A QRS axis between -90° and 180° (the 'northwest'): lead I and aVF both negative, aVR positive.
Up and to the right: the frontal QRS axis points between -90° and 180°. Lead I and aVF are both negative, and aVR is positive. You'll see it with ventricular rhythms, hyperkalemia, severe right ventricular hypertrophy, and swapped limb leads. It's drawn here in sinus rhythm so you can learn the axis on its own.
Each is a standard 12-lead: 2.5 seconds of each lead in four columns, with 10 seconds of lead II along the bottom, drawn to scale (25 mm a second, 10 mm a millivolt). The measurements are under each one.
A QRS axis more negative than -30°: lead I positive, lead II and aVF mostly negative.
A QRS axis beyond +90°: lead I negative, aVF positive.
The ECG tool in the app gives you a new 12-lead every time and walks you through reading it: rate, QRS, axis, then where the ST is up and down. It's part of the Paramedic level, and you can try 5 ECGs a day free.
Try the 12-lead drill
EMS Registry Ready