Share this Article
Singapore Med J 2014; 55(12): 607-612; http://dx.doi.org/10.11622/smedj.2014172
Importance of QT interval in clinical practice
Ambhore A, Teo SG, Omar AR, Poh KK
Correspondence: A/Prof Poh Kian Keong, kian_keong_poh@nuhs.edu.sg
ABSTRACT
Long QT interval is an important finding that is often missed by electrocardiogram interpreters. Long QT syndrome (inherited and acquired) is a potentially lethal cardiac channelopathy that is frequently mistaken for epilepsy. We present a case of long QT syndrome with multiple cardiac arrests presenting as syncope and seizures. The long QTc interval was aggravated by hypomagnesaemia and drugs, including clarithromycin and levofloxacin. Multiple drugs can cause prolongation of the QT interval, and all physicians should bear this in mind when prescribing these drugs.
Keywords: causes, diagnosis and management, ECG, long QT interval, torsade de pointes
Singapore Med J 2014; 55(12): 607-612; http://dx.doi.org/10.11622/smedj.2014172
REFERENCES
| 1. Bazett HC. An analysis of time relations of the electrocardiogram. Heart 1920; 7:353-70. | ||||
| 2. Fridericia LS. The duration of systole in an electrocardiogram in normal humans and in patients with heart disease. 1920. Ann Noninvasive Electrocardiol 2003; 8:343-51. http://dx.doi.org/10.1046/j.1542-474X.2003.08413.x | ||||
| 3. Sagie A, Larson MG, Goldberg RJ, Bengtson JR, Levy D. An improved method for adjusting the QT interval for heart rate (the Framingham Heart Study). Am J Cardiol 1992; 70:797-801. http://dx.doi.org/10.1016/0002-9149(92)90562-D | ||||
| 4. Malik M. Problems of heart rate correction in assessment of drug-induced QT prolongation interval. J Cardiovasc Electrophysiol 2001; 12:411-20. http://dx.doi.org/10.1046/j.1540-8167.2001.00411.x | ||||
| 5. Moss AJ. Measurement of the QT interval and the risk associated with QTc interval prolongation: a review. Am J Cardiol 1993; 72:23B-25B. http://dx.doi.org/10.1016/0002-9149(93)90036-C | ||||
| 6. Jervell A, Lange-Nielsen F. Congenital deaf-mutism, functional heart disease with prolongation of the QT interval and sudden death. Am Heart J 1957; 54:59-68. http://dx.doi.org/10.1016/0002-8703(57)90079-0 | ||||
| 7. Romano C, Gemmer G, Pongiglione R. [Rare cardiac arrythmias of the pediatric age. II. Syncopal attacks due to paroxysmal ventricular fibrillation (presentation of 1st case in italian pediatric literature)]. Clin Pediatr 1963; 45:656-83. Italian. | ||||
| 8. Ward OC: A new familial cardiac syndrome in children. J Ir Med Assoc 1964; 54:103-106. PMid:14136838 | ||||
| 9. Splawski I, Shen J, Timothy KW, et al. Spectrum of mutations in long-qt syndrome genes. KVLQT1, HERG, SCN5A, KCNE1, and KCNE2. Circulation 2000; 102:1178-85. http://dx.doi.org/10.1161/01.CIR.102.10.1178 | ||||
| 10. Schwartz PJ, Priori SG, Spazzolini C, et al. Genotype-phenotype correlation in the long-QT syndrome: gene-specific triggers for life-threatening arrhythmias. Circulation 2001; 103:89-95. http://dx.doi.org/10.1161/01.CIR.103.1.89 | ||||
| 11. Priori SG, Schwartz PJ, Napolitano C, et al. Risk stratification in the long-QT syndrome. N Engl J Med 2003; 348:1866-74. http://dx.doi.org/10.1056/NEJMoa022147 | ||||
