ABSTRACT
BACKGROUND: A collateral flow can be assessed and graded by coronary angiography, however, the technique does not provide any information about perfusion. Myocardial contrast echocardiography (MCE) can assess collateral perfusion and has superior spatial resolution in defining its distribution. OBJECTIVE: To investigate the difference of transmural perfusion according to the angiographical collateral grade in normal myocardium, we performed MCE of collateral artery in 16 patients (m : f = 11 : 5, age: 57+/-13yrs.) with angina and compared the results with the angiographical grades. METHODS: In six patients with preexisting collaterals on baseline angiography, we performed MCE after intracoronary injection of sonicated Hexabrix. For 10 patients without preexisting collaterals on baseline angiography, we performed angiography, MCE for recruited collateral arteries during balloon inflation of stenotic coronary arteries (2 times for 120sec.). For 12 patients who underwent PTCA, we performed pressure wire simultaneously with angiography and MCE for recruited collateral arteries during balloon inflation. Fractional collateral flow(FCF) was defined by the ratio of coronary wedge pressure to proximal pressure(Pw/Pa). Angiographical collaterals were graded according to 'Rentrop' criteria(grade 0-3). Transmural thickness (TMT) and enhanced myocardial thickness (EMT) of an enhanced segment on MCE were measured at diastolic phase. The depth of collateral perfusion was estimated by collateral perfusion index (CPI) that was the ratio of EMT to TMT. RESULTS: There were significant differences of CPI with respect to angiographical grades according to one way ANOVA test (p< 0.05). One of five patients who had no recruited collaterals showed partial enhancement confined to the epicardium with CPI of 0.24. There was significant correlation between the angiographical grade and the CPI with Spearman's Rho value of 0.93(p< 0.0001). The angiographical grades were significantly correlated with FCF with the Spearman's Rho value of 0.87(p=0.0002). There was also significant correlation between FCF and CPI with Pearson's r=0.81 (p=0.0016). CONCLUSION: The higher the angiographical collateral grade is, the higher the collateral pressure and the deeper the fractional transmural perfusion from epicardium into endocardium gets.