ROLE OF SODIUM IN CONTRAST MEDIUM-INDUCED POLYMORPHIC VENTRICULAR-TACHYCARDIA - RESULTS IN A RABBIT MODEL OF LENGTHENED QT INTERVAL

Rationale and Objectives. The authors (a) compared the proarrhythmic e ffects of ioxaglate (152 mmol/L sodium) and iohexol (no sodium) in a r abbit model and (b) assessed the effect of adding 150 mmol/L sodium to isotonic iohexol. Materials and Methods. Either ioxaglate (320 mg of iodine per milliliter) or iohexol (350 mg of iodine per milliliter) wa s selectively injected into the right coronary artery (1.5 mL over 30 seconds) of 10 rabbits, some of which also received the alpha(1)-adren ergic receptor agonist methoxamine. To validate the model, the class I II antiarrhythmic agent clofilium was injected intravenously during me thoxamine infusion. Frontal electrocardiography was performed continuo usly to detect polymorphic ventricular tachycardia (PVT). In a second study, the authors assessed the frequency of arrhythmias after injecti on of isotonic iohexol solution (145 mg of iodine per milliliter), eit her alone or with 150 mmol/L sodium. Results. Methoxamine significantl y lengthened the QT, QTc, and RR intervals (P < .05). The use of clofi lium alone induced no PVT, whereas five of eight methoxamine-infused r abbits developed PVT after clofilium injection (P = .03). Both contras t media prolonged the repolarization period. Iohexol alone induced a h igher frequency of PVT than did ioxaglate alone (P = .0006). Methoxami ne infusion did not potentiate the frequency of PVT in the ioxaglate-i njected rabbits. The addition of sodium to isotonic iohexol prevented the occurrence of PVT ( P = .0006). Conclusion. Although ioxaglate pro longed the repolarization period, it did not cause a higher frequency of arrhythmia when injected in association with methoxamine. Iohexol, which contains no sodium, induced a high frequency of arrhythmia. The addition of a physiologic concentration of sodium to isotonic iohexol can prevent ventricular arrhythmias.