Remarkable anatomic anomalies of coronary arteries and their clinical importance: a multidetector computed tomography angiographic study

Anatomical Variants of the Origin of the Coronary Arteries: A Systematic Review and Meta-Analysis of Prevalence

PURPOSE

The most common anomaly is an anomalous left coronary artery originating from the pulmonary artery. These variants can be different and depend on the location as well as how they present themselves in their anatomical distribution and their symptomatological relationship. For these reasons, this review aims to identify the variants of the coronary artery and how they are associated with different clinical conditions.

METHODS

The databases Medline, Scopus, Web of Science, Google Scholar, CINAHL, and LILACS were researched until January 2024. Two authors independently performed the search, study selection, and data extraction. Methodological quality was evaluated using an assurance tool for anatomical studies (AQUA). Pooled prevalence was estimated using a random effects model.

RESULTS

A total of 39 studies met the established selection criteria. In this study, 21 articles with a total of 578,868 subjects were included in the meta-analysis. The coronary artery origin variant was 1% (CI = 0.8-1.2%). For this third sample, the funnel plot graph showed an important asymmetry, with a p-value of 0.162, which is directly associated with this asymmetry.

CONCLUSIONS

It is recommended that patients whose diagnosis was made incidentally and in the absence of symptoms undergo periodic controls to prevent future complications, including death. Finally, we believe that further studies could improve the anatomical, embryological, and physiological understanding of this variant in the heart.

Anomalous origin of the coronary artery: prevalence and coronary artery disease in adults undergoing coronary tomographic angiography

BACKGROUND

Anomalous aortic origin of a coronary artery (AAOCA) is a rare congenital coronary anomaly with the potential to cause adverse cardiac events. However, there is limited data on the association between AAOCA and coronary artery disease (CAD). Therefore, the aim of this study is to determine the prevalence and symptoms of patients with AAOCA, as well as investigate the correlation between AAOCA and CAD in a population referred for coronary computed tomographic angiography (CTA).

METHODS AND RESULTS

All consecutive patients who underwent CTA from 2010 to 2021 were included. Characteristics, symptoms, coronary related adverse events and CTA information were reviewed by medical records. Separate multivariable cumulative logistic regressions were performed, using the stenosis severity in each of the four coronaries as individual responses and as a combined patient clustered response. Finally, we identified 207 adult patients with AAOCA, the prevalence of AAOCA is 0.23% (207/90,501). Moreover, this study found no significant association between AAOCA and CAD. AAOCA did not contribute to higher rates of hospitalization or adverse cardiac events, including calcification.

CONCLUSION

AAOCA is a rare congenital disease that is not associated with increased presence of obstructive CAD in adults.

Prevalence and characteristics of coronary artery anomalies (CAAS) in 3016 symptomatic adult participants undergoing coronary computed tomography angiography (CCTA): A single-center retrospective study in Iran

Introduction

Coronary artery anomalies (CAAs) are associated with an increased risk of cardiovascular events, including sudden cardiac death, especially in young people. A different prevalence has been reported based on the USED diagnostic modality. This study aimed to determine the prevalence and type of these anomalies using coronary computed tomography angiography (CCTA).

Methods

This single-center retrospective study was performed on 3016 consecutive cases who underwent CCTA for cardiac symptoms from March 2015 to August 2020 and the prevalence and types of CAAs were evaluated.

Results

38 cases (overall prevalence of 1.26%) including 21 men (55.3%) and 17 women (44.7%) were retrospectively diagnosed with CAAs. The most common anomalies were the Anomalous origin of LCX from the right coronary sinus (11 cases, 28.9%), Anomalous origin of RCA from the left coronary sinus (11 cases, 28.9%), and Anomalous origin of LM from the right coronary sinus (6 cases, 15.8%). There was no difference in the prevalence of CAAs in terms of patient's gender (P value=0.16) and age (P value=0.61).

Conclusion

The prevalence of CAAs among patients who underwent CCTA was 1.26%. The most common anomalies observed were the anomalous origin of the LCX arising from the right coronary sinus, the anomalous origin of the RCA arising from the left coronary sinus, and the anomalous origin of the LM arising from the right coronary sinus. These findings emphasize the importance of CCTA in detecting and characterizing coronary artery anomalies, which may have clinical implications for patient management and treatment decisions.

