Asymptomatic Coronary to Left Ventricle Fistula with Coronary Artery Ectasia Managed Conservatively: A Case Report

Coronary artery fistula (CAF) is a rare congenital or acquired anomaly characterised by an abnormal connection between a coronary artery and a cardiac chamber or great vessel. It is observed in approximately 0.002% of the general population and accounts for approximately 0.4% of all congenital cardiac malformations.¹ With the widespread use and advances in noninvasive cardiac imaging modalities, such as coronary CT angiography (CTA), an increasing number of asymptomatic CAFs are now being detected incidentally. As a result, the clinical management of incidentally discovered, asymptomatic CAFs has become an emerging topic of interest.

CAF may be associated with aneurysmal coronary artery disease, including coronary artery aneurysm and coronary artery ectasia (CAE). Surgical or transcatheter interventions have been shown to be effective in symptomatic cases; however, the optimal management strategy for asymptomatic patients, particularly those with CAF and CAE, remains controversial and subject to ongoing debate.^2,3

In this article, we present a rare case of an asymptomatic right coronary artery (RCA)–left ventricular (LV) fistula with diffuse ectasia of the RCA, and we discuss a conservative treatment approach in the absence of ischaemia, symptoms or significant haemodynamic compromise. Our case may help inform decision-making for similarly asymptomatic patients with CAF and aneurysmal coronary artery disease.

Case Presentation

A 52-year-old Cambodian man with a medical history of hypertension, dyslipidaemia and diabetes was referred to our outpatient clinic for a routine health check-up. He had no prior history of cardiovascular disease and was taking valsartan as his only regular medication. He was entirely asymptomatic, with normal vital signs and no abnormal findings on cardiovascular or respiratory examination.

A 12-lead ECG showed non-specific flat T waves in both limb and precordial leads. Chest radiography demonstrated mild cardiomegaly, with a cardiothoracic ratio of 50%. Lipid profile showed LDL cholesterol of 155 mg/dl, HDL cholesterol of 46 mg/dl and triglycerides of 64 mg/dl, and HbA_1c was 6.6%. Given his cardiovascular risk factors and these initial findings, transthoracic echocardiography (TTE) and a treadmill exercise test were performed. Initial TTE revealed an enlarged RCA at its origin (Figure 1A). Colour Doppler imaging demonstrated abnormal diastolic flow entering the LV (Figure 1B), with pulsed-wave Doppler confirming prominent flow during late diastole (Figure 1C), raising suspicion of an abnormal intracardiac shunt. LV systolic function was preserved (ejection fraction 62% by Simpson’s biplane method), but global longitudinal strain (GLS) was mildly reduced to −13.4%, suggesting subtle myocardial dysfunction (Figure 1D).

Although the treadmill test yielded negative results, the suspicion of an intracardiac shunt and possible coronary artery anomaly based on TTE findings prompted further evaluation with coronary CTA. Subsequent coronary CTA revealed a fistulous connection from the RCA to the LV, with associated diffuse ectasia (maximal diameter 30 mm) and a 5-mm terminal orifice (Figures 2A and B). No thrombus formation was observed. Furthermore, a 70% stenosis was noted in segment 7 of the left anterior descending artery (LAD; Figure 2C). Despite these findings, the patient remained completely asymptomatic.

To determine an appropriate treatment strategy, further evaluation was performed. Autoimmune screening, including antinuclear antibody and antineutrophil cytoplasmic antibody panels, was negative. B-type natriuretic peptide was mildly elevated at 50 pg/ml, while high-sensitivity cardiac troponin I was negative. To assess the haemodynamic significance of the fistula, the pulmonary:systemic flow ratio (Qp/Qs) was measured via TTE and calculated to be 1.03, suggesting a haemodynamically insignificant shunt.

After multidisciplinary discussion and shared decision-making with the patient, we opted for conservative management without invasive treatment for the coronary ectasia and fistula (Figures 3A and 3B), which provides 3D visualisations illustrating diffuse RCA ectasia and the fistulous drainage into the LV. As part of the conservative management strategy, aspirin was initiated to address the LAD stenosis. Given the absence of intracoronary thrombus, prophylactic anticoagulation was withheld. In addition, antihypertensive and lipid-lowering therapies were intensified to optimise cardiovascular risk reduction.

The patient is currently in the early follow-up period (3 months to date) and remains asymptomatic, with no evidence of angina, heart failure or arrhythmias. The patient is being followed in the outpatient clinic with periodic imaging studies, including coronary CTA and TTE, as well as laboratory monitoring of B-type natriuretic peptide and high-sensitivity troponin I. During the first year, follow-up is planned every 3–6 months with repeat coronary CTA and echocardiography to monitor fistula morphology, ectasia diameter, and ventricular function. Functional testing, such as treadmill stress testing, will be performed when clinically indicated.

