Cardiac catheterization is among the most performed medical procedures in the modern era. There were sporadic reports indicating that cardiac arrhythmias are common during cardiac catheterization, and there are risks of developing serious and potentially life-threatening arrhythmias, such as sustained ventricular tachycardia (VT), ventricular fibrillation (VF) and high-grade conduction disturbances such as complete heart block (CHB), requiring immediate interventions. However, there is lack of systematic overview of these conditions.

To systematically review existing literature and gain better understanding of the incidence of cardiac arrhythmias during cardiac catheterization, and their impact on outcomes, as well as potential approaches to minimize this risk.

We applied a combination of terms potentially used in reports describing various cardiac arrhythmias during common cardiac catheterization procedures to systematically search PubMed, EMBASE and Cochrane databases, as well as references of full-length articles.

During right heart catheterization (RHC), the incidence of atrial arrhythmias (premature atrial complexes, atrial fibrillation and flutter) was low (< 1%); these arrhythmias were usually transient and self-limited. RHC associated with the development of a new RBBB at a rate of 0.1%-0.3% in individuals with normal conduction system but up to 6.3% in individuals with pre-existing left bundle branch block. These patients may require temporary pacing due to transient CHB. Isolated premature ventricular complexes or non-sustained VT are common during RHC (up to 20% of cases). Sustained ventricular arrhythmias (VT and/or VF) requiring either withdrawal of catheter or cardioversion occurred infrequently (1%-1.3%). During left heart catheterizations (LHC), the incidence of ventricular arrhythmias has declined significantly over the last few decades, from 1.1% historically to 0.1% currently. The overall reported rate of VT/VF in diagnostic LHC and coronary angiography is 0.8%. The risk of VT/VF was higher during percutaneous coronary interventions for stable coronary artery disease (1.1%) and even higher for patients with acute myocardial infarctions (4.1%-4.3%). Intravenous adenosine and papaverine bolus for fractional flow reserve measurement, as well as intracoronary imaging using optical coherence tomography have been reported to induce VF. Although uncommon, LHC and coronary angiography were also reported to induce conduction disturbances including CHB.

Cardiac arrhythmias are common and potentially serious complications of cardiac catheterization procedures, and it demands constant vigilance and readiness to intervene during procedures.

The risks of ventricular fibrillation (Vfib) associated with frequency-domain optical coherence tomography (OCT)/optical frequency domain imaging (OFDI) remain undetermined.

We retrospectively studied the occurrence of Vfib during OCT/OFDI for unselected indications. The frequency of Vfib and patient and procedural characteristics were investigated. A total of 4,467 OCT/OFDI pullback examinations were performed in 1,754 patients (median of 2.0 [2.0-3.0] pullbacks for 1.0 [1.0-1.3] vessels). OCT/OFDI was performed during PCI in 899 patients (51.3%). The contrast injection volume per pullback was 14.4 (11.7-17.2) mL with a flow rate of 3.4 (3.2-3.5) mL/s. Vfib occurred in 31 pullbacks (0.69%) in 30 patients (1.7%). No cases of Vfib occurred when using low-molecular-weight dextran. On multivariate analysis, contrast volume was the only independent factor for predicting Vfib (odds ratio, 1.080; 95% confidence interval, 1.008-1.158, P=0.029). The best cutoff value of contrast volume for predicting Vfib was 19.2 mL (area under the curve, 0.713, P<0.001; diagnostic accuracy, 87.1%).

The present large, single-center registry study indicated that Vfib during OCT/OFDI was rare for unselected indications. Contrast injection volume used to displace blood should be limited to avoid Vfib.

To assess the incidence, investigate the predictors and analyze the causes of ventricular fibrillation (VF) during coronary angiography (CA) on the condition of current techniques.

From April 2004 to January 2007, a total 22,254 patients (27,798 procedures) received CA procedures in our center; 27 patients developed VF during CA. This report was to retrospectively analyze the clinical basic characteristics, coronary angiographic characteristics and CA procedure records of these patients.