Prevalence and patterns of coronary artery anomalies in 28,800 adult patients undergoing angiography in a large tertiary care centre in India

Coronary artery anomalies (CAAs) are a diverse group of disorders with varied clinical presentation and pathophysiological mechanisms. A majority of these anomalies are asymptomatic and often an incidental finding on coronary angiogram or autopsy. This retrospective study included 28,800 patients who underwent coronary angiography from 2016 to 2020. The coronary angiograms were reviewed by two independent reviewers and CAAs were documented. CAAs were classified into (a) anomalies of coronary artery connection, (b) anomalies of intrinsic coronary arterial anatomy and (c) anomalies of myocardial/coronary artery interaction as proposed by the European Society of Cardiology. Of the 28,800 coronary angiograms, CAAs were present in 4.12% with anomalies in the left coronary artery (LCA) being most common. Anomalies of coronary artery connection were most common (48.48%) followed by anomalies of myocardial/coronary artery interaction (34.49%) and anomalies of intrinsic coronary artery anatomy (17.03%). Among anomalies of coronary artery connection, absent left main trunk or split LCA with separate origins of left anterior descending coronary artery and left circumflex coronary artery from the left coronary sinus of Valsalva (22.59%) was most common. An intramural course or "myocardial bridge" had an incidence of 1.16%  while incidence of coronary artery fistulae (CAF) was 0.115%.

Cardiac-CT with the newest CT scanners: An incoming screening tool for competitive athletes?

Competitive athletes of all skill levels are at risk of sudden cardiac death (SCD) due to certain heart conditions. Prior to engagement in high-intensity athletics, it is necessary to screen for these conditions in order to prevent sudden cardiac death. Cardiac-CT angiography (CCTA) is a reliable tool to rule out the leading causes of SCD by providing an exceptional overview of vascular and cardiac morphology. This allows CCTA to be a powerful resource in identifying cardiac anomalies in selected patients (i.e. unclear symptoms or findings at ECG or echocardiography) as well as to exclude significant coronary artery disease (CAD). With the advancement of technology over the last few years, the latest generations of computed tomography (CT) scanners provide better image quality at lower radiation exposures. With the amount of radiation exposure per scan now reaching the sub-millisievert range, the number of CT examinations it is supposed to increase greatly, also in the athlete's population. It is thus necessary for radiologists to have a clear understanding of how to make and interpret a CCTA examination so that these studies may be performed in a responsible and radiation conscious manner especially when used in the younger populations. Our work aims to illustrate the main radiological findings of CCTAs and highlight their clinical impact with some case studies. We also briefly describe critical features of state-of-the-art CT scanners that optimize different acquisitions to obtain the best quality at the lowest possible dose.

Myocardial bridges: A meta-analysis

Myocardial bridges are anatomical entities characterized by myocardium covering segments of coronary arteries. In some patients, the presence of a myocardial bridge is benign and is only incidentally found on autopsy. In other patients, however, myocardial bridges can lead to compression of the coronary artery during systolic contraction and delayed diastolic relaxation, resulting in myocardial ischemia. This ischemia in turn can lead to myocardial infarction, ventricular arrhythmias and sudden cardiac death. Myocardial bridges have also been linked to an increased incidence of atherosclerosis, which has been attributed to increased shear stress and the presence of vasoactive factors. Other studies however, demonstrated the protective roles of myocardial bridges. In this study, using systematic review and a meta-analytical approach we investigate the prevalence and morphology of myocardial bridges in both clinical imaging and cadaveric dissections. We also discuss the pathophysiology, clinical significance, and management of these anatomical entities.

Myocardial Bridging: A Meta-Analysis of Prevalence

The main objective of this article was to analyze prevalence data about myocardial bridging (MB) in published studies. To this purpose, we performed a meta-analysis of studies published in English literature that contained data about the prevalence of MB and its anatomical characteristics. The overall prevalence was 19% (CI: 17-21%); autopsy studies revealed an overall prevalence of 42% (CI: 30-55%), CT studies 22% (CI: 18-25%), and coronary angiography 6% (CI: 5-8%). Most bridges were located on the left anterior descending artery (82% overall, 63% on autopsy studies), had a mean thickness of 2.47 mm and a mean length of 19.3 mm. In conclusion, autopsy studies should be the gold standard in evaluating the actual prevalence of myocardial bridges, while in vivo high-resolution CT scanning should be preferred to coronary angiography studies.

