Determining the QRS axis: visual estimation is equal to calculation

Area of Science:

• Cardiology
• Medical Imaging
• Diagnostic Tools

Background:

• The QRS axis on an electrocardiogram (ECG) is crucial but often estimated crudely.
• Precise QRS axis determination is valuable for scenarios like pinpointing the origin of premature ventricular complexes (PVCs).
• Visual estimation using the hexaxial reference system offers a method for more exact QRS axis determination.

Purpose of the Study:

• To evaluate the correlation between visually estimated QRS axis and mathematically calculated QRS axis.
• To assess the accuracy of visual QRS axis estimation in patients with outflow tract PVCs.

Main Methods:

• Analysis of 12-lead ECGs from a PVC database (2012-2020) for outflow tract PVCs.
• Visual QRS axis determination by two physicians using the hexaxial reference system (±10° accuracy).
• Calculation of QRS axes using three established voltage-based formulas.

Main Results:

• Strong correlations were found between visually estimated and calculated QRS axes for both regularly conducted beats (r=0.97-0.98) and PVCs (r=0.94).
• Estimated QRS axis for regularly conducted beats was 39±40°, and for PVCs was 88±15°.
• Calculated QRS axes closely matched the visual estimations across all formulas and beat types.

Conclusions:

• Sophisticated visual estimation of the QRS axis is a reliable method.
• This visual estimation correlates well with voltage-based calculations.
• The visual method is sufficient for most clinical purposes in ECG analysis.