Pulmonary Arteriovenous Malformation Causing Systemic Hypoxemia in Early Infancy.

Pulmonary arteriovenous malformation (AVM) is not routinely appreciated during the standard echocardiogram to assess for structural abnormalities or pulmonary hypertension. The distal pulmonary AVM is suspected only if an injection of agitated saline is performed and late entry of particles is appreciated in the left heart structures. A large or complex pulmonary AVM can result in significant right-to-left shunting and consequential systemic hypoxemia in the presence or absence of pulmonary hypertension. For direct visualization of the pulmonary AVM, computerized tomography (CT) scan is the procedure of choice. Here, we present two young infants with systemic hypoxemia who underwent standard medical management including mechanical ventilation and one patient was placed on extracorporeal membrane oxygenation (ECMO) before the diagnosis of pulmonary AVM was established. Subsequently, both patients have done well into mid-term follow-up after being treated successfully using transcatheter occlusion techniques in the cardiac catheterization laboratory during early infancy. We aim to emphasize the importance of a high index of suspicion for pulmonary AVM in infants with refractory systemic hypoxemia of unclear etiology.

Right hemidiaphragmatic elevation with a right-to-left interatrial shunt through a patent foramen ovale: a case report and literature review.

A right-to-left shunt (RLS) is an uncommon complication of a patent foramen ovale (PFO) that may cause hypoxemia from venous admixture and ischemic complications from paradoxic embolization. This report presents the third described patient whose RLS through a PFO and profound hypoxemia developed in association with right hemidiaphragm dysfunction (but without a pressure gradient driving the right-to-left flow). In addition to extending the available experience with this unusual clinical event, we report on the successful closure of the PFO by a catheter-deployed double-umbrella device, after the positioning of which the patient's oxygenation normalized.

Impact of low body weight on frequency of pediatric cardiac catheterization complications.

The overall risk of pediatric cardiac catheterization remains low despite the enormous new complexity and potential for complications brought on by the growth of interventional catheterization techniques. For all patients aged < 21 years, balloon interventions carry the highest risk, diagnostic procedures carry more risk than non-balloon interventions, and although weight < or = 5 kg is a significant risk factor for complications, irrespective of the type of procedure performed, weight < or = 2.5 kg did not alter that risk.

Age related changes in dual AV nodal physiology.

Dual atrioventricular nodal (DAVN) physiology has been reported in up to 63% of pediatric patients with anatomically normal hearts, yet atrioventricular nodal reentrant tachycardia (AVNRT) accounts for only 13%-16% of supraventicular tachycardia (SVT) in childhood. The incidence of AVNRT increases with age and becomes the most common form of SVT by adolescence. We investigated the age related electrophysiological responses to programmed atrial and ventricular stimulation in 14 pediatric patients who underwent intracardiac electrophysiological study prior to radiofrequency catheter ablation for AVNRT and who exhibited DAVN physiology. Single atrial and ventricular extrastimuli were placed following drive trains with cycle lengths of 400-700 ms and 350-500 ms, respectively. Six children (mean age 8.2 years, range 5.2-11.5 years) were compared to eight adolescents (mean age 16.6 years, range 13.3-20.7 years). Adolescents were found to have a significantly longer fast pathway effective refractory period (ERP) (median 375 vs 270 ms, P = 0.03), slow pathway ERP (median 270 vs 218 ms, P = 0.04), atrio-Hisian (AH) during AVNRT (median 300 vs 225 ms, P = 0.007), and AVNRT cycle length (median 350 vs 290 ms, P = 0.03). There was a strong trend for the AH measured at the fast pathway ERP to be longer in adolescents than in children (median 258 vs 198 ms, P = 0.055). The AH at the fast pathway ERP was more strongly correlated with baseline cycle length than with age (r = 0.7, P = 0.01 vs r = 0.5, P = 0.7). There was no significant difference in the retrograde VA conduction between adolescents and children. These results demonstrate an age related difference in AV nodal response to programmed atrial stimuli in pediatric patients with DAVN physiology and AVNRT. These differences are consistent with mechanisms that may explain the increased incidence of AVNRT in adolescents compared to children.

Cardiac arrest in infants after congenital heart surgery.

BACKGROUND: The survival rate to discharge after a cardiac arrest in a patient in the pediatric intensive care unit is reported to be as low as 7%. The survival rates and markers for survival strictly regarding infants with cardiac arrest after congenital heart surgery are unknown. METHODS AND RESULTS: Infants in our pediatric cardiac intensive care unit database were identified who had a postoperative cardiac arrest between January 1994 and June 1998. Parameters from the perioperative, prearrest, and resuscitation periods were analyzed for these patients. Comparisons were made between survivors and nonsurvivors. Of 575 infants who underwent congenital heart surgery, 34 (6%) sustained a documented cardiac arrest; of these, 14 (41%) survived to discharge. Perioperative parameters, ventricular physiology, and primary rhythm at the time of arrest did not influence outcome. Prearrest blood pressure was lower in nonsurvivors than in survivors (P<0.001). A high level of inotropic support prearrest was associated with death (P=0.06). Survivors had a shorter duration of resuscitation (P<0.001) and higher minimal arterial pH (P<0.02) and received a smaller total dose of medication during the resuscitation. Although survivors had an overall shorter duration of resuscitation, 5 of 22 patients (23%) survived to discharge despite resuscitation of >30 minutes. CONCLUSIONS: The outcome of cardiac arrest in infants after congenital heart surgery was better than that for pediatric intensive care unit populations as a whole. Univentricular physiology did not increase the risk of death after cardiac arrest. Infants with more hemodynamic compromise before the arrest as demonstrated with lower mean arterial blood pressure and higher inotropic support were less likely to survive. The use of predetermined resuscitation end points in this subpopulation may not be justified.

Locational decisions of physicians in rural North Carolina.

Recent literature suggests that there is a rural-urban imbalance of doctors in the United States. In order to investigate this maldistribution, a survey was conducted of 504 physicians in eastern North Carolina. The objective was to determine the factors which most influenced doctors' decisions to locate their practice. A conceptual framework was used to highlight the influence of the community, medical schools and the physician's personal preferences. A discriminant analysis of rural and urban physicians revealed the doctor's personal characteristics to be most important, followed by community and medical school factors. In particular, physicians raised in smaller communities showed a greater preference for practicing in rural areas. Tactics for recruiting rural doctors and other policy recommendations are suggested.

Adaptive filter with a time-domain implementation using correlation cancellation loops.

The results of a feasibility study of an optical adaptive filter are presented. The processor is a time-domain implementation using correlation cancellation loops. Included is a theoretical verification of the correlation cancellation loop approach for linear prediction. The processor architecture and performance are described in detail. The results are encouraging although limited by laboratory equipment.