Transcatheter occlusion of large pulmonary arteriovenous fistula.

We describe the compound transcatheter occlusion of a large and symptomatic pulmonary arteriovenous malformation in a 58-yr-old man. Pre- and postintervention clinical and laboratory data support the impression of an excellent outcome.

Significant pulmonary valve incompetence following oversize balloon pulmonary valveplasty in small infants: A long-term follow-up study.

Oversized dilatation balloons are recommended for relief of valvar pulmonic stenosis in infants and children during cardiac catheterization. Little information exists about the long-term outcome of this practice. Six of 107 consecutive patients undergoing balloon pulmonary valveplasty developed increasing pulmonary valve incompetence during follow-up periods of 0.5-10 years (mean, 7.2 years). Secondary right ventricular dilatation prompted insertion of a bioprosthetic pulmonary valve in one patient 6.8 years after intervention; valve replacement is pending in two additional patients, 4.3 and 10 years after intervention, respectively; and the three remaining subjects are thought likely to require valve replacement during childhood. The six reported subjects differ from the pulmonary valveplasty group as a whole in that they are younger (median age, 3 days vs. 11 months), had a higher degree of obstruction (right/left ventricular systolic pressure ratio prior to valveplasty 1.28 vs. 0.92), and underwent dilatation with relatively oversized balloons (balloon diameter to pulmonary valve annulus ratio 1.44 vs. 1.08). The balloon diameter to valve annulus ratio did not exceed 1.5 in any subject. Caution is advised in the use of oversized dilatation balloons in neonates or young infants with severe or critical pulmonic stenosis. Long-term consequences of substantial pulmonary valve incompetence outweigh, in our opinion, the limited gradient relief achieved with smaller balloons, sometimes requiring a second dilatation of the valve at an older age and larger size. Cathet. Cardiovasc. Intervent. 48:61-65, 1999.

Vessel-sparing technique for coil occlusion of the very small patent ductus arteriosus.

A technique is described for coil occlusion of the small patent ductus arteriosus through a 4 French arterial catheter. The need for a 5 French sheath and catheter to stabilize the 3 French size delivery catheter system is obviated. The method is proposed as a way to minimize arterial vascular injury in the small patient undergoing transcatheter occlusion of the small ductus.

Ventricular arrhythmias in children with an apparently normal heart.

Ventricular ectopy occurs frequently in normal children. In the presence of a normal heart, these arrhythmias, including asymptomatic, nonsustained ventricular tachycardia, carry a benign prognosis and are not associated with sudden, unexpected death. However, complex ventricular arrhythmias frequently indicate the presence of underlying cardiac disease; patients with such arrhythmias must undergo an appropriately thorough evaluation before decisions regarding prognosis and the need for therapy can be made.

Great vein and right atrial thrombosis in critically ill infants and children with central venous lines.

We performed a retrospective review of echocardiographic data files of infants and children hospitalized in the Newborn and Pediatric Intensive Care Units. Echocardiograms were examined to detect the presence and evolution of great vein and right atrial thrombosis in patients with central venous lines. Thirty-seven patients were identified over a five-year period. Echocardiograms were performed, not routinely, but in response to specific indications including catheter malfunction, thrombocytopenia, persistent chylothorax, bacterial or fungal sepsis, and superior vena cava syndrome. Fifteen of 37 patients died, 13 of them during the hospitalization in which the thrombus was discovered. Thrombolytic agents and surgery were used to treat selected patients, with mixed results. Two of the 22 survivors have significant disability related to the thrombus or complications arising from it. We conclude that great vein and/or right atrial thrombosis is a common complication of central venous catheterization in small infants and children; moreover, the morbidity and mortality relating to this complication is substantial.

Rate-adaptive cardiac pacing in children using a minute ventilation biosensor.

Chronotropic integrity is required for a normal cardiac output response to exercise. We evaluated a rate-adaptive ventricular demand pacemaker (Telectronics, META-MV) which uses minute ventilation as the sensed physiological variable for adjusting pacing rate, in seven young patients with a mean age of 11.4 years. All patients had clinically significant bradycardia related to complete heart block (n = 4) or sinus node dysfunction (n = 3). For the entire group, paced heart rates increased from 70 +/- 10 beats/min to 151 +/- 19 beats/min with exercise testing. The onset of rate adaptation took less than 30 seconds. Changes in paced rate were linearly related to workload, VO2 (5.9 to 20.7 mL/min/kg) and minute ventilation (8-65 L/min). The decline in pacing rate after exercise was related directly to the gradual decrease in minute ventilation and VO2. Our data show that minute ventilation closely and accurately reflects the metabolic demands of varying workloads in children and can be used to achieve physiological, rate-adaptive pacing.

