Optical coherence tomography for the evaluation of asymmetric cardiac allograft vasculopathy in a child

Patterns of Early Coronary Artery Changes in Pediatric Heart Transplant Recipients Detected Using Optical Coherence Tomography

BACKGROUND

Cardiac allograft vasculopathy, the leading cause of graft failure in pediatric heart transplant recipients, is characterized by diffuse and concentric coronary intimal thickening. Early treatment yields better outcomes. While coronary angiography is the standard for cardiac allograft vasculopathy screening and diagnosis, it only identifies luminal narrowing, which occurs in more severe disease. Coronary optical coherence tomography (OCT) is a high-definition intravascular imaging modality that may offer earlier diagnosis. We used OCT to investigate coronary intimal thickening in pediatric transplant recipients and examined its (1) location (ie, vessel type and location) and (2) nature (ie, characteristics of cross-sectional and longitudinal thickening).

METHODS

Sites collected coronary angiography and OCT data from participants (N=258 vessel segments from 73 individuals; median age: 11.5 years [8.4-15.3]; 55% male). Images were collected from the left anterior descending, left circumflex, and right coronary arteries, and location (ie, proximal, middle, and distal) were classified using coronary angiography.

RESULTS

OCT identified 32 vessel segments meeting criteria for significant thickening, 88% of which were angiographically silent. Longitudinal thickening was segmental rather than global in 88%, and cross-sectional thickening was 48% eccentric and 52% concentric. Intimal thickening prevalence and severity measures did not consistently differ between coronary artery type (P=1.000) or location (P=0.248) but increased with time since transplant and age at transplant and OCT procedure.

CONCLUSIONS

In pediatric transplant recipients, we observed a surprisingly high prevalence of segmental and eccentric intimal thickening. Insights from intravascular imaging suggest these patterns of coronary vascular changes may precede overt cardiac allograft vasculopathy. Identifying early changes may offer opportunity for enhanced surveillance and earlier intervention.

Feasibility of Real-Time Myocardial Contrast Echocardiography to Detect Cardiac Allograft Vasculopathy in Pediatric Heart Transplant Recipients

BACKGROUND

Cardiac allograft vasculopathy (CAV) is an important adverse prognostic factor for pediatric heart transplant (HT) recipients. Invasive coronary angiography (ICA) is the gold standard for CAV detection but lacks sensitivity for early microvascular changes and cumulative radiation exposure is of concern. Real-time myocardial contrast echocardiography (RTMCE) using ultrasound enhancing (contrast) agents performed during dobutamine stress echocardiography (DSE) can assess myocardial function, perfusion, and microvascular integrity. The objective of this study was to determine the safety and feasibility of RTMCE during DSE to detect CAV in a pediatric HT population.

METHODS

HT patients 10-21 years of age were recruited to undergo DSE with RTMCE to determine technical feasibility, test tolerability and adverse event rate, and detection of perfusion defects compared with ICA-detected CAV. Thirty-six patients from two centers were enrolled, with a mean age 13.5 ± 4.3 years; 21 (58%) were male. Wall motion and myocardial perfusion were qualitatively assessed and compared with ICA findings of CAV. Myocardial blood flow (MBF) at rest and peak stress was quantified, and myocardial blood flow reserve (MBFR) was defined as the ratio of peak to rest MBF.

RESULTS

Five (14%) patients had CAV by ICA, two with obstructive disease and three with mild CAV. Real-time myocardial contrast echocardiography was feasible in 32 (89%) patients. Three patients had wall motion defects, including one with a mixed defect and two with fixed defects. A perfusion abnormality was present in five patients, two of whom had obstructive CAV and one with mild CAV. Sensitivity and specificity of RTMCE for CAV detection were 60% and 94%, respectively, and diagnostic accuracy was 89%. MBFR assessment was feasible in 20 (63%) patients. The mean MBFR was 3.4 ± 0.7. Patients with CAV had lower MBFR than those without (2.0 ± 0.2 vs 3.7 ± 0.8; P < .01). There were no serious adverse events related to RTMCE.

CONCLUSIONS

Dobutamine stress RTMCE appears to be safe and feasible for the assessment of CAV in pediatric HT recipients. Further assessment is warranted to determine whether this noninvasive technique could provide a reliable alternative to ICA.