Final answer:
NSTEMI is the type of myocardial infarction without transmural involvement, where the ECG does not show ST elevation but there is evidence of cardiac muscle damage. Unlike unstable angina, which may progress to MI, NSTEMI indicates actual heart muscle damage.
Step-by-step explanation:
The type of myocardial infarction (MI) with no transmural involvement is NSTEMI (non-ST elevation myocardial infarction). Unlike STEMI (ST-elevation myocardial infarction), NSTEMI does not show the classic pattern of ST elevation on an electrocardiogram (ECG). Nonetheless, both NSTEMI and STEMI indicate substantial cardiac muscle damage due to impaired blood supply and are distinguished using ECG and blood markers. While unstable angina indicates a change in the pattern of previously stable angina or new onset of symptoms without myocardial cell death, stable angina occurs with exertion and improves with rest. It is essential to use ECG, cardiac magnetic resonance imaging, and blood tests detecting markers such as creatine kinase MB and cardiac troponin to differentiate among these conditions.