Whenever the ST segment and/or T wave are directed counter to an expected repolarization abnormality, consider ischemia, healed MI, or drug or electrolyte effects.

Altered repolarization in RBBB: In RBBB, there is an obligatory inverted T wave in right precordial leads with an R' (usually only V1) or its equivalent (a qR complex in septal MI). An upright T in these leads suggests completed posterior MI.

LBBB:

LVH (with repolarization abnormalities):

Subarachnoid hemorrhage:

RVH:

Inferior subendocardial injury:

Posterior subepicardial injury:

Anterior subendocardial injury (NSTEMI):

Hypokalemia:

Digitalis:

Antiarrhythmics:

J point depression secondary to catecholamines:

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