Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2001-04-19
2003-12-23
Schaetzle, Kennedy (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S009000
Reexamination Certificate
active
06668191
ABSTRACT:
FIELD OF INVENTION
This invention relates generally to medical device system for therapy of cardiovascular disorders, more specifically to adjunct (add-on) treatment of certain cardiovascular disorders by neuromodulation of a selected nerve or nerve bundle, utilizing an implanted lead-receiver and an external stimulator.
BACKGROUND
Electrical stimulation of the vagus nerve, and the profound effects of electrical stimulation of the vagus nerve on the central nervous system (CNS) activity extends back to the 1930's. Medical research has furthered our understanding of the role of nervous control of body functions. In the human body there are two vagal nerves (VN), the right VN and the left VN. The innervation of the right and left vagus nerves is different. The innervation of the right vagus nerve is predominately to the sinus (SA) node of the heart, and its stimulation results in slowing of the sinus rate. The cardiac innervation of the left vagus nerve is predominately to the AV node, and its stimulation results in delaying the conduction through the atrioventricular (AV) node.
The system and method of the current invention utilizes an implanted lead-receiver, and an external stimulator for adjunct (add-on) treatment or alleviation of symptoms for certain cardiovascular disorders, such as atrial fibrillation, inappropriate sinus tachycardia, and refractory hypertension. The system of this invention delivers neuromodulation pulses according to a limited number of predetermined programs, which are stored in the external stimulator, and can be activated by pressing a button. The predetermined programs contain unique combinations of pulse amplitude, pulse width, frequency of pulses, on-time and off-time. In one embodiment, the system contains a telecommunications module within the external stimulator. In such an embodiment, the external stimulator can be controlled remotely, via wireless communication.
Nervous Control of the Heart
FIGS. 1A and 1B
are simplified schematic diagrams showing nervous control of cardiovascular function. As shown in
FIG. 1A
, The cardiovascular (CV) center
222
located in the medullary center in the brain influences and controls cardiovascular functions such as heart rate, contractactility, and blood vessels. The cardiovascular center
222
in the brain
220
, receives input from the higher centers in the brain
224
and from receptors
226
such as baroreceptors and propriocepters. The cardiovascular (CV) center
222
of the brain
220
controls the effector organs in the body by increasing the frequency of nerve impulses. The CV center
222
decreases heart rate by parasympathetic stimulation via efferent impulses carried by the 10
th
cranial nerve or the vagus nerve. The CV center can also increase heart rate and cause vasoconstriction via sympathetic stimulation. Thus, the CV center
222
in the brain
220
exerts its control via the opposing actions of the sympathetic and parasympathetic stimulation.
Further, as shown in
FIG. 1B
baroreceptors located in the aortic arch
262
, and in the carotid sinus
260
send blood pressure information to the cardiovascular (CV) center
222
located in Medulla Oblongata
240
of the brain
220
. This information is carried by afferent fibers of Glossopharyngeal Nerve
55
and Vagus Nerve
54
.
Additionally of interest to the current patent application, the efferent fibers of the right vagus nerve predominately innervate the sinus node
252
and stimulation of these fibers will be used to control (slow-down) heart rate for Inappropriate Sinus Tachycardia Syndrome. The efferent fibers from the left vagus nerve predominately innervate the A-V node
256
of heart, and efferent stimulation of the left vagus nerve
54
will be used for controlling heart rate as adjunct (add-on) therapy for atrial fibrillation in this invention.
Atrial Fibrillation
Atrial fibrillation (AF) is both the most common sustained arrhythmia encountered in clinical practice, and the most common arrhythmia-related cause of hospital admission. Although health utilization costs related to AF are significant, little is known about its incidence and prevalence. Estimates indicate that 2.2 million Americans have AF and that 160,000 new cases are diagnosed each year. The incidence is higher in older adults, whose risk for developing AF is associated with advanced age. During atrial fibrillation, the atria of the heart discharge at a rate between 350 and 600 per minute. The ventricular rate during atrial fibrillation is dependent on the conducting ability of the AV node which is itself influenced by the autonomic system. Atrioventricular conduction will be enhanced by sympathetic nervous system activity and depressed by high vagal tone. In patients with normal atrioventricular conduction, the ventricular rate ranges from 100 to 180 beats per minute.
AF is characterized by a rapid, irregular ventricular rate, the irregularity being in rhythm and arterial pulse pressure amplitude. This can occur to such an extent that multiple pulse deficits (absence of an arterial pulse following ventricular excitation) are present. Current therapies are designed to extinguish the fibrillation activity or to control or abolish atrioventricular (AV) conduction.
Thus, the two components of acute management of patients with atrial fibrillation include control of ventricular rate and conversion to sinus rhythm. The traditional first step in acute treatment of patients with symptomatic AF who have a rapid ventricular response is to slow the ventricular rate. The first line of defense is usually drugs such as Digoxin, Metoprolol, Esmolol and verapamil etc. Drugs typically have side effects, and some patients may be refractory to drugs. Non-pharmacologic adjunct therapy such as nerve stimulation offers an alternative mode of therapy.
In a paper published by Van den Berg et al in the Aug. 19, 1997 issue of Circulation, the authors showed that heart rate variability in patients with atrial fibrillation is related to vagal tone. In an abstract published at the American Heart Association meeting, by Tabata et al from the Cleveland Clinic Foundation, the authors presented the results of heart rate reduction by vagus nerve stimulation on left ventricular systolic function. Their data showed a dramatic decrease in ejection fraction and stroke volume as atrial fibrillation was induced. Then, while still in atrial fibrillation, a return towards baseline of both ejection fraction and stroke volume, with vagus nerve stimulation of the atrio-ventricular (AV) node.
Thus, with the system of the present invention where an implanted lead-receiver is implanted within the body, and a stimulator with predetermined programs is external to the body, would be useful. The implantable and external components are inductively coupled. With turning the stimulator “on”, the symptoms of atrial fibrillation would be alleviated by decreasing the heart rate and increasing the stroke volume and ejection fraction.
Inappropriate Sinus Tachycardia
Inappropriate Sinus Tachycardia is a clinical syndrome with a relative or absolute increase of heart rate at rest or an exaggerated heart rate response inappropriate to the degree of physical or emotional stress. On the surface electrocardiogram, P-wave morphology during tachycardia is nearly identical to the P-wave morphology during normal sinus rhythm. The clinical manifestations of this syndrome complex are diverse. Young women make up most of the patient population, and clinical symptoms can range from intermittent palpitations to multiple system complaints.
Clinical signs and symptoms associated with inappropriate sinus tachycardia are often refractory to medical therapy with drugs. Drugs, such as &bgr;-adrenergic blockers or calcium channel blockers, usually either are not effective in controlling symptoms or are poorly tolerated. It is hypothesized that the inappropriate sinus tachycardia response in these patients is due to underlying autonomic dysregulation. The electrophysiologic findings are consistent with the diagnosis of inappropriate sinus tach
Droesch Kristen
Schaetzle Kennedy
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