The use of programmed electrical stimulation to assess the fibrillatory propensity of ionic and nonionic contrast media

Reduced Risk of Ventricular Fibrillation by Balancing Sodium, Calcium, Potassium and Magnesium Added to Nonionic Contrast Media

The effect of addition of calcium, potassium and magnesium to iohexol (350 mg I/ml) enriched with 30 mM sodium was investigated with regard to ventricular fibrillation (VF) in isolated rabbit hearts. Enriching iohexol containing 30 mM sodium with increasing amounts of calcium (0–1.2 mM) caused an increase in the frequency of VF. Increasing amounts of potassium (0–3.8 mM) to iohexol with 30 mM Na + 0.15 mM Ca + 0.1 mM Mg reduced the risk of VF. However, this protective effect of potassium on VF was reduced if magnesium was removed from the test solution. Furthermore, increasing amounts of magnesium (0–1.2 mM) to iohexol with 30 mM Na + 0.15 mM Ca + 0.4 mM K led to an increased frequency of VF. Iohexol with 30 mM Na + 0.3 mM Ca + 0.9 mM K + 0.3 mM Mg caused no VF. It is of interest to add multiple cations to sodium-containing nonionic media to improve cardiac contractility following coronary perfusion. The present study indicates that it is possible to enrich iohexol 350 mg I/ml + 30 mM Na with calcium, potassium and magnesium in small amounts, and balanced with respect to each ion, without changing the risk of VF.

Reducing the Risk of Ventricular Fibrillation by Adding Sodium to Ionic and Non-Ionic Contrast Media with Low Iodine Concentration

To compare the fibrillatory propensity of low concentrations of contrast media (140 mg I/ml) the ionic, ratio 1.5, contrast medium meglumine diatrizoate, the non-ionic, ratio 3, medium iopentol and equimolar glucose (0.37 mol/l) were perfused into 35 isolated rabbit hearts. The three substances were compared at three levels of sodium concentration (0, 77 and 154 mmol Na+/l). Meglumine diatrizoate without sodium caused the highest frequency of ventricular fibrillation (91 %). Iopentol without sodium caused a significantly lower frequency of ventricular fibrillation (17%). Glucose without sodium caused no fibrillation. The addition of 77 or 154 mmol Na+/l significantly decreased the frequency of ventricular fibrillation of both meglumine diatrizoate (3 % and 6%) and iopentol (0%). Meglumine diatrizoate with sodium added caused a lower frequency of ventricular fibrillation than iopentol without sodium. At equal sodium concentrations (0, 77 and 154 mmol Na+/l) glucose caused smaller reduction in contractile force and heart rate than iopentol, and iopentol caused smaller reduction in contractile force and heart rate than diatrizoate. It is concluded that addition of sodium to ionic or non-ionic contrast media without sodium decreases the risk of ventricular fibrillation.

Acute hemodynamic effects of intravenous bolus injection of ionic and nonionic magnetic resonance contrast media

RATIONALE AND OBJECTIVES

With the development of fast magnetic resonance (MR) imaging, bolus injection of contrast media is often required. We evaluated the acute hemodynamic effects of intravenous (i.v.) bolus injection of two MR contrast media: ionic gadopentetate dimeglumine and nonionic gadoteridol.

METHODS

Twenty normal rats were anesthetized, and the left ventricular pressure (LVP), right atrial pressure (RAP), peripheral arterial pressure (PAP), positive rate pressure development (dP/dt) of the left ventricle, and heart rate were continuously monitored up to 10 min after bolus injections of 0.1, 0.3, and 0.5 mmol/kg of either media.

RESULTS

Bolus injections of gadopentetate dimeglumine induced temporal reduction of the blood pressure (the peak LVP was -25.0% at 0.5 mmol/kg and -13.2% at 0.3 mmol/kg). At the injected doses of 0.5 and 0.3 mmol/kg, the systolic PAP, mean PAP, and dP/dt were reduced. The lowest peak systolic LVP was observed at around 20 sec after injection. Those suppressed values returned to the control values within 120 sec. Injection of high doses of gadoteridol caused a temporal increase in the peak systolic LVP (9.2% at 0.5 mmol/kg and 7.4% at 0.3 mmol/kg), systolic PAP, and dP/dt. Approximately 15 sec after injection, the highest peak systolic LVP was observed, and within 30 sec the value normalized. With both ionic and nonionic contrast media, a dose of 0.1 mmol/kg did not cause significant changes in hemodynamics.

