Gadolinium phosphonates as MR imaging contrast agents: physiologic effects in rabbit hearts

The hemodynamic effects of the diphosphonate terminus of a new infarct-avid magnetic resonance (MR) imaging agent, gadolinium-DTPA (diethylenetriamine-pentaacetic acid) HPDP (1-hydroxo-3-aminopropane-1,1-diphosphonate), and HEDP (hydroxyethyl-1,1-diphosphonate) (a simple diphosphonate terminus model) have been evaluated at MR imaging doses in both isolated and intact rabbit hearts. Rapid injections of the sodium salt of the diphosphonates reversibly depressed left ventricular developed pressure and its first derivative (dP/dt) but did not affect the in vivo heart rate. Hemodynamic depression was prevented by the co-administration of two equivalents of calcium ion per diphosphonate terminus in the isolated heart and by either slow infusion or co-administration of one equivalent of calcium ion per diphosphonate terminus in the in vivo heart. Therefore, if these agents are to be used in MR imaging of acute myocardial infarction, appropriate measures should be taken to prevent negative inotropic effects.