The Investigation of the Ischemic Response in the Patients with Coronary Slow Flow by Atrial Pacing

Pathophysiology of the chest pain is not precisely known yet in patients who does not have fixed coronary lesion but slow coronary flow by angiography. In this study, our aim is to display metabolic ischemia via atrial pacing to determine the difference of lactate production and arteriovenous oxygen content (AVO2). The 34 patients with slow coronary artery flow detected by coronary angiography via TIMI "frame count" method were included. All patients underwent myocardial perfusion tomography. Resting and stress images were recorded. Lactate extraction and AVO2 content values determined before and after atrial pacing. Patients were classified according to their response. Twenty-eight patients (18 male, 10 female, mean age 54.42±9.61) (Group I) did not have metabolic ischemia while 6 patients (4 male, 2 female, mean age 60±5.76) (Group II) showed evidences of metabolic ischemia. There was not significant increase in AVO2 content after pacing (57.37±2.05, 57.96±2.65; p<0.061) in Group I. Statistically significant difference were found in Group II (58.23±2.1, 68.35±2.15; p<0.028). Comparison of AVO2 contents showed that there was not significant difference in basal values (p<0.43) but levels after pacing were significant (p<0.001). Lactate extraction rates before and after pacing decreased in two groups (0.24±0.10, 0.15±0.15; p<0.028 and 0.23±0.18, -0.471±0.27; p<0.01). Reduction was more prominent in Grup II. Basal lactate extraction were similar in both groups, but significant decrease in Group II after atrial pacing were found (p<0.0001). Metabolic ischemia was not ascertain in 82.4% of patients in this study group. Positive perfusion scintigraphy rate was 83.3% in patients with proven metabolic ischemia. Our data confirmed that chest pain was not originated from myocardial ischemia in significant number of patients with slow coronary flow. We concluded that perfussion sintigraphy is reliable and accurate method for determination of ischemia in this group of patients.