Optical coherence tomography (OCT) can detect coronary vascular changes beyond the capabilities of angiography in pediatric heart transplant recipients, according to a study published July 18 in JACC: Cardiovascular Imaging.
This intravascular imaging technique could be used to inform the medical management of these patients and potentially provide an earlier diagnosis of cardiac allograft vasculopathy (CAV), a leading cause of graft failure and death for this population.
“After the diagnosis of CAV, graft survival at six years ranges between 42 percent and 48 percent,” wrote lead author Eimear McGovern, MB, with British Columbia Children’s Hospital in Vancouver, and colleagues. “This reflects the difficulties encountered with managing this condition and the need for improved early diagnosis and earlier targeted treatment.”
Researchers from centers in Canada, Spain and Germany performed both angiography and OCT in 110 cases. Patients were 11.9 years old on average and a median 6.5 years removed from cardiac transplantation. OCT findings were analyzed on the basis of two measurements the authors considered to have clinical relevance: intima thickness and the ratio of the intima/media cross-sectional area (I/M CSA).
A total of 26 cases showed evidence of abnormal intima size (greater than 0.25 mm) while 11 cases had severe intima thickening (greater than 0.4 mm). Importantly, angiographic findings were normal for eight of the children with severe thickening, which has been linked to inflammatory states from chronic illness and infectious disease and may be a precursor to CAV. However, the authors said additional serial imaging studies are needed to confirm whether intima thickening progresses over time and represents a harbinger for CAV.
In this study, the I/M CSA ratio was significantly higher for children diagnosed with CAV, while maximal intima thickness was greater for patients with current or previous antibody-mediated rejection.
“Intimal thickening is prevalent in this population and is often angiographically silent,” McGovern et al. wrote. “Our study demonstrated that, even in cases of severe intima thickening, angiography results were most often normal. OCT is readily able to identify structural coronary changes that have not become manifest in the form of lumen narrowing.”
The authors also found OCT findings prompted a change in medical management in 17 percent of cases. These patients had normal angiographic findings but higher than normal I/M CSA ratios and/or intima thicknesses. Patients with maximal intima thickness above 0.25 mm were four times more likely to have a change in medication versus those below that threshold.
The authors said there is now “a growing body of evidence” supporting that statins are safe for children. This finding, coupled with the fact that more intima thickening was observed in patients not taking statins, suggests future heart transplant guidelines should consider adding recommendations for statin therapy, they added.
One limitation of the study is it didn’t have a control group of healthy children to compare artery anatomy. The authors also acknowledged it’s tricky to pin down average or reference anatomical measurements in the pediatric population, which contains a wide variety of ages and sizes.