Coronary arteries in transposition of the great arteries

Embryology of coronary arteries and anatomy/pathophysiology of coronary anomalies. A comprehensive update

OBJECTIVES

This paper reviews new findings in both embryology of coronary arteries and in clinical observations of coronary artery anomalies.

FOCUS

Our presentation emphasizes studies based on: 1) newer methods of coronary development in animals and humans, and 2) intravascular ultrasonography to interpret pathophysiology and guide treatment of coronary anomalies.

CONCLUSIONS

New data reveal the roles of many cellular interactions and signaling pathways involved in the normal and abnormal formation of the coronary arterial system and the consequences of their defective formation. Pathogenetic developmental mechanisms include dysfunction of the Notch and Hypo signaling pathways, angiogenic and arteriogenic molecules, and neural crest cells. We addressed numerous clinically significant coronary anomalies and their prevalence in a general population (especially those characterized by an ectopic origin with aortic intramural course), and point out the critical relevance of understanding the variable mechanisms of coronary dysfunction, especially, fixed versus phasic stenoses or intermittent spasm, and individual severity of clinical presentations.

Coronary anomalies in mice with congenital heart defects

BACKGROUND

Coronary anomalies are frequently associated with congenital cardiac defects. Accordingly, we tested the hypothesis that the development of the tunica media of coronary arteries/arterioles is compromised in mice with cardiac defects of the outflow tract (persistent truncus arteriosus, double outlet right ventricle and transposition of the great arteries) by studying hearts of G7-9 generation mice bred from mutagenized mice caused by N-ethyl-N-nitrosourea. Mice were studied at embryonic days E16.5, E17.5, and postnatal days 1 and 11. Data were based on immunohistochemistry of serial sections.

RESULTS

In 21 of 24 mice with outflow tract defects, the development of smooth muscle in arteries and arterioles was retarded; most commonly arterioles had an incomplete layer of smooth muscle or in a few instances, lacked a tunica media. In this model, an absence of a coronary ostium occurred in only 2 mice, indicating that the mechanisms underlying the formation of coronary ostia and the recruitment and differentiation of vascular smooth muscle differ. Coronary fistulas were present in 20% and dilated vessels in 30% of the hearts with cardiac defects.

CONCLUSIONS

The data suggest that vascular smooth muscle recruitment and differentiation are not necessarily linked to other coronary anomalies, such as absence of a main coronary artery or branching patterns.

Can we better understand the known variations in coronary arterial anatomy?

Coronary arterial anatomy is remarkably diverse. Identification of surgical risk factors, however, requires description in a uniform fashion. Such description mandates that account be given of both aortic sinusal origin and variability in aortopulmonary relationships. Currently, however, it is rare to find all this information provided either in clinical reports or published reviews. In this review, therefore, we summarize why both these features are important, emphasizing the marriage of convenience between the aortic root position within the cardiac base and the arrangement of the epicardial coronary arteries. The inductive approach accounts for all potential variations.

Prevalence of Congenital Coronary Artery Anomalies and Variants in 2697 Consecutive Patients Using 64-Detector Row Coronary CTAngiography

BACKGROUND

Coronary artery anomalies are not common, but could be very serious.

OBJECTIVES

This study determines the frequency of coronary anomalies and normal variants by multi-detector-row computed tomography (MDCT).

PATIENTS AND METHODS

The results of cardiac MDCT study in 2697 consecutive patients were analyzed retrospectively. Acquisition was performed by a 64-detector row CT machine. Imaging results were assessed by experienced radiologists.

RESULTS

Myocardial bridging was by far the most frequent coronary variant (n = 576, 21.3%). Eighty-three subjects (3.1%) showed other coronary anomalies and variants. Anomalies of origination and course of the left main coronary artery (LMCA) were detected in 1.09% of the subjects. The frequency of these anomalies in the right coronary artery (RCA), left circumflex artery (LCx), left anterior descending artery (LAD), posterior descending artery (PDA) and obtuse marginal (OM) artery were 1.24%, 0.33%, 0.1%, 0.07% and 0.03%, respectively. The single coronary pattern was seen in 0.18% and coronary fistulas in 0.07%.

CONCLUSION

Based on the fact that coronary CT-angiography using MDCT can display different coronary anomalies, this study shows similar results to other reports on the subject. Future advances in the performance of CT machines will further improve the quality of CT-based cardiac imaging.

