Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-10-01
2004-05-25
Manuel, George (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06740038
ABSTRACT:
BACKGROUND OF INVENTION
1. Technical Field
The present invention relates generally to systems and methods for assessing vascular health and for assessing the effects of treatments, risk factors and substances, including therapeutic substances, on blood vessels, especially cerebral blood vessels, all achieved by measuring various parameters of blood flow in one or more vessels and analyzing the results in a defined matter. In addition, the present invention further pertains to collecting, analyzing, and using the measurement of various parameters of blood flow in one or more vessels to establish protocols for and to monitor clinical trials. Further, the present invention relates to an automated decision support system for interpreting the values of various parameters of blood flow in one or more vessels in assessing the vascular health of an individual.
2. Background Information
Proper functioning of the vascular system is essential for the health and fitness of living organisms. The vascular system carries essential nutrients and blood gases to all living tissues and removes waste products for excretion. The vasculature is divided into different regions depending on the organ systems served. If vessels feeding a specific organ or group of organs are compromised, the organs and tissues supplied by those vessels are deleteriously affected and may even fail completely.
Vessels, especially various types of arteries, not only transmit fluid to various locations, but are also active in responding to pressure changes during the cardiac cycle. With each contraction of the left ventricle of the heart during systole, blood is pumped through the aorta and then distributed throughout the body. Many arteries contain elastic membranes in their walls which assist in expansion of the vessel during systole. These elastic membranes also function in smoothing pulsatile blood flow throughout the vascular system. The vessel walls of such arteries often rebound following passage of the systolic pressure waveform.
In auto-regulation, cerebral blood vessels maintain constant cerebral blood flow by either constricting or dilating over a certain mean arterial blood pressure range so that constant oxygen delivery is maintained to the brain. Vascular failure occurs when the pressure drops too low and the velocity starts to fall. If the blood pressure gets too high and the vessels can no longer constrict to limit flow, then breakthrough, hyperemia breakthrough, and loss of auto-regulation occur. Both of these conditions are pathologic states, and have been described in the literature in terms of mean arterial pressure and cerebral blood flow velocity. But there are outliers that could not be explained based on that model. The failure of the model is that it relies upon systemic blood pressure; the pressure of blood in the brain itself is not being measured directly. The resultant pressure curve has an S-shaped curve.
The force applied to the blood from each heart beat is what drives it forward. In physics, force is equivalent to mass times acceleration. But when blood is examined on a beat to beat variation, each heartbeat delivers about the same mass of blood, unless there is severe loss of blood or a very irregular heart rhythm. Therefore, as a first approximation, the force of flow on the blood at that particular moment is directly proportional to its acceleration.
Diseased blood vessels lose the ability to stretch. The elasticity or stretch of the blood vessel is very critical to maintaining pulsatile flow. When a muscle is stretched, it is not a passive relaxation. There is a chemical reaction that happens within the muscle itself that causes a micro-contracture to increase the constriction, so that when a bolus of blood comes through with each heartbeat, it stretches the blood vessel wall, but the blood vessel then contracts back and gives the kick forward to maintain flow over such a large surface area with the relatively small organ of the heart. This generates a ripple of waves, starting in the large vessel of the aorta and working its way through the rest of the vessels. As vessels become diseased, they lose the ability to maintain this type of pulsatile flow.
Further, if vessels are compromised due to various factors such as narrowing or stenosis of the vessel lumen, blood flow becomes abnormal. If narrowing of a vessel is extensive, turbulent flow may occur at the stenosis resulting in damage to the vessel. In addition, blood may not flow adequately past the point of stenosis, thereby injuring tissues distal to the stenosis. While such vascular injuries may occur anywhere throughout the body, the coronary and cerebral vascular beds are of supreme importance for survival and well-being of the organism. Narrowing of the coronary vessels supplying the heart may decrease cardiovascular function and decrease blood flow to the myocardium, leading to a heart attack. Such episodes may result in significant reduction in cardiac function and death.
Abnormalities in the cerebral vessels may prevent adequate blood flow to neural tissue, resulting in transient ischemic attacks (TIAs), migraines and stroke. The blood vessels which supply the brain are derived from the internal carotid arteries and the vertebral arteries. These vessels and their branches anastomose through the great arterial circle, also known as the Circle of Willis. From this circle arise the anterior, middle and posterior cerebral arteries. Other arteries such as the anterior communicating artery and the posterior communicating artery provide routes of collateral flow through the great arterial circle. The vertebral arteries join to form the basilar artery, which itself supplies arterial branches to the cerebellum, brain stem and other brain regions. A blockage of blood flow within the anterior cerebral artery, the posterior cerebral artery, the middle cerebral artery, or any of the other arteries distal to the great arterior circle results in compromised blood flow to the neural tissue supplied by that artery. Since neural tissue cannot survive without normal, constant levels of glucose and oxygen within the blood and provided to neurons by glial cells, blockage of blood flow in any of these vessels leads to death of the nervous tissue supplied by that vessel.
Strokes result from blockage of blood flow in cerebral vessels due to constriction of the vessel resulting from an embolus or stenosis. Strokes may also arise from tearing of the vessel wall due to any number of circumstances. Accordingly, a blockage may result in ischemic stroke depriving neural tissue distal to the blockage of oxygen and glucose. A tearing or rupture of the vessel may result in bleeding into the brain, also known as a hemorrhagic stroke. Intracranial bleeding exerts deleterious effects on surrounding tissue due to increased intracranial pressure and direct exposure of neurons to blood.
Regardless of the cause, stroke is a major cause of illness and death. Stroke is the leading cause of death in women and kills more women than breast cancer. Currently, more than three quarters of a million people in the United States experience a stroke each year, and more than 25 percent of these individuals die. Approximately one third of individuals suffering their first stroke die within the following year. Furthermore, about one third of all survivors of a first stroke experience additional strokes within the next three years.
In addition to its terminal aspect, stroke is a leading cause of disability in the adult population. Such disability can lead to permanent impairment and decreased function in any part of the body. Paralysis of various muscle groups innervated by neurons affected by the stroke can lead to confinement to a wheel chair, and muscular spasticity and rigidity. Strokes leave many patients with no ability to communicate either orally or by written means. Often, stroke patients are unable to think clearly and have difficulties naming objects, interacting with other individuals, and generally operating in society.
Strokes also result in massive expenditures of
Crutchfield Kevin
Davidson John
Fitall Simon
Mozayeni Robert
Hogan & Hartson LLP
Jung William C.
New Health Sciences, Inc.
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