The effects of infusion of calcium and magnesium ions on the cardiovascular system in man.

The effects of Ca++ and Mg++ infusion on the cardiovascular system were studied in 96 normotensive subjects and 85 hypertensive patients. The results obtained were as follows: (1) The effects of Ca++ infusion on the systolic time intervals were characterized by the shortening of QS2I, PEPI, and ICT, and increase in ET/PEP. The responses of the systemic hemodynamics were elevation of mean blood pressure and increase in cardiac index and stroke index. The heart rate was not altered. (2) These results support that Ca++ has a positive inotropic action and increases the left ventricular performance. (3) The effects of Mg++ infusion on the systolic time intervals were characterized by the prolongation of QS2I, PEPI, and ECT. The responses of systemic hemodynamics were elevation of mean blood pressure and increase in heart rate. The ET/PEP and cardiac index tended to decrease, but these changes were not significant. (4) From these results it is suggested that Mg++ depress myocardial contractility and has a positive chronotropic action. (5) There were no significant differences in the systolic time intervals and hemodynamic responses to the infusion of Ca++ and Mg++ between normotensives and hypertensives.