Intracardiac electrography in children and young adults.

The interpretation of IE recorded in children has been hampered by a lack of agreement regarding normal values. We recorded IE in 158 children and young adults (ages, three days to 33 years) to define the various conduction intervals in normal and disease states. The HBP was recorded in 156 subjects. In 85 subjects with normal conduction indicated by surface ECG, including 19 subjects with normal hearts, there were no statistically significant age-related differences in internodal, A-V nodal, or His-Purkinje conduction intervals. Therapeutic levels of digitalis did not alter the conduction intervals. In 11 subjects with first degree A-V block and in five subjects with congenital complete A-V block, the site of block as determined by IE could not be predicted from the surface ECG. No abnormalities in conduction intervals were found in 18 subjects with right bundle branch block (surgically induced in 17 cases). Intracardiac electrography with recording of the HBP was found to be a safe, informative technique for electrophysiologic investigations in children and young adults.     

Right ventricular myxoma

We recently treated a patient with right ventricular myxoma and a clinical picture of pulmonary embolism and tricuspid valve obstruction who had successful removal of the tumor through the tricuspid valve via a right atriotomy.     

Dose-response studies of the suppression of whole blood histamine and basophil counts by prednisone

If some clinical problems (e.g., radiographic contrast media reactions) arise from mediator release by circulating basophils, prednisone's capacity to prevent such is likely to be at least partly related to its suppressive effects on whole blood histamine and basophil levels. To establish an optimal dosage schedule, 15 healthy male volunteers entered a two-phased study to determine (1) the single dose of prednisone required to produce maximal suppression of histamine and basophil levels and (2) the effects of repeated prednisone doses. Parameters monitored were whole blood histamine, quantitative basophil counts, white blood cell (WBC) and differential counts, and plasma prednisone, prednisolone, and cortisol levels. Fifty milligrams prednisone suppressed whole blood histamine levels as much as a larger dose and also showed a marked effect on circulating basophils and other leukocytes. Three 50-mg prednisone doses given at 6-hr intervals had a greater effect on whole blood histamine and circulating leukocytes than fewer doses. Thus, the commonly used empirical prednisone dosage regimen is supported. One implication of the results of this study is that greater suppression of blood basophils and histamine levels might be obtained by administering the last prednisone dose about 6 hr before procedures in which a very rapid release of mediators from basophils is anticipated.     

Hemodynamic effects of an oral dopamine receptor agonist (fenoldopam) in patients with congestive heart failure

Dopamine receptor stimulation causes vascular and neurohumoral responses that may be beneficial in patients with heart failure. Oral inactivity, emesis and adrenergic-induced arrhythmias have limited the use of currently available compounds. Fenoldopam (SKF-82526-J) is a new, orally available, selective, dopamine-receptor agonist with potent renal vasodilating properties (six times that of dopamine) without positive inotropic or adrenergic activity. Drug efficacy was clinically evaluated in 10 patients with heart failure after single oral doses of placebo and 50, 100 and 200 mg of medication. Placebo produced no changes. Peak efficacy was noted 30 minutes to 1 hour after the 200 mg dose with mean blood pressure decreasing from 96 +/- 15 (mean +/- SD) to 83 +/- 8 mm Hg (p less than 0.05), pulmonary capillary wedge pressure decreasing from 23 +/- 6 to 20 +/- 8 mm Hg (p less than 0.05) and mean pulmonary artery pressure decreasing from 32 +/- 9 to 29 +/- 8 mm Hg (p less than 0.05). Systemic vascular resistance decreased from 1,987 +/- 887 to 1,191 +/- 559 dynes.s.cm-5 (p less than 0.05) with a subsequent 55% increase in cardiac index from 2.2 +/- 1.1 to 3.1 +/- 1.3 liters/min per m2 (p less than 0.05). Heart rate and right atrial pressure did not change (p greater than 0.05). No emesis or new tachycardia was noted at any dose. Baseline hemodynamics generally returned within 3 to 4 hours. Fenoldopam, therefore, is a short-acting, orally effective drug that decreases systemic vascular resistance and increases cardiac index in patients with heart failure and represents a new class of oral compounds that may be useful in treating such patients.