Effects of contrast media used in angiocardiography on the mechanical performance and the relaxation of normal and ischaemic myocardium

The aim of this study was to investigate the mechanisms of thecardiodepressive action of ionic and non-ionic contrast mediacurrently used in coronary arteriography. Experiments carried out on isolated preparations of cat papillarymuscle, treated with increasing concentrations of Telebrix 39,Radioselectan, Hexabrix and Iopamidol 370 and 300, on the onehand and, on the other hand, a pre- determined dose of Telebrixand Iopamidol 300 during hypoxia and subsequent reoxygenation,showed that, at constant Ca²⁺ concentrations: (1) The cardiodepressive effects of contrast media are correlatedwith the hyperosmolality that they induce. When osmolality washigher than 400 mOsm, all the products caused a reduction ofthe peak force (PF: 40–49±5–15 %), the maximumvelocity of contraction (V_max: 39-85±3–66 %) andof the peak velocity of relaxation (V_relax: 23-30±2-20%) (P<0-01). The time to peak force (TPF), on the other hand,remained constant, whereas the half-relaxation time (THR) wasincreased. No significant differences were observed betweenthese effects and those induced by control iso-osmolar solutionswhen the same osmolality was induced. In practice, however, the critical hyperosmolality value of400 mOsm is never reached when using non-ionic contrast mediasuch as Hexabrix and Iopamidol 300. This could explain the excellenttolerance to these substances. (2) During hypoxia and reoxygenation, the effect ofhyperosmolalityis more marked. Thus, the non-ionic contrast medium, Iopamidol300 (340 mOsm), reduces the hypoxic contractility depression(PF: 53-10±2-60% compared to the control values of47-60±5-00%,P<0-01), whereas, at the same dose, the ionic medium Telebrixis hyperosmolar (440 mOsm) and induces a more pronounced hypoxicdepression of contractility (P<0-01). The critical hyperosmolality is never reached during ventriculography(320 mOsm), whatever the medium used, but it can be observedduring coronary arteriography. It is, therefore, important touse non-ionic contrast media in the investigation of unstableangina and of acute myocardium infarction.