THE RELATIONSHIP BETWEEN R AMPLITUDE IN LEAD V-5 (RV5) AND LEFT-VENTRICULAR MASS IN THE GROUPS OF ADOLESCENT SUBJECTS CLASSIFIED BY BODY-COMPOSITION

How the amplitude of the R wave in lead V5 (RV5) of the ECG represents the left ventricular (LV) mass was investigated in 894 students aged 15 (boys: 545, girls: 349). The influence of body composition [ie, per centage of body fat (%fat)] was taken into consideration. A significan t correlation was found between RV5 amplitude and LV mass for both gen ders. However, the relationship was stronger for boys than for girls. The students were then divided into 3 groups; that is, those at either the top or bottom 10th percentile (low or high-fat range) and the res t of the students (middle-fat range), depending on the % fat calculate d by the bioelectrical impedance method. The significant correlation b etween RV5 and LV mass was found only for the 2 groups of boys whose p ercentage fat was in the low or middle-fat range. The correlation coef ficients were 0.40 and 0.34, respectively. Moreover, in the boys' low- fat range, the RV5 of students whose LV mass was large (greater than o r equal to 90th percentile), was significantly higher (p<0.01) than in the other ranges. Setting a particular cutoff point of RV5 in the low -fat range of boys improved sensitivity as well as specificity (20-30% better among all boys) for detecting large LV mass. These observation s suggest that classification of subjects by body composition could be improve the reliability of ECG assessment for left ventricular hypert rophy, although the gender and number of subjects in whom improvement is expected are limited.