Miniaturized Designs of Implantable and Wireless Hemodynamic Pressure Monitoring Capsules

Hemodynamic pressure (HP) monitoring is critical for managing cardiovascular diseases. Clinical Doppler echocardiography and invasive catheter monitoring cannot realize remote continuous monitoring in daily life. Current implantable wireless equipment depends on custom chips or indirect sensing, presenting challenges in cost-effective and precise applications. Here, we present systematic design strategies for implantable, wireless, and battery-free capsule-like HP monitoring under near and middle-distance circumstances.

The systems were composed of completely non-customized devices, with extremely compact volumes (<0.4 cm³). Near-distance monitoring utilized Near Field Communication with a piezoresistive sensor and foldable circuit designs. Middle-distance monitoring employed dual-winding antennas based on magnetic resonance (∼600 kHz) and Bluetooth. The power feedback circuit was optimized through human model electromagnetic simulations. Validation involved in vitro and in vivo experiments.

Near-distance system achieved 0.35 mmHg omnidirectional pressure accuracy under 5 mm tissue shielding. Middle-distance system attained the longest wireless power transfer distance (7.5 cm) via electromagnetic fields, supporting a capacitive sensor with 0.4 mmHg accuracy. In vitro tests in artificial tissue demonstrated stable data/energy transfer, accommodating axial misalignments up to ±45°. In vivo experiments on the beagle demonstrated real-time, wireless monitoring of left atrial pressure, whose rhythm synchronized with electrocardiograph recordings. The interatrial septum interventional installation was also validated.

The wireless and implantable capsules enable near and middle-distance hemodynamic pressure monitoring, even in dynamic swinging intracardiac situations. and has been validated in animal experiments.

The designs provide a universal method for in vivo fully-implantable pressure monitor development.