16.2 Great Vessels, Venous Return, and Pulmonary Artery Assessment

Use a flow-path map rather than an isolated measurement

CCI task D7 covers great vessels, venous return, and pulmonary artery assessment. Trace the right-sided pathway from RV inflow through the RV body, infundibulum, pulmonary valve, main pulmonary artery (MPA), bifurcation, and proximal right and left pulmonary arteries. Then trace pulmonary venous return to the LA and systemic venous return through SVC, IVC, hepatic veins, and coronary sinus to the RA. This map prevents a high velocity, dilated segment, or unexpected color jet from being assigned to the wrong structure. Confirm unusual connections in orthogonal views.

Use parasternal short-axis at the aortic valve and a pulmonary-artery-focused modification to show distal RVOT, pulmonary valve, MPA, and bifurcation. A high left parasternal or suprasternal window may improve branch arteries; subcostal views help in congenital anatomy. Measure distal RVOT at end diastole just proximal to the annulus. Measure MPA at end diastole, perpendicular to its long axis, halfway between the pulmonic valve and bifurcation; measure proximal RPA and LPA in the same phase. A TTE MPA diameter above 25 mm is abnormal in adults but nonspecific: pressure or volume overload, shunts, valve disease, altered body size, and normal variation must be considered.

Localize pulmonary-artery and RVOT findings

Color Doppler first identifies aliasing or regurgitation. Step PW through the RVOT and across accessible segments to locate acceleration, then use aligned CW for the highest velocity when obstruction is suspected. Place a small PW sample 1–2 mm below the pulmonary valve to acquire a clean RVOT VTI and acceleration time (AccT), measured from flow onset to peak. An AccT above 105 ms is generally normal; shortening or midsystolic notching can support increased pulmonary vascular impedance but is not diagnostic of pulmonary hypertension. Heart rate, stroke volume, RV dysfunction, sampling location, respiration, and technical filtering alter the contour.

Inspect the pulmonary valve in 2-D for leaflet number, doming, mobility, and annular size. A narrow aliasing origin at the valve differs from subvalvar infundibular acceleration or supravalvar/branch stenosis. Preserve each PW sample location in labeled clips so the CW envelope has an anatomic source. In suspected shunt physiology, combine pulmonary and systemic flow calculations only when both outflow diameters and VTIs are technically valid; small diameter errors are squared and can dominate the ratio.

Interpret the MPA and RVOT with TR velocity or PASP, PR end-diastolic velocity when valid, RV size and function, RA size, septal flattening, shunt search, and valve morphology. A dilated MPA with normal pressure estimates may reflect prior or volume loading; a normal MPA does not exclude pulmonary hypertension. Report the exact segment and whether a velocity is proximal, valvar, supravalvar, or branch-level. If comparing CT, CMR, and echo, do not treat unlike phases, planes, or edge conventions as true growth.

Examine systemic and pulmonary venous return

Image the IVC in subcostal long axis and measure at end expiration 0.5–3.0 cm proximal to the RA ostium and distal to the hepatic-vein junction. Observe quiet breathing and a sniff, and confirm that apparent caliber change is not translation out of plane; a transverse view can verify the maximum diameter. IVC size and collapse support an RA-pressure category but are less reliable with positive-pressure ventilation, abnormal respiratory effort, athletic remodeling, or chronic right-heart disease. Hepatic-vein PW across a full respiratory cycle adds systolic and diastolic filling information and can reveal systolic reversal with severe TR or expiratory diastolic reversal with constriction.

Visualize the SVC from subcostal, right supraclavicular, or modified apical views when indicated. A dilated coronary sinus should prompt consideration of a persistent left SVC. With an authorized agitated-saline study, left-arm injection entering the coronary sinus before the RA supports that connection; compare with right-arm injection and exclude unroofed coronary sinus or other shunts before concluding anatomy. Interrupted IVC with azygos continuation may show absent hepatic continuity and a prominent posterior mediastinal vein. CT or CMR usually maps systemic venous variants more completely.

Use color to locate pulmonary veins and place PW about 10 mm proximal to the LA, commonly in the right upper pulmonary vein from an apical view. A normal waveform commonly has systolic, diastolic, and atrial-reversal components, but rhythm, age, MR, LA pressure, and sampling depth alter it. Attempt multiple views to document venous connections. Failure to see all four veins does not prove partial anomalous pulmonary venous return; unexplained right-heart volume overload, an atypical vein course, or sinus venosus defect should trigger additional imaging.

A complete report names each visualized segment, connection, diameter with phase and convention, direction and character of flow, obstruction or regurgitation, and technical limitation. Promptly communicate suspected acute pulmonary-artery obstruction, severe RV pressure overload with deterioration, or a critical congenital/iatrogenic connection, while recommending definitive CT, CMR, or TEE according to stability and local protocol.