Published Aug 4, 2003
Im a new grad on a cv surgical floor.. mostly CABG's and valves.. and lately im hearing some much about patient's EF... especially pertaining to drugs and why they are one certain drugs... please correct me if i am wrong... but i think EF stands for ejections fraction? is it force of the contraction? what exactly is EF?? why is it so important and how do you find out some ones EF...
also.. i just finished a three day class on cardiac dysrhymias but i often hear people talking about some ones QTC... what is that and why is it important and how it is measured???
THANKS FOR ANY INFO you can provide... there is soooo much to learn in cardiac!!!!!!
According to the Textbook of Critical Care Nursing (Thelan, L, and others: Chapter 11, Cardiovascular Anatomy & Physiology, p. 150; 1990, Mosby) ejection fraction is "the ratio of the stroke volume ejected from the left ventricle per beat to the volume of blood in the left ventricle at the end of diastole (left ventricular end-diastolic volume). It is expressed as a percent, normal being at least greater than 50%. Both ejection fraction and LVEDV are widely used clinically as indices of contractility and cardiac function."
Ejection fraction can be estimated through echocardiography and more precisely measured during cardiac catheterization. When you review a chart look for the cardiologist's progress note on the date the heart cath was done and you'll see the EF recorded, as well as the extent of coronary artery occlusion and valve problems. Also, look for the echo report. The EF will be recorded there. Essentially, the lower the EF, the sicker the patient. I've seen some EF's as low as 10-11% in folks with really poopy pumps.
After cardiac surgery drugs like dobutamine and epi can be used to increase heart contractility and blood flow. If the patient becomes bradycardic or junctional the epicardial pacer can be used to increase heart rate and perfusion. I assume most or all of your post-op hearts are monitored hemodynamically with a Swan-Ganz catheter. In which case all of your efforts to maximize EF would be reflected in cardiac output and cardiac index measurements.
It's getting late, so I'll leave the QTc explanation to another colleague, or if no one posts, I'll review and post in a few days.
Good luck, study hard, keep reading, don't get discouraged if you don't understand something the first time or two. Over time you will understand if you persist. I hope this helps.
Here is some relative info that may help you. The QTc is actually a corrected QT interval.
QT represents the duration of activation and recovery of the ventricular muscles. This duration varies inversely with the rate rate. Since the duration of the QT varies inversely with heart rate, the QT is not used, but rather the corrected QT is used, (QTc)
The QTc Interval is QTc= QT =1.75 ( ventricular rate - 60)
Normal QTc is approximately 0.41 seconds and tends to be slightly longer in females and increased slightly with age.
Prolonged QT can be related to Quinadine Toxicity or hypocalcemia,
Shortened QT can be from hypocalcemia.
There is alot to say on this, and more than I can explain you might want to go to some of the following for more info:
Hope this helps!!
Ejection fraction is easy. Think of your left ventricle as a ballon. When you feel the balloon up with air and the release it the air empties out. But over time if you refill and empty the balloon repeatedly the ballon becomes wore out and some of the air gets trapped inside and less in released. So if the balloon ejects all the air the ejection fraction is 100% as it get wore out the percentage gets smaller.
Now if think about your left ventricle ejecting less blood then there is less oxygenated blood making it into the circulatory system and more onoxygenated blood backing up up in the venous return system.
I hope this helps.
I think you all did a great job answering the questions.
Making nurses look as inteligent as we are
Thank YOU ALL SO MUCH!!!!!!!!!!!!!!!!!!!!!!!!!
It helps alot it really does... I am in a new grad internship program and i am sure they will cover it at some point but in the mean time i really wanted to know. I think i was confusing it with co. But correct it if i am wrong.. co is the AMOUNT of blood pumped out of the l ventricle.. whereas ef is the PERCENT of blood pumped out with each beat... ohhh and I checked the echo report of one of my patients today and it had the EF right on there (30%)... This website is awsome so much knowledge at ones fingertips... also thank for the encouragement... sometimes i feel so stupid and i do get discouraged because everyone else seems to know so much...
And if i may ask one more question... AIVR.... what exactly is it and why does know one worry much about it as long as its short and the patient is ok?
Right! CO or cardiac output is the amount of blood pumped out by the left ventricle. Normal CO is 4-6L/min (at rest). CO is calculated using the formula: Heart rate x Stroke volume. Stroke volume is the amount of blood ejected by the LV with each beat and is normally 60-70ml.
The description Noney gave of EF with the balloon analogy is excellent!
AIVR is short for Accelerated IdioVentricular Rhythym. This rhythym occurs when the SA or sinoatrial node, which is normally the main pacemaker of the heart, looses control of pacing and the heart is paced from the ventricles for a time at a normal rate. (Normal rate being 60 to 100 beats a minute.) On a rhythym strip you may see Normal Sinus Rhythym (NSR) and then a run of what appears to be Premature Ventricular Contractions (PVCs) and then a return to NSR after a period of time. You can tell a beat originating from the ventricles because the QRS duration is > .12 seconds if you measure it out with calipers. The rhythym is called accelerated idioventricular because the ventricles normally pace the heart at 20-40 beats/min if the two higher pacemakers in the heart fail. (The two higher pacemakers are the SA node which sends an impulse 60-100 times/min; then the AtrioVentricular node which sends an impulse at 40-60 times/min if the SA node fails.)
The reason no one gets excited about this arrhythmia is because the patient is usually hemodynamically stable. This means his blood pressure is normal or normal for him.
renerian, BSN, RN
excellent responses! renerian
Ok I think i understand!!!! THANK YOU!!!
One thing I noticed reading responses.... EF is never 100 %. It does not start at 100 % and decrease. The highest I've ever seen recorded was 68 %....and that was considered "perfect" by the cardiologists. So, when 68 is normal and perfect, the 33 % takes on a different interpretation. The pt has lost about 1/2 of his push as compared to 2/3 if 100 were the max.
Theoretically, EF can be 100 %. Though, after 17 years in the cath lab, I've never seen such. However, in some patients, the LV cavity will nearly obliterate. These cases would be those patients with LVH, and/or a hyper-dynamic ventricle. I have seen patients with an EF of >75%. This is atypical.
Luvbabies, I would encourage you to spend some time in the cath lab. After observing several caths, it will all make more sense to you. I have never met any cath lab staff that wasn't eager to share their knowledge and experience, not to mention show off their cath lab!
moonshadeau, ADN, BSN, MSN, RN, APN, NP, CNS
We use the QT/QTc in determing dosing for TIkosyn a chemical cardiac antiarrythmic. Tikosyn works by prolonging the QT in an attempt to help convert a patient from Fib/Flutter to NSR. WHen the QT becomes too long, it can lead to torsades. Very scary drug once you see what it can do. But it does work for some.
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