Coronary Artery Anomalies



Coronary Artery Anomalies


Paolo Angelini

Jorge Monge



The rich medical literature on coronary artery anomalies (CAA) suffers from many limitations, but the two main ones are

1. the superficial, general infatuation with unusual anatomy (the “fascinomas” presented in many clinical sessions), which has led to thousands of case reports but also to a disorganized and tentative literature on the subject of CAA, and

2. the lack of a clear and widely accepted conceptual organization of the knowledge in this field. For an in-depth and comprehensive review of the subject, we would refer the interested reader to a book our group published in 1999.1

In the current chapter, we briefly review contemporary information on CAA, particularly as it relates to the diagnostic and interventional activities performed in the catheterization laboratory.




DEFINITIONS

Given the great variability of coronary anatomy, a general definition of “normal” coronary arteries should be founded on the knowledge of the variations of each of the features used to describe coronary anatomy (e.g., the number and location of ostia, the diameter or cross-sectional area of coronary arteries). Generally, each descriptive feature should be considered anatomically normal when it is found in more than 1% of a general population or within 2 standard deviations of the mean value for Gaussian distribution continuous parameters.1 The most relevant clinical assessment of each anatomic variant should focus on the pathophysiological consequences of any given morphologic variation, and these consequences should be discussed separately from the variant’s anatomy.

Of the many coronary arteries, the “primary” (or elementary) ones are defined as the three main proximal arteries: one provides circulation to the anterior septum and anterior lateral wall (the left anterior descending or LAD), another provides blood flow to the obtuse marginal region of the left ventricle (the circumflex, or Cx), and the third provides circulation to the free wall of the right ventricle (the right coronary artery or RCA).1 The left main trunk may serve as a common stem that joins the LAD and Cx (a common left main stem is present in about 90% of cases and is not essential, but the LAD and Cx are essential). Normally, the LAD and Cx originate from an aortic area located above the upper or middle third of the left coronary sinus of Valsalva (also called the left posterior sinus). The right coronary artery originates from the upper or middle third of the right sinus of the Valsalva. Normally, the coronary ostia lead to an orthogonally oriented coronary proximal stem, off the aortic wall.

A popular classification of the coronary anomalies2 (Table 16.1) uses the basic features that describe each anatomic entity, especially the anomalies of origin, according to its course and destination.1,2 Figure 16.1 describes diagrammatically the normal distribution of the three primary coronary arteries in a coronal plane, and their multiple possible anomalies of origin and proximal course.

The prevalence of CAAs obviously depends on the definition of each CAA (which, unfortunately, is usually not mentioned in most reports of CAA studies). As a consequence of inadequate methodological discipline in this regard, the prevalence of CAA has been variably reported in the literature. Indeed, collecting meaningful and accurate prevalence data requires both the use of prospectively stated criteria for the diagnosis of CAA and the sampling of a general population, devoid of pretest bias. Because no such studies have been performed to date, we do not have yet credible, precise information about the prevalence of CAA in the general population; rather, most available prevalence data come from studies of patients seen in the catheterization laboratory. This type of study clearly has a referral bias but can still be important if correctly structured.1,2









Table 16.1 Classification of Coronary Anomalies






























































































































































































































































































































































































A)

Anomalies of origination and course

1)

Absent left main trunk (split origination of LCA)

2)

Anomalous location of coronary ostium within aortic root or near proper aortic sinus of Valsalva (for each artery)


a) High


b) Low


c) Commissural

3)

Anomalous location of coronary ostium outside normal “coronary” aortic sinuses


a) Right posterior aortic sinus


b) Ascending aorta, with anomalous course



(1) Intramural (ACAOS)



(2) Extramural


c) Left ventricle


d) Right ventricle


e) Pulmonary artery. Variants:



(1) LCA arising from posterior-facing sinus (ALCAPA)



(2) Cx arising from posterior-facing sinus



(3) LAD arising from posterior-facing sinus



(4) RCA arising from anterior-right-facing sinus



(5) Ectopic location (outside facing sinuses) of any coronary artery from pulmonary artery




(a) From anterior left sinus




(b) From pulmonary trunk




(c) From pulmonary branch


f) Aortic arch


g) Innominate artery


h) Right carotid artery


i) Internal mammary artery


j) Bronchial artery


k) Subclavian artery


l) Descending thoracic aorta

4)

Anomalous origination of coronary ostium from opposite, facing “coronary” sinus (which may involve joint origination or adjacent double ostia). Variants:


a) RCA arising from left anterior sinus, with anomalous course



(1) Posterior atrioventricular groovea or retrocardiac



(2) Retroaortica





(3) Between aorta and pulmonary artery,a preaortic, intramural (aortic), or ACAOS



