Resumen

ACOLTZIN, Cuauhtémoc  y  RABLING, Elizabeth. In electrocardiograms with long QTc, descending branch of T greater than 44% of JT, is abnormal. Rev. Mex. Cardiol [online]. 2014, vol.25, n.1, pp.3-6. ISSN 0188-2198.

Introduction and objetives: The prolongation of ventricular M cell action potential lengthens QT, increases the supernormal phase and propitiates death by electrocution; however, it is not possible to identify the patient who is at risk. Because the descending branch of the T-wave in the area principally affected, the possibility of arrythmogenic risk could be identified by the relative duration of the T descending branch is worth considering. Material and methods: Electrocardiograms of patients in sinusal rhythm, with a cardiac frequency between 60 and 100 p/m, QRS lower than 0.100 s. and without myocardial infarction o medication affecting repolarization were analyzed. The R-R, QT, QRS and the descending branch of the T-wave (rdT) were measured. QRS was subtracted from QT (JT), rdT was divided by JT and multiplied by 100. QTc was calculated. Groups were separated according to QTc duration between 0.350 and 0.440 o greater (QTc N and QTc L). Histograms were made. Mean, standard deviation, median, mode and interquartile range were calculated. Data was analyzed using the Mann-Withney U test and the Z transformation of the normal curve. Result: There were 100 electrocardiograms of QTc L and 400 of QTc N. The curves were non-parametric with downward bias. There was significant difference (p = 0.002). The interquartile range was similar in 75% of the cases. Z transformation indicated abnormality in rdT/JT = 44. Conclusion: The descending branch of T bigger than 44% of JT is abnormal.

Palabras llave : Sudden death; long QT syndrome; electrocardiography.