Contrast media-induced ventricular fibrillation: an experimental study of the effects of dimeric contrast media during wedged catheter injection in dogs

A multicentre evaluation of the safety of intracoronary optical coherence tomography

AIMS

Optical coherence tomography (OCT) is increasingly being applied to the coronary arteries. However, the risks associated with the imaging procedure are not yet well defined. The purpose of the present multicentre registry was to assess the acute complications associated with the clinical use of intra-coronary OCT in a large number of patients.

METHODS AND RESULTS

Consecutive patients from six centres who had OCT examination were retrospectively included. All adverse events and complications, even if transient, were noted. Risks were categorised into: 1) self-limiting 2) major complications including major adverse cardiac events (MACE) and 3) mechanical device failure. A total of 468 patients underwent OCT examination for evaluation of: plaque (40.0%), percutaneous coronary intervention (28.2%) or follow-up stent tissue coverage (31.8%). OCT was performed using a non-occlusive flush technique in 45.3% with a mean contrast volume of 36.6+/-9.4ml. Transient chest pain and QRS widening/ST-depression/elevation were observed in 47.6% and 45.5% respectively. Major complications included five (1.1%) cases of ventricular fibrillation due to balloon occlusion and/or deep guide catheter intubation, 3 (0.6%) cases of air embolism and one case of vessel dissection (0.2%). There were no cases of coronary spasm or MACE during or within the 24 hour period following OCT examination.

CONCLUSIONS

OCT is a specialised technique with a relatively steep learning curve. Major complications are uncommon and can be minimised with careful procedural planning and having an awareness of the potential contributory risks, especially deep guide catheter intubation during contrast flushing. Upcoming developments will make OCT more practical and less procedurally demanding, also potentially conserving contrast volume considerably.

Signs in vector-electrocardiography (VECG) predicting the fibrillatory propensity of iodixanol and mannitol solutions after injection into the left coronary artery of pigs

RATIONALE AND OBJECTIVES

To find signs in vector-electrocardiography (VECG) predicting the ventricular fibrillatory propensity (VF-PROP) of iodixanol and mannitol solutions after injection into the left coronary artery (LCA) of pigs.

MATERIALS AND METHODS

Five plasma-isotonic solutions perfused LCA: Iod 320 + Na/Ca (iodixanol 320 mg I/mL, 19 mM NaCl, 0.3 mM CaCl(2)), Iod 320 + Mann (iodixanol 320 mg I/mL, 50 mM mannitol), Mann + Na/Ca (240 mM mannitol, 19 mM NaCl, 0.3 mM CaCl(2)), Mann (275 mM mannitol), and Ringer (representing "physiologic electrolytes"). The first two solutions have at 37 degrees C viscosity 13 mPas and the others <1 mPas. In eight pigs, 20 mL of each solution was injected twice for 10 seconds, and in 15 pigs, each solution was injected for 11-40 seconds (0.5 mL/second) through a wedged catheter in the LCA. If ventricular fibrillation (VF) occurred, injection was stopped and heart was defibrillated. If VF did not occur, perfusion period was 40 seconds. A higher frequency of VF and a shorter period from start of injection until start of VF gave a solution a higher ranking of VF-PROP.

RESULTS

The 10-second injections caused no VF. Ringer and Iod 320 + Na/Ca caused no VF after 40-second injections, whereas the other solutions caused VF. Ranking the solutions from lowest to highest VF- PROP gave: Ringer = Iod 320 + Na/Ca < Iod 320 + Mann < Mann + Na/Ca < Mann. Prolongation of QRS time and QTc time were the only VECG signs that showed significant differences (P < .05) between all solutions and correctly ranked the VF-PROP of all solutions in both animal groups.

CONCLUSION

The results fit with the concept that a more physiologic electrolyte composition and a higher viscosity of a test solution will, after start of injection of that solution into LCA, delay changes in the electrolyte composition in myocardial interstitial fluid and also delay start of VF. If a plasma isotonic contrast medium (CM) with lower viscosity than that of iodixanol at 320 mgI/mL were created, we conclude that such a CM should have electrolyte composition closer to that of Ringer than present composition (19 mM NaCl and 0.3 mM CaC1(2)) to counteract the effects of faster diffusion of nonphysiologic electrolyte composition from the low-viscosity CM to myocardial interstitial fluid.

