Tiny implantable echo probemonitors cardiac functions

Aloka assists development of transducer

Researchers in Japan are working on a miniaturized implantableechocardiography probe (IEP) that could replace bulky transesophagealechocardiography (TEE) probes for monitoring cardiac functions.Tokyo-based ultrasound vendor Aloka is assisting with the developmentand manufacture of the novel transducer, which has shown substantialbenefit in the monitoring of cardiac function in open-heart surgerypatients. The latest work on the IEP device was presented at lastmonth's American Heart Association meeting in Anaheim, CA.

The tiny phased-array Doppler biplane transducer has a centerfrequency of 5 MHz and is mounted on the tip of a flexible probethat is less than 7.4 mm in diameter, which is narrower than apencil, according to its inventor, Dr. Ryohei Yozu, an assistantprofessor of cardiovascular surgery at Keio University in Tokyo.The probe is still investigational in Japan as well as in theU.S.

IEP is designed to provide real-time images for continuousmonitoring of ventricular wall motion, measurement of cardiacoutput, detection of intracardiac thrombus and assessment of valvuloplastyand prosthetic valve function, Yozu said.

The probe is not intended to replace traditional postoperativecardiac monitoring techniques such as ECG, invasive blood pressureand Swan Ganz catheter measurement of cardiac output. Rather,it may become an alternative to larger TEE probes that are nowused.

"The probe is implanted much the same as a pericardialdrainage tube and is similarly removed," Yozu said. "Becausethere is no TEE probe in the mouth, patients experience less distress;they can speak and perform oral hygiene. There is no lung tissueor air between the probe and the heart, so the image is very clear."

Like TEE devices, IEP may also prove useful for helping physiciansevaluate the recovery of cardiac function and the time to weanthe patient from mechanical ventilation subsequent to open-heartprocedures.

According to Yozu's presentation at the AHA meeting, the averageIEP device was implanted for a period of two days; one deviceremained implanted for seven days. No deaths or complications,such as arrhythmia, bleeding or infection, have been reportedin the 26 patients in whom the device has been implanted thusfar.

Yozu plans to have IEP in clinical trials within a year. Althoughit is too soon to predict the price of a commercial version ofIEP, Yozu hopes that it will be less than $1000. The developmentof a single-use version is also a possibility.

Although IEP is currently used exclusively for high-risk patients,its comfort and convenience for patients as well as its diagnosticimaging value and ease of use for physicians could soon make itsuse routine for cardiac surgeries.