Congenital isolated pulmonary valve incompetence: neonatal presentation and early natural history.
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Cardiac Catheterization↗
Biomedical subjects
S M Yabek
Publications and source records attributed to S M Yabek.
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.
Adolescent↗
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.
Catheterization, Central Venous↗
Severe cardiac conduction abnormalities associated with atypical toxic shock syndrome.
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Adolescent↗
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.
Adult↗
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.
Aortic Valve↗
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.
Action Potentials↗
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.
Action Potentials↗
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.
Adolescent↗
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.
Blood Pressure↗
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.
2,3-Diphosphoglycerate↗
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.
Brain Edema↗
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.
Blood Pressure↗
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.
Action Potentials↗
Recreational and occupational recommendations for young patients with heart disease. A Statement for Physicians by the Committee on Congenital Cardiac Defects of the Council on Cardiovascular Disease in the Young, American Heart Association.
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Adolescent↗
Acute effects of amiodarone on the electrophysiologic properties of isolated neonatal and adult cardiac fibers.
The acute cellular electrophysiologic actions of amiodarone on isolated neonatal and adult canine ventricular muscle and Purkinje fibers were evaluated using standard microelectrode techniques. Amiodarone, 10(-6) to 5 X 10(-5) M (0.68 to 34 micrograms/ml), significantly (p less than 0.05) prolonged adult ventricular muscle action potential duration and voltage-dependent refractoriness at all concentrations, thereby demonstrating typical class III antiarrhythmic effects. Similar concentrations had no significant effects on neonatal ventricular muscle. Amiodarone significantly shortened action potential duration and refractoriness of both neonatal and adult Purkinje fibers, with neonatal fibers having a greater sensitivity to the drug. At the standard stimulation rate of 1 Hz, amiodarone had no effects on action potential amplitude or maximal rate of rise of phase 0 of the action potential (Vmax) of any tissues. At faster stimulation frequencies (2 to 4 Hz), amiodarone produced frequency-dependent decreases in action potential amplitude and Vmax of all neonatal and adult preparations. The data indicate that amiodarone exhibits a complex aggregate of electrophysiologic actions that include significant frequency-related class I effects. Compared with adult myocardium, neonatal tissues demonstrated altered responsiveness to amiodarone, a feature common to many antiarrhythmic compounds.
Action Potentials↗
Effects of hypoxia on the cellular electrical activity of adult and neonatal canine ventricular myocardium.
Standard microelectrode techniques were utilized to evaluate the effects of acute hypoxia on the cellular electrical activity of neonatal and adult ventricular myocardium. Control action potential parameters from adult and neonatal tissues were not significantly different. Thirty minutes of acute hypoxic superfusion significantly (p less than 0.05) reduced all adult action potential indices. In neonatal preparations, only action potential duration at 50% repolarization (-17%) and action potential duration at 90% repolarization (-12%) were reduced significantly. After 60 min of hypoxia, action potential amplitude, maximum diastolic potential, and phase 0 upstroke velocity from neonates were still not reduced significantly. The alteration in neonatal action potential parameters induced by 1 h of hypoxic superfusion (5.5 mM glucose) were all reversed by 16.5 mM glucose despite continued hypoxia. Exclusion of glucose from the hypoxic superfusate did not greatly affect the response of neonatal tissues to hypoxia. In adult action potentials, the degree of decrease for each action potential parameter was markedly greater compared to the hypoxic solution with normal (5.5 mM) glucose. Following hypoxic superfusion of neonatal preparations with 0 mM glucose, reoxygenation with 16.5 mM glucose resulted in action potential parameters with exceeded control values by 4 to 25%. Our data indicate a greater resistance of developing myocardium to the detrimental effects of hypoxia on cellular electrical activity. This seems to be related to a greater glycolytic activity of neonatal myocardium compared to adult hearts.
Action Potentials↗
Right ventricular contractile function in children with congenital heart disease.
Indexes of right ventricular (RV) systolic function were evaluated in 41 patients undergoing cardiac catheterization. High-fidelity tracings were used to determine RV pressure, maximal RV dP/dt and the velocity of contractile element shortening at a developed pressure of 10 mm Hg (VCE10). In 14 children with an RV systolic pressure less than 35 mm Hg, normal RV volume, pulmonary vascular resistance (PVR) less than 3 units X m2 and no shunts (our normal group), mean (+/- standard deviation) RV dP/dt was 437 +/- 116 mm Hg X s-1 and VCE10 was 1.15 +/- 0.33 muscle length X s-1. In patients with RV systolic hypertension due to valvular pulmonary stenosis or isolated increases in PVR, mean values for RV dP/dt and VCE10 were significantly (p less than 0.05) greater than the normal values. In patients with a ventricular septal defect, RV hypertension and normal PVR, VCE10 was normal but RV dP/dt was significantly elevated. Children with chronic RV volume overload had normal RV contractile indexes. No patient in any group had values for RV dP/dt or VCE10 that were less than normal (mean normal - 2 standard deviations). This study establishes for the first time the indexes of RV isovolumic systole in children. It also shows that RV contractile function is preserved in young patients with chronic RV pressure or volume overload who do not have overt congestive heart failure.
Adolescent↗