The incidence of VF during CA was 0.097%. The incidence of VF in radial approaches and femoral approaches was 0.076% and 0.147% (p = 0.085). The VF patients had higher coronary artery bypass grafting (CABG) rates (11.1% vs 2.3%, p = 0.024) and were more likely to have a three-vessel disease (59.3% vs 31.2%, p = 0.002) and a total occlusion lesion (25.9% vs 11.1%, p = 0.014) than non-VF patients. On logistic regression analysis, three-vessel disease (OR: 2.582, 95% CI: 1.165-5.720, p = 0.019) and the history of CABG (OR: 3.959, 95% CI: 1.160-13.513, p = 0.028) were the two independent predictors of VF occurrences. Among 27 episodes of VF, 13 were ischemia-related; 11 were manipulation-related; two were contrast-related; one was hypokalemia-related; and the causes remain unclear in five episodes.

The incidence of VF during CA is low on the condition of current techniques. The severity of coronary artery disease (CAD) is an independent predictor of VF occurrence during CA. Acute ischemia and inappropriate manipulation may be the two main causes in VF development.

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.

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.

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.

Ventricular fibrillation (VF) developing out of hospital or even in hospital has a reported prognosis for survival that is <50%. We examined the prognosis for VF in 19,497 patients undergoing percutaneous coronary intervention and identified 164 who had VF (0.84%). The time to defibrillation was <1 minute and was successful in all without sequelae. Thus, VF developing in the catheterization laboratory is unique in terms of prognosis.

The ECG is an indispensable tool in the ICU for the detection and diagnosis of heart disease. ECG abnormalities however can be present in a wide variety of noncardiac conditions, complicating the differential diagnosis with primary cardiac pathology. This overview discusses the ECG abnormalities and their pathophysiologic basis in the most frequently encountered noncardiac conditions, such as electrolyte abnormalities, pulmonary embolism, CNS diseases, esophageal disorders, hypothermia, and drug-related and other conditions. Knowledge of the characteristic ECG changes may provide early clues to the presence of these disorders, the prompt recognition of which can be life saving.

Radiographic contrast media (CM) are necessary to provide x-ray absorption of the bloodstream; all other observed effects need to be regarded as adverse. Four types of CM are currently used in diagnostic and interventional cardiology: ionic high-osmolar CM (HOCM), either ionic or non-ionic low-osmolar CM (LOCM), and non-ionic iso-osmolar CM (IOCM). Focusing on the potential cardiovascular effects caused by the CM, there is a clear difference between HOCM and the LOCM or IOCM. HOCM have a poorer profile due to a higher incidence of hypotension and electrophysiological effects. To prevent contrast-induced nephropathy, HOCM should be avoided and patients should receive the minimal dose of LOCM or IOCM with intravenous hydration before and after the procedure. Clinical hyperthyroidism has been detected after CM use, but the condition appears, ultimately, to be self-limited and to occur mainly in elderly patients. When assessing the need for a CM in terms of improved patient safety, preventing serious complications should be the major factor determining the choice. CM should not be selected on the basis of minor adverse effects since these are, ultimately, of low clinical relevance. Thrombotic events, in contrast, carry a high clinical relevance and we consider that these should be the main issue governing current choice. Ionic LOCM appear to have better profile than other CM with respect to interaction with platelet function and coagulation. In relation to thrombotic events in randomised clinical studies, ionic CM have been associated, mainly, with favourable and some neutral results compared with non-ionic agents. Only one trial indicated a more pronounced antithrombotic effect of the non-ionic IOCM relative to the ionic LOCM. The antithrombotic advantages of ionic over non-ionic LOCM are, in part, balanced by a greater frequency of minor adverse effects such as nausea, vomiting or cutaneous rashes. A matter of concern is the delayed adverse effects observed with non-ionic IOCM. However, severe and life-threatening reactions are exceptional and there are probably no significant differences between IOCM and LOCM whether ionic or non-ionic. However, in patients with known allergies, non-ionic CM are to be recommended. On the basis of the available pre-clinical and clinical data, the ionic LOCM or the non-ionic IOCM are the agents to be recommended in percutaneous coronary interventions because of their antithrombotic advantages over non-ionic LOCM.

