703-4 Second Harmonic Imaging Enhances Contrast Echocardiography in Patients with Cardiac Disease: Demonstration of Feasibility

The fact that contrast microbubbles suspended in blood resonate results in the ability to alter the frequency of sound energy reflected by these targets. Therefore, preferential recording of reflected energy at frequencies which are harmonics of the carrier frequency offers the potential to selectively enhance contrast signals. We tested the clinical value of this concept during standard transthoracic echocardiography in 5 pts with organic heart disease (CAD, cardiomyopathy, other). Echo imaging was performed in the apical 4chamber view using a prototype instrument engineered to perform imaging focused about 2.5 or 5.0 megaHertz. Contrast signals were produced by injecting 3000–4000 mg of SHU508 (Levovist) into the brachial vein. For each injection, images were obtained at both 2.5 MHz and its second harmonic. Pts tolerated the injections well without change in BP or heart rate. Contrast echoes were analyzed qualitatively (1 + weak and incomplete opacification, 2+ complete LV filling, 3+ dense and complete filling) and with videointensity measurements. All pts manifested 1+ opacification during regular imaging except for one who showed no LV contrast. With 2nd harmonic imaging all pts were judged to have 2+ signals. Analysis of the ratio of LV cavity to myocardial intensity (gray levels) revealed a ratio of 0.7 ± 0.09 with regular imaging and 5.0 ± 2 with 2nd harmonics. Thus, second harmonic imaging can substantially enhance the relative signal from microbubbles as compared to tissue in patients with cardiac disease. This selective contrast amplification enables more dense and complete opacification of the LV. Second harmonic imaging should prove of value in the clinical application of contrast echocardiography