Ambulatory respiratory rate trends identify patients at higher risk of worsening heart failure in implantable cardioverter defibrillator and biventricular device recipients: a novel ambulatory parameter to optimize heart failure management

Abstract

Purpose: Respiratory distress is the primary driver for heart failure (HF) hospitalization. Implantable pacemakers and defibrillators are capable of monitoring respiratory rate (RR) in ambulatory HF patients. We investigated changes in RR prior to HF hospitalizations and its near-term risk stratification power.

Methods: NOTICE-HF was an international multi-center study. Patients were implanted with an implantable cardioverter defibrillator or cardiac resynchronization therapy defibrillator, capable of trending daily maximum, median, and minimum RR (maxRR, medRR, minRR). RR from 120 patients with 9 months of follow-up was analyzed. One-tailed Student's t test was used to compare RR values prior to HF events to baseline defined as 4 weeks prior to the events. A Cox regression model was used to calculate the hazard ratios (HR) for the 30-day HF hospitalization risk based on RR values in the preceding month.

Results: Daily maxRR, medRR, and minRR were significantly elevated prior to HF events compared to baseline (ΔmaxRR 1.8 ± 3.0; p = 0.02; ΔmedRR, 2.1 ± 2.8; p = 0.007; ΔminRR, 1.5 ± 2.1, p = 0.008). Risk of experiencing HF events within 30-days was increased if the standard deviation of medRR over the preceding month was above 1.0 br/min (HR = 12.3, 95 % confidence interval (CI) 2.57-59, p = 0.002). The risk remained high after adjusting for clinical variables that differed at enrollment.

Conclusion: Ambulatory daily respiratory rate trends may be a valuable addition to standard management for HF patients.

Fig. 1

A schematic plot of the HF risk analysis schedule. Each monthly HF event risk assessment is calculated using RR collected during a 30-day evaluation period and is compared to the number of protocol-defined HF events during a subsequent 30-day observation period

Fig. 2

Mean and SD RR during the study (for the HFE group, data between 30 days prior to and 14 days post HF events were excluded from the analysis)

Fig. 3

Respiratory rates in a patient without HF admissions. From top to bottom: daily maximum, median, and minimum respiratory rates. Thin lines with markers: daily trends; thick lines: 5-day moving averages

Fig. 4

Respiratory rates in patient with a HF admission. From top to bottom: daily maximum, median and minimum respiratory rates. Thin lines with markers: daily trends; thick lines: 5-day moving averages Dotted line indicates the day of HF admission.

Fig. 5

Changes in respiratory rate metrics prior to a HF event

Fig. 6

The results of the proportional means model of event-free time using standard deviation of respiratory rate during the evaluation periods