New sensor based on fibre optics for measurement of heart movement

Abstract

Innovative fibre-optic sensor technology for measuring the movement of the myocardial walls, and from this the heart chamber volumes, was developed. An optical fibre, with a mirror at its end, is inserted into a catheter located in the heart. An opto-electrical control unit positioned outside the heart contains both the light source and the signal receiver. It generates and couples the light into the fibre and transforms and analyses the reflected signal. With such a system, the movement of the cardiac wall can be continuously measured during each cycle, because the fibre moves synchronously with the heart, and this movement bends the fibre, changing the optical attenuation. Experiments where the fibres were wound around metal cylinders of different diameters revealed a maximum sensitivity of 4% mm(-1), diameter. The noise signal corresponded to about 1% of the diameter. First tests in a working pig heart showed a high correspondence of the fibre signal with cardiac parameters. Although these tests are promising, further long-term, extensive experiments in preclinical test devices, and later in clinical tests, must be carried out before the new sensor is used in clinical practice. The fibre-optic technique could be used in monitoring devices, assist devices, pacemaker systems or cardioverter defibrillators.

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“…Multiple attempts might cause injury to the septum and increase the risk of perforation. Additionally, heart contraction is an axial twisting movement (20). The torsion between the large atrium and septum might result in perforation after removal of the sheath.…”

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“…Because of the extremely small mass and the high degree of flexibility of the thin fibers, the mechanical characteristics of the leads are not influenced. On the other hand, to avoid disturbances from movements outside the heart, a special fiber has to be constructed, with low sensitivity outside the heart and high sensitivity within the lead chambers [42]. From the comparison of typical sensors' specifications as shown in Table IV, fiber-optic sensor has smaller size, less weight, moderate power consumption and high reliability.…”

“…Only the end of the fiber outside the heart can be used for coupling the light into and out of the fiber. Therefore the end within the heart is provided with a mirror to reflect the light [42].…”