Selective transepicardial ablation in the immature canine myocardium. A more precise method.

The numerous surgical and transcatheter ablation methods widely applicable to the adult heart have had limited use and efficacy in the immature myocardium. This study introduces a more precise modification of the transepicardial approach to ablation, applicable to the immature heart, by combining selective mapping and simultaneous ablation techniques. To determine the specificity of this method, we attempted His bundle and sinus node ablations in 14 beagle puppies (aged 2 to 4 months). After a thoracotomy, a custom bipolar needle mapping/ablation probe, attached to a standard electrophysiologic recorder, was applied along the aortoatrial and atrial-superior vena caval junctions to record maximal epicardial His bundle and sinus node impulses, respectively. Complete ablation was achieved by the single injection of 10% formalin specifically into the desired target region of the conduction system after the probe was advanced into the myocardium proper. Ventricular pacing was then instituted, the thoracotomy closed, and the animals allowed to recover. After 4 months' observation, bidirectional complete atrioventricular block persisted. High right atrial electrical activity was absent in the animals that underwent sinus node ablation. Programmed stimulation failed to induce any arrhythmias. Histologic study demonstrated selective His bundle and sinus node destruction with minimal involvement of surrounding tissue. This study demonstrates a reproducible transepicardial approach to precise ablation in the immature heart.

A new low threshold platinized epicardial pacing electrode: comparative evaluation in immature canines.

A prospective comparison of pacing and sensing capabilities between the conventional Medtronic Model 4951 platinum-iridium epicardial pacing electrode and a new modified "platinized" version of the same electrode was performed in immature canines to determine if the new electrode design improves pacing in the immature myocardium. The conventional electrode was modified by electroplating platinum black particles onto the surface to increase the effective or true microscopic surface area, yet essentially maintain the same overall geometric electrode size. Both epicardial electrodes were inserted into the right ventricular myocardium with the lead pad sutured to the epicardium, and externalized to the scruff in five puppies (age 3 months). An additional left ventricular lead was implanted to permit chronic pacing following epicardially-induced atrioventricular block. Acute and chronic sensing and pacing capabilities of each externalized electrode were performed at implant and weekly up to 4 months. Histologic examination of each electrode implant site was performed at the end of the study period. At implant, both electrodes exhibited comparable values for sensed R waves, lead impedances, and pacing thresholds. During the study, the platinized electrode exhibited lower pacing thresholds. Analysis of all postimplant data demonstrated this threshold difference to be significantly lower (P less than .01) for the platinized version. Lead impedance and sensing capabilities remained comparable between the two designs. Histologic study demonstrated less fibrotic infiltration at the platinized electrode site. This preliminary evaluation indicates that for the duration of the postimplant study period, the platinized epicardial electrode design was associated with significantly lower thresholds and less fibrosis as a function of time compared to the conventional smooth electrode surface design. The new platinized electrode limits exit block in the developing immature myocardium and permits safe pacing at lower pulse widths and voltages to increase battery life.

Three conditions in neonatal asphyxiating thoracic dysplasia (Jeune) and short rib-polydactyly syndrome spectrum: a clinicopathologic study.

Clinicopathologic examination of eight patients with asphyxiating thoracic dysplasia (Jeune; ATD) disclosed two different types, which were designated as type 1 and type 2. Type 1 ATD was characterized by the presence of radiologically irregular metaphyseal ends and histopathologically irregular cartilage bone junction with patchy distribution of physeal zone of hypertrophy. Type 2 ATD showed radiologically smooth metaphyseal ends and histopathologically diffusely retarded and disorganized physes with smooth cartilage bone junctions. Examination of four patients with the "Verma-Naumoff" short rib-polydactyly syndrome showed many radiologic and pathologic features similar to those of type 1 ATD. Differential diagnosis of these three osteochondrodysplasias is discussed along with chondroectodermal dysplasia (Ellis-van Creveld), short rib-polydactyly syndrome type 1 (Saldino-Noonan), short rib-polydactyly syndrome type 2 (Majewski), and the new short rib syndrome reported by Beemer et al [1983].

Melanosis and hydrocephalus. Report of four cases.

Four cases are presented in which hydrocephalus and extensive pigmented lesions of the body coexisted. A related developmental defect is suggested.

Two lethal chondrodysplasias with giant chondrocytes.

Two infants, each with a different form of sporadic lethal chondrodysplasia, had multinucleated giant chondrocytes in resting cartilage. Both patients also had severe laryngeal stenosis and normal chromosomes. The radiographic abnormalities in one patient conformed to the recently delineated entity, atelosteogenesis (spondylohumerofemoral hypoplasia or giant cell chondrodysplasia); the other patient had an unclassified type of spondyloepiphyseal dysplasia. The findings in these two patients and the previously reported observations in spondylohumerofemoral dysplasia confirm that chondrocytic giant cells are a causally nonspecific phenomenon.

Disseminated neonatal echovirus 11 disease following antenatal maternal infection with a virus-positive cervix and virus-negative gastrointestinal tract.

An infant girl was born apparently well one week after her mother had had a mild illness with chills, fever, and diarrhea. On the third day of life, the infant became ill and died four days later with necrotizing hepatitis. On the same day, echovirus type 11 was recovered from the throat, rectum, and buffy coat of the infant and from the cervix of the mother. At this time, the mother had an IgM neutralizing antibody titer to echovirus type 11 and 1:128, but no IgG antibodies. The infant had no echovirus type 11 antibodies. The virus was also isolated from the baby's liver and adrenal at autopsy. These findings raise the possibility of enterovirus infection at delivery from a contaminated cervix.

Idiopathic neonatal iron storage involving the liver, pancreas, heart, and endocrine and exocrine glands.

Autopsy studies of two infants, one a newborn, the other 4 months old, revealed massive amounts of iron in lysosomes of hepatocytes and pancreatic acinar cells. Iron, which had been transported across the placenta, accumulated in the same cell types as in adults with primary and secondary hemochromatosis. Hemosiderin was found in cardiac muscle cells, gastric and intestinal glands, and endocrine and exocrine organs including pituitary, thyroid, adrenals, islets of Langerhans, and sublingual and sweat glands. The liver was the most affected organ and the normal hepatic architecture was replaced by hepatocytes which were arranged in cluster, pseudoacinar structures, and multinucleated giant cells embedded in a collagen matrix. The islets of Langerhans were hyperplastic and hypertrophic. Ten similar cases, in five families, have been described; no patients liver longer than 4 months. Neonatal iron storage disease is clinically and pathologically distinct from Zellweger's cerebrohepatorenal syndrome and hypermethioninemia (tyrosinemia) neonatal diseases in which large stores of iron are present in hepatocytes. No abnormalities in serum iron, ferritin, or transferrin concentrations were detected in five parents of the affected children.

Atypical clinical course of ornithine transcarbamylase deficiency due to a new mutant (comparison with Reye's disease).

A male infant with ornithine transcarbamylase (OTC) deficiency is described who was relatively symptom free for 4 months, gradually developed severe spasticity due to cerebral atrophy, and died at 13 months of age. Liver OTC activity was 1.5% of the normal mean. The mutant OTC showed an increased apparent Km for ornithine and an increased pH optimum. These kinetic findings fail to explain the atypical clinical course. The clinical picture of patients with genetic OTC deficiency who present during acute exacerbations together with the elevation of serum glutamic oxaloacetic transaminase and microvesicular fat accumulation in liver, as seen in this case, may suggest Reye's syndrome; however, electronmicroscopic examination of this patient suggested that the normal appearance of mitochondria helps to distinguish the two.