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QT interval

Interval between the beginning of the ECG QRS complex (beginning of ventricular depolarization) to the begining of the T wave (beginning of ventricular repolarization). Reference interval: - QT interval varies inversely with heart rate. - QTc is the QT interval corrected for the heart rate - normal QTc is < 0.44-0.46 msec - a QTc of > 500 msec is considered QTc prolongation [6] Clinical significance: - the QT interval is generally longer in women than men [3] thus women are predisposed to QT prolongation - QTc prolongation preceeds ST segment elevation with transmural myocardial ischemia & infarction. [5] - QTc prolongation predisposes to torsades de pointes Genetics: - polymorphism in NOS1AP influences the QT interval

Related

long QT syndrome QT prolongation torsades de pointes

Database Correlations

OMIM 610141

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, American College of Physicians, Philadelphia 1998
  3. Prescriber's Letter 8(4):19 2001
  4. UpToDate 14.1 http://www.utdol.com
  5. Kenigsberg DN et al, Prolongation of the QTc interval is seen uniformly during early transmural ischemia. J Am Coll Cardiol 2007, 49:1299 PMID: 17394962
  6. Geriatric Review Syllabus, 9th edition (GRS9) Medinal-Walpole A, Pacala JT, Porter JF (eds) American Geriatrics Society, 2016