Final answer:
The concentration of LDH1, an isoenzyme form of lactate dehydrogenase, peaks for about 6 days following a myocardial infarction before declining. Elevated LDH levels, along with markers like creatine phosphokinase and cardiac troponin, assist in diagnosing heart damage.
Step-by-step explanation:
After a myocardial infarction (MI), the isoenzyme form of lactate dehydrogenase (LDH), particularly LDH1, shows an increase in plasma concentration. This elevated LDH is maintained at peak levels for about 6 days following the heart attack, before it starts to decline. LDH, which catalyzes the conversion of lactate to pyruvate, is a cytosolic enzyme released from damaged cells and can act as a marker for tissue damage and cell viability. The elevation of LDH, along with other markers like creatine phosphokinase (CPK) and cardiac troponin, helps in diagnosing an MI, which can also be confirmed with an ECG, echocardiography, or cardiac magnetic resonance imaging.
CPK is another important enzyme whose levels increase rapidly in the plasma following a heart attack. The concentration of CPK is greatly elevated (up to 10 times the normal level) after the first attack and can increase significantly more with subsequent attacks. Detection of elevated levels of specific enzymes like CPK and LDH1 can confirm heart damage, and these are part of common blood tests employed when diagnosing an MI.