Electrocardiographic Profiles by Sex in a Cohort of Healthy Vietnamese University Students

Objective: To establish sex-specific electrocardiographic (ECG) reference values among healthy young Vietnamese adults and to characterize sex-based differences in precordial lead patterns, with particular attention to early repolarization and T-wave morphology. Methods: In this cross-sectional study, 5,127 first-year Vietnamese university students (58.6% female; age 17–29) underwent resting 12-lead ECG recordings as part of a routine health screening. Participants were asymptomatic and free of known cardiovascular or metabolic disease. Standard ECG parameters—including heart rate (HR), PR interval, QRS duration (QRSd), QTc (Bazett’s correction), and QRST angle—were automatically extracted and manually verified. J-point (JV1–V6), ST-segment (ST60V1–V6), and T-wave amplitudes (TV1–V6) in precordial leads were evaluated to identify sex-based patterns. Data were summarized as medians with interquartile ranges and compared using non-parametric Wilcoxon rank-sum tests. Results: Significant sex differences were observed across all ECG parameters (p < 0.001). Females exhibited higher HR (83 vs. 80 bpm), shorter PR intervals (138 vs. 140 ms), and longer QTc intervals (423 vs. 406 ms), while males had longer QRS durations (90 vs. 80 ms) and narrower QRST angles. In the precordial leads, males demonstrated greater J-point and ST60 amplitudes, particularly in V2–V3, where the 98th percentile of ST60V2 reached 0.40 mV in males—surpassing international reference thresholds. Females more frequently exhibited anterior T-wave inversion (TWI), with 71.3% showing TWI in V1 and 2.5% in V2, compared to 48.1% and 0.9% in males, respectively. TWI beyond V2 was rare in both sexes. These patterns closely mirrored sex-specific repolarization profiles described in Western and athletic cohorts. Conclusion: This study provides the first comprehensive sex-stratified ECG reference data for healthy Vietnamese adults. Distinct sex-specific patterns in precordial leads—including elevated ST segments in males and higher prevalence of anterior TWI in females—underscore the need for ethnically tailored ECG interpretation criteria. These findings have clinical implications for improving diagnostic precision and avoiding overinterpretation of repolarization variants in Southeast Asian populations.