Thomas A. Riemenschneider

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.

Maturational Changes in Myocardial Contractile State of Newborn Lambs.

Summary: There have been no investigations of chronologic changes in postnatal contractile state of both left and right ventricles of the newborn. Thus, we determined isovolumetric indices of contractility in 32 acutely instrumented newborn lambs (1 day to 12 wk; three exteriorized near term fetuses, and four adult sheep. These studies demonstrated a narked increase in inotropic properties of both ventricles which was especially pronounced during the first 3 days of extrauterine life (group I. left ventricle Vmax 3.2 ± 0.27 and VCEIO 3.2 ± 0.28 ML (muscle lengths/sec; right ventricle Vmax 2.1 ± 0.2 and VCEIO 2.2 ± 0.13 ML/sec) and was associated with elevated cardiac output (428 ± 52 cc/kg/min), largely resulting from an elevated stroke volume (2.1 ± 0.31cc/kg). During subsequent postnatal maturation, contractility indices of both ventricles gradually declined to values intermediate between newborn and adult [(group IV. 22 to 84 days) - left ventricle Vmax 1.78 ± 0.13 and VCEIO, 1.79 ± 0.15 ML/sec; right ventricle Vmax 1.48 ± 0.07 and VCEIO 1.31 ± 0.3 ML/sec]; associated with a corresponding decling in cardiac output (group IV, 136 ± 38 cc/kg/min), related in large measure in a decline in stroke volume (0.76 ± 0.13 cc/kg). Simulation of birth in exteriorized fetuses was associated with a sudden increase in contractile indices for both left (Vmax 2.1 ± .2 → 3.0 ± .3 and VCEIO 2.1 ± 0.2 → 3.1 ± ML/sec) and right (Vmax 2.0 ± 0.2 → 2.5 ± 0.2 and VCEIO 1.9 ± 0.1 → 2.5 ± 0.2 ML/sec) ventricles. We conclude that there is a postnatal elevation of ventricular contractile state which contributes to successful postnatal adaptation of the newborn cardiovescular system.Speculation: The increased metabolic demands associated with adaptation to extrauterine life are met by an increased cardiac output in the newborn. The necessary cardiac output may be accomplished in part through an elevation of myocardial contractile state, induced by postnatal increases in circulating hormones.

Laser irradiation of congenital heart disease: Potential for palliation and correction of intracardiac and intravascular defects

We examined the potential for laser irradiation of congenital heart defects, with the use of postmortem hearts and an argon ion laser with a flexible quartz fiber. Atrial septectomy was performed in five newborn hearts. Obstructive lesions were relieved by laser irradiation in valvular pulmonic and aortic stenosis, dysplastic pulmonary valve, pulmonary atresia, and coarctation of the aorta. To demonstrate the efficacy of in vivo cardiac laser surgery, atrial septectomy was also performed in an anesthetized dog model, under echocardiographic visualization, without change in heart rate or blood pressure. Our results demonstrate the feasibility of intracardiac and intravascular laser irradiation for palliation and repair of selected congenital heart diseases.

Occult arrhythmias as the etiology of unexplained syncope in children with structurally normal hearts

We evaluated six children for syncope of unknown etiology between March, 1983, and March, 1984. All had undergone previous neurologic evaluation which was normal. Cardiac examination, chest roentgenograms, and two-dimensional echocardiograms were also normal in all of the patients. Abnormal noninvasive findings in five patients included Mobitz type II atrioventricular (AV) block (one patient), sinus bradycardia (three patients), and supraventricular tachycardia (one patient). Four patients had one or more abnormal findings at invasive electrophysiologic study including evidence of sinus node dysfunction (three patients), AV node dysfunction (three patients), and distal His-Purkinje system disease (two patients). All children had a normal right heart hemodynamic catheterization. We conclude that arrhythmias are an important cause of syncope in some children with an otherwise normal heart when neurologic causes have been excluded.

A 20-year review of ostium primum defect repair in children

Between July, 1963, and July, 1983, a total of 69 patients (35 boys and 34 girls) underwent ostium primum defect repair. There were four perioperative deaths and four patients were subsequently lost to follow-up, leaving 61 children followed for 6 months to 20 years (mean 5 years). Results of surgery were assessed by cardiac catheterization in 17 of 61 patients, while the remaining patients were evaluated noninvasively. Postoperative mitral insufficiency was found to be absent in 19 patients, mild to trivial in 35, moderate in four, and severe in two. Four patients were found to have large residual atrial septal defects. Significant late postoperative arrhythmias were found in 14 of 61 patients. The types of arrhythmias included isolated complete atrioventricular block in 5 of 14, complete atrioventricular block with sinus node dysfunction in 2 of 14, and isolated sinus node dysfunction in 7 of 14. Pacemakers have been implanted in 8 of 14 of these patients. Based on this 20-year review of a large number of children: (1) ostium primum defect repair is associated with a low mortality rate, (2) residual mitral insufficiency although common is usually mild to trivial and nonprogressive, and (3) significant arrhythmias are a frequent complication and often require pacemaker implantation.

Maturational changes in myocardial pump performance in newborn lambs

We examined the left ventricular stroke volume response to fluid loading in 24 acutely instrumented newborn lambs and the right ventricular response in 12 lambs. Newborn lambs (group 1, ages 2 to 4 days) demonstrated a limited response to acute volume loading for both left and right ventricles. With maturation, the left ventricle exhibited a progressively greater ability to respond to acute volume loading, with greater peak stroke volumes achieved at higher end-diastolic pressures. The response of the right ventricle remained limited at all ages examined, with peak stroke volume achieved at lower end-diastolic pressures. We conclude that postnatal maturation of the left ventricle results in a progressively greater stroke volume response in older lambs, while the response of the right ventricle remains limited.

Magnetic resonance imaging in patients with hypoplastic right heart syndrome

Abstract ECG-gated magnetic resonance imaging (MRI) has been shown to provide excellent tomographic images of congenital heart defects. 1–4 Cardiac structures are especially well demonstrated because of the sharp distinction between relatively white myocardial walls or valves and the dark appearance of rapidly flowing blood within the heart. In particular, the clarity with which the endocardial and epicardial surfaces are resolved using MRI is superior to that produced by other noninvasive imaging modalities such as computed tomography (CT) or ultrasound and rivals the clarity produced by high quality cineangiograms. Thus, ventricular size, geometry, and wall thicknesses can be precisely defined. In this study, we examined the ability of MRI to depict the abnormal cardiac morphology in patients with known hypoplastic right heart syndrome (tricuspid atresia or pulmonic atresia with intact ventricular septum).

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.

Maturational changes in cardiac muscle myosin adenosine triphosphatase activity relative to hemodynamic alterations in newborn lambs.

We performed a chronologic investigation of left (LV) and right (RV) ventricular myosin ATPase activity and hemodynamics in newborn lambs. We found an elevation in myosin ATPase activity for the LV, which was achieved by 6 to 8 weeks of age and which correlated directly with increasing ventricular stroke work. Myosin ATPase activity did not increase with age for the RV, a finding which was associated with a postnatal decrease in ventricular stroke work. These findings may represent an important postnatal adaptation of newborn myocardium to the demands of extrauterine life.