Comparison of congenital coronary artery anomalies between Uyghur and Han: a multi-slice computed tomography study in Xinjiang, China

BACKGROUND

The incidence of congenital coronary artery anomalies (CCAAs) is different between ethnic groups, but there is no report about Uyghur CCAAs because of the limitation of inspection methods. This study determined the prevalence of Uyghur CCAAs and analysis the difference of CCAAs between Uyghur and Han ethnic groups by the method of multi-slice computed tomography coronary angiography (MSCTCA).

METHODS

Seven thousand four hundred and sixty-nine MSCTCA were analyzed for the CCAAs retroactively, 1934 were Uyghur patients while 4746 were Han patients. All the coronary artery images dates obtained by MSCTCA were evaluated for the CCAAs by two doctors.

RESULTS

Nineteen kinds of CCAAs were found: (1) The overall incidence of CCAAs was 2.72% (203/7469) among all patients, 2.34% (111/4746) among Han patients whereas a significant higher 3.93% (76/1934) among Uyghur patients (χ2 = 12.780,P < 0.05); (2) the incidence of CCAAs among male patients was 2.48% (76/3069) in Han while 4.33% (56/1293) in Uyghur (χ2 = 10.663, P < 0.05); (3) the incidence of CCAAs on the left side was 1.07% (51/4746) among Han patients while 2.17% (42/934) among Uyghur patients (χ2 = 12.047, P < 0.05); (4) among these 19 kinds of CCAAs, there were significant differences of the incidence of the following kinds of CCAAs between Uyghur and Han: Left coronary artery (LCA) high location (χ2 = 8.320, P = 0.004), right coronary artery (RCA) originate from left coronary sinus (χ2 = 5.450, P = 0.020), and RCA originate from left Coronary sinus + LCA high location (P = 0.024).

CONCLUSIONS

There exists some difference in CCAAs between Uyghur and Han ethnic groups. The CCAAs incidence of Uyghur is higher than that of Han, especially in male patients and on the left side; among all kinds of CCAAs, the incidence of LCA high location, RCA originate from left coronary sinus, RCA originate from left coronary sinus + LCA high locations of Uyghur is higher than Han.

Acute Anterior Myocardial Infarction Accompanied by Acute Inferior Myocardial Infarction: A Very Rare Coronary Artery Anomaly

Coronary artery anomalies are rare and mostly silent in clinical practice. First manifestation of this congenital abnormality can be devastating as syncope, acute coronary syndrome, and sudden cardiac death. Herein we report a case with coronary artery anomaly complicated with ST segment myocardial infarction in both inferior and anterior walls simultaneously diagnosed during primary percutaneous coronary intervention.

Can coronary artery anomalies be detected on CT calcium scoring studies?

PURPOSE

To determine whether coronary artery anomalies can be detected on noncontrast computed tomography (CT) coronary artery calcium scoring (CCS) studies.

MATERIALS AND METHODS

A total of 126 patients (mean age 62 years; 35 women) underwent noncontrast CCS and contrast enhanced coronary CT angiography (cCTA). Thirty-three patients were diagnosed with a coronary anomaly on cCTA, whereas coronary anomalies were excluded in 93. Two observers (reader 1 [R1] and reader 2 [R2]), blinded to patient information independently evaluated each CCS study for: 1) visibility of coronary artery origins, 2) detection of coronary anomalies, and 3) benign or malignant (ie, interarterial) course. Using cCTA as the reference standard, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CCS studies for detecting coronary anomalies were calculated.

RESULTS

Of the 33 coronary anomalies, 16 were benign and 17 malignant. Based on noncontrast CCS studies, R1 and R2 correctly identified the left main origin in 123/126 (97.6%) and 121/126 (96%) patients; the left anterior descending origin in 125/126 (99.2%) and 122/126 (96.8%); the circumflex origin in 120/126 (95.2%) and 105/126 (83.3%); and the right coronary artery origin in 117/126 (92.9%) and 103/126 (81.7%), respectively. R1 and R2 identified 34 and 27 coronary anomalies and classified 19 and 15 as malignant, respectively. Interobserver reproducibility for detection of coronary anomalies was good (k = 0.76). Interobserver agreement for detection of malignant variants was even stronger (k = 0.80). On average, coronary artery anomalies were diagnosed with 85.2% sensitivity, 96.4% specificity, 90.5% PPV, and 94.1% NPV on noncontrast CCS studies.

