Direct pharmacologic and osmolal effects of contrast media on the mechanics of heart muscle isolated from cats

Determining optimal acquisition parameters for computed tomography coronary angiography: evaluation of a software-assisted, breathhold exam simulation

RATIONALE AND OBJECTIVES

Scanning parameters used in multislice computed tomographic (MSCT) coronary angiography should be adapted to patients' heart rates. The aim of this study was to evaluate the rate of success of a software-assisted scan simulation to determine optimal gantry rotation time prior to MSCT coronary angiography.

MATERIALS AND METHODS

Data from 218 64-slice MSCT coronary angiographic studies were retrospectively analyzed. Prior to the MSCT examination, a scan had been simulated by giving a breath-hold command, after which a software program recorded the patient's heart rate from an electrocardiogram over the expected scanning time and predicted optimal scanning parameters. The success rate in predicting optimal parameters for the subsequent MSCT examination and the resulting acquisition window width were analyzed.

RESULTS

There was a wide range of heart rates among the patients. The mean intraindividual variation during scan simulation and examination was 4.8 beats/min. Optimal scan parameters were selected in 179 of 218 cases (82%). The median acquisition window width achieved in this group was 174 ms (range, 100-200), compared with 192 ms (range, 149-225) in cases in which suboptimal settings were selected (P < .001). Correct prediction occurred significantly more often in patients with low heart rates (<66 beats/min) than in those with higher heart rates (>or=66 beats/min) (93% vs 66%; P < .001).

CONCLUSIONS

The software-assisted scan simulation was a fast and simple procedure that allowed the selection of optimal computed tomographic parameters in >80% of patients. The procedure may be a useful adjunct to avoid unwanted synchronicity of gantry rotation and heart cycle and optimize temporal resolution in MSCT coronary angiography.

The effect of contrast material on transitional cell carcinoma viability

In this study, increasing contrast concentration and/or exposure time decreased the growth and adherence of transitional cell carcinoma cells. Similarly, several authors have shown that the toxicity of contrast material to vascular endothelial cells in culture is related to concentration and time of exposure; this toxicity is minimized if non-ionic, low osmolar contrast is utilized. Identical trends of increasing toxicity with increasing osmolality have been documented with kidney cell lines, vascular smooth muscle cells, myocardial cells, neural cells, human fibroblasts, rat mesenchymal cells, and rat hepatocytes. The toxicity of contrast material in malignant cells (human cervical carcinoma cell lines and prostate cancer cell lines) has also been documented. Factors other than direct cellular toxicity may also affect the ability of malignant transitional cells transported with contrast material to implant on other sites in the collecting system. Zhan et al have evaluated neutrophil adhesion to contrast-exposed vascular endothelial cells. These authors observed increasing cellular adhesion with decreasing contrast dose. This was not related to osmolality as there was no similar endothelial adhesion activation with equal osmolality solutions of non-contrast solutions. The authors felt that contrast material, therefore, caused some form of modulation of cell adhesion molecules. This theory is supported by research by Owens et al that shows increases in the adhesive properties of endothelial cells to platelets after contrast exposure, and Rasmussen et al who found decreased granulocyte adherence with contrast exposure. In our study, transitional cell carcinoma cultures were placed on a collagen substrate to encourage adherence. There was an increasing number of non-adherent cells with increasing contrast concentration and exposure time, which suggests an effect of the contrast on cellular adhesion as well (Table 1). Potier et al found that rat mesangial cells were more sensitive to the cytotoxic effects of contrast agents than the less differentiated human fibroblasts were. This might suggest that the more poorly-differentiated transitional cell carcinoma cells would not be as sensitive to contrast material as low-grade tumors. However, we did not observe any differences in the responses of high- versus low-grade transitional cell tumors to exposure to contrast material. Intravenous contrast administration can lead to multiple adverse reactions, such as cardiotoxicy, nephrotoxicy, and hemodynamic toxicity. This makes non-ionic, low-osmolality agents preferable to ionic, high-osmolality agents. However, direct introduction of material into the urinary collecting system for the evaluation of transitional cell carcinoma may be less prone to seeding of viable malignant cells if ionic, high-osmolar contrast agents are utilized. Additional considerations include potential masking of very small filling defects in the upper urinary tract through opacification with extremely concentrated contrast material. Also, cytologic abnormalities are worsened by exposure to ionic, high-osmolar contrast agents, thus, any specimens for cytologic analysis should be collected prior to utilization of any contrast agents.

