Hyperkalemia can cause several characteristic EKG abnormalities that are often progressive. Initially the T wave becomes tall, symmetrically peaked and tented. Widening of the QRS complex with an intraventricular conduction delay then occurs. Additional elevation of serum potassium leads to a decrease in the amplitude of the P wave and its eventual disappearance from the EKG. Rarely, ST segment elevation mimicking myocardial in- farction, described as “pseudoinfarction” pattern, is pre- sent. Further progression of hyperkalemia leads to a sine wave appearance of EKG and eventual asystole. These progressive changes in EKG have not been previously studied in respect to the corresponding serum K+ levels.