Hyperkalemia revisited

Abstract

Hyperkalemia is a common clinical condition that can induce deadly cardiac arrhythmias. Electrocardiographic manifestations of hyperkalemia vary from the classic sine-wave rhythm, which occurs in severe hyperkalemia, to nonspecific repolarization abnormalities seen with mild elevations of serum potassium. We present a case of hyperkalemia, initially diagnosed as ventricular tachycardia, to demonstrate how difficult hyperkalemia can be to diagnose. An in-depth review of hyperkalemia is presented, examining the electrophysiologic and electrocardiographic changes that occur as serum potassium levels increase. The treatment for hyperkalemia is then discussed, with an emphasis on the mechanisms by which each intervention lowers serum potassium levels. An extensive literature review has been performed to present a comprehensive review of the causes and treatment of hyperkalemia.

Fig. 1 Admission electrocardiogram.

Fig. 2 Electrocardiogram after the correction of hyperkalemia.

Fig. 3 Illustration of a normal action potential (solid line) and the action potential as seen in the setting of hyperkalemia (interrupted line). The phases of the action potential are labeled on the normal action potential. Note the decrease in both the resting membrane potential and the rate of phase 0 of the action potential (V_max) seen in hyperkalemia. Phase 2 and 3 of the action potential have a greater slope in the setting of hyperkalemia compared with the normal action potential.

Fig. 4 Curve relating V_max to the resting membrane potential at the onset of action potential. As the membrane potential becomes less negative, as in the setting of hyperkalemia, the V_max decreases, leading to a depression of conduction through the myocardium.

Fig. 5 Curve relating V_max to the resting membrane potential under conditions of hyperkalemia (solid line) and in the setting of increased calcium concentration (interrupted line). For any given resting membrane potential, up to approximately −75 mV, increasing calcium levels lead to an increase in V_max.