[QT interval shortening in families with history of sudden death at young age].

AIM

To assess frequency of short QT interval among members of families with history of young age sudden death.

MATERIAL

Eleven children aged 3-16 years (mean age 11.2+/-4.2 years) from families with cases of sudden death at young age (<40 years) not caused by an obvious disease according to autopsy data. None of the probands had overt heart disease, life threatening arrhythmias, long QT syndrome.

METHODS

Predicted QT value was estimated according to the P. Rautaharju formula [QT(p)=656/(1+HR/100)], and values equal to 80 and 88% of QT(p) (QT(p)80 and QT(p)88) were determined. Corrected QT interval duration (QT(c)) was calculated for all these values with the use of the Bazett formula.

RESULTS

Values of corrected QT(c)88 370 ms and 350 ms were considered minimal for heart rates above and below 78 bpm, respectively. QT shortening to the level of QT(p)80 at heart rates above 70 bpm corresponded to QT(c) values <330 ms. Nine of 11 children (81.1%) had QT interval equal to or less than QT(p)88. Three probands with attacks of syncope had QT equal to QT(p)80, high concentration of sudden deaths in family (up to 30% of family members), and high prevalence of shortened QT <80% among family members.

CONCLUSION

Shortened QT interval is characteristic for children with family history of sudden death at young age. Registration of QT duration equal to or shorter than 88% of predicted value requires exclusion of diseases and syndromes with increased risk of sudden death.