Is it harmful for babies to have high myocardial enzymes?

When many parents take their babies with fever and cold for routine check-ups, the test reports they receive may show elevated myocardial enzymes. They then consider whether it is myocarditis and become extremely nervous. In fact, common colds and fevers can also cause elevated myocardial enzyme levels, which can return to normal after treatment.

What are cardiac enzymes?

Myocardial enzymes generally refer to biological enzymes that react to myocardial lesions. They are a general term for a variety of enzymes produced by the myocardium and present in the myocardium, generally including aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and isoenzymes, α-hydroxybutyrate dehydrogenase (α-HBDH) and creatine kinase (CK) and isoenzymes (CKMB). In China, this group of enzymes related to myocardial injury are often collectively referred to as myocardial enzyme spectrum, which has certain value in diagnosing myocardial lesions and injuries.

When the myocardium undergoes inflammatory response, myocardial enzymes will increase to varying degrees. However, cardiac enzymes are not the only enzymes that specifically respond to myocarditis and myocardial disease. Myocardial enzymes are non-specific enzymes. The main diagnostic indicator for myocarditis is not abnormal myocardial enzymes. Electrocardiogram must be one of the two main diagnostic indicators, and myocardial enzymes are secondary diagnostic indicators.

What does high myocardial enzyme mean?

Generally speaking, if the myocardial enzyme level is high, it does not necessarily mean myocarditis, because a common cold and fever will cause a temporary increase in myocardial enzyme level.

Clinical diagnosis basis of myocarditis: 1. Heart failure, cardiogenic shock or cardio-cerebral syndrome. 2. Enlarged heart (one of the manifestations in X-ray and echocardiography examinations). 3. ECG changes: ST2T changes in 2 or more main leads (I, II, aVF, V5) with R wave as the main feature, lasting for more than 4 days with dynamic changes, sinoatrial block, atrioventricular block, complete right or left bundle branch block, coupled rhythm, polymorphic, multi-source, paired or parallel premature beats, ectopic tachycardia caused by non-atrioventricular node and atrioventricular reentry, low voltage (except newborns) and abnormal Q waves. 4. CK-MB is elevated or cardiac troponin (cTnI or cTnT) is positive.

In fact, myocardial enzymes are often elevated in non-cardiac organ lesions, which are then misdiagnosed as myocarditis or myocardial damage. For example, many children with skeletal muscle diseases of the limbs, such as pseudohypertrophic muscular dystrophy, were admitted to the hospital for myocarditis because of a significant increase in myocardial enzymes found during physical examinations. In the end, it was found that the myocardium was completely normal and not myocarditis. Through muscle biopsy and other examinations, it was confirmed to be skeletal muscle disease, thus excluding myocarditis. 2. Children with pneumonia or respiratory tract infection often have a slight or significant increase in myocardial enzymes. At this time, doctors often diagnose the child as myocarditis and treat the child with intravenous infusion of fructose-6-phosphate.

In fact, any organ infection or damage can stimulate the body to show non-specific manifestations of increased myocardial enzymes. Doctors should be careful not to diagnose and treat nonspecific changes as specific problems, otherwise it will lead to misdiagnosis and incorrect treatment. Improper treatment may also lead to drug toxicity and side effects. Lactate dehydrogenase (LDH) in the myocardial enzyme spectrum is widely present in various tissues of the human body, with the highest concentrations in the myocardium, skeletal muscle, lungs, kidneys, and pancreas. Damage to any tissue in the body can cause an increase in lactate dehydrogenase (LDH), and the myocardium does not necessarily need to be damaged. Even creatine phosphokinase CK, the most sensitive and specific enzyme in the myocardial enzyme spectrum, is not unique to the myocardium, but is also present in skeletal muscle, smooth muscle, and brain tissue.

In fact, the most sensitive and specific indicator of myocardial injury is troponin, which can be troponin T or troponin I (cTnT or cTnI), which is 4 times more sensitive than CK-MB and has a specificity of 100%. If the electrocardiogram is abnormal, there are abnormal manifestations of myocarditis and elevated troponin I, myocarditis or myocardial damage should be considered. If troponin is not high, the electrocardiogram is normal, but myocardial enzymes are elevated, then myocarditis or myocardial damage cannot be diagnosed, and other causes must be sought.

In addition, the normal reference values ​​of myocardial enzyme spectrum are mostly based on adult standards, while the normal reference values ​​for children are higher than those for adults. The myocardial enzyme spectrum of most children is 2 to 3 times the normal reference value. Therefore, do not assume that a child with elevated myocardial enzyme spectrum values ​​has myocarditis. Since there are many factors that affect the myocardial enzyme spectrum, cardiac troponin should be measured to assist in the diagnosis of myocarditis.