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Biomedical subjects

C L Case

Publications and source records attributed to C L Case.

At least 19 recordsLinked to original sources
PubMed2002

Effect of feeding organic and inorganic sources of additional zinc on growth performance and zinc balance in nursery pigs.

Three experiments were conducted to evaluate the effect of feeding pharmacological concentrations of zinc (Zn), from organic and inorganic sources, on growth performance, plasma and tissue Zn accumulation, and Zn excretion of nursery pigs. Blood from all pigs was collected for plasma Zn determination on d 14 in Exp. 1, d 7 and 28 in Exp. 2, and d 15 in Exp. 3. In Exp. 1, 2, and 3, 90, 100, and 15 crossbred (GenetiPorc USA, LLC, Morris, MN) pigs were weaned at 24+/-0.5, 18, and 17 d of age (6.45, 5.47, and 5.3 kg avg initial BW), respectively, and allotted to dietary treatment based on initial weight, sex, and litter. A Phase 1 nursery diet was fed as crumbles from d 0 to 14 in Exp. 1, 2, and 3, and a Phase 2 nursery diet was fed as pellets from d 15 to 28 in Exp. 1 and 2. The Phase 1 and Phase 2 basal diets were supplemented with 100 ppm Zn as ZnSO4. Both dietary phases contained the same five dietary treatments: 150 ppm additional Zn as zinc oxide (ZnO), 500 ppm added Zn as ZnO, 500 ppm added Zn as a Zn-amino acid complex (Availa-Zn 100), 500 ppm added Zn as a Zn-polysaccharide complex (SQM-Zn), and 3,000 ppm added Zn as ZnO. Overall in Exp. 1, pigs fed 500 ppm added Zn as SQM-Zn or 3,000 ppm added Zn as ZnO had greater ADG (P < 0.05) than pigs fed 150 ppm, 500 ppm added Zn as ZnO, or 500 ppm added Zn as Availa-Zn 100 (0.44 and 0.46 kg/d vs 0.35, 0.38, and 0.33 kg/d respectively). Overall in Exp. 2, pigs fed 3,000 ppm added Zn as ZnO had greater (P < 0.05) ADG and ADFI than pigs fed any other dietary treatment. On d 14 of Exp. 1 and d 28 of Exp. 2, pigs fed 3,000 ppm added Zn as ZnO had higher (P < 0.05) plasma Zn concentrations than pigs on any other treatment. In Exp. 3, fecal, urinary, and liver Zn concentrations were greatest (P < 0.05) in pigs fed 3,000 ppm added Zn as ZnO. On d 10 to 15 of Exp. 3, pigs fed 3,000 ppm added Zn as ZnO had the most negative Zn balance (P < 0.05) compared with pigs fed the other four dietary Zn treatments. In conclusion, feeding 3,000 ppm added Zn as ZnO improves nursery pig performance; however, under certain nursery conditions the use of 500 ppm added Zn as SQM-Zn may also enhance performance. The major factor affecting nutrient excretion appears to be dietary concentration, independent of source.

Animal Feed↗
PubMed2001

Atrioventricular block in a newborn with acquired long QT syndrome.

We report a case of 2:1 atrioventricular block associated with acquired long QT syndrome. A newborn presented to our neonatal intensive care unit with intermittent bradycardia due to 2:1 atrioventricular block. Initial evaluation showed QT prolongation and significant electrolytic abnormalities. After correction of the electrolytic imbalance, the QT interval normalized and atrioventricular block resolved. Compared to congenital long QT syndrome with 2:1 atrioventricular block, acquired long QT syndrome with comparable atrioventricular block has a benign prognosis, provided treatment is initiated quickly.

Electrocardiography↗
PubMed1999

Diagnosis and treatment of pediatric arrhythmias.

The work up of arrhythmias encountered in the pediatric patient is usually initiated by primary care providers. Proper treatment of pediatric arrhythmias necessitates recording the suspected rhythm disturbance and an evolution of the underlying cardiac structure and function.

Adolescent↗
PubMed1998

JT dispersion in Wolff-Parkinson-White syndrome: effect of eccentric ventricular depolarization on the dispersion of repolarization.