CONCLUSION

In normal rats, bolus i.v. injection of high-dose gadopentetate dimeglumine has negative hemodynamic effects; gadoteridol produces mild positive effects.

Cardiac electrophysiology, arrhythmogenic mechanisms and roentgen contrast media

Contrast media (CM) affect normal cardiac electrophysiology when injected into the coronary arteries. High-osmolality CM cause more pronounced electrophysiological effects than do low-osmolality CM. Further, both high- and low-osmolality ionic CM have more pronounced effects than the nonionic CM. The CM-induced electrophysiological effects involve regional disturbances of depolarization and repolarization, thereby causing disturbances of impulse conduction as well as dispersion of refractoriness. Recent experimental studies have demonstrated that the addition of sodium or a balanced electrolyte supplement to nonionic CM reduces the risk of ventricular fibrillation (VF), particularly when the CM is injected in a wedged catheter situation. The reduced risk of VF may be due to the small and transient lengthening of repolarization seen in the CM-perfused area of the myocardium. Iodixanol, which is an isotonic nonionic dimer supplemented with NaCl and CaCl(2), is as well tolerated as iohexol during free coronary flow. However, when flow is restricted, such as when CM is injected through a wedged catheter, the risk of VF is less with iodixanol than with iopamidol, iohexol and ioxaglate.

A review of coronary arteriography- and contrast media-induced ventricular fibrillation

Since the first animal coronary arteriogram in 1933 there have been many innovations in techniques and contrast media. From 1933 through the late 1950s the procedures used involved nonselective aortic injections and the use of acetylcholine to slow the heart. The first selective coronary arteriogram in animals was performed by West, Kobayashi & Guzman in 1958 (45) and in 1959 Guzman & West (7) observed ventricular fibrillation with some media but not others. In 1967 Judkins (14) described the catheter designs for right and left coronary catheterizations that we still use today. In the 1970s and 80s many authors observed the ionic monomeric contrast media reduced plasma calcium causing fibrillation and myocardial depression. Supplementation of ionic media with calcium was shown to moderate these adverse effects. Almen's vision of low osmolality contrast media and the creation of metrizamide (1) stimulated the rapid development of monomeric and dimeric nonionic contrast media. The ionic dimeric medium ioxaglate also provided low osmolality. Digital frame grabbers and computers lead to the development of digital subtraction angiography and new applications of arteriography, frequently using dilute media. Unexpectedly, during prolonged right coronary arteriography in animals, dilute nonionic media were found to produce increased fibrillation as compared to dilute ionic media. The addition of sodium to nonionic media significantly reduced the incidence of fibrillation. Animal studies with the nonionic medium iodixanol supplemented with sodium and calcium (Visipaque) have demonstrated minimal incidences of fibrillation and myocardial depression.

Role of sodium addition to nonionic contrast medium in preventing ventricular fibrillation during coronary arteriography in dogs

RATIONALE AND OBJECTIVES

We studied the effect of the addition of sodium to nonionic contrast medium (CM) on the incidence of ventricular fibrillation (VF) during coronary arteriography in dogs.

METHODS

We infused 20 ml (0.5 ml/sec) of iohexol, iohexol plus 30 mmol of Na+ per liter, and NaCl-Ringer's acetate in randomized order through a wedged catheter placed in the right coronary artery (RCA) or in the left anterior descending coronary artery (LAD) in 12 anesthetized dogs. In addition to electrocardiographic and hemodynamic measurements, epicardial monophasic action potential durations and ventricular activation times were recorded during infusions into the LAD.

RESULTS

All infusions with iohexol into the RCA and the LAD (n = 16) caused VF. Seven of 19 infusions with iohexol plus 30 mmol of Na+ per liter caused VF. Infusions with iohexol plus 30 mmol of Na+ per liter that did not cause VF lengthened monophasic action potential durations and increased ventricular activation times more in the CM-perfused area than in the control area.

CONCLUSION

The addition of sodium to iohexol reduces the incidence of VF when infused through a wedged catheter. The protective mechanisms may be attributable to a lengthened repolarization phase and an increased activation time in the CM-perfused area.

