Continuous Respiratory Rate is Superior to Routine Outpatient Dyspnea Assessment for Predicting Heart Failure Events

Introduction Dyspnea is a common complaint in patients hospitalized for heart failure (HF). Implantable medical devices are capable of monitoring and calculating a respiratory rate trend (RRT) using transthoracic impedance. We compared RRT to routine outpatient dyspnea assessment in identifying patients risk of acute HF events (HFEs) between follow-up (FU) visits. Methods The MultiSENSE study enrolled 900 HF patients with COGNIS TM CRT-Ds followed for up to 1 year. HFE including hospitalizations or outpatient administration of IV decongestive medications were independently adjudicated. Scheduled FU occurred every 6-8 weeks unless remotely monitored which allowed 3 months between FU. Dyspnea status and the daily RRT were evaluated at each FU. RRT was compared to dyspnea assessment in identifying patients risk of HFE in the next FU period. Dyspnea assessment was discrete with two grades (with or without dyspnea), RRT was a continuous value represented in breath per minute (bpm). Results During 4635 FU periods, 135 HFEs occurred. The hazard ratio (HR) for a HFE was 2.0 (95% confidence interval: 1.4-3.0) times higher for patients with dyspnea compared to those without. The HR for RRT was similar using a threshold of 18 bpm, 2.1 (95% CI: 1.4-3.0). RRT thresholds above 18 bpm provided successively higher HR (figure below), significantly higher than that of dyspnea. Conclusion In ambulatory HF patients, an RRT was able to stratify the risk of a HFE beyond what dyspnea status could do. RRT was able to determine patients with up to 10-fold higher risk of a HFE in the next FU period. The use of automatic, device measured, objective respiration measurements in ambulatory patients may improve the ability for clinicians to identify patients at risk for HFE.