Ethnic differences in electrocardiographic intervals and axes

The presence of ethnic differences in electrocardiographic (ECG) patterns is debated. We retrospectively examined the first 1,000 medical files of a multi-ethnic community, where all individuals shared similar living conditions. Only healthy adults (ages 15 to 60 years) were included. All patients had similar socioeconomic, nutritional, environmental, and occupational conditions. Interval and axes measurements were obtained through integrated computerized analysis from a standard 12-lead ECG. ECGs from 597 patients were included in the study: 350 Saudi Arabians, 95 Indians, 39 Jordanians, 17 Sri-Lankans, 39 Filipinos, and 57 Caucasians; 349 patients were men. Interval and axes were compared by analysis of variance. No statistically significant differences were found among ethnic groups in PR interval, QRS duration, QT interval, P wave axis, QRS axis, or T wave axis in men (P = .05). In women, Jordanians had longer QRS duration than Filipinos (87.69 ± 10.4, 78.81 ± 5.47 ms, respectively, P = .014). P-wave axis was lower in Filipino women than Saudi, Indian, and Caucasian women (36.87 ± 26.32, 50.39 ± 16.88, 52.23 ± 16.67, 63.19 ± 14.55°, respectively, P = .002). QRS axis was significantly higher in Filipino than Saudi women (53.06 ± 26.14, 32.62 ± 28.31°, respectively, P < .014). There was no ethnic difference in ECG interval measurements in men. However, in women, there were differences in QRS interval, and P and QRS wave axes. Although women had a statistically significant difference in intervals, the magnitude was not clinically significant. Current reference standards for ECG intervals and axes can be used across the ethnic groups studied.