Rate adaptive pacemakers are used to achieve a better cardiac performance during exercise by increasing the heart rate and cardiac output. The ideal rate adaptive sensor should be able to mimic sinus node modulation under various degrees of exercise and other metabolic needs. Minute ventilation sensing has proven to be one of the most accurate sensor systems. In this study, alterations in sinus rhythm and pacing rates during daily life conditions in 11 children (median age 11 years, range 6–14 years) with minute ventilation single chamber pacemakers were investigated. Correlation of sinus rhythm with pacing rates was assessed. ECG records were obtained from 24–hour Holter monitoring. Average rates of five consecutive P waves and pace waves were determined every half hour. The average of the two values was then used to determine hourly rates. Correlation coefficients between the sinus rhythm and pacing rates were calculated. In nine patients, pacing rates correlated well to sinus rhythm (range 0.6793–0.9558. P < 0.001 and P < 0.05), whereas in two cases correlation was not sufficient (P > 0.05). Most of the patients, in whom rate response factor (RRF) measurements during peak exercise by treadmill with cnronotropic assessment exercise protocol were performed and pacemakers were programmed to these parameters, had more appropriate ventricular rates compared to spontaneous sinus rates. In these patients mean RRF value was 15.3 ± 2.7 (range 12–20, median 15). This study shows that during daily activities minute ventilation rate adaptive pacemakers can achieve pacing rates well correlated to sinus rhythm that reflects the physiological heart rate in children.
"However, typical in vivo biosensors only approximate physiological function via the measurement of surrogate signals. Such surrogatesignal estimation is a prime source of error; e.g., cardiac pacemakers that use such signals often lack a high degree of dynamic fidelity with chronotropic requirements  . A novel alternative approach is to use a biologically-based system that can sense physiological signals directly, thereby avoiding the approximation errors associated with surrogatesignal sensing. "
[Show abstract][Hide abstract] ABSTRACT: Biosensors play a critical role in the chronotropic regulation of rate-adaptive electronic pacemakers. However, typical pacemaker biosensors only approximate physiological function via the measurement of surrogate signals such as ventilation, and therefore can be poorly correlated with chronotropic requirements. Alternatively, the electropotential input-output relationship of cardiac myocytes could be exploited for long-term, reversible quantification of chronotropic demand by monitoring the inherent rate effects of blood-borne catecholamines. Previously, we demonstrated the utility of this approach using murine whole-heart pinnal allograft transplants. Here, we advance this technique by utilizing pluripotent embryonic stem cell-derived cardiac myocyte aggregates implanted in the pinnae of syngeneic murine hosts. After one week, in all of the aggregates that showed sustained electropotential activity, there was ≥70% concordance between the myocyte-aggregate rate and endogenous heart rate over the course of the trial, thereby demonstrating the ability of the cell-based biosensors to sense humoral signals and track endogenous chronotropic dynamics. Improvements in myocyte-aggregate electropotential competency, along with further advancements such as catheter-based myocyte-aggregate systems, may facilitate the incorporation of such long-term, reversible biosensors into cardiac pacemakers or other devices that require humoral substance sensing.
Engineering in Medicine and Biology Society, 2001. Proceedings of the 23rd Annual International Conference of the IEEE; 02/2001
[Show abstract][Hide abstract] ABSTRACT: 94 Patienten der Universitätsklinik für Kinderkardiologie Münster erhielten zwischen 2/80 und 10/00 einen permanenter Herzschrittmacher.. Untersucht wurden 75 Revisionseingriffe an insgesamt 166 Schrittmachersystemen. Die Patienten waren bei Erstimplantation im Durchschnitt 6,5 Jahre alt, davon 30 (32%) jünger als 18 Monate. Haupt-Revisionsursache war eine Erschöpfung des Schrittmacheraggregats in 38 Fällen (51%). Die mittlere Batteriefunktionsdauer betrug 86 (± 5) Monate. Epimyokardiale Systeme erschöpften sich durchschnittlich 32 Monate früher als transvenöse (p< 0,01). Die implantierten Elektroden funktionierten durchschnittlich 110 (± 5) Monate. Insgesamt zeigten epimyokardiale und transvenöse Systeme keinen nennenswerten Unterschied in der Funktionsdauer. Epimyokardiale Elektroden mussten vor allem wegen frühzeitigen Reizschwellenanstiegs revidiert werden, transvenöse Elektroden dagegen hauptsächlich nach Ablauf einiger Jahre wegen wachstumsbedingter Elektrodenstreckungen.
[Show abstract][Hide abstract] ABSTRACT: The choice of the optimal mode for pacing in children depends on the age of the child and the indication. Ventricular demand
pacing offers the advantage of simplicity and is ideal as a safety measure for children who have paroxysmal abnormalities.
In the rate responsive ventricular pacing mode (VVIR) the pacing rate is adjusted automatically by an additional sensor that
detects activity. Due to the potential risk of late venous thrombosis in young children, it is our policy to implant VVIR
units in children less than 20kg who have atrioventricular (AV) block and normal heart structures, and to upgrade them to
dual chamber units when the generator has to be replaced. The results of VVIR pacing are good and children have a normal level
of exercise. The atrial demand mode (AAI) is indicated in children who present with symptoms related to sinus bradycardia,
which is usually the consequence of atrial surgery. AAI pacing alone is selected when patients have satisfactory sinus acceleration
and normal AV conduction at exercise; AAIR pacing is considered in those with permanent chronotropic incompetence. As the
sinus node is the best sensor to increase the ventricular rate, atrial sensing ventricular pacemakers (DDD mode) are the best
choice for children with congenital AV block. Infants are paced by the epicardial approach and the results have been very
good in 34 patients who were operated in the last ten years. Transvenous endocardial DDD pacing is selected only in children
older than 7 years (or 20–25kg) exept for those who have complex heart malformations and need AV synchrony. Pacemakers with
mode switching algorithms should be selected in all patients who have AV block and paroxysmal atrial tachycardias. Finally,
new indications have been developed in children with atrial tachycardia, in whom atrial antitachycardia pacemakers (AAIT)
may terminate episodes of re-entry. Specific pacemaker options should be tailored to individual needs and close follow-up
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