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QT prolongation

Prolongation of the electrocardiogram QT interval. Etiology: 1) pharmaceutical agents (see drug-induced QT prolongation) 2) electrolyte disturbances a) hypokalemia b) hypomagnesemia 3) endocrine disorders a) hypothyroidism b) hypoparathyroidism c) pheochromocytoma d) hyperaldosteronism 4) intracranial disorders a) subarachnoid hemorrhage b) stroke c) encephalitis d) head trauma 5) nutritional disorders a) liquid protein diet b) starvation Epidemiology: 1) women are predisposed to QT prolongation 2) the QT interval is generally longer in women than men [3] Special laboratory: - electrocardiogram - a normal QTc is < 0.44-0.46 msec - a QTc of > 500 msec is considered QTc prolongation [6] Complications: - QTc prolongation predisposes to torsades de pointes - QTc prolongation identifies hospitalized patients with increased risk of mortality [4] Management: - avoid or discontinue pharmaceutical agents that prolong the QT interval

Related

electrocardiogram (ECG, EKG) long QT syndrome QT interval

Specific

drug-induced prolongation of the QT interval

General

sign/symptom

References

  1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 151
  2. Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 17, 18. American College of Physicians, Philadelphia 1998, 2012, 2015, 2018.
  3. Prescriber's Letter 8(4):19 2001
  4. Haugaa KH et al. Institution-wide QT alert system identifies patients with a high risk of mortality. Mayo Clin Proc 2013 Apr; 88:315. PMID: 23541006 - Mizusawa Y and Wilde AAM. QT prolongation and mortality in hospital settings: Identifying patients at high risk. Mayo Clin Proc 2013 Apr; 88:309. PMID: 23541004
  5. Drew BJ, Ackerman MJ, Funk M et al Prevention of torsade de pointes in hospital settings: a scientific statement from the American Heart Association and the American College of Cardiology Foundation. Circulation. 2010 Mar 2;121(8):1047-60. PMID: 20142454
  6. Geriatric Review Syllabus, 9th edition (GRS9) Medinal-Walpole A, Pacala JT, Porter JF (eds) American Geriatrics Society, 2016
  7. Trinkley KE, Page RL 2nd, Lien H, Yamanouye K, Tisdale JE. QT interval prolongation and the risk of torsades de pointes: essentials for clinicians. Curr Med Res Opin. 2013 Dec;29(12):1719-26. Review. PMID: 24020938