Daily distribution of atrial arrhythmic episodes in sick sinus syndrome patients: implications for atrial arrhythmia monitoring.

AIMS: Disorders such as paroxysmal atrial fibrillation (AF) and atrial tachyarrhythmias (AT) are difficult to investigate because of their intermittent, and sometimes asymptomatic, nature. The aim of this study was to investigate the daily temporal distribution of AT/AF episodes--onset and occurrence--by analysing data from 250 pacemaker-implanted, brady-tachy syndrome patients who have been enrolled in the Burden II Study. METHODS AND RESULTS: Data were analysed accounting for the mode switch list which includes date, time, and duration of each mode switch episode. Chi-squared tests for goodness of fit were used to determine whether AT/AF episode were uniformly distributed. The population analysed in the present study suggests the occurrence of a circadian rhythm of paroxysmal AF episodes, similar to that described for other cardiovascular diseases, with clustering of events in the morning from 08:00 and (to a lesser degree) in the afternoon (03:00 to 18:00). The relative risk of AT/AF onset is 13% higher during daytime, 40% lower at night (P < 0.000001). CONCLUSION: The use of monitoring devices based on daily electrocardiogram (ECG) recording could be optimized with these data, thus increasing the probability to detect AT/AF episodes.

Management of alert messages in the remote monitoring of implantable cardioverter defibrillators and pacemakers: an Italian single-region study.

AIMS: The remote monitoring of pacemakers and implantable cardioverter defibrillators (ICDs) promotes accurate supervision of the patient and device. Alert settings appear to be a crucial parameter of its efficacy. The purpose of our study was to evaluate various settings for alerts and alert message management in patients with pacemakers and ICDs. METHODS AND RESULTS: We prospectively evaluated 282 patients (181 males, 101 females, mean age 72 ± 11 years) who were referred to nine electrophysiological centres in the Veneto region of Italy for a pacemaker (76 patients) or ICD (206 patients) implant in which remote monitoring was activated (Biotronik Home Monitoring®, Biotronik, Berlin, Germany). During a mean follow-up of 382 ± 261 days, we received 106,039 transmissions. In the pacemaker group, the alerts that were most frequently activated were those concerning battery exhaustion, surveying impedances, sensing and threshold measurements, as well as missing transmissions. In the ICD/ICD-cardiac resynchronization therapy group, the alerts nearly always activated were those concerning a detection setoff, battery exhaustion, critical values of impedance, or ineffective maximum energy shock. In both groups, the alarms for heart rate monitoring and supraventricular arrhythmia were activated in fewer cases at higher variability among centres. CONCLUSIONS: Our study demonstrates that more attention is paid to critical technical data than to patients' clinical profiles, probably to limit an excessive flow of data into the centre. Accurate alert settings, personalized to the patients' features, are essential for easier and more effective management of patients who are followed remotely.

Autonomic function during closed loop stimulation and fixed rate pacing: heart rate variability analysis from 24-hour Holter recordings.

AIM: Aim of this retrospective study was to analyze the effect of closed-loop stimulation (CLS) and DDD pacing mode on autonomic balance, and to evaluate heart rate variability (HRV) during CLS stimulation. METHODS AND MATERIALS: Autonomic balance was estimated by a 24-hour HRV analysis of paced and spontaneous beats in patients implanted with a dual-chamber pacemaker (Inos(2+) CLS-Biotronik GmbH, Berlin, Germany) and randomly assigned to CLS or DDD pacing mode. Patients underwent two 24-hour electrocardiogram Holter recordings at the end of each 3-month pacing mode period. Each Holter recording was automatically scanned to extract sequences of consecutive beats of the same type [atrial paced (Ap)-sequence and atrial spontaneous (As)-sequence], lasting at least 130 beats. RESULTS: Eight hundred and ten sequences were extracted from 15 patients, and the following spectral parameters were evaluated during both CLS and DDD mode: the total power (variance), the absolute and percentage (relative to the total power) powers of the low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) components, as well as the LF/HF power ratio. DISCUSSION: The two main findings of this study were: in all the patients, CLS seems to mimic short-term physiological HRV, although the variability (total power) was lower than that relative to the spontaneous beats; the HRV of the spontaneous beats had an higher LF/HF when the pacemaker was programmed as DDD respect to CLS, consistent with a shift toward sympathetic predominance.

Simulation of monitoring strategies for atrial arrhythmia detection.

INTRODUCTION: The current external monitoring strategies used to detect atrial fibrillation (AF) and atrial tachycardia (AT) episodes are based either on transient periods of shortterm ECG recordings or on infrequent period of long-term continuous monitoring. The aim of this study was to investigate the ability of short-term daily ECG monitoring strategies for the detection of AF events. METHODS AND MATERIALS: The investigation was based on simulations performed on data extracted from Burden II study (patients implanted with pacemaker for brady-tachy syndrome), reporting date, time and duration of each episodes. RESULTS AND CONCLUSIONS: We found that a short-term daily temporally-optimized ECG monitoring allows to detect a higher percentage of episodes than 1-day Holter monitoring and to be at least as effective as a 7-days monitoring.

