Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-04-08
2004-03-23
Layno, Carl (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S046000, C607S004000
Reexamination Certificate
active
06711442
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO A MICROFICHE APPENDIX, IF ANY
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to therapeutic painful stimuli such as electric pacing and subthreshold pulses, and more particularly to the process of reducing the pain associated with these therapeutic painful stimuli by modifying a patient's pain perception and response using prepulse inhibition (PPI). Specifically, the present invention relates to reducing the pain and discomfort associated with painful transcutaneous and transesophageal cardiac pacing and subthreshold transcutaneous stimuli as provided using modern, noninvasive, transcutaneous or transesophageal pacing devices, either as stand-alone cardiac pacemakers, combination pacemaker-ECG monitors, or combination pacemaker-monitor-defibrillators.
2. Background Information
Implantable cardioverter-defibrillators (ICDs) deliver high-voltage electrical pulses (shocks) to terminate cardiac arrhythmias. This treatment is highly successful, but it is severely painful and may even stun a patient temporarily. Initially, painful and startling therapeutic shocks were considered acceptable only as a treatment of last resort. Because of this, ICD therapy was restricted to ventricular arrhythmias which were both life-threatening and refractory to all other therapies. Subsequently, however, ICDs have become first-line therapy for patients with a history of life-threatening ventricular arrhythmias and patients at risk for life-threatening ventricular arrhythmias. Controlled studies have shown that ICDs are superior to alternative therapy for specific groups of these patients. These studies are the Multicenter Automatic Defibrillator Implantation Trial (Moss et al, N Engl J Med 1996; 335: 1933-1940) and the Antiarrythmics Versus Implantable Defibrillators Trial (Zipes et al, N Engl J Med 1997; 337: 1576-1583).
As ICD therapy has been applied to larger numbers of patients with ventricular arrhythmias, more attention has been paid to the painful and startling nature of the therapeutic shocks and the psychological complications of this therapy. These factors limit patient acceptance of ICD treatment of arrhythmias in conscious patients. A significant fraction of patients report anxiety and fear of painful ICD shocks ((1) Dougherty, Psychological reactions and family adjustment in shock versus no shock groups after implantation of internal cardioverter defibrillator, Heart Lung 1995; 24: 281-291—(2) Dunbar et al, Cognitive therapy for ventricular dysrhythmia patients, J Cardiovasc Nursing 1997; 12: 33-44—(3) Luderitz et al, Patient acceptance of ICD devices: Changing attitudes, Am Heart J 1994; 127: 1179-1184—(4) Morris et al, Psychiatric morbidity following implantation of the automatic ICD, Psychosomatics 1991; 32: 58-64). Shocks correlate with anxiety, psychiatric morbidity and psychological distress in ICD recipients. In one study 87.5% of patients experienced “nervousness” after a shock and 12.5% experienced “terror” or “fear.” Patients who have experienced large numbers of repetitive shocks frequently suffer from a form of post-traumatic stress disorder.
Recently, ICD therapy has been applied to treatment of atrial arrhythmias, particularly atrial fibrillation ((1) Lau et al, Initial clinical experience with an implantable human atrial defibrillator, PACE 1997; 20: 220-225—(2) Timmersman et al, Early clinical experience with the Metrix automatic implantable atrial defibrillator, European Heart J 1997; 134). Although atrial fibrillation usually is not life-threatening, it is the most common arrhythmia requiring hospitalization in the United States. It causes potentially disabling symptoms of palpitations, shortness of breath, or chest pain and is an important cause of stroke.
The painful and startling nature of ICD shocks are considered a particular limitation for patient acceptance of ICD treatment of atrial fibrillation. It has been stated in recent published literature (Cooper et al, Internal atrial defibrillation in humans: Improved efficacy of biphasic waveforms and the importance of phase duration, Circulation 1997; 96: 2693-2700) that the ultimate acceptance of a fully automatic atrial defibrillator will depend on the reduction of pain to acceptable levels.
To this end, present state-of-the-art holds that a primary method of reducing the pain associated with these shocks is to reduce the strength of the shock pulse as measured by energy or voltage. This method requires a significant decrease in the shock strength required to defibrillate with a success rate of 50%. This shock strength is known as the defibrillation threshold. Recent studies have focused on reducing the atrial defibrillation threshold by altering the shape (waveform) of the delivered shock pulse or the locations of the electrodes (electrode configuration) through which these shocks are applied. The fundamental hypothesis is that lowering of the defibrillation threshold will permit atrial defibrillation with weaker shocks and thereby decrease the pain associated with these shocks in patients.
The shock strength judged tolerable for defibrillation in conscious patients has differed in previous studies, but is generally in the range of 0.1-0.5 joules (J). Zipes (Zipes et al, Clinical transvenous cardioversion of recurrent life-threatening ventricular tachyarrhythmias: Low energy synchronized cardioversion of ventricular tachycardia and termination of ventricular fibrillation in patients using a catheter electrode, Am Heart J 1982; 103: 789-794) reported that shocks of 0.5 J or less delivered between electrodes in the superior vena cava and right ventricle were tolerable for treatment of ventricular tachycardia. However, using the same electrode system, Perelman (Perelman et al, Assessment of prototype implantable cardioverter for ventricular tachycardia, Br Heart J 1984; 52: 385-391) found that 3 of 9 patients reported severe discomfort at a shock strength of 0.1 J. Nathan (Nathan et al, Internal transvenous low energy cardioversion for the treatment of cardiac arrhythmias, Br Heart J 1984; 52: 377) delivered transvenous shocks to 19 conscious patients for various atrial and ventricular arrhythmias. Fourteen of 19 patients described severe discomfort with shock strengths 0.5 J. Murgatroyd (Murgatroyd et al, Efficacy and tolerability of transvenous low energy cardioversion of paroxysmal atrial fibrillation in humans, J Am Coll Cardiol 1995; 25: 1347-1353) determined the range of tolerable shock strengths for the most favorable electrode configuration for atrial defibrillation (right atrium to distal coronary sinus). Although the range of shock strengths tolerated without severe discomfort was 0.1 to 1.2 J, seven of 19 patients found even 0.1 J shocks intolerable. Using a different electrode system, Steinhaus (Steinhaus et al, Atrial defibrillation: are low energy shocks acceptable to patients? PACE 1996; 19: 625) delivered shocks of 0.4 J and 2.0 J shocks in randomized order. Patients reported no difference in perceived pain between the two shock strengths. Both shock strengths were given discomfort scores of approximately 7 on a scale of 0-10.
However, Steinhaus found that the second shock was judged significantly more painful than the first shock, independent of shock strength. This observation is important because a strategy for reducing pain in defibrillation of arrhythmias which are not life-threatening (such as atrial fibrillation) contemplates clinical use of defibrillation shocks with strength near the defibrillation threshold. The hypothesis is that, even if multiple shocks are required to terminate the arrhythmia, multiple weaker shocks will be better tolerated than one strong shock. Steinhaus' data suggest that any clinical benefit in pain reduction achieved by delivering clinical defibrillation shocks with strength near the defibrillation threshold is likely to be offset by the increased discomfort associated with subsequent shocks as weak as
Brewer James E.
Swerdlow Charles D.
Swerdlow Neal R.
Imperception, Incorporated
Layno Carl
Skinner & Associates
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