Table 1 Factors affecting the information transmission from ECG R wave to PPG pulse wave
From: Pulse rate variability: a new biomarker, not a surrogate for heart rate variability
Physiological measure | Anatomical location | Conversion of physical property | Modulators | |
|---|---|---|---|---|
Direct | Indirect | |||
ECG R wave ↓ | Left ventricular muscle | Electric excitation ↓ | Intraventricular conduction, ventricular activation time, electromechanical coupling | Myocardial ischemia, heart diseases |
Pre-ejection period ↓ | Left ventricle | Muscle force ↓ | Preload and after-load, contractility, aortic diastolic pressure | Respiration, blood pressure, body position and exercise, heart failure (alternating pulse) |
Aortic pressure elevation ↓ | Aorta | Pressure impulse ↓ | Stroke volume, aortic dynamic compliance, intrathoracic pressure | Respiration, peripheral resistance |
Pulse conduction time ↓ | Artery | Pressure wave ↓ | Internal radius, wall thickness and elasticity, blood density | Vasomotor sympathetic activity, endothelial function, blood pressure |
Tissue volume ↓ | Tissue microvasculature | Blood volume ↓ | Vascular dynamic compliance, blood flow, venous pressure | Location and body position, body and environmental temperature |
PPG pulse wave | Red cell hemoglobin | Light intensity | Absorption, scattering, reflection, and transmission; vascular bed volume | Local red cell count, hemoglobin content, waveform fiducial point |