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.

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.