Short QT syndrome in a 14-year-old patient: The first pediatric case from Turkey.

Introduction

Short QT syndrome (SQTS) is a cardiac channelopathy associated with sudden cardiac death (SCD) and disposition to atrial-ventricular fibrillation (A-VF) (1). An accelerated ventricular repolarization (VR) abnormality develops in the heart due to an electrical stability disorder secondary to increased extracellular potassium flow in the heart (2, 3). Therefore, ventricular arrhythmias develop, which cause syncope, convulsion, and SD (2).

This paper presents a 14-year-old male patient whose elder brother and father had died because of SD and who presented to us with the complaint of syncope. He was identified to have a short QT interval (SQTI) in his electrocardiogram (ECG) result, diagnosed with SQTS following an electrophysiological study (EPS), and implanted with an implantable cardioverter defibrillator (ICD).

Case Report

The 14-year-old male patient presented to our center with the symptom of syncope. His elder brother was found dead after taking a bath (autopsy result negative), and his father was found dead while he was asleep. The physical examination, biochemical parameters, tele-cardiography, and echocardiography results of the patient were normal. The QT and QTc values were identified to be 310 msec and 320 msec in his ECG result, respectively (Fig.1a). After the family’s consent was received, in EPS, the patient had a QTc value of 323 msec and the values for the atrial-ventricular effective refractory period (AERP-VERP) pertaining to the SQTS were found to be short, i.e., 150 msec and 160 msec, respectively. It was observed that the patient easily entered AF based on a programmed stimuli delivered through the right atrium catheter (Fig.1b). The six-step ventricular tachycardia (VT) stimulation protocol was started in such a way that the ventricular catheter was placed first on the right ventricle (RV) apex and then on the RV outflow tract. Upon a triple stimulus at the RV apex, polymorphic VT and VF suddenly developed (Fig. 2a). The VF attack was terminated after the delivery of 100 joules of energy by the defibrillator. His SQTS diagnosis score of >4 (diagnosis score-7) were taken into account. A transvenous, single-chamber ICD was successfully implanted in the patient (Fig. 2b). The patient was started on Sotalol therapy; the result of the genetic study is awaited.

Figure 1

a, b. (a) Patient’s first ECG. Particularly, the short QTc (320 msec) and early repolarization pattern is remarkable (b) Induction of atrial fibrillation during EPS

Figure 2

a, b. (a) Induction of ventricular fibrillation during EPS (b) Patient’s telecardiogram after ICD implantation

Discussion

According to the HRS/EHRA/APHRS specialists’ consensus guide, SQTS diagnosis is made if the QTc value is ≤330 msec. If the QTc distance is measured as <360 msec for girls and as <350 msec for boys, it is diagnosed in the presence of one or more of the following conditions: pathogenic mutation, family history of SQTS, history of sudden death below the age of 40 years, and surviving a VT/VF episode without any cardiac diseases (3,4). During EPS, AERP and VERP are typically measured to be short. The AERP and VERP values of our patient were measured to be <160 msec.

It is recommended that an ICD can be implanted as a Class I indication in short QT syndrome patients, who have survived a cardiac arrest and have symptoms such as a documented spontaneous sustained VT attack with or without syncope. ICD implantation may be considered as a Class IIb indication in asymptomatic patients with a diagnosis of SQTS and a family history of SCD. Furthermore, quinidine and sotalol treatment may be considered as a Class IIb indication in asymptomatic patients with a diagnosis of SQTS and a family history of SCD (3, 4). Our case is the first pediatric case reported in Turkey, who was diagnosed with SQTS based on seven points in total according to the SQTS diagnostic criteria.

It is reported that genetic transmission is autosomal dominant and highly penetrative with SQTS. To date, seven different mutations have been defined. Some of these include patients associated with the overlapping effect of SQTS (Types 4–7) and Brugada syndrome (Types 3,4) (1, 3). The incidence of early repolarization is high with SQTS (1). Factors that reduce the QT value such as digoxin intake, hypercalcemia, use of androgens, and SQTI condition must be ruled out. There are also several publications indicating that there are no correlations between SQTI and life-threatening cardiac events (3, 5, 6). It is considered that SQTI is marked by the lack of a phenotypical expression, which is not associated with arrhythmia (5). Babaoğlu et al. (6) published a case report with asymptomatic SQTI where no arrhythmias could be induced during EPS.

Conclusion

EPS should be performed in selected SQTS cases. It is absolutely recommended that an ICD should be implanted in patients meeting the diagnostic criteria and requiring it. In addition, quinidine or sotalol treatment may be considered for necessary cases.