ABSTRACT
BACKGROUND: Monitoring respiratory rate (RR) is recommended at the time of hospital presentation for acute decompensation in heart failure (HF). Device-based continuous monitoring of RR may be helpful for diagnostic and prognostic stratification after implantable cardioverter-defibrillator (ICD) implantation. This study was undertaken to analyze short- and long-term changes in ICD-measured RR and to relate RR with the patient's clinical status and the occurrence of HF events. METHODS: One hundred twenty-four consecutive HF patients who received ICD endowed with this diagnostic capability (Boston Scientific Inc., Natick, MA, USA) were prospectively enrolled. Patients were followed up for 12 months. RESULTS: At the baseline, the proportion of New York Heart Association (NYHA) class III-IV was higher among patients with daily maximum RR >27 breaths/min (third tertile) than those with <24 breaths/min (first tertile) (43 vs. 23%, p < 0.05). Moreover, the ejection fraction was lower (27 ± 7 vs. 34 ± 8%, p < 0.05). In patients with HF hospitalizations (33 events) and urgent visits for HF (15 events), the weekly average of RR calculated over the 7 days preceding hospital accesses did not differ from values recorded at the baseline and before scheduled follow-up visits. However, the weekly variation in RR (i.e., the difference between maximum and minimum values collected over the week) was significantly higher prior to hospitalization (p < 0.05). A weekly variation >3 breaths/min in maximum RR predicted an impending hospital admission for HF with sensitivity of 73 % and specificity of 57%. CONCLUSIONS: In this study, elevated values of ICD-monitored RR identified patients with worse functional status and lower systolic function. The weekly variation in RR increased before HF exacerbation. This monitoring technology may represent a useful tool in the clinical management of patients with HF.
Subject(s)
Defibrillators, Implantable , Heart Failure/physiopathology , Monitoring, Physiologic/instrumentation , Respiratory Rate/physiology , Aged , Female , Humans , Male , Prospective Studies , Sensitivity and SpecificityABSTRACT
AIMS: Control of atrioventricular (AV) node conduction by means of high-frequency stimulation (HFS) of efferent AV node vagal stimulation (AVNS) fibres enables the ventricular rate (VR) to be modulated during atrial fibrillation (AF). The aims of this study were to verify, on 18-month follow-up, the reproducibility of the dromotropic effect obtained on implantation and the long-term reliability of the system in patients who received an implantable cardioverter-defibrillator (ICD) with a standard atrial lead positioned at a location suitable for AVNS. METHODS AND RESULTS: We enrolled 12 patients with paroxysmal or persistent AF who were candidates for ICD. The right atrium was mapped to locate the pacing site, and a transvenous screw-in lead was implanted in that region. The voltages required for VR modulation (25% VR reduction) and complete AV block at different pulse durations (from 0.1 to 0.5 ms) were recorded. Eleven out of 12 patients underwent 18-month follow-up examination. Atrial pacing parameters were adequate and did not differ from the baseline values (all P > 0.05): pacing threshold 0.9 ± 0.5 V (0.5 ms pulse duration) and impedance 556 ± 121 Ω, with P-wave amplitude of 1.6 ± 0.7 mV. High-frequency stimulation induced VR modulation in nine patients and complete AV block in eight patients at pulse durations ≥0.3 ms. No differences were observed in the voltages for VR modulation and complete AV block between implantation and 18-month examination (all P > 0.100). CONCLUSION: Ventricular rate control during AF was obtained under HFS 18 months after implantation in patients with the atrial lead positioned at a location suitable for AVNS. The pacing outputs needed to achieve the dromotropic effect were comparable to those measured on implantation.