[Contrast media and percutaneous coronary interventions]

Contrast media are widely used for percutaneous coronary interventions. Currently, about a dozen types of contrast media are available in France. On account of their overall safety, only low osmolar and isosmolar contrast media are used in practice. However, the appropriate use of contrast media remains difficult as accurate recommendations are lacking. Several doubts are still present regarding potential adverse effects of contrast media. Our review summarizes contrast media-related risks (hypersensitivity, arrhythmic risk, effects on coagulation and platelets, contrast media-induced nephrotoxicity) underlying mechanisms, prophylaxis strategies, and differences among contrast media. Many questions remain in this area and we need further prospective randomised trials.

Adding sodium and calcium ions to the contrast medium iodixanol reduced the risk of ventricular fibrillation during perfusion of the left coronary artery in pigs

RATIONAL AND OBJECTIVES

The effects of electrolytes, viscosity, and chemotoxicity of a plasma-isotonic iodine contrast medium iodixanol were compared with regard to its propensity to cause ventricular fibrillation (VF).

MATERIALS AND METHODS

The left coronary artery of pigs was perfused with five isotonic solutions: iodixanol 320 mg I/mL with 19 mmol/L NaCl + 0.3 mmol/L CaCl2, Iod 320+Mann (iodixanol 320 mg I/mL + 50 mmol/L mannitol), Mann+Na/Ca (240 mmol/L mannitol with 19 mmol/L NaCl + 0.3 mmol/L CaCl2), Mann (275 mmol/L mannitol) and Ringer. The first two solutions have at 37 degrees C a viscosity of approximately 13 mPa x s while the others have a viscosity < 1 mPa x s. In eight pigs, each test solution was injected twice into the left coronary artery in random order for 10 seconds (injection volume, 20 mL). In 15 pigs, each of the solutions was injected in random order for 11-40 seconds through the end-hole of a wedged 5F balloon catheter in left coronary artery. Injection rate was 0.5 mL/sec until VF occurred. If VF occurred, injection was stopped and the heart was defibrillated. If VF did not occur, the perfusion period was 40 seconds.

RESULTS

The 10-second perfusions caused no VF. The 40-second perfusions with iodixanol 320 mg I/mL with 19 mmol/L NaCl + 0.3 mmol/L CaCl2 or Ringer caused no VF (0%). Iod 320+Mann caused nine VF (60%) after 35 +/- 4 seconds (SEM). Mann+Na/Ca caused 14 VF (93%) after 30 +/- 2 seconds. Mann caused 15 VF (100%) after 24 +/- 2 seconds. Iodixanol 320 mg I/mL with 19 mmol/L NaCl + 0.3 mmol/L CaCl2 and Ringer caused fewer VF than all other solutions (P < .05-.001). Iod 320+Mann caused fewer VF than Mann (P < .05). Iod 320+Mann caused VF later than Mann+Na/Ca or Mann (P < .02 and P < .01). Mann+Na/Ca caused VF later than Mann (P < .05).

CONCLUSION

The results fit with a concept that VF starts when the electrolyte composition of the interstitial fluid in the myocardium is sufficiently nonphysiologic. The more physiologic the electrolyte composition of the perfusion fluid, and the higher its viscosity, the slower the composition of the interstitial fluid will be changed, and VF will occur later (or not at all).

Computer-assisted continuous ST-segment analysis for clinical research: methodological issues

Continuous ST-segment monitoring has been used to detect acute myocardial ischemia, determine the success of the reperfusion therapy, and predict outcomes in both research and a variety of clinical settings. However, analyzing the abundant electrocardiography (ECG) data recorded using continuous multilead ST-segment monitoring techniques is time consuming and requires expertise. Experienced data interpreters in dedicated ECG core laboratories handle many continuous ECG data records from large clinical trials. Little information on measurement issues for computer-assisted ST-segment analysis is available for individual investigators. Unsupervised or inexperienced computer analysis of ST-segment deviations can, under certain circumstances, yield invalid or unreliable summary indices. The goal of this article is to discuss basic ST-segment measurement principles in evaluating acute myocardial ischemia and methodological issues surrounding the use of computer-assisted ST-segment analysis for continuous ECG data. Variables affecting ST-segment measurements will be examined. Sources and examples of variability for these potential errors will be identified.

