- During the many years of investigations into cardiac physiology, several physical parameters have been defined which are useful for studying the activity and regulation of this organ. Below we have listed these parameters and discuss their definition individually. Their role in cardiac physiology and pathophysiology can be gleaned from their interlinks
|Ventricular End Diastolic Volume|
- The Ventricular End Diastolic Volume (VEDV) is the total amount of blood within a ventricle at the end of Diastole. In other words, it is the volume of the ventricle when maximally filled, immediately prior to onset of cardiac contraction.
|Ventricular End Systolic Volume|
- The Ventricular End Systolic Volume (VESV) is the total volume of blood within a ventricle after completion of systole. Consequently, it is the volume of the ventricle when minimally filled immediately after systolic ejection of blood.
- Stroke Volume refers to the total volume of blood that is ejected by the heart in a single contraction. The stroke volume for a typical heart at rest is roughly 70mL.
- Derivation: Stroke Volume = VEDV - VESV
- The "Heart Rate" refers to the number of contractions the heart undergoes in one minute (Beats/min)
- The normal heart rate is between 60-100 beats/min
- Tachycardia is considered a heart rate above 100 beats/min whereas bradycardia is considered a heart rate below 60 beats/min
- The Cardiac Output (CO) refers to the total volume of blood ejected from the heart in one minute (ml/min). On a most basic level the Cardiac Output is a generic proxy for total cardiac function. In a resting individual the average cardiac output is roughly 5000mL/min.
- Derivation: Cardiac Output = Stroke Volume x Heart Rate
- The Ejection Fraction refers to the fraction of the VEDV which is ejected from the heart during a single contraction. The Ejection Fraction is used as a rough indicator of the heart's contractility and is typically 55% in a resting individual
- Derivation: Ejection Fraction = Stroke Volume/VEDV x 100%