Coronary heart disease is a common heart disease in adults. Infants can also experience heart problems caused by coronary arteries. CAD is a manifestation of coronary heart disease in infants. CAD lesion detection rate in the present study was as high as 1.06%. Therefore, bilateral coronary arteries should be carefully monitored during echocardiography. In the present study, the chief complaint (or surrogate chief complaint) in the congenital group was auscultation murmurs, while that of the acquired group was fever. Therefore, echocardiography should be routinely performed to screen for CAD in children with auscultation murmur and fever lasting for five days or more.
The present study showed that the causes of CAD include congenital dysplasia and acquired diseases. A total of 84.77% (206/243) were acquired diseases, all of which were KD, which was the main cause of infant CAD. Of these, 15.23% (37/243) were congenital causes, including CAF, anomalous origin of the coronary artery, severe pulmonary stenosis, and moderate aortic stenosis. Acquired diseases were medically treated, while congenital dysplasia was treated surgically. Therefore, it is very important to quickly and accurately determine the cause of CAD. There was no significant difference in the CAD Z-score between the two groups of children, so it could not be used as a key point of identification.
The present study showed that the acquired causes were more likely to manifest as coronary artery segmental dilatation, while congenital causes were more likely to manifest as tubular coronary artery dilatation. By observing the scope and shape of CAD, the dilatation was first distinguished by its congenital and acquired causes. These data were combined with clinical symptoms and signs and a laboratory examination to compare with KD diagnostic criteria, where 2.43% (5/206) of children with KD were identified from the cases with tubular dilatation.
Congenital causes also showed cardiac structure characteristics. CAF is present in 1–2% of the general population[4–5]. In the early embryonic period, the sinusoid space of the myocardium communicates with the heart cavity and epicardial blood vessels. As the heart develops, blood vessels are distributed on the surface of the heart from the root of the aorta. The growth and development of the myocardium gradually compress the sinusoid spaces into small channels, which become coronary arteries and capillaries in the myocardium. If the development is impaired, the sinusoid space of the myocardium is not degraded, leading to abnormal communication between the coronary arteries and the heart chambers and forming a CAF. The clinical symptoms of this disease are related to the size of the fistula shunt. A small shunt may have no obvious symptoms. Only a continuous murmur on the left or right parasternal border can be identified during a physical examination. With age, some patients will experience palpitations, shortness of breath, cyanosis, angina, and heart failure after physical activity. CAF should be considered when right or left proximal coronary artery broadening is found via transthoracic ultrasonography. More than 90% of coronary fistulas are single artery fistulas, of which right coronary artery is the most common, accounting for ~ 50% of cases, followed by left coronary artery at ~ 30–40%, and bilateral coronary fistulas at ~ 10%. The most common sites of termination are the pulmonary artery, right ventricle, and right atrium. Drainage into the left side of the heart is unusual. In the 30 CAF patients in the present study, 26 patients had a right coronary artery pulmonary fistula (Fig. 2) and four patients had a right coronary artery right ventricular fistula. It is thus key to identify diseased coronary arteries and search for fistulas and other associated malformations. The parasternal long- and short-axis sections of the great blood vessels are very important. In addition, several non-standard sections are also used to explore the location of coronary artery dislocations and fistulas.
There were five anomalous origin coronary artery patients in the present study. Among them, four had a left coronary artery from the pulmonary artery (ALCAPA) (Fig. 3) and one had a right coronary artery from the left coronary sinus. Anomalous origin of the coronary arteries is mainly due to the error in the process of coronary artery fusion to the aortic sinus during embryonic development. It is a serious congenital coronary artery malformation. ALCAPA is relatively more common. As the pulmonary circulatory resistance decreases after birth, the effective myocardial perfusion depends on the collateral circulation formed between the right coronary artery of normal origin and the left coronary artery of abnormal origin. The collateral circulation is not well developed and the left ventricular myocardial blood supply is reduced, resulting in left ventricular dysfunction and mitral regurgitation. Anomalous origin of the coronary artery from the pulmonary artery may be asymptomatic at birth, then manifest as sweating, pale face, and crying, and often present along with congestive heart failure. The parasternal long-axis section, short-axis section of the great blood vessels, and the apical five-chamber heart section are all important sections of the coronary arteries, focusing on the position of the coronary artery ostium and the proximal shape. When the initial segment of the left or right coronary artery is thickened and there is no coronary artery ostium in the aortic sinus, it is important to observe whether there is coronary artery ostium in the right medial side and the posterior side of the main pulmonary artery. About 90% of the children died before reaching one year of age, mainly due to congestive heart failure. Early diagnosis and treatment can significantly improve their prognosis.
Acquired etiologies include KD, acute stage of myocarditis, polyarteritis nodosa, Takayasu disease, scleroderma, and Noonan syndrome[6–9]. Of these, KD is the most frequent CAD etiology in children and is defined as vasculitis involving medium and small blood vessels. In patients with KD, risk factors for coronary artery injury include male gender, younger age at diagnosis, persistent fever longer than 14 days, anemia, increased white blood cell count, neutrophil percentage, platelet count, alanine transaminase, hypersensitive C-reactive protein, erythrocyte sedimentation rate, and decreased hemoglobin and albumin[10–17].
Study limitations include the fact that all of the acquired causes are KD, which do not cover all of the acquired CAD characteristics. In addition, study sample size needs to be expanded for further investigations.