Tolerance to organic nitrates: evidence, mechanisms, clinical relevance, and strategies for prevention

Article Abstract:

Nitroglycerine has been used for years to treat angina pectoris, chest pain caused by coronary heart disease (inadequate blood flow to the heart). In recent years, its beneficial effects on other aspects of coronary and circulatory functions have been explored. Tolerance to nitroglycerine (resistance to its effects) has also been recognized for many years. Early studies suggested that nitroglycerine tolerance was of little clinical significance, but more recent work has shown otherwise. One study reported that only 24 hours of continuous nitroglycerine therapy induces tolerance to its effects on angina. Patients with congestive heart failure (inability of the heart to pump blood effectively) that is responsive to nitroglycerine develop nitrate tolerance after a short duration of therapy. Patients experiencing acute myocardial infarctions (heart attacks) benefit from the administration of nitroglycerine; the clinical significance of the development of tolerance is not clearly understood in this group of patients. However, people with unstable angina (frequent, severe chest pain that can occur at rest and frequently progresses to heart attack) seem to develop tolerance to continuous nitroglycerine, often with more serious consequences of their unstable angina. The rate of development of nitrate tolerance is unclear. Some studies suggest that half of patients so treated will develop tolerance, while other studies report that most, if not all, patients will experience tolerance. Preliminary studies seem to suggest that higher doses of nitroglycerine lead to greater risk for developing tolerance, but this finding needs to be confirmed. The mechanism of tolerance may be that certain molecules, known as sulfhydryl groups, are removed from cells by nitroglycerine; this theory has led to studies in which drugs that replace sulfhydryl groups are administered at the same time as nitroglycerine. Another suggested strategy to avoid the development of tolerance is intermittent dosing, in which drug-free periods occur at regular intervals (often every day), allowing for 'washout' of the old nitroglycerine so that new doses will still be effective. (Consumer Summary produced by Reliance Medical Information, Inc.)

Reports, Nitroglycerin, Drug tolerance

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Cardiovascular problems in pregnant women with the Marfan syndrome

Article Abstract:

Women with the Marfan syndrome should exercise caution in contemplating pregnancy and in carrying a baby to term. Marfan syndrome is an inherited condition that affects the development of muscle and bone. It often affects the arteries and valves of the heart. Researchers reviewed the current literature written about pregnant women with the Marfan syndrome. Most of these women developed serious heart complications late in their pregnancies. A few researchers have been successful in performing heart surgery on pregnant women with Marfan syndrome. The use of beta-blockers may be helpful in preventing heart problems in these women. Routine upper chest ultrasound scans during pregnancy also may be helpful in monitoring any heart problems that may develop. Children born to women with Marfan syndrome have a 50% chance of inheriting the gene causing this disease.

Health aspects, Causes of, Heart diseases, Pregnant women, Marfan syndrome

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Acute myocardial infarction associated with pregnancy

Article Abstract:

Heart attacks during or closely following pregnancy may be rare but serious. Researchers pooled 125 published reports of heart attacks associated with pregnancy. Twenty-one percent of the mothers died. While only 13% of the fetuses died, most of the fetuses that died had mothers that died. Forty-three percent of the heart attacks were associated with fat and cholesterol build-up in major blood vessel walls but 29% had normal heart blood vessels. Fetal safety should determine the choice of drug treatments. Vaginal delivery and cesarean delivery were equally safe.

Care and treatment, Heart attack, Pregnancy, Complications of, Pregnancy complications

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