Role of peripheral vasodilation in the hypotensive response to left ventriculography in anesthetized dogs

Hemodynamic Effects of Gadodiamide Injection and Gadopentetate Dimeglumine in Anesthetized Dogs

A nonionic (gadodiamide injection) and an ionic (gadopentetate dimeglumine) contrast medium were compared for their effect on hemodynamics in the anesthetized, open-chest dog. Both agents were administered i.v. over 15 s at dosages of 1.0 and 1.5 mmol/kg, in randomized order. Both contrast agents resulted in transient but statistically significant decreases in aortic pressure, left ventricular pressure, indices of left ventricular contractility and relaxation, and systemic and pulmonary vascular resistance, and increases in aortic blood flow. At each dosage investigated, the changes associated with the administration of gadodiamide injection were of significantly smaller magnitude than those seen after gadopentetate dimeglumine and returned to preadministration levels sooner. The results from this study confirm that gadodiamide injection produces less severe alterations in hemodynamics than gadopentetate dimeglumine.

Selection of a contrast agent in the cardiac catheterization laboratory

The evolution of contrast material for intravascular use has been directed toward the development of better-tolerated agents. Currently, a variety of such "dyes" are available for coronary angiography and left ventriculography. Considerable animal and human investigation suggests that significant differences exist between the families of contrast agents that relate to patient tolerance. The newer low osmolality agents (especially the nonionic agents) produce less perturbation of the homeostatic state, which is clinically manifested by a lessened incidence of side effects, including those of a hemodynamic and electrophysiologic nature. While controversy continues over the cost/benefit ratio of the low osmolality contrast agents compared to traditional high osmolality agents, the former are rapidly becoming the community standard for diagnostic and especially therapeutic cardiologic procedures. Accepting the advantages of the low osmolality contrast agents, differences between the ionic dimers and the nonionic agents have been examined. Both experimental and clinical data suggest superiority of the nonionic agents. Although controversy still surrounds the issue of thromboembolism with the nonionic agents, accumulating evidence fails to support a clinically significant relation. The choice of contrast material is the responsibility of the invasive cardiologist. While the benefits of low osmolality agents are most obvious in high-risk patients, experience with large-scale intravenous studies suggests that the choice of contrast agent is a better discriminator of adverse reaction than is preprocedural risk stratification.

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.

Left ventricular receptors: physiological controllers or pathological curiosities?

Mechanically and chemically sensitive receptors in the ventricle have been described histologically and electrophysiologically. Early experiments documented the hypotension and bradycardia that resulted from the intracoronary administration of one of the veratrum alkaloids (the Bezold-Jarisch reflex). Mechanical distension of the ventricles also results in a reflex decrease in heart rate and a reduction in peripheral resistance. Skeletal muscle and coronary vascular resistance appear to be most prominently affected by stimulation of ventricular receptors. Coronary ischemia has also been shown to evoke reflex effects which are attributable to stimulation of ventricular receptors. The resultant bradycardia can be especially ominous in acute myocardial infarction. Changes in myocardial inotropic state have been shown to alter ventricular receptor discharge in experimental animals. This stimulus may evoke reflex changes in peripheral hemodynamics. A variety of humoral substances can alter ventricular receptor discharge and evoke Bezold-Jarisch like responses. These include bradykinin and prostaglandins. PGI2, when given intracoronary in small doses or intravenously in larger doses will lower blood pressure while inhibiting the baroreflex induced tachycardia. It has also been shown in some experiments that PGI2 and arachidonic acid can evoke overt bradycardia and hypotension via a reflex mechanism. The role of prostaglandins in cardiovascular reflex control may be important in pathophysiologic states such as coronary ischemia and heart failure. Ventricular receptors can interact centrally with the arterial baroreceptors to attenuate the baroreflex control of both heart rate and peripheral resistance. Finally, the stimulation of ventricular receptors can alter a variety of humoral substances which are important regulators of cardiovascular and fluid volume homeostasis. These include vasopressin, renin and catecholamines. Those studies which have been done within the last 10 years or so, especially in unanesthetized animals, have demonstrated that the Bezold-Jarisch reflex is more important to cardiovascular control than previously thought. Future work will be necessary to determine the precise role ventricular receptors play in various pathological situations.

Changes in left ventricular diastolic function after left ventriculography: a comparison with iopamidol and urografin

Changes in left ventricular (LV) diastolic indices after left ventriculography (LVG) with iopamidol or urografin were studied in 42 subjects. Increase in heart rate and decrease in LV systolic pressure were more significant with urografin than with iopamidol (p less than 0.05 to 0.001). LV end-diastolic pressure was elevated more with urografin than with iopamidol (p less than 0.005 to 0.05) 1 to 3 minutes after LVG. LV peak negative dP/dt decreased significantly with urografin immediately (10 to 15 seconds, -511 and 30 seconds, -376 mm Hg/sec; p less than 0.0005 to 0.02), but with iopamidol it did not decrease significantly after LVG. Time constant, T, was elongated with iopamidol (10 to 15 seconds, +13 and 30 seconds, +6 msec; p less than 0.0005), but this elongation was significantly less than urografin (10 to 15 seconds, +34; 30 seconds, +25; 1 minute, +15; and 2 minutes, +10 msec; p less than 0.05 to 0.0005). We conclude that iopamidol disturbed LV diastolic function to a lesser degree than did urografin.