Return to play? Practical considerations for young athletes with cardiovascular disease.

Sports activities are an important part of the daily life of young persons. For a small proportion of those with cardiac conditions, sports participation can result in sudden cardiac arrest. Children and adolescents often participate in both organised and spontaneous play, for which activity guidelines are needed when a condition known to cause sudden cardiac death is identified. This article examines the current guidelines that provide recommendations for sports participation by young persons with cardiovascular disease and reviews the current information on risks of physical activity for those with specific cardiac conditions. The goal of the practitioner is to balance the risks of restriction from physical activity with the benefits of participation. Some practical recommendations are offered for consideration, along with potential alternatives to absolute restriction.

Potential additional indicators for pacemaker requirement in isolated congenital atrioventricular block.

Low heart rate is the predominantly used indication for pacemaker intervention in patients with isolated congenital atrioventricular block (CAVB). The aim of this study was to compare the difference in heart rates recorded with ECG and Holter monitoring between paced (PM) and nonpaced (NPM) patients with isolated CAVB before pacemaker implantation to identify additional predictors for future PM need. Retrospective evaluation of atrial and ventricular rates (electrocardiography) and minimal and maximal (Holter) heart rates in 129 CAVB patients prior to PM implantation (n = 93) was performed, and results are expressed in V adjusted for age and sex. The average V score for the atrial rate was 0.51 (n = 50) in the PM group and 0.60 (n = 22) in the NPM group (not-significant). The average z score for the ventricular (average) rate was -0.91 (n = 83) in the PM group and -0.93 (n = 33) in the NPM group (not-significant). Minimal heart rate was -0.94 (n = 61) in the PM group and -0.86 (n = 25) in the NPM group (not significant). Maximal heart rate was -0.96 (n = 61) in the PM group and -0.95 (n = 26) in the NPM group (not significant). Initial recordings of the average heart rate and the minimal and maximal heart rate recorded during Holter monitoring do not seem to predict future pacemaker need in patients with CAVB. Studies with exercise stress tests are needed to confirm these findings.

The Pediatric Heart Network: a primer for the conduct of multicenter studies in children with congenital and acquired heart disease.

Most contemporary diagnostic and treatment strategies for pediatric patients with cardiovascular disease are not supported by evidence from clinical trials but instead are based on expert opinion, single-institution observational studies, or extrapolated from adult cardiovascular medicine. In response to this concern, the National Heart, Lung, and Blood Institute established the Pediatric Heart Disease Clinical Research Network (PHN) in 2001. The purposes of this article are to describe the initiation, structure, and function of the PHN; to review the ongoing studies; and to address current and future challenges. To date, four randomized clinical trials and two observational studies have been launched. Design and conduct of complex, multicenter studies in children with congenital and acquired heart disease must address numerous challenges, including identification of an appropriate clinically relevant primary endpoint, lack of preliminary data on which to base sample size calculations, and recruitment of an adequate number of subjects. The infrastructure is now well developed and capable of implementing complex, multicenter protocols efficiently and recruiting subjects effectively. The PHN is uniquely positioned to contribute to providing evidence-based medicine for and improving the outcomes of pediatric patients with cardiovascular disease.

Effects of beta-adrenergic antagonists on the QT measurements from exercise stress tests in pediatric patients with long QT syndrome.

It has been proposed that beta-adrenergic antagonist protection against cardiac events in patients with long QT syndrome (LQTS) may be related to a decrease in baseline QTc dispersion. To determine the effects of beta-blocker therapy on QT measurements, we evaluated the exercise tests of 25 pediatric patients with LQTS. Measurements were made of the maximum QTc interval and QTc dispersion during the various segments of the exercise test. There was no statistically significant difference between the pre-beta-blocker and post-beta-blocker maximum QTc interval during the supine (0.473 +/- 0.039 vs 0.470 +/- 0.038 sec), exercise (0.488 +/- 0.044 vs 0.500 +/- 0.026 sec), or recovery (0.490 +/- 0.031 vs 0.493 +/- 0.029 sec) phases of the exercise stress test. There was also no statistically significant difference between the pre-beta-blocker and post-beta-blocker QTc dispersion during the supine (0.047 +/- 0.021 vs 0.058 +/- 0.033 exercise vs 0.063 +/- 0.028 sec), or recovery (0.045 +/- 0.023 vs 0.052 +/- 0.026 sec) phases of the exercise stress test. Therefore, the protection that beta-blockers offer appears not to be related to a reduction of the baseline QTc interval or a decrease of QTc dispersion.