There is much interest in QT dispersion for noninvasive risk stratification of patients at risk of arrhythmias. However, little is known about the genesis of abnormal QT dispersion. In particular, whether eccentric ventricular depolarization, as seen in preexcitation, can lead to abnormal dispersion of repolarization is unknown. We studied 24 children aged 1-19 years (mean +/- SD, 11 +/- 5 years) with manifest preexcitation due to Wolff-Parkinson-White syndrome who had successful catheter ablation. Standard ECGs done preablation, early postablation (< 1 week), mid postablation (> 1 week, < 2 months), and late postablation (> 2 months) were reviewed. The QRS duration prior to ablation ranged from 90-160 ms (mean +/- SD, 123 +/- 21 ms). On the preablation ECG, the JT and JTc dispersions showed no relationship to the QRS duration (r = 0.04 and 0.07, respectively). There was no change in JT dispersion when the preablation (42 +/- 15 ms) ECG was compared to early (43 +/- 15 ms), mid (44 +/- 13 ms), and late postablation (48 +/- 19 ms) ECGs. There was no significant change in JTc dispersion as well. Thus, JT dispersion is unrelated to QRS duration and unaffected by catheter ablation in patients with Wolff-Parkinson-White syndrome. Eccentric ventricular depolarization does not lead to abnormal dispersion of repolarization.

Adolescent↗
PubMed1998

Differential developmental effects of acute hypoxia on the rabbit atrioventricular conduction axis.

The differential developmental effects of hypoxia on antegrade fast and slow and retrograde conduction through the atrioventricular junction are unknown. This study describes the effects of hypoxia on fast and slow antegrade atrioventricular node, infra-Hisian and retrograde conduction in immature and mature hearts during premature pacing protocols in excise, perfused adult and neonatal rabbits. The results are: (1) antegrade conduction delay through the atrioventricular node is the same developmentally, but delay through the His-Purkinje system is greater in adults; (2) hypoxia reduces the extra delay in the His-Purkinje system in adults; (3) fast atrioventricular node conduction is more sensitive to hypoxia in neonates than in adults, and slow atrioventricular node conduction is more sensitive to hypoxia in adults than in neonates, and (4) retrograde atrioventricular node conduction is more resistant to hypoxia in neonates than in adults.

Aging↗
PubMed1997

QRS prolongation is associated with inducible ventricular tachycardia after repair of tetralogy of Fallot.

Prolonged QRS duration on the electrocardiogram has been found to predict adverse arrhythmic events in patients late after repair of tetralogy of Fallot. Whether QRS duration can also predict inducible ventricular tachycardia (VT) at electrophysiologic study is unknown. Between 1984 and 1995 we studied 135 survivors of tetralogy of Fallot surgery whose age at surgery was 34 days to 37 years (3.7 +/- 3.9, median 2.5) and age at electrophysiologic study was 1.4 to 43 years (9.7 +/- 8.2, median 6.7). QRS duration was 80 to 240 ms (137 +/- 29) and > or = 180 ms in 9 patients. Sustained VT was induced in 22 patients (monomorphic in 17). Induced sustained monomorphic VT was related to QRS duration, right ventricular dimension, H-V interval, and presence of symptoms. QRS duration was also related to induced sustained monomorphic VT by multivariate analysis. QRS duration > or = 180 ms was 35% sensitive and 97% specific for induced sustained monomorphic VT. QRS duration was related to induced sustained monomorphic VT even when only asymptomatic patients were analyzed. A QRS duration > or = 180 ms was 100% sensitive and 96% specific for detecting clinical VT. Prolonged QRS duration on the electrocardiogram is associated with induced sustained monomorphic VT on electrophysiologic study. The finding of prolonged QRS duration should suggest the need for further testing to determine the risk of adverse arrhythmic events in patients after repair of tetralogy of Fallot, even if they are asymptomatic.

Adolescent↗
PubMed1997

Catheter ablation treatment of supraventricular tachycardia-induced cardiomyopathy.

