Maturational changes in left and right ventricular electromechanical intervals in the newborn lamb.

Electromechanical intervals of right and left ventricles were examined in newborn lambs (9 hours to 42 days). The electromechanical interval of the left ventricle did not change with maturation, while that of the right ventricle became progressively longer, resulting in an increasing ventricular mechanical asynchrony. We postulate that the pattern of developing mechanical asynchrony described may occur secondary to postnatal changes in ventricular morphology.

Chromosome damage in infants and children after cardiac catheterization and angiocardiography.

Current diagnostic cardiac studies in infants and children result in longer x-ray exposure times and in more angiocardiograms per patient. Blood samples removed before and immediately after such studies in 20 infants and children have shown chromosome damage in all. The damage was equal to an in vitro absorbed dose in the range of 20 to 50 rads. Since the effect was considerably greater than that calculated from the x-ray exposure dose to the patient, it is concluded that the damage is mainly due to the contrast agent used in angiocardiography. Long-term follow-up studies on such patients are indicated.

Absorbed dose in the presence of contrast agents during pediatric cardiac catheterization.

Administration of x-ray contrast agents during heart catheterization examination increases the absorbed radiation dose in tissue. To estimate the dose absorbed by the blood of children undergoing diagnostic heart catheterization and angiocardiography, a number of measurements and calculations were conducted. First, entrance and exit exposures to the patient were measured with thermoluminescent dosimeters calibrated for the diagnostic x-ray energy range. Second, a dose enhancement factor was calculated from mass energy absorption coefficients for various concentrations of the contrast media and at selected x-ray energies. Third, the dose enhancement factor was estimated from survival of peripheral blood lymphocytes suspended in varying concentrations of the contrast agent during exposure to graded doses of x-rays. Fourth, a mean absorbed dose to the patient's blood was calculated using (a) the dose enhancement factor determined above, (b) an estimate of the mean exposure in the irradiated body volume calculated from the entrance and exit exposure measurements, (c) an effective iodine concentration in the blood during the exposure time, and (d) a ratio correcting for the distribution and circulation of the blood. For eight pediatric patients monitored, absorbed doses to the blood ranged between 3 and 12 rad. These values were two to three times greater than the expected dose without administration of a contrast agent.