cardiolab: Interactive ECG Simulator

cardiolab

Simulator 12-Lead Axis Flashcardsupdates

Cardiac axis

Where the mean QRS vector points in the frontal plane

Left axis deviation-78°normal -30° to +100°

Axisdrag or use arrows

Findings

Lead I: positive
aVF: negative
Narrows to: Left quadrant → -90° to 0°
Measured: -77.9° off the drawn beat

Only the QRS turns. The P and T stay where a normal heart puts them, because axis means the QRS axis.

Causes of left axis deviation

Left anterior fascicular block
Inferior myocardial infarction
Left bundle branch block
Left ventricular hypertrophy
Ventricular pacing or ventricular ectopy
Wolff-Parkinson-White pattern
Hyperkalaemia

The leads sit as a printed ECG shows them: I, II and III, then aVR, aVL and aVF. Cabrera lays them out in the order the dial runs, from -30° to +120°. aVR is drawn as recorded, looking along -150°, up and to the right and away from the heart, which is why it is negative on almost every normal ECG.