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Biomedical subjects

B L George

Publications and source records attributed to B L George.

25 records · Page 2Linked to original sources

Experience with the Fontan procedure.

From 1975 to the present, 45 patients have undergone modifications of the Fontan procedure for complex congenital heart disease. There were 30 males and 15 females ranging in age from 2 to 38 years (mean 13 years). Primary diagnoses were tricuspid atresia in 19, univentricular heart in 24, and pulmonary atresia with intact ventricular septum in two. Right atrial-pulmonary arterial connections were performed in 32 patients, 11 with conduits (seven with valves and four without) and 21 by direct anastomosis with patch augmentation. Right atrial-right ventricular connections were made in 13 patients, six with valved conduits and seven without conduits. Follow-up ranged from 0.1 to 9 years, with a mean of 2.3 years. There were three early deaths (less than 30 days) (7%) and two late deaths (5%) in this series, all in patients with a univentricular heart. The late deaths were both related to venous hypertension. A venous assist device was used in eight patients in the immediate postoperative period and was effective in improving cardiac output and reducing fluid accumulation. Postoperative Doppler flow studies in 15 patients revealed biphasic pulmonary artery flow in all without distinction between the type of connection or the presence of a valve. Cardiac catheterization was performed in 16 patients a mean of 14 months postoperatively (range 1 to 42 months) and revealed a reduced cardiac index at rest. Exercise testing in eight patients demonstrated a marked rise in right atrial pressure with a reduced rise in the cardiac index, even in those without functional limitations. With a mean follow-up of 2.3 years, 78% of patients were in New York Heart Association Class I, 17% in Class II, and 5% in Class III. We conclude that the Fontan procedure is an excellent operation in carefully selected patients with tricuspid atresia and other forms of complex congenital heart disease.

Adolescent↗

The effects of lanthanum and manganese on excitation-contraction coupling in the newborn rabbit heart.

The effects of 5 microM of lanthanum (La) and 0.5 mM of manganese (Mn) on myocardial mechanical function were studied in isolated, arterially perfused cardiac preparations of newborn and adult rabbits. The La-induced decrease in developed tension (DT) and maximal rate of tension development [+dT/dt(max)] was similar in the two age groups for the first 4 min of perfusion. La perfusion caused a significant rise in the resting tension (RT) of the newborn preparation, but not of the adult preparation. In the newborn, Mn perfusion resulted in a decrease in DT and +dT/dt (max) that was similar to the decrease induced by La. In the adult, however, the Mn-induced decrease in function occurred much more slowly than did that of La. In addition, the Mn-induced decrease in function in the newborn was significantly (p less than 0.005) greater than that of the adult. As with La, Mn caused a significant (p less than 0.001) increase in the RT of the newborn preparation only. These data show that there are significant age-related differences in the mechanical response of the myocardium to uncouplers of excitation-contraction. Furthermore, they suggest that the etiology of these differences may lie in the maturation of intracellular organelles that are responsible for the beat-to-beat regulation of myocardial contractility.

Aging↗

Effect of extracellular calcium on myocardial mechanical function in the neonatal rabbit.

The effects of extracellular calcium ([Ca2+]0) and barium ([Ba2+]0) on myocardia mechanical function were studied in the isolated arterially perfused neonatal and adult rabbit heart. The force of cardiac contraction per gram tissue in the newborn was approximately one third that in the adult for [Ca]0 of 1.5 mM. One half maximal values of developed tension (DT) and maximal tension first derivative [+dT/dt (max)] in the newborn were observed at [Ca2+]0 that were significantly higher than those in the adult. The maximal inotropic effect of calcium was observed at [Ca2+]0 of 10 mM in the adult and 30 mM in the newborn. Calcium binding to the isolated sarcolemma in the newborn and adult were identical. Cellular calcium in the newborn was significantly less than that in the adult. Barium infusion caused equal contracture in the newborn and adult, and the time to half maximal contracture was not different in the two age groups. These data indicate that (1) sarcolemmal permeability to divalent cations is similar in the newborn and adult rabbit, and (2) although calcium influx is similar in the two age groups, the amount of contractile calcium in the newborn is less than that in the adult for all [Ca]0.

Aging↗

Diagnosis and management of postoperative pulmonary hypertensive crisis.

In this paper we discuss two infants and one child who experienced a previously unreported complication after complete correction of a large, unrestrictive ventricular septal defect. Two patients had documented pulmonary hypertensive crises and severe right-heart failure secondary to hypoxia and pulmonary vasoconstriction. These crises were associated with significantly increased right ventricular (RV) peak systolic and end-diastolic pressures and right-to-left shunting via a foramen ovale which, in turn, exaggerated the hypoxis. The crises were treated successfully with tolazoline in the second and third patients. RV pressure returned to normal values and have remained normal up to 12 months postoperatively in the second patient. Although the RV pressures decreased with tolazoline in the third patient, they never reached normal values. Postoperative monitoring of pulmonary artery and RV pressures in infants with large ventricular septal defects is essential when unexplained complications are encountered. Tolazoline proved to be very effective in the treatment of two patients with pulmonary vasoconstriction secondary to hypoxia.

Heart Septal Defects, Ventricular↗

Exaggerated natural measles following attenuated virus immunization.

An adolescent girl, devoid of a detectable humoral immunity to measles virus despite two inoculations of live, attenuated vaccine, developed an exaggerated atypical rubeola illness following exposure to wild virus. This observation suggests that attenuated virus may be capable of immunologically sensitizing some individuals as has been described with killed virus vaccine.

Adolescent↗