Prevalent hypertension and stroke in the Sleep Heart Health Study: association with an ECG-derived spectrographic marker of cardiopulmonary coupling

Abstract

Study objectives: The electrocardiogram (ECG)-based sleep spectrogram generates a map of cardiopulmonary coupling based on heart rate variability and respiration derived from QRS amplitude variations. A distinct spectrographic phenotype, designated as narrow-band elevated low frequency coupling (e-LFC(NB)), has been associated with central apneas and periodic breathing and predicts sleep laboratory failure of continuous positive airway pressure therapy. This study assesses, at a population level, the associations of this spectrographic biomarker with prevalent cardiovascular disease using the Sleep Heart Health Study (SHHS)-I dataset.

Design: Retrospective analysis of the Sleep Heart Health Study-I dataset.

Setting: Laboratory for complex physiologic signals analysis.

Measurements and results: The fully-automated ECG-derived sleep spectrogram technique was applied to 5247 (of the original 6441) polysomnograms from the SHHS-I. Associations were estimated with use of various drugs and pathologies including prevalent hypertension and cardiovascular and cerebrovascular disease. Increasing with age and more common in males, e-LFC(NB) is also associated with greater severity of sleep apnea and fragmented sleep. After adjustment for potential confounders, an independent association with prevalent hypertension and stroke was found.

Conclusions: An ECG-derived spectrographic marker related to low frequency cardiopulmonary coupling is associated with greater sleep apnea severity. Whether this biomarker is solely a sign of more severe disease or whether it reflects primary alterations in sleep apnea pathophysiology (which may either cause or result from sleep apnea) is unknown. This ECG-based spectral marker is associated with a higher prevalence of hypertension and stroke.

Figure 1

Spectral characteristics of high frequency coupling, narrow and broadband elevated-low frequency coupling. High frequency coupling (short arrow), narrowband elevated-low frequency coupling (long arrow) and broadband elevated-low frequency coupling (arrow head), mapped across the whole night.

Appendix Figure 1

Sequential steps in the derivation of cardiopulmonary coupling measures.

Appendix Figure 2

Sequential steps in the detection of sleep physiology from cardiopulmonary coupling measures. HFC = High Frequency Coupling; LFC = Low Frequency Coupling; VLFC = Very Low Frequency Coupling; e-LFC = elevated-Low Frequency Coupling