Stolen from the coronaries: Left-to-Left shunts presenting as chest pain syndrome!

Abstract

We present the case of a 61-year-old woman with chest pain syndrome. Cardiac catheterisation did not reveal atherosclerotic coronary disease. However, a haemodynamically significant fistula connecting the left coronary artery to the left atrial appendage was found to be the culprit through a left-to-left shunting mechanism. In this report, we review the pathophysiology of coronary artery fistulas and the mechanism by which these fistulas may lead to ‘coronary steal syndrome’. Indications for interventional and surgical management are outlined. Ultimately, we suggest the consideration of coronary artery fistulas in the differential diagnosis of patients presenting with chest pain.

Background

A coronary artery fistula (CAF) is an anomalous vascular connection that links coronary arteries to a cardiac chamber and/or the great vessels.¹ Often the result of a congenital malformation, they have a prevalence of approximately 0.002% in the general population.^{2 3} In approximately 50% of patients with CAFs, the fistulas arise from the right coronary artery (RCA) and in approximately 42% of patients, they arise from the left coronary artery (LCA).⁴ CAFs that arise from both the RCA and LCA are quite rare, with only 5% of patients demonstrating such a connection.⁴ Most fistulas (90%) drain into the venous circulation, with the most common sites being the: right ventricle (41%), right atrium (26%), pulmonary artery (17%), coronary sinus (7%), left atrium (5%), left ventricle (3%) and superior vena cava (1%).⁵

Our case report illustrates chest pain syndrome in a patient, in whom cardiac catheterisation showed a double shunt in parallel; one fistula arising from the separate os in the right coronary sinus to the left atrial appendage (LAA) and another one arising from the proximal left anterior descending artery (LAD) connecting to the LAA. We outline the pathophysiology and haemodynamics of these uncommon shunts and mechanisms of steal syndrome. Rationale for therapy and therapeutic modalities are discussed with emphasis on coil embolisation therapy.

Case presentation

A 61-year-old woman with a history of hypertension and dyslipidaemia presented to the emergency room with sudden onset chest pain. She was a non-smoker and had no family history of coronary artery disease or diabetes. Her presentation was concerning for acute coronary syndrome (ACS) and featured substernal chest pain radiating to the left arm and jaw, as well as diaphoresis. The patient had no prior episodes of chest pain and was on ramipril 10 mg daily at the time of admission. Vital signs included a blood pressure of 130/70 mm Hg, heart rate of 70 beats/min, respiratory rate of 16, and blood oxygen saturation of 96% on room air. Cardiovascular examination was unremarkable, jugular venous pressure was normal and heart sounds were audible in all areas without any murmurs or rub.

Investigations

Investigations revealed elevated initial troponin of 71 ng/L (normal <14 ng/L), creatine kinase of 73 U/L (normal 30–200 U/L), and complete blood count and electrolytes were all within normal limits. ECG showed a rate of 60 beats/min with no signs of ischaemia or infarction. Echocardiogram revealed a left ventricular ejection fraction of 60% with no wall motion abnormalities or signs of valvular heart disease. Right ventricular systolic pressure was mildly elevated at 33 mm Hg.

The patient was admitted and the ACS pathway protocol was initiated with a cardiac catheterisation to follow. She was started on acetylsalicylic acid 81 mg, clopidogrel 300 mg loading dose, metoprolol 25 mg two times a day, atorvastatin 80 mg, ramipril 10 mg and intravenous heparin. Catheterisation did not reveal any atherosclerotic plaque/plaque rupture. However, two fistulas were demonstrated, one connecting the proximal portion of the LAD to the pulmonary artery (figure 1, video 1), and another connecting the RCA to the pulmonary artery (figure 2, video 2).

Figure 1.

Coronary angiogram image (right anterior oblique view) showing arteriosinusoidal fistula (white arrow) from proximal portion of the left anterior descending artery (red arrow) to the pulmonary artery.

Video 1.

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DOI: 10.1136/bcr-2021-242425.video01

Figure 2.

