Inotropic effects of ionic and nonionic contrast materials in isolated heart preparations.

: The inotropic effects of ionic (amidotriazoate) and nonionic (iohexol) contrast material were compared in isolated rat heart preparations. Left atria exposed to amidotriazoate for 10 mins exhibited a dose dependent depression of contractile force approximately twice as large as that brought about by equiosmolar sucrose. When the driving rate was reduced from 60 to 20 beats/min, this specific effect was abolished. The spontaneously beating hearts perfused with amidotriazoate-containing medium had increased resting tension and depressed force of contractions. These effects tended to spontaneously normalize. Upon bolus administration of amidotriazoate the contractile force of perfused hearts was briefly depressed and heart rate, action potential duration and time to peak force decreased. Iohexol did not produce any significant changes in the contractile force. The experiments illustrated direct action of ionic contrast dye on cardiac inotropy probably resulting from an immediate, slowly compensated ionic imbalance, and demonstrated a definite superiority of the nonionic contrast material.