-Brugada, Cesar, Arbelo, Brugada and Brugada4} Besides a short QT interval, a PQ depression of more than 0.5 mm was recently determined to be a novel marker for short QT syndrome because it rarely appears in healthy patients.^{Reference Wakatsuki, Iso and Mase5}

The annual risk of cardiac arrest among patients in the largest short QT syndrome cohort to date was approximately 1%, and most of the cardiac arrests reported in this cohort occurred during rest or sleep. On the other hand, unlike long QT syndrome, patients with short QT syndrome rarely experience cardiac arrest during emotional stress or physical effort.^{Reference Hammond-Haley, Patel, Providencia and Lambiase6} The prevalence of a QTc < 320 ms was reported as 0.1% in a diverse young British population including athletes and among the few individuals who did have a QTc of <320 ms, none experienced any adverse events, syncope, or sudden death over a mean follow-up period of 5.3 years.^{Reference Dhutia, Malhotra and Parpia7} To the best of our knowledge, this is the first children reported with an aborted sudden cardiac arrest during sport activity in a previously asymptomatic short QT syndrome patient with negative family history. The first and only reported case of sudden cardiac arrest during exercise in a previously asymptomatic short QT syndrome patient with negative family history was a 22-year-old male who collapsed while running in the early evening after work.^{Reference Wakatsuki, Iso and Mase5}

Although there is no definitive consensus on the treatment of patients with short QT syndrome, the current guidelines recommend an implantable cardiac defibrillator as the first and most effective therapeutic measure in patients who have experienced sustained ventricular tachycardia/ventricular fibrillation episodes or in survivors of an aborted cardiac arrest.^{Reference Tristani-Firouzi8} Inappropriate shock is a common complication in short QT syndrome patients carrying an implantable cardioverter defibrillator because of tall and peaked T waves. In our case, implantable cardioverter defibrillator was implanted due to aborted cardiac arrest and the day after implantation the patient had an episode of ventricular tachycardia with a rate 230 of beats/minute; it was ceased by anti-tachycardia pacing. Although our patient had a total of four episodes of non-sustained ventricular tachycardia throughout 1 year of follow-up, all of the episodes were ceased on its own and there were no inappropriate shocks.

As a conclusion, patients with short QT syndrome rarely experience cardiac arrest during emotional stress or physical effort. Because electrocardiography findings may be easily ignored especially among children due to higher resting heart rates, short QT syndrome should be kept in mind in any cases with palpitation, syncope, aborted cardiac arrest and family history of sudden cardiac death. Increased awareness of short QT syndrome may be lifesaving in these patients.