OBJECTIVE: To investigate the efficacy of radiofrequency catheter ablation (RFCA) as an alternative nonpharmacological therapy for tachycardia-induced cardiomyopathy. DESIGN: A retrospective study of 8 pediatric patients (age range, 10 months to 21 years) who underwent RFCA for an incessant supraventricular tachycardia-induced cardiomyopathy. A patient's tachycardia was considered incessant if the tachycardia was present more than 75% of the time. The left ventricular shortening fraction, as measured by echocardiography, before and after ablation, was used as the index of cardiac function. Cardiomyopathy was defined as a left ventricular shortening fraction of 28% or less. RESULTS: Following RFCA, 7 patients had total resolution of their tachycardia and were discharged from the hospital with no antiarrhythmic medications. The remaining patient's tachycardia was modified by the catheter ablation and was subsequently controlled with flecainide acetate. With follow-up ranging from 9 months to 3 years, all patients have normal cardiac function as documented by echocardiography. No significant morbidity resulted from the catheter ablations. CONCLUSIONS: Tachycardia-induced cardiomyopathy is amenable to "curative" therapy with RFCA. Ventricular function returns to normal after the successful catheter ablation procedure.

Adolescent↗
PubMed1997

Beta2-agonist induced ventricular dysrhythmias secondary to hyperexcitable conduction system in the absence of a long QT syndrome.

BACKGROUND: The use of inhaled beta 2-agonists for bronchodilation in the treatment of lower airway obstruction is accepted worldwide. These agents are used for symptomatic relief of lower airway obstruction and, as well, can be employed prophylactically in exercise-induced bronchospasm. Cardiac dysrhythmias, specifically the long QT syndrome, have been associated with cardiac events precipitated by sympathomimetics. There are reports of documented long QT syndrome in association with syncope in children; however, there are no reports of beta 2-agonist-induced syncope in the absence of long QT syndrome. OBJECTIVE: To determine predisposing cardiac factors resulting in syncope associated with inhaled beta 2-agonist use. METHOD: Case report. The index case was evaluated for cardiac pathology through non-invasive techniques, cardiac catheterization, and electrophysiologic studies. Electrophysiologic studies included provocative challenge with parenteral adrenergic agents. RESULTS: Non-invasive studies were unremarkable. There was no evidence of prolonged QT syndrome or support for vasopressor syncope. Electrophysiologic studies revealed reproducible polymorphic ventricular tachycardia. This predisposition required a ventricular stimulation program of higher intensity while on mexilitine. CONCLUSIONS: This case of syncope associated with inhaled, short-acting beta 2-agonist resulted from a hyperexcitable conduction system rather than the presence of a long QT syndrome.

Adrenergic beta-Agonists↗
PubMed1997

Different effects of flecainide on atrioventricular conduction properties in the adult and immature rabbit heart.

The influence of flecainide (0.1, 0.5, 1.0, and 2.0 micrograms/mL) on atrioventricular (AV) conduction was studied in neonatal and adult perfused rabbit hearts using extracellular bipolar surface electrograms and premature atrial and ventricular pacing. Flecainide produced a concentration and rate-related increase in the steady-state nodal conduction (AHmin) and an increase in slow AH conduction (AHmax) in both age groups. The drug produced significant increases in the refractory periods of the atrium, AV node, His-Purkinje system, and ventricular myocardium. The neonatal refractory periods were significantly greater at lower or the same drug concentrations than those of the adult. The neonatal Wenckebach cycle length was significantly greater with a lower concentration of drug (0.5 microgram/mL) than was the adult Wenckebach cycle length. The His-Purkinje system steady-state conduction time (HVmin) was increased by a lower concentration of drug in the neonate (0.5 microgram/mL) as compared with 2.0 micrograms/mL in the adult. These data show that across a wide range of AV conduction parameters, the neonatal preparations responded to a lower concentration of flecainide than did the adult preparations. These findings may, in part, be the basis for the reported greater efficacy of the drug in children than in adults.

Aging↗
PubMed1997

Radiofrequency ablation of a posteroseptal accessory pathway via the middle cardiac vein in a six-year-old child.

Although radiofrequency ablation is highly successful in patients with the Wolff-Parkinson-White syndrome, certain pathways remain refractory to ablation. In particular, subepicardial pathways often fail ablation via an endocardial approach. In adult patients, left-sided subepicardial pathways have been treated successfully using energy delivery within the coronary sinus. To document the safety and efficacy of this approach in children, we present the case of a 6-year-old boy who underwent radiofrequency ablation of a posteroseptal pathway via energy delivery within the middle cardiac vein. Follow-up study showed no evidence of recurrence or gross coronary vascular injury.

Catheter Ablation↗
PubMed1996

Radiofrequency catheter ablation of right ventricular outflow tachycardia in children and adolescents.

