Electrocardiographic characteristics in the underweight and obese in accordance with the World Health Organization classification

ObjectiveIt is clinically important to recognize how the underweight or obese affects electrocardiogram (ECG). We assessed the effects of body mass index (BMI) on QRS axis or R-wave heights.MethodsFrom daily outpatient electrocardiograms with sinus rhythm, 203 were selected. The patients were classified into four groups: underweight (< 18.5 kg/m2), normal weight (18.5–24.9 kg/m2), overweight (25–29.9 kg/m2) and obese (≥ 30 kg/m2).ResultsWith increasing BMI, QRS axis shifted rightward to leftward. There was a significant inverse correlation between BMI and QRS axis (r = − 0.60, p < 0.001). Multivariate linear regression analysis among age, female, BMI, hypertension, left ventricular internal dimension and left ventricular mass (LVM) revealed that BMI was an independent determinant of QRS axis (β = − 0.52, p < 0.0001). Although LVM increased with increasing BMI, R-wave heights in leads V4-5 were similar among the underweight, normal weight and overweight. R-wave heights in leads V4-5 were significantly lower paradoxically in the obese than other groups. With increasing BMI, Sokolow–Lyon index corrected by LVM decreased progressively.ConclusionsOur results suggest that the underweight or obese is strongly associated with QRS axis or R-wave heights.