Experiences with iohexol and iodixanol during cardioangiography in an unselected patient population

AIM

To compare the frequency of adverse events after cardioangiography with iohexol and iodixanol in an unselected patient population with special regard to previously defined "risk patients": age> or =65 years, severe coronary artery disease, unstable angina pectoris and left ventricular dysfunction.

METHODS

A total of 1020 patients referred to cardioangiography were included in this open, prospective cross-sectional study, comparing iodixanol (320 mgI/ml) and iohexol (350 mgI/ml). Adverse events were recorded and the patients answered a questionnaire.

RESULTS

Cardiac adverse events (CAE) i.e., angina pectoris, arrhythmia and dyspnea within 24 h of examination were reported by 9% of patients receiving iohexol and by 7% receiving iodixanol. Two cases of ventricular fibrillation occurred, both after iohexol. The proportion of CAE was 11% for patients> or =65 years receiving iohexol and 7% in younger patients. For patients receiving iodixanol the proportion was 7%, in both age groups. Patients with severe coronary disease had more CAE than less ill patients in both CM groups. The proportion of unstable patients with CAE was 18% in the iohexol group and 12% in the iodixanol group. Left ventricular dysfunction was not related to CAE.

CONCLUSIONS

Iodixanol could be advantageous in patients with unstable angina.

Vectorcardiographic changes during cardioangiography with iodixanol and ioxaglate

AIM

To compare the electrophysiological effects of two contrast media (CM), the non-ionic dimer iodixanol and the ionic dimer ioxaglate using computerised dynamic vectorcardiography (VCG) during coronary angiography.

METHODS

The study was designed as a double-blind, three-period crossover, randomised comparison between iodixanol (320 mg I/ml) and ioxaglate (320 mg I/ml). Group 1 (HVV) received ioxaglate (H) in the first injection in the left coronary artery (LCA) and iodixanol (V) in the following injections. Group 2 (VHH) received iodixanol in the first injection in LCA and ioxaglate in the following injections. The first three injections in the LCA were subjected to electrocardiographic analysis.

RESULTS

For five out of six VCG variables, there was a significant difference in response between iodixanol and ioxaglate. For these five variables, the deviations from baseline were greater in the ioxaglate than in the iodixanol group (P<0.05). The most pronounced effects from ioxaglate were seen on the ST-segment and T-wave.

CONCLUSIONS

Iodixanol caused less pronounced electrophysiological changes than ioxaglate, especially during the repolarisation phase. Vectorcardiography is a sensitive and reproducible technique for detecting electrophysiological effects induced by CM.

The haemodynamic effects of iodinated water soluble radiographic contrast media: a review

All classes of iodinated water-soluble radiographic contrast media (RCM) are vasoactive with the iso-osmolar dimers inducing the least changes in the vascular tone. The mechanisms responsible for RCM-induced changes in the vascular tone are not fully understood and could be multifactorial. A direct effect on the vascular smooth muscle cells causing alterations in the ion exchanges across the cell membrane is thought to be an important factor in RCM-induced vasodilatation. The release of the endogenous vasoactive mediators adenosine and endothelin may also play a crucial role in the haemodynamic effects of RCM particularly in the kidney. In addition, the effects of RCM on blood rheology can cause a reduction in the blood flow in the microcirculation. The purpose of this review is to discuss the pathophysiology of the haemodynamic effects of RCM and to offer some insight into the biology of the endothelium and vascular smooth muscle cells as well as the pharmacology of the important vasoactive mediators endothelin and adenosine.

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 effects of ioxaglate (152 mmol/L sodium) and iohexol (no sodium) in a rabbit 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) was selectively injected into the right coronary artery (1.5 mL over 30 seconds) of 10 rabbits, some of which also received the alpha 1-adrenergic receptor agonist methoxamine. To validate the model, the class III antiarrhythmic agent clofilium was injected intravenously during methoxamine infusion. Frontal electrocardiography was performed continuously to detect polymorphic ventricular tachycardia (PVT). In a second study, the authors assessed the frequency of arrhythmias after injection of isotonic iohexol solution (145 mg of iodine per milliliter), either alone or with 150 mmol/L sodium.

