Magnesium Deficiency and Cardiac Dysrhythmia

Abstract

In the early subacute magnesium-deficiency study of Kruse et al. (1932), convulsions were produced in 86% of the rats by the 18th day, with death occurring after one or more convulsions in 93%. Tachycardia was manifest during the preconvulsive period, and bradycardia with marked arrhythmia just before the convulsions started. Greenberg and Tufts (1938) confirmed these findings, and showed additionally that ECGs, taken while the rats were unconscious from the convulsive seizures, revealed a sinoauricular block, with occasional skipped and ventricular beats. Of 10 rats with less severe magnesium deficiency, such that despite manifest nervousness only one developed convulsions, seven survived long enough to have ECGs recorded the day before sacrifice on day 62. These rats exhibited little change in heart rates (which were slightly slower than were those of control rats on the same diet to which magnesium had been added) but had lengthened P-R intervals. Five of the seven surviving deficient rats had additional ECG abnormalities: Three had numerous extrasystoles, two had abnormally high takeoff of the ST segment in lead III, one with partial heart block and one with auricular extrasystoles.