Background-Data on the results and clinical effect of an invasive risk stratification strategy in asymptomatic young patients with the Wolff-Parkinson-White electrocardiographic pattern are scarce. Methods and Results-Eighty-five consecutive patients aged <18 years with a Wolff-Parkinson-White pattern and persistent preexcitation at maximum exercise undergoing invasive risk stratification were retrospectively studied. Adverse accessory pathway (AP) properties were defined according to currently consented criteria as any of the following: shortest preexcited RR interval during atrial fibrillation/rapid atrial pacing ≤250 ms (or antegrade effective refractory period ≤250 ms if shortest preexcited RR interval was not available) or inducible atrioventricular re-entrant tachycardia. Age at evaluation was median 14.9 years. Eighty-two patients had a structurally normal heart and 3 had hypertrophic cardiomyopathy. A single manifest AP was present in 80, 1 manifest and 1 concealed AP in 4, and 2 manifest APs in 1 patient. Adverse AP properties were present in 32 of 85 patients (37.6%) at baseline and in additional 16 of 44 (36.4%) after isoproterenol. Ablation was performed in 41 of these 48 patients. Ablation was deferred in the remaining 7 for pathway proximity to the atrioventricular node. In addition, 18 of the low-risk patients were ablated based on patient/parental decision. Conclusions-Adverse AP properties at baseline were exhibited by 37.6% of the evaluated patients with an asymptomatic Wolff-Parkinson-White preexcitation persisting at peak exercise. Isoproterenol challenge yielded additional 36.4% of those tested at higher risk. Ablation was performed in a total of 69.4% of patients subjected to invasive risk stratification. (Circ Arrhythm Electrophysiol. 2014;7:218-223.)

The probability of continued epicardial pacing in children was 76% at 10 years after implantation, increased for implantation in recent years, and allowed transvenous pacing to be deferred to a significantly greater age. The use of bipolar steroid-eluting leads and of a beat-to-beat capture tracking feature significantly increased pacing system longevity and decreased the need for surgical reinterventions.

A fter repair of tetralogy of Fallot with significantly decreased exercise tolerance, a 17-year-old symptomatic boy underwent successful permanent resynchronization of a failing right ventricle (RV). The patient had surgical repair including pulmonary valvulotomy, infundibulectomy, and pericardial right ventricular outflow tract (RVOT) plasty at 1 year of age. At 3 years of age, he underwent resection of RVOT aneurysm, pulmonary valvuloplasty, and patch enlargement of the left pulmonary artery. Finally, a balloon pulmonary valvuloplasty of a mild residual pulmonary valve stenosis was performed at 17 years of age, resulting in a gradient reduction from 18 to 4 mm Hg and mild (grade I) pulmonary and tricuspid regurgitation. However, the patient continued to show significant RV dilation and systolic/diastolic dysfunction with signs of major RV dyssynchrony (right bundle-branch block; QRS duration of 200 ms and paradoxical interventricular septal motion with a late systolic right to left septal flash) by echocardiography and MRI.1 As a result of reports on successful acute subpulmonary RV resynchronization, 2-4 the patient underwent resynchronization testing in the catheterization laboratory with the aim to identify the RV pacing site associated with maximum acute increase in RV dP/ dt max (from 432 to 624 mm Hg/s) when pacing in complete fusion with spontaneous activation. One month later, an MRIcompatible permanent transvenous dual-chamber pacemaker was implanted, with ventricular pacing lead inserted as close as possible to the previously identified optimal site at the RV free wall (Figure 1), resulting in a Q-RV interval of 140 ms, proving late electric activation of this area. Atrio-ventricular delay was programmed to achieve complete fusion with spontaneous ventricular depolarization, as subsequently confirmed by 24-hour Holter ECG.Six months later, a major decrease in RV size, along with improvement in RV as well as LV function, functional class, and exercise capacity were noted (Table, Figures 2 through 6, and Movies I and II in the online-only Data Supplement). We conclude that permanent resynchronization of a failing RV is an effective method to achieve hemodynamic improvement after repair of tetralogy of Fallot. Patients with right bundle-branch block and significant RV dilation and dysfunction might be considered for this procedure in isolation or along with other indicated surgical or transcatheter interventions. RV electromechanical dyssynchrony may be, in addition to volume overload, a major factor in RV failure development. The precise role and indications for this novel treatment option remain to be studied. This is, to our knowledge, the first report of successful permanent resynchronization of a failing subpulmonary RV in congenital heart disease. Sources of Funding

Aims Fontan palliation is a surgical strategy for patients with complex congenital heart disease, in whom biventricular circulation cannot be achieved. Long‐term survival is negatively affected by the absence of sub‐pulmonary ventricle and increased systemic venous pressure. Exercise capacity is a known predictor of overall survival and quality of life in congenital heart defects. We aim to track individual trends of peak oxygen uptake (V̇O2peak) after total cavopulmonary connection (TCPC), identify predictors of deterioration, and derive a disease‐specific reference V̇O2peak dataset. Methods and results A retrospective study of serial cardiopulmonary exercise testing (CPET) data, gathered from all patients who underwent TCPC in the Czech Republic between 1992 and 2016. Of 354 consecutive patients with TCPC, 288 (81.4%) patients underwent one or more CPETs yielding 786 unique V̇O2peak values used as a reference dataset. Longitudinal data were available in 206 (58.2%) patients, who underwent a median (inter‐quartile range) of 3.0 (2.0–5.0) CPETs over a mean (standard deviation) of 8.9 (5.5) years. The decline of exercise capacity with age was linear and not faster than in healthy peers (P = 0.47), but relative values of V̇O2peak in TCPC patients were 12.6 mL/min/kg lower. Single ventricular morphology and pulmonary artery size had no significant influence on the exercise capacity dynamics. V̇O2peak decline correlated negatively with the trend of body mass index z‐score (P = 0.006) and was faster in women than men (P = 0.008). Conclusions Total cavopulmonary connection patients have significantly reduced exercise capacity. The age‐related decline paralleled the healthy population and correlated negatively with the body mass index trend. The presented V̇O2peak reference dataset may help the clinicians to grade the severity of exercise capacity impairment in individual TCPC patients.