Effect of contrast material on transitional cell carcinoma viability

OBJECTIVES

To assess the effects of contrast material on the viability of transitional cell carcinoma (TCC) cells and the ability of such cells to attach to a recipient bed, because seeding of TCC into the upper urinary tract is a possibility during retrograde pyelography or percutaneous procedures.

METHODS

Primary cultures of TCC cells were established and placed in either quarter, half, or full-strength contrast for 10 minutes or one-quarter strength contrast for 10, 30, and 60 minutes. Cells were then removed from the contrast agent, resuspended in urothelium-specific media, and incubated for 5 days, after which the cells were counted.

RESULTS

A pronounced decrease in cell viability was observed with increasing exposure time and contrast material concentration. Cells incubated for 10, 30, and 60 minutes with contrast yielded an average of 79%, 60%, and 12% of the control group growth, respectively (P <0.001). Likewise, plates incubated with quarter, half, and full-strength contrast yielded 79%, 27%, and 10% of the control group growth, respectively (P <0.001). The difference in the response of low-grade superficial and high-grade invasive bladder tumors was not statistically significant.

CONCLUSIONS

TCC cells that have been exposed to dilute contrast material for a short period are able to attach and grow on an adequate recipient bed. However, increasing the contrast concentration and/or the exposure time appears to decrease the viability and adherence of the TCC cells.

Selective coronary artery perfusion in vitro: a method to study cardiac effects of contrast media

RATIONALE AND OBJECTIVES

The authors evaluated selective perfusion of the coronary arteries in the isolated rat heart as a model for studying contrast medium-induced cardiac effects and compared the effects of iodixanol, iotrolan, and ioxaglate with this model.

MATERIALS AND METHODS

Isolated, spontaneously beating rat hearts were used. Control hearts were perfused in the Langendorff or the selective perfusion mode receiving Krebs Henseleit buffer. Contrast media were injected selectively into the left coronary artery. Left ventricular pressure and electrocardiographic parameters were monitored continuously throughout the experiments.

RESULTS

The stability of the selective perfusion preparation was similar to that of the conventional Langendorff preparation. Ioxaglate (0.3 g iodine per kilogram body weight) significantly (P < .05) depressed left ventricular contractility and decreased (P < .05) left ventricular pressure. Iodixanol and iotrolan had minor cardiac effects.

CONCLUSION

Selective coronary artery perfusion seems to be a suitable model for studying direct cardiac effects of contrast media. The nonionic dimers, iodixanol and iotrolan, induce only minor changes in cardiac function.

Comparison of cardiovascular changes after administration of gadodiamide injection and gadopentetate dimeglumine in dogs

RATIONALE AND OBJECTIVES

The authors compared the cardiovascular effects of gadodiamide injection and gadopentetate dimeglumine.

METHODS

Gadodiamide injection or gadopentetate dimeglumine, each at doses of 0.3 or 1.5 mmol per kilogram of body weight, or saline volume control was administered intravenously in the cephalic vein of anesthetized dogs. Hemodynamic parameters, electrocardiographic parameters, and peripheral flow were measured.

RESULTS

Neither the low or high dose of gadodiamide injection caused statistically significant (P < .05) changes in any of the measured cardiovascular parameters. High doses of gadopentetate dimeglumine, however, significantly decreased left ventricular and systemic blood pressure and significantly depressed left ventricular contractility (P < .05).

CONCLUSION

Gadodiamide injection caused no observable cardiovascular effects, whereas high doses of gadopentetate dimeglumine caused cardio-depressive and hypotensive effects.

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).

