Surgery – Diagnostic testing
Reexamination Certificate
2002-09-19
2004-11-23
Jones, Mary Beth (Department: 3736)
Surgery
Diagnostic testing
C600S549000, C128S898000
Reexamination Certificate
active
06821249
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to apparatus and methods for continuous monitoring of health condition in patients with congestive heart failure.
2. Background Information
Congestive heart failure (“CHF”) is a chronic inability of the heart to maintain an adequate output of blood from one or both ventricles of the heart to meet the metabolic demands of the tissues. With a markedly weakened left ventricle or right ventricle or both, the volume of blood presented to the heart is in excess of the heart's capacity to move it along. Consequently, fluid builds up behind the heart. With a weakened left ventricle or right ventricle or both, there is a shift of large volumes of blood from the systemic circulation into the pulmonary (lung) circulation. If the inability to move the volume of blood forward is due to a left heart problem without the right side failing as well, blood continues to be pumped into the lungs by the normal right heart, while it is not pumped adequately out of the lungs by the left heart. As the volume of blood in the lungs increases, the pulmonary vessels enlarge, pulmonary venous congestion develops, and, once the pulmonary capillary pressure rises above a critical point, fluid begins to filter out of the capillaries into the interstitial spaces and alveoli (air sacs in the lungs where exchange of oxygen and carbon dioxide occurs), resulting in pulmonary edema. Subsequently this can lead to pleural effusion (effusion is the escape of fluid into a part) and abdominal effusion. If the abnormality lies in the right heart or the pulmonary arteries, limiting the ability to move blood forward, then congestion occurs behind the right heart (causing pleural effusion and/or build up of fluid in the abdomen).
CHF is the fourth leading cause of death in the United States and a leading cause of poor quality of life in the population over 65. There are 5 million cases of CHF in the United States. In patients diagnosed with CHF, sudden cardiac death occurs at 6 to 9 times the rate of the general population. A 44 year follow-up Framingham Heart Study of the National Heart, Lung and Blood Institute (the “NHLBI”, part of the U.S. National Institute of Health), has found, based on hospital admissions, that there are nearly 550,000 admissions of new cases of CHF each year in the United States. The number of patients hospitalized for CHF annually is 1.01 million. CHF approaches 10 cases per 1000 members of the U.S. population after age 65. CHF hospitalizations have increased steeply in the last 20 years, the number of hospital discharges (which includes both the living and the dead) more than doubling both for males and females from 1979 to 1999. As the population of 65 and older grows hugely in the U.S. with the aging of the baby boomer generation, and as the number of first heart attack survivors increases, CHF portends a dramatic increase of morbidity and mortality and a burgeoning drain on healthcare funds in the U.S.
One of many needs for CHF patients is accurately predicting when they have a significantly worsening condition signifying death draws near. With sufficient warning, steps can be taken to save them. Among CHF patients in the very poorest condition, there is a need to know which patients are likely to have the shortest lives in order to select those for whom heart transplantation or left ventricular assist device (LVAD) implantation is the appropriate treatment.
Bedside classifiers such as age, sex, ischemic heart disease (IHD), cardiac cachexia, and New York Heart Association (NYHA) functional classes for CHF are useful factors for general prognosis of risk of poor outcome, but do not provide physiologically specific or dynamic information. With today's sophisticated medical diagnostics technology, especially in large urban medical center complexes, much can be done in a hospital environment to develop specific test information concerning the condition of a patient's heart. Numerous predictors of mortality in patients with CHF have been described in the literature. Some of the tests that can be performed include, without limitation: chest wall impedance, chest impedance peak oxygen uptake (dot(V)O2), left and right ventricular ejection function (LVEF and RVEF), both respiratory and circulatory response to exercise (exercise capacity, especially if combined with maximal oxygen consumption), cardiac index, left ventricular cavity size, left ventricular stroke work index, right and left ventricular filling pressure (RVFP and LVFP) and isovolumic relaxation time (LV IVRT), left ventricular systolic pressure (LV SP), right and left atrial pressure, systemic vascular resistance, calculated wall stress, tricuspid regurgitation (TR), jugular venous pressure (JVP), pulmonary capillary wedge pressure (PCWP), 6-minute walk distance, arterial and venous pH, pO2, pCO2, serum creatinine, serum sodium, plasma norepinephrine, plasma neurotensin, plasma renin activity (PRA), plasma arginine vasopressin, plasma atrial and brain natriuretic peptides, plasma endothelin-1, plasma interleukin-6, plasma tumor necrosis-alpha, serum sodium, serum potassium (and total potassium stores), serum magnesium, lymphocyte count, frequent ventricular extrasystoles, ventricular tachycardia (VT), bundle-branch blockage (left and right), atrial fibrillation or flutter, T-wave alternans, QT prolongation and dispersion, PACO
2
, pH, respiratory rate, QRS width, R—R variability, and dP/dt. Quite surprisingly, however, these heart performance or heart condition factors together account for only a portion of statistical variance as a predictor of poor outcome in CHF patients, usually applying to only a few patients, leaving prognosis uncertain for the individual patient.
Even these tests don't help much if the patient isn't hospitalized to receive them at a critical time. Home-monitoring promises an opportunity to reduce costs and improve quality of life in some patients. Prognostic variables described in the literature that might be readily monitored at home include S3 gallop, Cheyne-Stokes respiration, apnea/hypopnea index, systolic blood pressure (SBP), heart rate at rest (HR), pulse pressure (PP), and mean arterial pressure (MAP). However, these factors are not statistically strong predictors of risk of imminent death.
SUMMARY OF THE INVENTION
Our invention involves detecting a significant worsening of condition of a CHF patient and issuing an alert so that life saving therapies and interventions can be summoned to save the patient's life and/or intervention devices can be activated or adjusted. In an aspect of the invention, the output of an alert is to a medical device that applies a therapeutic treatment to the patient to treat the patient's condition of congestive heart failure. The device suitably may be a ventricular assist device responsive to the alert to provide additional ventricular assist to the patient. The device may be an medication release device responsive to the alert to adjust the amount of medication the patient is receiving. Or the device may be a cardiac rhythmic regulator, such as a pacemaker or defibrillator, responsive to the alert to optimize the patient's regulator parameters to reverse hypothermia, or a device responsive to the alert to warm the patient.
In a significant departure from use of other prognostic factors, these new methods and apparatus not only are dynamically predictive but also are applicable for watching the individual patient on an ambulatory and continuous basis, allowing the patient to be monitored at home or elsewhere as well as in-hospital. This allows the patient an improved quality of life yet protects the patient by enabling immediate availability of professional care appropriate to his or her condition for timely initiated therapy or intervention.
In the parent application of which this is a continuation in part, there is described the discovery that very mild hypothermia is an indicator of imminent death in CHF patients. Hypothermia is generally d
Casscells, III Samuel Ward
Payvar Saeed
Astorino Michael
Board of Regents The University of Texas
Burgess, P.C. Tim L.
Jones Mary Beth
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