Apical Views

The Apical Window: Transducer Placement

With the patient still in left lateral decubitus, the transducer is placed at the point of maximal impulse (PMI) — the cardiac apex, typically the fifth intercostal space at the midclavicular line — and angled superiorly toward the base of the heart.

Apical Four-Chamber (A4C) View

With the index marker toward the patient's left side, the A4C view shows all four chambers simultaneously: the LV (lateral wall), the RV (free wall), the LA, the RA, the mitral valve, the tricuspid valve, and the interventricular and interatrial septa. A4C is the workhorse apical view: it is one of the two views (paired with the apical two-chamber) used for Simpson's biplane method of disks to calculate ejection fraction, it is the primary window for pulsed-wave Doppler of mitral inflow (E and A waves) and tricuspid inflow, and it provides continuous-wave Doppler alignment for the tricuspid regurgitant jet used to estimate right ventricular systolic pressure. It also profiles septal and lateral wall motion across the basal, mid, and apical segments.

Apical Five-Chamber (A5C) View

From the A4C position, tilting the transducer anteriorly (toward the patient's right shoulder) brings the left ventricular outflow tract (LVOT) and aortic valve into the scan plane while the atria drop out of view — hence 'five chambers.' A5C is the primary window for LVOT pulsed-wave Doppler (velocity-time integral for stroke volume/cardiac output and the continuity equation) and for continuous-wave Doppler across the aortic valve (peak velocity and mean gradient in aortic stenosis).

Apical Two-Chamber (A2C) View

Rotating the transducer roughly 60-90 degrees counterclockwise from A4C, without translating the probe, eliminates the right-heart structures and shows only the LV, LA, and mitral valve. A2C profiles the anterior and inferior LV wall segments and, paired with A4C, completes the two orthogonal planes needed for Simpson's biplane ejection fraction.

Apical Three-Chamber / Apical Long-Axis (A3C) View

Rotating a further ~60 degrees counterclockwise from A2C (roughly 120 degrees total from A4C) produces the apical long-axis view, which resembles the PLAX view but is obtained from the apex. It shows the LV, LA, mitral valve, and the LVOT/aortic valve together, and profiles the anteroseptal and inferolateral (posterior) wall segments. Because it also aligns with LVOT-to-aortic flow, it serves as a second, confirmatory Doppler window for aortic valve velocity and is useful for assessing systolic anterior motion (SAM) of the mitral valve in hypertrophic cardiomyopathy.

A Common Technical Pitfall: Apical Foreshortening

The single most common technical error in the apical window is foreshortening — angling the transducer so the imaging plane cuts across the LV obliquely rather than through its true long axis and anatomic apex. A foreshortened LV appears shorter and more rounded than it truly is, which artificially reduces traced LV volumes and can falsely elevate the calculated ejection fraction. Sonographers avoid this by maximizing LV length and confirming that the apex, rather than a lateral LV segment, forms the sharpest point of the cavity before freezing images for Simpson's biplane tracing.

Doppler Sample Placement and Color Screening

Pulsed-wave Doppler for mitral inflow is performed in A4C with the sample volume positioned at the tips of the open mitral leaflets, where flow velocity is most representative of transmitral filling; the same principle places the tricuspid inflow sample at the tricuspid leaflet tips. For the LVOT, the pulsed-wave sample volume is positioned just proximal to the aortic valve, matching the location where the LVOT diameter was measured in PLAX, so that the two measurements describe the same cross-sectional area for the continuity equation. Color Doppler is swept through A4C, A2C, and A3C/A5C during the standard protocol to screen qualitatively for mitral, tricuspid, and aortic regurgitation and to guide where the continuous-wave cursor should be placed to capture a jet's peak velocity.

Why Doppler Belongs to the Apical Window

Doppler velocity measurement accuracy depends on the intercept angle between the ultrasound beam and the direction of blood flow; error is minimized as the angle approaches 0 degrees (cosine of 0 degrees equals 1), and standard practice keeps the intercept angle under about 20 degrees (cosine of 20 degrees is approximately 0.94, under 6% velocity underestimation). Blood flow through the mitral, tricuspid, and aortic valves runs roughly along the long axis of the LV — from apex toward base for inflow, and base toward the apex-adjacent LVOT for outflow — which is exactly the direction the ultrasound beam travels from an apical transducer position. This makes the apical views (A4C for mitral/tricuspid inflow, A5C/A3C for LVOT and aortic outflow) the primary windows for essentially all spectral and continuous-wave Doppler hemodynamic measurements, complementing the 2D anatomic detail obtained from the parasternal window.