Cellular electrophysiologic responses of isolated neonatal and adult cardiac fibers to d-sotalol.

The short-term cellular electrophysiologic actions of d-sotalol on isolated neonatal and adult canine ventricular myocardium and Purkinje fibers were evaluated using standard microelectrode techniques. d-Sotalol, 10(-6) to 10(-4)M, had no effects on action potential amplitude, maximal diastolic potential or action potential upstroke velocity (Vmax) in any neonatal or adult preparation. In five adult myocardial preparations, d-sotalol produced concentration-dependent increases in action potential duration at 50% (APD50) and 90% (APD90) repolarization and effective refractory period. In six neonatal myocardial preparations, d-sotalol produced a biphasic response; APD50, APD90 and effective refractory period decreased at 10(-6) and 10(-5)M. At 10(-4)M, these values increased significantly but to a lesser extent compared with values in adults. In seven adult Purkinje fibers, d-Sotalol significantly increased APD50, APD90 and effective refractory period in a concentration-dependent manner. All six neonatal Purkinje fibers responded in a biphasic manner, with values for APD50, APD90 and effective refractory period being less than control at 10(-6)M and near control values at 10(-5)M. At 10(-4)M, these variables were significantly increased, but to a lesser extent than in adult preparations. Our data confirm the typical class III effects of d-sotalol in adult cardiac tissues. The shortening of repolarization and refractoriness at lower drug concentrations in developing cardiac tissues may relate to age-dependent differences in cellular ionic function and basic electrophysiology.

Medical management of three asymptomatic infants with severe valvar aortic stenosis.

We report on the clinical course and serial hemodynamic studies of three patients with severe valvar aortic stenosis diagnosed in the neonatal period. None of the children were symptomatic in the first year of life. In each case, a conservative initial management approach was adopted. Between the time of initial study (mean age, 1.8 months) and the follow-up at 12-27 months of age (mean, 14.3 months), mean left ventricular systolic pressure decreased from 151 to 125 mmHg, the mean peak systolic pressure gradient across the aortic valve decreased from 61 to 33 mmHg, and the mean calculated aortic valve area index increased from 0.24 to 0.60 cm2/m2. One patient was operated on for symptoms that appeared at 14 months of age. The patient followed longest is now 5 years old, is growing well, has a normal electrocardiogram and an echo-predicted left ventricular systolic pressure of 128 mmHg. This experience suggests that not all asymptomatic neonates with severe valvar aortic stenosis require surgical intervention early in life. In some, the aortic valve orifice may increase in size with somatic growth and obviate the need for surgery in infancy or early childhood.

Amiodarone efficacy in a young population: relationship to serum amiodarone and desethylamiodarone levels.

Serum amiodarone and desethylamiodarone levels were measured in children and young adults receiving chronic amiodarone therapy. The study population consisted of 34 children and young adults with ventricular tachycardia (36%), atrial flutter (36%), and recurrent supraventricular tachycardia (27%). The mean age was 12.9 +/- 8.6 years (range 4 months to 23 years) and the mean daily dose of amiodarone was 6.6 +/- 3.7 mg/kg/day (range 2.5 to 25 mg). Serum amiodarone and desethylamiodarone levels after 10.1 months (range 1 to 40 months) were 0.85 +/- 0.63 microgram/ml and 0.67 +/- 0.42 microgram/ml, respectively. In three patients for whom amiodarone therapy was unsuccessful, serum amiodarone levels were 0.27, 0.85, and 1.18 micrograms/ml. There was no significant correlation between serum amiodarone or desethylamiodarone levels and dosage of amiodarone. Four patients, all 13 years or older, developed toxicity (skin rash [one patient], keratopathy [two patients], and hyperthyroidism [one patient]). There was no correlation between serum amiodarone and desethylamiodarone levels and toxicity; although there was a trend toward elevated reverse serum triiodothyronine levels in patients who developed toxicity, the values fell within the range of those patients without toxic side effects. Serum amiodarone levels do not appear to be of great value in predicting efficacy and toxicity of amiodarone in children and young adults receiving chronic drug therapy.

