What are the normal electrocardiogram (EKG) measurements for a healthy adult woman?

Normal EKG Measurements for Adult Women

For healthy adult women, the key normal EKG parameters include: QRS duration <110 ms, QTc interval ≤460 ms, heart rate 60-100 bpm, PR interval 120-200 ms, and QRS axis -30° to +90°, with important sex-specific differences in repolarization patterns and voltage criteria that must be considered for accurate interpretation. 1, 2, 3

Core Interval Measurements

QRS Duration

• Normal QRS duration in adult women (>16 years) is <110 ms 1
• QRS duration ≥120 ms indicates complete bundle branch block and warrants echocardiography to assess ventricular function 4
• QRS duration between 110-119 ms with rsR' pattern suggests incomplete right bundle branch block 4

QT Interval (Rate-Corrected)

• The upper limit of normal QTc for women is 460 ms, which is longer than the male threshold of 450 ms 2, 3
• QTc should be measured from the earliest QRS onset to the latest T-wave offset, typically longest in leads V2 or V3 5
• Normal QTc thresholds: shortened <390 ms, normal 390-460 ms, prolonged >460 ms 3
• Visual validation of computer-measured QTc is essential due to algorithm variability in defining T-wave offset 5

PR Interval

• Normal range: 120-200 ms in adults 6
• Values >200 ms indicate first-degree atrioventricular block 5

Heart Rate

• Normal resting heart rate: 60-100 beats per minute 1
• Age-related changes should be considered when evaluating heart rate normality 1

Sex-Specific Considerations for Women

Repolarization Parameters

• Women have physiologically longer QTc intervals than men due to hormonal influences, making the 460 ms threshold critical 2, 3
• T-wave amplitude in lead aVR: normal is <-100 μV (more negative); values >-100 μV are associated with increased coronary heart disease mortality risk 7
• T-wave amplitude in lead V1: normal is <175 μV; values >175 μV predict increased cardiovascular risk 7

ST-Segment Thresholds

• For women, ST-segment elevation thresholds are lower than for men:
  • Leads V2-V3: 0.15 mV (1.5 mm) for women vs. 0.2-0.25 mV for men 2
  • All other leads: 0.1 mV (1 mm) 2
• ST-segment depression at rest: normal is minimal; depression >150 μV may be abnormal 3

QRS Axis

• Normal QRS axis: -30° to +90° 6
• Age-related rightward shift is common in older women 6

Advanced Repolarization Measurements

T-Peak to T-End Interval (Repolarization Dispersion)

• Normal threshold for white and Hispanic women: <110 ms 3
• Normal threshold for African-American and Asian women: <120 ms (race-specific difference) 3
• This parameter reflects global repolarization heterogeneity 3

QRS-T Angle

• The spatial angle between QRS and T-wave vectors is a powerful predictor of cardiovascular events in women 8
• Abnormal QRS-T angle: >42° is associated with over 2-fold increased risk of coronary heart disease death 7
• Angle between initial and terminal T vectors (Ѳ[Tinit|Tterm]): abnormal if >30° 7

QT Peak Interval

• Rate-adjusted QT peak (QTpa): normal thresholds are 295-365 ms 3
• Prolonged QTpa (>365 ms) or shortened QTpa (<295 ms) may indicate increased risk 3

Voltage Criteria and Amplitude Measurements

Left Ventricular Hypertrophy Indices

• Body mass index profoundly affects voltage criteria in women, limiting the utility of Cornell and Sokolow-Lyon voltage criteria 3
• Amplitudes in left precordial leads show substantial increase in older women (but not men), requiring age-specific interpretation 6

P-Wave Duration

• Normal P-wave duration varies by measurement method (global vs. single-lead) 5
• Global measurements from time-coherent multiple leads detect earlier onset and later offset, yielding longer durations 5

Critical Pitfalls to Avoid

• Never apply male QTc thresholds (450 ms) to women, as this leads to under-recognition of prolonged QT and increased arrhythmia risk 2, 3
• Do not dismiss rsR' pattern in V1-V2 as "incomplete RBBB" without measuring QRS duration; normal QRS duration (<110 ms) indicates a benign variant 4
• Always visually validate computer-generated QT measurements, as algorithm differences can significantly affect values 5
• Consider race-specific thresholds for T-peak to T-end interval and other parameters 3
• Account for age-related changes in QRS axis, QTc interval, and precordial lead amplitudes, particularly in older women 6
• Recognize that ST-segment depression during exercise is more pronounced in women and increases with age, but this alone does not indicate coronary disease 9

Measurement Technique Considerations

• Measure QT interval in the lead showing the longest duration, usually V2 or V3 5
• If QT measurement differs by >40 ms between leads, consider measurement error and check adjacent leads 5
• When T and U waves are superimposed, measure QT in leads without U waves (often aVR, aVL) 5
• Modern digital ECG machines using simultaneous lead recording yield longer global measurements than older sequential single-lead recordings 5