CONCLUSION

Benign and malignant coronary artery anomalies can be detected with relatively high accuracy on noncontrast-enhanced CCS studies. CCS studies should be reviewed for signs of coronary artery anomalies in order to identify malignant variants with possible impact on patient management.

The clinical anatomy of the coronary arteries

There are a manifold number of variations and anomalies of the origin and course of coronary arteries described in the literature. The incidence of such variations in the general population is reported to range between 0.3 and 1.6 %. Although uncommon, they may be benign or produce symptoms ranging from mild dyspnea to sudden cardiac death, and have been associated with an increased risk of accelerated atherosclerosis and perfusion defects. Thus, in order to effectively utilize the increasing number of therapeutic options available for treating coronary artery diseases, an appreciation of the likely normal and variable arrangements of the coronary arteries is essential. This review will describe the normal anatomy of the coronary arteries as well as the common variations with potential clinical effects.

Prevalence and predictors of bridging of coronary arteries in a large Indonesian population, as detected by 64-slice computed tomography scan

BACKGROUND

Multislice computed tomography (MSCT) can be used to detect myocardial bridging (MB) of coronary arteries. However, most published studies included small cohorts and did not collect data about predictors. We investigated prevalence and predictors of MB in an Indonesian population.

METHODS

All patients who had MSCT at Cinere Hospital, Jakarta, Indonesia between 2006 and 2009 were included in a prospective registry. MB was defined when at least half of the coronary artery was imbedded within the myocardium with a normal epicardial course of the proximal and distal portion.

RESULTS

Of the 934 patients (mean age 53 years, 37.8 % female), MB could be observed in 152 patients (16.3 %). Patients with MB were younger compared with those without MB. Coronary risk factors were not different between the two groups. Coronary calcifications and moderate to severe coronary stenoses were less prevalent in patients with MB, also after adjusting for differences in age. At the time of diagnosis, only a few patients with MB were treated with beta-blockers (35 %) or calcium channel blockers (13 %).

CONCLUSIONS

Prevalence of myocardial bridging as detected by MSCT is relatively high. Patients with MB were younger and had a lower prevalence of coronary sclerosis. MB could be the cause of their unexplained symptoms. Follow-up studies are necessary to assess the symptoms of these patients, their response to treatment and the incidence of (coronary) events. MSCT can be used to identify patients for potential new treatment strategies.

[Role of multidetector CT scan in the diagnosis of congenital coronary artery anomalies with inter-aortopulmonary course: about two cases and literature review]

Coronary anomalies are a rare entity. The gold standard remains the coronary angiogram. However, the identification of the origin and the course of aberrant coronary arteries using angiography may be difficult. We report two cases regarding two patients who underwent coronary angiography in order to evaluate coronary heart disease. In the first case, angiography has shown a left anterior descending artery (LAD) originating from the right anterior sinus. A multidetector CT scan (MDCT) showed an inter-aortopulmonary course of the LAD. In the second case, selective catheterization of the right coronary artery could not be done. A MDCT scan was performed. An abnormal origin of the right coronary artery was detected. It originates from the left sinus with a separate ostium of the left main coronary artery. This artery had an inter-aortopulmonary course. The 64 MDCT scan can be useful as a complementary tool for the diagnosis of coronary artery anomalies. Detection of the inter-aortopulmonary course is essential, since this situation will require surgical treatment to avoid sudden cardiac death.

Anomalous origination of a coronary artery from the opposite sinus

Anomalous origination of a coronary artery from the opposite sinus (ACAOS) is estimated to be present in 0.2-2.0% of the population. In the majority of individuals, ACAOS has no hemodynamic or prognostic implications, but in a minority of cases, typically where the anomalous coronary artery takes an interarterial course to reach its correct myocardial territory, it can precipitate ischemia and sudden cardiac death (SCD). With the growing use of CT coronary angiography (CTCA) in the investigation of ischemic heart disease, we can expect increasing rates of incidental detection of this anomaly. Although CTCA and magnetic resonance coronary angiography can effectively characterize these lesions anatomically, they fail to describe and quantitatively assess the basic defect that leads to coronary insufficiency, such as mural intussusception. The key challenge lies in the identification of which patients are at risk of SCD and, therefore, who should be offered corrective surgical or (potentially) percutaneous intervention. Conventional, noninvasive stress testing has limited sensitivity, but emerging, invasive stress tests, which utilize intravascular ultrasonography and measurements of fractional flow reserve, show the potential to provide more-accurate hemodynamic and prognostic assessment.

