Adenosine Stress with Quantitative Perfusion and Dobutamine CMR in Children & Young Adults with Anomalous Origin of the Right Coronary Artery

Background: Anomalous aortic origin of the right coronary artery (AAORCA) with interarterial or intramural course can be associated with ischemia and sudden cardiac death. Pharmacological stress is often used for risk stratification in these patients.

Methods: To assess if quantitative myocardial blood flow (MBF) or perfusion reserve (MPR) under adenosine stress in pediatric and adolescent patients with AAORCA reveals consistent occult ischemia in comparison to qualitative analysis or dobutamine stress testing.

Results: Twenty-five patients (mean age 14 + 3 years, 44% female) were included. Biventricular volumetric analysis was normal (Table 1, mean LVEF 60% + 5.9, RVEF 55.9% + 5.0) in all patients. On qualitative assessment, no inducible perfusion defects were observed with adenosine stress. Quantitative analysis demonstrated mean global MBF of 1.72 + 0.49 mL/g/min at rest, increasing to 3.33 + 0.76 mL/g/min with adenosine. Mean global MPR was 2.31 + 0.72, with RCA-territory MPR averaging 2.28 + 0.95. Adequate augmentation of MBF was observed in the RCA territory, with similar augmentation between RCA (mean stress MBF 3.26 + 0.84 mL/g/min) and LCA territories (mean stress LAD MBF 3.38 + 0.97 mL/g/min) (p = 0.36) (Table 2). Analysis of perfusion bullseye plots did not reveal segmental perfusion deficits. Dobutamine stress did not demonstrate inducible wall motion abnormalities.

Conclusion: Quantitative perfusion did not reveal any systematic occult RCA ischemia in these patients in comparison to standard qualitative analysis or dobutamine stress testing. The combined approach, however, may provide a more sensitive pharmacological approach to testing the individual patient. Larger studies are warranted in this group.

Table 1: Basic Characteristics

Characteristics	Mean + SD
Age (years)	14 + 3.0
Weight (kg)	57.1 + 27.2
BSA (m2)	1.5 + 0.3
Male	14 (55%)
LVEF (%)	60.1 + 5.9
RVEF (%)	55.9 + 5.0

BSA: Body surface area, LVEF: Left ventricular ejection fraction, RVEF: Right ventricular ejection fractionTable 2: Myocardial Perfusion Parameters

Parameters	Overall	RCA	LAD	LCx	p-value
Mean MBF rest (ml/g/min)	1.72 + 0.49	1.76 + 0.60	1.68 + 0.64	1.72 + 0.50	0.28
Mean MBF stress (ml/g/min)	3.33 + 0.76	3.26 + 0.84	3.38 + 0.97	3.33 + 0.70	0.36
Mean MPR	2.31 + 0.72	2.28 + 0.95	2.38 + 0.95	2.27 + 0.75	0.15

MBF: Myocardial blood flow, MPR: Myocardial perfusion reserve, RCA: Right coronary artery, LAD: Left anterior descending artery, LCx: Left circumflex artery