Note that lead I is at zero degrees, lead II is at +60 degrees, and lead III is at +120 degrees. Lead aVL (L for left arm) is at -30 degrees and lead aVF (F for foot) is at +90 degrees.

There are a variety of causes, including left anterior fascicular block and left ventricular hypertrophy ... deviation in this setting, look at lead II. If lead II is downward (negative), then ...