APICAL FOUR CHAMBER VIEW OF THE HEART

Transverse view of the fetal chest. Apex of the heart pointing directly toward or away from the transducer. Interventricular septa and interatrial septa are parallel to the transducer.
LV – left ventricle RV – right ventricle Ao – ascending aorta RA – right atrium LA - left atrium Dao – descending thoracic aorta Arrow – interventricular septum

VISUALIZED STRUCTURES ON THIS VIEW

Structures best visualized on this view are those that are perpendicular to the ultrasound beam.

1. Two atrial chambers of equal size (left atrium is situated most posteriorly and is closest to the fetal spine).
2. Two ventricular chambers of equal thickness. The right ventricular chamber is slightly larger than the left ventricular chamber (more obvious in third trimester).
3. The atrioventricular valves (mitral and tricuspid) between the atria and ventricles). Excellent view for assessing valvular stenosis or incompetence as the the doppler angle of insonation is close to 0°.
4. Interventricular septum between the ventricles (not well visualized as the septum is parallel to the ultrasound beam).
5. The interatrial septum and foramen ovale between the atria.
6. Pulmonary veins entering the left atrium.

Video clip of Apical Four Chamber view

COLOR DOPPLER ASSESSMENT

· Color doppler of the heart should be performed from an apical approach.

· Angle of insonation of about 45 degrees.

· During diastole perfusion of color from both atria into their respective ventricles across the AV valves. The perfusion of color should be of approximately equal size and separated by the interventricular septum.

Four chamber view in atrial systole
Note the direction of color perfusion from the atria to their respective ventricles.

· Defects on perfusion of the ventricles occur in;

o Ventricular septal defect – flow across the membranous or muscular part of the septum.

o Atrioventricular septal defect – mixture of blood at the crux of the heart.

o Disproportion between the chamber perfusion – coarctation of the aorta.

o Disproportion between the chamber perfusion + VSD – double outlet RV, tubular aortic arch hypoplasia and interruption of the aortic arch.

o Small RV perfusion stripe – Pulmonary atresia + intact ventricular septum, critical pulmonary stenosis.

o Double inlet ventricle with patent AV valves.

· During systole both AV valves should be closed, and AV regurgitation is visualized as blood flowing from the ventricle into the atrium while the valve is closed.

Four chamber view in ventricular systole

CONDITIONS THAT MAY BE DIAGNOSED

1. Hypoplastic left or right ventricle.
2. Defects of the interatrial or interventricular septum (remember that an artifactual membranous septal defect may occur as the angle of insonation is parallel to the septum).
3. Abnormalities of the atrioventricular valves.
4. Anomalous pulmonary venous drainage.