Rationale and objectives: The authors evaluated the potential of SonoVue, a new echo contrast agent, for the detection of myocardial perfusion abnormalities using intermittent harmonic power Doppler (IHPD) imaging and different pulse repetition frequencies (PRFs).
Methods: Experiments were performed in vitro (in a tissue-mimicking phantom) and in vivo (in minipigs) in harmonic power Doppler using an ATL HDI 3000 with second harmonic software. SonoVue was injected intravenously in an auricular vein in bolus (dose range 0.01-0.05 mL/kg) in closed-chest animals or as an infusion (rate = 0.1 mL/kg/minute) in open-chest minipigs with reversible left anterior descending coronary artery (LAD) occlusion. The animals were imaged using IHPD gated on the electrocardiogram at end-systole (pulsing interval at each cardiac cycle). The efficacy of SonoVue was evaluated at six PRFs from 500 to 6000 Hz either qualitatively using a subjective scoring system or quantitatively using a digital image analyzer.
Results: SonoVue at a dose of 0.01 mL/kg produced a strong and homogeneous myocardial opacification in IHPD. Higher doses prolonged the duration of the contrast effect. Varying the PRF allowed the discrimination of flow velocities in vitro and the detection of perfusion differences within the myocardium during transient LAD occlusion and during immediate reperfusion in vivo. Low PRFs were particularly useful to differentiate the ischemic bed from the healthy one during LAD occlusion. The high flows caused by coronary hyperemia during immediate reperfusion were detected clearly in the reperfused area at high PRFs.
Conclusions: SonoVue is a promising agent for myocardial opacification studies using IHPD. The latter imaging modality is particularly well suited for blood flow detection in tissues. Varying the PRF provides additional information on flow velocity and improves the detection of perfusion differences in the myocardium.