Sudden Cardiac Death and Anomalous, Aortic Origin, Coronary Arteries

Coronary artery anomalies (CAA) are the second most common cause of exercise-related deaths in competitive athletes accounting for 17%¹, with SCD the presentation in half of these cases. The true prevalence is unknown with data from retrospective angiographic or autopsy studies. There is significant uncertainty about which phenotypes are malignant, which can be discharged, require follow up or corrective intervention and how they should be investigated. Here we discuss the state of the art and the future directions.

The true incidence is unknown- with retrospective invasive angiographic studies suggesting an incidence of 0.3-5.6% and autopsy studies quoting 1%- both prone to referral bias³.

The aims, therefore, of this article are to summarise the known malignant anomalies, the factors with unknown risks and consensus recommendations.

Nomenclature

Anatomical classification aims to describe the origin, the ostium and finally the course (see figure 1). The nomenclature described here is adapted from Angelini². In normality the coronary anatomy consists of 2-4 ostia with arteries arising from the right and left sinuses of Valsalva at an orientation of 45-90deg from the aortic wall². The different descriptive terms used are summarised in Table 1.

Table 1: Nomenclature of origin, ostium and course adapted from Angelini²

Figure 1:

Reproduced with permission from McLarry et al. Copyright ©The Author(s) 2015. Published by SpringerLink Publishing Group Inc. All rights reserved.

Figure 1¹⁶: Normal coronary artery origin and course contrasted with several varieties of AAOCA. a Normal coronary artery origin and course. b Anomalous origin of the LCX from the RCA with a posterior (retroaortic) course; this is more commonly encountered than AAOCA of the LCX from the right sinus of Valsalva. c AAOCA of the LM with an anterior (prepulmonic) course. d AAOCA of the LM with a posterior (retroaortic) course. e AAOCA of the LM with a subpulmonic (intramyocardial) course. f AAOCA of the LM with an interarterial course. g AAOCA of the RCA with an interarterial course. LCX left circumflex coronary artery, RCA right coronary artery, LAD left anterior descending artery.

Mechanisms of SCD

On the basis of anatomical patterns associated with exercise related SCD involving Anomalous, Aortic origin, coronary arteries (AAOCA), reports in the medical literature highlight the association of slit-like orifice, acute angle take off, interarterial or intramural course⁴ (see figure 2). The mechanism is thought to involve exceptional ischaemia and malignant arrhythmia from compression of coronary artery between aorta (Ao) and pulmonary artery (PA) (interarterial course), ostial occlusion during exertion (slit-like orifice and acute angle take off) or proximal segment occlusion (intramural course in the aortic wall).

In the case of SCD at rest it is postulated that chronic ischaemia and fibrosis in the territory supplied gives rise to malignant arrhythmia².

Figure 2:

Reproduced with permission from McLarry et al Copyright ©The Author(s) 2015. Published by SpringerLink Publishing Group Inc. All rights reserved.

Figure 2: A 71-year-old female presented with exertional chest pain and underwent coronary CTA which demonstrated AAOCA of the right coronary artery. a An oblique sagittal maximum intensity projection image demonstrates the acute angle of takeoff and a slit-like orifice of the anomalous right coronary artery (arrowhead) as it courses between the aorta and the pulmonary artery. b The oblique coronal multiplanar reformat demonstrates lateral luminal compression of the anomalous right coronary artery (arrow), suggestive of an intramural course. c The luminal shape and diameter are restored distally (arrow) as it exits the intramural portion. This AAOCA with an interarterial course is considered malignant and is associated with increased risk of sudden cardiac death. Ao aorta, PA pulmonary artery. ¹⁶

Anomalous Aortic Origin Coronary Arteries: Subtypes, Incidence and Case Reports

The commonest anomalies are separate left anterior descending artery (LAD) and left circumflex (LCx) ostia (0.67%) from the left sinus of Valsalva (LSV) and LCX arising from the right coronary artery (RCA) or right sinus of Valsalva (RSV) (0.67%)⁵.

A single case report of SCD in the medical literature has been associated with separate LAD and LCx ostia⁶. The case was a 24 year old man with failed resuscitation after being found collapsed in a swimming pool at a party with significant alcohol levels on a toxicology report. The case was interesting in that the LAD took an unusual interarterial course. There were areas of fibrosis in the anterior wall suggestive of chronic ischaemia giving rise to arrhythmia.

All published cases of LCx from RSV or as a branch of the RCA describe the circumflex artery taking a retroaortic course (see figure 3) with no cases of SCD found on literature search for this article.

Figure 3: Schematic representation of left circumflex artery arising from right coronary artery³.

RCA: Right coronary artery; LAD: Left anterior descending; LCX: Left circumflex; R: Right sinus of Valsalva; L: Left sinus of Valsalva; N: Non-coronary sinus; PA: pulmonary artery.

Copyright © The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.

Anomalous left coronary artery from the right sinus of Valsalva (ALCA-R) includes an ectopic LMS from the RSV (ostium separate from RCA ostium), confluent ostia or single coronary artery (single ostium) with an incidence of 0.15%. This is the classically described malignant anomalous coronary artery and is the most commonly described AAOCA associated with sudden cardiac death⁷. Most frequently the left system passes interarterially. SCD is reported at rest and with exercise⁴.

