Assessment of Autonomic Function in Cardiovascular Disease

Abstract

Certain abnormalities of autonomic function in the setting of structural cardiovascular disease have been associated with an adverse prognosis. Various markers of autonomic activity have received increased attention as methods for identifying patients at risk for sudden death. Both the sympathetic and the parasympathetic limbs can be characterized by tonic levels of activity, which are modulated by, and respond reflexively to, physiological changes. Heart rate provides an index of the net effects of autonomic tone on the sinus node, and carries prognostic significance. Heart rate variability, though related to heart rate, assesses modulation of autonomic control of heart rate and carries additional prognostic information, which in some cases is more powerful than heart rate alone. Heart rate recovery after exercise represents the changes in autonomic tone that occur immediately after cessation of exercise. This index has also been shown to have prognostic significance. Autonomic evaluation during exercise and recovery may be important prognostically, because these are high-risk periods for sudden death, and the autonomic changes that occur with exercise could modulate this high risk. These markers provide related, but not redundant information about different aspects of autonomic effects on the sinus node.

Are Changes in Heart Rate Variability in Middle‐Aged and Older People Normative or Caused by Pathological Conditions? Findings From a Large Population‐Based Longitudinal Cohort Study

“…Frequency‐domain components were computed by integrating the power spectrum within 2 frequency bands: 0.04 to 0.15 Hz (low‐frequency power [ms 2 ]) and 0.15 to 0.4 Hz (high‐frequency power [ms 2 ]). Low‐frequency power (low‐frequency HRV [LF‐HRV]) reflects both parasympathetic and sympathetic HR modulations; high frequency (high‐frequency HRV [HF‐HRV]) is an index of parasympathetic modulation of HR 4, 5. In addition, we used LF‐HRV in normalized units (LFnu [%]), which was computed as LF/(LF+HF).…”

“…To avoid redundancy, the HF‐HRV in normalized units, being equal to 100% minus LFnu (%), was not analyzed. These ratio‐based HRV measures have been proposed as indices of sympathovagal balance 4, 5…”

“…Specifically, increased sympathetic and/or decreased parasympathetic activity has been associated with increased risk for a number of cardiac outcomes such as sudden cardiac death, heart failure, ventricular arrhythmias, or hypertension 2, 3. Heart rate variability (HRV) is a valid noninvasive technique for estimating the characteristics of the autonomic nervous system and for quantifying modulation of the sympathetic and parasympathetic inputs 4, 5. Decreased HRV has been linked to increased mortality in cardiac patients6, 7 and increased risk of coronary heart disease and cardiac mortality in general populations 8, 9.…”

Effect of exercise on cardiac autonomic function in females with rheumatoid arthritis

“…The techniques used for the evaluation of HRV from RR-interval data sets were grouped into three categories: time domain, frequency domain and non-linear analysis (Poincarè plot analysis) [29,31]. As there is no gold standard for HRV measurements and no method has been identified as being superior to another, it was decided to use all three techniques as they are complementary to each other [32]. Time domain indicators that were determined included RR interval (the mean of the intervals between successive QRS complexes) and SDRR (the standard deviation of intervals between successive QRS complexes) representing vagal and sympathetic influence, i.e.…”

Measurement fidelity of heart rate variability signal processing: The devil is in the details

“…Frequency-domain variables are based on spectral analysis of RR intervals (Lahiri et al, 2008). Power spectral density decomposes RR intervals into their fundamental frequency components and provides information on the distribution of power as a function of frequency.…”