July 1, 1997
View Full PaperAbnormal Awake Respiratory Patterns Are Common in Chronic Heart Failure and May Prevent Evaluation of Autonomic Tone by Measures of Heart Rate Variability
Key Result
Unrecognized periodic breathing or Cheyne-Stokes respiration occurred in 64% of awake chronic heart failure patients, accounting for 77% and 87% of very-low-frequency heart rate variability.
Study Design
Type
Observational (n=80)
Structured PICO
Does controlled breathing reduce VLF oscillations in heart rate variability compared to spontaneous breathing in awake patients with chronic heart failure?
P
Population
80 stable patients with mild to severe chronic heart failure in sinus rhythm, referred for consideration of transplantation
I
Intervention
Controlled breathing
C
Comparator
Spontaneous awake breathing
O
Outcome
Heart rate variability, specifically power of cardiovascular oscillations in the Very-low-frequency (VLF) spectral bandsurrogate
Abnormal respiratory patterns are common in awake heart failure patients and significantly confound heart rate variability measurements, highlighting the need to control for respiration when assessing autonomic tone.
Abstract
BACKGROUND: Reduced heart rate variability, particularly in the Very-low-frequency (VLF) spectral band, has been found to be a marker for poor prognosis in patients after myocardial infarction, but the origin of the VLF oscillations is unclear. In this study, we demonstrate that the power of cardiovascular oscillations in the VLF band in awake patients with mild to severe chronic heart failure is greatly increased by the common occurrence of unrecognized irregularity of breathing, which may confound the use of heart rate variability measures as indexes of autonomic tone or prognosis. METHODS AND RESULTS: Among 110 consecutive patients referred for consideration of transplantation, 90 were in sinus rhythm, of whom 10 were excluded as unstable. The remaining 80 patients underwent recordings of ECG, beat-to-beat arterial oxygen saturation (SaO2), and respiration during both spontaneous and controlled breathing. During spontaneous awake breathing, 64% showed periodic breathing or Cheyne-Stokes respiration (CSR), which was associated with dominant power in the VLF band of all signals. This VLF power accounted for 55%, 77%, and 87% of heart rate variability, respectively, in patients with normal breathing, periodic breathing, and CSR. It was reduced by 48% and 62%, respectively, during controlled breathing in patients with periodic breathing or CSR. Controlled ventilation also improved oxygen saturation and markedly reduced its variability. CONCLUSIONS: Breathing disorders are surprisingly common in awake patients with poor left ventricular function and produce large VLF oscillations in heart rate variability. If measures of heart rate variability are used for prognostic purposes during both short-term and long-term recordings, the confounding effects of variable respiratory patterns should be excluded. Respiratory rehabilitation might help control potentially hazardous surges in sympathetic tone.