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.