What is the interpretation of an ECG showing a normal heart rate, normal blood pressure, slightly prolonged QTc interval, and other specified electrocardiographic parameters in an adult patient with an unspecified medical history?

ECG Interpretation: Essentially Normal with Mild Left Axis Deviation

This ECG demonstrates a normal sinus rhythm with mild left axis deviation (-11° to -17°) and otherwise normal parameters that require no immediate intervention but warrant clinical correlation to determine if this represents a chronic finding or new abnormality.

Heart Rate and Blood Pressure

• Heart rate is normal at 66-70 bpm, well within the physiologic range 1
• Blood pressure is normal at 126/81 mmHg, indicating no acute hemodynamic compromise 2

QRS Axis Analysis

The QRS axis of -11° to -17° represents mild left axis deviation (LAD), which falls outside the normal adult range of +30° to +90° but does not meet criteria for marked LAD. 1, 3

• This degree of LAD (-11° to -17°) is classified as mild, falling short of moderate LAD (which begins at -30°) 3
• Mild LAD can be a normal variant, particularly with increasing age, as the QRS axis naturally shifts leftward over time 1, 3
• This finding alone has limited diagnostic value and must be interpreted with other clinical and ECG findings 3

Clinical Significance of This Axis

• The axis does not meet criteria for left anterior fascicular block, which requires marked LAD (-45° to -90°), a qR pattern in lead aVL, R-peak time in aVL ≥45 ms, and QRS duration <120 ms 1, 3
• Common causes of mild LAD include left ventricular hypertrophy, though voltage criteria would need to be assessed on the actual ECG tracing 3
• Without comparison to prior ECGs, it is impossible to determine if this represents a chronic finding or new development 3

Conduction Intervals

All conduction intervals are normal:

• PR interval: 94-100 ms (normal range 120-200 ms; this is at the shorter end but not pathologically short) 1
• QRS duration: 94-95 ms (normal <120 ms in adults) 1
• QT interval: 360-362 ms (normal, varies with heart rate) 1
• QTc interval: 370-379 ms (normal <450 ms in men, <460 ms in women) 1

Key Point on QRS Duration

• The QRS duration of 94-95 ms excludes complete bundle branch block (which requires ≥120 ms) 1
• This duration also excludes incomplete bundle branch block, which requires 110-120 ms in adults 1, 4
• The normal QRS duration makes intraventricular conduction delay unlikely 1

P-Wave and T-Wave Axes

• P-wave axis: 61-65° (normal, indicating normal atrial depolarization) 1
• T-wave axis: 57-64° (normal and concordant with QRS axis, suggesting normal ventricular repolarization) 1

Clinical Recommendations

Immediate Actions

No urgent intervention is required based on these parameters alone. 1

Further Evaluation Needed

1. Obtain prior ECGs for comparison to determine if the mild LAD is chronic or new 3
2. Review the actual ECG tracing to assess for:
   • Voltage criteria for left ventricular hypertrophy (most common cause of LAD) 1, 3, 5
   • Presence of Q waves that might suggest prior infarction 1
   • ST-segment or T-wave abnormalities not captured in automated measurements 1
3. Correlate with clinical context:
   • History of hypertension (most common cause of LVH and LAD) 1, 5
   • Presence of cardiac symptoms 1
   • Age of patient (LAD becomes more common with advancing age) 1, 3

Common Pitfalls to Avoid

• Do not overdiagnose mild LAD as pathologic without clinical correlation - it may represent a normal age-related variant 3
• Do not diagnose left anterior fascicular block based on axis alone - additional morphologic criteria must be met 1, 3
• Do not assume this ECG is completely normal without reviewing the actual tracing - automated measurements may miss subtle ST-segment or T-wave abnormalities 1
• Do not fail to obtain comparison ECGs - determining chronicity is essential for appropriate management 3

Risk Stratification

• In asymptomatic populations, ECG abnormalities (particularly LVH with repolarization changes) predict increased cardiovascular risk 1, 5
• However, mild LAD alone without other abnormalities has uncertain prognostic significance 1, 3
• The presence of normal blood pressure and heart rate is reassuring 1, 5