Patient with syncope and “hidden” long QT syndrome

    Authors

    Keywords

    syncope, long QT sindrom, polymorphic ventricular tachycardia

    DOI

    https://doi.org/10.15836/ccar2018.340

    Full Text

    Introduction : Long QT syndrome (LQTS) is characterized by prolongation of the QT interval, with a QTc exceeding 480 ms and an increased risk for syncope and sudden cardiac death secondary to polymorphic ventricular tachycardia (VT). Genetic defects in either cardiac potassium, sodium or calcium channels are responsible for this syndrome. ( 1 ) Case report : 49-year-old patient without previous medical history was admitted to another hospital because of the syncope. On the day of admission, he felt palpitations and after which he transiently lost consciousness for 1-2 minutes. Initial ECG strip recorded short polymorphic tachycardia (5 QRS complexes, 250 beats per minute). Echocardiography and coronary angiography were both normal. During the hospitalization, he developed ventricular fibrillation and was successfully defibrillated. Amiodarone was introduced in therapy and he was transferred to our hospital for further workup. 12-lead ECG showed normal sinus rhythm with 1 premature ventricular contraction (PVC) originating from right ventricular outflow tract (RVOT). QTc interval was normal (433 ms) with prominent U waves and no signs of J wave syndromes. On 24-hours Holter monitoring, PVC burden was around 5%. Electrophysiologic study was performed, during isoproterenol infusion, QTc prolongation was observed (maximum QTc 555 ms). Therefore long QT syndrome was diagnosed. Combination of intermittently prolonged QTc interval and RVOT PVCs in this patient provoked polymorphic VT and cardiac arrest. After MRI which showed structurally normal heart, implantable cardioverter defibrilator (ICD) was implanted and the patient was discharged with low a dose of beta-blocker. In the follow-up PVC burden is increased to 10% and the patient became symptomatic, so ablation was scheduled. Conclusion : Right ventricular outflow tract PVCs in a structurally normal heart is considered a benign condition, but in some patient populations, they can be fatal, as proved in our case. In most cases of malignant right ventricular PVC-s, unrecognized arrhythmogenic right ventricular dysplasia is deemed responsible for mortality but we have to consider other possibilities. In this case, ablation of culprit PVCs can significantly lower the possibility of fatal arrhythmias and ICD discharges, but nevertheless permanent ICD therapy is still mandatory.

    Cardiologia Croatica
    Back to search

    Patient with syncope and “hidden” long QT syndrome

    Extended Abstract
    Issue11-12
    Published
    Pages340
    PDF via DOIhttps://doi.org/10.15836/ccar2018.340
    syncope
    long QT sindrom
    polymorphic ventricular tachycardia

    Authors

    Davor Radić*ORCIDUniversity Hospital Centre Zagreb, Zagreb, Croatia
    Borka Nikolić PezoORCIDUniversity Hospital Centre Zagreb, Zagreb, Croatia
    Richard MatasićORCIDUniversity Hospital Centre Zagreb, Zagreb, Croatia
    Mislav PuljevićORCIDUniversity Hospital Centre Zagreb, Zagreb, Croatia
    Miroslav KrpanORCIDUniversity Hospital Centre Zagreb, Zagreb, Croatia
    Davor PuljevićORCIDUniversity Hospital Centre Zagreb, Zagreb, Croatia
    Davor MiličićORCIDUniversity Hospital Centre Zagreb, Zagreb, Croatia
    Vedran VelagićORCIDUniversity Hospital Centre Zagreb, Zagreb, Croatia

    Full Text

    Introduction : Long QT syndrome (LQTS) is characterized by prolongation of the QT interval, with a QTc exceeding 480 ms and an increased risk for syncope and sudden cardiac death secondary to polymorphic ventricular tachycardia (VT). Genetic defects in either cardiac potassium, sodium or calcium channels are responsible for this syndrome. ( 1 ) Case report : 49-year-old patient without previous medical history was admitted to another hospital because of the syncope. On the day of admission, he felt palpitations and after which he transiently lost consciousness for 1-2 minutes. Initial ECG strip recorded short polymorphic tachycardia (5 QRS complexes, 250 beats per minute). Echocardiography and coronary angiography were both normal. During the hospitalization, he developed ventricular fibrillation and was successfully defibrillated. Amiodarone was introduced in therapy and he was transferred to our hospital for further workup. 12-lead ECG showed normal sinus rhythm with 1 premature ventricular contraction (PVC) originating from right ventricular outflow tract (RVOT). QTc interval was normal (433 ms) with prominent U waves and no signs of J wave syndromes. On 24-hours Holter monitoring, PVC burden was around 5%. Electrophysiologic study was performed, during isoproterenol infusion, QTc prolongation was observed (maximum QTc 555 ms). Therefore long QT syndrome was diagnosed. Combination of intermittently prolonged QTc interval and RVOT PVCs in this patient provoked polymorphic VT and cardiac arrest. After MRI which showed structurally normal heart, implantable cardioverter defibrilator (ICD) was implanted and the patient was discharged with low a dose of beta-blocker. In the follow-up PVC burden is increased to 10% and the patient became symptomatic, so ablation was scheduled. Conclusion : Right ventricular outflow tract PVCs in a structurally normal heart is considered a benign condition, but in some patient populations, they can be fatal, as proved in our case. In most cases of malignant right ventricular PVC-s, unrecognized arrhythmogenic right ventricular dysplasia is deemed responsible for mortality but we have to consider other possibilities. In this case, ablation of culprit PVCs can significantly lower the possibility of fatal arrhythmias and ICD discharges, but nevertheless permanent ICD therapy is still mandatory.