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We read the recent article by Wejner-Mik et al.1 in the Journal with great interest and we congratulate them on their study which re-emphasizes both the clinical value of myocardial contrast echocardiography (MCE) and specifically the prognostic value of dipyridamole MCE. Both real-time and triggered imaging techniques were used, highlighting the robust nature of each method. We wish to highlight certain methodological aspects which may be of use in planning future studies.

First, the contrast agent (Optison) was administered by repeated bolus injections rather than a continuous intravenous infusion. The pioneering scientific experiments that established the ability of MCE to assess myocardial blood flow (MBF) used a continuous infusion.2 The myocardial signal assessed visually as contrast intensity reflects the concentration of microbubbles within the myocardium. When the entire myocardium is fully saturated with microbubbles, the signal intensity denotes the capillary blood volume.3 Any alteration of signal must, therefore, occur predominantly from a change in capillary blood volume. Consequently, one of the basic physiological principles of MCE is that the myocardium should be fully saturated with microbubbles prior to destruction-replenishment imaging. This steady-state can be achieved with a bolus injection if the microbubbles persist for long-time periods (e.g. as with the contrast agent Imagify®, used in the recent multicentre RAMP trials).4

Issue Section:
Letters to the Editor
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