Coronary angiogram image (left anterior oblique view) showing a fistula arising from separate os in the right coronary sinus (red arrow) and terminating in the left atrial appendage via arteriosinusoids (white arrow). Proximal aspect of right coronary artery shown with yellow arrow.

Video 2.

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DOI: 10.1136/bcr-2021-242425.video02

To determine the functional impact of these fistulas, the patient underwent exercise stress echocardiography. The patient exercised on the supine bicycle for a total of 6 min. She developed stress-induced chest tightness, ECG changes and wall motion abnormalities in the circumflex territory consistent with ischaemia. These findings explain coronary steal due to fistula affecting the circumflex territory first. The other territories may also be affected but given the triad of symptoms, ECG changes and echocardiographic abnormalities, the test was stopped at this relatively low workload (figure 3, videos 3 and 4). Given the clinically, electrocardiographically and echocardiographically positive stress echocardiogram, the patient was subsequently booked for a repeat catheterisation with the intent to embolise the LAD to pulmonary artery fistula to provide symptom relief.

Figure 3.

Pictorial representation of myocardial wall motion scoring on stress echocardiography in the long axis (LAX), short axis (SAX), 4-chamber (4C) and 2-chamber (2C) views. Note that row I denotes wall motion scoring at rest and row II denotes wall motion scoring during exercise. The middle posterior and lateral wall motion are noted to be hypokinetic during exercise.

Video 3.

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DOI: 10.1136/bcr-2021-242425.video03

Video 4.

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DOI: 10.1136/bcr-2021-242425.video04

To further define the anatomy and definitive course of the fistulas, in anticipation of coil embolisation, a CT angiogram was done. This showed that the LAD fistula ended in a serpiginious region of vessels left lateral to the main pulmonary artery and connecting to the tip of the LAA (figure 4). Importantly, the RCA fistula originated from a separate os in the right coronary sinus but terminated at the same region in the LAA (figure 5). Given its origin from a separate os, the RCA fistula was deemed unlikely to be causing coronary steal.

Figure 4.

CT angiogram image showing arteriosinusoidal fistula (white arrow) from left anterior descending artery to left atrial appendage. LAD, left anterior descending artery; RCA, right coronary artery.

Figure 5.

CT angiogram image showing arteriosinusoidal fistula (white arrow) arising from right coronary artery (RCA) ostium to left atrial appendage. LAD, left anterior descending artery.

Treatment

Twelve hydrostatic embolisation coils were deployed via a guiding catheter in the aneurysmal segment of the LAD fistula with successful occlusion of the same. There were no immediate postprocedure complications (figure 6, video 5). Patient was discharged home on ramipril 10 mg daily and bisoprolol 2.5 mg daily.

Figure 6.

Coronary angiogram image (30° right anterior oblique and 20° caudal angulation view) showing post coiling embolisation (white arrow) of arteriosinusoidal fistula (blue arrow) arising from proximal portion of the left anterior descending artery (red arrow). Left circumflex artery shown with yellow arrow.

Video 5.

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DOI: 10.1136/bcr-2021-242425.video05

Outcome and follow-up

The patient was reviewed as an outpatient 6 months and 1 year post procedure. She was doing very well from the cardiovascular standpoint, with good aerobic capacity. Stratification with exercise stress test was clinically and electrically negative at moderate workload. Repeat echocardiogram showed normal biventricular systolic function and normal valvular function. She is awaiting an outpatient CT angiogram.

