H.24A Solving the Challenge to Aspirating Blood from a Small Vessel
Several endovascular procedures emerging in widespread use involve aspirating blood from a small vessel 20-65 cm away. For instance, adrenal vein sampling (AVS) is a procedure performed to determine which adrenal gland is responsible for disease in primary hyperaldosteronism. The demand for this procedure is growing exponentially. Other procedures involving small vessel aspiration over a distance include procedures like parathyroid sampling. Research and emerging applications exist, too, such as aspirating blood for measurement of free testosterone in spermatic veins and rare but critical diagnostic procedures such as renin sampling.
Emory IR continues to represent one of the highest volume practices for AVS in the United States. AVS is an outpatient minimally-invasive image-guided procedure performed to determine if primary hyperaldosteronism is due to the left adrenal gland, the right adrenal gland, or both adrenal glands. The presence of a nodule on one of the adrenal glands is not enough to determine that the “tumor” (the nodule) is the source of the disease. We often point out to patients that adrenal nodules are like moles on the skin. While in roughly half of patients they may be the source of hormone production for high blood pressure, in the other half, they are simply present but the disease is due to both adrenal glands. Rarely, a microscopic nodule in the other adrenal gland is the source of disease. In this final case, getting it wrong is devastating to a patient – removing the side where the nodule is seen (but turns out not to be active) renders the patient incurable. No solution exists at present whereby both adrenal glands can be removed and patients with bilateral disease face the return to disappointment that no ideal solution exists.
For this proposal, we seek to address the absence of highly skilled proceduralists who can perform AVS. Emory IR is the largest academic IR group in North America (and possibly the world) and the demand is very high for us. Many IR’s are not able to perform this procedure. The challenges include: finding the adrenal veins (with the right often being harder to find and anatomic variability being high), confirming one is in the adrenal veins, staying in the adrenal veins (respiratory motion often makes this challenging), and getting blood out of the adrenal veins. The focus of this project is on challenging in aspirating blood out of a small (1-2 mm) vessel with high tortuosity from roughly 65 cm away. To date, no ideal catheter exists for this purpose. The main catheter used involves a “Sim 1” with sideholes manually punched at roughly 2-3 mm from the tip. Even with this arrangement, we often find that the ”Goldilocks” situation of appropriate suction force is difficult to determine – without aspiration, blood does not want to trickle through the catheter, and with aspiration, the wall of the vessel is sucked in and obstructs flow. Sometimes, a “milking” or “pulsatile” technique is used to aspirate, get a few drops of blood before the wall is sucked in, and then released to restart the process. An ideal solution would simulate this repetitive task for the operator and have implications anywhere blood sampling in small vessels is performed (such as with intravenous lines in patients with challenging anatomy).