Sodium-calcium balance in nonionic contrast media. Effects on the risk of ventricular fibrillation in the isolated rabbit heart.

RATIONALE AND
OBJECTIVES: During coronary arteriography the blood is replaced for a short period of time with a contrast medium (CM) solution. The CM may cause a risk of arrhythmias and ventricular fibrillation (VF). Previous investigations have shown that the addition of small amounts of sodium (10-30 mmol/L) to nonionic CM may decrease the risk of VF from these media. Calcium addition to nonionic CM may reduce a negative inotropic effect. In the current investigation, the changed risk of VF from nonionic CM with 19 to 30 mmol/L NaCl was studied when the media also contained calcium or calcium and magnesium.
METHODS: An isolated rabbit heart model was used. The risk of arrhythmias and VF from the nonionic monomer iohexol and the nonionic dimer iodixanol containing 19 to 30 mmol/L NaCl with 0 to 2.5 mmol/L calcium as CaCl2 was studied. In the series with iodixanol, 0 to 0.95 mmol/L MgCl2 also was added to the solutions with sodium and calcium, but the role of magnesium was not especially evaluated in the investigation.
RESULTS: Nonionic CM with small amounts of NaCl (19-30 mmol/L), without calcium or with calcium at the level of 0.05 to 0.3 mmol/L, caused the lowest risk of VF. When relatively higher additions of calcium reached the physiologic concentration of 2.5 mmol/L, the CM caused a greater risk of arrhythmias and VF.
CONCLUSIONS: When calcium is added to a nonionic CM, the concentration of calcium must be balanced against the NaCl concentration to minimize the risk of VF. Excessive calcium concentration will increase the risk of VF.