QTc and LQTS Score

QT corrections (QT and QTc in ms; RR in seconds = 60 / HR)

Bazett       QTc = QT / RR^(1/2)
Fridericia   QTc = QT / RR^(1/3)
Framingham   QTc = QT + 154 x (1 - RR)      [Sagie 1992: QT + 0.154 (1 - RR), all in seconds]
Hodges       QTc = QT + 1.75 x (HR - 60)    [HR in beats/min]
All four equal QT at RR = 1 s (HR 60).

• Framingham: Sagie et al., 5,018 Framingham Heart Study adults aged 28–62 (abstract retrieved). Its constant 0.154 is in seconds; mixing seconds and milliseconds gives a near-zero correction.
• Hodges: formula as printed in Phan 2015. The original Hodges 1983 abstract was not retrieved [unverified as to original wording].
• Bazett and Fridericia are the standard exponent forms (Phan 2015 describes them as QT/RR^e, e = 0.5 and 0.33). The 1920 originals were not retrieved.

Pediatric reference context

• Phan 2015 (702 children ≤6 y, mean age 26 months, mean HR 122 bpm): Bazett gave the most consistent correction across heart rates (QTc-RR slope −0.019). A Bazett QTc >460 ms was 2 SD above the mean; the matching values were 414 ms (Fridericia) and 443 ms (Hodges). The page shows these only for age ≤6 years.
• Phan's Framingham value (353 ms) is not shown: its Framingham QTc values (overall low of 217 ms) could not be reconciled with the Sagie formula in seconds.
• Saarel 2018 (PHN, 2,400 healthy children, digital ECGs): QTc in lead II differed by sex and race; from age 3 years girls' mean QTc (Bazett) was 5–10 ms longer than boys'; under 3 years the 98th percentile reached 464 ms in one race group. Its age, sex and race tables are not reproduced here (AHA copyright).
• Formula choice changes "prolonged": state the formula with any QTc you report.

Schwartz score (Schwartz & Crotti 2011, Table 2: "1993–2011 LQTS Diagnostic Criteria")

• ECG findings count only "in the absence of medications or disorders known to affect these electrocardiographic features". The same family member cannot be counted in both family items.
• Score: ≤1 point low probability; 1.5 to 3 points intermediate; ≥3.5 points high probability of LQTS.
• The 4th-minute recovery item was added in 2011; the editorial adopted a 480 ms cut-off (the source study, Sy et al., found an optimal cut-off of 445 ms). The 1993 version (Schwartz, Moss, Vincent, Crampton) did not include it.
• When TdP and syncope are both ticked, this page counts the higher-scoring of the two (an interpretation of "mutually exclusive").
• "Low heart rate for age" needs an age-specific heart-rate reference that this page does not provide.

Verification

Checked in October 2026: Bazett, Fridericia, Framingham and Hodges agree with MDCalc’s published formulas to 1 ms in 32 of 32 cases (heart rate 42 to 200 bpm, entered as rate or RR). The Schwartz score agrees with the MSD Manual Professional table in 8 of 8 combinations (points and category). MDCalc’s live code was not available, so its published formula text was the comparator.

References

• Phan DQ, Silka MJ, Lan YT, Chang RK. Comparison of formulas for calculation of the corrected QT interval in infants and young children. J Pediatr 2015;166(4):960-964.e2. doi:10.1016/j.jpeds.2014.12.037 (full text, PMC4380641)
• Sagie A, Larson MG, Goldberg RJ, Bengtson JR, Levy D. An improved method for adjusting the QT interval for heart rate (the Framingham Heart Study). Am J Cardiol 1992;70(7):797-801. doi:10.1016/0002-9149(92)90562-d
• Schwartz PJ, Crotti L. QTc behavior during exercise and genetic testing for the long-QT syndrome. Circulation 2011;124(20):2181-2184. doi:10.1161/CIRCULATIONAHA.111.062182 (Table 2)
• Schwartz PJ, Moss AJ, Vincent GM, Crampton RS. Diagnostic criteria for the long QT syndrome: an update. Circulation 1993;88(2):782-784. doi:10.1161/01.cir.88.2.782 (not retrieved)
• Saarel EV, Granger S, Kaltman JR, et al. Electrocardiograms in healthy North American children in the digital age. Circ Arrhythm Electrophysiol 2018;11(7):e005808. doi:10.1161/CIRCEP.117.005808
• Rautaharju PM, Surawicz B, Gettes LS, et al. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram, part IV. Circulation 2009;119(10):e241-e250. doi:10.1161/CIRCULATIONAHA.108.191096 (not retrieved; cited for context only)