Circadian variations in myocardial ischemia: implications for management
Article Abstract:
Modern methods of monitoring physiological variables of patients during their normal daily activities (ambulatory monitoring) provide the opportunity to record the daily rhythms of heart function. In particular, changes in myocardial ischemic activity (periods when the heart receives insufficient oxygen) throughout the day can be evaluated. It is known that myocardial ischemia is highest between 6:00 a.m. and 12:00 noon, and that similar peaks also occur for heart attack, stroke (sudden cessation of blood to the brain because of a clot or hemorrhage), and sudden death. A review is presented of the circadian (daily) rhythms of myocardial ischemia and the possible physiological bases for these changes. Activity of the sympathetic nervous system, which mediates vascular constriction, is high in morning hours, leading to increased constriction of coronary blood vessels when demand (because of activity levels and physiological factors) is greatest. Other morning events conspire to reduce the supply of oxygen to the heart: these include increased coronary muscle tone, increases in blood cortisol, and an increased tendency for blood platelets (essential for clotting) to aggregate. These are reviewed in detail. Ideal therapy to treat myocardial ischemia should concentrate on the hours when ischemia is most likely. Such agents could include nitroglycerin taken immediately upon awakening; a beta-blocking drug (which blocks the action of other chemicals that stimulate cardiac activity) taken each night; calcium antagonists, which do not seem to affect the circadian pattern of ischemia; aspirin, whose role in preventing ischemia is not understood; and plasminogen activators, drugs that increase the rate of clot dissolution. Awareness of circadian triggers for morning myocardial ischemia should improve control of cardiovascular disease, even if the physiological bases for such oscillations have not been completely described. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: JAMA, The Journal of the American Medical Association
Subject: Health
ISSN: 0098-7484
Year: 1991
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Breast cancer after Hodgkin disease: hope for a safer cure
Article Abstract:
Doctors should consider treating all patients with Hodgkin's disease with chemotherapy followed by low-dose radiation treatment delivered only to the lymph nodes that are cancerous. In the 1970s and 1980s, only high-dose radiation treatment was used, and all lymph nodes were irradiated. However, this has been shown to increase the future risk of breast cancer in female patients.
Publication Name: JAMA, The Journal of the American Medical Association
Subject: Health
ISSN: 0098-7484
Year: 2003
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Valvular dysfunction and carotid, subclavian, and coronary artery disease in survivors of Hodgkin lymphoma treated with radiation therapy
Article Abstract:
Radiation treatment for Hodgkin's disease may damage the heart, especially the heart valves, according to a study of 415 people who received radiation treatment for Hodgkin's disease during childhood. These patients were 8 times more likely to require heart valve replacement than the general population. High radiation doses can also increase the risk of coronary artery disease.
Publication Name: JAMA, The Journal of the American Medical Association
Subject: Health
ISSN: 0098-7484
Year: 2003
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