Massimo Stefano Silvetti

Atrial Threshold Variability: Implications for Automatic Atrial Stimulation Algorithms

Background: Automatic management of atrial stimulation by verification of atrial threshold (ACM) has recently been made feasible. We investigated circadian atrial threshold variability over the long term and the predictors of successful automatic atrial threshold measurement, in order to provide practical clues for programming ACM features, in such a way as to achieve daily threshold verification and > 99% effective atrial stimulation.

Paroxysmal atrioventricular block in young patients

We describe 17 patients (8 girls, and 9 boys), aged 9.6 ± 5.7 years, with paroxysmal atrioventricular block (PAVB), a condition rarely described in children. Holter monitoring documented the PAVB in 15 patients, and tilt test was performed in 4 patients (positive in 1). The electrocardiograph (ECG) was normal in 7 patients. Two patients had acquired and 11 patients had congenital heart disease (CHD). Syncope or presyncope were present in 7 patients. A normal ECG was significantly more frequent in symptomatic patients. Pauses were significantly longer in girls and in children <5 years. PAVB was recorded only during nocturnal hours in 6 patients and throughout the day in the others. The sinus rate decreased during PAVB in 6 patients and increased in 4 (generally younger girls with symptoms). Permanent pacemakers were implanted in 13 patients, including 7 asymptomatic patients with CHD and severe bradycardia. During follow-up (3.7 ± 2.5 years), 1 patient developed complete AVB. Although PAVB was still present in 91% of paced patients, symptoms did not recur because pacing prevented the pauses. In conclusion, PAVB is a rare arrhythmia. Autonomic nervous system dysfunction seems to play an etiological role and permanent pacing was an effective treatment.

Ventricular pre-excitation: symptomatic and asymptomatic children have the same potential risk of sudden cardiac death

AIMSnChildren and adolescents with ventricular pre-excitation (VPE) are at increased risk for sudden cardiac death (SCD). Although antiarrhythmic therapy and catheter ablation are well established temporary or definitive treatments for patients with Wolff-Parkinson-White (WPW) syndrome, the optimal management of children with asymptomatic VPE remains to be clearly defined. On the basis of the most recent guidelines and recommendations, the aim of this study was to determine the electrophysiological characteristics of young patients with VPE and WPW syndrome to assess and compare their potential risk of SCD.nnnMETHODS AND RESULTSnWe retrospectively investigated 124 consecutive young patients with VPE (51 with WPW syndrome and 73 asymptomatic) who underwent transoesophageal electrophysiological study. At baseline, atrioventricular reentrant tachycardia (AVRT) was induced in 13 WPW vs. 10 asymptomatic patients (25.5 vs. 13.7%, P = NS). Atrial fibrillation (AF) was induced in 13 WPW vs. 15 asymptomatic patients (25.5 vs. 20.5%, P = NS). A shortest pre-excited R-R interval (SPERRI) ≤250 ms during AF was found in four WPW vs. six asymptomatic patients (30.8 vs. 40%, P = NS). During isoproterenol infusion or stress testing, AVRT was induced in 31 of 44 WPW vs. 33 of 69 asymptomatic patients (70.4 vs. 47.8%, P = 0.018). Atrial fibrillation was induced in 12 of 44 WPW vs. 21 of 69 asymptomatic patients (27.3 vs. 30.4%, P = NS). A SPERRI ≤ 210 ms was found in 6 of 12 WPW vs. 10 of 21 asymptomatic patients (50 vs. 47.6%, P = NS). No statistically significant correlation was observed between accessory pathway location and symptoms, AVRT/AF inducibility, or mean APERP/SPERRI values.nnnCONCLUSIONnChildren and adolescents with WPW syndrome have a higher rate of AVRT inducibility than asymptomatic patients. However, no differences between the two groups were found in atrial vulnerability and parameters related to the risk of SCD.

