A complex coronary arteriovenous fistula

Xiaoyong Zhang, RT1; Wuchao Li, MD1; Xianchun Zeng, MD1; Rongpin Wang, MD1; Pengyun Cheng, MD2; Xinglong Liu, MD2

1 Department of Radiology, Guizhou Provincial People’s Hospital, Guizhou, P. R. China

2 Siemens Healthineers, China

A 75-year-old male patient, a known long-term smoker, was hospitalized due to an acute cerebral infarction. He was complaining of chest discomfort and his blood pressure was 190/110mm Hg. An echocardiography examination was performed, revealing no abnormalities. A coronary CTA (cCTA) was requested for further evaluation.

CT images showed a right coronary artery (RCA) dominant system. The left main coronary artery (LM) was moderately dilated. Its branches, the left anterior descending artery (LAD) and the circumflex artery (Cx), showed normal calibers and courses. The LM extended tortuously as an anomalous fistula with multiple aneurysmal changes, passing in front of the main pulmonary artery (MPA) and then joining the ascending aorta (AA) near the origin of the RCA. Four other fistulas originated therefrom – the first, with a clear “jet sign”, drained into the MPA suggesting a left to right shunt; the second, coursing in between the MPA and the ascending aorta (AA), as well as the innominate artery (IA) and the left common carotid artery (LCCA), drained into the root of the IA posteriorly; the third, passing along the anterior aspect of the MPA and the aortic arch, connecting posteriorly with the proximal left subclavian artery (LSA) with a bulbous change at the entrance and finally the fourth, going behind the MPA and draining into a dilated bronchial artery (BA) arising from the descending aorta (DA). Two small fistulas from the distal RCA were also seen draining into the middle cardiac vein (MCV). There were no other accompanying anomalies present and the diameter of the MPA was normal. CT findings suggested a complex coronary arteriovenous fistula (CAF), Sakakibara type A. The patient was not recommended for immediate intervention but for follow ups, considering his age, mild cardiac symptoms, and no other structural and functional abnormalities.

An axial image shows a fistula draining into the MPA with a clear “jet sign”. A MIP image shows a dilated LM extending into a tortuous anomalous fistula.

Courtesy of Department of Radiology, Guizhou Provincial People’s Hospital, Guizhou, P. R. China

Fig. 1: An axial (Fig. 1a) image shows a fistula draining into the MPA with a clear “jet sign” (arrow). A MIP image (Fig. 1b) shows a dilated LM extending into a tortuous anomalous fistula.

cVRT images show an anomalous fistula with multiple aneurysmal changes, passing in front of the MPA and joining the AA near the origin of the RCA. The LAD and the Cx are branched out, with normal calibers and courses. Two small fistulas from the distal RCA are seen draining into the MCV.

Courtesy of Department of Radiology, Guizhou Provincial People’s Hospital, Guizhou, P. R. China

Fig. 2: cVRT images show an anomalous fistula with multiple aneurysmal changes, passing in front of the MPA and joining the AA near the origin of the RCA (Fig. 2a, arrow). The LAD and the Cx are branched out, with normal calibers and courses. Two small fistulas from the distal RCA are seen draining into the MCV (Fig. 2b, arrows).

cVRT images show three fistulas – two coursing anteriorly and one posteriorly – draining into the root of the IA, the proximal LSA with a bulbous change at the entrance and a dilated BA arising from the DA.

Courtesy of Department of Radiology, Guizhou Provincial People’s Hospital, Guizhou, P. R. China

Fig. 3: cVRT images show three fistulas – two coursing anteriorly and one posteriorly – draining into the root of the IA (white arrows), the proximal LSA with a bulbous change at the entrance (orange arrows) and a dilated BA arising from the DA (white dotted arrow).

A complex CAF involves entangled blood vessels with multiple fistulous structures with which coronary arteries drain into any segment of the pulmonary or systemic circulation. Occasionally, it may have multiple origins and drainage sites with complex communications, such as this case, making the diagnosis very challenging. Coronary CTA with cinematic volume rendering technique (cVRT) allows for excellent visualization of anatomic details of multiple fistulous tracts to various thoracic vessels. In this case, the multiple fistulas draining into the AA, IA, LSA, BA and MCV are clearly identified. The other challenge is that the patient could not comply with breathing instructions due to his critical situation. Therefore, an ultrafast scanning technique – Turbo Flash mode – is applied to acquire a scan range of 29.5 cm in just 0.4 seconds at free breathing. This also facilitates the reduction of radiation exposure and the amount of contrast agent needed. Although CAFs are usually asymptomatic, they can alter coronary hemodynamic parameters causing serious complications, including heart failure and myocardial infarction, making surgical ligation or percutaneous transcatheter closure necessary. In such cases, it is crucial to have pre-procedural knowledge concerning the characteristics of the CAFs, with cCTA playing an important role.

Scanner

Scan area

Thorax

Scan mode

Turbo Flash mode

Scan length

295 mm

Scan direction

Cranio-caudal

Scan time

0.4 s

Tube voltage

70 kV

Effective mAs

240 mAs

Dose modulation

CARE Dose4D

CTDIvol

0.67 mGy

DLP

22.4 mGy*cm

Rotation time

0.25 s

Pitch

3.2

Slice collimation

192 x 0.6 mm

Slice width

1.0 mm

Reconstruction increment

0.7 mm

Reconstruction kernel

Bv40, ADMIRE 3

Heart rate

96 bpm

Contrast

370 mg/mL

Volume

40 mL + 40 mL saline

Flow rate

4 mL/s

Start delay

Bolus tracking triggered at 100 HU in the ascending aorta + 4 s