Congenital LQTS is a disease resulting from impaired expression or dysfunctions of cardiac ion channels as a result of their encoding gene variants. It can cause the prolongation of QT intervals and, as a consequence, result in life threatening events such as VFs. Itoh et al. reported that 28% of acquired LQTS patients were actually “congenital” [
8]. Moreover, only 60% of patients show symptoms prior to the diagnosis of congenital LQTS [
9]. Given that our patient was asymptomatic until the operation, it is presumable that stimulating factors related to perioperative and postoperative procedures or the use of medicines strongly contributed to the event of postoperative TdP followed by VFs. The factors associated with fatal arrhythmias for acquired LQTS are medicines including anesthetic agents, inotropes, hypokalemia, bradycardia, emotional stress, hypothermia and the combinations of these factors [
8,
10]. If we had known that the patient had a genetic background of CACNA1C mutations, some of which were reported as cardiac-only Timothy syndrome, we could have avoided potential factors that triggered malignant TdP and VFs [
5‐
7,
10]. In order to prevent malignant arrhythmias postoperatively, some authors have recommended the use of appropriate premedications, avoidance of hypothermia, proper anesthetic agents, adequate pain relief, continuous use of beta blockers during and after operations, avoidance of the excess use of diuretics, and maintenance of proper level of electrolytes such as calcium and magnesium [
3,
4,
10,
11]. In our case, sevoflurane, propofol, dopamine and dexmedetomidine were used for anesthesia and postoperative care, and these were categorized as possible cause of arrhythmic events or should be avoided in CredibleMeds (
https://www.crediblemeds.org/). If the diagnosis was made preoperatively, these possible unsafe drugs could not have been used and, as a result, the patient could not have experienced the refractory VFs in the ICU.
The congenital LQTS is often overlooked and difficult to recognize before the occurrence of arrhythmic events, especially in patients with congenital heart diseases, as in our case. However, preoperative diagnosis of this syndrome is essential as it may help physicians to avoid arrhythmic factors [
1,
2,
12]. Diagnostic difficulty is due to the fact that patients with LQTS and ASDs occasionally show a RBBB preoperatively or after surgical correction of tetralogy of Fallot, and this ECG abnormality can mask the prolonged QT time [
1]. It has also been reported that QT interval is prolonged after surgical correction of ASD in 42% of patients due to increased coronary flow after the correction [
13]. Thus, physicians should carefully evaluate patients’ family medical history, especially when they present RBBB and a strong family history of arrhythmias. It is important to note that Schwartz and Moss score can help medical practitioners to diagnose the LQTS, even in the absence of genetic screening for LQTS [
14,
15].