Myoglobin levels rise first after an MI but they also bear the risk of unspecific rises due to injuries to skeletal muscle. Because of it´s short detectability it is very useful for the diagnosis of early reinfarctions.
Troponin I and T levels, both are very specific for heart muscle, also rise earlier than CK-levels, and can be used to detect myocardial infarctions which are a few days old.
Unfortunately, all the mentioned cardiac markers need a few hours after an infarction to rise to significant levels. Thus, they cannot serve as a rationale for revascularisation therapy (lysis or PTCA).
The enzymes mentioned above show specific patterns of plasma level increase after a MI. Their levels can increase for a maximum of days, to finally decrease in various different patterns. In a reinfarction these enzyme levels show a recurrent increase.