RESULTS

Methoxamine significantly lengthened the QT, QTc, and RR intervals (P < .05). The use of clofilium alone induced no PVT, whereas five of eight methoxamine-infused rabbits developed PVT after clofilium injection (P = .03). Both contrast media prolonged the repolarization period. Iohexol alone induced a higher frequency of PVT than did ioxaglate alone (P = .0006). Methoxamine infusion did not potentiate the frequency of PVT in the ioxaglate-injected rabbits. The addition of sodium to isotonic iohexol prevented the occurrence of PVT (P = .0006).

CONCLUSION

Although ioxaglate prolonged 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.

Preclinical safety assessment of contrast media: predictive value

The purpose of preclinical tests is to identify the potential benefits and risks of new diagnostic or therapeutic products. Regarding iodinated contrast media (CM), LD50 tests were used extensively in the past. However, from both scientific and ethical perspectives, it is today highly relevant to question the use of LD50 tests. Due to species differences and the very high volume of CM needed to kill half of the animals, such tests are not sensitive enough to differentiate between modern nonionic CM. Further, they are not very predictive in terms of human tolerability. In other tests with more relevant end-points than death, overall tolerance to the new dimeric compound iodixanol (Visipaque), representing the latest step in the development of CM, has been shown to be higher than to the nonionic monomers. Clinical experience has shown that the physiological parameters often stay closer to baseline after Visipaque than after administration of conventional CM.

Sodium-calcium balance in coronary angiography and experimental experience with iodixanol

The present short review describes the physiological effects of rapid transient changes in cardiac extracellular ions (electrolytes) caused by the bolus of x-ray contrast medium (CM) during coronary angiography. The underlying hypothesis is that as the molecular and osmolal toxicities of modern CM is low, cardiac side-effects result mainly from secondary and biphasic ionic changes which occur during the initial washout phase and during the later reintroduction of blood. In particular, the washout pattern for sodium (Na) and calcium (Ca) has great influence on cardiac function. Thus the Na-Ca exchange system of the cardiac cell membrane plays a pivotal role in controlling intracellular Ca and contractility during very brief coronary bolus injections of both nonionic and ionic CM. The nonionic dimeriodixanol is hyposmolal without an additive. Animal experiments demonstrate the value of taking myocardial Na-Ca relationships into careful consideration when adding ions to iodixanol and formulating an isotonic CM like Visipaque.

Contrast-medium-induced ventricular fibrillation: arrhythmogenic mechanisms and the role of antiarrhythmic drugs in dogs

RATIONALE AND OBJECTIVES

Small electrolyte additions to a nonionic contrast medium reduce the risk of ventricular fibrillation (VF) during wedged catheter injection of a contrast medium. The current study was designed to further investigate contrast-medium-induced VF by studying the effect of pretreatment with different antiarrhythmic drugs.

METHODS

During a simulated wedged catheter situation, iohexol was injected into the anterior descending branch of the left coronary artery in five open-chest, anesthetized dogs pretreated with lidocaine, propranolol, amiodarone, almokalant, or verapamil.

RESULTS

Wedging the catheter for 60 sec did not induce VF. However, all 15 wedged catheter injections with iohexol induced VF within 28 sec (19 +/- 1 [mean +/- standard error of the mean]) despite pretreatment with antiarrhythmic drugs. Prior to VF, conduction was slowed and monophasic action potential duration lengthened in the contrast-medium-perfused myocardium, although no significant changes occurred in the control area.

CONCLUSION

The combination of catheter wedging and long-lasting contrast medium injection has a high risk of causing VF. Although adding a small amount of electrolytes to nonionic contrast media can reduce the risk of VF, antiarrhythmic drug therapy may not have a protective effect.

Additive hemodynamic and electrophysiologic effects of repeated intracoronary contrast media injections in dogs with heart failure

RATIONALE AND OBJECTIVES

We investigated the cardiac effects of single and repeated contrast media injections in dogs with heart failure and compared the effects of iohexol with iohexol supplemented with electrolytes (30 mmol/l NaCl, 0.15 mmol/l CaCl2, 0.9 mmol/l KCl, and 0.1 mmol/l MgCl2; iohexol + electrolytes [IPE]). Although it has a higher osmolality than iohexol, IPE appears to be safer when injected through a wedged catheter.

METHODS

Acute ischemic heart failure was induced by injections of small plastic microspheres into the left coronary artery of 16 anesthetized dogs. Iohexol, IPE, and Ringer acetate were injected into the left coronary artery either as a 5-ml single injection or repeatedly five times, once every 10th second.

