Overview of the arterial system

The arterial system

The left-sided aorta couples the left ventricle to the arterial system. Transthoracic ultrasound detects the ascending aorta (left parasternal view) and the aortic arch (suprasternal view). In the ICU, however, these acoustic windows may be impossible to obtain. Transesophageal echocardiography (TEE) is invaluable in visualizing the thoracic aorta in the ICU but typically cannot image the entirety of the thoracic aorta. Usually, the brachiocephalic trunk, left common carotid artery (CCA), and left subclavian artery (SCA) originate from the arch, in that order. The right CCA begins at the bifurcation of the brachiocephalic trunk, whereas the right vertebral artery (VA) originates from the right SCA. One third of patients have a common origin of the left CCA and brachiocephalic trunk, or the former originates from the proximal segment of the latter. The left VA may originate from the arch, and the right SCA may exhibit an aberrant origin. A right-sided aorta is rare and frequently associated with other types of congenital cardiovascular disease. ^,

The CCA is detected sonographically in the lateral aspect of the neck by using high-frequency transducers (7.5 to 10 MHz) in both the longitudinal and transverse planes. The CCAs run upward to about the upper border of the thyroid cartilage before branching. The normal Doppler spectral waveform (DSW) of the CCA has a narrow peak systolic and forward diastolic flow ( Figure 8 E-1 ). The CCA bifurcates into the internal (ICA) and external (ECA) carotid arteries. The ICA does not branch in the neck and has a low-resistance DSW with forward diastolic flow. The ECA branches in the neck and has a high-resistance DSW with reversed diastolic flow. The VA runs toward the sixth cervical vertebra and enters the base of the skull accompanied by its vein. The SCA becomes the axillary artery after crossing the first rib, and the latter continues as the brachial artery (BA) after the posterior axillary fold. The BA ends about 1 cm distal to the elbow by dividing into the radial artery (RA) and ulnar artery (UA). The RA becomes the deep and the UA the superficial palmar arch, respectively, which join in the hand. The DSW of upper extremity arteries is triphasic.

The descending thoracic aorta is detected sonographically via the cardiac apical window. The abdominal aorta (AA) begins at the aortic hiatus of the diaphragm and ends at the fourth lumbar vertebra (bifurcation). The AA is detected sonographically on longitudinal, transverse, and oblique planes by using convex transducers (2.5 to 5 MHz), and its DSW is biphasic. The AA gives off several main branches: the celiac artery (CA), which supplies the liver, gallbladder, stomach, intestines, and pancreas and in turn branches into the splenic, left gastric, and common hepatic arteries (see Figure 8 E-1 ); the superior mesenteric artery (SMA), which originates approximately 1 cm inferior to the CA and supplies the intestines and pancreas; the inferior mesenteric artery (IMA), which supplies the colon and rectum; and the renal arteries, which branch off last and supply the kidneys and adrenal glands. The AA bifurcates into the right and left common iliac arteries at the level of the umbilicus, and these vessels travel distally to divide into the internal (IIA) and external (EIA) iliac arteries. The EIA enters the thigh at the inguinal ligament and becomes the common femoral artery (CFA). The CFA bifurcates into the superficial (SFA) and deep (DFA) femoral arteries. The DFA travels laterally and medially to supply the deep thigh muscles. The SFA travels distally through the adductor canal (Hunter canal) into the popliteal fossa and becomes the popliteal artery (POPA). The POPA gives off several branches (e.g., sural) and bifurcates into the anterior tibial artery (ATA) and the tibioperoneal trunk (TPT). The ATA travels anteriorly and laterally between the tibia and fibula and becomes the dorsalis pedis artery (DPA) as it travels across the foot. The TPT bifurcates into the posterior tibial artery (PTA) and peroneal artery. The PTA travels posterior to the medial malleolus and peroneal artery and down the calf. The PTA bifurcates into the medial and lateral plantar arteries in the foot. The latter join with the plantar metatarsal arteries to form the plantar arch. The lower extremity arteries have a triphasic DSW (see Figure 8 E-1 ). ^,