Thoracic aortic pulsatility decreases during hypovolemic shock: Implications for stent-graft sizing

Purpose: To investigate the thoracic aortic pulsatility during hypovolemic shock in an experimental porcine model. Methods: The circulating blood volume of 7 healthy Yorkshire pigs was gradually lowered until the subjects had lost 40% of their normal blood volume. Intravascular ultrasound was used to assess the aortic pulsatility in normovolemic and hypovolemic state at the level of the ascending and descending thoracic aorta. Results: The mean aortic pulsatility at the level of the ascending aorta decreased from 15.9%±7.2% (range 6.3%-25.7%) in normovolemia to 6.2%±2.8% (range 2.9%-10.7%, p=0.018) in hypovolemia. At the level of the descending thoracic aorta, the mean aortic pulsatility decreased from 8.7%±2.8% (range 4.4%-12.2%) at baseline to 5.6%×2.5% (range 1.5%-9.5%, p=0.028) in hypovolemia. The maximum mean aortic diameter, obtained in cardiac systole, was significantly smaller as well at both evaluated levels during hypovolemic shock compared with the mean diameter in normovolemia. Conclusion: The thoracic aortic diameter and pulsatility decreased significantly during hypovolemic shock in this porcine model, most impressively at the level of the ascending aorta. Electrocardiographically-gated imaging may not be necessary for hypovolemic patients with acute aortic disease requiring endovascular repair because of the minimal aortic pulsatility.