Long QT syndrome

Schwartz criteria (1993-2012 LQTS diagnostic criteria)[32]Schwartz PJ, Moss AJ, Vincent GM, et al. Diagnostic criteria for the long QT syndrome. An update. Circulation. 1993 Aug;88(2):782-4. http://www.ncbi.nlm.nih.gov/pubmed/8339437?tool=bestpractice.com ​​[33]Schwartz PJ, Crotti L. QTc behavior during exercise and genetic testing for the long-QT syndrome. Circulation. 2011 Nov 15;124(20):2181-4. https://www.doi.org/10.1161/CIRCULATIONAHA.111.062182 http://www.ncbi.nlm.nih.gov/pubmed/22083145?tool=bestpractice.com

The Schwartz criteria are diagnostic criteria for LQTS and are distinct from the criteria used to risk-stratify patients with known LQTS.

Points are assigned to ECG, clinical, and familial findings. Patients with 3.5 or more points have a high probability of having LQTS, those with 1.5 or 3 points have an intermediate probability, and those with 1 or no points have a low probability of having LQTS.

ECG findings (in the absence of medications or disorders known to affect these features)

• Corrected QT interval (QTc), defined as QT interval (in seconds) divided by the square root of the RR interval (in seconds):

  • ≥480 ms = 3 points

  • 460-479 ms = 2 points

  • 450-459 ms (in males) = 1 point

• QTc 4th minute of recovery from exercise stress test ≥480 ms = 1 point

• Torsades de pointes = 2 points

• Visible T-wave alternans = 1 point

• Notched T wave in 3 leads = 1 point

• Low heart rate for age (resting heart rate below the 2nd percentile for age) = 0.5 points.

Clinical history

• Syncope (cannot receive points for both syncope and torsades de pointes)

  • With stress = 2 points

  • Without stress = 1 point.

• Congenital deafness = 0.5 points.

Family history (the same family member cannot be counted for LQTS and sudden death)

• Family members with definite LQTS = 1 point

• Unexplained sudden cardiac death under age 30 years among immediate family = 0.5 points.