Skip to Main Content


A continuous electrocardiogram, whether from a Holter recording, an intensive care unit monitor, an overnight polysomnogram, or even a short-term recording, provides a signal that can yield information about the morphology and time of onset of each heartbeat. This information, exported as a "beat file" provides the basis for multiple ways of quantifying and categorizing heart rate variability (HRV), in most cases based on intervals between normal to normal (N-N) heartbeats only. The various methods for quantifying HRV (eg, time domain, frequency domain, nonlinear) and their relationship to cardiac autonomic function have been described in multiple excellent reviews elsewhere.1-3 Less appreciated is the power of using graphical images, also derived from beat files, to obtain information about normal and abnormal cardiac autonomic function, sinus node function, and sleep-disordered breathing.


The periods between successive heartbeats can be converted to a time series of instantaneous heart rates (60,000 milliseconds in a minute/time between beats in ms). Heart rate (HR) patterns can be examined on multiple scales, each providing both unique and overlapping information. HR itself can be plotted on a beat-by-beat basis, or HR averages and ranges over longer periods can be plotted. Power spectral analysis can mathematically deconstruct heartbeat patterns into their underlying rhythmic components using fast Fourier transforms (FFTs).3 The structure of heartbeat patterns can be examined using Poincaré plots, which are plots of the interval between every pair of successive beats versus the next pair.


The current review will illustrate the types of information potentially available from these aspects of graphical HRV analysis (ie, 5-minute averaged HR patterns, hourly power spectral analysis, hourly Poincaré plots, and beat-by-beat HR tachograms). To accomplish this, we will primarily use representative plots from recordings selected from our database of subjects with and without known cardiovascular disease. From among the healthy subjects, we will examine graphical HRV in a younger adult with high HRV (the standard deviation of all normal-to-normal interbeat intervals [SDNN] = 198), an older adult with high HRV (SDNN = 167), and an older adult with low HRV (SDNN = 65). From among those with known cardiovascular disease, we will examine graphical HRV in a subject with very low HRV but normal HR patterns (SDNN = 63), a subject with periods of abnormal HR patterns (SDNN = 99), a subject with significant sleep-disordered breathing HR patterns (SDNN = 49), and a subject with atrial fibrillation (SDNN = 211).


Commercial Holter scanner reports often show plots of 5-minute averaged HR patterns. The presence or relative absence of a circadian rhythm of HR is clearly visible on these plots. Under normal circumstances, a clear decrease in HR during the night, a distinct rise in HR on awakening, and a relatively higher HR during the daytime are seen. Lack of circadian rhythm of HR is the primary determinant of low values for total HRV and suggests severe autonomic dysfunction and/or a complete lack of physical activity. In Fig. 16–1, ...

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.


About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

AccessCardiology Full Site: One-Year Subscription

Connect to the full suite of AccessCardiology content and resources including textbooks such as Hurst's the Heart and Cardiology Clinical Questions, a unique library of multimedia, including heart imaging, an integrated drug database, and more.

$595 USD
Buy Now

Pay Per View: Timed Access to all of AccessCardiology

24 Hour Subscription $34.95

Buy Now

48 Hour Subscription $54.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.