A leadless intracardiac pacemaker powered by energy harvested from cardiac motion may generate sufficient electricity to pace the heart without an external power source in a preclinical study.
Researchers developed a self-sustaining leadless intracardiac pacemaker incorporating two triboelectric nanogenerators (TENG) that converted heartbeats into electrical energy. The system fit within the 0.7-cm³ cylindrical cell used by a commercial pacemaker and was designed for implantation with a commercial femoral-venous catheter. The researchers used 12 adult swine in acute experiments and a 4-week chronic implantation evaluation.
In vivo, TENGs produced electrical output synchronized with cardiac activity. The researchers measured maximum outputs of 14.2 V and 1.1 μA, with an average accumulated charge of 33 nC per cardiac cycle. In a capacitor-charging experiment, cardiac motion charged a 10-μF capacitor to 3 V within 653 seconds at a heart rate of 84 bpm.
To determine whether the harvested energy could support cardiac stimulation, the researchers used electronics from a different commercial pacemaker. Powered solely by energy from the TENG system, the pacemaker electronics increased an intrinsic heart rate from 92 to 100 bpm with stable ventricular capture. In a higher-demand experiment, the system increased heart rate from 75 to 120 bpm while maintaining stable electrical capture.
During the increase from 92 to 100 bpm, average systolic blood pressure decreased 15%, from 89 to 76 mmHg, and returned toward baseline when pacing power was stopped. The response was consistent with previously reported hemodynamic effects of increased pacing rates.
Prior to in vivo testing, the researchers evaluated energy harvesting under controlled mechanical conditions and found that power increased from 0.34 μW at an acceleration of 2 m/s² to 12.24 μW at 16 m/s². At 8 m/s², average output was 4 μW, approaching the 2.9- to 5.5-μW power consumption of modern leadless pacemakers. At 10 m/s², output reached 7 μW.
The integrated device achieved a volumetric power density of 277 μW/cm³ within a 0.7-cm³ device volume. The researchers reported that its power density was more than 100% higher than that of previously reported implanted nanogenerators included in their comparison. However, controlled mechanical simulations could not reproduce the complexity of physiologic cardiac conditions.
After exposure to accelerated fatigue testing at 25 Hz with 2-mm displacement, electrical output remained stable for over 300 million cycles, equivalent to about 10 years of oscillation at 60 beats/min.
They then evaluated whether the device could be delivered using clinically relevant methods. The pacemaker was advanced through the femoral vein and implanted in the right ventricular endocardium using a commercial catheter and a procedure corresponding to standard implantation.
One swine underwent chronic evaluation for 4 weeks. Serial radiographs showed the device remained securely positioned without migration or detachment. Echocardiography showed preserved cardiac function, with no observed tricuspid regurgitation, pericardial effusion, or interference with valvular motion.
Electrocardiographic and arterial blood pressure measurements remained stable, and hematologic and serum chemistry measures remained within reference ranges during the chronic study. Following explantation, the researchers observed localized fibrosis and tissue reaction around the fixation site but no thrombus formation, valvular damage, myocardial perforation, or diffuse myocardial injury.
The findings were preclinical and did not establish long-term safety or performance in patients. Only one swine underwent the chronic implantation evaluation. The researchers stated that longer implantation studies in larger animal cohorts are needed to assess tissue remodeling, fibrosis progression, calcification, and electromechanical coupling stability.
The researchers stated that a compact storage component would be needed to regulate pulsatile energy output, support circuitry, and provide a safety buffer. Instead, the energy-harvesting system is intended to continually replenish stored energy and extend device operating life.
The findings established a foundation for a “clinically compatible self-charging intracardiac pacing system,” wrote lead study author Pengfei Chen, of the Department of Materials Science and Engineering at the University of Wisconsin–Madison, and colleagues. Whether the system can provide adequate power and acceptable safety during long-term implantation and under diseased cardiac conditions remains to be determined.
Full disclosures of the study authors can be found in the study.
Source: Science Advances
