Blood calcium levels in the presence of arteriographic contrast material.

One of the complications of coronary angiography is a sudden and persistant fall in blood pressure. This may be due to the presence of calcium chelating agents in the vehicle of the radio-opaque compounds. Depressed ambient calcium levels are associated with decreased myocardial contractility and when low enough cause electromechanical dissociation. Simultaneous measurements of radial artery and coronary sinus ionized calcium levels in nine patients during intracoronary injection of the contrast agent revealed a lowering of the level of ionized calcium in the coronary sinus to a point that can be expected to be associated with a decrease in myocardial contractility. This ionized calcium depression was more marked and prolonged in patients with arteriosclerosis, some reaching levels which, if persistent, could result in electromechanical dissociation.