Giora Ben-Shachar

Infective endocarditis in infants and children during the past 10 years: A decade of change

Abstract Infective endocarditis (IE) is closely associated with congenital heart diseases. 1–9 In major series done over several decades up to the early 1970s 2,6 and in a recent review 8 both the changing pattern of etiologic agents and the increasing incidence of IE overal has been stressed. In the last decade, the practice of pediatric cardiology has changed greatly. New diagnostic methods such as M-mode and two-dimensional echocardiography (2DE) have been developed. The rate of survival, particularly that of infants and of children with complex heart diseases, has greatly increased, coincident with improved surgery and intensive care of severely ill infants and children. Advances have also occurred in the antibiotic armamentarium. With these multiple recent developments it was questioned whether a change might have also taken place in the pattern of IE. Few reviews, however, dealing with the pattern of pediatric IE over the last decade are available. 8–10 This report is a review of our experience in diagnosis and treatment of pediatric IE during the last decade (1972 to 1982).

Development of infundibular obstruction after percutaneous pulmonary balloon valvuloplasty

A 14 month old boy with suprasystemic right ventricular pressure secondary to pulmonary valvular stenosis and anular size of 10 mm underwent percutaneous balloon valvuloplasty with a 12 mm balloon. Right ventricular pressure almost doubled after valvuloplasty and the electrocardiogram revealed development of severe right ventricular strain. Both findings persisted on the following day. A postvalvuloplasty right ventriculogram demonstrated a severe systolic infundibular obstruction not present before. The patient underwent surgical relief of infundibular obstruction; successful opening of the pulmonary valve by the balloon valvuloplasty was observed. It is concluded that a balloon size 20% larger than anular size can be safe in human subjects and that infundibular obstruction may appear or even worsen after balloon valvuloplasty. Such an obstruction may be related to the severity of pulmonary valvular obstruction and a hypercontractile infundibulum.

Intelligence and hypoxemia in children with congenital heart disease: fact or artifact?

Previous studies have reported lower intelligence for cyanotic than for acyanotic children with congenital heart disorders, a finding attributed to the degree of hypoxemia present. Several important variables have not been examined consistently, however, including coexisting neurologic or genetic disorders, definitive surgery, degree of sickness, age at testing sex and social class. The present study examined the relation of these variables to obtained intelligence measures for 82 consecutively admitted children, excluding children with abnormal neurologic examinations and those having received definitive surgery. Consistent with earlier reports, intelligence quotients for the acyanotic children (112.81 +/- 14.52 mean +/- SD) were significantly higher (t = 2.60; p = 0.006) than for the cyanotic group (103.50 +/- 15.81). Although sex, race and social class were not significantly different between the 28 cyanotic and the 54 acyanotic children, the cyanotic children were significantly sicker (x2 = 9.12; p = 0.005) and younger (t = 4.10; p = 0.001). However, when young and old children and the degree of sickness within cyanotic and acyanotic groups were compared, no significant differences were found. These findings demonstrate that intelligence differences between cyanotic and acyanotic children persist when the effect of neurologic abnormalities and definitive surgery is removed and remain despite the severity of sickness or childs age at testing.

Time Course of Myocardial Amiodarone Uptake in the Piglet Heart Using a Chronic Animal Model

Abstract. This investigation sought to study single dose pharmacokinetics of amiodarone in a chronic animal model. We developed a new chronic animal model that allows serial direct access to the heart of the immature piglet via an implanted acrylic thoracic window. Following instrumentation and 72-hour recovery, amiodarone (5 mg/kg) was administered as a single intravenous bolus in immature piglets. Timed paired serum samples and myocardial biopsies for amiodarone level were obtained prior to, and up to 72 hours following, amiodarone administration. Peak concentrations of amiodarone in both serum (3.60 ± 1.02 μg/ml) and tissue (84.2 ± 6.50 ng/mg) occurred within 5 minutes of drug administration. As reported by others, this study demonstrated that the volume of distribution (VD) of amiodarone was large (33.31 ± 35.21 L/kg), and the clearance (Cl) was low (13.6 ± 4.4 ml/min/kg). Marked prolongation of both the serum t1/2 (29.98 ± 29.26 hours) and the myocardial t1/2 (29.20 ± 29.49 hours) were noted as well. The early, rapid myocardial peak of amiodarone in the immature myocardium corresponds with recent clinical observations of onset of antiarrhythmic efficacy 5 to 10 minutes following intravenous amiodarone administration in young children.

