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- 2D, two dimensional
- 3D, three dimensional
- AQ, acoustic quantification
- LVEF, left ventricular ejection fraction
- MRI, magnetic resonance imaging
Echocardiography has been criticised of having only moderate reproducibility and of having a low sensitivity of changes in left ventricular ejection fraction (LVEF). Inadequate endocardial visualisation during echocardiography occurs in up to 20% of cases. Although image quality has been improved with the introduction of harmonic imaging,1,2 there are still a number of studies remaining of inadequate quality, and it is here that the use of contrast agents comes into its own.3 A number of studies have now been performed looking at the effect of contrast on assessment of cardiac regional and global function. This paper reviews the current and future clinical use of ultrasound contrast agents for assessment of left ventricular function.
DEVELOPMENT OF CONTRAST AGENTS AND IMAGING TECHNIQUES
The first licensed contrast agent in the UK was Levovist (Schering, Germany) and has now been followed by Optison (Amersham, UK) and Sonovue (Bracco, Italy) which are licensed for left ventricular opacification. Although infusions are preferential for assessment of myocardial perfusion, bolus injections of agents may be satisfactory for left ventricular opacification in many cases. In tandem with the development of contrast agents have been advances in imaging modalities. The first contrast specific modalities were harmonic imaging and harmonic power Doppler, which both use a relatively high transmit power leading to bubble destruction. Optimal imaging therefore requires triggered imaging. Second harmonic imaging enhances contrast effect compared to fundamental imaging and has been used for border definition using real-time imaging.4 However, it also leads to bubble destruction and artefacts. Latest developments such as power modulation and power pulse inversion, which are low power techniques and non-destructive, allow for real-time imaging without the limitations of harmonic imaging and with less contrast. As tissue returns are not displayed, unlike with …