Andrew D. Blaufox

A Cross-Sectional Study of Exercise Performance During the First 2 Decades of Life After the Fontan Operation

OBJECTIVES The aim of this study was to describe exercise performance during the first 2 decades of life in Fontan survivors by a cross-sectional study and to identify factors that influence exercise performance. BACKGROUND Exercise performance after the Fontan procedure is reduced relative to performance in healthy subjects. Data on pre-adolescents are limited, and the patterns of exercise performance in different ages are unexplored. METHODS Ramp cycle ergometry was performed with expired gas. Data were analyzed for the entire study population and for subpopulations that did and did not achieve a maximal aerobic capacity. RESULTS Of 411 subjects tested (12.4 +/- 3.2 years of age), 166 achieved a maximal aerobic capacity. Peak oxygen consumption (VO(2)) was 26.3 ml/kg/min (65% of predicted for age and gender [% predicted]) for the entire population and was lower in the submaximal capacity subgroup compared with the maximal capacity subgroup (63% predicted and 67% predicted, respectively; p = 0.02). Oxygen consumption at ventilatory anaerobic threshold (VAT) was better preserved (78% predicted for the total population) than peak VO(2). Higher % predicted O(2) pulse at peak exercise was associated with greater % predicted peak VO(2), work rate, and VAT. Adolescence and male gender were associated with decreased % predicted peak VO(2). The relationship between echocardiographic indexes of ventricular function and exercise function was surprisingly weak. CONCLUSIONS In Fontan patients, maximal aerobic capacity is reduced compared with healthy subjects, with better preservation of submaximal performance. Higher O(2) pulse is associated with better exercise performance, whereas adolescence and male gender are associated with decreased performance compared with healthy subjects.

Arrhythmias in a contemporary fontan cohort: prevalence and clinical associations in a multicenter cross-sectional study.

OBJECTIVES Our aim was to examine the prevalence of arrhythmias and identify independent associations of time to arrhythmia development. BACKGROUND Since introduction of the Fontan operation in 1971, long-term results have steadily improved with newer modifications. However, atrial arrhythmias are frequent and contribute to ongoing morbidity and mortality. Data are lacking regarding the prevalence of arrhythmias and risk factors for their development in the current era. METHODS The Pediatric Heart Network Fontan Cross-Sectional study evaluated data from 7 centers, with 520 patients age 6 to 18 years (mean 8.6 +/- 3.4 years after the Fontan operation), including echocardiograms, electrocardiograms, exercise testing, parent-reported Child Health Questionnaire (CHQ) results, and medical history. RESULTS Supraventricular tachycardias were present in 9.4% of patients. Intra-atrial re-entrant tachycardia (IART) was present in 7.3% (32 of 520). The hazard of IART decreased until 4 to 6 years post-Fontan, and then increased with age thereafter. Cardiac anatomy and resting heart rate (including marked bradycardia) were not associated with IART. We identified 3 independent associations of time to occurrence of IART: lower CHQ physical summary score (p < 0.001); predominant rhythm (p = 0.002; highest risk with paced rhythm), and type of Fontan operation (p = 0.037; highest risk with atriopulmonary connection). Time to IART did not differ between patients with lateral tunnel and extracardiac conduit types of Fontan repair. Ventricular tachycardia was noted in 3.5% of patients. CONCLUSIONS Overall prevalence of IART was lower in this cohort (7.3%) than previously reported. Lower functional status, an atriopulmonary connection, and paced rhythm were determined to be independently associated with development of IART after Fontan. (Relationship Between Functional Health Status and Ventricular Performance After Fontan-Pediatric Heart Network; NCT00132782).

