Small myocardial infarction (MI) has been reported in 8 - 20% of patients undergoing percutaneous transluminal coronary angioplasty (PTCA). But neither appropriate threshold of cardiac enzyme nor useful biochemical marker for its detection has not yet been fully defined. We examined the cardiac enzyme to define more valuable biochemical marker for the detection of small MI after PTCA and to evaluate factors associated with small MI after PTCA.

This study population consisted of 209 consecutive patients who underwent PTCA. Cardiac enzyme levels were measured before and 8, 24 hours after PTCA for CK-MB, and before and 16 hours after PTCA for troponin T. We defined small MI when CK-MB levels were over 16U/L and/or troponin T levels were over 0.2 ng/ml.

Incidence of small MI after PTCA was 28/209 (13.4%) and the most of those were non-Q MI (24/28, 86%). In the detection of small MI after PTCA, the sensitivity of troponin T was higher than CK-MB (92.9% vs 39.3%). Major complications (major dissection, acute coronary occlusion, and side branch occlusion) developed significantly more in patients with small MI than in patients without small MI (p=0.002). Three independent variables, which were significantly associated with small MI after PTCA, were age, total/subtotal occlusion, and acute coronary occlusion as complication (p=0.01, p=0.02, and p=0.04, respectively).

Troponin T is more sensitive biochemical marker than CK-MB in the detection of small MI after PTCA. Major complications of angioplasty are frequently associated with small MI. Especially, age, total occlusion, and acute coronary occlusion as complication are independent factors significantly associated with small MI after PTCA.