Widened: (1) ventricular premature beats, (2) bundle branch blocks: right (RsR' in V1, deep S in V6) and left (RR' in V6 [Fig. 111-2]), (3) toxic levels of certain drugs (e.g., flecainide, propafenone, quinidine), (4) severe hypokalemia.
Section 8. Cardiology