Читать книгу Interventional Cardiology - Группа авторов - Страница 52

Ultrasound guided vascular access has gained attention by catheterization laboratories for arterial access, especially for large bore vascular access. The main advantage of ultrasound guided access is to identify the anatomy of the vessels and the relationship between the artery and the vein. Ultrasound guided access helps to select the puncture site more precisely. By using a sterile plastic cover, a 5–10 Hz linear ultrasound probe is positioned over the point of maximal pulsation to scan the femoral artery and vein. Each probe has a reference marker which is a vertical line, often backlit, that should be aligned according to the patient’s topography (e.g. to the patient’s right while scanning the groin vessels in short axis). The probe should be placed over the point of maximal arterial pulsation to identify the vessel. The artery should be imaged in both longitudinal and axial view starting with an axial view where the femoral artery appears as a pulsatile circle. The artery has thicker arterial walls than the vein, often with calcium or plaques, and can be easily identified because of its pulsatility. If there is any doubt identification of femoral artery versus vein is easily achieved applying gentle pressure with the vascular probe. The artery is not compressible, and the pulsations become more apparent while the vein collapses. Note that pulsation of the vessels can be misleading in patients with severe tricuspid regurgitation. Calcification or plaques along the artery help selecting the optimal puncture point once, by cranial and/or caudal scanning, the femoral bifurcation is found. If the probe is now turned clockwise (for the right femoral artery) or counterclockwise (for the left femoral artery) by 90 ^° with the probe marker pointing cranially, the longitudinal view of the artery is obtained. Here the femoral bifurcation is imaged, with relation to the underlying femoral head and, possibly, the inguinal ligament (visualized as an echodense triangular density cranially to the femoral head in the longitudinal view and as a linear density on axial views) (Figure 2.4).

Ultrasound is able to easily localize the femoral bifurcation, avoiding “low” punctures, but the superior limit of a correct puncture (inguinal ligament) is more difficult to identify, often leading to a “high puncture” (in up to 6.6% of the cases) [13]. Careful integration of the fluoroscopic and ultrasound information can minimize this risk. With the probe aligned perpendicular to the artery, imaged in the center of the view, the needle is inserted approximately at 45 °, 1–2 cm more caudally than the intended arterial entry site (center of the probe) (Figure 2.4). The artery is gently approached by repeated short jabbing movements. The needle will become visible when it enters the imaging plane of the probe. The probe can be slightly tilted to identify the reverberant artifact of the needle’s path to the artery but we recommend to use the same fixed probe angle to image the bifurcation of the common femoral artery to avoid high punctures, When the needle enters the artery insert the wire and use ultrasound again to accurately identify the puncture location. The rest of the procedure follows the standard procedure for vascular access. Sometimes, the vein runs medial and posterior to the artery. Using ultrasound can occasionally be useful to avoid entering artery before venous access and prevent other complications such as arteriovenous fistulae. In a multicenter randomized trial (FAUST trial) ultrasound as compared to fluoroscopic guidance increased common femoral artery cannulation in patients with high femoral bifurcation and improved first pass success rate, reduced the number of attempts, the risk of venipuncture and median time to access [14].

Hybrid access techniques such as integrating ultrasound with fluoroscopy or guidewire‐aided technique [15] can be helpful to obtain a correct puncture. The first technique involves placing the tip of a forceps at the anticipated arterial entry site at the mid femoral head as identified on fluoroscopy and aiming to puncture not above this landmark and the latter uses the ultrasound artifact from a J‐tipped guidewire placed from a contralateral arterial access inside the target common femoral artery to aid the puncture.