Letter to the Editor: Holodiastolic Flow Reversal in the Descending Aorta: A Marker of Concomitant Acute Myocarditis and Aortitis in Children-A Case Series.

Holodiastolic flow reversal in the descending aorta can complicate acute myocarditis, indicating decreased cardiac output and possible aortitis. This pathology is related to the disappearance of the 'Windkessel' phenomenon, normally enabling the aortic walls to store potential energy during systole, which is released to the thoracic aorta blood flow during diastole. Furthermore, severe low-output syndrome or distributive shock can render the aortic walls incapable of exploiting their elasticity, which usually enhances the power of aortic blood flow. Moreover, the increased release of catecholamines, or their large-scale administration, causes vasoconstriction, mainly in the abdominal aorta and iliac-femoral branches. This increases peripheral resistance, but to a lesser extent in the supra-aortic branches, whose network becomes competitive and remains supplied with a sufficient amount of blood. From a pathological point of view, aortitis can be caused by an increase in the release of inflammatory cytokines, enhanced by ischemia resulting from a decrease in blood supply from the vasa vasorum, a consequence of shock. This pathology, easily detected by Echocardiography, must be considered an important sign of shock and is worthy of further investigation using 4D MRI aortic angiography.