Acute Kidney Injury After Surgery for Congenital Heart Disease

BACKGROUND The RIFLE criteria (risk, injury, failure, loss, and end-stage kidney disease) have been used to assess acute kidney injury (AKI) in various populations of critically ill children. There are limited reports of AKI using RIFLE criteria in large pediatric populations undergoing congenital heart disease surgery. METHODS Records of patients 18 years and younger who underwent surgery for congenital heart disease between January 2006 and November 2009 were reviewed. The RIFLE score was determined for each patient postoperatively. Multivariate logistic regression analyses were performed to determine risk factors for AKI and the association with clinical outcomes, with subanalyses of patients 1 month of age or younger. RESULTS Data for 458 patients (median age, 7.6 months) were collected and analyzed. Evidence of AKI was demonstrated in 234 patients (51%), the vast majority of whom recovered within 48 hours. Younger age, higher RACHS-1 (risk-adjusted classification for congenital heart surgery) category, and longer cardiopulmonary bypass time were associated with development of AKI. Acute kidney injury was associated with longer duration of ventilation and lengths of intensive care unit and hospital stay. Incidence of AKI in patients 1 month of age or younger was 60.9%, of which more than half required greater than 72 hours to recover. In patients 1 month of age or younger, use of cardiopulmonary bypass, lower preoperative serum creatinine, and higher preoperative blood urea nitrogen were associated with AKI, and AKI was the only factor associated with longer intensive care unit and hospital lengths of stay. CONCLUSIONS Incidence of AKI based on RIFLE criteria in patients undergoing congenital heart disease surgery is higher than previously reported. Risk factors include age 1 month or younger and use of cardiopulmonary bypass. Acute kidney injury is associated with longer lengths of stay.

Functional status, heart rate, and rhythm abnormalities in 521 Fontan patients 6 to 18 years of age

OBJECTIVES Our objective was to determine the relationship between functional outcome and abnormalities of heart rate and rhythm after the Fontan operation. METHODS The National Heart, Lung, and Blood Institute Pediatric Heart Network conducted a cross-sectional analysis of patients who had undergone a Fontan procedure at the 7 network centers. Analysis was based on 521 patients with an electrocardiogram (n = 509) and/or bicycle exercise test (n = 404). The Child Health Questionnaire parent report and the oxygen consumption at the anaerobic threshold were used as markers of functional outcome. RESULTS Various Fontan procedures had been performed: intracardiac lateral tunnel (59%), atriopulmonary connection (14%), extracardiac later tunnel (13%), and extracardiac conduit (11%). Prior volume unloading surgery was performed in 389 patients: bidirectional Glenn (70%) and hemi-Fontan (26%). A history of atrial tachycardia was noted in 9.6% of patients and 13.1% of patients had a pacemaker. Lower resting heart rate and higher peak heart rate were each weakly associated with better functional status, as defined by higher anaerobic threshold (R = -0.18, P = .004, and R = 0.16, P = .007, respectively) and higher Child Health scores for physical functioning (R = -0.18, P < .001, and R = 0.17, P = .002, respectively). Higher anaerobic threshold was also independently associated with younger age and an abnormal P-axis. Resting bradycardia was not associated with anaerobic threshold or Child Health scores. CONCLUSIONS In pediatric patients (6-18 years) after the Fontan procedure, a lower resting heart rate and a higher peak heart rate are each independently associated with better physical function as measured by anaerobic threshold and Child Health scores. However, these correlations are weak, suggesting that other, nonrhythm and nonrate, factors may have a greater impact on the functional outcome of pediatric patients after the Fontan operation.

Radiofrequency catheter ablation in small children: Relationship of complications to application dose

Little data exists to support the use of procedural modifications during radiofrequency catheter ablation (RFCA) in small children. A single institution database was reviewed for patients under 15 kg undergoing RFCA from January 1998 to August 2001. Of 268 RFCA procedures, 18 were done in 14 patients under 15 kg (median weight 5.7 kg, 3.5–13.7; age 5.8 months, 1.2–19.8). Six patients had normal hearts, 4 had congenital heart disease, and 4 patients had cardiomyopathy. Diagnoses were orthodromic reciprocating tachycardia (ORT) in nine patients/nine studies, chaotic atrial tachycardia (CAT) in one patient/two studies, and VT in four patients/seven studies. RFCA variables included maximum temperature (69°C, 50–78), total applications (10, 2–21), applications > 20 seconds (5, 0–15), and total application time (331 s, 26–1,006 s). Complications were pericardial effusion in 1 patient, mild mitral regurgitation in 1, and myocardial infarction in 1 patient. When indexed for weight, the number of applications with a duration > 20 seconds in the ORT group was significantly greater in complicated versus uncomplicated procedures (0.7 applications/kg vs 0.16 applications/kg, P = 0.05). In addition, for the ORT subgroup, the indexed total application time trended higher in complicated versus uncomplicated procedures (40.6 s/kg, vs 6.6 s/kg, P = 0.1). RFCA success was 9/9 in ORT, 6/7 in VT, and 0/2 in CAT. RFCA can be successful in small children; however, complications appear to be related to RF dose indexed for body size. Thus, the decision to proceed with RFCA, and the application duration and number should be guided by patient size, balanced against the risks of the arrhythmia, and reserved for dire circumstances. (PACE 2004; 27:224–229)