The incidence of arrhythmias in a pediatric cardiac intensive care unit.

A pediatric cardiac intensive care unit (CICU) manages critically ill children and adults with congenital or acquired heart disease. These patients are at increased risk for arrhythmias. The purpose of this study was to prospectively evaluate the incidence of arrhythmias in a pediatric CICU patient population. All patients admitted to the CICU at the Cardiac Center at The Children's Hospital of Philadelphia between December 1, 1997, and November 30, 1998, were evaluated prospectively from CICU admission to hospital discharge via full disclosure telemetry reviewed every 24 hours. Arrhythmias reviewed included nonsustained and sustained ventricular tachycardia (VT), nonsustained and sustained supraventricular tachycardia (SVT), atrial flutter and fibrillation, junctional ectopic tachycardia, and complete heart block. We reviewed 789 admissions consisting of 629 patients (age range, 1 day-45.5 years; median, 8.1 months). Hospital stay ranged from 1 to 155 days (total of 8116 patient days). Surgical interventions (n = 602) included 482 utilizing cardiopulmonary bypass. During the study period, there were 44 deaths [44/629 patients (7.0%)], none of which were directly attributable to a primary arrhythmia. The operative mortality was 5.1%. Overall, 29.0% of admissions had one or more arrhythmias the most common arrhythmia was nonsustained VT (18.0% of admissions), followed by nonsustained SVT (12.9% of admissions). Patients admitted to a pediatric CICU have a high incidence of arrhythmias, most likely associated with their underlying pathophysiology and to the breadth of medical and surgical interventions conducted.

Permanent epicardial pacing in pediatric patients: seventeen years of experience and 1200 outpatient visits.

BACKGROUND: The purpose of this study was to evaluate the long-term outcome of all pediatric epicardial pacing leads. METHODS AND RESULTS: All epicardial leads and 1239 outpatient visits between January 1, 1983, and June 30, 2000, were retrospectively reviewed. Pacing and sensing thresholds were reviewed at implant, at 1 month, and at subsequent 6-month intervals. Lead failure was defined as the need for replacement or abandonment due to pacing or sensing problems, lead fracture, or phrenic/muscle stimulation. A total of 123 patients underwent 207 epicardial lead (60 atrial/147 ventricular, 40% steroid) implantations (median age at implant was 4.1 years [range 1 day to 21 years]). Congenital heart disease was present in 103 (84%) of the patients. Epicardial leads were followed for 29 months (range 1 to 207 months). The 1-, 2-, and 5-year lead survival was 96%, 90%, and 74%, respectively. Compared with conventional epicardial leads, both atrial and ventricular steroid leads had better stimulation thresholds 1 month after implantation; however, only ventricular steroid leads had improved chronic pacing thresholds (at 2 years: for steroid leads, 1.9 muJ [from 0.26 to 16 mu]; for nonsteroid leads, 4.7 muJ [from 0.6 to 25 muJ]; P<0.01). Ventricular sensing was significantly better in steroid leads 1 month after lead implantation (at 2 years: for steroid leads, 8 mV [from 4 to 31 mV]; for nonsteroid leads, 4 mV [from 0.7 to 10 mV]; P<0.01). Neither congenital heart disease, lead implantation with a concomitant cardiac operation, age or weight at implantation, nor the chamber paced was predictive of lead failure. CONCLUSIONS: Steroid epicardial leads demonstrated relatively stable acute and chronic pacing and sensing thresholds. In this evaluation of >200 epicardial leads, lead survival was good, with steroid-eluting leads demonstrating results similar to those found with historical conventional endocardial leads.

Dilated cardiomyopathy in isolated congenital complete atrioventricular block: early and long-term risk in children.