Hemodynamic consequences of neonatal polycythemia.

The hemodynamic consequences of neonatal polycythemic hyperviscosity and the effects of partial exchange transfusion were evaluated in 13 infants. Mean (+/- SD) venous hematocrit was 72% +/- 2.5%. After partial exchange transfusion, whole blood viscosity at a shear rate of 11.5 sec-1 decreased from 16.2 to 8.4 centipoise. There were significant (P less than 0.05) increases in heart rate (127 +/- 7.5 to 139 +/- 7.8 beats/min), Doppler-derived cardiac index (200 +/- 35 to 263 +/- 48 ml/kg/min), left ventricular stroke volume index (1.56 +/- 0.23 to 1.89 +/- 0.33 ml/kg), systemic oxygen transport (51.4 +/- 8.4 to 57.9 +/- 11.9 ml/kg/min), and laser-Doppler peripheral (cutaneous) blood flow (+80%) after partial exchange transfusion. The increase in cardiac index probably resulted from reductions in pulmonary and systemic vascular resistance index, the latter decreasing from 0.26 to 0.19 mm Hg/ml/min/kg-1. The greater increase in cutaneous blood flow (+80%) versus cardiac index (+32%) after exchange transfusion suggests hemodynamic compromise and a redistribution of blood flow away from organs that use little oxygen during polycythemia. Our data provide a possible basis for the symptoms of neonatal polycythemia, and demonstrate the acute hemodynamic benefits of partial exchange transfusion.

Systemic oxygen transport in patients with congenital heart disease.

The physiology of oxygen delivery was studied in 118 stable patients from 3 months to 20 years old with congenital heart disease. During cardiac catheterization, oxygen consumption (VO2), arterial and venous blood gases and oxygen saturations (range 41% to 98%), hemoglobin concentration, diphosphoglycerate (2,3-DPG), and P50 levels were measured, and then cardiac output, systemic oxygen transport (SOT), arterial and venous oxygen contents, and the VO2/SOT ratio (fractional O2 extraction) were calculated. P50 averaged 31 mm Hg, compared with 27 mm Hg in 10 control children (p less than .01). The composite O2-hemoglobin dissociation curve in vivo was broad: Po2 varied from 37 to 65 mm Hg at 80% saturation. P50, 2,3-DPG, hemoglobin concentrations, and O2 saturation varied widely and inconsistently with Po2 and arterial and venous O2 content, but resulted in clustering of the arterial oxygen content near 165 +/- 23 (SD) ml/liter over a wide range of Po2 and hemoglobin concentrations. SOT varied in direct relation with flow (r = .82, p less than .001), but not with oxygen content, Po2, or P50. VO2 varied widely at normal or high levels of SOT, but decreased linearly at SOT levels below 400 ml/min/m2. Oxygen extraction varied inversely with venous O2 content, rising to about 50% and plateauing below venous contents of 100 ml/liter. O2 extraction did not correlate with Po2, arterial O2 content, or P50. These data suggest that: O2 saturation cannot be predicted or calculated accurately from measured Po2, but must be measured directly, 2,3-DPG, hemoglobin concentration, and P50 fluctuate to stabilize arterial oxygen content, SOT is determined primarily by cardiac output in subjects who are adapted chronically, O2 extraction rises, due to a fall in venous O2 content, to maintain VO2 as transport falls, below a critical level of SOT, O2 extraction ceases to rise and VO2 falls with further reduction in transport.

Effects of flecainide on the cellular electrophysiology of neonatal and adult cardiac fibers.

The acute cellular electrophysiologic actions of flecainide acetate on isolated neonatal and adult canine ventricular myocardium and Purkinje fibers were evaluated with standard microelectrode techniques. Flecainide, 0.1 to 10.0 micrograms/ml, produced concentration-dependent decreases in action potential amplitude, overshoot, and phase O Vmax of adult ventricular myocardium and Purkinje fibers. The greatest effects were on Vmax. Neonatal action potential characteristics were affected to a lesser degree by flecainide. Flecainide had disparate effects on myocardial and Purkinje fiber repolarization and refractoriness. In adult ventricular myocardium, action potential duration (APD) and effective refractory period (ERP) increased progressively with drug concentration. APD and ERP were increased to a lesser degree in neonatal myocardium. In adult Purkinje fibers, APD decreased progressively with increasing flecainide concentrations. ERP decreased at 0.1 and 1.0 microgram/ml, but returned to control values at 10.0 micrograms/ml. APD and ERP of neonatal Purkinje fibers responded to a lesser degree. At faster stimulation frequencies (2 to 4 Hz), flecainide produced significant frequency-dependent decreases in Vmax in adult Purkinje fibers. Such use-dependency was not evident in neonatal fibers. These data indicate a significantly lower sensitivity of immature cardiac tissues to the electrophysiologic effects of flecainide.