Acute Coronary Artery Stenosis During Slow Pathway Ablation for Atrioventricular Nodal Reentrant Tachycardia in a Child

Coronary injury during radiofrequency ablation is a rare but potentially life‐threatening complication that has been reported for attempted elimination of accessory pathways. This is the first report of coronary artery injury during slow pathway ablation for AV nodal reentrant tachycardia. Manifest signs of injury may be transient or nonexistent and easily missed. Controlled studies are needed to determine the true risk of coronary artery injury during radiofrequency ablation for supraventricular tachycardia, particularly in small children. (J Cardiovasc Electrophysiol, Vol. 15, pp. 97‐100, January 2004)

Complete Occlusion of the Left Circumflex Coronary Artery After Radiofrequency Catheter Ablation in an Infant

Radiofrequency catheter ablation of a left lateral accessory atrioventricular pathway was performed in a 5‐week‐old infant with drug‐refractory supraventricular tachycardia. Energy application via a 5‐French mapping and ablation catheter in the temperature‐controlled mode (60°C, 30 W) at the atrial aspect of the mitral valve annulus repeatedly resulted in termination of the tachycardia by conduction block within the pathway. Tachycardia remained inducible subsequently. After a safety energy application during sinus rhythm, significant ST‐segment elevation in the inferior, mid precordial, and left lateral leads was noted. Selective left coronary angiography revealed complete occlusion of the circumflex coronary artery. Moderate‐to‐severe mitral valve regurgitation developed, finally requiring mitral valve replacement. (J Cardiovasc Electrophysiol, Vol. 14, pp. 1004‐1006, September 2003)

The Study of Antiarrhythmic Medications in Infancy (SAMIS) A Multicenter, Randomized Controlled Trial Comparing the Efficacy and Safety of Digoxin Versus Propranolol for Prophylaxis of Supraventricular Tachycardia in Infants

Background—Supraventricular tachycardia (SVT) is one of the most common conditions requiring emergent cardiac care in children, yet its management has never been subjected to a randomized controlled clinical trial. The purpose of this study was to compare the efficacy and safety of the 2 most commonly used medications for antiarrhythmic prophylaxis of SVT in infants: digoxin and propranolol. Methods and Results—This was a randomized, double-blind, multicenter study of infants <4 months with SVT (atrioventricular reciprocating tachycardia or atrioventricular nodal reentrant tachycardia), excluding Wolff-Parkinson-White, comparing digoxin with propranolol. The primary end point was recurrence of SVT requiring medical intervention. Time to recurrence and adverse events were secondary outcomes. Sixty-one patients completed the study, 27 randomized to digoxin and 34 to propranolol. SVT recurred in 19% of patients on digoxin and 31% of patients on propranolol (P=0.25). No first recurrence occurred after 110 days of treatment. The 6-month recurrence-free status was 79% for patients on digoxin and 67% for patients on propranolol (P=0.34), and there were no first recurrences in either group between 6 and 12 months. There were no deaths and no serious adverse events related to study medication. Conclusions—There was no difference in SVT recurrence in infants treated with digoxin versus propranolol. The current standard practice may be treating infants longer than required and indicates the need for a placebo-controlled trial. Clinical Trial Registration Information—http://clinicaltrials.gov; NCT-00390546.

Catheter Tip Cooling during radiofrequency ablation of intra-atrial reentry: Effects on power, temperature, and impedance

Catheter Tip Cooling. Introduction: Cooling the catheter tip either passively with increased tip size or actively during radiofrequency catheter ablation (RFCA) has been shown in canine thigh preparations to create larger lesions than standard catheter tips, yielding a theoretical advantage for improving the outcome of RFCA for intra‐atrial reentrant tachycardia (IART).

Fascicular and Nonfascicular Left Ventricular Tachycardias in the Young: An International Multicenter Study

The aim of this study was to evaluate the clinical presentation and outcomes of pediatric patients with ventricular tachycardia (VT) originating from left heart structures.