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C L Case

Publications and source records attributed to C L Case.

At least 37 records · Page 2Linked to original sources
PubMed1996

Developmental effects of d-sotalol on anterograde and retrograde atrioventricular conduction in the rabbit.

INTRODUCTION: These experiments investigate the developmental effects of d-sotalol on standard electrophysiologic parameters of anterograde and retrograde AV conduction in the rabbit. METHODS AND RESULTS: Using bipolar electrograms and standard pacing techniques, the effects of graded concentrations of d-sotalol on anterograde and retrograde conduction in mature and immature perfused rabbit hearts were compared. Also, a quantitative assessment of the drug's effects on a rate-dependent property of anterograde AV node (AVN) conduction, termed the "recovery process," was compared in mature and immature rabbit hearts. The main developmental electrophysiologic findings of this investigation are: (1) in both the mature and immature rabbit heart, d-sotalol increases the anterograde conduction time and prolongs refractoriness of the AVN, yet the minimal concentrations of d-sotalol that produce these changes are lower in the neonate; (2) d-sotalol increases the anterograde refractory period of the His-Purkinje system in both age groups, but increases anterograde infra-Hisian conduction only in the neonate; (3) 1 x 10-4 M d-sotalol significantly changes the time constant of the AVN recovery process in the neonate, but not in the adult; (4) for retrograde conduction, slow conduction through the AVN (HAmax) and infra-Hisian region (VHmax) are increased by d-sotalol in the neonate, but not in the adult. CONCLUSIONS: The findings of this study illustrate that d-sotalol has different effects on parameters of the developing AV conduction system. This implies that there may be maturational changes in the ionic currents that are responsible for anterograde and retrograde AVN and His-Purkinje conduction.

Aging↗
PubMed1995

Pulmonary/systemic flow ratio in children after cavopulmonary anastomosis.

OBJECTIVES: This study attempted to provide a formula for calculation of the pulmonary/systemic flow ratio in children after bidirectional cavopulmonary anastomosis. BACKGROUND: With the bidirectional cavopulmonary anastomosis, only the superior vena cava blood is oxygenated by the lungs. The inferior vena cava flow recirculates into the systemic circulation. The ratio of these flows will determine systemic arterial saturation. METHODS: According to the Fick principle, 1) Systemic cardiac output (liters/min) = Pulmonary venous flow + Inferior vena cava flow; 2) Systemic blood oxygen transport (ml/min) = Pulmonary venous blood oxygen transport + Inferior vena cava blood oxygen transport. By substituting the first equation into the second, Pulmonary/systemic flow ratio = (Systemic saturation - Inferior vena cava saturation)/(Pulmonary venous saturation - Inferior vena cava saturation). RESULTS: We applied the third formula to data obtained from 34 catheterizations in 29 patients after bidirectional cavopulmonary anastomosis. Mean [+/- SD] age at operation was 1.70 +/- 1.43 years, and mean age at catheterization was 2.95 +/- 1.65 years. The pulmonary/systemic flow ratio calculated for all 29 patients was 0.58 +/- 0.09. Of 17 patients with aortography, 10 had systemic to pulmonary collateral vessels. Patients with collateral vessels had a significantly higher pulmonary/systemic flow ratio (0.61 +/- 0.07 vs. 0.53 +/- 0.07, respectively, p < 0.02) and systemic saturation (88 +/- 4% vs. 82 +/- 4%, respectively, p < 0.002) than those without collateral vessels. The pulmonary/systemic flow ratio in those patients with no collateral vessels was similar to the previously reported echocardiographically derived superior vena cava/systemic flow ratio in normal children. CONCLUSIONS: The pulmonary/systemic flow ratio after bidirectional cavopulmonary anastomosis can be calculated. Pulmonary blood flow in these patients determines systemic saturation and accounts for the majority of venous return in young children.

Child, Preschool↗
PubMed1995

The JT interval as a depolarization independent measurement of repolarization: lessons from catheter ablation of the Wolff-Parkinson-White syndrome.

