Table 2 Cardiovascular measures derived from peripheral physiological data.
Feature | Definition | Interpretation |
|---|---|---|
Interbeat interval (IBI) | Time (in ms) between heartbeats (inverse of heart rate) | IBI describes how fast the heart is beating; greater IBI values indicate slower heart rate |
Respiratory sinus arrhythmia (RSA) | High frequency variability in IBI which occurs within the respiratory frequency | RSA is an estimate of parasympathetic (PNS) influence on the heart; greater RSA values indicate PNS activation |
Pre-ejection period (PEP) | Time (in ms) between the beginning of electrical stimulation of the heart and the opening of the aortic valve | PEP is an inverse estimate of cardiac contractility and sympathetic (SNS) control of the heart; greater PEP values indicate reduced contractility and SNS withdrawal |
Left ventricular ejection time (LVET) | Time (in ms) between the opening and closing of the aortic valve | LVET describes how long it takes the heart to pump out blood; greater LVET values are associated with greater blood volume |
Stroke volume (SV) | Volume (in mL) of blood ejected by the heart with each beat | SV describes blood flow; greater SV values indicate greater blood flow per heartbeat |
Cardiac output (CO) | Volume (in L) of blood circulated in the body per unit of time (m) | CO describes blood flow over time; greater CO values indicate greater blood flow |