Acute continuous argon-laser induced tissue effects in the isolated canine heart

Fresh isolated myocardial, elastic-arterial, and valvular tissues from seven canine hearts were irradiated by argon laser. Irradiation was transmitted through 300 and 400 micron flexible quartz fiberoptic elements. Minimal power densities for vaporization of the myocardial, arterial, and valvular tissues were 80, 90, and 110 W/cm2, respectively, with maximal vaporization distances (fiberoptic tip to tissue) of 4 mm, 1 mm, and 1 mm, respectively. Irradiation of the valves at power densities approaching perforation caused contraction of the tissue. When tissue vaporization occurred, histologic examination of irradiated tissues showed a central crater surrounded by sequential layers of char, vaporization, and coagulation necrosis. These findings were common to all cardiac tissues. Additional findings unique to myocardium were a normal-appearing myocardial layer (skip-area), circumferential halo, and tissue clefts. Elastic arteries showed concentration of necrosis around the collagen and elastic fibers. Valvular damage was the most extensive and also included contraction of adjacent valvular tissue and endocardial sloughing.

Laser Atrial Septostomy: An Engineering Problem

The purpose of this study was to develop a reproducible method for atrial septostomy in live animals, which would be independent of both atrial septal thickness and left atrial size. Seven mongrel dogs monitored electrocardiographically were anesthetized and instrumented with systemic and pulmonary arterial lines. A modified Mullins transseptal sheath was advanced under fluoroscopic control to interrogate the left atrium and atrial septum. A 400 micron regular quartz or a laser heated metallic tip fiber was passed through the sheath up to the atrial septum. Lasing of the atrial septum was done with an Argon laser at power output of 5 watts. In three dogs, an atrial septosomy catheter was passed to the left atrium through the laser atrial septostomy and balloon atrial septostomy was performed. The laser atrial septostomy measured 3 x 5 mm in diameter. This interatrial communication could be enlarged with a balloon septostomy to over one cm in diameter. Hemodynamic and electrocardiographic monitoring were stable during the procedure. Engineering problems included: 1) radioluscency of the laser fibers thus preventing fluoroscopic localization of the fiber course; and 2) the inability to increase lateral vaporization of the atrial septum. It is concluded that further changes in the lasing fibers need to be made before the method can be considered for clinical use.

Myocardial Dose Response To Argon Laser Irradiation In Saline And Blood With Ultramicroscopical Analysis Of Myocardial Debris

Fresh myocardial segments from fetal and adult sheep, and from newborn and adult pigs were exposed to continuous mode argon laser irradiation in saline medium. Additionally, myocardial segments from newborn pigs were exposed to laser irradiation in fresh, heparin-ized blood medium. The irradiation distance from the tip of the quartz fiber to the tissue varied between contact and 20 mm, and power output at the fiber tip varied between 1 and 8 watts. Exposure time was kept constant at 2 seconds. Tissue debris was also processed for study by scanning and transmission electron microscopy. There was no difference in myocardial tissue response between sheep and pigs, nor was there a difference in response between young and adult animals. In both saline and blood media, there was a sharp decrease in burn depth with increasing irradiation distance. With increasing irradiation distances in saline medium, burn diameter increased initially and then plateaued; while with increasing irradiation distance in blood medium, the burn diameter decreased sharply. When the fiber tip was in contact with the tissue, the diameter of burn was greater in blood than saline, while the depth of burn was similar. Filtration of the tissue bath demonstrated particles as large as 3 mm in length which were composed of deformed and coagulated whole tissue segments. Electron and scanning micrography of the bath media identified intracellular components and fragments of burst cells. In conclusion, we have found no difference in adult vs. newborn, or sheep vs. porcine myocardial response to fiberoptic argon laser irradiation. The most critical factors affecting width and depth of burn were the distance of the fiber tip from the tissue, and the medium in which the tissue was bathed. Of particular clinical importance was the fact that the burn width and depth drastically decreased when blood was present between the laser fiber and the tissue.