Received 21 April 2016; accepted 13 June 2016; published 16 June 2016
Long QT syndrome (LQTS) is an uncommon cardiac disorder of repolarization leading to prolonged QT interval and T-wave abnormalities on the ECG, thus predisposing to Torsades de Pointes (TdP) and sudden cardiac death  . A study by Schwartz et al.  reported the prevalence of LQTS to be 1 in 2000 people. Pseudo 2:1 AV block when sinus intervals are shorter than the ventricular refractory period has been reported with long QT syndrome (LQTS)  , but only few reports of acquired complete heart block, and few reports of congenital complete heart block with prolonged QT interval  -  .
2. Case Report
We report a 29-year-old gentleman, with positive family history of sudden cardiac death, and no cardiac symptoms before, who presented to our center with syncope, his ECG showed complete heart block with an escape
Figure 1.Showing complete heart block,prolonged QT interval and deep T wave inversion in pericardial leads and one spike of failed temporary pacing.
Figure 2.Showing the polymorphic ventricular tachycardia induced by PVC.
Figure 3.Showing shortening of the QT interval after pacing with complete suppression of the arrhythmia.
rhythm of wide QRS, at a rate of 35 beats per minutes, We had no previous records of the patient as he has recently arrived to the country but this was his first time to have such a complaint, inpatient work up did not reveal any reversible cause of complete heart block, his QT interval was prolonged (QT 680 ms, QTc bazett method 534 ms, QTc Hodges method 640 ms) (we used the Hodges method because the patient was tachycardiac after DDD pacing as the bazett method would overestimate the corrected QT when the patient heart rate above 110 BPM  ), with deep T wave inversion in the precordial leads (Figure 1). On telemetry he started to have recurring polymorphic ventricular tachycardia which was initiated by a premature ventricular beat (Figure 2) and led to loss of consciousness. A temporary pacemaker was inserted which suppressed the arrhythmia and led to shortened QT. His echocardiogram, serum electrolyte including potassium and coronary angiogram were normal. A permanent dual chamber pacemaker was implanted the following day with higher basal rate (Figure 3) and the patient was started on beta blocker. QT and QTc were significantly reduced after permanent pacing (QT 400 ms QTc bazett 573 ms (overestimated as heart rate is 119 BPM), QTc Hodges 503 ms)  . He remained arrhythmia free and discharged in good condition. At six weeks follow up the patient was seen doing well, without symptoms or recorded arrhythmia, and normal pacemaker function.
The ventricular tachyarrhythmia that underlies the cardiac events of LQTS is Torsades-de-Pointes, a curious type of ventricular tachycardia that most of the time is self-limiting and produces transient syncope but that can also degenerate into ventricular Fibrillation and cause cardiac arrest or sudden death  . The association of acquired complete heart block and long QT interval in literature is quite rare, only few reports about congenital complete heart block and long QT interval   . Indik  had also reported a similar case study of a 65-years old female who developed dizziness and found to have complete heart block with QT interval of 800 ms and markedly abnormal T wave. She was demonstrated to have episodes of TdP on Holter monitoring. After insertion of the pacemaker, the T-waves normalized and QT interval shortened and arrhythmia suppressed. It is generally accepted that in the long QT syndrome, the irritability of the ventricle increases due to the exaggerated dispersion of ventricular repolarization and unilateral changes in sympathetic tone of the heart (functional distribution of right and left stellate innervation to the ventricles). The appearance of polymorphous ventricular tachycardia mostly of the torsade de pointes type can frequently be detected in the syndrome of QT prolongation. Contrary to congenital complete heart block, the acquired complete heart block can have more frequent attacks of loss of conscious. In our work, we went in agreement with other authors  -  that pacing shortened the QT interval and prevented the provocation of the torsade de pointes. In searching for the etiology of our condition, a study by Kurita et al.  investigated fourteen patients with complete atrioventricular block. They demonstrated that there was significant prolongation of the QT and QTc intervals among patients with complete heart block who developed TdP as compared to those who did not develop TdP: 753 ± 57.5 vs 635 ± 78.4 ms (p < 0.01) and 585 ± 44.8 vs 476 ± 58.3 ms (p < 0.01) which might point to the mechanism of arrhythmia in our case.
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