Ventricular fibrillation (VF) is not an infrequent complication of percutaneous transluminal coronary angioplasty (PTCA). However, it is not clear why there is a marked discrepancy in the higher incidence of VF during right coronary artery (RCA) approach.

We analyzed in detail every case of VF occurring in 905 consecutive PTCA procedures to investigate possible mechanisms. Sixteen patients (M/F=15/1, mean age: 71 +/- 8 years) with VF during PTCA for the RCA as Group I. Those 51 patients (M/F=48/3, mean age: 70 +/- 9 years) without VF during PTCA for the RCA engagement were designated as Group II. Patients were equipped with cardiac event recorder (CardioCall, Reynolds Medical, UK) before the PTCA, and we set the time period 1 min before and after the event. The lead II was selected to check the QRS width, QTc interval, ST segment change and RR interval before and after event. A total of 905 PTCA procedures were included. There were 561 procedures for the left coronary artery and three events (0.5%) with spontaneous VF. However, there were 16 events (4.6%) of VF during 344 PTCA procedures for the right coronary artery. The incidence of VF for the right side PTCA was significantly higher than for the left side. The orifice of RCA in Group I was smaller than Group II (orifice of RCA in Group I vs. Group II - 2.7+/-0.8 vs. 4.1+/-1.2 mm, P<0.001). Most cases (68.7%) presented with ST segment depression before the onset of VF.

A small caliber of RCA and associated ST segment changes played important roles in the patients with VF during the PTCA.

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.

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.

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.

Iodixanol could be advantageous in patients with unstable angina.

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.

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.

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.

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.

Previous studies have proposed that sodium supplement to nonionic contrast media (CM) can decrease the risk of ventricular fibrillation (VF). This study was designed to compare the occurence of VF induced by ioxilan (containing 9 mmol/LNa+) with other nonionic CMs. After wedging a catheter in the right coronary artery, test solutions including ioxilan, ioversol, iomeprol, and iopromide were infused for 30 sec at the rate of 0.4 ml/sec or until VF occurred. Then, incidence of VF, contact time (i.e. the time required to produce VF), and QTc were measured. Also, the CMs other than ioxilan were investigated at sodium levels adjusted to 9 and 20 mmol/L Na+. The incidence of VF with ioxilan (0%) was the lowest of all. In the other CMs, the incidence decreased in accordance with increase of sodium. Iomeprol and iopromide showed significant reduction of VF incidence at the sodium level of 20 mmol/L. The higher sodium supplements also prolonged the contact times. The increase of QTc was the greatest in ioxilan. Ioxilan has the least arrythmogenic property among the current low-osmolality nonionic CMs. This property might be attributable to an optimal sodium concentration of 9 mmol/L in the CM.

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.

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.

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.

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.

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.

We investigated the cardiac effects of an ionic dimer, ioxaglate and two nonionic dimers, iotrolan, and iodixanol.

During a simulated wedged catheter situation, 22 ml of each contrast medium was injected into the left anterior descending branch of the left coronary artery in seven open-chested, anesthetized dogs.

Of 13 injections with each contrast medium, ioxaglate induced ventricular fibrillation in 11 after 34 +/- 5 sec, iotrolan in 6 after 42 +/- 4 sec, and iodixanol in 3 after 61 +/- 1 sec. Ioxaglate markedly lengthened monophasic action potential duration in contrast medium-perfused myocardium. Iotrolan, and iodixanol induced biphasic changes, first lengthening and then shortening action potential duration. The electrophysiological changes occurred later when using iodixanol.

The risk of ventricular fibrillation during long-lasting contrast media exposure to the myocardium, as in a wedged catheter situation, appears to be much lower with iodixanol compared with ioxaglate and also lower than when using iotrolan.

Controversy exists as to whether low-osmolality radiographic contrast agents, which have less detrimental pharmacological effects but are considerably more expensive than high-osmolality agents, should be used universally or only for selected high-risk patients.

