Posted on 02/26/2004 1:46:13 PM PST by neverdem
WASHINGTON, Feb. 25 — High blood pressure in the lungs has been identified as a major risk factor for death in adults with sickle-cell disease, and all people with the disease should be screened for this complication, according to a study being published Thursday.
Almost one-third of adult sickle-cell patients who were screened with a noninvasive ultrasound method were found to have moderate to severe pulmonary hypertension and high blood pressure in the lungs that had not previously been detected, the study found.
The results from the tests confirm earlier suggestions from studies of patient records that pulmonary hypertension is present in 20 percent to 40 percent of sickle-cell patients and poses a major threat of death, the researchers said in their paper, which appears in the Feb. 26 issue of The New England Journal of Medicine. The researchers, from the National Institutes of Health and the Howard University Center for Sickle Cell Disease, said the findings were so striking that all patients with sickle cell should be regularly screened.
In addition, they said, patients with even mild to moderate pulmonary hypertension should have the condition treated because the added risk of death appears high even in less severe cases.
"In sickle-cell patients, this appears to be the No. 1 predictor of sudden death syndrome," said the study's lead author, Dr. Mark T. Gladwin of the health institutes' Magnuson Clinical Center. "This is when a patient who appears to be doing well suddenly falls ill and dies."
"Even people with mild pulmonary hypertension caused by sickle-cell disease are at risk of sudden death," Dr. Gladwin said in an interview.
Pulmonary hypertension is high blood pressure in the arteries that supply the lungs, a condition that results in the vessels narrowing and their walls thickening to restrict blood flow. When this condition is caused by a pre-existing disease, like sickle cell, it is known as secondary pulmonary hypertension.
In the new study, researchers followed 195 sickle-cell patients, 82 men and 113 women, for two years. The average age of the patients was 37. The researchers used Doppler echocardiology, a noninvasive technique that uses sound waves to monitor the heart. The technique measures blood flow velocity to deduce pulmonary artery pressure.
The researchers found that 32 percent of the patients had mild to severe pulmonary hypertension. After a follow-up period of 18 months, during which 5 patients left the study, 20 percent of the 62 participants with pulmonary hypertension died. Of the 128 participants without demonstrated hypertension, only 2 died.
Dr. Oswaldo Castro of Howard University, an author of the study, said that the research proved that earlier studies had not exaggerated the risk of a sickle cell-pulmonary hypertension link. "We now know this situation is real and can take steps to do something about it," he said.
Sickle-cell disease is an inherited blood disorder that affects hemoglobin, the oxygen-carrying protein of red blood cells. This flawed hemoglobin causes red cells to stiffen and to take on jagged shapes, which blocks blood vessels and causes vascular inflammation leading to damaged organs.
The disease worldwide affects millions of people, primarily those with ancestors from Africa, the Mediterranean and India. In the United States, it afflicts an estimated 80,000 people.
Dr. Gladwin estimated that perhaps 60,000 adult patients in this country should be regularly tested and monitored for pulmonary hypertension.
The researchers said that the cause of the problem appeared to be excess free hemoglobin in the blood from the breakdown of red blood cells seen in sickle-cell disease. This hemoglobin scavenges nitric oxide, a chemical that dilates blood vessels, and another red blood cell product, arginase. Arginase blocks the activity of a chemical called arginine that is crucial for making nitric oxide.
In terms of treatment, the authors recommended that patients with pulmonary hypertension first be aggressively treated for their sickle-cell disease to keep it under control and reduce the amount of free hemoglobin. Many patients take the drug hydroxyurea, which helps produce a healthier form of hemoglobin and enhances the availability of nitric oxide. Other therapies include blood transfusions and inhaled nitric oxide gas.
The researchers also suggested that doctors enroll sickle-cell patients in trials involving drugs that can increase nitric oxide, like oral arginine, and drugs approved to treat primary pulmonary hypertension, like prostacyclins and calcium-channel blockers.
Because of the role of free hemoglobin in causing the condition, the paper suggested that researchers examine patients with thalassemia, hereditary spherocytosis and other types of anemias resulting from red-cell destruction, to see if they are also at increased risk of pulmonary hypertension and death.
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