Clinical pharmacology of iomeprol

The pharmacodynamic effects of iomeprol on the cardiovascular, central nervous, coagulation, and complement systems and on renal and thyroid functions using a wide range of intravenous and intraarterial radiological procedures were evaluated in Phase I, Phase II and Phase III clinical studies. The pharmacokinetics and metabolism of iomeprol were studied in healthy volunteers. Iomeprol 350 and 400 mgI/ml at doses ranging from 100 to 300 ml did not cause any significant changes of the basal haemodynamic parameters when used in CT of the chest and upper abdomen. No significant alterations of haemodynamic and ECG parameters were seen in patients who underwent cardiac-angiography or coronary angiography with iomeprol 400 mgI/ml. Intensive monitoring of haemodynamic and EEG parameters in patients undergoing conventional cerebral angiography with iomeprol 300 mgI/ml confirmed good toleration by the CNS. Neither renal and thyroid functions nor the coagulation and complement systems were significantly affected by iomeprol. Iomeprol was not metabolised and did not bind to plasma proteins. In healthy volunteers it was excreted almost exclusively by renal glomerular filtration (about 90% of the injected dose after 24 h). The pharmacokinetic behaviour of iomeprol was very similar to the behaviour of other nonionic, monomeric agents.

Contractile, metabolic and arrhythmogenic effects of ionic and nonionic contrast agents in the isolated rat heart

Intracoronary administration of contrast agents may be associated with contractile dysfunction and arrhythmias. To further establish the mechanisms of these alterations, we studied high-energy phosphate metabolism, developed pressure, the occurrence of arrhythmias, and the effects of verapamil during infusion of ionic and nonionic agents in isovolumic, retrogradely perfused rat hearts using 31P nuclear magnetic resonance imaging (NMR). Diatrizoate meglumine (Renografin) infusion reduced developed pressure (DP) to 17.1 +/- 3.4% (p less than 0.001) of the control level, and immediately following termination of the infusion, sudden ventricular tachycardia (VT) was observed in four of six hearts. In the presence of verapamil, meglumine reduced DP to 13 +/- 1.9% of control values and none of these six hearts developed VT. Iopamidol infusion in the presence of verapamil (n = 6) and alone (n = 6) resulted in a decrease in DP to 87% of control value, and no arrhythmias, significant change in high-energy phosphate levels, or changes in pH were observed. These results suggest that contrast-induced contractile depression is not mediated by changes in high-energy phosphate metabolism or pH. Arrhythmias associated with meglumine administration alone and suppressed by verapamil are probably related to calcium loading.

Adverse reactions of low osmolality contrast media during cardiac angiography: a prospective randomized multicenter study

A multicenter study was performed to determine the incidence of adverse reactions to two contrast media with similar low osmolality during cardiac angiography. The study was of a randomized double-blind design comparing ioxaglate (an ionic dimer) and iopamidol (a nonionic compound) and included 500 patients; 250 patients received ioxaglate and 250 iopamidol. There were 58 adverse reactions attributed to the contrast media in the ioxaglate group and 29 in the iopamidol group (p less than 0.001). Chest pain occurred in 11 patients in the ioxaglate group compared with 5 in the iopamidol group (p = 0.123). Nausea or vomiting was present in 20 and 2 patients, respectively (p less than 0.0003). Allergic adverse reactions, such as bronchospasm, urticaria and itching, occurred in 15 of the ioxaglate group and only 1 of the patients receiving iopamidol (p less than 0.0007). Fifty-two patients in the ioxaglate group had a known allergic history (not to contrast medium) or asthma, whereas 77 receiving iopamidol had a similar history. Seven of the 52 ioxaglate-treated patients developed an allergic adverse reaction compared with none of the 77 in the iopamidol group (p = 0.001). Of 41 patients receiving ioxaglate who were premedicated with diphenhydramine, 4 had an allergic adverse event. In the iopamidol group 45 patients received similar premedication and none had an allergic adverse reaction (p less than 0.03). Thus, this multicenter study shows that adverse reactions occur more often with ioxaglate than with iopamidol and that patients with an allergic history have a greater risk with ioxaglate therapy compared with iopamidol.