OBJECTIVES: The current study reviews the safety and efficacy of radiofrequency catheter ablation for the treatment of right ventricular outflow tachycardia in children and adolescents and describes a modified method for mapping the tachycardia focus. BACKGROUND: Although radiofrequency catheter ablation has proved highly effective for the treatment of supraventricular tachycardia during childhood and adolescence, its application in children with idiopathic right ventricular outflow tachycardia has been limited. METHODS: Six children (mean [+/- SD] age 10.6 +/- 2.4 years, range 6 to 16) with right ventricular outflow tachycardia underwent seven radiofrequency catheter ablation procedures. The mean tachycardia cycle length was 323 +/- 24 ms (range 300 to 360). Two multipolar catheters were positioned in the right ventricular outflow tract to map the tachycardia focus. RESULTS: Radiofrequency catheter ablation was successful in five (83%) of the six children (95% confidence interval 36% to 99%). At successful ablation sites, local endocardial activation time preceded the surface QRS onset by 46 +/- 5 ms (range 37 to 57), and there was concordance of the 12-lead pace map and the electrocardiogram (ECG) in 11 (one patient) to 12 ECG leads (four patients). One patient developed complete right bundle branch block during radiofrequency catheter ablation. There were no additional complications and no clinical recurrences over a mean follow-up period of 12.7 +/- 3.8 months (range 9 to 22). CONCLUSIONS: These results suggest that radiofrequency catheter ablation is a safe and effective treatment for right ventricular outflow tachycardia during childhood and adolescence. In addition, tachycardia mapping may be enhanced by use of a multipolar right ventricular outflow catheter technique.

Adolescent↗
PubMed1996

High prevalence of repolarization abnormalities in children with simple ventricular ectopy.

BACKGROUND: Premature ventricular contractions (PVCs) may occur in 0.3 to 2.2% of routine resting electrocardiograms (ECGs) in children with structurally normal hearts. HYPOTHESIS: This study tests the hypothesis that repolarization abnormalities are present more frequently on the surface ECG in pediatric patients with benign ventricular ectopy. METHODS: A retrospective study was performed examining 32 children with benign ventricular ectopy and structurally normal hearts. The surface ECG was carefully reviewed, concentrating on repolarization abnormalities as evidenced by a prolonged QTc, a prolonged JTc, and/or an abnormal T-wave vector. QTc was calculated using Bazett's formula and considered prolonged if > 440 ms, and the JTc was calculated using a formula analogous to Bazett's formula and considered prolonged if > 340 ms. The T-wave vector was considered normal if between 0 to +90 degrees, concordant with the frontal QRS axis and within 60 degrees of the QRS axis. There were 13 females (41%) and 19 males (59%) with an average age of 9.1 years (range 1-16.1 years). These patients were then compared with age- and gender-matched controls. Fourteen of 32 study patients (44%) and 2 of 32 controls (6%) had evidence of repolarization abnormalities. RESULTS: Using chi 2 analysis, there was a significant difference between groups (p = 0.0005). No patient had an abnormal T-wave vector and there were no other significant ECG abnormalities. There was no significant relationship between repolarization abnormalities and patient gender or age. CONCLUSION: A significant percentage (44%; P = 0.0005) of children with benign ventricular ectopy have associated repolarization abnormalities as evidenced by a prolonged QTc and/or JTc. This finding suggests that children with "benign PVCs" may have repolarization changes indicative of underlying substrate abnormalities.

Adolescent↗
PubMed1996

Learning curve for radiofrequency catheter ablation in pediatrics at a single institution.

We examined the learning curve for radiofrequency ablation in pediatrics at a single institution. The first 146 cases were retrospectively reviewed, including patients < or = 21 years old with a single tachycardia diagnosis who were undergoing radiofrequency ablation for the first time. Data regarding demographics, electrophysiologic properties of the tachycardia, and procedural characteristics were tabulated. Data were then analyzed for evidence of association between these characteristics, success, and experience. Results revealed that success rates improved significantly with experience, reaching 85% success for all cases after < 100 cases attempted. Success for accessory pathway tachycardias alone reached > 93%. The number of cases of nonpathway tachycardias undertaken significantly increased as experience was gained. Fluoroscopy time improved to 34 +/- 27 minutes after < 100 cases. In conclusion, as experience was gained, (1) success rates showed a steep improvement; (2) the population undergoing radiofrequency ablation clearly shifted to include more difficult diagnoses; and (3) fluoroscopy time significantly decreased.

