Electrocardiographic abnormalities and serum magnesium in patients with subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: ECG abnormalities and hypomagnesemia frequently occur after aneurysmal subarachnoid hemorrhage (SAH). Because hypomagnesemia is associated with several ECG abnormalities, we studied whether hypomagnesemia mediates ECG abnormalities after SAH.

METHODS: We prospectively studied a consecutive series of 62 patients admitted within 72 hours after aneurysmal SAH. A standard 12-lead ECG and serum magnesium measurement were routinely performed at admission. The relationship between serum magnesium and ECG abnormalities was assessed with linear regression analysis and the Mann-Whitney test in case of dichotomized ECG abnormalities.

RESULTS: Hypomagnesemia was present in 23 patients (37%), and 38 patients (61%) had a long QTc duration. Low serum magnesium was related to a long PR interval (P=0.001) and a shorter QTc interval (P=0.004). Adjustment for World Federation of Neurological Surgeons score, hydrocephalus, and the amount of cisternal and ventricular blood did not influence these relations.

CONCLUSIONS: In patients with SAH, lower serum magnesium levels are related to less pronounced increase in the QTc interval. Although the direction of the relation was unexpected, decreased serum magnesium might be the missing link between SAH and ECG abnormalities.