Double-blind comparison of the clinical, hemodynamic, and electrocardiographic effects of sodium meglumine ioxaglate or iohexol during diagnostic cardiac catheterization

The clinical effects and the maximal hemodynamic and electrocardiographic effects of two low-osmolality radiographic contrast media (ioxaglate and iohexol) were directly compared during diagnostic cardiac catheterization in a double-blind, randomized study in 80 patients. Because small changes were expected after injection of both of these agents, sensitive ECG and intracardiac-pressure-monitoring methods were used, and maximal changes, as well as mean changes in variables, were analyzed. Symptoms were absent, mild, or moderate in 67-77% of patients after left ventriculography and in 97-100% of patients after coronary arteriography. After left ventriculography, maximum and minimum left ventricular systolic pressure and end-diastolic pressure, the first derivative of left ventricular pressure (dp/dt), heart rate, were significantly altered over the two-minute observation period but were not different from the preinjection values at two minutes after both agents. Small but significant increases in mean aortic pressure, cardiac output, and pulmonary arterial wedge pressures were seen at two minutes after both agents.

Cardiovascular effects of iodinated contrast agents

The ideal intravascular contrast agent would be biologically inert and have no pharmacologic actions. Pharmacologic actions of currently used radiographic contrast agents are determined principally by 3 physicochemical properties of the iodine-bearing molecule and its formulation: osmolality, sodium concentration and calcium-binding properties. Within this framework, the calcium-binding 1.5 ratio agents have the most marked effects, and the 3.0 ratio nonionic agents the least, with the noncalcium-binding formulations of 1.5 ratio agents and ioxaglate (the only 3.0 ratio ionic agent) in between. Differences in hemodynamic effects are predominantly related to osmolality with the 3.0 agents causing less hemodynamic disturbance. The magnitude of difference is small enough that the 3.0 ratio agents have no important clinical advantage when used in patients with good or moderately impaired left ventricular function. However, the difference may be important in patients with severely impaired circulatory performance. The principal electrophysiologic differences are between the calcium-binding 1.5 ratio agents (which are associated with a clear-cut greater frequency of ventricular fibrillation during coronary injection than the noncalcium-binding 1.5 ratio agents) and the 3.0 ratio agents. There is no justification for the use of calcium-binding 1.5 ratio agents, since noncalcium-binding formulations of the same molecule are available at the same price. The circulatory reserve of most patients makes the differences between 3.0 ratio agents and noncalcium-binding 1.5 ratio agents clinically unimportant. In view of the substantial price disparity between 1.5 ratio and 3.0 ratio agents, noncalcium-binding 1.5 ratio agents are appropriate for patients with good circulatory performance and 3.0 ratio agents are best reserved for patients with impaired circulatory performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Electromechanical effects of two low osmolality contrast media, ioxaglate and iohexol, on isolated rat atria

This study aimed at investigating the direct effects of two low osmolality radiographic contrast media, iohexol (non-ionic) and ioxaglate (ionic), on transmembrane action potentials, contractile force and refractoriness of isolated rat atrial preparations. Superfused with 10% solution, ioxaglate induced a biphasic mechanical response, initially decreasing and thereafter increasing contractile force. The same concentration of iohexol only increased contractile force. The two contrast media increased the resting membrane potential, action potential amplitude and rate of depolarization to the same extent. Iohexol prolonged repolarization. Both contrast media decreased the effective refractory period. The direct effects of contrast media on myocardial contractility in this study can explain the different haemodynamic effects of iohexol and ioxaglate in vivo. The observed effects on the action potentials in vitro can explain commonly observed ECG changes during coronary arteriography. The changes in depolarization, repolarization and refractoriness are probably related to the arrhythmogenic properties of these contrast media.

Hemodynamic abnormalities during coronary angiography: comparison of Hypaque-76, Hexabrix, and Omnipaque-350

