Detection of coronary artery anomalies before surgery is necessary to determine the surgical technique and to provide homografts or other tube grafts for total correction of these patients (3, 8, 11-13). At the present time, either preoperational coronary angiography or coronary CT angiography can be used, although the angiography is more common (2, 3, 9, 14). However, the accuracy of cardiac angiography and the best view of root aortogram to detect coronary anomaly is an open issue. We tried to investigate these subjects in our study by retrospective comparison of angiographic and surgical reports in large number of TOF patients.
According to the results of present study, 36 of 451 patients (8%) had coronary artery anomalies that was in concordance with results of other studies, although previous studies have wide ranges of reports from 2% to more than 30 percent.(1, 4, 15). Fellow and colleagues in a retrospective study reported 8% coronary arteries anomalies (21). In another study, Shrivastava et al. reviewed coronary angiograms of 296 cases with TOF, and reported 11.8% coronary artery anomalies.(16) Similar Iranian population study also report 5.9% coronary artery anomalies among 135 patients.(17) The incidence of coronary anomalies in TOF varied widely regarding the method of detection.
Postmortem studies demonstrate a higher incidence of 5-9 percent, which is probably due to greater possibility of careful examination of the coronary arteries (18), and the overestimation bias can be occur due to increased surgical mortality rate related with coronary artery anomalies. Some older studies surprisingly reported a very higher rate of anomaly and even high rate of coronary fistula in TOF patients that are poorly consistent with other researcher (1, 2, 4, 15).
In agreement with the dominant reports, our study confirmed that the most common coronary anomaly was the origin of LAD from RCA which was seen in 20 cases (4.4%), and single origin coronary artery was the second most common anomaly. RCA origin from LAD or left main coronary artery had the lowest frequency in our population that were in agreement with other studies (4, 15, 17).
Sensitivity of an angiography report depends on the experience of operators, quality of images, and the most important factor image views. In our study, the specificity of angiographies to detect coronary anomaly was high (99%), but the sensitivity was dependent on the angiographic views, which ranged from 75% for LAO/CRA view to 100% for LAO/CAU view. In this study, most abnormal coronary anatomy and courses were detected in the LAO/CAU view, and LAO/CRA view missed a significant portion of the coronary anomalies. Extreme caudal view (45º) had excellent sensitivity and specificity for detection of the anomalies in angiographic evaluation.
A few studies have compared coronary anomalies in the angiography with surgical reports and we could not find a sensitivity report for angiography in similar studies.(19) .Li et al. studied a limited number of TOF patients and reported coronary artery anomaly in 14% of the cases, while two of them were misdiagnosed in the pre-operational caudal angiography view (8). One of their cases died due to transection of an undiagnosed coronary anomaly during repair. Compared to that study, we had more mis-diagnosis in group 1 that can be related to the lesser usage of caudal view among this group, while we had not any misdiagnosed case among group 2. Carvalho et al. also emphasized on caudal view and labeled it as an excellent view to detect coronary arteries that passing the RVOT (10), and they claimed that the lateral view was also needed to differentiate the anterior or posterior position of the crossing artery in the laid-back view; it was indicated that this view may decrease some false positive cases in the caudal view. However, we have no any misunderstanding in the caudal view, and lateral view might not be necessary, so elimination of this view can reduce the X-ray radiation.
It seems that the key view in interpreting TOF coronary anatomy is caudal view. The Caudal view illustrated in Figures 1 and 2 from our patients clearly showed an abnormal course of coronary arteries crossing RVOT, while both of them had no significant finding in the LAO/CRA view.
Cineangiograms of the 8 proven abnormal coronaries that were reviewed by an expert pediatric cardiologist also showed the weakness of LAO/CRA view to detect coronary artery anomaly with only 25% definite detection of abnormal coronary course passing across the RVOT. In the LAO/CRA view, interpretation of the anterior-posterior relationship of RVOT and LVOT is difficult and may lead to high rate of misdiagnosis of clinically significant abnormal coronary courses.
Compared to CT scan, our data showed excellent sensitivity for angiographic detection of coronary anomaly crossing RVOT if the caudal view is used, but clearly the LAO/CRA view had lesser sensitivity. New dual source CT scan can accurately explore coronary anatomy with no need to the heart rate modification even in infants, with no usual cardiac catheterization risk. In multiple studies, more than 95% sensitivity and specificity were reported to detect coronary artery anomalies that is excellent result with lesser radiation in comparison to angiography(2, 4, 15). This modality may replace cardiac catheterization in future.