ejection fraction

[bmart100]

what is the ejection fraction and what part of the heart is affected?

[kenkeith]

I understand, and you are not wrong with your reference to the math but it is not very accurate in terms efficacy...my info is fine tuning :) You are referring to a procedure that is identical to fraction shortening (subtracting dimensions of chambers before and after heart cycle and dividing by dimension after diastole times 100).  Those dimensions do not refer to "volume"etc. and at best it is a very poor method for an estimate.  Also, with MVR the EF can appear to be efficient with normal EF, and with DD (dystolic dysfunction) the heart is pumping efficiently (normal EF range) but the cardiac output is lower than normal and can cause heart failure if not properly treated.

Q: "Not ALL the blood is pumped out of the ventricles with each heart beat, it would take too long for them to refill".

The amount of blood pumped with normal heart function and no abnormality (good health), the amount of blood pumped with each stroke is a compensating factor to maintain a balance of blood flow between the left and right side of the heart along with HR and BP.. When the heart normally dilates (EF stays within the normal range) that increases the cardiac output (stronger contractions) and visa versa. An EF of 100% is not possible because when the EF is greater than 70% the diagnoses would be the heart LV is beginning to overcompensate and dilating excessively would result in a pathologically enlarged left ventricle (damage the myocite heart cells...loss of elasticity and realignment)  to the extent EF would drop into the heart failure range.  There would be heart failure well before a 100% EF.

Thanks for your comments.

[ed34]

It isn't 'my' method, it's how EF is calculated.

End diastolic - end systolic = stroke volume. The percentage is calculated from these.

You are simply looking for efficiency, then if the EF is low, you look for the cause. So I really don't understand the point you are making.

[kenkeith]

Does that explanation and take into account MVR.  If 50% is left in the ventricle after the stroke, that doesn't mean 50% goes into circulation is that part of your consideration?. How does your method account for MVR?

[ed34]

Not ALL the blood is pumped out of the ventricles with each heart beat, it would take too long for them to refill. The ejection fraction is the amount of blood in one of the ventricles before it pumps, less the amount left behind after it has pumped. This is the amount which has left the heart for its journey around the vessels. This figure is then turned into a percentage.
As an exaggerated example, let's say you had 1 litre in your left ventricle before it pumped, so its full up and ready to go. It then squeezes and you have half a litre remaining. This means half a litre was ejected from the heart, making it 50%. So the ejection fraction of the left ventricle would be 50% or usually written as LVEF 50%.

[kenkeith]

The ejection fraction is the percent of blood pumped with each heartbeat.  Normal is 50 to 70%.  The left ventricle (pumping chamber) is the siginificant chamber, and the heart walls that are not impaired with heart cell damage will have the contractility to pump effectively to meet the oxygen/blood demand of the system.  

Heart cells can be damaged and affect the heart's contractility and that will reduce the heart's ability, and the usual cause for heart cell damage is occluded vessels, heart muscle disease, heart impaired structually that reduces cardiac output.

Thanks for your question,  Take care,

Ken