Acoustic navigation of intramyocardial injection needle catheter using color doppler echocardiography

Background: Drug or stem cell intramyocardial delivery has been tested using transendocardial injections navigated by fluoroscopy and NOGA electromechanical mapping system. However, the exact location of the needle tip and the injection depth within the myocardium are difficult to determine due to limitations in depicting cardiac anatomy, and muscle thickness in particular, with fluoroscopy or NOGA. The objective was to develop a prototype of an intramyocardial injection catheter that allows visual localization of the injection needle tip in the myocardium under the guidance of conventional 2D color Doppler echocardiography. Methods: An acoustically active catheter (AAC)with a retractable injection needle was constructed using a commercially available steerable sheath and piezoelectric crystals. The navigation and myocardial injection were tested in a beating heart in animal experiments. Crystals on the AAC tip and needle tip were driven by a waveform generator and produced acoustic interactions with Doppler beam. The interaction resulted in realtime color markers in echocardiography scans. Results: In all cases, both AAC catheter tip and inserted needle tip in the myocardium were visualized clearly. Green color dye was injected through the needle lumen and successful formation of a dye deposit was observed at autopsy in 15 of 20 attempts. Conclusion: The concept of acoustically active navigation of the injection needle in a beating heart is presented. Guiding the injection needle within the left ventricular myocardium has potential to provide safer intramyocardial therapeutic delivery, utilizing a conventionally available echocardiography system.