Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1999-01-12
2001-11-20
O'Connor, Cary (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S481000, C600S483000, C600S500000, C600S504000, C600S507000
Reexamination Certificate
active
06319205
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for the non-invasive detection and monitoring of a physiological state or medical condition by monitoring peripheral arterial tone. More specifically, the present invention relates to monitoring changes in the peripheral arterial vasoconstriction in reaction to such state or condition, particularly those related to cardiopulmonary distress and blood pressure in order to detect or monitor the physiological state or medical condition of the patient.
2. Description of Related Art
As noted above, the present invention relates to detection and monitoring of various physiological states and medical conditions by detecting hemodynamic events in body extremity of the patient. However, while the present invention relates to detecting and monitoring numerous physiological states and medical conditions, four particular examples generally related to cardiopulmonary distress and blood pressure are provided herein; namely, myocardial ischemia, sleep staging, sleep apnea syndrome, and continuous blood pressure monitoring. Therefore, the following discussion includes description of art related to these four examples.
Definitions of Related Terms in Myocardial Ischemia
1. Ischemia - a term used when an organ in the body is inadequately perfused with blood.
2. Myocardial ischemia - a term used when the heart muscle—myocardium—is ischemic.
3. Angina pectoris - (cardiac pain) - the clinical symptomatology usually produced by myocardial ischemia. Classically, these symptoms consist of pain, or discomfort, or pressure felt in the chest and/or in the left arm.
4. Atypical angina pectoris - ischemic events may produce atypical symptomatology, such as pain in the neck, molar teeth, and in other places.
5. Silent angina pectoris - refers to the condition of asymptomatic (painless) myocardial ischemia.
Silent angina is present in approximately 20% of people who sustain ischemic episodes. Consequently, they do not realize they have a life-threatening problem, and they do not seek medical advice. They are therefore at risk of sudden and unexpected death.
6. Coronary artery disease - the coronary arteries are the vessels which nourish the heart. In arteriosclerosis, narrowing inside the coronaries is caused by the swelling of voluminous cholesterol and calcium debris, replacing the normal elements of the walls of the arteries.
7. Chronic angina pectoris - in this category of angina pectoris, the ischemic symptoms are related to physical effort (i.e. are “demand-related”). The increased demand for blood required by the laboring heart cannot be accommodated by the fixed, non-expandable, rigid arteriosclerotic narrowing.
8. Unstable angina pectoris - in this category of angina pectoris, a clot of blood forms spontaneously in an arteriosclerotic narrow segment suddenly and unexpectedly, partially obstructing the artery and inducing myocardial ischemia. In most instances the clot is spontaneously dissolved after a while, the blood perfusion is reinstituted, and the myocardial ischemia is relieved.
9. Myocardial infarct - When the forming clot is not dissolved, but rather progresses to the state of a totally obstructing thrombus, or when atheroma ruptures blocking the artery, the myocardium, which is nourished by the involved artery, succumbs to necrosis. That is the myocardial infarct.
10. Arterial tone - The degree of “active tension” which the smooth muscle fibers surrounding the arteries impart. When activated (usually by sympathetic nerve endings or by blood bourne or locally elaborated mediators), these fibers contract and in so doing reduce the calibre of the arteries. When the degree of active tension is high, this results in state of vasoconstriction and conversely, when the degree of active tension is low vasodilation occurs. Apart from active tension, arterial walls also experience passive tension which is due to the blood pressure within the arteries.
11. Coronary angiography - The practice of the radiographic visualization of the coronary arteries. A radio-opaque material is injected into the origin of the coronary arteries within the aorta by way of an arterial catheter which is inserted into an artery of an arm or leg, and is then advanced through the artery towards the heart.
12. Cardiopulmonary distress - a general term used to describe a low grade negative impact on the patient induced by an acute impairment in the cardiopulmonary function. This can result from, among others, myocardial ischemia, valvular heart disease, cardiomyopathy, congestive heart failure and chronic lung disease.
Prior Art Methods for Detecting Myocardial Ischemia
In patients who sustain typical episodes of unstable angina pectoris associated with pain, the diagnosis of spontaneous ischemia is made on the basis of their symptoms. Usually, coronary angiography is performed on these patients for selecting the mode of therapy (e.g. surgery, drug therapy, balloon angioplasty, etc.). However, people who complain about chest pain linked to physical activity, as well as people in whom, for other medical reasons, the presence or absence of coronary artery disease needs to be determined, are referred to cardiac stress tests.
In cardiac stress tests the heart is provoked to increase its demand for oxygen by using treadmill, bicycle and other physical stress exercises, or pharmacologically. A number of methods, as described herein, are available for detecting events once a demand related ischemia develops during cardiac stress tests. The predictive values of such existing methods, however, vary from approximately 50% to 85% and therefore none is sufficiently reliable to be used as a sole determinate of disease or a universal standard.
The following are the diagnostic techniques in use for detecting myocardial ischemia elaborated during exercise tests:
1) ECG (Electrocardiography): The ECG depicts abnormal electrical activities which may arise in ischemic myocardial regions. The sensitivity and specificity of the ECG in detecting myocardial ischemia is directly related to the extensiveness of the arteriosclerotic disease. Hence, high risk localized disease (i.e. limited to one or two arterial branches) may be easily overlooked. Although the overall predictive value of ECG in stress test is only approximately 60%, it is still the most important tool for detecting chronic angina pectoris, and because of its easy applicability and low cost, it is the only available method for screening purposes.
2) Stress echocardiography: This technique is based on two dimensional ultrasonic imaging of the walls of the heart. During the stress testing the myocardial segments related to arteriosclerotic coronary arteries may become ischemic. Consequently, wall motion disturbances, such as hypokinesia and/or a decrease in wall thickening, may be depicted by the echocardiograph. Continuing improvements in this technique have increased the predictive diagnostic value of stress echo to approximately 75%-80%, which is nearly as high as nuclear imaging technologies. The test can be performed in the doctor's office but since it is labor intensive and professionally demanding it is not appropriate for mass screening.
3) Nuclear imaging technologies. In each of the nuclear technologies described below, radioactive isotopes are injected intravenously. In techniques b and c described below, a second intravenous dose of the same isotope is required some time after the first is washed out and the patient is at rest. This enables the physician to distinguish between filling defects due to infarcted regions versus transient filling defects in demand-related ischemic segments.
Patients deemed to have a significant degree of demand related myocardial ischemia on the basis of the diagnostic tests described below are usually then referred for cardiac catheterization and coronary angiography, which is the most invasive, but also the most definitive diagnostic test available. In most cases the ultimate treatment choice in cases in which nuclear tests are posit
Goor Daniel A
Lavie Peretz
Schnall Robert P
Sheffy Jacob
Itamar Medical (C.M.) 1997 Ltd.
Natnithithadha Navin
O'Connor Cary
Sughrue Mion Zinn Macpeak & Seas, PLLC
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