Background and Objectives: Frame count reserve (FCR) is a simple and reliable angiographic method for the evaluation the microvascular dysfunction, and it can be easily calculated by TIMI frame count during pharmacologically induced hyperemia. Slow coronary flow (SCF) is a commonly observed phenomenon during coronary angiography and some reports showed that it is related with the nitric oxide deficiency and microvascular dysfunction. We investigated the clinical implication of FCR and SCF for the evaluation of microvascular angina.
Subjects and Methods: We included 77 patients with the complaint of chest pain and showed normal coronary angiography. After the routine angiography, intracoronary nitroprusside (15μg) was infused to induce hyperemia (nitroprusside stress test), and repeated coronary angiography was performed after 30 seconds. TIMI frame count was analyzed in left anterior descending artery and all angiograms were taken at 15 frames/s. FCR was calculated by dividing basal by hyperemic TIMI frame count. SCF was defined if the TIMI frame count was more than 28. All the patients underwent treadmill test without any medication after the coronary angiography.
Results: According to the result of treadmill test, patients were divided into microvascular angina group (40 patients) and control group (37 patients). There was no significant difference in baseline characteristics including age, sex, and cardiovascular risk factors between 2 groups. Basal TIMI frame count in microvascular angina group (21.5±11.2) was not different compared to control group (18.1±7.1). However, the hyperemic TIMI frame count after nitroprusside infusion was significantly higher in microvascular angina group (10.9±4.7) than in control group (9.0±3.5, p<0.05). FCR in microvascular angina group (2.0±1.0) was not different with control group (2.1±0.9). SCF patients had significantly higher incidence of microvascular angina (11/14 patients) compared to that in normal coronary flow (29/63 patients, p<0.05). We defined the positive result of nitroprusside stress test as a case of SCF or FCR<2. Among the microvascular angina group, 33 patients (82.5%) showed positive result of nitroprusside stress test and only 7 patients (17.5%) were negative, and it was statistically significant (p<0.01).
Conclusion: The hyperemic TIMI frame count could be a good indicator of microvascular dysfunction. The positive result of nitroprusside stress test (SCF or FCR<2) had a diagnostic value for the evaluation of microvascular angina.
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