/QTc (Corrected QT)

QTc (Corrected QT)

Corrects QT interval for heart rate (Bazett)

QT Interval
msec
Heart Rate
bpm

Total Score

0

Normal QTc interval.

0–440+Low
441–460+Moderate
461–499+High
500–999+High

Disclaimer: The clinical scoring and algorithms on this platform are intended strictly for professional informational purposes. They do not constitute a definitive medical diagnosis, treatment, or clinical decision. The final judgment and responsibility lie with the treating physician.

Yasal Uyarı: Bu platformdaki klinik skorlamalar ve algoritmalar yalnızca sağlık profesyonellerini bilgilendirme amaçlıdır. Herhangi bir kesin tıbbi teşhis, tedavi veya klinik karar yerine geçemez. Nihai karar ve sorumluluk hastayı yatak başında değerlendiren hekime aittir.

Clinical Overview

The QT interval represents electrical depolarization and repolarization of the ventricles. Because the QT interval naturally shortens at faster heart rates, it must be 'corrected' (QTc) to evaluate whether repolarization is pathologically prolonged. A prolonged QTc (>450 ms in men, >470 ms in women) significantly increases the risk of early afterdepolarizations and Torsades de Pointes (TdP).

Clinical Pearl

Bazett's formula is the most widely reported on standard EKG machines, but it overcorrects at fast heart rates (tachycardia) and undercorrects at slow heart rates. In patients with severe tachycardia (>100 bpm), the Fridericia or Framingham formulas are generally more accurate for assessing true repolarization risk.

Pitfalls & Warnings

  • Measurement should ideally be taken in Lead II or V5-V6, and the maximum QT interval observed should be used.
  • In the presence of a wide QRS (e.g., LBBB), the QTc is artifactually prolonged. Various algorithms (like the Rautaharju formula or subtracting 50 ms) must be applied to estimate the true repolarization time.

Academic References

Rautaharju PM, Surawicz B, Gettes LS, et al. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part IV: the ST segment, T and U waves, and the QT interval. J Am Coll Cardiol. 2009;53(11):982-991.

Vandenberk B, Vandael E, Robyns T, et al. Which QT Correction Formulae to Use for QT Monitoring?. J Am Heart Assoc. 2016;5(6):e003264.

Disclaimer: The clinical scoring and algorithms on this platform are intended strictly for professional informational purposes. They do not constitute a definitive medical diagnosis, treatment, or clinical decision. The final judgment and responsibility lie with the treating physician.