Last time we talked about how the IBI series is transformed from the time-domain to a frequency-domain representation. This is done to isolate specific frequency ranges of variability. One of the frequency bands, named the High Frequency (HF) band, is influenced predominantly by a phenomenon known as respiratory sinus arrhythmia. […]

## All About HRV Part 3: Frequency Domain Analysis

Last time we talked about the IBI series and how it is built from the detected R peaks on the ECG signal. Time-domain HRV statistics can be derived directly from the IBI series, but further processing is needed to extract specific frequencies of beat-to-beat variation. Most notable of these frequencies […]

## All About HRV Part 2: Interbeat Intervals and Time Domain Stats

Now that we have laid a basis for what HRV is and what signals are necessary for studying it, we need to talk about the process by which important statistics are calculated. It all starts by building something called the IBI series. IBI Series If HRV is the study of […]

## All About HRV Part 1: Introduction to Heart Rate Variability

All About Heart Rate Variability Heart Rate Variability, or HRV for short, is the measure of variation in timing between successive heart beats. It has been shown that heart rate and HRV are regulated by both the sympathetic (SNS) and parasympathetic (PSNS) branches of the autonomic nervous system (ANS). Only […]

## All About Cardiac Impedance Part 6: Deriving Respiration

Select analysis version to view the applicable content: For our final entry in the series on cardiac impedance, we are going to step back from analyzing the impedance signal directly and examine another way in which it can be used – to provide an index of respiration. Why this […]

## All About Cardiac Impedance Part 5: Data Editing

Select analysis version to view the applicable content: Now that we have talked about meaningful statistics in impedance cardiography and how they are calculated, we need to take a step back and make sure the data are clean and free of artifact. There are two steps for editing in impedance cardiography – […]

## All About Cardiac Impedance Part 4: Systolic Time Intervals & More

Welcome back to the series on Cardiac Impedance. This time, we will use the key points identified last time on the dZ/dt ensemble average to determine important systolic time intervals (PEP, LVET) which will lead directly into additional cardiac indices of interest (stroke volume, cardiac output, total peripheral resistance) calculated […]

## All About Cardiac Impedance Part 3: dZ/dt Component Identification

Select analysis version to view the applicable content: Last time we talked about how an entire segment of data is distilled down to an average representation of the cardiac cycle using ensemble averaging. Using the ensemble average, three landmarks are identified on the dZ/dt waveform: B, Z, and X. All three […]

## All About Cardiac Impedance Part 2: Ensemble Averaging

Last time we introduced the following depiction of the dZ/dt signal: What we are looking at here is a single cycle of dZ/dt. In the IMP Analysis application, we distill a series of cardiac cycles down to a single average cycle for a given time period. It is from this average waveform […]

## All About Cardiac Impedance Part 1: Introduction to Cardiac Impedance

All About Cardiac Impedance Cardiac impedance is a measurement of the mechanical activation of the heart. By recording cardiac impedance in conjunction with the electrical activation of the heart, the electrocardiogram (ECG), we can gain insight into sympathetic nervous system influence through measures such as Pre-Ejection Period, Stroke Volume, and Cardiac […]