In patients with Wolff-Parkinson-White syndrome (WPW), preexcitation precludes accurate assessment of the ventricular repolarization by the QTc. In patients with long QT syndrome, it has been demonstrated that the JTc does not change when depolarization abnormalities develop. We hypothesized that this phenomenon should also be applicable to WPW patients. To test this, we assessed the surface ECG of 29 patients (16 males, 13 females) with WPW pre- and postablation. The QRS, QT, and JT intervals were measured pre- and postablation at 50 mm/s paper speed in leads II and V2. QTc and JTc were calculated according to Bazett's formula. The average age was 12.8 +/- 4.9 years (range 1.5-21). All patients had no residual preexcitation on postablation ECG. Early and late follow-up ECGs were obtained at 32 +/- 34 days and 388 +/- 197 days postablation, respectively. Both the QRS and the QTc intervals shortened significantly on the postablation versus preablation ECGs (QRS: 115 +/- 23 ms vs 89 +/- 15 ms, respectively; P < 0.0001), QTc: 454 +/- 26 vs 423 +/- 23, respectively; P < 0.0001). The preablation JTc interval did not change, postablation (319 +/- 21 vs 323 +/- 23, respectively; P > 0.2). Also, the JTc interval did not change between early and late follow-up, postablation. JTc is an independent measure of repolarization, not related to depolarization. JTc may be a useful tool in assessing repolarization in patients with WPW and other depolarization abnormalities.

Adolescent↗
PubMed1994

Management of atrial flutter after the Fontan procedure.

OBJECTIVES: The purpose of this study was to review the management of atrial flutter occurring after the Fontan procedure. BACKGROUND: Atrial flutter occurs frequently after the Fontan procedure and is often hemodynamically poorly tolerated. METHODS: The patients' charts were reviewed for relevant information. RESULTS: Between 1984 and 1992, 18 patients had atrial flutter after the Fontan procedure. The underlying heart defect was tricuspid atresia in nine, mitral atresia in six and double inlet left ventricle in three. All but three patients had undergone previous palliative surgery. The time interval from Fontan operation to atrial flutter was < 1 day to 16 years (mean 3.7 years). Seven had early atrial flutter before leaving the hospital. Electrophysiologic study in 15 showed sinus node dysfunction in 12. Atrial flutter was inducible in all patients, and 13 had > 1 flutter configuration. Digoxin and a variety of other antiarrhythmic agents (mean 2.7 drugs/patient) were tried with poor results. Only digoxin, amiodarone, flecainide and propafenone showed some benefit when used alone or in combination. Antitachycardia pacemakers were implanted in 16 patients (endocardial 14, epicardial 2) and, with drugs, were useful in 8 (50%). Because atrial flutter was resistant to treatment, right atriectomy was performed in three patients (with benefit in two, one death), successful radiofrequency catheter His bundle ablation in one patient and catheter ablation of atrial flutter in three patients (two failed, one partial success). One patient underwent heart transplantation, and two died suddenly. Another died of complications after an elective epicardial pacemaker replacement procedure. CONCLUSIONS: Atrial flutter after the Fontan procedure is difficult to control. Aggressive drug and antitachycardia pacemaker therapy help about half of the patients. When these measures fail, other options, such as atriectomy, His bundle ablation or catheter ablation of atrial flutter, need consideration. The risk of sudden death justifies the use of such aggressive treatment methods.

Adolescent↗
PubMed1994

Effect of beta-adrenergic stimulation on the QT interval of children with syncope.

The effect of intravenous bolus doses (0.25, 0.5, 1.0 microgram) of isoproterenol on the QT and RR intervals was reviewed in a group of 34 children undergoing autonomic testing for syncope. Twenty-one patients had a positive orthostatic test and 13 were negative. The two groups (positive and negative) were compared. Baseline QT and RR intervals were similar. The RR interval was shortened by isoproterenol in both groups. Isoproterenol shortened the QT interval in the negative group (as seen in normal persons), but produced QT prolongation in the positive group, although neither reached statistical significance when compared to baseline within the respective group. Comparing the values for RR and QT at each dose of isoproterenol (including baseline) between the two groups showed a significant difference in the QT interval after the 1.0-microgram dose of isoproterenol. Thus children with orthostatic positive neurocardiogenic syncope showed a different QT response to beta-adrenergic stimulation. This lends support to the theory of altered beta-adrenergic sensitivity being present in children with neurocardiogenic syncope.

Adolescent↗
PubMed1994

Radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia in children.

