Rate‐adapting pacing in a 7‐year‐old boy using ventricular contractility information

Abstract

Pacemaker (PM) therapy seems to be the established choice in pediatric patients with congenital complete atrioventricular block. Recent data have shown how PM therapy reduces mortality and morbidity compared with natural history data previously published, but the appropriate time for the implant is yet to be defi ned. 1 A relevant problem in pediatric patients regards the choice between single-and dual-chamber PM. In the fi rst decade the use of single-chamber, accelerometric rate-responsive PM (ventricular pacing, ventricular sensing, inhibition response, rate-adaptive; VVIR ) is an adequate and cost-effective solution: only a few VVIR patients report PM symptoms within 10 years after implantation. 2 Notwithstanding these interesting results, the benefi t of dual-chamber rate-responsive pacing (atrial and ventricular pacing, atrial and ventricular sensing, inhibition and tracking response, rate-adaptive; DDDR ), particularly in adolescents and young adults, would suggest the upgrading procedure. 3,4 This procedure involves various complications, mainly related to the choice and positioning of leads. 5,6 Newgeneration rate-responsive PM induce physiologic pacing by adapting the pacing rate upon the indirect measurement of the ventricular contractility (closed loop stimulation, CLS). Contractility is estimated by continuous sampling of the intraventricular electrical impedance obtained by a high-frequency sub-threshold pulse train. The PM records the impedance values under rest conditions (reference curve), then compares the instantaneous impedance values for each ventricular-paced beat with the reference curve: an increase of the impedance curve slope is an indication of increased contractility and this value is used to modulate the pacing rate. 7 In addition, the system updates the reference curve continuously, to adapt it to the patient's autonomic tone. 7 CLS uses conventional endocardial leads and does not require special settings. It has been shown that, in dual-chamber devices, this mode modulates the heart rate in response to various kinds of autonomic stimuli (either movement or non-movement), 8 -10 in adult and adolescent populations. Recently a single-chamber PM featuring the CLS mode has been introduced (ProtosVR-CLS, Biotronik, Berlin, Germany). A single-chamber physiologic PM, which responds to various stresses (mental or physical), may be an interesting choice for pediatric patients with congenital complete atrioventricular block: it may postpone the upgrade procedure by providing heart rate control according to the maturation of the autonomic tone. Case reportIn 1998 a 2-year-old patient was diagnosed with a congenital complete atrioventricular block confi rmed by two 24 h electrocardiogram (ECG; Holter) recordings that showed an average heart rate of 46 beats/min (range 38 -80 beats/min). In 1999 the patient was implanted with a single-chamber PM after a cyanotic episode due to fever and a heart rate lower than 30 beats/min. The endocardial lead (Capsure SP 4023-58, Medtronic, Minneapolis, MN, USA...

Physiological pacing in young patients with complex congenital heart defects

“…In 2005, our group demonstrated for the first time the efficacy of CLS to set the pacing rate very close to the spontaneous rhythm in children and late adolescents with dual‐chamber PMs, ensuring a physiological trend of R‐R intervals, without suppressing the spontaneous sinus rate . Later on, we reported on a single‐chamber ventricular CLS PM (VVI‐CLS) with physiologic modulation of pacing rate according to the autonomic tone in a pediatric patient, confirming the results obtained with CLS in dual‐chamber (DDD) pacing . In an infant, DDD‐CLS with epicardial leads was able to modulate heart rate more than accelerometer‐based DDDR pacing .…”

“…The increase in intracardiac impedance reflects a greater metabolic demand . Several studies have documented the ability of CLS to respond to movement and nonmovement stresses, both in adult and pediatric patients . In 2005, our group demonstrated for the first time the efficacy of CLS to set the pacing rate very close to the spontaneous rhythm in children and late adolescents with dual‐chamber PMs, ensuring a physiological trend of R‐R intervals, without suppressing the spontaneous sinus rate .…”

“…7 Several studies have documented the ability of CLS to respond to movement and nonmovement stresses, both in adult [5][6][7][8][9][10][11] and pediatric patients. [12][13][14][15] In 2005, our group demonstrated for the first time the efficacy of CLS to set the pacing rate very close to the spontaneous rhythm in children and late adolescents with dual-chamber PMs, ensuring a physiological trend of R-R intervals, without suppressing the spontaneous sinus rate. 12 Later on, we reported on a single-chamber the results obtained with CLS in dual-chamber (DDD) pacing.…”

“…Closed Loop Stimulation (CLS, Biotronik, Berlin, Germany) is a physiological rate‐responsive PM based on the indirect measure of ventricular contractility. Studies performed on both adult and pediatric populations have assessed the efficacy of this device for heart rate modulation in response to different stresses, and its clinical advantages in the treatment of sinus node dysfunction, atrial fibrillation, or syncope. However, no data are available on the behavior of such pacing strategy in young patients with CHD who received a single‐chamber atrial PM with CLS.…”

Physiological rate adaptation in a child with chronotropic incompetence through closed-loop stimulation using epicardial leads

“…Indeed, as already observed using endocardial leads,2, 3, 5, 6 the CLS behaves differently accordingly to the nature of the stress: the maximum heart rate value reached during handgrip is higher than that reached during the mental tests (video game playing and Stroop test).…”