There are a handful of conditions associated with a rightward axis on the ECG: left posterior fascicular block, ventricular ectopy, lateral MI (old), pulmonary hypertension (acute or chronic), right ventricular hypertrophy, hyperkalemia, misplaced leads, and toxicity of sodium channel blocking drugs, to name a few.
When you notice that the rightward axis is NEW compared to an old ECG, and there's nothing else on the ECG that's obviously diagnostic (e.g. hyperkalemia would also show peaked Ts; ventricular tachycardia would be wide complex and fast, etc.), in emergency medicine you should always think first and foremost of the following three possibilities: 1. acute pulmonary embolus 2. toxicity of a sodium channel blocking drug 3. misplaced leads
Pay attention to axis! Using the above rule can make rightward axis very simple and useful.
