Effect of heparin in nonionic contrast media on blood coagulation and its dose response curve

Impact of contrast agent type (ionic versus nonionic) used for coronary angiography on angiographic, electrocardiographic, and clinical outcomes following thrombolytic administration in acute myocardial infarction

The goal of this study was to examine the relationship between contrast agent type (ionic vs. nonionic) and angiographic, electrocardiographic, and clinical outcomes after thrombolytic administration. Ionic or nonionic contrast agents were selected in a nonrandomized fashion for 90-min angiography and percutaneous coronary intervention (PCI) following thrombolytic administration in the TIMI 14 trial [tissue plasminogen activator (tPA) or reteplase (rPA) vs. low-dose lytic + abciximab]. There was no relationship between contrast agent type and overall patency, rate of TIMI grade 3 flow, or corrected TIMI frame counts (CTFCs) in open culprit arteries and in post-PCI patency rates or post-PCI CTFCs. In patients treated with ionic contrast, ejection fractions at 90 min were slightly but significantly lower (56.2 +/- 16.5, n = 122, vs. 59.8 +/- 14.4, n = 322; P = 0.02), chest pain duration was longer (2.8 +/- 4.1 hr, n = 255, vs. 1.7 +/- 3.6, n = 550; P = 0.0003), and complete ST segment resolution was less frequent (41.5% vs. 50.8%; P = 0.04). While there was no difference in epicardial blood flow, ionic contrast agent use was associated with poorer ST segment resolution, longer chest pain duration, and poorer ejection fractions, perhaps as a result of microvascular dysfunction.

Influence of contrast media on blood coagulation

RATIONALE AND OBJECTIVES

Contrast agents have been reported to influence the blood clotting system to an extent depending mainly on whether the compounds are ionic or nonionic. The objective of the current series of studies was to determine interspecies differences; the effect of variable incubation times; and the effect on thromboplastin times (TPT) of adding heparin to a number of x-ray and magnetic resonance imaging (MRI) contrast agents. In addition, the stability of clots formed in the presence of iopromide was studied. In a final experiment, the effect of the contrast agents on the bleeding time was studied in rats.

METHODS

Nine x-ray and three MRI contrast agents were used in the study. Thromboplastin times was determined in platelet-poor plasma of humans, rats, rabbits, or dogs using calcium (Ca) thromboplastin from human placenta or rabbit brain and lung tissue and incubation times as long as 4 hours. Bleeding times were determined in rats 5 minutes, 4 hours, 24 hours, and 48 hours after intravenous injection of the contrast agents by making a small incision into the tail of the animal, immersing the tail in saline, and measuring the time period during which small blood streaks were visible.

RESULTS

Nonionic contrast agents (x-ray and MRI) increased the TPT by a factor of 1.5 to 2, whereas ionic compounds prolonged TPT by a factor of > 3. Thromboplastin times increased in the order of dog < rabbit < rat < human 2- to 4-fold. However, the ranking of different contrast agents remained unchanged. Prolongation of bleeding time lasted as long as 24 hours for some contrast agents. Clots formed in the presence of iopromide were unstable and did not absorb the contrast agent.

CONCLUSIONS

The animal models used in the current series of studies seem to be valid for predicting the effect of contrast agents on the blood clotting system in humans.

Radiographic contrast media and the coagulation and complement systems

Intravascular contrast agents have several side effects including alterations of the hemostasis and the complement system. The effects on these systems may be one of the main causes of the "adverse contrast agent reaction." In vitro and in vivo evidence is provided that both ionic and nonionic contrast media activate the plasma kallikrein with consecutive activation of the factor XII-contact phase and stimulation of the bradykinin generation. Furthermore, activation of the complement cascade via the classic and the alternative pathways was described to a various extent for intravascular application of contrast agents. In non-reactors, these alterations are transient and only have a limited extent indicating that these reactions are within the regulatory capacity of the kallikrein-kinin-factor XII system. In reactors, however, significant evidence for an extended activation of the kallikrein system is associated with reduced levels of C1-esterase inhibitor. Therefore, patients with alterations in these systems should be regarded as candidates for adverse contrast agent reactions. Furthermore, contrast media influence the blood coagulation, especially in contact to artificial surfaces (plastic or glass). In vitro findings suggest that there is a broad scope of modifications caused by contrast agents indicating a modification of the risk of thromboembolism during angiography. Preliminary data suggest that an inhibition of clot formation is more effective with ionic compared with nonionic contrast agents. In summary, radiographic contrast agents have an impact both on the hemostasis and the complement systems. The effects may be of importance for adverse reactions as well as for thromboembolic complications during angiography.

Unsuccessful pericardiocentesis for cardiac tamponade during angiocardiography with nonionic contrast material

Cardiac tamponade secondary to ventricular wall perforation is one of the possible complications of right-sided as well as left-sided cardiac catheterization. Ventriculography was performed on a patient with obstructive cardiomyopathy using a nonionic contrast medium. During the procedure, the right ventricle was accidentally perforated and the patient developed cardiac tamponade. Pericardiocentesis was unsuccessful and surgical drainage was needed after the patient developed progressive hemodynamic deterioration. At surgery, pericardial thrombus was found. We consider the reason for failure of pericardiocentesis was rapid coagulation of the extravasated blood in connection with nonionic contrast material.