Left ventricular pacing in neonates and infants with isolated congenital complete or advanced atrioventricular block: short- and medium-term outcome

AIMSnRight ventricular (RV) pacing may induce left ventricular (LV) dysfunction: neonates and infants with isolated congenital complete/advanced atrioventricular block (CCAVB) are at high risk of developing RV pacing-induced LV dyssynchrony, remodelling, and dysfunction. We prospectively investigated whether LV pacing results in normal LV function and good clinical status in the short/medium term.nnnMETHODS AND RESULTSnIn this single-centre, prospective study, 10 consecutive patients with CCAVB (median age 4 months, range: 0.1-16) underwent pacemaker implantation (4 VVIR, 6 DDD) using epicardial leads (on the LV apex in 8, on the LV free wall in 2). Data were collected at implantation and at 1- and 12-month follow-up. Echocardiographic evaluation included two-dimensional/three-dimensional assessment of LV dimensions, function (ejection fraction, EF), and ventricular synchrony (interventricular and intraventricular dyssynchrony). Prior to pacemaker implantation, EF was normal in six patients, 50% in two, ≤40% in two. All patients showed good clinical status and normal LV dimensions at follow-up. Patients with LV dilatation and impaired EF at implantation showed LV reverse remodelling and enhanced LV function. Normal LV function and synchrony were observed in most patients (one patient with EF 53% and three patients with mild dyssynchrony at 12-month follow-up). Paced QRS complex tended to be wider than native QRS complexes (P = 0.07); QTc duration of paced complexes was within normal limits or only slightly prolonged, without significant differences compared with QTc interval of native complexes.nnnCONCLUSIONnAt short- and medium-term follow-up, LV pacing results in satisfactory LV electromechanical function and synchrony in neonates and infants with CCAVB.

Cryoablation of AVNRT in children and adolescents: early intervention leads to a better outcome.

Currently, transcatheter cryoablation is a well‐established technique for the treatment of atrioventricular nodal reentry tachycardia (AVNRT) in children. In the past decade, many studies have focused on identifying factors that may affect acute and long‐term outcome, but none has been shown to be strongly predictive of treatment success. The aim of our study was to determine whether patient age and cryoablation method correlate with acute and long‐term success.

Cryoablation of right-sided accessory pathways in children: report of efficacy and safety after 10-year experience and follow-up

AIMSnThe aim of this study was to report the 10-year experience of our Institution in cryoablation of supraventricular tachycardia due to a right accessory pathway (AP).nnnMETHODS AND RESULTSnSeventy-one cryoablations of right AP were performed between July 2002 and October 2011 in our Institution in 66 patients (mean age 12 + 3 years, 56% males). Acute procedural success rate was 97%: 80% in patients with concealed AP and 100% in those with manifest AP (P < 0.05). Acute procedural success rate was not related to institutional experience. No permanent complication occurred. Sixteen patients had recurrences during the follow-up (18.6 ± 6.6 months; range 3-111), 13 within the first month of follow-up, 2 within the 6 months of follow-up, and 1 within 12 months of follow-up. Cox regression showed that sex, patient age, number of delivered cryo-bonus, and presence of manifest or concealed AP are not independent predictors of procedural success. Among the 16 patients with recurrences, in 10 a cryoablation redo was successful and with no further AP recurrences. The mean fluoroscopy time was 28.4 min (range 19.7-44.6) with a significant decrease (P = 0.033) in relation to the increase of the institutional experience. There were no permanent ablation-related complications.nnnCONCLUSIONnCryoablation of right-sided AP is effective and very safe in children. Better results are achieved in manifest AP. The learning curve has a real impact in the attempt to reduce the fluoroscopy time.

Long-term outcome of transvenous bipolar atrial leads implanted in children and young adults with congenital heart disease.

AIMSnAtrial leads are often implanted in paediatric patients needing a pacemaker (PM). The aim of this study is the evaluation of their outcome in young patients.nnnMETHODS AND RESULTSnWe evaluated transvenous atrial leads outcome in children and young adults from a single centre, with a retrospective analysis. A P< 0.05 was considered significant. Between 1992 and 2008, 110 patients, 75 with congenital heart defects (d-transposition of great arteries status/post, s/p, Mustard 41%, atrioventricular septal defect 11%, tetralogy 9%, ventricular septal defect 8%), aged 13.3 ± 5.3 years, underwent PM implantation with bipolar atrial transvenous leads for sinus node dysfunction (50%), atrioventricular block (38%), cardiomyopathies, and primary ventricular arrhythmias (12%). Leads are steroid-eluting (98%), tined (59%), screw-in (41%), polyurethane-insulated (72%), silicone-insulated (28%), and have been positioned by transcutaneous puncture of subclavian vein into right atrial appendage/remnant (RAA, 50%), right atrial free wall/septum (25%), left atrium (s/p Mustard, 25%). Follow-up duration is 6.4 ± 4.8 (range 0.1-18) years. At multivariate analysis, younger age at implant was a risk factor for lead failure (4 leads, 3.5%) (P= 0.03); 16 leads (14%) dislodged post-implantation and 12 were successfully repositioned, the others extracted or abandoned. Dislocation occurred more frequently with screw-in leads (P= 0.03) positioned outside RAA (P= 0.02). Atrial threshold showed a small but significant increase, 0.002 V/month (P< 0.001), impedance showed a decrease (0.6 Ω/month, P< 0.001), P-wave showed no significant difference.nnnCONCLUSIONSnTransvenous bipolar atrial leads have good long-term results in young patients, with a very low rate of lead failure. Older age at implant can further reduce this rate. Lead dislodgement is frequent in the post-operative period.

