Evaluation of microvascular angina with TIMI frame count using nitroprusside induced hyperemia.

TIMI frame count (TFC) provides a quantitative index of coronary microvascular dysfunction. Previous studies suggested the degree of frame count reserve (FCR) and slow coronary flow (SCF) correlated with microvascular dysfunction. We investigated the clinical implication of FCR and SCF for the evaluation of microvascular angina (MA). We included consecutive 77 patients with the complaint of chest pain, who subsequently had normal coronary angiography. TFC was obtained from left anterior descending artery. Intracoronary nitroprusside (15 μg) was infused to induce hyperemia, and repeat angiogram was performed after 30s. FCR was calculated by dividing basal TFC by hyperemic TFC. SCF was defined as being present when TFC was more than 28. All patients underwent a treadmill test without medication after angiography. After the treadmill test, patients were divided into a MA group (40 patients) and a control group (37 patients). FCR was similar in both groups (2.0±1.0 and 2.1±0.9, MA and control group, respectively). However, hyperemic TFC induced by nitroprusside was significantly higher in the MA group (10.9±4.7) than in the control group (9.0±3.5, p<0.05). Patients who showed SCF had a significantly greater incidence of MA (78.5%; 11/14 patients) than that with normal coronary flow (46.0%; 29/63 patients, p<0.05). The higher hyperemic TFC and presence of SCF were found to have a diagnostic value for MA.