Long-term follow-up of bronchopulmonary dysplasia.

We observed 10 children with bronchopulmonary dysplasia, evaluated initially by cardiac catheterization (mean age 18 months), for an average of 4.4 years. Age at last evaluation averaged 5.8 years; subjects reside in and around Albuquerque, N.M. (altitude 5000 ft). At initial cardiac catheterization, mean pulmonary artery pressure was 40 mm Hg, pulmonary vascular resistance index 8.9 units, and intrapulmonary shunt fraction was high; pulmonary wedge angiograms were normal. Over the period of follow-up the group has done poorly. Four of the 10 continue to receive home oxygen therapy, but none requires inotropic or diuretic therapy; four children have marked developmental or motor delays. Nine of 10 patients have abnormalities of respiratory function on spirometric testing. Four patients underwent recatheterization because of clinical indications; two had large atrial level left-to-right shunts not found on initial study. Reductions in pulmonary artery pressure (55 to 37 mm Hg) and pulmonary vascular resistance (11.9 to 7.8 units) occurred between the two studies in these four patients (average study interval 4.0 years); the still elevated levels of pressure and resistance fell further in response to 40% O2 administration. Pulmonary wedge angiograms were abnormal in each restudied patient. Although not uniformly bleak, the long-term outlook for children with severe bronchopulmonary dysplasia is diverse and guarded.

Communicating hydrocephalus: a reversible complication of the Mustard operation with serial hemodynamics and long-term follow-up.

Severe superior vena caval (SVC) obstruction following the Mustard operation resulted in substantially increased intracranial pressure in 3 patients. A pathophysiological mechanism is postulated to explain the cerebral edema in 1 and the communicating hydrocephalus in 2. Following surgical relief of the obstruction in the latter 2, there was a decrease in both the rate of head growth and the ventricular size. It is of note that despite the angiographic appearance of azygous decompression, the pressure elevation from the SVC obstruction was transmitted to the brain. The long-term follow-up at three and four years of the 2 infants with communicating hydrocephalus suggests that aggressive treatment is compatible with a favorable outcome.

Electrophysiologic effects of the levo- and dextrorotatory isomers of sotalol in isolated cardiac muscle and their in vivo pharmacokinetics.

Dl-sotalol is a specific beta-adrenergic blocking agent that markedly lengthens cardiac action potential duration. To determine whether d-sotalol, with little or no beta-blocking effect, also lengthens repolarization, standard microelectrode studies were used to determine the electrophysiologic properties of dl-sotalol and its stereoisomers in isolated rabbit and canine myocardial fibers. D- and l-sotalol produced concentration-dependent increases in action potential duration to 50% (APD50) and 90% (APD90) repolarization, respectively, and in the effective refractory period without changes in the maximal rate of rise of action potential. In rabbit sinoatrial node, d- and l-sotalol produced concentration-dependent increases in spontaneous sinus cycle length (29 and 35%, respectively) by lengthening the action potential duration (by 58 and 55%) without effect on phase 4 depolarization. At the highest concentration (27.2 micrograms/ml), d- and l-sotalol prolonged APD90 (by 38 and 54%, respectively, in Purkinje fibers and by 32 and 34% in ventricular muscle) and effective refractory period (by 49 and 49% in Purkinje fibers and 29 and 40% in ventricular muscle). The effects of the two isomers were not significantly different. At the middle concentration (2.7 micrograms/ml), d-sotalol, unlike l-sotalol, had no beta-adrenergic blocking effect, but the electrophysiologic effects of dl-, d- and l-sotalol were indistinguishable. The data indicate that d-sotalol is equipotent with l-sotalol in lengthening the action potential duration and effective refractory period in cardiac muscle, an action unrelated to adrenergic antagonism or pharmacokinetic differences between the stereoisomers.