Ira W. DuBrow

The conduction system in Pompe's disease

SummaryWe report our findings in the microscopic examination of the conduction system in four infants with glycogen storage disease, one of whom had adequate electrophysiologic studies. The electrophysiologic studies in the latter case showed P-A and A-H intervals at the lower limits of normal, but the H-V interval was just above the normal mean. This suggests that the rapid conduction was not localized in the anatomic counterpart of the H-V interval. The short P-R interval in the ECG may be related to the enlargement of cells, which may in turn be related to increased glycogen content. The relationship of glycogen per se to the speed of conduction is unknown.We found that the summit of the ventricular septum bulged, probably because of the generally increased cell size, and that the topography of the atrioventricular conducting system was different from normal. This is possibly related both to an increase in the cell sizes of the specialized conducting tissue itself and to deforming effects of this bulging summit of the ventricular septum. New microscopic details of the components of the conducting system are described in these cases.

The Influence of Age on Cardiac Refractory Periods in Man

Extract: As age is a determinant of cardiac refractory periods, this communication describes changes of refractory periods in an age continuum of infants, children and adults, 7 months through 77 years. Seventy patients with evidence of normal A-V conduction on scalar electrocardiogram were included. The patients were divided into six age groups: <2 years, 3–5 years, 6–10 years, 11–15 years, 16–30 years, and >30 years. Extrastimulus technique was used to determine refractory periods in sinus rhythm or at longest cycle length assuring atrial capture, then at shorter cycle lengths. Cycle lengths (CL) for each age group were divided into ranges: CLl, 1,000-600 msec; CL2, 599 460 msec; CL3, <459 msec. Refractory periods at the three CLs within each age group were determined. Full recovery times of the A-V node within groups of children were determined. Statistical significance of the data was found by analysis of variance. The younger group tended to have shorter values than the older groups (F < 0.05–0.001).Speculation: These changes with age apparently reflect maturation of the conduction system and may explain the differences in susceptibility to and electrophysiologic manifestations of various arrhythmias in infants, children, and adults.

Pathologic measurements in aortic atresia

Detailed autopsy measurements were performed in 13 infants with hypoplastic left ventricle and aortic atresia. Emphasis was placed on the evaluation of changes in the right ventricle, since its function may be important in determining surgical survival. Other important aspects were the ascending aortic and transverse aortic arch diameter, the presence of left atrial obstruction, and the size of the left atrium. The development of improved 2DE and Doppler imaging will permit preoperative and sequential evaluation of these parameters. Measurements performed in this study may serve as a basis for selection of infants for palliative surgery; these procedures are being undertaken more frequently in this hitherto fatal lesion. The measurements may also serve as a basis for noninvasive serial studies of these infants postoperatively.

Etiology of atrioventricular-conduction abnormalities following cardiac surgery☆

Atrioventricular-nodal-conduction abnormalities following cardiac surgery have been attributed to the potassium ion in cardioplegic solutions. To clarify the etiology of these rhythm problems, 15 dogs were subjected to (I) 60 min 4 degrees C potassium cardioplegic arrest; (II) 30 min normothermic ischemic arrest; or (III) cardiac hypothermia without ischemia. In sinus rhythm and during atrial pacing, A-H and H-V intervals, Wenckebach cycle length (WCL), atrial- and AV-nodal refractory periods (ARP and NRP) were measured at 37 degrees C before and 30 min after arrest (groups I and II) and at various myocardial temperatures (group III). Following cardioplegic arrest and reperfusion, all AV-nodal-conduction properties were unchanged from preischemic values. In contrast, unprotected ischemia significantly prolonged AV-nodal-conduction time (P less than 0.01) and myocardial hypothermia resulted in prolonged WCL (P less than 0.01), prolonged functional NRP (P less than 0.05), in addition to delayed A-H interval (P less than 0.05). The data suggest that properties of AV-nodal conduction are preserved following potassium cardioplegic arrest, but impaired by ischemic injury or persistent local cardiac hypothermia.

Parietal and Septal Atrioplasty for Total Correction of Anomalous Pulmonary Venous Connection with Superior Vena Cava

Abstract An operative procedure is described for correction of anomalous drainage of the right pulmonary veins into the superior vena cava. The procedure is technically simple and has the advantage of providing ample drainage of the pulmonary veins and superior vena cava without resorting to the use of prosthetic materials. Four case reports are presented.

Pulmonary Artery Banding in Infants: A Physiological Intraoperative Method of Determining the Effectiveness of the Procedure

Abstract A physiological method has been devised to evaluate the degree of intraoperative pulmonary artery constriction during operations for the palliation of infants with severe congestive heart failure. This approach depends on precisely determining the degree of shunting between the right and left sides of the heart by serial determinations of arterial oxygen saturation. Two patients are cited who illustrate the advantages of this technique.

