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The Frank–Starling law of the heart (also known as Starling's law and the Frank–Starling mechanism) represents the relationship between stroke volume and end diastolic volume. [1] The law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction (the end ...
The stroke volume is affected by changes in preload, afterload, and inotropy (contractility). In normal hearts, the SV is not strongly influenced by afterload, whereas, in failing hearts, the SV is highly sensitive to afterload changes. Stroke volume relative to EDV is Ejection Fraction.
However, the relationship is not simple because of the restriction of the term preload to single myocytes. Preload can still be approximated by the inexpensive echocardiographic measurement end-diastolic volume or EDV. Preload increases with exercise (slightly), increasing blood volume (as in edema, excessive blood transfusion (overtransfusion ...
In cardiovascular physiology, stroke volume (SV) is the volume of blood pumped from the ventricle per beat. Stroke volume is calculated using measurements of ventricle volumes from an echocardiogram and subtracting the volume of the blood in the ventricle at the end of a beat (called end-systolic volume [note 1]) from the volume of blood just prior to the beat (called end-diastolic volume).
The right ventricular end-diastolic volume (RVEDV) ranges between 100 and 160 mL. [5] The right ventricular end-diastolic volume index (RVEDVI) is calculated by RVEDV/BSA and ranges between 60 and 100 mL/m 2. [5]
This allows the heart to cope with the required cardiac output at a relatively low right atrial pressure. We get what is known as a family of cardiac function curves, as the heart rate increases before the plateau is reached, and without the RAP having to rise dramatically to stretch the heart more and get the Starling effect. [citation needed]
Many of the factors that regulate the heart rate also affect cardiac function by altering the stroke volume. While a number of variables are involved, stroke volume is dependent upon the difference between end diastolic volume and end systolic volume. The three primary factors involved are preload, afterload and contractility. [1]
V is volume; α is the alpha factor. The value is between 0 and 1 but closer to 1. As can be inferred from the above formula, if the alpha factor is not taken into account, the calculated volume is an underestimate. ρ specific resistance of blood; L distance between pair of electrodes; G measured conductance; G P parallel conductance