Normal Limits of Electrocardiogram and Cut-Off Values for Left Ventricular Hypertrophy in Young Adult Nigerians

This study assessed healthy young adults to determine the normal limits for electrocardiographic variables and cut-off values for left ventricular hypertrophy. It was a cross sectional descriptive study in which the participants were evaluated clinically by standard 12-lead resting electrocardiogram (ECG) at 25mm/s during quiet respiration. The heart rate, P wave duration, axis and amplitude, PR and QT intervals, QRS duration, axis and amplitude and T wave axis were assessed. Three hundred and twenty four (324) volunteers comprising of 175 males and 149 females aged 20 to 30 years (mean, 23.01±2.88years) participated in the study. The normal limits for heart rate, P wave duration, amplitude and axis in lead II, QRS duration and axis, T wave axis, PR interval, QT interval and QTc respectively were; 61-93beats per minute,0.08-0.12s,1.00-2.00mm,22.00-79.00⁰,78.00-106.00ms,15.50-81.00⁰, 24.25-69.00⁰,0.12-0.19s, 0.32-0.40s and 0.36-0.44s. The cut-off values for Sokolow-Lyon, Cornell and Araoye criteria for assessment of left ventricular hypertrophy (LVH) were higher than those previously in use in medical practice. Gender difference exists in some cut-off values for LVH. This study defined the normal limits for electrocardiographic variables for young adult Nigerians. Racial factor should be taken into consideration in interpretation of ECG.

Keywords
Normal limits; Electrocardiogram; Cut-off values; Left ventricular hypertrophy; Young Adults