Cardiac Effects of Adding Electrolytes and Oxygen to Iohexol in a Dog Model of Contrast Media-Induced Ventricular Fibrillation

We investigated whether addition of a balanced electrolyte supplement and oxygen to the nonionic contrast medium iohexol reduces the risk of ventricular fibrillation (VF), and studied regional electrophysiology prior to the VF event. Twenty ml of each test solution were infused at a rate of 0.5 ml/s into the left anterior descending coronary artery (LAD) in 8 anesthetized dogs. LAD was externally occluded during infusion, to simulate a wedged catheter situation. ECG, hemodynamics, regional epicardial monophasic action potential duration (MAPD) and ventricular activation times (VAT) were calculated. All infusions with iohexol caused VF within 27 s. Five of 12 infusions with iohexol + 30 mmol NaCl, 3 of 11 infusions with iohexol + electrolytes (IPE) (NaCl, KCl, CaCl2 and MgCl2) and 4 of 11 infusions with IPE with oxygen addition (IPE + O2) caused VF after 45 s. Iohexol did not change MAPD prior to the VF event. Iohexol + 30 mmol NaCl and the IPE solutions lengthened MAPD initially, but at the time of the VF event MAPD were normalized or shortened. We conclude that electrolyte supplement to iohexol may prevent VF, probably by lengthening MAPD.

Significance of zinc in nephrotoxicity of contrast media used in imaging diagnostics of the cardiovascular system

Nephrotoxicity is an undesirable reaction of contrast media used in X-ray or magnetic resonance diagnostics. In addition to a direct toxic effect on renal tubules, the hemodynamic factor is considered to be the main cause of kidney damage and malfunction. The factors that increase the probability of a nephrotoxic effect of contrast media include oldage, diabetes, arterial hypertension, circulatory system insufficiency, neoplastic diseases, and prior kidney damage. Decreased serum zinc is observed in all those conditions. In this article, the influence of contrast media on zinc homeostasis and the possibility of a nephrotoxic reaction caused by these agents is discussed.

Prominent ECG repolarization changes associated with intracoronary infusion of normal saline: comparisons with alternate coronary catheter flush solutions

Normal saline (NS) is commonly used as a coronary catheter flush solution. We tested the hypothesis that intracoronary (i.c.) infusions of lactated Ringer's solution (LR) and LR with 5% dextrose (D5LR), both of which contain potassium and calcium, would be associated with less prominent surface ECG changes compared with i.c. infusions of NS. In 34 patients, 10 mL each of NS, LR, and D5LR at 37 degrees C were infused over 5 sec into the left main coronary artery. A 12-lead ECG was recorded before, continuously during, and after each infusion. Blinded ECG analysis revealed T-wave amplitude changes > 0.2 mV in 94%, 12%, and 3% of patients with the use of i.c. NS, D5LR, and LR, respectively (P < 0.0001, NS vs. D5LR or LR). QT prolongation > 40 msec occurred in 88%, 15%, and 18% of patients with i.c. NS, D5LR, and LR, respectively (P < 0.0001, NS vs. D5LR or LR). QT dispersion was increased by > 40 msec in 26% of patients during i.c. NS infusion compared to only 3% of patients with i.c. LR and D5LR infusions (P < 0.01). In conclusion, i.c. NS infusion is associated with more marked repolarization changes as compared with i.c. LR and D5LR infusions. Since such changes may lower arrhythmogenesis thresholds, the routine use of LR as a coronary catheter flush solution should be considered. Cathet. Cardiovasc. Intervent. 48:359-364, 1999.

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.

Coronary arteriography with an oxygenated contrast medium: cardiac effects in dogs with and without acute ischemic heart failure

RATIONALE AND OBJECTIVES

We investigated the possible cardiac effects of oxygen addition to contrast media (CM) during coronary arteriography in dogs that did and did not have ischemic heart failure.

METHODS

Acute ischemic heart failure was induced by injecting small plastic microspheres into the left coronary artery of 18 dogs. Hemodynamic and electrophysiologic measurements were performed during a single injection before and during heart failure and during a single injection and five rapidly repeated CM injections during heart failure. Iohexol supplemented with electrolytes (iohexol + electrolytes = IPE), oxygenated IPE (IPE+O), Ringer acetate, and oxygenated Ringer acetate were injected into the left coronary artery.

RESULTS

Single injections of IPE and IPE+O induced small hemodynamic and electrophysiologic effects. However, repeated injections of IPE and IPE+O increased left ventricular inotropy (maximum value of the first derivative of the left ventricular pressure) by 36% and 39%, reduced heart rate by 7% (for both), and lengthened QTc time (corrected QT interval) by 39 and 38 msec, respectively. A comparison of IPE and IPE+O revealed no statistically significant differences.

CONCLUSION

Although electrolyte addition to nonionic CM may reduce the risk of cardiac complications during coronary arteriography, oxygenation does not seem to significantly further reduce this risk.

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.

Changes in contractile function with low-osmolal and isosmolal contrast media for coronary angiography

Changes in contractile function induced by modern roentgen contrast media (CM) were examined in isolated rat hearts. Four coronary perfusions were undertaken in each heart with increasing volumes of each CM in order to test a wider spectrum of potential side-effects. Left ventricular developed pressure (LVDP) and heart rate (HR) were recorded. Six commercially available or investigational CM were examined: A, Hexabrix (ioxaglate 320 mg I/ml, Na 146 mM); B, Iosvist (iotrolan 300 mg I/ml, Na 6 mM);C, Visipaque (iodixanol 320 mg I/ml, Na 19 mM, Ca 0.3 mM); D, "Iodixanol high Ca-Mg" (iodixanol 320 mg I/ml, Na 19 mM, Ca 1.2 mM, Mg 0.6 MM); E, "Iohexol I 350" (iohexol 350 mg I/ml, Na 28 mM); and F, "Iohexol I 150" (iohexol 150 mg I/ml Na 28 mM). A, E and F were low-osmolal (400-940 mosm/kg H2O) CM whereas B, C and D were essentially isosmolal. Contractile changes (transient LVDP depression) was volume-dependent. Maximal values for LVDP depression were "Iohexol I 150" 11-22%<Iosovist 13-45% and Visipaque 18-45%<"Iodixanol high Ca-Mg" 14-62%<"Iohexol I 350" 40-76%<Hexabrix 92-96%. No changes observed in HR. The study revealed that cardiac function was hardly affected by CM which had the following characteristics: a low to normal osmolality (<400 mosm/kg H2O); a low concentration of contrast agent (150 mg I/ml); and an overall content of ions (Na 6-28 mM, Ca 0-0.3 mM) complying well with myocardial ratios of Na and Ca. Of the CM tested that may be in clinical use in coronary angiography (300-350 mg I/ml), Iosvist and Visipaque induced the least changes in contractibility.

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 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.

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.