Heart problems are fairly common in young adults with sickle cell disease, but physicians don't fully understand why. The researchers demonstrated that lower oxygen saturation in the blood was linked to the heart structure seen in the 44 children studied.
Sickle cell disease is an inherited blood disorder affecting red blood cells, which contain hemoglobin, the substance that carries oxygen from the lungs to all parts of the body. In patients with this disease, red blood cells contain an abnormal type of hemoglobin that causes the normally round, flexible red blood cells to become stiff and sickle- or crescent-shaped. The sickle cells can't pass through tiny blood vessels, which can prevent blood from reaching some tissues and can result in tissue and organ damage, pain and stroke.
In addition, sickle cells are short lived and lead to a shortage of red blood cells and anemia, which make the heart grow bigger because it has to work harder, says Mark C. Johnson, MD, associate professor of pediatrics at Washington University School of Medicine and first author of the study.
In this study, the first to analyze sleep studies and echocardiograms of children with sickle cell disease, these heart abnormalities were found in the left pumping chamber, or left ventricle, of the children's hearts. The findings included an enlarged left ventricle, called ventricular hypertrophy, and abnormal blood filling of the left ventricle, called diastolic dysfunction. Both are associated with early death in adults with sickle cell disease, but the meanings of the same results in children are unclear.
"This suggests that the beginning of adult heart disease may start in children, but we need to follow these patients longitudinally to strengthen the meaning of the findings," says Michael R. DeBaun, MD, a Washington University sickle cell disease specialist at St. Louis Children's Hospital and senior author of the study, published online in Blood First Edition April 8, 2010.
"Many researchers assumed it was the anemia alone that makes the heart enlarge, but this study suggests it's not that simple," Johnson says.
Researchers began the study thinking that the abnormalities in the left ventricle, the heart's main blood-pumping chamber, would be the result of sleep-disordered breathing, such as sleep apnea, commonly found in children with sickle cell disease. Sleep-disordered breathing has previously been associated with left ventricle hypertrophy and with diastolic dysfunction in children and adults. But only about one-fifth of the children had some evidence of obstructive apnea hypopnea, or recurrent episodes of upper airway collapse and obstruction during sleep.
Researchers also thought they would find lower oxygen saturation while patients were sleeping compared to when they were awake. However, the average oxygen saturation while asleep and awake were similar. Only about one-fourth of patients had average oxygen saturation values below normal.
The echocardiograms showed that 46 percent of participants had left ventricle hypertrophy in which the chamber of the left ventricle was enlarged. The research team's analysis showed that for every 1 percent drop in oxygen saturation, there was a measurable increase in the mass of the heart's left ventricle.
"The average oxygen saturation of 97 percent in these children is in a normal range, but the patients with slightly lower levels had enlarged hearts," Johnson says. "A relatively small change in oxygen levels caused a big change in the heart. That's what makes us think there's something under the surface that we don't quite understand yet."
The team also measured an indicator of pulmonary hypertension, or high blood pressure in the lungs, the major cause of death in adults with sickle cell disease. When the pulmonary hypertension level is raised in adults with sickle cell disease, it is a strong predictor of death within 24 months. However, despite the strong association between pulmonary hypertension and sleep abnormalities, no such association was demonstrated in this study, DeBaun says.
Johnson and DeBaun say more sleep and cardiac studies are needed to confirm the association of left ventricle abnormalities with low blood oxygen levels. In the future, the researchers plan to look at other indicators to find potential new therapies to prevent progression of the disease.
Johnson M, Kirkham F, Redline S, Rosen C, Yan Y, Roberts I, Gruenwald J, Marek J, DeBaun M. Left Ventricular Hypertrophy and Diastolic Dysfunction in Children with Sickle Cell Disease are Related to Asleep and Waking Oxygen Desaturation. Blood First Edition. Prepublished online April 8, 2010.
Funding for this study was provided by the National Heart, Lung, and Blood Institute.
Washington University School of Medicine's 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked fourth in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.
Beth Miller | EurekAlert!
Serious children’s infections also spreading in Switzerland
26.07.2017 | Universitätsspital Bern
New vaccine production could improve flu shot accuracy
25.07.2017 | Duke University
Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers
Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...
Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.
At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...
3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects
A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
26.07.2017 | Event News
21.07.2017 | Event News
19.07.2017 | Event News
26.07.2017 | Earth Sciences
26.07.2017 | Materials Sciences
26.07.2017 | Physics and Astronomy