Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2000-05-12
2004-04-27
Jastrzab, Jeffrey R. (Department: 3762)
Surgery
Diagnostic testing
Cardiovascular
C381S067000, C181S131000
Reexamination Certificate
active
06726635
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to medical diagnostic instruments, and more particularly, to such instruments for detecting abnormal heart functions.
BACKGROUND INFORMATION
Patients occasionally develop heart disease, the prompt and timely discovery of which can be determinative of patients' health and survival. Until the 19th century, medical caregivers had to press their ears against patients' chests in order to hear heart sounds. When the stethoscope (“spy of the chest” in Greek) was introduced by René Laennec (1781-1826), it enabled medical caregivers to hear heart sounds with improved ease and clarity. “In search of the perfect stethoscope that hears all heart sounds, and explains them to you.” (Laennec)
The ballistic recoiling of the heart produces a vibration when it moves its apex upward, rightward, and against the underside of the chest wall before the ejection of blood. This motion or vibration is typically inaudible and infrasonic, having a sound frequency of less than about 30 Hertz. There are other low frequency, low amplitude vibrations which normally occur during cardiac filling. There are also abnormal cardiac vibrations with sound frequencies as low as about 10 Hertz, but of high amplitude that occur when the heart fills abnormally. The period of cardiac filling is called diastole, and when these abnormal vibrations occur, they indicate diastolic dysfunction of the heart. These abnormal vibrations during diastole are called pathologic gallops. Some gallops are faint and difficult to hear, and some are infrasonic.
There are two types of pathologic gallops of primary clinical significance: An S4 type of gallop, which occurs during late diastole; and an S3 type of gallop, which occurs during early diastole. Many gallops are palpable and visible even when they are inaudible. This is because they are of high-energy amplitude despite their low frequencies. Detection of gallops is very important, and can lead to the diagnosis and treatment of such cardiac disorders as hypertrophic heart syndromes, valvular lesions, cardiomyopathies, and congenital heart problems.
A visual and palpable assessment of cardiac motion of a patient in the supine position may be made at the left chest wall near the left breast. This location is called the cardiac apical impulse, and for purposes of clarity is also herein referred to as the cardiac apical impulse point. The cardiac apical impulse point is a single area typically less than about 15 millimeters in diameter. The skin motion at this location is normally caused by the recoiling of the heart when it moves its ventricular apex upward, rightward, and against the underside of the chest wall. Presently, medical caregivers may examine the heart motions at the cardiac apical impulse point by placing their fingertips against the skin at this point to enable tactile detection of apical impulses having sufficient amplitude.
Over the past 60 years, sophisticated and elaborate laboratory apparatus have been developed to detect and record heart movements, and enable medical caregivers to analyze the data for indications of abnormal heart conditions. The apexcardiogram (“ACG”), for example, which was in popular use until the early 1980's, was capable of revealing low frequency heart motions by means of electromechanical sensors affixed to a patient's chest. The ACG signals were recorded on a strip chart recorder for later analysis. An electrocardiogram (“EKG”) and a separate phonocardiogram were required to be performed contemporaneous with the ACG in order to provide correlation between the low frequency heart motions and the additional heart signals. The three charts were then correlated, as by technicians, for later analysis by caregivers. Although this method was very useful for detecting heart irregularities in suspected cases, the time delay incurred by a patient between seeing a physician for referral to an ACG laboratory, testing in the laboratory by technicians, correlation of strip chart results, and analysis and diagnosis by at least one physician, generally hindered prompt and effective treatment in time-critical cases. In addition, the large expense for this labor-intensive procedure may have precluded its use in many instances.
By the mid-1980's, the ACG had been generally displaced by the echocardiogram. The echocardiogram uses ultrasonic waves to monitor heart function and provides more detail than the ACG. Unfortunately, the echocardiogram suffers from some of the same drawbacks as the ACG, including the requirement for special laboratory testing and associated expense. Like the ACG, the echocardiogram also fails to produce recognizable sounds indicative of the infrasonic heart motions, and therefore fails to disclose a method for their discovery.
Various other prior art systems are also directed toward monitoring human heart function. For example, U.S. Pat. No. 5,218,969 to Bredesen et al. (“the '969 patent”) depicts an electronically enhanced stethoscope for detecting heart sounds. However, the '969 patent teaches filtering out sounds below 50 Hz (see FIG. 3F). Since human hearing is generally recognized to extend to at least as low as 30 Hz, the stethoscope of the '969 patent is not capable of detecting heart vibrations of frequency below the range of human hearing, even if it may amplify low amplitude sounds which are above 50 Hz. Accordingly, the electronic stethoscope of the '969 patent does not detect infrasonic cardiac apical impulses, and in fact is incapable of detecting any phenomena emitting a frequency below 50 Hz.
U.S. Pat. No. 5,178,151 to Sackner (“the '151 patent”) shows another system for detection of heart irregularities. The '151 patent shows placement of a plurality of motion transducers about the thoracic region of a patient's chest wall. Blood vessel volume, blood pressure waveforms, and other thoracic motions including respiratory and cardiac apical motions are measured as conglomerate signals that must be further analyzed to determine the presence of heart irregularities. Due in part to its bulk, complexity, cost, and requirement for further analysis, this system suffers from design constraints that generally preclude its inclusion in a general caregiver's office. The apparatus of the '151 patent further lacks provision for transmitting the acoustic heart waveform data typically relied on during a routine physical examination.
The basic acoustic stethoscope, whether electronically amplified, filtered or not, can only be used to hear what Rene Laennec heard with his original wooden device. Only a small percentage of the vibrations of the heart are actually detected by an acoustic stethoscope. These audible vibrations range between about 40 Hertz to 500 Hertz and about 0.002 to 0.5 dynes/cm
2
(amplitude). The remaining vibrations are inaudible because of the typical thresholds of human hearing. Infrasonic vibrations of sufficient amplitude have heretofore only been detectable with bulky, complex, and costly apparatus requiring labor intensive analysis. Heart gallops rest near the division of audible and infrasonic vibrations. Heart gallops have been called the heart's “cries for help.” Detection of these vibrations is important in diagnosing cardiac pathology and is why palpation of the cardiac apical impulse is an extremely important, yet often neglected, part of the cardiac exam.
All in all, the above-described prior art fails to recognize the utility of detecting infrasonic heart motions and producing audible outputs that are indicative of those motions. Such prior art also fails to put infrasonic heart motion data in context with traditional acoustic heart data. It is therefore an object of the present invention to overcome the above-described significant drawbacks and disadvantages of the prior art.
SUMMARY OF THE INVENTION
The present invention is directed to a cardiac impulse detector for use in routine cardiac examinations, which employs a sensor capable of detecting infrasonic cardiac apical impulse
Jastrzab Jeffrey R.
McCarter & English LLP
Oropeza Frances P.
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