Quantitative angiographic and morphologic aspects of aortic valve atresia

Quantitative angiographic measurements were performed in 15 infants aged 1 to 35 days who had aortic valve atresia with intact ventricular septum and hypoplastic left ventricle. Thirteen infants had similar measurements performed at autopsy. The latter measurements were smaller than those found at angiography (because of shrinkage), but their relationship was predictable. Angiographic right ventricular (RV) volumes were 2 and 4 times normal in diastole and systole, respectively. The RV volume measured at autopsy was greater than 3 times normal. Mean RV ejection fraction was 0.40; it was below normal in 10 infants. Maximal right atrial volume was greater than 2 times normal, and mean left atrial maximal volume was two-thirds normal. The relation between circumferences of the aortic arch and ascending and descending aorta was similar at angiography and autopsy.

Effect of palliative and corrective surgery on ventricular volumes in complete atrioventricular canal

SummaryThe effect of pulmonary artery banding (PAB) and intracardiac repair on ventricular volumes was studied in 35 patients with uncomplicated complete atrioventricular canal (CAVC). Right ventricular (RV) and left ventricular (LV) end-diastolic volumes (EDV), determined from biplane cineaniograms using Simpsons rule, were expressed as a percent of normal mean (% NI) for body surface area; normal range (mean ± 1SD) is equivalent to 75%–125% NI. In preoperative studies (RV 26, LV 33), EDV averaged 149±51% and 184±50% NI, respectively,P vs NI<0.001 for both. In one of 26 patients, RV was very small (45% NI), and one of 33 had a small LV (70% NI). In 13 patients studied post-PAB, RVEDV and LVEDV were lower than in the preoperative group (P<0.001) and averaged 114±40% and 126±52% NI, respectively. In three of 13, RV was small (67% and 71% NI) or very small (56% NI). Three others had a small (71% and 67% NI) or very small (56% NI) LV.In serial pre- and post-PAB studies (RV 9, LV 11), EDV was increased or normal in all preoperatively. In seven of nine, RVEDV decreased, falling below normal range in three. In eight of 11, LVEDV decreased, falling below normal in three. Following repair, RV and LVEDV averaged 80±20% NI and 126±23% NI, respectively, in seven patients. Four of the seven had RVEDV below normal range. Two patients with a small ventricle had intracardiac repair and did well. A previous report of small RV in patients with CAVC and PAB was corroborated and a similar incidence of small LV was found.Serial pre- and post-PAB studies suggested a direct relationship between PAB and ventricular underdevelopment. The number of patients with small ventricles undergoing repair was too small to establish that their surgical risk is higher. Longer follow-up is necessary to tell whether small RV after repair will result in significant impairment of cardiac function.

The Incidence of Percutaneous Central Venous Catheter (PCVC) Thrombosis in High Risk Neonates, and the Relationship of Thrombosis to the Occurrence and Persistence of Bacteremia 1420

Percutaneously inserted central venous catheters (PCVCs) are commonly used in high risk neonates, but may be complicated by the formation of thrombi in the central veins or right atrium, and/or the occurrence of foreign-body induced bacterial blood stream infection. The purpose of this study is to determine the incidence of PCVC-related, central vein and/or right atrial thrombosis in neonates. In addition, the study will assess the relationship of thrombus formation to the subsequent development of bacterial blood stream infection, and determine if the presence of a thrombus is associated with failure of antibiotic treatment to eradicate bacteremia. To date, 47 neonates(mean birth weight 1139.4 grams, mean gestational age 28.1 weeks) have been enrolled in the study. In all subjects, immediately post insertion, a blood culture was drawn from the PCVC. Within 72 hours of insertion, a baseline 2-D echocardiogram with color flow Doppler study was performed. Thereafter, while the catheter was in place, blood cultures were drawn and a follow-up 2-D echocardiogram/color flow Doppler study was done once weekly. If a positive blood culture was detected, two additional, quantitative blood cultures (one from the PCVC; one from a peripheral vein) were obtained prior to initiating antibiotic therapy, and a 2-D echocardiogram/color flow Doppler study was performed within 24 hours. Following initiation of antibiotic therapy, a single, daily blood culture was obtained from the PCVC or peripheral vein depending on access, until three consecutive, daily blood cultures showed no bacterial growth. The median duration of PCVC lines was 37 days. Four neonates(0.09%) had positive blood cultures, at a mean of 25.3 days post-insertion. Neonates had a median of 5 blood cultures performed. Only 1 neonate (0.02%) had evidence of thrombus formation on echocardiogram at 10 days post-insertion. Neonates are continuing to be enrolled in this study. Based on this preliminary data, it appears that, despite the fact that in our unit PCVC lines are not changed, PCVC-related bacteremia and thrombosis are rare complications.