Investigators have sought to improve contrast agents by changing the ionic content or decreasing osmolarity. This study compared the effects of meglumine sodium diatrizoate, sodium meglumine calcium metrizoate, and metrizamide on coronary blood flow, myocardial contractile force, and perfusion pressure under normal and ischemic conditions in eight isolated canine hearts. Diatrizoate had an initial negative inotropic effect, but contractile force returned to baseline within 1 minute during normal perfusion and within 2 minutes under ischemic conditions. Calcium-enriched metrizoate and metrizamide had only a positive inotropic effect under normal perfusion (127 +/- 3.9% and 116 +/- 2.9% of baseline, respectively). During ischemia, however, the positive inotropic effect of sodium meglumine calcium metrizoate was followed by a decrease in contractile force to 93 +/- 5% of baseline after 2 minutes. Metrizamide showed only a positive inotropic effect during ischemia. The myocardial depression that follows the initial positive inotropic effect of calcium may further alter the instability between normal and ischemic areas of the heart, thus increasing the risk of coronary arteriography in patients with severe coronary artery disease.

Angiography↗

PubMedDate not supplied

Effect of angiographic contrast agents on the mechanical performance of the isolated rat papillary muscle preparations.

The effects of the radiographic contrast agents Renografin, Isopaque, and Hypaque on the mechanical performance of isometrically contracting rat papillary muscle was compared to a new contrast agent, Amipaque. It was found that exposure to Amipaque resulted in significantly less depression of contractile activity than any of the other agents. Changes in mechanical performance associated with exposure to Renografin, Isopaque, or Hypaque could not be attributed to either hypocalcemia or hypoxia. The decrease in developed tension and increase in resting tension was similar to that produced by Krebs-Henseleit containing hypertonic (1420 mmol) glucose or sucrose. Thus, the data support the concept that hyperosmolarity of the radiographic contrast agents may be primarily responsible for the adverse effects on mechanical performance of the myocardium associated with angiography.

Angiography↗

PubMedDate not supplied

Intracoronary thallium-201 assessment of thrombolysis in acute myocardial infarction. Validation of the method of imaging before and after therapy.

In order to study acute changes in perfusion with intracoronary thrombolytic therapy, we have used ten times the pretherapy intracoronary thallium-201 dose for the posttherapy study. Because of the larger posttherapy dose, the posttherapy images had ten times as many counts as the pretherapy images. Since the change in image quality between the pretherapy and posttherapy studies might affect interpretation, we studied the effect of image statistics on interpretation of perfusion scintigraphy. The pretherapy and posttherapy images were scored on a four-point scale in five segments on each of three views. In 31 patients, Poisson-distributed pseudorandom noise was added to the posttherapy study in order to match the statistical accuracy of the pretherapy study. A blinded interpretation of the pretherapy and posttherapy noise-added images was performed in the same way as the initial unblinded interpretation. The mean difference between the unblinded pretherapy and posttherapy scores (the improvement in thallium distribution with therapy) was 2.5+/-0.8 (standard error) compared with the difference between the blinded pretherapy and posttherapy noise-added scores which was 2.6+/-1.0. The correlation between readings of similar pairs of data was higher than the correlation between pretherapy and posttherapy studies. Thus, the difference in statistic quality of the pretherapy and posttherapy studies did not affect the interpretation of these studies. Therefore, our evaluation of pretherapy and posttherapy studies using a ten-fold increase in thallium-201 dosage is valid.

Coronary Vessels↗