| 12. Napolitano C, Priori SG, Schwartz PJ, et al. Genetic testing in the long QT syndrome: development and validation of an efficient approach to genotyping in clinical practice. JAMA 2005; 294: 2975-80. http://dx.doi.org/10.1001/jama.294.23.2975 | ||||
| 13. Zhang L, Timothy KW, Vincent GM, et al. Spectrum of ST-T-wave patterns and repolarization parameters in congenital long-QT syndrome: ECG findings identify genotypes. Circulation 2000; 102:2849-55. http://dx.doi.org/10.1161/01.CIR.102.23.2849 | ||||
| 14. Priori SG, Napolitano C, Schwartz PJ, et al. Association of long QT syndrome loci and cardiac events among patients treated with beta-blockers. JAMA 2004; 292:1341-4. http://dx.doi.org/10.1001/jama.292.11.1341 | ||||
| 15. Zipes DP, Camm AJ, Borggrefe M, et al. ACC/AHA/ESC 2006 guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: a report of the American College of Cardiology/American Heart Association Task force and the European Society of Cardiology Committee for practice guidelines. J Am Coll Cardiol 2006; 48: e247-346. http://dx.doi.org/10.1016/j.jacc.2006.07.010 | ||||
| 16. Al-Khatib SM, Allen LaPionte N, Kramer JM, Califf RM. What clinicians should know about the QT interval? JAMA 2003; 289:2120-7. http://dx.doi.org/10.1001/jama.289.16.2120 | ||||
| 17. Yap YG, Camm AJ. Drug induced QT prolongation and torsades de pointes. Heart 2003; 89:1363-72. http://dx.doi.org/10.1136/heart.89.11.1363 | ||||
| 18. Coumel P, Leclercq JF, Lucet V. Possible mechanisms of the arrhythmias in long QT syndrome. Eur Heart J 1985; 6 Suppl D:115-29. | ||||
| 19. Nguyen PT, Scheinman MM, Sege J. Polymorphous ventricular tachycardia: clinical characterization, therapy and the QT interval. Circulation 1986; 74:340-9. http://dx.doi.org/10.1161/01.CIR.74.2.340 | ||||
| 20. Sclarovsky S, Strasberg B, Lewin RF, Agmon J. Polymorphous ventriculartachycardia: clinical features and treatment. Am J Cardiol 1979; 44:339?44. http://dx.doi.org/10.1016/0002-9149(79)90326-6 | ||||
| 21. Kay GN, Plumb VJ, Arciniegas JG, Henthorn RW, Waldo AL. Torsade de pointes: the long-short initiating sequence and other clinical features: observations in 32 patients. J Am Coll Cardiol 1983; 2:806-17. http://dx.doi.org/10.1016/S0735-1097(83)80226-5 | ||||
| 22. Darpo B. Spectrum of drugs prolonging QT interval and the incidence of torsades de pointes. Eur Heart J Supplements 2001; 3(suppl K):S70-S80. http://dx.doi.org/10.1016/S1520-765X(01)90009-4 | ||||
| 23. Taylor DM. Antipsychotics and QT prolongation. Acta Psychiatr Scand 2003; 107:85-95. http://dx.doi.org/10.1034/j.1600-0447.2003.02078.x | ||||
| 24. Haddad PM, Anderson IM. Anti-psychotic related QTc prolongation, torsades de pointes and sudden death. Drugs 2002; 62:1649-71. http://dx.doi.org/10.2165/00003495-200262110-00006 | ||||
| 25. Woosley RL. Drugs that prolong the QT interval and/or induce torsades de pointes. Revised November 18, 2014 [online]. Available at: www.QTdrugs.org. Accessed November 30, 2014. | ||||
| 26. Khan IA. Long QT syndrome: diagnosis and management. Am Heart J 2002; 143:7-14. http://dx.doi.org/10.1067/mhj.2002.120295 | ||||
| 27. Tzivoni D, Banai S, Schuger C, et al. Treatment of torsade de pointes with magnesium sulfate. Circulation 1988; 77:392-7. http://dx.doi.org/10.1161/01.CIR.77.2.392 | ||||