RESULTS

Single injections of iohexol and IPE induced small hemodynamic and electrophysiologic effects. However, repeated injections of iohexol and IPE increased the maximum rate of isovolumetric contraction by 46% and 36%, reduced heart rate by 8% and 7%, and lengthened QTc (the Q-T interval corrected for heart rate) time by 44 and 39 msec, respectively. No statistically significant differences were found in a comparison of IPE and iohexol.

CONCLUSION

During heart failure, repeated injections of iohexol and IPE induced similar additive hemodynamic and electrophysiologic effects without inducing arrhythmias or serious hemodynamic changes.

Cardioangiography and the hemodynamic effects of iodixanol

Patient safety should be in focus when using contrast media (CM) in diagnostic and interventional cardiac procedures. Side-effects that occur during cardioangiography due to hemodynamic effects of CM include direct effects on the heart, effects on the systemic and pulmonary circulation, and effects on the blood volume. Although not a totally inert solution, iodixanol (Visipaque) has less pronounced direct inotropic effects on the heart than have other CM; its vasodilatory effects on peripheral arteries are smaller, and the increase in blood volume is smaller after administering iodixanol than after other CM. Thus, iodixanol represents a further step forward in terms of reducing side-effects during contrast-enhanced diagnostic and interventional cardiac procedures.

Cardiac effects of iodixanol compared to those of other nonionic and ionic contrast media on the isolated rat heart

This study was designed to compare the cardiac electrophysiology and mechanical effects of iodixanol to those of iotrolan, iopromide, ioxaglate and diatrizoate. Two consecutive injections of contrast media (CM) (0.3 g I/kg and 0.9 g I/kg b.w.) were given to spontaneously beating, Langendorff-perfused rat hearts. CM were given as a single, short-lasting bolus injection (i.e. over 2 and 5 s). Changes in aortic pressure, left ventricular pressures and ECG were continuously recorded during constant volume perfusion. The nonionic CM had less pronounced effects on aortic pressure than had the ionic media. The peak rate of isovolumetric contraction (LV dP/dt(max)) was slightly decreased by iodixanol and iotrolan, slightly more decreased by iopromide and markedly decreased by ioxaglate and diatrizoate. Similarly, the peak rate of pressure decline (LV dP/dt (min)) was only slightly decreased by iodixanol and iotrolan. Also, the 2 nonionic dimers had the smallest effects on the left ventricular end diastolic pressure (LVEDP) and heart rate. Ioxaglate lengthened the PQ-interval, but less so than diatrizoate. THe QT-interval was only slightly lengthened by iodixanol and iotrolan, as compared to the lenghthening caused by iopromide, ioxaglate and diatrizoate. Single ventricular extrasystoles were seen in all groups. Extrasystoles up to 3 coupled beats were registered after ioxaglate and diatrizoate. No episodes of ventricular fibrillation occurred with any CM. In conclusion, the nonionic dimers, and in particular iodixanol, induce only minor changes in cardiac function, whereas the ionic dimer ioxaglate and the ionic monomer diatrizoate induce pronounced effects.

Sodium-calcium relationships and cardiac function during coronary bolus perfusion

The present review deals with the side-effects of contrast media (CM) on cardiac function during coronary angiography. A physiological approach is used to redefine existing concepts of CM osmotoxicity and chemotoxicity in terms of osmolal, ionic and molecular effects. The main idea conveyed is that purely ionic effects are of central importance during and immediately following the transit of a brief coronary bolus. Ionic effects result largely from rapid transient washout of normal extracellular ions, but are also influenced by ions present in the CM. In particular, the calcium (Ca) and sodium (Na) ions controlling cardiac function are easily affected. The myocardial Na-Ca exchange, which is mainly a physiological mechanism for cellular Ca efflux during cardiac relaxation, is therefore highlighted in detail. The importance of avoiding a potential Na-Ca mismatch is shown by examples from basic physiology, cardiac surgery and coronary angiography and by results of experiments with Visipaque. In the isomolal and isotonic CM Visipaque, which is based on the dimer isodixanol (320 mg I/ml), an available osmolal space is filled with an appropriately balanced supplement consisting of NaCl (19mM) and CaCl2 (0.3 mM).