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.