Successful percutaneous coil embolization of coronary-pulmonary, -carotid, and -internal mammary artery fistulas

We herein describe a 57-year-old man with coronary-pulmonary artery fistulas that had abnormal connections between the left common carotid artery and the left internal mammary artery. The patient was treated with percutaneous coil embolization using antegrade (via the coronary artery) and retrograde (via the pulmonary artery) approaches. Coronary artery fistulas have diverse anatomical variations, and it is important to thoroughly evaluate the anatomy before beginning any mode of treatment, surgical or endovascular. In the case reported herein, multislice computed tomography played a pivotal role in the preprocedure evaluation.

Aberrant right bronchial artery originating from right coronary artery - MDCT angiography findings

Aberrant bronchial arteries are rarely seen and may originate from various vascular structures. In our case, a 48-year-old man with recurrent chest pain underwent multidetector CT (MDCT) coronary angiography. MDCT images demonstrated an aberrant right bronchial artery originating from the right coronary artery. To our knowledge, this is the first case report of an aberrant right bronchial artery originating from the right coronary artery.

Right coronary artery chronic total occlusion in presence of anomalous origin of left coronary artery

Right sinus origin of left coronary artery is a very uncommon congenital coronary anomaly. The presence of an associated totally occluded right coronary artery represents an exceedingly rare picture. An accurate morphologic identification of anomalous arteries, by multi-detector computed tomography, is mandatory before planning any therapeutic intervention. We report an interesting case of chronic total occlusion of the right coronary artery in a young patient with anomalous left coronary artery.

Anomalous right coronary artery originating from the left anterior descending artery: case report and review of the literature

The anomalous origin of the right coronary artery (RCA) as a branch of the left anterior descending (LAD) artery is a very rare variation of single coronary artery. At least 36 cases have been described previously in the literature. The vast majority of previous reports have described a single anomalous vessel with its origin after the first septal perforator of the LAD, which courses anterior to the right ventricular outflow tract to reach territory normally served by the right coronary artery. Of 35 cases in structurally normal hearts, 19 (54%) patients had >50% narrowing in one or more epicardial coronary arteries (54%), at least 14 (40%) of whom required revascularization. Thirteen cases (37%) did not have significant coronary artery disease, while the remaining 3 cases were unclear. The current report reviews previous reports of this anomaly and describes a patient with an anomalous RCA from the mid-LAD, in whom heart block, back pain and dyspnea was the initial manifestation of ischemia. On heart catheterization, there was significant coronary artery disease in the LAD proximal to the origin of the anomalous artery. The patient was successfully revascularized with a unique sequential left internal mammary artery bypass to the anomalous vessel and LAD.

Aberrant crossed left circumflex and left anterior descending arteries: diagnosis with multidetector cardiac CT angiography

The multidetector coronary computed tomography angiogram findings of a rare variant crossed left circumflex and left anterior descending artery are presented. In this patient, multidetector coronary computed tomography angiogram enabled clear delineation of the aberrant coronary artery anatomy, including an estimation of patency during systole and diastole. To our knowledge, this is only the second reported case of this particular coronary artery anomaly in the world literature.

Comparison of myocardial bridging by dual-source CT with conventional coronary angiography

BACKGROUND

The diagnosis of myocardial bridging (MB) is of clinical importance because of the association between MB and compromised coronary flow. The aim of this study was to compare the ability of dual-source computed tomography (DSCT) and conventional coronary angiography (CAG) to detect MB.

