Faculty Bibliography

Dual atrioventricular nodal (DAVN) physiology has been reported in up to 63% of pediatric patients with anatomically normal hearts, yet atrioventricular nodal reentrant tachycardia (AVNRT) accounts for only 13%-16% of supraventicular tachycardia (SVT) in childhood. The incidence of AVNRT increases with age and becomes the most common form of SVT by adolescence. We investigated the age related electrophysiological responses to programmed atrial and ventricular stimulation in 14 pediatric patients who underwent intracardiac electrophysiological study prior to radiofrequency catheter ablation for AVNRT and who exhibited DAVN physiology. Single atrial and ventricular extrastimuli were placed following drive trains with cycle lengths of 400-700 ms and 350-500 ms, respectively. Six children (mean age 8.2 years, range 5.2-11.5 years) were compared to eight adolescents (mean age 16.6 years, range 13.3-20.7 years). Adolescents were found to have a significantly longer fast pathway effective refractory period (ERP) (median 375 vs 270 ms, P = 0.03), slow pathway ERP (median 270 vs 218 ms, P = 0.04), atrio-Hisian (AH) during AVNRT (median 300 vs 225 ms, P = 0.007), and AVNRT cycle length (median 350 vs 290 ms, P = 0.03). There was a strong trend for the AH measured at the fast pathway ERP to be longer in adolescents than in children (median 258 vs 198 ms, P = 0.055). The AH at the fast pathway ERP was more strongly correlated with baseline cycle length than with age (r = 0.7, P = 0.01 vs r = 0.5, P = 0.7). There was no significant difference in the retrograde VA conduction between adolescents and children. These results demonstrate an age related difference in AV nodal response to programmed atrial stimuli in pediatric patients with DAVN physiology and AVNRT. These differences are consistent with mechanisms that may explain the increased incidence of AVNRT in adolescents compared to children

BACKGROUND: Alcoholic liver disease has been associated with QT prolongation and sudden cardiac death. HYPOTHESIS: We evaluated children with hepatic failure to determine whether they have abnormalities of ventricular repolarization. METHODS: Between October 1990 and January 1996, 38 pediatric patients (mean age 6.5 +/- 7.2 years) underwent evaluation for liver transplantation, including a 12-lead electrocardiogram and an echocardiogram. All patients had normal serum electrolytes, calcium, and magnesium at the time of cardiac evaluation and were not on any medications known to prolong repolarization. Follow-up electrocardiograms were performed on all survivors with QT prolongation following liver transplantation. RESULTS: Among those evaluated, seven (18%) were noted to have a prolonged QT interval corrected for rate (QTc > 450 ms; range 460-560 ms). All had a structurally normal heart, except one with an atrial and ventricular septal defect. When compared with patients with a normal QT interval, there was no significant difference in serum indices of liver function or indication for liver transplantation. None of the patients developed a ventricular arrhythmia. Two patients with a prolonged QTc died prior to transplant and another died immediately after surgery. All four survivors had normalization of the QTc following liver transplantation. CONCLUSION: QTc prolongation can be seen in a significant number of children with hepatic failure. While the mechanism is not known, it appears to be reversible following liver transplantation

An infant with congenital junctional ectopic tachyardia required frequent hospitalizations due to tachycardia acceleration despite multiple antiarrhythmic medications. At 9 months of age, he underwent successful radiofrequency catheter ablation of the tachycardia with preservation of AV conduction

Adenosine has been demonstrated to reliably produce transient block of atrioventricular nodal (AVN) conduction, and has been advocated as a method of differentiating retrograde conduction via the atrioventricular node from accessory pathway conduction. However, the response of retrograde AVN to adenosine in patients with typical atrioventricular nodal reentry tachycardia (AVNRT) remains unclear. We evaluated 13 patients (mean age 45 +/- 20 years) with typical AVNRT prior to AVN modification. During right ventricular pacing, a rapid bolus of adenosine (0.2 mg/kg; maximum 18 mg) was administered. Adenosine sensitivity, defined by transient ventriculoatrial block, was observed in six patients, while in seven patients ventriculoatrial conduction was unaffected. An adenosine bolus administered during sinus rhythm or atrial pacing resulted in antegrade atrioventricular block in all the adenosine resistant patients in whom this was performed (n = 6). Comparisons of AVN electrophysiological characteristics between the adenosine sensitive and adenosine resistant patients were performed. There was no difference with respect to ventriculoatrial effective refractory period, ventriculoatrial Wenckebach, AVNRT cycle length, and His to atrial echo interval in AVNRT. However, there was a trend toward a longer antegrade fast pathway ERP in the adenosine sensitive group (P = 0.07). Electrophysiological properties do not predict retrograde AVN adenosine sensitivity. Adenosine does not cause retrograde AVN block in all patients with AVNRT, and therefore cannot reliably distinguish between retrograde conduction via the AVN or an accessory pathway

OBJECTIVES: The purpose of this study was to describe the functional outcome of a large number of patients after modifications of the Fontan operation and to investigate perioperative risk factors that might influence late functional state. METHODS: A comprehensive cross-sectional review of the first 500 patients undergoing a Fontan operation at our institution was undertaken. Those surviving with an intact Fontan circulation were reviewed by questionnaire to assess functional status and medication history. Medical records, chest roentgenograms, echocardiograms, cardiac catheterizations, and laboratory investigations were also reviewed to assess postoperative status. RESULTS: Three hundred sixty-three long-term survivors with an intact Fontan circulation were identified during cross-sectional follow-up. Median age at operation was 5.0 years (range 0.4 to 31 years), and median follow-up was 5.4 years (range 1.7 to 20 years). Most patients (91.1%) were in New York Heart Association class I or II. In a multivariate model, poor (class III or IV) functional state was associated with longer duration of follow-up (p < 0.001), a prior atrial septectomy (p = 0.03), and a prior main pulmonary artery-ascending aorta anastomosis (p = 0.05). CONCLUSIONS: A poor functional outcome is uncommon after the Fontan operation but becomes more frequent with increasing duration of follow-up