Newer concepts for imaging anomalous aortic origin of the coronary arteries in adults

Of the different kinds of coronary anomalies observed in adults, anomalous origin of a coronary artery from the opposite sinus of Valsalva with an "interarterial" course (ACAOS) entails a high risk of clinical consequences related to the intramural course of the ectopic coronary artery. We review current imaging modalities for differentiating this condition from generally benign coronary anomalies and for quantifying the severity of individual cases. For identifying ACAOS, noninvasive modalities (echocardiography, computed tomographic angiography, and coronary magnetic resonance angiography) are preferred: the favored modalities are transthoracic echocardiography in children and multidetector computed tomography in adults. For evaluating the pathophysiologic mechanisms of ischemia in ACAOS and subclassifying the severity of individual forms, coronary intravascular ultrasonography provides enhanced temporal and spatial resolution. The critical quantifiable features of the coronary anatomy in ACAOS seem to be hypoplasia, lateral compression at the level of the intramural course, and possibly exercise-related further narrowing of the proximal ectopic segment. Definitive guidelines are being developed for the optimal workup and treatment of ACAOS.

Myocardial infarction late after Mustard procedure

This case report discusses a young man with d-transposition of the great arteries who suffered three myocardial infarctions late after his Mustard procedure. The etiology was found to be a coronary embolism, with a mural thrombus in the systemic ventricle as the probable nidus. The risk factors of coronary embolism are discussed, and it is concluded that Mustard patients are at risk for coronary embolization and myocardial infarction, which can be a cause of sudden death.

Coronary artery anomalies--current clinical issues: definitions, classification, incidence, clinical relevance, and treatment guidelines

The study of coronary artery anomalies would benefit from the clarification of various fundamental issues, including the definitions, classification, incidence, pathophysiologic mechanisms, and clinical relevance of each anomaly. The greatest challenge is to identify the abnormality and determine its clinical relevance so that appropriate treatment can be instituted. Currently, the coronary anatomy is essentially defined by the features of the (conductive) epicardial coronary tree and its dependent territory. Therefore, one must consider all the possible and observed variations in anatomic features that are used to describe the coronary arteries. We propose that the left anterior descending, circumflex, and right coronary arteries be considered the essential elementary units of coronary anatomy. We also suggest that the coronary arteries be defined not by their origin or proximal course, but by their intermediate and distal segments or dependent microvascular bed. A strict classification system is necessary before meaningful data can be gathered about the incidence of coronary anomalies. With respect to clinical relevance, the greatest challenge is presented by anomalies that only occasionally cause critically severe clinical events and are otherwise compatible with a normal life. In such cases, it is not known whether the specific features of a given anomaly cause adverse clinical consequences, or whether additional episodic factors are required. To correlate subclassifiable anatomic and functional features with clinical events and prognoses, a large, multicenter database, relying on prospective, coordinated protocols, is urgently needed. In the absence of established official guidelines, we present practical protocols for diagnosing and treating coronary anomalies.

Anatomic variability in coronary arterial distribution with regard to the arterial switch procedure

BACKGROUND

We investigated the coronary arterial origins and course and the position of the great arteries in hearts with discordant ventriculoarterial connections. At the same time, we sought to evaluate the practicality of alphanumeric classifications in accounting for surgically relevant features of the coronary arteries.

METHODS AND RESULTS

We studied 200 postmortem hearts, noting the patterns of coronary arterial branching, the vertical and horizontal location of the arterial orifices within the aortic sinuses, the course of the proximal coronary arteries in relation to the aortic wall, and the relations of the great arteries and their respective commissures. All hearts examined had concordant atrioventricular and discordant ventriculoarterial connections. We found 7 of the 8 predicted patterns for sinusal origin of the 3 major coronary arteries and identified 5 different positions of the arterial trunks relative to each other. A correlation was found between less frequent relationships of the arterial trunks and unusual patterns of coronary arterial branching, as well as with mismatch between the valvar commissures.

CONCLUSIONS

The surgically relevant features of the coronary arteries in hearts with discordant ventriculoarterial connections are best described rather than classified. Correlations exist between certain, less frequent relations of the great arteries and unusual patterns of branching of the coronary arteries. The presence of unusual great arterial positions should alert the surgeon to potentially complicated arrangements of the origin and distribution of the coronary arteries.