Discussion

CAFs with the cardiac chambers, also known as cameral fistulas, are rare with a reported incidence of about 0.08%–0.3% in patients undergoing diagnostic left heart catheterisation.^{6 7} Arterioluminal fistulas have a direct and focal communication with the concerned cardiac chamber whereas arteriosinusoidal fistulas communicate with the concerned chamber via a sinusoidal network, as described in our patient.^{6 7} The large majority (>90%) of cameral fistulas drain into the right-sided cardiac chambers.⁸

Patients presenting with a CAF exhibit symptoms dependent on the degree of shunting from coronary steal.⁹ Few patients may present with fatigue, dyspnoea, ischaemia, arrhythmias and endocarditis, whereas those with severe shunting may have additional complications including pulmonary hypertension, myocardial ischaemia and infarction, congestive heart failure.^10–12 Fistula are known to enlarge with age and rupture has been uncommonly described.^{13 14} Atrial fibrillation may be the presenting symptom if the fistula ends in the right atrium, causing volume overloading.¹⁵ Sudden cardiac death has also been reported.¹³

Of particular interest is the concept of how coronary steal syndrome can be brought about by the presence of a CAF. Considering the formula for vascular resistance, we observe that the resistance within a vessel is inversely proportional to the radius to the fourth power.¹⁶ Thus, the larger the fistula (and therefore the radius), the lower the resistance. Furthermore, the pressure gradient is steeper in fistulas connecting coronary arteries to the venous circulation as opposed to fistulas occurring between coronary arteries in isolation.¹⁷ If we consider Poiseuille’s law, the flow through a vessel is directly proportional to the pressure gradient and inversely proportional to the resistance.¹⁸ Thus, with a high pressure gradient (LAD-to-LAA connection) and decreased resistance (large fistula and thus large radius), there is more flow through the fistula than the coronary artery, resulting in a coronary steal syndrome wherein flow through the coronaries is limited.

Definitive management of CAFs can occur either via the transcatheter route or surgically.^{14 19–21} The mainstay of treatment is to prevent complications resulting from volume overload of the cardiac chambers resulting in congestive heart failure, atrial fibrillation and ventricular arrhythmias, coronary complications resulting in myocardial ischaemia/infarction through coronary steal, valvular complications and infective endocarditis.^22–29 Extracardiac complications include hemopericardium, from rupture of an associated aneurysm as well as pulmonary hypertension.^{22 24 30}

In the absence of guidelines, there is no consensus on therapeutic strategies regarding management of CAFs. Spontaneous closure of CAFs has been reported while haemodynamically significant ones require intervention.^31–33 A retrospective study completed in 2015 followed 122 individuals with CAFs from 1996 to 2011 and saw 90 patients remain asymptomatic, with spontaneous closure noted in 29%.³⁴

Coil embolisation using a wide range of occlusion devices, umbrella devices, detachable balloons, vascular plugs and covered stents have been used with success.^{20 35–37} Major contraindications to coil embolisation include large fistula, fistula with multiple communications, distal fistula and risk to an adjacent vessel.³⁸ Surgical closure of CAFs remain the most effective therapy to date.¹⁴ Results from both approaches indicate good short-term and long-term prognosis. In the series by Cheung et al., 97% of patients remained asymptomatic during a follow-up period of 9 years with a 10% fistula recurrence rate.³⁹ Valente et al reported a complication rate of 15% in their series, including myocardial infarction, thrombotic coronary occlusion, cardiomyopathy, and residual fistula.⁴⁰

Dual CAFs are an uncommon cause of chest pain syndrome and a clinical curiosity, that may provoke ischaemia through a coronary steal syndrome. The rationale to obliterate these either surgically or via coil embolisation should be based on the objective evidence of ischaemia by non-invasive testing. The temptation to obliterate them just because they are abnormal vessels should be resisted, akin to the ‘stenotic reflex’ in coronary artery stenting.

Learning points.

• Coronary artery fistulas (CAFs), acting as shunts, can cause ischaemia through coronary steal syndrome.

• Management of CAFs is guided by symptoms provoked by coronary steal and shunt haemodynamics, as well as preventing complications.

• Surgical obliteration of CAFs is the most effective therapy.

• Coil embolisation of CAFs via the transcatheter route is a promising percutaneous technique with comparable results to surgical closure.

• Complications of haemodynamically significant CAFs include sudden death, myocardial infarction, heart failure, atrial fibrillation, ventricular arrhythmias and infective endocarditis.