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Long QT syndrome . Katie DePlatchett, M.D. AM Report April 7, 2010. Long QT Syndrome (LQTS). QT interval = beginning of the QRS to the end of the T wave duration of activation and recovery of the ventricular myocardium. Bazett formula: QT/ square root of RR > 440 msecs in men
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Long QT syndrome Katie DePlatchett, M.D. AM Report April 7, 2010
Long QT Syndrome (LQTS) • QT interval = beginning of the QRS to the end of the T wave • duration of activation and recovery of the ventricular myocardium. • Bazett formula: QT/ square root of RR • > 440 msecs in men • > 460 msecs in women
Long QT Syndrome (LQTS) • Disease of the ion channels • Prolongation of the action potential • Early after depolarization* • Increased sympathetic activity • Imbalance in sympathetic innervation of heart
Acquired • Metabolic (HypoK, HypoMg, HypoCal, Anorexia, Hypothyroidism) • Medications Antiarrhythmics (sotalol, amiodarone, etc) Antibiotics (Macrolides, Fluoroquinolones) Psychotropic (Haldol, TCAs, Thioridazine) SSRIs, Risperidone, Methadone, Droperidol, protease inhibitors
Acquired • Myocardial Ischemia or Infarction • Intracranial disease • Hypothermia • HIV
Congenital • h/o syncope, family h/o SCD, deafness • 7 genetic defects • Important for identifying arrhythmia triggers • LQT1 = exercise-related • LQT2 = auditory stimuli • LQT3 = at rest or sleep; no benefit from BB • Most cases discovered after syncope or arrest
Treatment • Primary Prevention • Beta blockers • Avoidance of strenuous activity/sports • Left cardiac sympathetic denervation • Secondary Prevention • Beta blockers • ICD • Avoidance of QT prolonging agents
Back to our patient… • Discharge with life vest & beta blocker • Repeat Echocardiogrm = normal EF • Genetic testing: LQT1 + LQT9 mutations • LQT1 = EXERCISE RELATED!!! • No more novice marathon training. • s/p ICD placement • No Family History of SCD
REFERENCES • Schwartz, PJ. The long QT syndrome. Curr Probl Cardiol 1997; 22:297. • Zipes, DP, et al. ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias & Prevention of SCD. J. Am Coll Cardiol 2006; 48; 1064. • Priori, SG, et al. Association of long QT syndrome loci and cardiac events among patients treated with beta-blockers. JAMA 2004; 292;1341. • UpToDate