OBJECTIVES: We sought to identify the risk factors predicting the development of dilated cardiomyopathy (DCM) in patients with isolated congenital complete atrioventricular block (CCAVB). BACKGROUND: Recently evidence has emerged that a subset of patients with CCAVB develop DCM. METHODS: This was a retrospective study of 149 patients with CCAVB who had heart size and left ventricular (LV) function assessed by echocardiography and chest radiography over a follow-up period of 10 +/- 7 years. RESULTS: Nine patients developed DCM at the age of 6.5 +/- 5 years. No definite cause could be identified. In these nine patients, CCAVB was diagnosed in eight at 23 +/- 2.3 weeks gestation and in one at birth. Maternal SSA/SSB antibodies were confirmed in seven of the nine patients. Pacemakers were implanted in eight patients in the first month and in one patient at five years of age. The initial left ventricular end-diastolic dimension (LVEDD) was in the 96th +/- 2.6 percentile and the cardiothoracic (CT) ratio was 64 +/- 3.8% in the nine patients who developed DCM, and differed significantly in patients with CCAVB (p < 0.005) who did not develop DCM. The LVEDD and CT ratio did not decrease in the patients with CCAVB and DCM, but decreased significantly in the patients with CCAVB without DCM (p < 0.001) once pacing was initiated. Two patients with DCM died within two months of diagnosis; one patient is neurologically compromised; two patients received a heart transplant; and four patients are listed for heart transplantation. CONCLUSIONS: Isolated CCAVB is associated with a long-term risk for the development of DCM. Risk factors may be SSA/SSB antibodies, increased heart size at initial evaluation and the absence of pacemaker-associated improvement.

Epicardial pacemaker implantation and follow-up in patients with a single ventricle after the Fontan operation.

OBJECTIVES: There is an increasing incidence of sinus node dysfunction after the Fontan procedure. Inability to maintain atrioventricular synchrony after the Fontan operation has been associated with an adverse late outcome. Although pacing may be helpful as a primary or adjunct modality after the Fontan procedure, the effects of performing a late thoracotomy or sternotomy for epicardial pacemaker implantation are unknown. In addition, little is known about the long-term effectiveness of epicardial leads in patients with single ventricles. The purpose of this study was to compare the hospital course and follow-up of epicardial pacing lead implantation in patients with Fontan physiology and patients with 2-ventricle physiology. METHODS: We retrospectively reviewed all isolated epicardial pacemaker implantations and outpatient evaluations performed between January 1983 and June 2000. RESULTS: There was no difference in the perioperative course for the 31 Fontan patients (27 atrial and 41 ventricular leads [68 total]) compared with the 56 non-Fontan subjects (9 atrial and 61 ventricular leads [70 total]). The median length of stay in Fontan and non-Fontan patients was 3 and 4 days, respectively. There was no early mortality in either group. Pleural drainage for 5 days or longer was reported in 4% of the Fontan cohort and 3% of the non-Fontan group. Late pleural effusions were identified in only 2 patients in the Fontan group and 2 patients in the non-Fontan group. There was no significant difference in epicardial lead survival between the Fontan group and the non-Fontan group (1 year, 96%; 2 years, 90%; 5 years, 70%). The overall incidence of lead failure was 17% (24/138). CONCLUSIONS: Epicardial leads can be safely placed in Fontan patients at no additional risk compared to patients with biventricular physiology. Sensing and pacing qualities were relatively constant in both the Fontan and non-Fontan groups over the first 2 years after implantation.

Somatic growth failure after the Fontan operation.

Our study was designed to characterize the patterns of growth, in the medium term, of children with functionally univentricular hearts managed with a hemi-Fontan procedure in infancy, followed by a modified Fontan operation in early childhood. Failure of growth is common in patients with congenital cardiac malformations, and may be related to congestive heart failure and hypoxia. Repair of simple lesions appears to reverse the retardation in growth. Palliation of the functionally single ventricular physiology with a staged Fontan operation reduces the adverse effects of hypoxemia and prolonged ventricular volume overload. The impact of this approach on somatic growth is unknown. Retrospectively, we reviewed the parameters of growth of all children with functionally univentricular hearts followed primarily at our institution who had completed a staged construction of the Fontan circulation between January 1990 and December 1995. Measurements were available on all children prior to surgery, and annually for three years following the Fontan operation. Data was obtained on siblings and parents for comparative purposes. The criterions of eligibility for inclusion were satisfied by 65 patients. The mean Z score for weight was -1.5 +/- 1.2 at the time of the hemi-Fontan operation. Weight improved by the time of completion of the Fontan circulation (-0.91 +/- 0.99), and for the first two years following the Fontan operation, but never normalized. The mean Z scores for height at the hemi-Fontan and Fontan operations were -0.67 +/- 1.1 and -0.89 +/- 1.2 respectively. At most recent follow-up, with a mean age of 6.1 +/- 1.3 years, and a mean time from the Fontan operation of 4.4 +/- 1.4 years, the mean Z score for height was -1.15 +/- 1.2, and was significantly less than comparable Z scores for parents and siblings. In our experience, children with functionally univentricular hearts who have been palliated with a Fontan operation are significantly underweight and shorter than the general population and their siblings.

