Analysis of heart rate variability. Background, methods, and possible use in anaesthesia

Author(s): Frey, A. W., Adt, M.

Journal/Book: Anaesthesist. 1995; 44: 175 Fifth Ave, New York, NY 10010. Springer Verlag. 677-686.

Abstract: Background and methods. Small, periodic fluctuations in heart rate are well known to physicians, the respiratory sinus arrhythmia (RSA) being the most easily detectable form of this heart rate variability (HRV). Since it is caused by changing activity of the autonomic nervous system (ANS) controlling heart rate, HRV is investigated to gain information on the functional states of the ANS. Recent developments have led to computer-aided processing of EKG signals based on time and frequency domain methods - the latter using power spectral analysis by fast Fourier or autoregressive algorithms - to exactly describe and quantify HRV. Three major regions in the frequency spectrum between 0.03 and 0.5 Hz (the suitable range for short-term recordings) have been established: (1) a region around the respiratory rate, usually between 0.2 and 0.35 Hz, called high frequency (HF), (2) a region around 0.1 Hz attributed to vasomotor activity feedback, called low (or mid-) frequency (LF), (3) a peak around 0.04-0.05 Hz correlated to thermoregulation, called very low (or low)frequency (VLF). Power spectral density of HRV is now commonly accetped as a measure of autonomic cardiovascular control activity. By studies on vagal or sympathetic blockade, the HF (or RSA) region has been attributed solely to vagal activity, while both parts of the ANS may contribute to the other two, with, however: the vagal part predominating the resting, healthy individuals. Clinical applications/anaesthesia. Thus, spectral analysis of HRV provides a measure for quantifying sympatho-vagal balance in its physiological range. Additionally, reduction of HRV along with cardiovascular disease, including hypertension, myocardial infarction, heart failure and sudden cardiac death, as well as with autonomic dysregulation, has been reported. Since is also a striking reduction produced by most anaesthetic agents, RSA and HRV are investigated as measures of anaesthetic depth. There are contradictory data on the influence of ventilation, medication, and co-existing disease on the spectrum, and thus validation of the method is still to be achieved. It has, however, been proven useful in some studies as a parameter for risk assessment of perioperative or post-infarction cardiovascular complications.

Note: Review JH Baumer, Deutsch Herzzentrum Berlin, Inst Anasthesiol, Augustenburger Pl 1, Berlin, Germany

Keyword(s): heart rate; arrhythmia, sinus; autonomic nervous system; ana; anaesthesia; RESPIRATORY SINUS ARRHYTHMIA; CORONARY-ARTERY DISEASE; ACUTE MYOCARDIAL-INFARCTION; SUSTAINED VENTRICULAR-TACHYCARDIA; BARORECEPTOR REFLEX CONTROL; FREQUENCY-DOMAIN MEASURES; SPECTRAL-ANALYSIS; BAROREFLEX SENSITIVITY; CARDIOVASCULAR CONTROL; ISOFLURANE ANESTHESIA

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