Direct positive inotropic effect of mannitol on the intact canine heart

Effects of new intravascular contrast agents on [Ca2+]i transients and contraction in cultured ventricular myocytes

We examined the effects of four kinds of intravascular contrast agents (amidtrizoic acid, iohexol, iopamidol, and ioxaglic acid) on [Ca2+]i transients (indo-1 fluorescence) and cell contraction (video motion analyzer), using cultured chick embryo ventricular myocytes. Exposure of ventricular myocytes to amidtrizoic acid (a conventional contrast agent) reduced the [Ca2+]i transients and the sensitivity of the contractile elements to [Ca2+]i. Ioxaglic acid (a low osmotic contrast agent) also reduced the [Ca2+]i transients, but did not significantly change the sensitivity of the contractile elements to [Ca2+]i. Neither iohexol nor iopamidol (nonionic contrast agents) reduced the [Ca2+]i transients, but both significantly decreased the sensitivity of the contractile elements to [Ca2+]i. A marked negative inotropic effect of amidtrizoic acid was caused by both calcium binding and hypertonicity. The less marked depression of contractility produced by ioxaglic acid is possibly the result of calcium binding, but is not caused by hypertonicity. The negative inotropism produced by nonionic contrast agents (iohexol and iopamidol) was due to hypertonicity, but not due to alterations in the [Ca2+]i transients. Exposure of ventricular myocytes to nonionic contrast agents (iohexol and iopamidol) slowed decay in the [Ca2+]i transients with increased end-diastolic [Ca2+]i. After washing out the nonionic contrast agents, these parameters returned to control levels. On the other hand, exposure to amidtrizoic acid decreased end-diastolic [Ca2+]i without changing decay time in the [Ca2+]i transients. After washing out amidtrizoic acid, there was a prolongation of half decay time in [Ca2+]i transients with a significant increase in end-diastolic [Ca2+]i and cell position. Diastolic dysfunction just after washout of amidtrizoic acid was possibly caused by an increase in [Na+]i due to sodium influx during exposure to the contrast agent.

Effects of a new nonionic and a conventional ionic contrast agent on coronary sinus ionized calcium and left ventricular hemodynamics in dogs

Transient myocardial depression associated with intracoronary injections of contrast medium has been attributed to hypertonicity and to calcium binding. To further assess the importance of calcium binding, a new technique for continuous monitoring of coronary sinus ionized calcium with an intravascular calcium-selective electrode was used. With this calcium-selective electrode the effects of intracoronary injection in dogs of a conventional ionic contrast agent, sodium meglumine diatrizoate (Renografin-76), and a new nonionic agent, iohexol, were assessed and compared. Left ventricular pressure was measured with a micromanometer catheter. After bolus injection of 0.2 ml/kg body weight of Renografin-76 (n = 10), coronary sinus pCa increased by 0.27 from 2.98 +/- 0.02 to 3.25 +/- 0.03, indicating a decrease in ionized calcium from 2.0 to 1.1 mEq/liter. With iohexol (n = 9), pCa increased by only 0.05 +/- 0.01 (p less than 0.001), indicating a decrease in ionized calcium from 2.0 to 1.8 mEq/liter. Peak changes occurred approximately 6 seconds after injection. Renografin-76 caused a marked decrease in left ventricular systolic pressure (140 +/- 7 to 106 +/- 8 mm Hg) and in heart rate (122 +/- 7 to 101 +/- 5 beats/min) with an increase in end-diastolic pressure (5 +/- 1 to 12 +/- 1 mm Hg), whereas iohexol did not significantly alter these variables. Using Renografin-76 with calcium added to achieve an ionized calcium level of 2 (n = 4), 4 (n = 4) or 6 (n = 4) mEq/liter, the changes in coronary sinus pCa were abolished and the hemodynamic changes attenuated. These findings indicate that Renografin-76 results in greater myocardial depression than the new nonionic agent iohexol.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of myocardial depression in experimental hemorrhagic shock by pretreatment with hydrocortisone

The left anterior descending or left circumflex coronary artery was cannulated in ten dogs. 4 mg/kg hydrocortisone were slowly infused and the cannula was withdrawn. The dogs were then subjected to hemorrhagic shock for 90 minutes followed by retransfusion. The contractile force (CF) and its first derivative (df/dt) were measured in the pretreated (infused) area and in a control (non-perfused) area of the left ventricle. During the shock period, CF and df/dt in the non-pretreated area showed a 50% reduction in comparison to the pre-shock level, whereas the contractile force in the area that had been pretreated with hydrocortisone did not change when compared to the pre-shock period. This study shows that myocardial depression secondary to hemorrhagic shock can be effectively prevented by pretreatment with hydrocortisone.