What is the interpretation of an EKG (electrocardiogram) showing P-R-T axes values of 38, 20, and 78 degrees?

EKG Axis Interpretation: P 38°, QRS 20°, T 78°

Overall Assessment

This EKG shows a normal P-wave axis, left axis deviation of the QRS complex, and a normal T-wave axis. The QRS axis of 20° falls outside the normal range and warrants clinical correlation, though the P and T axes are within normal limits. 1

Individual Axis Analysis

P-Wave Axis: 38° (Normal)

• Normal P-wave axis ranges from 0° to 75° according to American Heart Association guidelines 1
• A P-wave axis of 38° is well within normal limits and indicates normal atrial depolarization 1
• This finding has no pathological significance in isolation 1

QRS Axis: 20° (Left Axis Deviation)

• The normal QRS axis in adults ranges from +30° to +90° per American College of Cardiology and American Heart Association standards 1, 2
• A QRS axis of 20° represents mild left axis deviation, falling just outside the lower limit of normal 1
• This degree of deviation (between 0° and +30°) is considered mild and may be a normal variant, particularly with increasing age 1

Clinical significance of this finding:

• Left axis deviation alone has limited diagnostic value and must be interpreted with other ECG findings and clinical context 1
• Common causes include left ventricular hypertrophy, left anterior fascicular block, and age-related changes 1
• Although an abnormal QRS axis occurs in some normal individuals, its presence should prompt thorough evaluation of all ECG parameters to exclude myocardial disease 2

Additional criteria to assess:

• Evaluate for left anterior fascicular block: look for qR pattern in lead aVL, R-peak time in aVL ≥45 ms, and QRS duration <120 ms 3, 1
• Assess for left ventricular hypertrophy using voltage criteria 1
• Compare with prior ECGs if available to determine if this represents a change 1

T-Wave Axis: 78° (Normal)

• Normal T-wave axis ranges from 15° to 75° per standard criteria 4
• A T-wave axis of 78° is at the upper limit of normal or minimally abnormal 4
• Abnormal T-wave axis has been shown to be a strong independent predictor of cardiac mortality, particularly sudden arrhythmic death 5, 6
• In this case, the T-wave axis of 78° is borderline and should be monitored, but does not represent significant pathology 6

Clinical Implications

The most clinically relevant finding is the mild left axis deviation (QRS 20°):

• Avoid the common pitfall of overdiagnosing left axis deviation as a primary diagnosis rather than recognizing it as a finding requiring clinical correlation 1
• Consider age-related changes, as QRS axis tends to shift leftward with aging 1
• Evaluate the complete ECG for additional abnormalities such as voltage criteria for hypertrophy, conduction delays, or Q waves 1

The QRS-T angle (calculated as the absolute difference between QRS and T axes) is approximately 58°:

• A QRS-T angle of 0° to 90° is considered normal 5
• This normal QRS-T angle is reassuring, as wide QRS-T angles (≥100°) are associated with increased risk of sudden cardiac death 5

Recommended Approach

For a patient with these axis values:

• Review the complete 12-lead ECG for additional findings (voltage criteria, Q waves, ST-T changes) 1
• Correlate with clinical history, particularly cardiovascular risk factors and symptoms 2
• Compare with prior ECGs to assess for interval changes 1
• If this represents new left axis deviation or if other concerning ECG features are present, consider echocardiography to evaluate for structural heart disease 1
• The borderline T-wave axis warrants monitoring in follow-up ECGs, particularly in elderly patients where abnormal T-wave axis is a strong predictor of cardiac events 6