A randomized, double-blind study was used to compare the frequency and severity of adverse events in 2245 consecutive patients undergoing diagnostic cardiac angiography. Two thousand one hundred sixty-six patients were successfully randomized to either iohexol, a low-osmolality contrast agent, or diatrizoate (as Hypaque 76), a high-osmolality agent. The end point event included clinically important adverse events (which jeopardized the patient or required aggressive treatment), contrast agent-related procedure abbreviations, and conversion to open-label contrast agent. Clinically important end point events were associated with increased age, New York Heart Association functional class, left ventricular end-diastolic pressure, arteriovenous oxygen difference, severity of coronary artery disease, and history of a previous reaction to contrast agent. End point events were less frequent in patients receiving iohexol (2.6% versus 4.6%; adjusted odds ratio, 1.59; 95% confidence interval, 0.97-2.60; P = .07). The difference in event frequency between iohexol and diatrizoate was confined to the highest-risk quartile of the patient population. An algorithm was developed to classify patients as being at high or low risk for an event based on patient age, New York Heart Association class, history of a prior contrast reaction, and left ventricular end-diastolic pressure. Application of this algorithm for selective use of low-osmolality agents only for high-risk patients to a theoretical population of 1000 patients reduced contrast agent costs 66% without increasing the frequency of contrast agent-related adverse events.

The advantages of low-osmolality contrast agents are clinically important in patients with severe heart disease but are not in less ill patients. Universal use of low-osmolality agents for cardiac angiography in an unselected population is not necessary. Appropriately guided selective use of low-osmolality contrast agents is feasible and has the potential to reduce cost substantially without compromising safety or effectiveness.

We conducted an economic analysis to assess the extent to which a reduction in adverse drug reactions induced by low osmolality compared with high osmolality contrast media during diagnostic angiocardiography would result in savings to hospitals, society and third-party payers that would offset the substantially higher price of low osmolality contrast medium.

Substitution of low osmolality for high osmolality contrast media in the approximately 1 million diagnostic angiocardiographic procedures performed each year in the United States could substantially increase health care costs. Cost-effectiveness estimates should include savings that might occur through reduced costs of managing adverse drug reactions.

In a randomized clinical trial of 505 persons under-going diagnostic angiography with either high osmolality or low osmolality contrast medium, we measured and compared 1) material costs of contrast media, and 2) costs from three perspectives of incremental resources used to manage contrast-related adverse drug reactions. We also performed sensitivity analyses to examine the effect of different assumptions with regard to relative risk, absolute risk and costs of adverse drug reactions on estimates of net cost of use of high osmolality and low osmolality contrast media.

One-hundred thirty-seven (54.2%) of 253 patients receiving high osmolality contrast medium and 44 (17.5%) of 252 patients receiving low osmolality contrast medium experienced adverse drug reactions. The average cost (from society's perspective) of resources used to manage adverse drug reactions per patient undergoing angiography was significantly (p = 0.0001) greater for high osmolality (mean $249) versus low osmolality (mean $92) contrast medium. Differential costs (from the hospital's perspective) were $67 greater for high osmolality contrast medium. Charges and professional fees (from the payer's perspective) were $182 greater for high osmolality (mean $312) than for low osmolality (mean $130) contrast medium (p = 0.42, NS). The higher differential and average costs of managing adverse drug reactions with high osmolality contrast medium offset 33% and 75%, respectively, of the $207 difference in mean material costs, but these estimates are sensitive to infrequent high cost cases.

Although low osmolality contrast medium is not cost-saving in diagnostic angiocardiography, its higher price is partially offset by lower management costs of adverse drug reactions. The cost offset for the hospital is lower than that for society and may not be realized by third-party payers. These methods and results may be useful in establishing clinical and payment guidelines for use of alternative contrast media in diagnostic angiocardiography.

Low osmolar contrast agents produce less adverse electrophysiologic and hemodynamic alterations during cardiac catheterization. The nonionic agents probably reduce the risk of provoking myocardial ischemia during coronary arteriography or ventriculography. Patients also report less subjective sensation of discomfort during administration of low osmolar agents for cardiovascular procedures. However, nonionic agents have not been proved to reduce the incidence of several serious complications of cardiac catheterization, including acute renal failure and anaphylactoid reaction. Although evidence is inconclusive, there may be an increased risk of thromboembolic complications during cardiac catheterization when certain low osmolar nonionic agents are administered. Nonionic contrast agents have not been definitely proved to reduce the risk of death after cardiac catheterization.

