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Abstract
The objective was to study the influence of geomagnetic activity as reflected by K- and Ak-indices on mean arterial blood pressure (MAP), heart rate (HR), and hemodynamic index (HDI, HR.MAP), and on cardiovascular variability expressed by MAP and HR standard deviation (SD). Baroreceptor function was assessed from measurement of the rate-pressure response (ΔHR/ ΔMAP) for intravenous phenylephrine. One hundred forty-three experimental runs were canied out in 29 rabbits. Rabbits were sedated by pentobarbital infusion (5 mg/kg/h) during 50-min experiments. MAP, HR, HDI, MAP SD, and HR SD were measured after a 10-min resting period for 5 min, followed by ΔHR/ΔMAP testing. We found a significant positive correlation of geomagnetic activity with MAP and HDI, and a negative correlation with ΔHR/ΔAP, MAP SD, and HR SD. Diminished baroreflex sensitivity and sympathetic hyperactivity may participate in the observed effects, and explain the greater incidence of severe cardiovascular events during magnetic storms.