Adolescent↗
PubMed1996

Interatrial septal aneurysms and atrial arrhythmias in infants.

Studies have suggested that interatrial septal aneurysms (IASAs) may be the initiating mechanism of supraventricular tachycardia (SVT) in newborns and infants. A retrospective study was performed to determine the incidence of IASAs in 30 infants with atrial arrhythmias (SVT, atrial flutter, or frequent premature atrial contractions) and their possible relation to the mechanism of atrial arrhythmias. An IASA was defined as dilation of the septum > 5 mm beyond the plane of the atrial septum and associated with redundant tissue and abnormal mobility. The study patients were compared with age and sex-matched control subjects. Four (13%) of the 30 study patients and 2 (7%) of 30 control subjects had an IASA (difference not significant). In contrast to previous reports, this study demonstrates that there is not a significant relation between the presence of IASAs and the onset and recurrence of atrial arrhythmias.

Atrial Flutter↗
PubMed1996

Lack of proarrhythmia as assessed by Holter monitor after atrial radiofrequency ablation of supraventricular tachycardia in children.

The purpose of this study was to assess the short-term arrhythmogenicity of atrial radiofrequency (RF) ablation lesions in children. Patients with the greatest exposure to RF energy comprised the study group. Holter data on 35 RF ablation procedures in 31 patients with a median age of 13.2 years (range 3 months to 20 years) was retrospectively analyzed. Patients received an average of 19.9 (SD = 13.6) RF lesions, all delivered by an atrial approach. Supraventricular ectopy and ventricular ectopy were compared immediately before and after and 4 to 9 weeks after RF ablation by serial Holter monitoring. Factors thought to possibly predispose patients to a proarrhythmic effect were used to define subgroups for separate analysis. No increase in ambient supraventricular ectopy or ventricular ectopy was observed either immediately after or 4 to 9 weeks after RF ablation compared with the baseline Holter recordings. Children exposed to relatively large doses of RF energy may demonstrate transient and asymptomatic nonsustained tachycardias in the short term. However, no new sustained tachycardias and no increase in supraventricular or ventricular ambient ectopy are detected by short-term Holter monitoring.

Adolescent↗
PubMed1996

Changes in atrioventricular conduction properties with refractory-period modulation.

Dofetilide, clofilium, and risotilide, three drugs known to prolong cardiac action potentials and refractory periods, were studied by using a perfused isolated rabbit heart preparation with intermittent premature pacing and bipolar surface electrograms. The rate-related effects of these drugs on atrioventricular (AV) conduction were tested by pacing at a long (400 ms) and a short (250 ms) basic cycle length (BCL). All three drugs increased refractory periods in a concentration-dependent manner in most segments of the AV axis. The maximal atrio-His (AH) conduction interval (AHmax) and delta AH (AHmax - AHmin) produced by premature pacing was decreased by the highest concentration of each drug at the 400-ms BCL, whereas only clofilium reduced AHmax and delta AH at the 250-ms BCL. Changes in delta AH correlated best with changes in the atrial functional refractory period. The His-Purkinje system conduction interval (HV), represented by delta HV, was unaffected by any drug at either BCL. These results show that if atrial or nodal refractory periods are increased sufficiently, AHmax but not AHmin was decreased at the 400-ms BCL. Because dofetilide and risotilide did not affect AHmax at the 250-ms BCL, these drugs may be less effective at preventing AV nodal reentrant tachycardias than a drug such as clofilium that displays less rate dependency.

Animals↗
PubMed1996

Late endocardial pacing lead body migration compromising Fontan physiology.

Migration of intracardiac transvenous pacing leads may occur. There is a known risk of intrapulmonary ventricular pacing lead migration in patients with endocardial lead systems. In the current report we present the late intrapulmonary migration of an endocardial atrial pacing lead body. The patient had undergone antitachycardia pacemaker placement to control recurrent atrial tachyarrhythmias following the Fontan procedure. Although the lead electrode remained in place and continued to pace, the lead body migrated, causing severe obstruction to blood flow. This resulted in severe cardiac decompensation, which was ultimately ameliorated by lead repositioning.

Adult↗