Coronary Artery Anomalies of Termination: Fistulae and Arteriovenous Malformations

Coronary Artery Fistulae

A coronary artery fistula (CAF) is a solitary communication between a coronary artery and one of any of the following: cardiac chambers or arterial venous, coronary venous, or pulmonary arterial conduits—that is, a disorder of coronary artery termination. Coronary artery fistulae also may be of anomalous origin.

The incidence of CAFs in the population is unknown. The incidence within angiographic series is 0.1% to 0.2%, second in frequency of all coronary artery congenital abnormalities, after anomalous origin of the coronary arteries.

Coronary fistulae usually are congenital, but occasionally they may be posttraumatic or iatrogenic.

Most congenital coronary fistulae drain into adjacent cardiac chambers or vessels:

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The right heart atrium
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The right ventricle
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The pulmonary arteries
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The coronary sinus
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The superior vena cave: right atrial junction
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The hepatic veins
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The bronchial arteries

The incidence of multiple or large fistulae is approximately 0.05%, and the incidence of small fistulae is approximately 0.1% to 0.4% of angiographic series.

The right heart receives the drainage of 90% of congenital coronary artery fistulae; however, some congenital coronary artery fistulae may drain into the left heart.

Congenital fistulae may arise from:

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The left coronary artery: 50% to 60%, more commonly in the left anterior descending artery (LAD) than in the left circumflex artery (LCX)
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The right coronary artery (RCA): 30% to 40%
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Both coronary arteries: 2% to 5%

Although the RCA and LAD are the most commonly involved vessels, left circumflex coronary artery fistulae do occur, with drainage into sites such as the right atrium, the coronary sinus, and even the uncommon site of the left ventricle.

Multiple microfistulae from the coronary artery to the left ventricle have been described, arising off the distal portion of the coronary arteries. These have a female preponderance.

Typically, congenital coronary artery fistulae are conspicuously tortuous and have resulted in dilation (“flow-dependent dilation”) of the coronary arteries that feed them.

Most coronary artery fistula are asymptomatic. Potential complications are listed in the next sections of this chapter. Ischemia within the territory of the fistula may be detected scintigraphically or by evidence of prior infarction within the territory. In the absence of angiographically evident disease within the artery or fistula, the findings of ischemia or infarction likely implicate the fistula. Although the diagnosis of coronary steal is not easy to establish, it has been demonstrated in the setting of coronary fistula.

Spontaneous closure of congenital coronary fistulae has been reported.

Visualization of the distal portions of fistulae by CCT, especially if small, may be incomplete.

Etiologies of Coronary Artery Fistula

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Congenital
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Acquired
- Iatrogenic
  - Aortocoronary bypass grafting
    - Aortopulmonary artery
    - Coronary artery-to-vein fistula
  - Congenital heart surgery repair
  - Post- myotomy or post-myectomy for hypertrophic obstructive cardiomyopathy
  - Endomyocardial biopsy
  - Maze procedure
- Aortic dissection
- Penetrating trauma
- Coronary artery dissection with rupture into an adjacent structure
- Coronary artery aneurysm with rupture into an adjacent structure
- Atherosclerosis
- Takayasu arteritis
- Neovascularization into a large left atrial thrombus

Potential Complications

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Volume overload pathophysiology: congestive heart failure
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Infection: endovascular/endocarditis
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Coronary steal pathophysiology
- Ischemia
- Angina
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Arrhythmia
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Syncope
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Aneurysm formation of the fistula
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Fistula rupture
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Fistula dissection
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Effusion
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Tamponade
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Hemorrhage/hematoma within the pericardial space
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Giant enlargement with compression of adjacent structures
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Coronary artery to left ventricular false aneurysm fistula

Patterns of Coronary Artery Fistulae

Coronary artery fistulae may occur in one or more permutations of:

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Source artery or arteries
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Drainage chamber(s) or venous structure(s)
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Absence or concurrence of congenital heart disease
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Absence or concurrence of acquired heart disease(s)

Hence, one fistula may drain into more than one low-pressure structure, and more than one fistula may drain into a single low-pressure structure, in the presence or absence of congenital or acquired heart disease.

Although the generalities of RCA and LAD source to right-sided or venous structures is the general rule, the range of permutations is vast and still incompletely known. A small sampling of infrequent but notably complex cases includes the following:

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Coronary artery to coronary sinus fistula (CACSF) may occur in association with congenital stenosis of the coronary sinus ostium and retrograde drainage via a persistent left superior vena cava.
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A case with four coronary to pulmonary artery fistulae also has been detailed.
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Coronary artery fistulae have been described in hypertrophic cardiomyopathy and mitral stenosis.

Potential CTA Findings of Coronary Artery Fistula

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Generally enlarged feeder vessel size
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Tortuosity of the fistula
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Aneurysm of the fistula
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Calcification of the fistula, generally in its dilated or aneurysmal portions
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Differential contrast/attenuation marking the site(s) of return of the fistula into chambers or vessels with lower attenuation
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Visualization of the surrounding chambers and hence the path of the fistula. The ability of cardiac CT to image the surrounding anatomy directly is the principal advantage when compared with conventional angiography, as is the overall robustness to manipulate a volumetric data set to solve the details of:
- Fistula source
- Fistula course
- Fistula site of termination
- Fistula complications such as aneurysm, calcification, thrombosis, hemorrhage

Treatment

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Asymptomatic/small size: observation
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Asymptomatic/large size: intervention advocated by some
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Symptomatic/large size: consideration of intervention

Potential Interventions

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Endovascular
- Coiling (currently the most common catheter-based intervention)
- Otherwise: device closure, detachable balloons, plugs, various chemicals
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Surgical
- Ligation
- Ligation with bypass

Variants of CAF are illustrated as follows:

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CAF arising from the right coronary artery: Figures 10-1 and 10-2 and ,
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CAF arising from the left circumflex coronary artery: Figures 10-3 through 10-6 and , , , ,
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CAF arising from the left main stem coronary artery: Figure 10-7 and ,
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CAF draining into the pulmonary artery: Figures 10-8 through 10-14 and ,
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Infected CAF: Figures 10-15 and 10-16 and .

$Figure 10-16, A 50-year-old man was involved in a high-speed motor vehicle accident. A and B, Axial CT images from a pan scan study done for trauma evaluation. An unusual-appearing curvilinear vascular structure was seen in the posterior aspect of the heart extending into the left atrioventricular groove. There was no evidence of a pericardial effusion or pericardial thickening. A, A transverse, minimally displaced rib fracture of one of the left mid ribs. A moderate-sized lung contusion is seen in the left lower lobe ( B ). Because of the uncertain etiology of the mediastinal vascular structure, a gated cardiac CT was performed. C and D, Volume-rendered images demonstrate a large tortuous vascular structure to be the circumflex coronary artery. E, The sagittal oblique maximum intensity projection image shows the tortuous circumflex artery confluence into the coronary sinus, confirming that this represents a congenital coronary artery to coronary sinus fistula, an incidental finding in this patient with thoracic trauma. See Video 10-12.$
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Iatrogenic CAF arising from septal branches of the LAD post-myotomy/myectomy: Figure 10-17
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Coronary artery to left ventricle fistulae: Figures 10-18 and 10-19 .