Abstract 13743: A Tale of Syncope, Prolonged QT and ICD

Abstract

Introduction: Long QT syndrome (LQTS) was first described in the 1960s. It manifests clinically as syncope, cardiac arrest or sudden cardiac death. LQTS can be caused by 15 different genes. These mutations lead to action potential prolongation by causing impaired repolarizing currents. Case Discussion: A 29-year-old previously healthy Caucasian woman was admitted after recurrent episodes of syncope that happened within 1-month prior to the presentation. She was hemodynamically stable with normal vitals. Her ECG showed normal sinus rhythm with corrected QT (QTc) of 598ms. In the ED, she suffered an episode of sustained monomorphic ventricular tachycardia (VT) and underwent cardioversion. She was started on amiodarone infusion. Serial ECGs showed prolonged QTc. She had another episode of pulseless VT that terminated without defibrillation. She was transferred to our facility for further care. Her family history was significant for paternal aunt who had died unexpectedly at the age of 39. All her lab work including electrolytes, thyroid panel, cardiac enzymes, inflammatory markers and extended drug screen was unrevealing. Transthoracic echocardiogram showed normal biventricular size and function. Decision making: She was started on propranolol for possible LQTS. Cardiac MR did not show any evidence of structural abnormalities. Genetic panel was sent. Since myocarditis or familial LQTS could not be ruled out, we proceeded with implantable cardioverter defibrillator (ICD) implantation for secondary prevention. She was discharged home on nadolol. Conclusion: In the absence of genetic information, LQTS can be diagnosed in symptomatic patients with QTc >480msec on serial ECGs after excluding secondary causes. Schwartz score comprising of ECG findings, symptoms, clinical & family history is diagnostic when greater than 3.5. Beta-blockers are indicated in all patients with a clinical diagnosis. Patients must avoid any QT prolonging agents and strenuous exercise. An ICD is indicated in patients who suffered cardiac arrest. ICD may also be considered for primary prevention in high risk patients.