(4) Intraseptala





(5) Anterior to pulmonary outflowa or precardiac



(6) Posteroanterior interventricular groovea




b) LAD arising from right anterior sinus, with anomalous course



(1) Between aorta and pulmonary artery, preaortic, intramural (aortic), or ACAOS



(2) Intraseptal



(3) Anterior to pulmonary outflow or precardiac



(4) Posteroanterior interventricular groove


c) Cx arising from right anterior sinus, with anomalous course



(1) Posterior atrioventricular groove



(2) Retroaortic


d) LCA arising from right anterior sinus, with anomalous course



(1) Posterior atrioventricular groovea or retrocardiac



(2) Retroaortic



(3) Between aorta and pulmonary artery,a preaortic, intramural (aortic), or ACAOS



(4) Intraseptal



(5) Anterior to pulmonary outflowa or precardiac



(6) Posteroanterior interventricular groovea




e) LCA arising from the “non-coronary” sinus, with anomalous course



(1) Intramural (ACAOS)



(2) Extramural

5)

Single coronary artery


B)

Anomalies of intrinsic coronary arterial anatomy

1)

Congenital ostial stenosis or atresia (LCA, LAD, RCA, Cx)

2)

Coronary ostial dimple

3)

Coronary ectasia or aneurysm

4)

Absent coronary artery

5)

Coronary hypoplasia

6)

Intramural coronary artery (myocardial bridge)

7)

Subendocardial coronary course

8)

Coronary crossing

9)

Anomalous origination of posterior descending branch or septal penetrating branch

10)

Absent PD or split RCA


a) Proximal + distal PDs, arising from separate RCA sources


b) Proximal PD arising from RCA, distal PD arising from LAD


c) Proximal PD arising from RCA, distal PD arising from Cx

11)

Absent or split LAD


a) Large first septal branch and small distal LAD


b) Double LAD

12)

Ectopic origination of first septal branch


C)

Anomalies of coronary termination

1)

Decreased number of arteriolar/capillary ramifications (hypothetical)

2)

Fistulas from RCA, LCA, or infundibular artery to


a) Right ventricle


b) Right atrium


c) Coronary sinus


d) Superior vena cava


e) Pulmonary artery


f) Pulmonary vein


g) Left atrium


h) Left ventricle


i) Multiple microfistulas draining into one or both ventricles


D)

Anomalous collateral vessels


a If a single, common ostium is present, the pattern is considered to represent “single” coronary artery. ACAOS, anomalous origin of a coronary artery from an opposite sinus of Valsalva, with intramural course; ALCAPA, anomalous origin of the left coronary artery from the pulmonary artery; Cx, circumflex; LAD, left anterior descending coronary artery; LCA, left coronary artery; PD, posterior descending branch; RCA, right coronary artery.



Recently, our Center for Coronary Artery Anomalies at the Texas Heart Institute has spearheaded a comprehensive process of acquiring definitive data regarding the prevalence of CAA by collecting magnetic resonance imaging data in a large population of schoolchildren. In addition, our group has previously performed a prospective study of adult patients examined or treated in the cardiac catheterization laboratory. The findings indicated that the prevalence of CAA in our cohort was 5.64%.2 Most of the previous, uncontrolled studies produced a wide range of unreliable prevalence data.3, 4, 5, 6

Of the 66 different types of CAA (Table 16.1), only one subgroup is considered to intrinsically pose any risk of causing coronary dysfunction (i.e., ischemia): the anomalous origin of a coronary artery from an “opposite” sinus of Valsalva, with an intramural course (ACAOS).7 Such anomalies are found in approximately 1% of adult cardiac catheterization laboratory patients2; these anomalies are discussed in detail in the next section, which covers most of the important clinical issues in adult cases of CAA. Most of the other CAA variants are not known to cause ischemia by themselves (and these non-ACAOS CAA should not be included in a discussion of clinically important CAA in the adult), but they could have clinical consequences because of clinical uncertainty about their recognition and management and because of occasional complicating factors (the most frequent of which is associated coronary artery atherothrombotic disease). Hence, the primary responsibility of a cardiologist in the adult catheterization laboratory is to properly diagnose each form of CAA and then to establish the severity of each case.


Anomalous Origin of a Coronary Artery from an Opposite Sinus of Valsalva, with an Intramural Course

As confirmed by most autopsy-based studies on the subject,8, 9, 10 ACAOS is the only kind of CAA with a clear ischemic
potential. This anomaly is especially critical to recognize because of its mortality implications in the young, specifically in athletes and military recruits, as well as because of its potential to cause disabling angina, dyspnea, and syncope. Anatomists have long debated the mechanisms and specific anatomic features of ACAOS that may lead to critical ischemia. Initially, a slit-like orifice, tangential orientation of the origin, a passage between the aorta and the pulmonary artery, or ostial fibrous ridges were implicated in the causation of ischemia in ACAOS cases. More recently, accurate in vivo imaging of such anomalies by intravascular ultrasound (IVUS), as well as some anatomic evidence, has led to the clear conclusion that the intramural proximal course of the ectopic ACAOS coronary artery, inside the aortic wall, is the recurrent and quantifiable mechanism of ACAOS-related ischemia (Figures 16.2, 16.3, 16.4, 16.5 and 16.6).

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Jun 26, 2016 | Posted by in CARDIOLOGY | Comments Off on Coronary Artery Anomalies

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