Quantitative assessment of coronary stenosis by harmonic power Doppler with a simple pulsing sequence and vasodilator stress in patients

OBJECTIVES: We examined whether myocardial contrast echocardiography (MCE) with harmonic power Doppler (HPD) employing a simple ultrasound pulsing sequence enables estimation of the severity of coronary artery stenosis in patients. BACKGROUND: Contrast intensity (CI) during MCE with intravenous microbubble infusion is dependent on the myocardial blood flow velocity (MBFV) and pulsing interval (PI). METHODS: Based on an in vitro experiment, we devised the MBFV index calculated as the reciprocal of the magnitude of CI decay produced by abrupt PI shortening during intermittent imaging. In 68 coronary artery territories from 49 patients, myocardial HPD images were acquired during intravenous infusion of Levovist, while the long PI with 1:10 electrocardiographic gating was shortened to 1:1, both at baseline and during adenosine triphosphate infusion. The MBFV index in each coronary territory and MBFV reserve as the ratio between hyperemia and baseline were compared with the severity of corresponding coronary artery stenosis assessed by quantitative coronary angiography (QCA) or by pressure guide wire as the fractional flow reserve (FFR). RESULTS: Both the MCE-derived MBFV index during hyperemia and MBFV reserve exhibited significant negative correlations with the QCA-derived stenosis severity (r = -0.56 and r = -0.64, respectively). The MBFV reserve positively correlated with FFR (r = 0.89). By combining the cutoff values of the MBFV index during hyperemia and MBFV reserve, > or =75% of stenoses defined by QCA were determined, with a sensitivity of 77.3%, specificity of 93.4%, and accuracy of 88.3%. CONCLUSIONS: Shortening of PI during intravenous MCE with intermittent HPD imaging under vasodilator stress enables assessment of coronary artery stenoses in patients.