First episode of ventricular fibrillation in an 84-year-old man with long-QT type 2 syndrome: A case report

Abstract

Congenital long QT syndrome (LQTS) is associated with ventricular arrhythmia and an increased risk of sudden cardiac death in young people. However, it is extremely rare for an elderly man to experience ventricular fibrillation (VF) due to congenital LQTS as a first episode. We describe the case of an 84-year-old man who experienced syncope after urination. He had a medical history of hypertension and asthma, but no history of syncope. Electrocardiographic findings in 2017 showed QT prolongation (corrected QT = 505 ms). No medication that could induce QT prolongation was administered. Blood test results on admission showed no electrolyte abnormalities, and there were no abnormal findings on echocardiography. The second episode of loss of consciousness occurred during hospitalization, and electrocardiography revealed incessant torsade de pointes, caused by R-on-T with short-long-short (SLS) sequences due to bradyarrhythmia. Coronary angiography did not detect myocardial ischemia, and an implantable cardioverter-defibrillator was implanted for secondary prevention. Genetic testing revealed a mutation of the KCNH2 gene, indicating LQTS type 2. In summary, we report a rare case of prolonged QT interval with SLS sequences due to sick sinus syndrome triggering VF as the first attack in an elderly patient with LQTS type 2.

<Learning objective: Physicians should be aware of the prolongation of QT as a cause of syncope in elderly patients and should pay attention to QT duration. Furthermore, patients with elderly-onset QT prolongation may have a genetic background associated with congenital long QT syndrome (LQTS); therefore, we should not hesitate to perform genetic testing in cases where LQTS is suspected in elderly patients.>

Introduction

Congenital long QT syndrome (LQTS) is a disorder of ventricular myocardial repolarization characterized by prolonged QT interval on the electrocardiogram (ECG), which can lead to ventricular arrhythmia and increased risk of sudden cardiac death in young people [1], [2]. The primary symptoms of LQTS include syncope, seizures, and cardiac arrest. The syndrome is associated with an increased incidence of torsade de pointes (TdP), a specific cardiac arrhythmia. While LQTS may be congenital or acquired [3], it is extremely rare for the elderly to experience ventricular fibrillation (VF) as the first episode of congenital LQTS. Herein, we report the case of an elderly man who presented with a first episode of loss of consciousness, which was attributed to TdP.

Case report

An 84-year-old man presented to our center with syncope following urination. He had been treated for hypertension and asthma for 18 years with amlodipine and budesonide, respectively, but no history of syncope was reported. There was no family history of ECG abnormalities, syncope, or sudden death. An ECG obtained 2 years before this episode showed a prolonged QT interval [corrected QT (QTc) = 505 ms]; however, because the patient was asymptomatic at that visit, he was not examined or treated. On admission, no medication that could induce QT prolongation was administered, blood test results revealed no electrolyte abnormalities, and there were no abnormal ECG findings, except for the QT prolongation (heart rate = 50 beats/min, QTc = 596 ms; Fig. 1A/Online Fig. 1). The patient experienced a second episode of loss of consciousness during hospitalization, and incessant TdP was observed on ECG, which was initiated by R-on-T with short-long-short (SLS) sequences due to bradyarrhythmia (Fig. 1B). A temporary pacemaker was implanted, and the coronary angiogram did not detect evidence of myocardial ischemia. Therefore, an implantable cardioverter-defibrillator (ICD) was implanted for secondary prevention. Bradycardia was considered the main cause of QT prolongation, and the pacemaker rate of the ICD was set at 80–130 beats/min. We measured the QT duration after ICD implantation at rates between 40 and 110 beats/min, with intervals of 10 beats/min. The QT/RR slope was calculated to be 0.23, which was considerably greater than that of healthy people [4]. The postoperative course was uneventful, and the patient was discharged as scheduled with a prescription of 5 mg/day of bisoprolol. One month after the ICD implantation, defibrillation due to VF was observed again on an intracardiac electrogram (Online Fig. 2); genetic analysis of KCNQ1, KCNH2, and SCN5A was then performed at the National Cerebral and Cardiovascular Center according to the Sanger sequencing method as described previously [2]. The results revealed the presence of an R744Ter mutation, corresponding to a mutation at the C-terminus (non-pore region) of the potassium channel encoded by the LQT2 gene, KCNH2 (Fig. 2A and B). The patient’s medication was switched from 5 mg/day of bisoprolol to 30 mg/day of nadolol. The follow-up period was 6 months, during which no defibrillation or asthma attack was observed. His family, including his son, daughter, and grandchild, underwent ECG examinations, which showed no prolonged QT at that time of examination (Fig. 3).

Fig. 1.

Electrocardiography and the occurrence of torsade de pointes.

(A) Electrocardiogram at rest showing prolonged QT interval. (B) Electrocardiogram showing incessant torsade de pointes, which was caused by the R-on-T phenomenon with short-long-short sequences due to sick sinus syndrome (heart rate = 50 beats/min, corrected QT = 596 ms).

PVC, premature ventricular complex.

Fig. 2.

Electropherogram of the sequence and topology of the KCNH2 gene.

(A) Genetic testing identified KCNH2 mutation (c.2230 C > T, p.R744Ter). (B) R744Ter was located at the C-terminus (arrow).

Fig. 3.

QTc duration of his family.

We have checked the electrocardiograms of his family, i.e. II-3, II-1, and III-1, and their QTc values were 404, 407, and 450, respectively.

Discussion

Congenital LQTS can be diagnosed based on ECG findings of QTc >480 ms, a family history of unexpected sudden death, syncopal episode, and TdP presence according to the 2011 LQTS criteria [5]. In the present case, QT prolongation was caused by the occurrence of the R-on-T phenomenon with SLS sequences due to sick sinus syndrome and ventricular premature complex. Consequently, the QT interval was further prolonged and induced TdP. It has been reported that this occurs when reentry is caused by an increase in repolarization variation [6].

Heart rate correction for calculating the QT interval may be inaccurate in cases of tachycardia or bradycardia. In contrast, the QT/RR analysis enables the evaluation of dynamic changes in the QT interval, because the heart rate is not corrected. Couderc et al. reported that the QT/RR slope was increased in LQTS. In the present case, the QT/RR slope was calculated to be 0.23, which was considerably higher than that of healthy individuals [4].

The incidence of fatal events is high among young people with congenital LQTS. A recent Japanese LQTS multicenter registry stated that the incidence of cardiac events in LQTS type 2 was higher among women >15 years than among men of the same age [2]. In that Japanese registry, 4 patients with LQTS type 2 with an R744Ter mutation were included (3 probands and 1 family), but all 3 proband participants were female patients aged <30 years old. Although a previous report described the case of a 71-year-old woman diagnosed with congenital LQTS, she experienced several syncopal attacks per year approximately 30 years previously [7]. Although there are some reports of fainting due to congenital LQTS in elderly women [8], [9], this is a rare case in an elderly man who experienced the first episode of VF due to congenital LQTS.

The onset of the first cardiac event in elderly patients might be caused by a genetic mutation in a non-pore location. In addition to genetic mutation, QT prolongation due to bradyarrhythmia can lead to TdP onset. During an outpatient follow-up, defibrillation due to VF was observed with bisoprolol administration. However, after switching the medication from bisoprolol to nadolol, no defibrillation was observed, suggesting the effectiveness of nadolol, as reported previously [10].

In conclusion, we presented a case of an elderly man with LQTS type 2 syndrome.

Conflict of interest

The authors declare that there is no conflict of interest.

Appendix A. Supplementary data

The following are Supplementary data to this article: