Enlargement of heart’s left chamber tied to worse disease severity
More emergency visits, blood test abnormalities seen for these SCD patients
Enlargement of the left atrium, one of the heart’s upper chambers, is associated with a greater sickle cell disease (SCD) burden for patients, with more emergency department visits and blood test abnormalities, according to a new study from the U.S.
A larger left atrium is believed to be a proxy indicator of left ventricular diastolic dysfunction — a heart problem known to be tied to mortality in people with SCD.
“To the best of our knowledge, this is the first time a marker of diastolic dysfunction has been shown to correlate with increased sickle cell disease burden as indicated by worsening laboratory markers and increased healthcare utilization,” the researchers wrote.
According to the team, “this study highlights the potential utility of using left atrial size as a marker of disease severity in SCD.”
The study, “Measurement of left atrial size as a predictor of severity of illness in sickle cell disease,” was published in The American Journal of Emergency Medicine.
Finding new ways to predict disease severity in SCD
Sickle cell disease is caused by mutations in the HBB gene that give rise to a faulty version of hemoglobin, the protein that helps red blood cells carry oxygen. This leads to misshapen and rigid red blood cells that don’t pass easily through blood vessels and that undergo premature hemolysis, or destruction.
Patients commonly experience red blood cell shortages, known as anemia. Further, compromised oxygen delivery to tissues due to blocked blood flow results in episodes of severe pain, called vaso-occlusive crises, which may require hospitalization.
These problems can cause damage to several organs, including the heart and lungs. Among the complications that can arise in SCD is diastolic dysfunction of the left ventricle (LV), one of the heart’s lower chambers.
The LV receives oxygen-rich blood from the lungs by way of the heart’s left atrium. It then pumps that blood out to the rest of the body. In between pumps, the LV is supposed to relax and fill up with new incoming blood from the left atrium.
Diastolic dysfunction happens when this relaxation is impaired, and the LV can’t fill up with blood as it should. Ultimately, that can cause blood pressure in the heart to rise, and lead to heart failure.
LV diastolic dysfunction has been identified as a risk factor for mortality in SCD patients, so it is important to understand its relationship to other indicators of SCD disease burden.
However, traditional ways of directly measuring this complication involve a “specialized and time-consuming process,” the researchers wrote.
Researchers used heart ultrasound data to assess heart enlargement
A proxy way of evaluating LV diastolic dysfunction is to instead look for enlargement of the left atrium using a heart ultrasound, or echocardiography. When the LV is having trouble filling up, pressure in the atrium might also increase to compensate, causing it to enlarge.
In this study, a team of researchers from the University of Illinois sought to determine any association between left atrium enlargement and other measures of SCD disease burden. To that end, the researchers examined data from 129 SCD patients, ages 15-45, enrolled in a patient registry at a hospital in their state.
Most were African American individuals (98%), and about half (52%) were women. “The age, race, and sex of the study subjects were representative of the usual adult sickle cell patient presenting to our [emergency department] for vaso-occlusive crises,” the researchers wrote.
Overall, 88 patients (about 68%) had a normal left atrial volume, assessed via an echocardiogram, while 41 (about 32%) had left atrial enlargement.
A higher percentage of those with left atrial enlargement — 34% vs. 17% — were considered frequent emergency department users, defined as having three or more visits per year, compared with those without such enlargement.
In this retrospective analysis, sickle cell patients with [left atrial enlargement] had significantly more annual [emergency department] visits, more hemolysis and lower average hemoglobin levels than sickle cell patients with normal left atrial volumes.
Moreover, the left atrial enlargement group had significantly lower median blood levels of hemoglobin (8.57 vs. 9.47 g/dL), reflecting more severe anemia, and a higher median hemolytic index (0.44 vs. -0.21), indicating more red blood cell destruction.
“In this retrospective analysis, sickle cell patients with [left atrial enlargement] had significantly more annual [emergency department] visits, more hemolysis and lower average hemoglobin levels than sickle cell patients with normal left atrial volumes,” the team wrote.
According to the researchers, the study supports the potential use of left atrial size in SCD patients as a marker of disease severity. Regular screening for LV diastolic dysfunction could thus help doctors monitor patients for SCD-related organ dysfunction, the team noted.
Among the study’s limitations, the scientists noted the maximum age of the patients was 45, meaning that older individuals with more severe heart involvement were not included.
“Further studies across hospital systems with larger sample sizes are needed to validate our findings,” the team concluded.
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