Final answer:
It is true that serum cardiac biomarkers need to be measured several times after admission if a myocardial infarction (MI) is suspected but remains uncertain. These biomarkers, especially creatine kinase MB and cardiac troponin, are key indicators of heart muscle damage.
Step-by-step explanation:
The statement is True. If the diagnosis (DX) of myocardial infarction (MI) remains uncertain, serum cardiac biomarkers should indeed be measured on admission, at 6-9 hours after admission, and again after 12-14 hours. Serum cardiac biomarkers, such as the creatine kinase MB isoenzyme (CK-MB) and cardiac troponin, are crucial for diagnosing an MI. CK-MB and cardiac troponin levels rise when cardiac muscle is damaged during an MI. CK-MB maintains elevated levels in the plasma for about 1-2 days post-MI, while cardiac troponins can remain elevated for a longer duration, providing a diagnostic window for detecting myocardial injury.
Furthermore, other enzymes like lactate dehydrogenase (LDH), specifically the LDH₁ isoenzyme, also increase and peak in plasma during an MI and can remain at high levels for up to 6 days following the event. Consequently, serial measurements of these markers are used to help confirm the diagnosis of an MI, particularly in ambiguous cases where the electrocardiogram (ECG) might not provide a definitive diagnosis, as seen with non-ST-elevation MI (non-STEMI).