INTRODUCTION: The neonatal presentation of the long QT syndrome is rare, although it is frequently accompanied by life-threatening arrhythmias. Infants may not survive childhood despite traditional management with beta-adrenergic blockade and pacing. METHODS AND RESULTS: This case describes a newborn with a long QT interval, T wave alternans, intermittent 2:1 AV block, ventricular arrhythmias, and a family history of sudden death. After failing medical therapy, conventional VVI and DDD pacing were unsuccessful due to prolonged ventricular refractoriness and proarrhythmia. At 2 months of life, the child was treated with high-rate (180 ppm) atrial pacing to produce intentional 2:1 AV block. Following an episode of possible syncope at 16 months of age, an automatic implantable cardioverter defibrillator (ICD) was added. Finally, as recently reported, acutely induced hyperkalemia led to both a marked decrease in QTc and functional improvement in repolarization (consistent 1:1 AV conduction at rates to 180 beats/min). Spironolactone and dietary potassium were added and have produced the same effects chronically. CONCLUSIONS: High-rate atrial pacing with 2:1 AV block is presented as a novel and 'bridging' therapy for neonatal long QT syndrome and 2:1 AV block with ventricular arrhythmias. Definitive therapy with ICD implantation was then possible when patient size was substantially increased. The electrophysiologic response to intentional elevation of the serum potassium suggests a genetic defect in an inward potassium channel and demonstrates a possible therapy of long QT syndrome in some future patients

Between May 1990 and March 1995, 5 of 29 young patients (ages 4.2-25 years; median 14.1 years) undergoing RF ablation for atrioventricular node reentrant tachycardia (AVNRT) presented with spontaneous accelerated junctional rhythm (AJR) (CL = 500-750 ms), compared to 0 of 58 age matched controls undergoing RF ablation for a concealed AV accessory pathway (P = 0.004). In 3 of the 5 patients with AVNRT and AJR, junctional beats served as a trigger for reentry. During attempted slow pathway modification in the five patients with AVNRT and AJR, AVNRT continued to be inducible until the AJR was entirely eliminated or dramatically slowed. These 5 patients are tachycardia-free in followup (median 15 months; range 6-31 months) with only 1 of the 5 patients continuing to experience episodic AJR at rates slower than observed preablation. Episodic spontaneous AJR is statistically associated with AVNRT in young patients and can serve as a trigger for reentry. Successful modification of slow pathway conduction may be predicted by the elimination of AJR or its modulation to slower rates, suggesting that the rhythm is secondary to enhanced automaticity arising near or within the slow pathway

OBJECTIVES: Atrial flutter is a frequent, potentially fatal complication of the Fontan operation, but risk factors for its development are ill defined. We evaluated clinical features that might predict the development of atrial flutter in patients who had a Fontan operation. METHODS: We evaluated 334 early survivors of a Fontan operation done between April 1973 and July 1991 (mean follow-up, 5.0 +/- 3.8 years). Evaluation included electrocardiography, Holter monitor recordings, and chart review. Modifications of the Fontan operation included an extracardiac conduit (n = 43), an atriopulmonary anastomosis (n = 117), or a total cavopulmonary anastomosis (n = 174). Patient, time, and procedure-related variables were analyzed with respect to the development of atrial flutter. RESULTS: Atrial flutter was identified in 54 (16%) patients at a mean of 5.3 +/- 4.7 years (range 0 to 19.7 years) after Fontan operation. Atrial flutter developed sooner and was more likely to occur in patients who were older at the time of Fontan operation (12.4 +/- 7.6 vs 6.3 +/- 5.2 years; p < 0.001), had a longer follow-up interval (8.7 +/- 3.9 vs 4.4 +/- 3.4 years; p < 0.001), had a prior atrial septectomy or pulmonary artery reconstruction (p < 0.01), and had worse New York Heart Association class symptoms (p < 0.02). The presence of sinus node dysfunction was associated with a higher incidence of atrial flutter (p < 0.001). Although there was a lower prevalence of atrial flutter in those patients with a total cavopulmonary anastomosis, the follow-up for this group was shorter. Anatomic diagnoses, perioperative hemodynamics, and other previous palliative operations were not associated with an increased incidence of atrial flutter. Multivariate analysis identified age at operation, duration of follow-up, extensive atrial baffling, and type of repair as factors associated with the development of atrial flutter after Fontan operation. CONCLUSION: Atrial flutter continues to develop with time after the Fontan operation. Further follow-up is necessary to determine whether a total cavopulmonary anastomosis reduces the incidence of atrial flutter

A 4-year-old male with transposition of the great arteries, status post-Senning repair, required placement of an atrial pacemaker for sinus node dysfunction and atrial flutter. Multiple systemic venous occlusions precluded conventional transvenous lead implantation. A transhepatic approach resulted in successful placement of an endocardial atrial pacing lead

Patients with pacemakers after Fontan surgery compared favorably with nonpaced patients with respect to survival. In patients with atrioventricular block, dual chamber pacing was superior to VVI pacing