Figure 4¹⁶: A 55-year-old female presented with exertional syncope. The evaluation culminated in a coronary CTA that demonstrated an anomalous left main coronary artery arising from the right sinus of Valsalva and coursing between the aorta and pulmonary artery. a The three-dimensional volume-rendered image demonstrates the malignant interarterial course of the anomalous left main (arrow) coronary artery between the aorta and pulmonary artery (subtracted to visualize the left main). b The maximum intensity projection image demonstrates the acute angulation, slit-like ostium, and the anomalous course of the left main coronary artery (arrow) between the aorta and pulmonary artery. The interarterial form of AAOCA is associated with an intramural course that leads to coronary intussusception with exertion, luminal compression, critical reduction of flow, and an increased risk for sudden cardiac death. Ao aorta, PA pulmonary artery.

Reproduced from McLarry et al Copyright ©The Author(s) 2015. Published by SpringerLink Publishing Group Inc. All rights reserved.

Anomalous right coronary artery from the left sinus of Valsalva, ARCA-L, (single coronary artery or separate ostia) is many times more common than ALCA-R yet is significantly less frequently associated with SCD⁷. The SCD medical literature in this group generally describe high risk anatomical features as being an acute angle take off, intramural or interarterial course⁴.

The medical literature of RCA and LMS from posterior Sinus of Valsalva (PSV) yields one report worldwide. SCD in a 16 year old occurred whilst playing basketball having experienced syncope during exertion 2 weeks prior ⁸. There was no interarterial course but an acute angle take off of the LMS (<45deg) was reported.

Consensus Statements

2 documents provide guidance on competitive sport and surgical intervention in AAOCA respectively.

The AHA consensus document⁹ recommends athletes with ARCA-L should be evaluated by exercise stress testing. Return to competitive sport can be considered with a negative stress test after adequate counselling as to risk and benefit, taking into consideration the uncertainty of accuracy of a negative stress test (Class IIa; Level of Evidence C). Symptoms, arrhythmia or ischaemia on exercise stress testing should result in restriction from competitive sport before surgical repair (Class III; Level of Evidence C).

Athletes with an ALCA-R, found incidentally or associated with symptoms, should be restricted from participation in all competitive sports before surgical repair (Class III; Level of Evidence B)⁹.

In 2008 an executive summary by the ACC and AHA gave recommendations for AAOCA¹⁰ with particular reference to surgical intervention:

• Coronary artery origins and course should be assessed in: aborted SCD or life threatening arrhythmia, unexplained coronary ischaemic symptoms or unexplained LV dysfunction (Class I; Level of Evidence B).
• Surgical revascularisation should be performed in ALCA-R coursing between Ao and PA or ARCA-L coursing between Ao and PA with evidence of ischaemia (Class I; Level of Evidence B).

Gaps in the Evidence

Functional testing

Functional testing plays an uncertain role in the management of AAOCA. Whilst it is integrated in the above consensus documents, functional testing will not identify exceptional ischaemia- defined as myocardial ischaemia occurring very rarely and without consistency. Furthermore, given the fact that athletes with AAOCA suffering exercise related SCD often train at or at a greater intensity relative to the index event what is the value of a negative stress test?

Age

With the recent change by the UK national guidance body- The National Institute for Health and Care Excellence (UK NICE)  regarding the management of  recent onset chest pain and proposed increased use of computer tomography coronary angiography (CTCA), the significance of finding AAOCA in patients >35 years old without evidence of atherosclerotic lesions is an important unknown particularly as this group has a much lower incidence of SCD⁴ and much less certain surgical benefit¹¹.

Optimal intervention

What is the long term durability of a bypass graft onto an artery experiencing exceptional ischaemia and therefore competitive flow? Atresia in the RIMA graft to ARCA-L has been reported in several analyses of this technique¹². Two surgical series of AAOCA^13,11 describe ligation of the anomalous artery after grafting or use of alternative repair operations. However, it should be noted, no positive impact has been demonstrated when comparing long-term surgical outcomes against conservative management¹¹. Furthermore, surgical intervention is not risk free and must be balanced against the unknown natural history of AAOCA on one hand and the psychological impact of living with the potential of SCD on the other¹⁴.

With the above unknowns the Texas Children’s Heart Center has developed a Coronary Anomalies Program¹⁵ aiming to produce a registry of anomalies and an MDT process to manage them by consensus. According to their decision pathway ALCA-R is managed surgically however not by CABG but by unroofing intramural segments, neo-ostium creation, coronary translocation or ostioplasty.

All other AAOCA lacking high risk anatomical features or proven ischaemia on functional testing are closely followed up. Of note the programme will only consider surgical intervention in the >35yrs age group on a case by case basis.

Conclusions

AAOCA is the second most common cause of sudden cardiac death (SCD) in competitive athletes.

The low prevalence of AAOCA, risk of associated SCD and lack of data to guide treatment and lifestyle modification make its management particularly taxing.

ALCA-R, symptomatic anomalies with slit-like orifice, intramural or interarterial course should be considered malignant with consideration of surgical management in those less than 35 years of age.

Integration of functional testing into a clinically useable algorithm is unproven as is the surgical management in those over 35 years old.

In the long term, with the uncertainties in the field, a UK wide registry with standardisation of anatomical description and MDT decision making with involvement of pathologists, cardiologists, surgeons and radiologists may help understand the true prevalence and malignancy of the condition.

References

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