RR tachogram Is fundamental tool for heart rate variability analysis that represents a plot correlation between RR intervals in msec (y axis) over a period of time or consecutive number of beats (x axis).

heart rate variability (HRV) low frequency band: is one of the items used in heart rate variability analysis, it represent the beat to beat variation of heart rate ( cyclical oscillations of heart rate ) over a low frequency band (6.7 - 25 sec) or ( 0.04-0.15 Hertz)

To understand how time unit is converted to Hertz :

frequency = number of cycles / time

frequency = 1/ time

frequency = 1/6.7 to 1/25 = 0.15 to 0.04 Hz

the low frequency band is mainly representative for the autonomic nervous system activity

RR Interval Plot - Wavy Pattern - Low-Frequency HRV: The RR interval plot refers to the time intervals between heartbeats, while the HRV (Heart Rate Variability) pattern is used as an indicator of overall health and autonomic nervous system control. The wavy pattern may indicate variability in the body's response to stress or physiological changes.

Dear Christina:

Expecting intervals of 5 mins between your X axis ticks, the frequency of HRV during the zig-zag pattern seems to be ~0.037 Hz which is below the LF band (0.05 .. 0.15 Hz). I did not yet see such slow rhythm (VLF) related to Mayer waves in healthy subjects. In the file LF_HRV you may see the typical relationship between increase in sympathetic vasomotor activity (MSNA) --> increase in blood pressure --> drop in heart rate.

On the other hand, VLF oscillations have been related to effects of medication, thermoregulation, hormones (RAAS, AVP), or central (dys)regulation. As to the latter, you may see an even slower rhythm in the file BP_HR_Parallelism. Such 'tracking of blood pressure and heart rate' is typically seen in baroreflex failure where baroreflex afferents are disrupted. However, the hypertensive patient in the figure responds to electrical baroreflex activation in a dose-dependent manner which excludes baroreflex failure.

Best regards,

Karsten

PS: I have uploaded the figures in different formats. Nevertheless, I cannot see them :-(

Karsten Heusser

Dear Karsten

Thank you very much for this informative response. This patient is in fact an immobilized white rhino and severely hypertensive (APB 180-250mmHg). The BP curve shows the same oscillations.

Oh, I missed the sort of patients you are dealing with :-)

I do not know the frequencies of cardiovascular regulation in rhinos.

Nevertheless, just out of curiosity, are BP and HR (at ~0.037 Hz) zig-zagging in parallel or antiparallel?