METHODS AND RESULTS

DSCT were performed in 53 patients and 4-dimensional (D) reconstruction was subsequently performed in 16 patients with MB for double-blinded comparison with the findings of CAG. The diameters at systole and diastole of the coronary segments proximal and distal to the MB and of the tunneled segment were measured. The relationship between the rate of stenosis of the tunneled artery and the "milking" effect on 4-D reconstruction was analyzed. Of the 53 patients, CAG and DSCT detected 4 MBs in 3 patients and 21 MBs in 16 patients, respectively (p<0.001). On a per-patient and per-MB basis, significant difference was found between both methods (p=0.001, p<0.001). The 4-D reconstruction showed the milking effect and abnormal blood flow, detecting more MBs than did CAG (p<0.001). The rate of stenosis of the tunneled artery was related to the milking effect on the 4-D reconstruction (r=0.640, p=0.006).

CONCLUSIONS

In the present study, DSCT detected more MBs than CAG, suggesting its clinical application for diagnosis of this condition.

MDCT of the S-shaped sinoatrial node artery

OBJECTIVE

The purpose of this study was to use 64-MDCT to investigate the anatomic characteristics of the S-shaped variant of the sinoatrial node (SAN) artery and to describe the clinical implications of the findings in ablative procedures involving the left atrium.

MATERIALS AND METHODS

Coronary CT angiograms of 250 patients (152 men, 98 women; mean age, 60 +/- 12 [SD] years) were retrospectively analyzed for identification of the origin, number, anatomic course, mode of termination, and S-shaped variant of the SAN artery.

RESULTS

At least one SAN artery was detected in 244 patients. The S-shaped variant was seen in 35 (14.3%) of these patients. Thirty-four of the variants (30.6% of all left SAN arteries) arose from the proximal to middle portion of the left circumflex artery (mean distance between the ostium of the left circumflex artery and the origin of S-shaped variant, 28.7 +/- 13.1 mm). The other variant (0.7% of all right SAN arteries) originated from the distal right coronary artery. The S-shaped variant was the only artery supplying the SAN in 28 (11.4%) of the patients. In patients with two arteries supplying the SAN, the right SAN artery and the S-shaped variant of the left SAN artery were seen together in seven patients. The S-shaped SAN artery (mean distance from atrial wall, 2.43 +/- 0.992 mm) had a predictable proximal course, lying in the posterior aspect in a groove between the orifices of the left superior pulmonary vein and the left atrial appendage close to the left atrial wall. The terminal segment of the artery approached the nodal tissue posterior to the superior vena cava in 22 patients, anterior to the vena cava in 10 patients, and through branches surrounding the vena cava in two patients.

CONCLUSION

The S-shaped variation of the SAN artery is common and has a characteristic anatomic course. MDCT can be used to plan surgical and catheter-based left atrial interventions in which this artery is at risk of injury.

Coronary variants and anomalies: methodology of visualisation with 64-slice CT and prevalence in 202 consecutive patients

PURPOSE

This paper aims to provide the tools for a complete anatomical evaluation of the coronary tree using 64-slice computed tomography (CT) and evaluate the prevalence of anatomical variants and anomalies in a population of 202 consecutive patients.

MATERIALS AND METHODS

Two hundred and two patients with suspected coronary artery disease underwent 64-slice CT with a standard protocol. Two observers working in consensus evaluated and collected the data regarding anatomical variants and anomalies of the coronary vessels.

RESULTS

In the 202 consecutive patients, the prevalence of anatomical variants was: left dominant circulation (7%), absent left main (5%), presence of intermediate branch (17%), aortic origin of conus branch (13%) and circumflex origin of sinus node branch (15%). Coronary anomalies (origin and course, intrinsic and termination) showed an overall prevalence of 25%.

CONCLUSIONS

CT is the ideal method for the three-dimensional evaluation of the coronary tree. Anatomical variants and anomalies of the coronary arteries are quite common and should be known and recognised promptly by the operators.

Aberrant Origin of the Left Main Coronary Artery Arising from the Right Coronary Artery Associated with Coronary Artery Disease: A Case Report

Coronary artery anomalies are not frequent, nevertheless they are associated with increased and potentially lethal cardiac events. Recognition of these anomalies is fundamental in patients undergoing diagnostic or interventional coronary angiography. Most patients presenting with coronary anomalies are asymptomatic, but the risk of myocardial ischemia and sudden death requires the treatment of those patients. Different therapeutic options have been discussed, including surgery, conservative therapy, and interventional approaches. In this report, an aberrant origin of the left main coronary artery arising from the right coronary artery associated with coronary artery atherosclerosis and its surgical correction is described.