Modifications to the cavopulmonary anastomosis do not eliminate early sinus node dysfunction.

OBJECTIVE: To determine whether operations that theoretically jeopardize the sinus node (hemi-Fontan and/or lateral tunnel Fontan procedures) are associated with a greater risk of sinus node dysfunction than those that theoretically spare the sinus node (bidirectional Glenn and/or extracardiac conduit). METHODS: Between January 1, 1996, and December 31, 1999, a prospective cohort study was conducted evaluating the incidence of sinus node dysfunction in patients undergoing a bidirectional Glenn or hemi-Fontan procedure and those in whom the Fontan repair was completed with either an extracardiac conduit or a lateral tunnel. Sinus node dysfunction was defined (1) as a heart rate more than 2 SD below age-adjusted norms or (2) as a predominant junctional rhythm and/or a sinus pause of more than 3 seconds as determined by the resting electrocardiogram and/or ambulatory monitoring at hospital discharge. RESULTS: Fifty-one patients had a bidirectional Glenn shunt (mean age 7.8 +/- 5.1 months) and 79 a hemi-Fontan procedure (mean age 6.9 +/- 2.8 months). The incidence of sinus node dysfunction on postoperative day 1 was significantly higher after the hemi-Fontan (36%) than after the bidirectional Glenn shunt (9.8%); however, by hospital discharge this difference was no longer apparent (hemi-Fontan [8%]; bidirectional Glenn [6%]; P = not significant). No difference in early sinus node dysfunction was discernible after the extracardiac conduit (4/30 [13%]) compared with the lateral tunnel Fontan procedure (6/46 [13%]) (P = not significant). No diagnostic or perioperative variables were predictive of sinus node dysfunction. CONCLUSIONS: Avoidance of surgery near the sinus node has no discernible effect on the development of early sinus node dysfunction. Thus, concerns about early sinus node dysfunction should not override patient anatomy or surgeon preference as determinants of which cavopulmonary anastomosis to perform.

Low temperature and low energy radiofrequency modification of atrioventricular nodal slow pathways in pediatric patients.

OBJECTIVES: To report our experience using low temperature and energy in the modification of the slow pathway in pediatric patients with atrioventricular nodal reentrant tachycardia. BACKGROUND: A concern in performing a slow pathway modification is the possible damage of the normal AV conduction system. Lesion size has been shown to have a linear relationship with temperature. Previous reports have used energy of 25-50 W that generate temperatures of 60 degrees C -70 degrees C for successful procedures. METHODS: Report of results of attempted AV nodal slow pathway modification in 17 consecutive pediatric patients < 15 years of age at The Children's Hospital of Philadelphia from April 1995 to November 1997 using low temperature and energy. RESULTS: There were 18 successful slow pathway modifications with 1 recurrence in 17 patients. The maximum energy used during successful lesions was 32.7 +/- 13.8 W (range 15-50 W) with a mean energy of 26.4 +/- 13.3 W (range 12-48 W). The peak temperature during these lesions was 55.1 degrees C +/- 4.1 degrees C (range 48 degrees C-64 degrees C) with a mean temperature of 47.9 degrees C +/- 2.7 degrees C (range 44 C-540C). The mean number of radiofrequency lesions required for a successful modification was 5.8 +/- 6.7 (median 4.0, range 1-26). Patients have been followed for 2.08 +/- 0.79 years. CONCLUSIONS: Slow pathway modification can be performed successfully with a low incidence of recurrence in the pediatric patient using low energy and temperature. It is possible that this may lead to smaller lesions.

Comparison of left and right atrial epicardial pacing in patients with congenital heart disease.

BACKGROUND: Complex congenital heart disease (CHD) often necessitates the use of epicardial pacing. Adequate right atrial (RA) sensing and pacing thresholds are often difficult to obtain due to suture line scarring and RA dilatation. The purpose of this study was to evaluate the placement of left atrial (LA) epicardial leads in children. METHODS: Patient demographics, pacing, and sensing data of atrial pacing systems implanted between January 1994 and January 1997 were collected. RESULTS: Forty-nine pacing systems were implanted: 14 LA epicardial, 19 RA epicardial, and 16 transvenous in the right atrium. Lead impedance, current, and energy were similar in the two epicardial groups throughout the study. Energy thresholds (ET) were lower in the LA than RA at 6 months, and 1 and 2 years (p < 0.05). Analysis of post-Fontan patients performed alone revealed a lower ET in the LA as compared with the RA. Pacing and sensing parameters from transvenous leads are presented for relative comparison. CONCLUSIONS: Transvenous leads are most efficient but often contraindicated in complex CHD. LA leads offer lower energy thresholds than RA leads with similar sensing parameters.

