Physiology of the left heart
The left ventricle (LV) is a pressurized chamber with a definite
myofiber architecture. The normal left ventricle is cone shaped,
posterior to and ‘hugged’ by the right ventricle (RV) and comprises an
inlet portion containing the mitral valve apparatus, an overlapping
outlet portion leading to the aortic valve, and a rather smooth apical
portion containing fine crisscross trabeculations25.
Anatomically, the LV is narrower and longer than the RV. Regarding the
myoarchitecture, the LV wall contains three layers from the
subepicardium to the subendocardium with a counterdirectional helical
arrangement of muscle fibers that is energetically efficient and
important for equal redistribution of stresses and strain in the
heart26. Furthermore, there is a gradual thinning of
the LV wall that is observed toward the apical segments. In contrast to
the RV, there are two papillary muscles that originate from the LV free
wall and are attached to the mitral valve chordae tendinae. During
contraction, the base and apex of the LV rotate in opposite directions.
The left and right ventricles are also subjected to the same filling
pressure, and their combined ventricular output perfuses the fetal
system. The LV primarily perfuses the coronary and cerebral circulations
through the ascending aorta, and the RV perfuses the lower body and
placental circulation through the ductus arteriosus and descending
aorta. Postnatally, after programmed closure of the fetal shunts, the LV
pumps blood at higher pressures than other cardiac cavities as it faces
a much higher workload and mechanical afterload. Recent findings from
the study by Junno et al. suggest that the fetal left ventricle seems to
be more sensitive to progressively worsening hypoxemia and acidemia than
the right ventricle27. As stated by Sengupta and
colleagues, understanding the cardiac structure–function relationship
of both the left and right heart is essential and constitutes the basis
of a comprehensive and structured assessment of cardiac
anatomy26. The advent of high temporal resolution
imaging methods, volumetric approaches and the recently introduced novel
semiautomatic algorithms for standardized reconstruction of cardiac
geometry might contribute to an improvement of prenatal detection rates
for more than just left-sided lesions. The potential of these
volume-based technologies to provide profound insights into global
anatomic changes of left heart anomalies will be discussed below.