Standard heart ultrasound may aid cardiac sarcoidosis screening
TTE worked best when combined with symptoms and ECG data
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A standard heart ultrasound scan, called transthoracic echocardiography (TTE), may help screen for cardiac sarcoidosis when used alongside symptoms and heart rhythm tests, a study found. Adding heart strain imaging or three-dimensional echocardiography did not appear to significantly improve its overall diagnostic value.
Although TTE had low sensitivity, meaning it missed many cases of cardiac sarcoidosis, certain abnormal TTE findings were highly specific for the disease and could help identify patients who may need more advanced imaging.
TTE alone can miss cardiac sarcoidosis
“Comprehensive echocardiography remains a useful screening tool among sarcoidosis patients with suspected cardiac [heart] involvement,” the researchers wrote.
The study, “Evaluation of contemporary echocardiography for the detection of cardiac sarcoidosis,” was published in Echo Research & Practice.
In sarcoidosis, the immune system becomes overactive and forms small clumps of inflammatory cells called granulomas, which can damage organs over time. Cardiac sarcoidosis occurs when these granulomas build up in the heart, disrupting its normal function and affecting how it beats and pumps blood.
TTE is a standard ultrasound scan of the heart obtained through the chest wall. It has been used to diagnose cardiac sarcoidosis, including under 2014 Heart Rhythm Society criteria, in which the only echocardiography-based criterion is an unexplained left ventricular ejection fraction (LVEF) below 40%. LVEF is the percentage of blood the heart’s lower left chamber, or left ventricle, pumps out with each heartbeat.
However, because “most CS [cardiac sarcoidosis] patients have a normal LVEF, the sensitivity of [TTE] for detecting CS may be as low as 25–32%,” the researchers wrote. A test’s sensitivity refers to its ability to correctly identify people with a given disease (true positives).
Researchers tested added heart imaging measures
Here, a team of researchers in the U.K. evaluated whether adding strain imaging, which measures how well the heart muscle changes shape during each beat, and 3D echocardiography, which creates three-dimensional images of the heart, to TTE could improve cardiac sarcoidosis diagnosis.
The researchers also compared TTE with other tests, such as an ECG, with or without Holter monitoring, which continuously records the heart’s rhythm, typically for 24-48 hours; heart MRI; and fluorodeoxyglucose PET, which uses a small amount of a radioactive tracer to look for areas of active inflammation.
A total of 181 people referred for evaluation of suspected cardiac sarcoidosis were included in the analysis. Their average age was about 55 years, and 59% were men. Most (92%) had sarcoidosis outside the heart, especially in the lungs. More than half, 106 of 181 patients, were diagnosed with cardiac sarcoidosis after testing.
On TTE, four parameters were linked to cardiac sarcoidosis. These included an enlarged left ventricle cavity, LVEF below 50%, thinning at the base of the wall between the heart’s ventricles, and abnormal motion in multiple regions of the heart muscle.
In the study’s TTE model, the presence of any of these four factors was classified as probable cardiac sarcoidosis. The model showed high specificity (96%), meaning that it could correctly identify most people without cardiac sarcoidosis, called true negatives. It also had a high positive predictive value (92%), meaning most positive cases were true cases.
However, it had low sensitivity (33%), meaning that its ability to correctly identify cases of cardiac sarcoidosis was poor, and many true cases would be missed. Adding data from heart strain or 3D echocardiography did not significantly improve the overall diagnostic ability of TTE.
Strain imaging measures how much the heart’s muscles contract and relax, with lower values indicating worse heart function. Certain strain cutoffs, including left ventricular global longitudinal strain greater than −13% and left ventricular global circumferential strain greater than −15%, showed high specificity, about 90%, for cardiac sarcoidosis.
Incorporating these strain parameters improved the sensitivity of TTE from 33% to 54%, but specificity dropped from 96% to 71%, “failing to improve the overall diagnostic ability of this modality,” the researchers wrote.
3D imaging did not improve diagnosis
Only half of the patients had 3D images of their heart due to technical limitations such as poor image quality, limited imaging windows, or irregular heart rhythms.
“Interestingly, significant differences in 3D strain values were not observed in those with and without CS,” the team wrote. “This is most likely explained by the reduced number of feasible studies and lower reproducibility of 3D strain measurements.”
However, a screening approach that combined symptom assessment, ECG or Holter data, and the probable cardiac sarcoidosis TTE model had 90% sensitivity for cardiac sarcoidosis.
Among patients without symptoms, normal rhythm data and a normal TTE made cardiac sarcoidosis unlikely, but did not fully rule it out. A small proportion of patients without symptoms and with normal tests still had cardiac sarcoidosis, showing that no single test can identify all true cases. In this cohort, heart MRI had the highest sensitivity, at 99%.
While patients came from a single center specialized in sarcoidosis, where more cardiac sarcoidosis diagnoses may be expected, this study suggests that TTE is “a useful screening tool” that can help identify patients with suspected cardiac sarcoidosis “who may benefit from further detailed imaging,” the researchers concluded.
