The potassium/sodium ratio in the demonstration of sudden ischemic cardiac death: a critical appraisal

Abstract

The practical value of measuring the ratio of potassium ion (K+) to sodium ion (Na+) in myocardium as an indicator of early inapparent infarction in sudden cardiac death was assessed using a series of 29 human hearts from selected coroner's autopsies together with experimental material from dogs, including infarcts of 5 min to 4 h duration. Samples for electrolyte analysis were derived from a transverse slice of each heart, taken through both ventricles midway between base and apex, all slices being completely subdivided into a numbered sequence of blocks. Ratios were mapped and compared with macroscopic enzyme staining and histological stains for injured muscle. Detailed examination of coronary arteries was performed on all human cases. Measurement of the K+/Na+ ratio did not detect all human cases of proven acute coronary occlusion and did not unequivocally demonstrate experimental infarcts less than 2 h old. Moreover, all ratios fell with increasing duration of autolysis, emphasizing the need for multiple sampling so that each heart may serve as its own control. As a routine test, therefore, the method is both impracticable and unreliable and as previously used has been subject to misinterpretation.