Monday, August 20, 2007

Pacemaker Leads: Is Ping the Thing?

Imagine having no pacemaker wire between the pacemaker pulse generator and the heart. It seems it has happened:
( A remote ultrasound energy source may one day replace implanted pacing leads in permanent pacemakers, results from a pilot study suggest [1]. Dr Kathy L Lee (University of Hong Kong, China) and colleagues used an ultrasound transducer on the chest wall to transmit energy to a receiver electrode on the tip of a transvenously placed electrophysiology catheter in 24 patients, reporting their results in the August 28, 2007 issue of the Journal of the American College of Cardiology.

The system, says Lee, "works by transfer of energy in different forms: ultrasound energy is transmitted through the chest wall to a receiver in the heart, and the energy is transferred back into electrical energy for direct myocardial stimulation or pacing. Conventionally, the electrical impulse is delivered via a pacing lead; with transfer of ultrasound energy, no pacing lead is required. . . . When this technique is mature enough for clinical use, it should be less burdensome, as less hardware is implanted."


The authors tested their ultrasound transducer and receiver electrode during or immediately following clinical electrophysiology procedures in 24 patients, testing a total of 80 pacing sites in the right atrium, right ventricle, and left ventricle; two additional sites were excluded from testing because ultrasound energy could not be consistently "captured" by the receiver electrode. Ultrasound energy from the transducer was amplitude-adjusted and transmitted at levels ranging from 313 kHz to 385 kHz. The receiver electrode, containing circuitry to convert the ultrasound energy to electrical energy, was positioned on the tip of a steerable bipolar electrophysiology catheter. Lee et al report that pacing was successfully achieved at all 80 test sites and consistently achieved at 77 sites, with no adverse events and no patient discomfort. Mean distance between the transducer and receiver was 11.3 cm but ranged from 5.3 to 22.5 cm."
It seems the frequencies used might have interference issues with conventional cell phone technologies in its present form, but this report demonstrates an important "proof of concept" of the application and has exciting ramifications for future pacemaker technologies.


Reference: Lee KL, Lau CP, Tse HF, et al. First human demonstration of cardiac stimulation with transcutaneous ultrasound energy delivery: Implications for wireless pacing with implantable devices. J Am Coll Cardiol 2007; 50:877-883.

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