ECG interpretation · interactive lab

Where is the QRS pointing?

Move the vector around the hexaxial wheel. Watch the axis, classification, and bedside quadrant rule update together.

DRAG OR TAP THE WHEEL

Tip: angle is measured counter-clockwise from lead I (0°). Tap any spot or drag the cyan handle.

0°

mean QRS axis

NORMAL
AXIS

Lead polarity snapshot

Lead I

0°

aVF

+90°

Lead II

+60°

I positive + aVF positive → normal quadrant. Lead II is positive, supporting a normal axis.

Quick angle control0°

Fast quadrant rule

I + / aVF + = normal. I + / aVF − = possible LAD; check Lead II. If II −, LAD is more likely. I − / aVF + = RAD. I − / aVF − = extreme (“northwest”) axis.

Exam cut-offs

Normal −30° to +90°LAD −30° to −90°RAD +90° to +180°Extreme −90° to ±180°

Borderline values can vary by convention; classify the pattern with the polarity logic, not a single number alone.