Percutaneous axillary vein approach in pediatric pacing: comparison with subclavian vein approach.

The subclavian vein approach has been used for 20 years in our center for pacemaker (PM) implantation in children, but it carries risks of hemothorax/pneumothorax and lead fracture, which could be reduced by axillary vein approach.

Voltage gradient mapping and electrophysiologically guided cryoablation in children with AVNRT

AimsnRecently, voltage gradient mapping of Kochs triangle to find low-voltage connections, or voltage bridges, corresponding to the anatomic position of the slow pathway, has been introduced as a method to ablate atrioventricular nodal reentry tachycardia (AVNRT) in children. Thus, we aimed to assess the effectiveness of voltage mapping of Kochs triangle, combined with the search for the slow potential signal in low-voltage bridges, to guide cryoablation of AVNRT in children.nnnMethods and resultsnFrom June 2015 to May 2016, 35 consecutive paediatric patients (mean age 12.1 ± 4.5 years) underwent 3D-guided cryoablation of AVNRT at our Institution. Fifteen children were enrolled as control group (mean age 14 ± 4 years). A voltage gradient mapping of Kochs triangle was obtained in all patients, showing low-voltage connections in all children with AVNRT but not in controls. Prior to performing cryoablation, we looked for the typical hump and spike electrogram, generally considered to be representative of slow pathway potential within a low-voltage bridge. In all patients the hump and spike electrogram was found inside bridges of low voltage. Focal or high-density linear lesions, extended or not, were delivered guided by low-voltage bridge visualization. Acute success rate was 100%, and no recurrence was reported at a mean follow-up of 8 ± 3 months.nnnConclusionsnVoltage gradient mapping of Kochs triangle, combined with the search for the slow potential signal in low-voltage bridges, is effective in guiding cryoablation of AVNRT in paediatric patients, with a complete acute success rate and no AVNRT recurrences at mid-term follow-up.

Comparison of cryoablation with 3D mapping versus conventional mapping for the treatment of atrioventricular re-entrant tachycardia and right-sided paraseptal accessory pathways.

UNLABELLEDnAim Transcatheter cryoablation is a well-established technique for the treatment of atrioventricular nodal re-entry tachycardia and atrioventricular re-entry tachycardia in children. Fluoroscopy or three-dimensional mapping systems can be used to perform the ablation procedure. The aim of this study was to compare the success rate of cryoablation procedures for the treatment of right septal accessory pathways and atrioventricular nodal re-entry circuits in children using conventional or three-dimensional mapping and to evaluate whether three-dimensional mapping was associated with reduced patient radiation dose compared with traditional mapping.nnnMETHODSnIn 2013, 81 children underwent transcatheter cryoablation at our institution, using conventional mapping in 41 children - 32 atrioventricular nodal re-entry tachycardia and nine atrioventricular re-entry tachycardia - and three-dimensional mapping in 40 children - 24 atrioventricular nodal re-entry tachycardia and 16 atrioventricular re-entry tachycardia.nnnRESULTSnUsing conventional mapping, the overall success rate was 78.1 and 66.7% in patients with atrioventricular nodal re-entry tachycardia or atrioventricular re-entry tachycardia, respectively. Using three-dimensional mapping, the overall success rate was 91.6 and 75%, respectively (p=ns). The use of three-dimensional mapping was associated with a reduction in cumulative air kerma and cumulative air kerma-area product of 76.4 and 67.3%, respectively (p<0.05).nnnCONCLUSIONSnThe use of three-dimensional mapping compared with the conventional fluoroscopy-guided method for cryoablation of right septal accessory pathways and atrioventricular nodal re-entry circuits in children was associated with a significant reduction in patient radiation dose without an increase in success rate.