P477The use of high frequency ultrasound imaging to detect and quantify the local effects of intramyocardial injections for cardiac regenerative therapy

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Purpose: Injection of multiple volumes of cells into the myocardium in the context of cardiac regenerative therapy can give rise to local myocardial damage. Quantification of this damage by means of clinically available imaging techniques is difficult. Alterative imaging techniques can specifically quantify this damage and gain insight into the effects of the injections and ultimately into the effects of the therapy. We used high frequency ultrasound to detect the locations of injection, and calculate local tissue deformation.Methods: Data acquisition was done epicardially prior to termination in 5 pigs with 4 to 12 weeks old myocardial infarctions. Four weeks after infarction the pigs were treated with 10 surgical or trans-endocardial catheter stem cell injections of 0.2cc. We have acquired high frequency ultrasound data of infracted and remote tissue using a Medison Accuvix V10 equipped with a raw radiofrequency (RF) data interface. The data where acquired at 129 frames per second, using a linear array transducer (center frequency = 8.5 MHz). RF data was used for deformation analysis.Results: Immediately after stem cell injections the injection site can be identified by an echogenic area. A 12 weeks old myocardial infarction shows larger radial strain in the epicardial region compared to the endocardial region (figure).Conclusion: This method is applicable to visualize an intramyocardial depot of stem cells directly after injection. The transmural gradient of the radial strain indicates local deformation inhomogeneities. More data needs to be acquired in these animals to demonstrate a relation between local strain and infarction size/severity or tissue damage. This novel technique provides an alternative to assess local cardiac deformation in the context of cardiac regenerative therapy.

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