Comparison of Normal Sinus Rhythm and Pacing Rate in Children with Minute Ventilation Single Chamber Rate Adaptive Permanent Pacemakers
ABSTRACT 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.
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ABSTRACT: The rate response of a pacemaker (PM) was compared with the sinus rate in patients during repeated exercise tests, at different settings of the rate response parameters. In patients with paroxysmal sick sinus syndrome (n=3) or atrioventricular block (n=8), a rate responsive PM was implanted. The activity-dependent pacing rate is represented by the sensor indicated rate (SIR). Each patient performed a treadmill test at 1 month, 1 year, and 2 years after implantation. Prior to the 1 and 2 year tests PM parameters were changed to produce a larger rate increase, especially at moderate levels of daily life activity. During the tests the O(2) consumption and CO(2) production were measured, breath-by-breath, to determine the workload and the anaerobic threshold. On average the workload (oxygen consumption), the patient's sinus rate, and the SIR, showed a linear increase with the workload imposed by the treadmill. In the 1 month and 1 year test the SIR was much lower than the spontaneous rhythm, especially at low or moderate workloads. On the more dynamic setting of several rate adaptive parameters at 2 years, the SIR changed significantly and was close to the spontaneous HR. The examined PM provides a paced heart rate that is proportional to the workload. For the first time the effect of reprogramming rate response parameters to produce an SIR that is similar to the sinus rate is shown in this study.Europace 02/2005; 7(1):54-9. · 2.77 Impact Factor
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ABSTRACT: Biosensors play a critical role in the real-time determination of relevant functional physiological needs. However, typical in vivo biosensors only approximate endogenous function via the measurement of surrogate signals and, therefore, may often lack a high degree of dynamic fidelity with physiological requirements. To overcome this limitation, we have developed an excitable tissue-based implantable biosensor approach, which exploits the inherent electropotential input-output relationship of cardiac myocytes to measure the physiological regulatory inputs of chronotropic demand via the detection of blood-borne signals. In this study, we report the improvement of this application through the modulation of host-biosensor communication via the enhancement of vascularization of chronotropic complexes in mice. Moreover, in an effort to further improve translational applicability as well as molecular plasticity, we have advanced this approach by employing stem cell-derived cardiac myocyte aggregates in place of whole cardiac tissue. Overall, these studies demonstrate the potential of biologically based biosensors to predict endogenous physiological dynamics and may facilitate the translation of this approach for in vivo monitoring.Journal of Applied Physiology 03/2002; 92(2):581-5. · 3.48 Impact Factor
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ABSTRACT: There are special challenges associated with the use of transvenous pacemakers in children. For example, a child's chest cavity or vascular dimensions could be too small to host the generator and leads available or required. If leads are implanted, they may stretch as the child grows. This increases the risk that the leads will later dislodge or fracture. Moreover, children requiring pacemakers often have coexisting congenital heart defects and the structural abnormalities of those could hinder easy placement of the pacing system. This article will first review the indications for permanent pacing in children and will then describe the unique challenges associated with such use.Expert Review of Cardiovascular Therapy 08/2003; 1(2):165-76.