On a normal working day, a child's mother came to me to open a liver function test, and she told me: "The last time the child entered the kindergarten for physical examination, there was an examination index that was a little higher than the normal value, and the kindergarten teacher asked for a review. ”
I opened the child's test records more than twenty days ago, when the child checked four hepatic functions: aspartate aminotransferase (AST): 41 IU/L (reference range: 15-40), and the other three: alanine aminotransferase, total protein, albumin are normal.
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Case after
While opening the test form for the parents to review, I thought to myself: "The AST value is a little higher, the clinical significance is really not big, the kindergarten teacher is really competitive enough, and I have to see the normal results before stopping." ”
Although I think so in my heart, but out of serious and responsible professional habits, when I handed the test form to the child's mother, I did not forget to advise: "After the test results of the review come out, you take it to the doctor to see it, if you do not have time to go to the hospital, you will upload the results to my online clinic, and I will take the time to help you see it." ”
After 1 day, the parents uploaded the results of four liver function tests for the re-examination, AST: 45 IU/L, and the remaining three items were still normal.
Seeing the results of this test, I began to feel a little wrong, AST is always a little higher, but Alanine transaminases (ALT) is normal, it is likely not liver function abnormalities, does the child have myocardial damage? I instructed parents to quickly bring their children to the hospital for follow-up consultation, planning to check the heart muscle enzyme spectrum for their children, and the parents happily agreed.
Knowledge Links:
AST, also known as aspartate aminotransferase, is mainly distributed in the heart muscle, followed by tissues such as the liver, skeletal muscle, and kidneys. Normally, the AST content in the serum is low, but when the corresponding cells are damaged, the cell membrane permeability increases, and the AST in the cytoplasm is released into the blood, so its serum concentration can be increased, and it is generally used as an auxiliary examination index for myocardial infarction and myocarditis.
The next day, the parents brought the child to the hospital, I carefully inquired about the child's situation, the child has had an upper respiratory tract infection in the past three weeks, but there has been no discomfort recently, eating and playing are normal. In the child's subsequent examination, no abnormalities were found. I then arranged for my child to have a blood draw and checked myocardial enzyme profile and myocardial infarction.
At noon, the laboratory doctor called the nurse's station furiously to report the critical value: the abnormal increase in creatine kinase isoenzyme (CK-MB). Looking closely at his test sheet, it was found that the myocardial enzyme profile was generally elevated, and it seemed that the child did have myocardial damage.
Next, we arranged for the child to have an electrocardiogram and a heart ultrasound. Finally, combining the results, although the child has myocardial damage, but fortunately did not meet the clinical diagnostic criteria for myocarditis, so I prescribed a nutritional myocardial drug to take home for oral administration, and instructed parents to take some precautions, asking them to come to the hospital regularly for review, and see a doctor at any time when the condition changes.
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Those enzymes in the myocardial enzyme profile
One of the most diagnostic indicators in myocardial enzyme profile is the creatine kinase isoenzyme (CK-MB), as it is specific for myocardium, which is mainly derived from damaged cardiomyocytes.
Myocardial injury releases a variety of other enzymes at the same time, including lactate dehydrogenase (LDH), α-hydroxybutyrate dehydrogenase (α-HBDH), creatine kinase (CK), and AST. Therefore, if only CK-MB is elevated without other enzymes, there is not necessarily myocardial damage and myocarditis; conversely, only other enzymes are elevated, and CK-MB is normal, which does not support myocarditis, because these enzymes can also be derived from skeletal muscle and many other tissues such as the liver.
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Trivia of different indicators
CK、CK-MB
CK and CK-MB rise early and short duration, so it is an early diagnostic indicator of myocardial damage.
In addition, the CK-MB (quality) test is more accurate than the CK-MB (active), and most tertiary hospitals have carried out this testing program. In children with mildly elevated CK-MB, CK-MB (mass) and troponin (cTnI) tests may be used to aid diagnosis.
LDH、α-HBDH
LDH is a nonspecific cardiomyosome that is also found in the cytoplasm and mitochondria of tissue cells such as liver, skeletal muscle, and red blood cells.
Α-HBDH, which is mainly derived from the heart muscle, has a large molecular weight and can rise for 2 weeks or more when the heart muscle is damaged. Therefore, α-HBDH testing is necessary for patients with late presentation, prolonged treatment, and inconspicuous clinical signs and ECG presentation.
The current reference value of myocardial enzymes used in clinical practice is the adult standard, and the data show that the level of myocardial enzymes in children is higher than that of adults. The elevation of myocardial enzymes is related to a variety of reasons, not only organic lesions can cause elevation, exercise, tension, etc. can also cause elevation, but its ratio is not affected by this factor. When the myocardium is damaged, there is a certain variation in its ratio.
CK-MB/CK and α-HBDH/LDH can be used as indicators that children are not affected by age and exercise factors. Therefore, some scholars have shown that in the diagnosis of myocarditis in children, CK-MB/CK, α-HBDH/LDH and cTnI are good combined diagnostic indicators.
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Diagnosis of myocarditis is a clinical challenge
Myocarditis is clinically and pathologically defined as an inflammatory disease whose lesion range is mainly limited to the myocardium, caused by a variety of pathogens (viruses, bacteria, spirochetes, protozoa, etc.), allergies or autoimmune diseases.
In myocarditis, viral myocarditis is the most common, and pathogens include enteroviruses (especially coxsackievirus group B), adenovirus, influenza virus, Epstein-Barr virus, cytomegalovirus, and parvovirus B19.
Given that the clinical manifestations of myocarditis vary greatly (from the absence of obvious symptoms or mild clinical symptoms to shock, heart failure, and even sudden death), and the pathological diagnosis (endocardial myocardial biopsy) is not widely used in the clinic, the diagnosis of myocarditis has always been a clinical challenge.
1. For the abnormal indicators of the test results, even if there is only a little abnormality, the doctor needs to have the spirit of "dying to the end", thinking, pondering and exploring more, so as not to miss the diagnosis and misdiagnosis;