Abstract
A QTc interval at the upper limits in young athletes can be challenging. Regardless
of factors able to influence it (age, electrolytes, etc.), several authors underlined
that rate correction formulas can often underestimate/overestimate it. Our objective
was to identify the most reliable formula and relative upper normal limit of QTc for
this population. The rest ECG of 701 healthy elite male athletes was analyzed. QTc
was calculated with 4 formulas (Bazett, Fridericia, Framingham, Hodges). Correlation/regression
analysis of QTc vs. heart rate and upper limits were calculated and compared considering
different age groups. Abnormal ECGs were compared considering different upper limits.
Correlation between QTc and heart rate was highly significant using Bazett’s and Framingham’s
formulas, lower using Hodges’ formula, and not significant using Fridericia’s formula.
Except for Framingham’s, the number of abnormal ECGs was identical considering an
upper limit of 480 msec, and significantly different for lower limits. Upper limits
were: Bazett 469 msec, Fridericia 451 msec, Framingham 458 msec, and Hodges 461 msec.
Except for Framingham’s, no difference among other formulas in individuating abnormal
ECGs for QTc≥480 msec was found. QTc obtained with the Bazett’s formula appears highly
dependent on heart rate. This, especially in the grey zone (440–480 msec), can lead
to overtesting. Framingham’s formula shows similar limits. Hodges’ formula offers
uncertain reliability. Fridericia’s formula seems the most reliable.
Key word
ECG - sudden death - Bazett - Fridericia - Long QT - LQTS