Closed loop stimulation improves ejection fraction in pediatric patients with pacemaker and ventricular dysfunction.

BACKGROUND: The aim of this prospective study was to evaluate the effect of the closed loop stimulation (CLS) on the ejection fraction in pediatric patients, affected by complete atrioventricular block (CAVB) or CAVB and sinus node dysfunction (SND), with a previously implanted pacemaker (PM) and ventricular dysfunction. The role of electrical therapy in the treatment of pediatric patients with congenital atrioventricular (AV) blocks has been shown. Conventional right ventricular pacing seems to affect ventricular function. Up to now, the feasibility and the long-term results of biventricular pacing in pediatric patients were not entirely clear. METHODS: In eight pediatric patients with a previously implanted single or dual chamber PM, ventricular dysfunction, and CAVB or SND and CAVB, a dual chamber PM INOS(2+)-CLS (Biotronik GmbH, Berlin, Germany) was implanted. The effect of the physiological modulation of CLS pacing mode on the ejection fraction was evaluated by Echo-Doppler examination. Measurements were performed before the substitution of the old PM and for up to 2 years of follow-up. RESULTS: All patients showed correct electrical parameters at implantation and during follow-up. The mean value of the ejection fraction measured before the replacement of the old PM was 36 +/- 7%, while after 2 years it was 47 +/- 1% (P < 0.003). No patient showed any worsening of the ejection fraction, while only one showed no improvement. CONCLUSIONS: DDD-CLS pacing seems to improve ventricular function in pediatric patients with CAVB and/SND in spite of the use of the apical right conventional stimulation.

Effect of pacemaker rate-adaptation on 24 h beat-to-beat heart rate and blood pressure profiles.

AIMS: The aims of the study were to evaluate the 24-h beat-to-beat heart rate (RR) and blood pressure changes during closed loop stimulation (DDD-CLS) pacing and conventional fixed rate DDD pacing with respect to spontaneous activity. METHODS: We simultaneously and continuously measured beat-to-beat heart rate and blood pressure for 24 h in patients implanted with Inos2+ (Biotronik GmbH, Berlin, Germany). A randomised cross-over comparison of DDD-CLS and DDD pacing was performed by short- and long-term analyses. RESULTS: Seventeen patients (10 males, aged 46-85 years) were enroled in the study: 11 completed the protocol. The percentage of atrial stimulation was 72.87% during DDD-CLS and 38.36% in DDD (P=0.003). All patients were 100% stimulated in the ventricle. On average, the percentage increase of paced RR intervals with respect to spontaneous beats was only 7.4% in DDD-CLS but 20.1% in DDD (P=0.0001). A significant correlation between spontaneous and paced RR profiles was obtained only during DDD-CLS (r(DDD-CLS)=0.77, r(DDD)=0.23, P=0.01). Short-term analysis revealed a 3.79% reduction of the escape interval in DDD-CLS and 8.19% in DDD, and the relative fall in diastolic blood pressure was 1.14% in DDD-CLS and 3.81% in DDD. CONCLUSION: DDD-CLS provided physiological heart rate fluctuations throughout the 24-h test. The blood pressure profiles of paced and spontaneous beats were comparable. The onset of paced rhythm in DDD-CLS resulted in a less pronounced decrease in heart rate and fall in diastolic pressure than in DDD.

Effect of autonomic stressors on rate control in pacemakers using ventricular impedance signal.

The aim of this study is to evaluate the heart rate adaptation obtained by a pacemaker, based on a measure of ventricular impedance in patients undergoing autonomic challenges. The evaluation procedure was based on the analysis of the mean value (MV) and heart rate variability (HRV) of RR and systolic pressure intervals, according to a set of neurovegetative stressors (controlled respiration in supine position and during active standing; mental stress; handgrip, and noninvasive sinusoidal stimulation of carotid baroreceptors). Each test lasted 5 minutes. Fifteen chronotropic incompetent patients first implanted, were studied three months after implantation. ECG, respiration activity, and noninvasive blood pressure were monitored. HRV was evaluated by spectral analysis. Variability in the low frequency (LF) and high frequency (HF) bands was compared by computing percentage and absolute powers. We found that baseline HR was 72.2 +/- 5.5 beats/min, in mental stress was 76.8 +/- 7.8 beats/min, in handgrip was 79.2 +/- 6.3 beats/min, and in active standing was 80.9 +/- 8.6 beats/min (P < 0.01, Friedman's test). During active standing, LF component was significantly higher with respect to baseline (25.7% of total power in standing; 9.4% in baseline, P < 0.01) and it was synchronous to the LF component of the arterial pressure variability. Carotid activation/deactivation by neck suction induced synchronous changes in the paced rates. In conclusion, closed loop strategy based on ventricular contractility continuously controls heart rate by tracking the sympathetic modulation to the heart.