Coronary Fistula: Left Anterior Descending to Pulmonary Artery Fistula

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Pradnya Brijmohan Bhattad, MD^1,3; Joseph Hannan, MD^1,2

¹Interventional Cardiology, Lahey Clinic, Massachusetts; ²Interventional Cardiology, Saint Vincent Hospital, UMass Chan Medical School, Massachusetts; ³Internal Medicine, Brijmohan Bhattad Hospital, Maharashtra, India

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

Informed consent has been obtained from the patient for their anonymized information to be presented in this study.

The authors can be contacted via Pradnya Brijmohan Bhattad, MD, at pradnyabhattad20@gmail.com.

Coronary artery fistulas (CAF) are rare congenital or acquired vascular anomalies characterized by abnormal connections between the coronary vessels and other major vessels or the cardiac chambers. The exact incidence is unknown, but it is estimated that CAFs account for 0.3% of cardiac abnormalities.¹ 

CAFs can be coronary-cameral or coronary IV depending on the compartments connected by the fistula with the fistula connecting the coronary artery with the cardiac chambers or other systemic or pulmonary vessels, respectively.¹ Among the CAFs, the most common is a fistula between the left anterior descending (LAD) and right ventricle, with an estimated incidence of 41% of CAFs, while the least common is the LAD to pulmonary artery fistula with a prevalence of 17%.¹ The first case of the LAD to pulmonary artery fistula was described by Krause in 1865, with the first successful surgical treatment described in 1958.²

Coronary artery fistulas can be asymptomatic incidental findings or can present with ischemic symptoms and acute coronary syndrome (ACS), signs of fluid overload depending on the size and flow of the fistula, sudden cardiac death, and structural changes such as papillary muscle rupture, secondary valvular disease, and premature atherosclerosis.³ The proposed mechanism of ischemia is thought to be the development of coronary steal because of the abnormal fistula and shunting, as well as increased left ventricular oxygen demand due to increased volume load.² Another significant complication of a LAD to pulmonary trunk fistula is the possible development of pulmonary hypertension.⁴

The gold standard for evaluation of CAFs is via coronary angiography which not only provides a diagnosis but also offers anatomic details that contribute to decision-making regarding management. In addition, transthoracic or transesophageal echocardiography can provide collateral information in the analysis of the anatomy of CAF, as well as its effect on cardiac function. An alternative modality for evaluation is coronary computed tomography (CT) angiography, although this comes with radiation exposure. Cardiac magnetic resonance imaging is also an option but generally has limited availability compared to the other modalities, as well as decreased resolution.¹

Our case describes an incidental finding of a fistula between the septal branch of the LAD and the pulmonary trunk (Figure 1; Videos 1-6).

Management of coronary artery fistulas should ideally involve a multidisciplinary discussion between the cardiologist, interventional cardiologist, cardiothoracic surgeon, and vascular surgeon, as multimodal therapy might be needed. Specific management of fistulas is not always indicated, especially when they are asymptomatic, incidental findings. Management is indicated mainly in symptomatic cases and fistulas associated with severe coronary artery disease. The American College of Cardiology and the American Heart Association also recommend surgical closure for large-volume fistulas.¹ Medical management with antianginal agents can also be considered in patients with low-flow fistulas without significant shunting.¹ 

Although there is no standardized guideline-directed therapy regarding timing and choice of intervention for coronary fistulas due to their rarity, cases have been managed by transcatheter coil embolization or surgical intervention via ligation. The choice of surgery or transcatheter intervention generally depends on factors such as the morphology of the fistula, including the location and size of the ostia, as well as the patient’s general condition and functional status. It should be noted that lesions repaired via transcatheter approach run a risk of recanalization, as shown in a study at Mayo Clinic⁵; therefore, follow-up invasive angiography is recommended. With the data available, surgery with or without cardiopulmonary bypass is currently described as the gold standard.² More room remains for an in-depth study of coronary artery fistulas for more standardized risk stratification and management.

References

1.     George V, Omerovic S, Madala M, Kang A. Left anterior descending artery to pulmonary artery fistula: a case report. Cureus. 2022 Jul 10; 14(7): e26713. doi:10.7759/cureus.26713

2.     Kunt AS. Coronary artery and pulmonary artery fistula originated from significant stenosis in the left anterior descending artery. Case Rep Emerg Med. 2013; 2013: 298156. doi:10.1155/2013/298156

3.     Gelman S, Benin A, Savoj J, et al. A fistula where? Left anterior descending to pulmonary artery fistula. J Med Cases. 2020 Oct; 11(10): 306-308. doi:10.14740/jmc3527

4.     Schizas N, Patris V, Giannaraki S, et al. Reversible pulmonary hypertension due to combined fistula between the left anterior descending artery (LAD) and pulmonary artery and severe stenosis of the LAD. Case Rep Cardiol. 2021 Mar 4; 2021:6629684. doi:10.1155/2021/6629684 

5.     Ibrahim MF, Sayed S, Elasfar A, et al. Coronary fistula between the left anterior descending coronary artery and the pulmonary artery: Two case reports. J Saudi Heart Assoc. 2012 Oct; 24(4): 253-256. doi:10.1016/j.jsha.2012.07.004

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