Coronary arteries in the fetal heart – a pictorial review

Introduction

Coronary arteries (CA) in the fetal heart are seen very rarely. However, due to the introduction of the latest ultrasound technology, they can be seen in the late third trimester of pregnancy, regardless of the heart anatomy.

Pictorial review

Based on our Unit Tricefy4 cloud database of ultrasound images, 5 fetuses were selected for re-evaluation (2018 – Sept 2023, over 5000 exams). Their clinical data can be found in Table 1. All these fetuses were subject to examinations performed with the use of a GE 10 convex transducer with the Research Cardiology Preset for the second/third trimester of pregnancy. In all of the fetuses, CA were seen in colour Doppler (Figure 1-5, Table 2). In 2 of them, the presence of turbulent blood flow in coronary arteries was proven by spectral Doppler. Case 4 presented a bilateral blood flow with a maximum velocity of up to 160 cm/sec in systole and 80 cm/sec in diastole (no survivor), whereas in case 5, a one-direction blood flow with a maximum velocity of 100 cm/sec (survivor) was observed.
All 5 fetuses presented different cardiac problems, including cardiomegaly + hypertrophy and tricuspid valve regurgitation due to absent ductus venosus, pulmonary critical stenosis, d-TGA, HLHS and AVC. All of them presented CA in the third trimester of pregnancy near term. A delivery by caesarean section took place in 4 cases out of 5. They were born alive with a birth weight of more than 3000 g and an Apgar score of 7 or more. Two out of 5 of them were asymptomatic, and HLHS was not considered for Norwood procedure due to neonatal lung oedema. However, 2 of them had cardiac procedures involving arterial switch operation on the 6th day of life, with a good result, and balloon valvuloplasty on the first day, with a good initial result; however, further digestive system complications and the use of stoma with prolonged hospital stay of up to 133 days were needed. In this short series of cases, in 3 out of 5 cases, the ultrasound visibility of coronary arteries had no clinical implications later on, but in one of them, with HLHS, which could be considered a poor sign for final outcome, and in another one, with critical PS, the possibility of long-term complications and blood flow impairment in the wall of his intestine cannot be ruled out.

Discussion

There are very few papers on the issue of coronary arteries [1-7]. According to the Chaoui hypothesis, confirmed by the research carried out by Baschat and Gembruch [1-4], the visualization of coronary flow is an important part of the cascade of abnormal haemodynamic events that can be detected by Doppler in the fetus, especially in the case of intrauterine growth restriction. “Heart-sparing effect” is defined as the increased perfusion of the coronary arteries in fetuses with severe growth restriction and abnormal Doppler velocimetry in the peripheral vessels. Increased perfusion detected in colour and pulsed Doppler is a late sign of fetal compromise in hypoxaemia. However, none of the 5 presented fetuses presented intrauterine growth restriction.
Fetal coronary artery blood flow was also observed by Baschat during acute fetomaternal haemorrhage [5], but no such problem was observed in our cases. Baschat pointed out that visualization of the coronary artery was highly operator-dependent [6].
Our short series of cases enriches current knowledge with the conclusion that, in addition to fetal growth restriction or anaemia, enhanced coronary blood flow could also be a temporary event without clinical significance in the short-term prognosis, which is contrary to what has been reported so far [7].
In this series of cases, it is worth noticing a value not only of colour Doppler but also spectral Doppler with the measurement of the maximal velocity of blood flows.

Conclusions

Fetal haemodynamics including coronary arteries, both in normal heart anatomy and in heart defects, could be analysed during fetal echocardiography not only in fetuses with fetal growth restriction, but also in normal fetal growth. Visualization of fetal coronary artery flow may have a temporary nature, and therefore may suggest possible fetal heart compensation mechanisms. In the case of visualization of coronary artery by colour Doppler, pulse wave Doppler is recommended for the analysis of maximal velocity and direction of blood flow.

Conflict of interest

The author declares no conflict of interest.

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