PLASMA POTASSIUM, SERUM MAGNESIUM AND VENTRICULAR-FIBRILLATION - A PROSPECTIVE-STUDY

Low plasma potassium and magnesium concentrations have been advanced a s risk factors for ventricular fibrillation (VF). For potassium, this assertion is based almost exclusively on retrospective data; for magne sium the evidence shows an association with ventricular arrhythmias bu t no direct association with VF. We studied the relationship between t hese electrolytes and VF prospectively. Plasma potassium and serum mag nesium concentrations were measured on admission to our coronary care unit. Drug therapy, time from onset of symptoms, ECG, enzyme changes a nd clinical status were all recorded. VF was confirmed by analysis of 24 h monitoring tapes. Mean plasma potassium in the 21 patients with V F who had measurements prior to their arrhythmia was 3.49 +/- 0.54 mmo l/l, lower than that of the 1165 patients without VF (mean K 3.88 +/- 0.57 mmol/l, p < 0.05). Plasma potassium concentrations in the 17 pati ents with myocardial infarction and VF were lower (mean 3.58 +/- 0.41 mmol/1) than in those without VF (n = 417, mean 3.89 +/- 0.61 mmol/1) (p < 0.05). Mean serum magnesium in the 12 patients with VF, measured prior to their arrhythmia (all with myocardial infarction) was 0.80 +/ - 0.07 mmol/l, which was not different from the mean for patients with out VF (n = 781, 0.82 +/- 0.09 mmol/l) or from the mean of 0.81 +/- 0. 08 mmol/l for those with infarction but not VF (n = 331). Low plasma p otassium concentrations are associated with increased risk of ventricu lar fibrillation, but low serum magnesium concentrations are not.