Discussion

CAFs represent rare vascular anomalies involving anomalous communication between the coronary circulation and cardiac chambers or major vessels. While most CAFs drain into the right heart or pulmonary circulation, drainage into the LV is exceedingly uncommon, accounting for <3% of all reported cases.⁴

When accompanied by CAE, the pathophysiology may resemble that of aortic regurgitation, with diastolic runoff into the low-resistance LV chamber, potentially resulting in volume overload and myocardial ischaemia over time.

Most previously reported cases of CAF associated with aneurysmal coronary artery disease have involved symptomatic patients and were treated either surgically or with transcatheter closure.^2,3 For example, Zhang et al. described RCA–LV fistula with giant RCA of diffuse ectasia that required the repair of the RCA–LV fistula, and the resection and reconstruction with coronary artery bypass grafting.⁵ Conversely, there are also reports of surgical intervention in asymptomatic patients; however, these cases typically involved giant coronary aneurysms with high risk of rupture, such as markedly dilated lesions >50 mm in diameter.^6,7

In contrast, the management strategy for asymptomatic patients with RCA ectasia and fistulous drainage into the LV remains poorly defined, as most treatment algorithms are guided by symptom burden or aneurysmal risk. Moreover, few studies have evaluated the haemodynamic impact of CAFs draining into the LV. Most available literature focuses on shunt physiology involving right-sided cardiac chambers or the venous system, with virtually no data specifically addressing RCA–LV fistulas.⁸

Although the use of Qp/Qs measurement is not routinely used in the evaluation of coronary–LV fistula, we hypothesised that it could provide insight into the haemodynamic significance of the shunt. In cases of large-volume coronary–LV fistula, a diastolic runoff into the LV may mimic the physiology of aortic regurgitation and potentially result in Qp/Qs values <1.0. In our case, the Qp/Qs was 1.03, supporting the absence of significant shunting. However, we acknowledge that Qp/Qs estimation in coronary–LV fistulas is not a validated or guideline-recommended method, and in this case, it was used only as an exploratory haemodynamic indicator rather than a definitive assessment of shunt severity. Additionally, the patient’s echocardiographic parameters, including preserved ejection fraction, a mildly reduced GLS and normal LV dimensions, suggested that LV volume overload was minimal.

The mildly reduced GLS observed in this patient may be related to the 70% stenosis in the mid-LAD segment, despite the absence of overt ischaemic symptoms or treadmill-induced changes. GLS reduction is known to be an early marker of subclinical myocardial dysfunction, and in this case, it may reflect subtle ischaemia in the LAD territory. The paradoxically increased strain in one basal RCA segment was interpreted as an artefact related to the fistulous entry site rather than true regional dysfunction.

Regarding the risk of coronary aneurysm, saccular coronary aneurysms are generally considered to carry a higher risk of rupture due to their focal wall stress and structural fragility.⁹ In contrast, the risk of rupture in CAE remains unclear. To date, there is limited evidence supporting a significant rupture risk associated with CAE, particularly in the absence of rapid expansion or thrombus formation.

Taken together, the absence of symptoms, minimal haemodynamic burden (Qp/Qs = 1.03), lack of intracoronary thrombus and the ectatic (rather than saccular) morphology of the coronary artery all supported a conservative management strategy in this case. Regarding follow-up, given the uncertainty surrounding the long-term natural history of RCA–LV fistulas with ectasia, structured imaging follow-up is essential. In our patient, surveillance with coronary CTA and TTE is planned every 3–6 months during the first year to monitor fistula morphology, ectasia progression and potential thrombus formation.

This report has several limitations. First, due to regional resource constraints, advanced imaging modalities, such as cardiac MRI and myocardial perfusion scintigraphy, were not available, which may have provided more detailed assessment of myocardial ischaemia and haemodynamic impact. Second, the role of treadmill testing in evaluating coronary steal phenomenon in patients with RCA–LV fistula remains unclear and may not fully exclude subtle ischaemia. Finally, the long-term observation will be essential to assess the progression of coronary ectasia and the potential development of symptoms or complications.

Conclusion

The management of asymptomatic coronary artery fistula with associated ectasia remains a clinical challenge due to the rarity of the condition and the lack of established guidelines. This case highlights the importance of individualised decision-making based on comprehensive anatomical, functional and haemodynamic assessment. Our findings suggest that conservative treatment may be a reasonable option in selected asymptomatic patients without evidence of ischaemia, significant shunting or ventricular dysfunction. However, given the potential for long-term complications, close clinical surveillance and further accumulation of similar cases are warranted to inform future management strategies.