Electrocardiographic changes during intravenous urography: a study with sodium iothalamate and iohexol

The electrocardiographic changes induced during a rapid bolus intravenous injection of both a conventional ionic agent (sodium iothalamate) and a new, low-osmolality non-ionic agent (iohexol) have been studied. Multiple abnormalities were observed but in every category significantly less frequently, or not at all, with iohexol. The most common abnormality was an increase in sinus rate of 15 beats/min over the rate during needle insertion. Other abnormalities observed included T-wave flattening and premature atrial and ventricular contractions. Contrary to some previous studies, we did not find that age, known heart disease or an abnormal base-line ECG were statistically significant determinants of subsequent ECG changes on contrast administration. There was, however, a significant correlation between ECG changes and more severe subjective side-effects experienced after the contrast injection. This offers support for the theories suggesting a psychogenic basis for some contrast reactions, since low-osmolality contrast media are known to produce less marked subjective side-effects. The new agents are known to be less cardiotoxic and to produce less profound haemodynamic changes. These factors may also play a part in the observed reduction in ECG disturbance.