Background: No assessment has been made up today concerning clinical features, coronary artery flow and mid-term prognosis between acute non-ST-elevation myocardial infarction (NSTEMI) patients without epicardial coronary disease and those with epicardial coronary artery stenosis > 50% of at least one vessel.
Methods: We evaluated consecutive NSTEMI patients who had undergone coronary angiography within the first 48 hours of infarction. We examined their age, sex, smoking habits, the incidence of diabetes, dyslipidemia, hypertension, and left ventricular ejection fraction. The coronary blood flow was assessed according to the conventional TIMI flow grade and with the TIMI frame count (TFC).
Results: From October 1, 2001 to December 31, 2003, 50 patients out of 996 with NSTEMI (20 males, 30 females, mean age 60 +/- 13 years), showed normal coronary arteries (5%). This subset of patients was compared with 50 NSTEMI patients with coronary stenosis. Patients of the first group were younger and more frequently female with respect to NSTEMI patients with coronary stenosis. The differences between the two groups with respect to diabetes, hypertension, dyslipidemia incidence and ejection fraction (52 vs 47%) were not statistically significant. With the corrected TFC (cTFC) method we found a slow flow in at least one coronary vessel in a high percentage of NSTEMI patients with normal coronary arteries. When we compared normal vessels between the two groups, we found a higher cTFC in NSTEMI patients with normal coronary arteries than in NSTEMI patients with coronary stenosis. After a 16 +/- 8 months of follow-up we observed 8 events in the normal vessel group and 10 in the coronary stenosis group (p = NS).
Conclusions: The possible hypothesis of microvessel dysfunction as a pathogenesis of a slow flow in NSTEMI patients with normal coronary arteries is strong. Further studies are warranted to investigate microvessel disease and characteristics and possible causes of abnormalities. A larger perspective study with a longer follow-up is needed as well to evaluate the prognosis in this subset of patients.