Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Patent
1999-11-26
2000-10-17
Getzow, Scott M.
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
A61N 1365
Patent
active
061344729
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to devices for determining the optimal rate for emission of a stimulation pulse to a heart.
2. Description of the Prior Art
The ability to control the heart rate by means of electrical stimulation is important to the well-being and survival of many people afflicted by various defects in the function of their hearts. Battery-powered stimulation devices are available for different kinds of disorders.
The heart comprises a left atrium, right atrium, left ventricle and right ventricle and contains e.g. a sinus node (sinoatrial node. SA node), an area made up of special tissue in the wall of the heart's right atrium. In the normal, healthy state this area emits periodic, recurrent electrical pulses, each of which starting a heart cycle. When the pulse from the sinus node is propagated across the walls of the atrium, it triggers contraction of the atrium for expulsion of blood into the corresponding ventricle. The pulse is carried to another tissue area in the heart which has a special delay function, the atrioventricular (AV) node, from which it is carried on special electrically conductive tissue pathways to the ventricles. It is during this phase, when the electrical pulse passes along the conductive pathways to the ventricular walls, that blood is "pumped" from the atrium to ventricle. By the time this pulse arrives to trigger contraction of the ventricles, the ventricles have been expanded by inflowing blood and are ready to contract in order to pump blood to the lungs and circulatory system. After each contraction of the ventricles, a resting period starts during which the atria fill with blood, and lasts until the SA node generates the next pulse.
Normal rhythm, i.e. sinus rhythm, arises in the SA node. A faulty rhythm or rate, i.e. arrhythmia, can develop for different reasons. For example, the pathways, made of electrically conductive tissue, to or in a ventricle may be damaged or blocked so pulses emitted in the atrium are unable to trigger any contraction of the ventricle. In such cases, an electrical stimulation pulse can be supplied by an electronic stimulation device, i.e. a pacemaker. The generating of stimulation pulses by most of the stimulation devices currently in use is synchronized with or generally dependent on the heart's intrinsic electrical activity. This activity can be monitored with sensor electrodes placed somewhere in the patient's body, e.g. in or adjacent to the heart.
These sensor electrodes in an appropriate system sense electrical voltages generated during heart activity. The electrical voltage sensed with surface electrodes on the exterior of the body has the following general morphology during a heart cycle: A low voltage pulse, the P wave, designates an atrial event, corresponding to depolarization of muscle cells in the walls of the atria, causing these walls to contract. A more complex pulse segment is referred to as the QRS complex and encompasses e.g. a large electrical pulse. This area designates a ventricular event in the form of depolarization of muscle cells in ventricular walls when these cells contract, and the heart's actual blood-pumping process is started and performed. A low voltage pulse further designates the start of repolarization of the cells in ventricular walls, i.e. recovery from their preceding contraction, and is referred to as the T wave. These pulses/pulse segments normally follow each other over time, i.e. a P wave starts first in a heart cycle, followed by the QRS complex and, finally, the T wave. These segments are not always distinguishable in the electrical voltage sensed by sensor electrodes placed in or by the heart. Thus, no T wave and often not even the QRS complex are discernible with an electrode placed in an atrium. The P wave is not visible with an electrode in the ventricle.
A typical stimulation device can operate in the following general manner: The stimulation device awaits an atrial event, signaled by corresponding electrical activity in the heart,
REFERENCES:
patent: 4535774 (1985-08-01), Olson
patent: 4867163 (1989-09-01), Schaldach
patent: 5156147 (1992-10-01), Warren et al.
patent: 5417715 (1995-05-01), Noren et al.
patent: 5500006 (1996-03-01), Heinze
Lidman Johan
Noren Kjell
Strandberg Hans
Getzow Scott M.
Pacesetter AB
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