QT interval
Jump to navigation
Jump to search
Introduction
Interval between the beginning of the ECG QRS complex (beginning of ventricular depolarization) to the begining of the T wave (beginning of ventricular repolarization).
Genetics
- polymorphism in NOS1AP influences the QT interval
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
Additional terms
References
- ↑ Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 151
- ↑ Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
- ↑ 3.0 3.1 Prescriber's Letter 8(4):19 2001
- ↑ UpToDate 14.1 http://www.utdol.com
- ↑ 5.0 5.1 Kenigsberg DN et al, Prolongation of the QTc interval is seen uniformly during early transmural ischemia. J Am Coll Cardiol 2007, 49:1299 PMID: https://www.ncbi.nlm.nih.gov/pubmed/17394962
- ↑ 6.0 6.1 Geriatric Review Syllabus, 9th edition (GRS9) Medinal-Walpole A, Pacala JT, Porter JF (eds) American Geriatrics Society, 2016