Totally implantable robot to treat chronic atrial fibrillation.

Chronic atrial fibrillation affects millions of people worldwide. Its surgical treatment often fails to restore the transport function of the atrium. This study first introduces the concept of an atrial assist device (AAD) to restore the pump function of the atrium. The AAD is developed to be totally implantable in the human body with a transcutaneous energy transfer system to recharge the implanted battery. The ADD consists of a motorless pump based on artificial muscle technology, positioned on the external surface of the atrium to compress it and restore its muscular activity. A bench model reproduces the function of a fibrillating atrium to assess the circulatory support that this pump can provide. Atripump (Nanopowers SA, Switzerland) is a dome-shaped silicone-coated nitinol actuator 5 mm high, sutured on the external surface of the atrium. A pacemaker-like control unit drives the actuator that compresses the atrium, providing the mechanical support to the blood circulation. Electrical characteristics: the system is composed of one actuator that needs a minimal tension of 15 V and has a maximum current of 1.5 A with a 50% duty cycle. The implantable rechargeable battery is made of a cell having the following specifications: nominal tension of a cell: 4.1 V, tension after 90% of discharge: 3.5 V, nominal capacity of a cell: 163 mA h. The bench model consists of an open circuit made of latex bladder 60 mm in diameter filled with water. The bladder is connected to a vertically positioned tube that is filled to different levels, reproducing changes in cardiac preload. The Atripump is placed on the outer surface of the bladder. Pressure, volume and temperature changes were recorded. The contraction rate was 1 Hz with a power supply of 12 V, 400 mA for 200 ms. Preload ranged from 15 to 21 cm H(2)O. Maximal silicone membrane temperature was 55 degrees C and maximal temperature of the liquid environment was 35 degrees C. The pump produced a maximal work of 16 x 10(-3) J. Maximal volume pumped was 492 ml min(-1). This artificial muscle pump is compact, follows the Starling law and reproduces the hemodynamic performances of a normal atrium. It could represent a new tool to restore the atrial kick in persistent atrial fibrillation.

Artificial muscles to restore transport function of diseased atria.

Surgical treatment of persistent atrial fibrillation often fails to restore the transport function of the atrium. This study first introduces the concept of an atrial assist device to restore the pump function of the atrium. A micro motorless pump based on artificial muscle technology, is positioned on the external surface of the atrium to compress it and restore its muscular activity. A bench model reproduces the function of fibrillating atrium to assess the circulatory support that this pump can provide. The Atripump is a dome shape silicone coated nitinol actuator mounted on a plastic ring. A pacemaker-like control unit drives the actuator, which compresses the atrium, providing the mechanical support to the blood circulation. The bench model consists of an open circuit made of latex bladder 60 mm in diameter filled with water. The Atripump is placed on the outer surface of the bladder. Pressure, volume, and temperature changes were recorded. The contraction rate was 1 Hz with power supply of 12 V, 400 mA for 200 milliseconds. Preload ranged from 15 to 21 cm H20. The pump produced a maximal work of 16 x 10(-3) J. Maximal volume pumped was 492 ml/min. This artificial muscle pump is compact, and reproduces the hemodynamic performances of normal atrium.

Atria assist device to restore transport function of fibrillating atrium.

OBJECTIVE: The Maze procedure can restore sinus rhythm in patients suffering from chronic atrial fibrillation but often fails to restore the mechanical function of the atrium, the so-called atrial kick and requires long-term anticoagulation most of the time. A micro motorless pump (Atripump) based on artificial muscle technology positioned on the external surface of the atrium could compress the heart chamber, restoring atrium transport function. A bench model reproducing the mechanical function of human atrium and human environment has been developed to assess the circulatory support that such a pump can provide. METHODS: Atripump (Nanopowers SA, Switzerland) is a dome-shape, silicone-coated nitinol actuator to be sutured on the external surface of the atrium. A pacemaker-like control unit drives the actuator and manages the external compression of the atrium. The bench model consists of an open circuit made of rubber bladder, 60 cc in volume, connected to a vertically positioned and scaled tube that is filled at different levels reproducing changes in cardiac pre-load and after-load. The pump was placed on the outer surface of the bladder and both were immersed in water having a constant temperature of 37 degrees C. Pressure, volume and temperature at the interface dome-bladder were recorded. RESULTS: Pump ran 24 h for three consecutive months. During the experiment, no technical failure occurred and the pressure and volume values were repeatable during the experience. Nitinol fatigue was assessed measuring the wire's electric resistance that remained 400+/-10 Omega/m. Contraction rate was 1 Hz with power supply of 12 V, 400 m and heating time of 300 ms. Pre-load ranged from 11 to 15 mmHg. When inserted in the bath at 37+/-0.5 degrees C, maximal temperature between silicone membrane and rubber bladder was 39 degrees C. Maximal volume pumped was 492 ml/min. CONCLUSIONS: This artificial muscle pump can reproduce the mechanical effect of a normal human atrium. It is compact, reliable and follows the Starling law. The surface temperature is in the physiologic range and it could represent a new tool to restore the atrial kick in persistent atrial fibrillation.