Sinus node function after a systematically staged Fontan procedure.

BACKGROUND: Sinus node dysfunction has been previously reported to occur in 13% to 16% of patients after the Fontan operation. Although there is concern that an intermediate cavopulmonary connection may increase the risk of sinus node dysfunction, previous studies have not reported on patients routinely staged to a Fontan operation. This study sought to determine the early and late incidences of sinus node dysfunction in patients systematically and uniformly staged to a Fontan operation after a prior hemi-Fontan. METHODS AND RESULTS: To determine the early incidence of sinus node dysfunction, hospital records and perioperative ECGs were reviewed in all 287 patients having had a staged Fontan operation between January 1990 and December 1995. A cross-sectional analysis was performed on 220 of 239 surviving patients (92%) to determine the late incidence of sinus node dysfunction. Sinus node dysfunction was present in 7% of the patients before and in 15% after the hemi-Fontan. Although most patients (81%) regained normal sinus node function between the 2 stages, 23% had sinus node dysfunction in the early postoperative period after the Fontan. Of the 95 patients followed for > 4 years after the Fontan operation, 44% had sinus node dysfunction. However, at a mean follow-up of 3.5 +/- 1.7 years, only 16 patients (6.7%) had received a pacemaker and only 10 (4.1%) had documented atrial flutter. CONCLUSIONS: Perioperative sinus node dysfunction is common after both the hemi-Fontan and the Fontan procedures. Although many patients regain sinus node function between the 2 stages, late sinus node dysfunction is common and more likely to occur in patients with early sinus node dysfunction and those with longer follow-up.

Perioperative conduction and rhythm disturbances after the Ross procedure in young patients.

BACKGROUND: The Ross procedure is performed for a variety of left ventricular outflow tract diseases in children. The preoperative hemodynamic burden of pressure or volume overload and associated ventricular hypertrophy can predispose to ventricular arrhythmias. Additional procedures performed with the Ross procedure (eg, Konno) may damage the conduction system. METHODS: Between January 1995 and February 1997, the Ross procedure was performed in 42 patients, 31 (74%) of whom had 71 prior interventions. Concomitant procedures (n = 42 in 23 patients) included 17 annular-enlarging procedures. Screening was performed for perioperative conduction and rhythm abnormalities. RESULTS: There was one postoperative death. Perioperative ventricular tachycardia occurred in 12 patients (29%), with 2 receiving antiarrhythmic medication for ventricular tachycardia at discharge. Transient complete heart block occurred in 3 patients, all of whom had concomitant procedures performed in the subaortic area; all patients were discharged in sinus rhythm and no patient received a permanent pacemaker. CONCLUSIONS: The Ross procedure can be performed successfully in children with complex cardiac disease with low mortality and perioperative morbidity. The incidence of perioperative ventricular tachycardia is high (29%), suggesting the need for vigilant perioperative monitoring and long-term surveillance.

Transcatheter radiofrequency ablation for congenital junctional ectopic tachycardia in infancy.

Congenital junctional ectopic tachycardia (JET) is a difficult to treat arrhythmia with a variably poor response to pharmacologic intervention. We report on the successful treatment of a 17-day-old infant with JET via transcatheter radiofrequency ablation of the arrhythmogenic focus resulting in resolution of the tachycardia and maintenance of normal atrioventricular nodal function. Transcatheter radiofrequency ablation techniques should be considered in infants with life-threatening arrhythmia recalcitrant to standard forms of drug therapy.

QT and JT dispersion in children with long QT syndrome.

INTRODUCTION: Abnormalities of ventricular repolarization leading to ventricular arrhythmias place children with long QT syndrome at high risk for sudden death. Dispersion of the QT (QTd) and JT (JTd) intervals, as markers of cardiac electrical heterogeneity, may be helpful in evaluating children with long QT syndrome and identifying a subset of patients at high risk for development of critical ventricular arrhythmias (ventricular tachycardia, torsades de pointes, and/or cardiac arrest). METHODS AND RESULTS: The QTd and JTd intervals in 39 children with long QT syndrome were compared to those of 50 normal age-matched children. In the long QT syndrome group, QTd measured 81 +/- 70 msec compared to 28 +/- 14 msec in the control group (P < 0.05), and JTd in the long QT syndrome group was 80 +/- 69 msec compared to 25 +/- 15 msec in the control group (P < 0.05). CONCLUSION: Children with long QT syndrome have an increased QTd and JTd when compared to normal controls. A QTd or JTd > or = 55 msec correlates with the presence of critical ventricular arrhythmias. These ECG measures of dispersion can be useful in stratifying children with the long QT syndrome who are at higher risk for developing critical ventricular arrhythmias.