Radiofrequency (RF) catheter ablation has been widely used in the treatment of cardiac arrhythmias. In atrioventricular nodal reentrant tachycardia (AVNRT), the experience has been predominantly in adults. The cardiac electrophysiological records of 18 consecutive children undergoing RF catheter AV node modification for AVNRT were reviewed. The patients (10 females, 8 males) were 8.2-17.9 years of age (mean 13.6 +/- 3.0), weight 15.2-88.1 kg (mean 52.2 +/- 20.8), and height 103-190 cm (mean 157.1 +/- 21.7). Thirteen were on antiarrhythmic medications (1-3, average 1.5 drugs/day). All drugs were discontinued 48 hours prior to the ablations. The procedures were performed under sedation and local anesthesia. Pre- and post-AV node modification electrophysiological studies were performed in all procedures. The 18 patients underwent a total of 25 procedures (1.39 +/- 0.61 per patient): the anterior approach aimed at the antegrade fast pathway in the first four patients and the posterior approach aimed at the slow pathway in the remainder. The number of energy applications was 8-54 (19.8 +/- 10.7) per procedure. The maximum energy used in each procedure was 30-50 watts (33.8 +/- 8.4). The average energy was 24-50 watts (33.0 +/- 6.8). The fluoroscopy time was 7.1-73.4 minutes (29.9 +/- 20.0) per procedure, for a total catheterization time of 228-480 minutes (300.3 +/- 59.1). Preablation spontaneous or induced AVNRT (cycle length 310.4 +/- 55.0 msec) was seen in all except one who had the arrhythmia (cycle length 270 msec) on surface ECG.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Developmental electrophysiology of encainide and its major metabolites on the Purkinje fiber action potential.

OBJECTIVE: With clinical data suggesting that neonates may be more prone to developing electrophysiologic side effects from encainide, this study investigates the in vitro developmental electrophysiologic effects of encainide and its major metabolites on the action potential parameters of the canine cardiac Purkinje fiber. METHODS: With standard microelectrode techniques, the in vitro tonic and rate-related effects of encainide, and its major metabolites (3-methoxy-4-hydroxy encainide, MODE, and O-dimethyl encainide, ODE) were investigated using mature and immature canine cardiac Purkinje fibers. RESULTS: The significant developmental differences in the effects of these compounds on the canine Purkinje fiber illustrated in this study are: (1) 1 x 10(-6) M encainide depresses Vmax in neonatal Purkinje fibers, yet not in the adult. (2) 1 x 10(-6) M MODE lengthens APD90 in the neonate, yet it has no substantial effect in the adult. (3) 1 x 10(-6) M ODE shortens APD90 in the adult, yet it has no appreciable effect on the neonate. (4) Rate-related effects of encainide and ODE are more pronounced in adult Purkinje fibers. CONCLUSION: In contrast to other in vitro studies on class I antiarrhythmic agents, neonatal canine Purkinje fibers seem to be more sensitive than the adult to the tonic depolarization depressant effect of encainide. This in vitro sensitivity parallels clinical experience with the drug in neonatal patients. Although encainide is no longer available for clinical use, these findings highlight the fact that the immature conduction system may show markedly different sensitivities to different class I agents despite the fact that these agents share similar qualitative pharmacologic properties.

Action Potentials↗
PubMed1993

"Superimposition" digital subtraction angiography: evaluation of total anomalous pulmonary venous connection.

Total anomalous pulmonary venous connection (TAPVC) has a relatively high surgical mortality, especially the infracardiac variety. A small left atrium may limit postoperative cardiac output. Superimposition of digitally subtracted angiographic (DSA) images may be used to define pulmonary venous anatomy, left atrial size, and its spatial relationship to the common pulmonary vein. The technique for acquiring superimposed digitally subtracted images and the results of two cases with infracardiac TAPVC are presented. We have found that this superimposition technique is easily performed and may provide important preoperative information in infants with TAPVC.

Angiography, Digital Subtraction↗
PubMed1993

Prospective study of the electrocardiographic effects of imipramine in children.

Because imipramine and desipramine have been implicated in sudden death in children, noninvasive electrophysiologic data were accumulated in 25 patients. Two children were excluded on the basis of resting electrocardiographic and Holter abnormalities. The remaining 23 patients received imipramine to a maximum dose of 5 mg/kg or a serum level of 150 to 250 ng/ml. Consistent but clinically insignificant resting electrocardiographic changes occurred during treatment. Ambulatory electrocardiographic monitoring may be useful when one is assessing the cardiovascular risks of imipramine therapy.

Adolescent↗