ECG HRV

Question 1

What is the HRV theory?

Answer 1

Analysis of the variability in R-R intervals in the ECG, can indicate imbalances between sympathetic and vagal influences on the heart.

Question 2

How can HRV be studied? (4)

Answer 2

• Mathematical modeling of heart rate regulatory systems
• Non-linear methods for determining indices for regulatory functions
• Time domain methods to determine the deviation of successive R-R
intervals
• Spectral domain methods to determine the power spectral density of
definitive frequency components of the ECG.

Question 3

What is happening in the HRV lab? What does the analysis involve?

Answer 3

• In this lab, a power spectral analysis (PSA) of the HRV of a subject will be
determined from the subject’s ECG.
• The analysis involves the mathematical transformation of the ECG record
to yield its power spectrum and the analysis of the spectrum to determine
the density of defined frequency ranges in the spectrum.

Question 4

What are the four components of the HRV power spectrum based on frequency range?

Answer 4

• ULP is the power density number for the ultra low frequency range (<0.003Hz)
–> Prognosis of sudden cardiac death taken from 24 hour ECG recordings is highly accurate.
• VLP is the power density number for the very low frequency range (0.003-0.04Hz),
–> Thought to be connected to thermoregulation, the renin-angiotensin system, and changes in physical
activity.
• LP is the power density number for the low frequency range (0.04-0.15Hz)
–> Generated mainly by sympathetic activity. Baroreceptor modulation is a major component of LP power.
• HP is the power of the high frequency range (0.15-0.40Hz)
–> Derived from vagal activity which is modulated by respiration.

Question 5

What is LF and HF and what does the LF/HF ratio represent and what does the ratio assess?

Answer 5

Since LF represents mainly sympathetic activity and HF represents
vagal activity, their ratio (HRV ratio) is a good indicator of
sympathetic-vagal balance.
• This ratio is used to assess the balance of the autonomic nervous
system in various diseases.

Question 6

What are the three experiments in the ECG and HRV Lab and what are their aims?

Answer 6

EX 1: ECG and Pulse in a Resting Subject
–> AIM: To measure and correlate the ECG and pulse in a resting individual.
EX 2: The ECG and Pulse After Leg Exercises
–> AIM: To measure and correlate the ECG and the pulse immediately after exercise.
EX 3: Heart Rate Variability in a Resting Subject
–> AIM: To determine heart rate variability in a resting individual.