Electrophysiologic properties of the atrioventricular node in pediatric patients.

OBJECTIVES: The purpose of this study was to characterize anterograde and retrograde properties of the atrioventricular (AV) node in children and to determine the presence of ventriculoatrial (VA) conduction and dual AV node pathways. BACKGROUND: Although AV node reentry is common in adults, it accounts for 13% of pediatric supraventricular tachycardia (SVT). The age-related changes in the AV node with development are poorly understood. The incidence of dual AV node pathways and VA conduction in the pediatric population is unknown. METHODS: Electrophysiologic studies were performed in 79 patients with normal hearts and no evidence of AV node arrhythmias. Patients were classified into two groups by age: group I = 49 patients (0.39 to 12.8 years old, mean [+/- SD] age 8.5 +/- 3.6); group II = 30 patients (13.4 to 20.0 years old, mean age 15.6 +/- 1.8). RESULTS: There was a significant difference (p < 0.05) in the cycle length (CL) at which anterograde AV block occurred between group I (305 +/- 63 ms) and group II (350 +/- 91 ms). Sixty-one percent of children had VA conduction with no age-related differences. There was no significant difference in the mean CL of retrograde VA block (360 ms). The incidence of dual AV node pathways in group I was 15% and 44% in group II (p < 0.05). CONCLUSIONS: These findings suggest that AV node electrophysiology undergoes maturational changes. The increase in AV node reentrant tachycardia in adults may relate to changes in the relative refractoriness and conduction of the AV node or to differences in autonomic input into the AV node that allow dual pathway physiology to progress to SVT.

Lack of cystic fibrosis transmembrane regulator-type chloride current in pediatric human atrial myocytes.

Mature cardiomyocytes have been shown to possess a cyclic AMP-mediated chloride channel (I(Cl)) which is the product of the cystic fibrosis transmembrane regulator (CFTR) gene. Species variability has been demonstrated for other ion channels. This study was designed to evaluate human I(Cl) regulation using the whole-cell patch-clamp bioassay. Atrial tissue obtained from children undergoing congenital heart surgery was enzymatically dispersed into isolated myocytes. The patients ranged in age from 1 day to 11 years (mean 2 years). Isoproterenol was used to activate the cAMP second-messenger system in a potassium-free environment. Membrane calcium and sodium channels were pharmacologically blocked. Of 20 human atrial myocytes obtained from 13 pediatric patients, 80% had a small basal chloride current. The current could be inhibited by the anion transport blocker, 9-anthracene carboxylic acid. In 4 of 20 otherwise viable myocytes, no I(Cl) could be elicited, either at baseline or with beta-adrenergic stimulation. Of the 16 myocytes with a basal I(Cl), the current was unaffected by cAMP stimulation in 15 (94%) cells. There were no significant differences in age, gender or clinical status of patients whose cells conducted Cl- current compared with patients whose myocytes had no measurable I(Cl). Ten mature guinea pig ventricular myocytes were evaluated using the same whole-cell patch-clamp technique. Seven of 10 cells showed a reversible increase in I(Cl) with isoproterenol exposure. Despite presence of the CFTR gene in human cardiomyocytes, functional expression of the cAMP-activated I(Cl) does not appear evident in isolated pediatric atrial myocytes. Whether the pathophysiology of congenital heart disease may influence chloride current modulation via alterations in adrenergic tone, intracellular Ca2+ regulation, and cellular osmotic conditions remains to be established.

Slipping rib syndrome as a cause of chest pain in children.

Four patients with the slipping rib syndrome presenting as chest pain are described, and the appropriate literature is reviewed. In two of the patients the physicians caring for the children were initially concerned that a cardiac condition was the cause of the chest pain, and a cardiac evaluation was done. In one patient an emotional cause for the pain was first considered and then a cardiac cause was pursued. In the last patient esophagitis was thought to be the cause and the child was referred to a gastroenterologist. It is suggested that slipping rib syndrome should be considered by physicians when evaluating children with a complaint of chest pain. The condition can be easily diagnosed on physical examination and therefore may save some patients from an unnecessary cardiac or gastroentestinal evaluation.