Signal‐Averaged Electrocardiography of the Terminal QRS in Healthy Young Adults

Interpretation of signal-averaged electrocardiograms (SAECG) in the young could be of value in detecting those at risk for episodic ventricular tachycardia, but suffers from a lack of data in normal young people. The purpose of this study is to determine normal values for QRS duration and the duration and amplitude of terminal potentials on the SAECG in young adults. Thirty-two normal medical students were examined. With high pass filtering at 25 Hz, normal total QRS duration (QRS) varied as a function of sex and body size whereas low amplitude signal duration (LAS) did not. Ninety-five percent confidence limits are: QRS (male) 85-117 msec, QRS (female) 76-102 msec, and LAS 6-35 msec. Root mean square voltage of the terminal QRS showed a broad scatter, however none was less than 20 microvolts. High pass filtering at 40 Hz did not change the QRS duration, but resulted in significantly longer LAS duration and diminished RMS voltage. Because of the longer QRS and shorter LAS previously reported in the presence of right bundle branch block, the normal values reported here should not be applied in the presence of intraventricular conduction delay following surgical repair of congenital heart disease. They will, however, provide a basis for interpretation of SAECG in young adults with normal QRS duration.