Study classed as CTIMP

Currently, Sonazoid is mainly used for imaging liver lesions by assessing perfusion characteristics. However, the ultrasound technology is the same as for cardiac imaging and the stability of the microbubbles will potentially aid the detection of myocardial perfusion defects. This study will look at the feasibility of using sonozoid in this way.

Ultrasound contrast agents are gas-filled microbubbles that enhance the visualisation of cardiac structures, function and blood flow. Myocardial contrast echocardiography enables us to visualise myocardial perfusion and provides incremental information for diagnosis of coronary artery disease (CAD) and prognosis beyond wall motion assessment .

Using ultrasound at low acoustic power (low/intermediate MI) causes the microbubbles to oscillate resulting in giving off non-linear signals which are different from tissues which gives off linear signals.

The first contrast agents were used in 1968. Since then the technology has been refined and now the microbubbles are more stable and consist of an inert gas encapsulated in a lipid or albumin shell. These microbubbles remain intact in the systemic circulation because of their small size can transit through the pulmonary circulation.

The indication for myocardial perfusion imaging is when vasodilator stress like Dipyridamole is performed. Vasodilators do not readily induce wall motion abnormalities but cause perfusion defects to occur which allows detection of CAD. Myocardial perfusion imaging is also indicated during treadmill or dobutamine stress when suspicion of CAD is high as it is more sensitive than wall motion for the detection of CAD.

Myocardial perfusion imaging looks at a uniformity of contrast appearance in the myocardium, following a continuous microbubble infusion. If there is decreased perfusion, the appearance of contrast will be delayed and the opacification will not be uniform.

The advantage of Sonazoid over the other frequently used contrast agents (Sonovue, Luminity, Optison) is that the microbubbles are more robust, allowing for a higher MI setting to be used during scanning. The higher MI setting enhances higher intensity bubble signal with improved spatial and temporal resolution which improves image quality and diagnostic accuracy.

This study is not looking for diagnosis in patients, which will be done according to standard of care. It is to evaluate whether it is possible to assess myocardial perfusion using the contrast agent Sonazoid.

Inclusion Criteria:

• Positive and normal Clinical SE
• Able to provide informed consent

Exclusion Criteria:

• Unable / unwilling to give informed consent
• Allergy to Perfluorobutane
• Egg allergy
• Patients with right to left arteriovenous cardiac or pulmonary shunt
• Unstable heart disease
• Serious pulmonary disease
• Pregnancy or lactation Women of child bearing potential (defined as not chemically or surgically sterilised or post menopausal)

10 patients will be identified for this proof of concept study.

Patients who have already had a positive clinical stress echo scan will be approached about participating in this study