1356644 - Acute low cardiac output syndrome following contrast administration in a pediatric patient with left ventricular outflow obstruction

A 12-year-old male with aortic valve hypoplasia, remote history of subaortic membrane resection and residual moderate left ventricular outflow obstruction, presented for routine non-sedated cardiac magnetic resonance (CMR) evaluation. A combination of breath-holds and free-breathing acquisitions was performed uneventfully. A bolus dose of Gadobutrol (0.02ml/kg) was injected 15 minutes prior to the end. There were no patient complaints during contrast acquisitions. Yet, while being moved out of the scanner, he appeared pale with cool extremities, weakness and remarkably wet clothes. Upon questioning, he reported profound perspiration and dizziness immediately following contrast administration.


Diagnostic Techniques and Their Most Important Findings:

Emergency reaction plan was activated, patient was transferred to zone 2 and placed on continuous cardiorespiratory monitoring. He was alert, tachycardic [(98 beats per minute, (bpm)], hypotensive (76/35mmHg), with oxygen saturation of 88% on room air. Physical examination showed hyperactive precordium with a long low-grade systolic murmur, a diastolic rumble and prolonged capillary refill. There were no signs of respiratory distress or skin rash. Hypoxia was attributed to reactive peripheral vasoconstriction and was reversed once the patient was rewarmed and hydrated. He received judicious amount of crystalloids until the blood pressure was stabilized at an acceptable level for age. Electrocardiogram differed from baseline in the form of diffuse ST segment depression and T wave inversion. Laboratory evaluation revealed elevated troponin I. CMR review revealed an average heart rate in the low 90’s prior to contrast administration versus 100-110bpm during the phase contrast and viability parts. The aortic valve annulus was severely hypoplastic (z score -6.3) with restricted leaflet motion (aortic valve area 0.7cm/m² via planimetry), at least moderate stenosis (peak velocity 4m/s) and mild regurgitation (regurgitant fraction 13%). There was a small subaortic membrane adjacent to the valve annulus. Ventricular function was hyperdynamic (LVEF 78%, RVEF 62%) with no wall motion abnormalities. Late gadolinium enhancement imaging demonstrated linear mid-wall fibrosis at the basal and mid- infero-septal and inferior wall segments. Patient was transferred to the ward where his serial ECGs and myocardial enzymes normalized over the course of a 24-hour admission.


Learning Points from this Case:

We aim to raise awareness of the possibility of low cardiac output syndrome in cases that may have limited cardiac reserve to compensate for acute vasodilation and subsequent hypotension following gadolinium-based contrast agents (GBCA) administration. In contrast to hypersensitivity induced coronary spasm, our patient experienced acute coronary hypoperfusion due to systemic vasodilation in the setting of severe valvar and sub-valvar aortic stenosis. Lack of profound hypersensitivity reactions like respiratory manifestations may delay diagnosis and timely intervention.