Low-osmolality contrast agents produce fewer hemodynamic and electrophysiologic alterations during cardiac angiography, but they are 20 times more expensive than high-osmolality contrast agents. In a randomized, double-blind trial comparing a nonionic low-osmolality contrast agent (Omnipaque 350) with a high-osmolality agent that does not avidly bind calcium (Hypaque 76) in 505 patients undergoing cardiac angiography, we determined the incidence of minor, mild, moderate, and severe adverse reactions, identified risk factors for such reactions, and evaluated the cost effectiveness of various strategies for the use of contrast material.

The 253 patients who received a high-osmolality contrast agent were three times more likely to have a moderate adverse reaction (95 percent confidence interval for the relative risk, 1.6 to 5.5) but no more likely to have a severe reaction (95 percent confidence interval, 0.2 to 2.3) than the 252 patients who received a low-osmolality agent. All 10 severe reactions occurred in patients who were older than 60 years or had unstable angina. Patients with these characteristics were also 3.5 times more likely (95 percent confidence interval, 1.8 to 6.8) to have a moderate reaction (44 of 310 patients, or 14 percent) than those without either characteristic (8 of 195 patients, or 4 percent). We estimated that the incremental cost of each moderate reaction avoided would be $1,698 with a strategy that involved giving a low-osmolality contrast agent only to patients who were over 60 years of age or had unstable angina, instead of giving a high-osmolality agent to all patients. The incremental cost per moderate reaction avoided by giving a low-osmolality contrast agent to all patients rather than only to those over 60 or with unstable angina would be $5,842.

The use of contrast agents with low rather than high osmolality during cardiac angiography reduces the risk of moderate, but not of severe, adverse reactions to the agent used. A strategy of reserving low-osmolality contrast agents for use in patients at high risk for adverse reactions would be more cost effective than one requiring their use in all patients.

Ionic and nonionic contrast materials are similarly efficacious in providing excellent images with minimal risk to the patient. In comparison with ionic media, the nonionic agents produce minor alterations in intracardiac and peripheral pressures as well as in electrocardiographic intervals and morphology. In addition, nonionic media are less often associated with undesirable symptoms, such as flushing and vomiting. At the same time, ionic and nonionic media are accompanied by a similar incidence of nephrotoxicity, serious arrhythmias, and death. Finally, nonionic contrast material is substantially more expensive than ionic media. In light of this marked difference in cost, one could argue that nonionic media should be reserved for "high-risk" patients, that is, those with a history of a serious adverse reaction to ionic contrast media and those in whom contrast-induced hypotension would be particularly deleterious.

Low osmolal contrast agents (LOCA) are measurably superior to high osmolal contrast agents (HOCA) in a number of properties. However, LOCA are substantially more expensive than HOCA, and universal use of LOCA for cardiac angiography would strain the health care budget. Therefore, the choice to use LOCA in place of HOCA should be based on clinically important differences. Review of available published data suggests that HOCA can be used safely and effectively for cardiac angiography in patients with mild or moderately severe heart disease. When HOCA are used, those that do not bind calcium should be chosen as they cause fewer clinically important adverse reactions than those that do bind calcium. Use of LOCA may offer added safety in high risk patients, although to date, this conclusion has not been proved with clinical experience. Nonionic LOCA may be safer to use than ionic LOCA.

Radiographic procedures which require the intravascular administration of water-soluble radiocontrast media are performed with increasing frequency. Each examination carries risks that are related either to the technique itself or to the opaque medium chosen. The pathogenesis of radiocontrast media-related adverse effects cannot be explained by a unique theory. The major factors implicated are direct chemotoxic effects and the physicochemical properties of contrast media, the latter being the basis for development of new contrast agents. With nonionic opaque media cardiovascular adverse effects, heat sensation and local pain are observed less frequently. However, it remains unclear whether the incidence of organ dysfunction or anaphylactic reactions with nonionic contrast media currently used can be reduced. This review compares ionic and nonionic contrast media, and current thoughts on the pathophysiology and treatment of adverse reactions are presented.

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)