Ventricular fibrillation during coronary angiography: reduced incidence with nonionic contrast media

Ventricular fibrillation during coronary angiography with Renografin-76 has been attributed to the high osmolar ionic and calcium binding additive properties. Isovue-370 is a new low osmolar nonionic contrast medium lacking calcium binding additives. The present investigation compared the incidence of contrast media-induced ventricular fibrillation in patients undergoing coronary angiography with Renografin-76 to that with Isovue-370. Group I consisted of 2,000 consecutive patients undergoing coronary angiography with Renografin-76, and group II consisted of 2,000 subsequent consecutive patients in whom Isovue-370 was employed as the contrast medium. There was no significant difference between groups I and II with respect to volume of contrast media used per patient (125 +/- 35 vs. 140 +/- 45 ml), age (63.5 +/- 15 vs. 60 +/- 17 years), sex (74% male vs. 76% male), ejection fraction (55% vs. 55%), valvular heart disease (8% vs. 9%), prior coronary artery bypass graft surgery (5.8% vs. 5%), or extent of coronary artery disease. Contrast media-induced ventricular fibrillation occurred in 20 patients in group I (incidence 1%), whereas eight episodes occurred in group II (incidence 0.4%) (P less than 0.03). Thus the present investigation suggests that the incidence of ventricular fibrillation during coronary angiography can be significantly decreased by using low osmolar nonionic contrast media lacking calcium binding additives.

The potential risk of thrombosis during coronary angiography using nonionic contrast media

The influence of contrast media on coagulation has an important association with thromboembolic complication during coronary angiography. In this study, whole blood was methodically mixed with nonionic contrast medium, Iohexol (IOH), conventional ionic contrast medium, Hypaque-76 (H76), and low osmolar ionic dimer Hexabrix (HB) in vitro. The thrombotic propensity of contrast agents can be evaluated by measuring the clot formation of the mixtures. The experiments were repeated with whole blood after systemic heparinization. In the in vitro study, 5 ml of canine (N = 10) and 3 ml of human (N = 11) whole blood was incubated for 30 min in glass tubes with equal volumes of IOH, H76, HB, and 0.9% NaCl before heparinization. Clot formation with IOH and 0.9% NaCl were seen both in dogs (4.0 +/- 0.7 gm and 5.6 +/- 0.8 gm) and in patients (1.4 +/- 0.9 gm and 2.9 +/- 1.3 gm), whereas no clot was seen with H76 or XB. Following heparinization, no clot was visualized in any mixture of whole blood with contrast media or 0.9% NaCl. Similar results were observed in the catheter-syringe system with canine blood (N = 11) mixed with the contrast agents. Blood clots found in 15 min and 30 min of IOH were 0.07 +/- 0.08 gm and 0.44 +/- 0.20 gm (P less than 0.01) and of NaCl were 0.29 +/- 0.37 gm and 0.69 +/- 0.38 gm (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of low osmolality ionic (ioxaglate) versus nonionic (iopamidol) contrast media in cardiac angiography

A double-blind randomized study was performed in 60 patients to compare the electrocardiographic and hemodynamic changes induced during cardiac angiography by 2 contrast media with relatively low osmolality. Ioxaglate meglumine sodium, an ionic dimer contrast medium, was compared with iopamidol, a nonionic compound. Of the 30 patients who received ioxaglate, 13 (43%) experienced a mild to moderate adverse reaction to the contrast media, while only 2 of the 30 patients (7%) in the iopamidol group had similar side effects (p less than 0.005). Significant prolongations of the QT intervals occurred with the ioxaglate injections. The QT intervals increased from 402 +/- 46 to 442 +/- 59 ms (p less than 0.001) with the right coronary artery injection and similar changes were observed after the left coronary artery injection and left ventriculography. Significant ST-segment and T-wave amplitude changes also occurred in the ioxaglate group. With iopamidol injections, there were no significant changes in any of these parameters. After the left ventriculogram, there were similar decreases in the systolic arterial pressures in both groups (-14 +/- 10 mm Hg with ioxaglate and -21 +/- 9 mm Hg with iopamidol). The left ventricular end-diastolic pressures increased after the ventriculogram in both groups (5 +/- 5 vs 2 +/- 3 mm Hg with ioxaglate and iopamidol, respectively, 60 seconds after the injection). This report demonstrates that mild to moderate adverse reactions, QT-interval prolongations, ST and T-wave changes were significantly greater during coronary angiography with ioxaglate when compared with iopamidol.(ABSTRACT TRUNCATED AT 250 WORDS)