The hemodynamic effects induced by coronary angiography in dogs with low osmolar ionic dimer Hexabrix (HB) and nonionic Omnipaque-350 (OM) were compared to the standard ionic contrast medium, Hypaque-76 (H76), both in the normal heart and in one with simulated severe cardiac disease. Left coronary angiography was performed in 12 "normal" closed-chest dogs with 10-cc injections of H76, HB, and OM in a randomized, blinded fashion. The maximal change in the left ventricular (LV) systolic pressure (SP), mean aortic pressure (MAP), left ventricular end diastolic pressure (LVEDP), and LV dp/dt were recorded. The LVSP and MAP fell 30 +/- 3 mm Hg and 26 +/- 4 mm Hg with H76, 22 +/- 2 mm Hg and 19 +/- 2 mm Hg with HB, and 7 +/- 1.5 mm Hg and 5 +/- 1 mm Hg with OM (P less than .001). The LVEDP increased 4.8 +/- 0.5 mm Hg with H76, 3 +/- 0.5 mm Hg with HB, but only 0.2 mm Hg with OM (P less than .001). The LV dp/dt decreased 392 +/- 63 mm Hg/sec with H76 and 235 +/- 21 mm Hg/sec with HB, but increased 411 +/- 50 mm Hg with OM (P less than .001). In eight additional open-chest dogs, left coronary angiography was performed 1 hr after occlusion of the proximal LAD coronary artery and in the presence of a critical circumflex coronary artery (CX) stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Selenium deficiency and cardiac electrophysiological and mechanical function in the rat

Earlier studies have shown that selenium and vitamin E are important in maintaining normal cardiac function. The present study was designed to test the effect of sole selenium deficiency on electrophysiological and mechanical characteristics of the rat heart. Male weanling rats were fed a standardized vitamin E adequate but selenium deficient diet, or a control diet. Deficiency of selenium was verified by direct (tissue selenium analyses) and indirect (glutathione-peroxidase tissue analyses) methods. In vivo electrocardiographic recordings as well as in vitro electrophysiological and mechanical recordings did not reveal abnormalities in any of the two groups. In conclusion, earlier studies have shown that the combined deficiency of selenium and vitamin E leads to abnormal cardiac function. Selenium deficiency alone, however, does not appear to significantly affect cardiac function in the rat.

Differential hemodynamic effects of Hypaque-76 and Renografin-76 during coronary angiography: the role of calcium-binding additives

Hypaque-76 (H76) and Renografin-76 (R76) are nearly identical ionic contrast media, except that R76 binds more calcium than H76 because of the presence of sodium citrate and EDTA in R76. To determine whether the calcium-binding additives in ionic contrast media contribute to the hemodynamic effects of contrast media during coronary angiography, left coronary angiography was performed in anesthetized dogs. In nine closed-chest dogs, 10 cc of H76 and R76 were injected in each dog in a blinded, randomized fashion. The effect of H76 and R76 on left ventricular systolic pressure (LVSP) and left ventricular diastolic pressure (LVDP), on mean aortic pressure (MAP), and on left ventricular (LV) dp/dt was recorded. Compared with H76, R76 produced a greater decrease in the LVSP (77 +/- 25 mmHg vs 48 +/- 17 mmHg P less than .05), MAP (72 +/- 24 mmHg vs 38 +/- 18 mmHg P less than .01), and LV dp/dt (747 +/- 87 mmHg/sec vs 460 +/- 81 mmHg/sec P less than .01). In nine additional open-chest dogs, left coronary angiography was performed 1 hour after occlusion of the proximal LAD coronary artery. Seven cc R76 produced a 35 +/- 15 mmHg decrease in LVSP, compared with 20 +/- 9 mmHg with H76 (P less than .01). The LV dp/dt decreased 720 +/- 387 mmHg/sec with R76, compared with 462 +/- 222 mmHg/sec with H76 (P less than 0.05). Thus, R76 produces significantly greater hemodynamic abnormalities than H76. Contrast media lacking calcium-binding agents may be preferable for coronary angiography.

Hemodynamic and electrocardiographic consequences of high- and low-osmolality contrast agents for left ventricular angiography

The cardiovascular effects of two nonionic contrast agents with low osmolality (iohexol and metrizamide) were compared with one standard ionic, high-osmolality contrast agent (metrizoate) used for left ventricular (LV) angiography in patients with coronary heart disease. Metrizoate induced a marked elevation of LV end-diastolic pressure and LV systolic pressure and an increase in cardiac output after a delay of a few minutes. All these changes were significantly less severe with iohexol and metrizamide. Hypotension occurring 30 sec after LV angiography was observed only with use of metrizoate. All agents increased heart rate, but the increase after metrizoate was significantly more pronounced and prolonged. The PQ and QT interval was prolonged only by metrizoate. The subjective symptoms were significantly more marked with metrizoate than with the two other agents. Thus the new nonionic contrast agent iohexol and metrizamide produced markedly less hemodynamic and electrocardiographic disturbance than the ionic agent metrizoate.

