Myocardial perfusion in excessively trabeculated hearts: Insights from imaging and histological studies

In gestation, the coronary circulation develops initially in the compact layer and it expands only in fetal develop-ment to the trabeculations. Conflicting data have been published as to whether the trabecular layer is hypoperfused relative to the compact wall after birth. If so, this could explain the poor pump function in patients with left ventricular excessive trabeculation, or so-called noncompaction. Here, we review direct and indirect as-sessments of myocardial perfusion in normal and excessively trabeculated hearts by in vivo imaging by magnetic resonance imaging (MRI), positron emission tomography (PET)/single photon emission computed tomography (SPECT), and echocardiography in addition to histology, injections of labelled microspheres in animals, and elec-trocardiography. In MRI, PET/SPECT, and echocardiography, flow of blood or myocardial uptake of blood-borne tracer molecules are measured. The imaged trabecular layer comprises trabeculations and blood-filled intertrabecular spaces whereas the compact layer comprises tissue only, and spatio-temporal resolution likely af-fects measurements of myocardial perfusion differently in the two layers. Overall, studies measuring myocardial uptake of tracers (PET/SPECT) suggest trabecular hypoperfusion. Studies measuring the quantity of blood (echo-cardiography and MRI) suggest trabecular hyperperfusion. These conflicting results are reconciled if the low up-take from intertrabecular spaces in PET/SPECT and the high signal from intertrabecular spaces in MRI and echocardiography are considered opposite biases. Histology on human hearts reveal a similar capillary density of trabecular and compact myocardium. Injections of labelled microspheres in animals reveal a similar perfusion of trabecular and compact myocardium. In conclusion, trabecular and compact muscle are likely equally perfused in normal hearts and most cases of excessive trabeculation.(c) 2022 Japanese College of Cardiology. Published by Elsevier Ltd. This is an open access article under the CC BY li-cense (http://creativecommons.org/licenses/by/4.0/).

Automated summary

The development of coronary circulation in gestation is initially in the compact layer and extends to the trabeculations in fetal development. Conflicting results have been reported regarding the perfusion of the trabecular layer compared to the compact wall after birth. This study reviewed different imaging techniques and histology to evaluate myocardial perfusion in normal and excessively trabeculated hearts, suggesting that trabecular and compact muscle are likely equally perfused in normal hearts and most cases of excessive trabeculation.