Intercoronary Anastomosis: A Rare Angiographic Finding to be Differentiated From Coronary Collaterals

Note: Video is available for this case.

Introduction

Anastomotic connections between normal coronary arteries have been observed in coronary angiography, mostly on postmortem examinations, but rarely in living adults.¹ The presence of a large-caliber intercoronary artery connection, defined as an open-ended circulation with bi-directional blood flow between two coronary arteries², is a very rare variant of the coronary circulation and its exact prevalence is unknown. Intercoronary anastomosis should not be confused with collateral arteries, which have distinct angiographic features and underlying pathophysiological mechanisms. We present a case of a rare intercoronary anastomosis in the absence of significant obstructive coronary artery disease. 

Case presentation

A 55-year-old man with no known coronary artery disease presented to an outside hospital with chest tightness, shortness of breath, lightheadedness, and sweating. An initial resting electrocardiogram (ECG) revealed a regular, wide complex tachycardia with a heart rate of 200 beats per minute and underlying right bundle branch block (RBBB). His rhythm spontaneously converted back to normal sinus while on intravenous diltiazem. The patient was referred to our hospital for further evaluation and management. He had a history of hypertension, dyslipidemia, diabetes mellitus, and a remote history of smoking. Physical examination was unremarkable. Lab testing revealed a peak troponin of 2.79. Given his risk factor profile, the wide complex tachycardia and his cardiac enzymes, it was elected to proceed with coronary angiography, which revealed non-obstructive coronary artery disease. However, during selective coronary angiography of the left system, retrograde filling of the distal right coronary artery (RCA) was noted (Figure 1). In addition, selective coronary angiography of the right system showed retrograde filling of the distal circumflex artery (Figure 2). 

Given the patient’s clinical presentation, lingering concerns regarding non-visualized stump occlusions, and the possibility that these channels represented collateral flow, simultaneous bilateral coronary angiography was performed after contralateral sheath insertion. Simultaneous injection of contrast material into both coronary arteries demonstrated interarterial continuity between the distal right coronary artery and distal circumflex (Figure 3), with no evident occlusions.

The patient subsequently underwent an electrophysiology study that revealed inducible, sustained ventricular tachycardia that originated from the base of left ventricular outflow tract. After the first radiofrequency ablation procedure, a second electrophysiology study two weeks later confirmed no further inducible ventricular tachycardia. The patient was maintained on a β-blocker, calcium channel blocker, aspirin, and his other anti-hypertension medications, and has remained symptom-free since.

Discussion

Prominent anastomosis between the right and left coronary arteries presents during fetal life and persist in to the postnatal period, but normally diminishes in caliber by the eighth month.³ Small intercoronary communications can exist in normal adult hearts, but are usually less than 200 µ in diameter and unidentifiable by angiography, probably due to minimal to no flow across and by the limitations inherent to imaging resolution.³ Prominent intercoronary artery continuity or coronary cascade demonstrated by angiography is a very rare variant of the coronary circulation and its exact prevalence is unknown, but probably less than 0.05%.³ Two types of have been described: communication between the left circumflex and the right coronary artery in the posterior atrioventricular groove as described in our case, and communication between the anterior descending and posterior descending artery in the distal portion of the posterior interventricular groove.⁴ It is important to note that intercoronary communication in the absence of obstructive coronary artery disease should not be confused with collateral anastomoses seen in the presence of occlusive coronary artery disease. Compared with collaterals that consist of one or more small, tortuous channels of different sizes and lengths, intercoronary arterial connections are larger in diameter (> 1 mm), extramural, and straight. Furthermore the histological structure of intercoronary arterial connection is typical of an epicardial coronary artery, with a well-defined muscular layer.²

Increased intercoronary anastomoses have been shown in patients with cor pulmonale, severe anemia, and cardiac hypertrophy, as well as in patients with obstructive coronary artery disease, suggesting that relative cardiac ischemia may be the common underlying stimulus for the development of these anastomotic channels. However, in the absence of severe obstructive coronary artery disease, intercoronary arterial connections are thought to be related to the persistence of congenital anastomoses that fail to recede.² It is suggested that faulty embryological development allows the existing intercoronary channel to remain prominent and maintain a large caliber. In our patient, the absence of significant obstructive coronary artery disease as evidenced by coronary angiography, absence of left ventricular hypertrophy on echocardiography, and the absence of anemia or cor pulmonale suggest that this large intercoronary anastomosis is likely congenital in origin. The functional significance of this large anastomotic connection between normal coronary arteries is unclear. It may play a protective role, because if an obstructive lesion develops proximally in one of the two coronary vascular territories, this large connection with bi-directional blood flow can provide additional perfusion and would be beneficial in preventing myocardial ischemia or infarction in the diseased territories.⁵ Conversely, a prior case report described a left anterior descending artery-posterior descending artery continuity that did not prevent extensive transmural infarction in the distribution of the posterior descending artery.⁶ Another suggested a potential “coronary steal” phenomenon caused by unidirectional intercoronary communication that in fact contributed to myocardial ischemia.⁴ In our patient’s case, a possible “coronary steal” phenomenon resulting in myocardial injury, as indicated by the increased troponin, cannot altogether be excluded. However, a more likely explanation would be supply-demand mismatch, given significant tachycardia in the presence of non-significant coronary disease.

Conclusion

Intercoronary anastomosis is a very rare entity with unclear functional significance. It should not be confused with collaterals; the absence of obstructive disease and angiographic characteristics aid in this differentiation. In the absence of the above-mentioned disorders, it may represent a congenital anatomic variation. The functional significance of intercoronary continuity, however, remains controversial.

Disclosure: The authors report no conflicts of interest regarding the content herein.

This article received a double-blind peer review from members of the Cath Lab Digest editorial board.

The authors may be contacted via Kun Xiang, MD, PhD, at: kun.xiang@utoledo.edu

Note: Video is available for this case.

References

1. Reig J, Jornet A, Petit M. Direct connection between the coronary arteries in the human heart. Intercoronay arterial continuity. Angiology. 1995; 46(3): 235-242. 
2. Sokmen A, Tuncer C, Sokmen G, Akcay A, Koroglu S. Intercoronary communication between the circumflex and right coronary arteries: a very rare coronary anomaly. Hellenic J Cardiol. 2009; 50(1): 66-67.
3. Voci G, Patel RB, Trivedi AD, Patel PV, Burris AC, Ruby SR. Angiographic demonstration of congenital intercoronary communication in normal adults. Am J Cardiol. 1987; 59(12): 1205-1206.
4. Gur M, Yilmaz R, Demirbag R. Unidirectional communication between the circumflex and right coronary arteries: a very coronary anomaly and cause of ischemia. Int J Crdiovasc Imaging. 2006; 22: 339-342.
5. Esente P, Gensini GG, Giambartolomei A, Bernstein D. Bidirectional blood flow in angiographically normal coronary arteries. Am J Cardiol. 1983; 51: 1237-1238.
6. Donaldson RF, Isner JF. Intercoronary continuity: An anatomic basis for bidirectional coronary blood flow distinct from coronary collaterals. Am J Cardiol. 1984; 53: 351-352.