Hemodynamic effects of contrast media during coronary angiography: a comparison of three nonionic agents to Hypaque-76

Coronary angiography with standard ionic contrast media is associated with marked alterations in cardiac hemodynamics because of the depressant effects of the contrast media on cardiac contractility. Nonionic contrast media have been reported to produce less hemodynamic alteration than standard ionic contrast media. However, there is no information on how one nonionic media compares to another. Thus we compared the hemodynamic effects of three nonionic contrast media, Iopamidol (IOP), Iohexol (IOH), and Ioversol (IOV) to each other as well as to the standard ionic contrast media Hypaque-76 (H76). In 20 closed-chest anesthetized dogs, we recorded the maximal change in left ventricular systolic pressure (LVSP), mean aortic pressure, left ventricular diastolic pressure (LVDP), and left ventricular dp/dt during 10-cc left main coronary artery injections of H76, IOP, IOH, and IOV. The mean aortic pressure and LVSP decreased 36 +/- 17 mm Hg and 46 +/- 21 mm Hg with H76 but only 5 +/- 5 mm Hg and 6 +/- 5 mm Hg with IOP, 5 +/- 4 mm Hg and 6 +/- 6 mm Hg with IOH, and 5 +/- 4 mm Hg and 7 +/- 6 mm Hg with IOV (P less than 0.001). The LVDP increased 6 +/- 5.0 mm Hg with H76 but only 0.2 +/- 0.5 mm Hg with IOP, 0.2 +/- 0.3 mm Hg with IOH, and 0.5 +/- 1.0 mm Hg with IOV (P less than 0.001). The LV dp/dt decreased 545 +/- 261 mm Hg/sec with H76 but increased 886 +/- 477 mm Hg/sec with IOP, 910 +/- 96 mm Hg/sec with IOH, and 473 +/- 335 mm Hg/sec with IOV (P less than 0.001). Whereas each nonionic agent produced significantly less hemodynamic abnormalities than H76, there was no significant difference between any of the nonionic agents on any hemodynamic parameter. Thus, as compared to H76, these nonionic contrast media produced only trivial alterations in hemodynamics and LV dp/dt. These agents may be preferable in patients with LV dysfunction.

Absence of myocardial biochemical toxicity with a nonionic contrast agent (iopamidol)

To evaluate the myocardial metabolic effects of a new nonionic contrast agent, iopamidol, a randomized, double-blind study was performed comparing iopamidol with sodium meglumine diatrizoate (Renografin-76) in 23 patients with ischemic heart disease. Coronary sinus and arterial metabolic samples were obtained prior to and during the 20-minute period following the contrast left ventriculogram. Ten patients received iopamidol and 13 received Renografin-76. The chemical lactate extraction in the iopamidol group was 13 +/- 9% prior to left ventriculography and 17 +/- 12% following the contrast injection (p less than 0.005). In the Renografin-76 group, the lactate extraction was 23 +/- 13% and decreased significantly to 12 +/- 24% following the ventriculogram (p less than 0.01). In a subset of these patients (n = 10), [1-(14)C] lactate was infused as a tracer to quantitate the amount of lactate released by the myocardium. [1-(14)C] lactate analysis demonstrated that the fall in lactate extraction ratio following Renografin-76 was due to an increase in myocardial lactate release. In the Renografin-76 group there was a 53 +/- 37% increase in lactate release at 10 minutes after contrast agent injection (p less than 0.005), while in the iopamidol patients there was no significant change in lactate release following contrast ventriculography. The increase in lactate release in the Renografin-76 group suggests that myocardial ischemia is induced with this ionic contrast agent. In comparison, the nonionic contrast agent is less toxic to the myocardium and is not associated with the biochemical changes of cellular ischemia.