CKMB ratio

EricTAMUCC-BSN, BSN, RN · Feb 14, 2005

I believe the ratio you are referring to is the CK to CKMB ratio. In theory you don't want the cardiac isoenzymes / the MB markers greater than 4% or 7 U/l of the total creatine kinase (CK) (normal CKMM is 96 to 100% or 174 U/l). CKMM is released natuarlly from skeletal muscles and contributes to the majority of isoenzymes released. According to researchers the brain and the majority of non cardiac organs contribute very little to the total amount of isoenzymes released.

Therefore you are left with skeletal versus cardiac or CK (MM) to CKMB ratio.

What should it be to indicate non-MI and when do we begin to suspect MI ?

Any CKMB less than 4% of the CK is considered "non-MI" while anything greater than that might cause you to investigate Troponin.

I have had patients with normal Troponin but elevated CK and CKMB but because the "ratio" was OK they were sent to the floor.

According to AACN, troponin is a specific part of the myocardial cell's contractile apparatus. Your physician may have felt comfortable with the patient's clinical status without an elevated troponin.

Hope this was helpful.

cpeubob · Feb 14, 2005

I appreciate your response and I don't want to appear clueless but :

CK = 290 CKMB = 7.30 ratio = ? is it as simple as 290 divided by 7.30 ?

We don't get elevated Troponins on the floor they go to the unit, we also don't get EKG changes on the floor. I just want to have a clear understanding of this ratio information to be able to demonstrate more competence.

UM Review RN, ASN, RN · Feb 14, 2005

I appreciate your response and I don't want to appear clueless but :

CK = 290 CKMB = 7.30 ratio = ? is it as simple as 290 divided by 7.30 ?

We don't get elevated Troponins on the floor they go to the unit, we also don't get EKG changes on the floor. I just want to have a clear understanding of this ratio information to be able to demonstrate more competence.

Gee, I may need some education myself here, but usually when I see a normal trop and an elevated CKMB, my first thought is that the patient has either fallen or done a lot of coughing in the past few days.

I'm not sure I understand what the significance of the CK to CKMB ratio is. All of our patients are ordered "Cardiac enzymes q8h X3" which includes the CK, CKMB, and troponin, so I guess I don't understand the question.

But I'm certainly willing to learn anything new. :)

cpeubob · Feb 15, 2005

Angie O

I am aware of a fall etc causing the CK to elevate, but as I understand it (and this is what I am searching for) if the ratio is above/below a certain number it will indicate cardiac vs. non-cardiac. I am fully aware of the greater significance of Troponin as an indicator of MI, but as you replied your institution also does enzymes (CK, CKMB, and Troponin I assume) so there is obviously some significance in the CK and CKMB or we would only do Troponin. I think the importance lies in the CK - CKMB ratio, and therein lies my quest. :confused: . I work in a chest pain unit (in case you didn't guess that by my name :lol2: ) and feel if I have this tidbit of knowledge maybe I can better benefit one patient.

EricTAMUCC-BSN, BSN, RN · Feb 15, 2005

Almost, if your CK is 290 and your CKMB is 7.3 than your ratio will be 7.3/290= 0.03 * 100= 3%

Now you teach me something

I appreciate your response and I don't want to appear clueless but :

CK = 290 CKMB = 7.30 ratio = ? is it as simple as 290 divided by 7.30 ?

We don't get elevated Troponins on the floor they go to the unit, we also don't get EKG changes on the floor. I just want to have a clear understanding of this ratio information to be able to demonstrate more competence.

UM Review RN, ASN, RN · Feb 15, 2005

OK Folks, I think I've got it--and thanks for the question that led me to search, because I did learn something interesting and valuable.

An excerpt from CK-MB, The Test:

http://www.labtestsonline.org/understanding/analytes/ckmb/test.html

CK-MB levels, along with total CK, are tested in persons who have chest pain to diagnose whether they have had a heart attack. Since a high total CK could indicate damage to either the heart or other muscles, a high CK-MB suggests that the damage was to heart muscle. If your doctor thinks you have had a heart attack and gives you a "clot-busting" drug (called a thrombolytic), CK-MB can help your doctor tell if the drug worked. When the clot is broken open, CK-MB tends to rise and fall faster. By measuring CK-MB in blood several times, your doctor can usually tell whether the drug has worked.

...If the ratio of CK-MB to total CK (relative index) is more than 2.5-3, the heart is the likely muscle damaged. A high CK with a very low relative index suggests that other muscles were damaged.

...Severe injury to skeletal muscle can be significant enough to raise CK-MB levels above normal, but such injury doesn't usually cause a high relative index. If your doctor suspects injury to both heart muscle and skeletal muscle, it may be hard to detect heart injury. Then your doctor may need to order other tests (such as troponin).

...Sometimes persons who are having trouble breathing have to use their chest muscles. Chest muscles have more CK-MB than other muscles, which would raise the amount of CK-MB in the blood.

...Persons whose kidneys have failed can also have high CK-MB levels without having had a heart attack. Rarely, chronic muscle disease, low thyroid hormone levels, and alcohol abuse can increase CK-MB, producing changes similar to those seen in a heart attack.

cpeubob · Feb 16, 2005

OK OK lets see if I have this right ..........CK - 290 CKMB - 7.3 so 100 = 3%, now that is 100 is the CK(290) and the 3% is the CKMB(7.3) hope I am right so far ? according to Angi O's info this is the upper limit for non-cardiac, have I managed to pull all this together or are the waters so muddy now we are all afraid to swim? As a side note they called me and ask me to come in today because the nurses working were "freaking" out about running a dobutrex drip, so of course I went in, and happen to speak with one of the cardioliogist and ask him about the formula for the CK - CKMB ratio, first he smiled then said he didn't know it off the top of his head - THE PLOT THICKENS LOL LOL LOL

ethelbsnrn · Feb 16, 2005

Why not order CK and Trop I only? CK to check if skeletal muscles are injured amd Trop I to see if cardiac muscles are involved. What is ckmb-ck ratio for?

cpeubob · Feb 16, 2005

I spoke with lab today and it's all clear now. CK - 290, CKMB - 7.3 then to find the relative index CKMB divided by CK and multiply that answer by 100, that then becomes a percent. So 7.3(CKMB) divided by 290(CK) is 0.0251724, now multiply that by 100 which is 2.51724 or 2.5%, which is my facilitys cut off for cardiac vs. noncardiac.

Why not just CK and Troponin ? This is just a guess but figuring the ratio is an additional tool to use to determine the cause of the elevation.

ethelbsnrn · Feb 16, 2005

With the formula above, it is just actually figuring-out what part (in percentage) of total CK is the MB isoenzyme ...simply, 7.3 (MB) is 2.5% of 290 (CPK).

If Trop I is more specific to the heart and would tell you that cardiac muscles were involved, why do we need to know the CKMB and the ratio? Would CPK and Trop I enough?

ethelbsnrn · Feb 16, 2005

As I read the previous posts re: cardiac enzymes , I figured-out the answer to my aboved-question. The Trop I will be elevated for as long as 8 days, so we need to check the CKMB with the ratio to see if the patient is having another / a new cardiac muscle injury. What do you think?