(Great Britain—The Practitioner, October 1999, p. 746.) Although atrial fibrillation occurs in up to 2.4 percent of persons older than 50 years of age, many cases are asymptomatic and undiagnosed. Patients with atrial fibrillation are at increased risk of stroke, thromboembolism, heart failure and decreased exercise tolerance. In addition to confirming the diagnosis, possibly with a 24-hour Holter monitor in cases of paroxysmal atrial fibrillation or sick sinus syndrome, the initial evaluation includes a search for conditions such as thyrotoxicosis, alcoholism, or excessive caffeine intake that may precipitate or exacerbate the condition. The choice of treatment depends on patient characteristics and coexisting conditions. When atrial fibrillation is associated with hypertension, ischemic heart disease or thyrotoxicosis, the patient may benefit from ß-blockade. When left ventricular function is poor, digoxin and amiodarone may be the drugs of choice. In addition to antiarrhythmic therapy, patients with atrial fibrillation require prophylaxis for thromboembolism. In elderly patients, aspirin may be sufficient, but many other patients with atrial fibrillation benefit from warfarin therapy. Cardioversion with drugs or synchronized direct current shock is most likely to be successful in younger patients and those with short duration of fibrillation.
(Great Britain—The Practitioner, September 1999, p. 672.) Fifth disease, or erythema infectiosum, is the most familiar clinical manifestation of parvovirus infection. The infection is caused by the B19 strain, one of the smallest known pathogenic viruses. Although other parvovirus strains infect animals, the B19 strain replicates only in human erythrocyte precursors. About one half of the population have IgG antibody by 15 years of age, and more than 90 percent have been exposed to infection by old age. Infection is believed to be by droplet spread. In children, the initial infection includes nonspecific influenza-like symptoms followed by the classic “slapped cheeks” rash with circum-oral pallor. The secondary rash on the trunk and arms has a lacy reticular pattern and may be trivial or persist for weeks. In adults, the facial rash is uncommon, but joint symptoms may be severe. In rare cases, parvovirus infection causes transient aplasia, especially in children with underlying hematologic conditions such as sickle cell anemia or hereditary spherocytosis. In pregnant women, parvovirus infection is particularly dangerous between 20 and 28 weeks of gestation. Up to 10 percent of such cases result in stillbirth, but infants who survive do not appear to have any sequelae or increased vulnerability to hematologic disorders. No treatments are currently available for parvovirus infection, but a vaccine is in development.
The Role of Tricyclic Antidepressants
(Australia—Australian Family Physician, August 1999, p. 809.) The new generation of antidepressant medications targeting serotonin metabolism has rapidly become the predominant form of therapy in depressive illness. Tricyclic antidepressant medications (TCAs) are still important pharmacologic weapons, particularly for patients with severe depression and those vulnerable to side effects or drug interactions associated with the newer antidepressant medications. Tricyclic antidepressants may be more effective in treatment of severe depression with marked psychomotor changes, withdrawal from normal activities, insomnia and excessive guilt. Because they do not affect the cytochrome P450 system, TCAs have fewer potential drug interactions than newer antidepressants. The side effects of TCAs include anticholinergic, cardiac and neurologic symptoms, which may be advantageous in selected patients (e.g., in management of insomnia). Newer antidepressants generally have less serious side effects, but some patients may benefit from changing to TCAs if headache, gastrointestinal upset, anorexia and agitation are predominant or if the serotonin syndrome occurs.
How Effective Is Pneumococcal Vaccine?
(Canada—Canadian Family Physician, October 1999, p. 2381.) Concerns about clinical efficacy may explain why only about one third of eligible elderly persons receive pneumococcal immunization. A review of the literature found more than 250 pertinent articles, including 13 high-quality clinical trials that included more than 65,000 patients. The net risk reduction for systemic pneumococcal infection from vaccination was estimated to be more than 80 percent for serotypes included in the vaccine and overall to be about 73 percent. Studies of institutionalized patients did not indicate reduced efficacy compared with other elderly persons. The authors estimated that 2,520 elderly persons would need to be vaccinated to prevent one case of pneumococcal bacteremia per year.