Sterno-bronchial fistula – an extremely rare complication after coronary artery bypass grafting

Introduction

Although the epicardial pacing wires are considered the standard in the diagnosis and treatment of dysrrhythmias following cardiac surgery, it’s implementation is not independent from the potentially serious complications [1, 2]. We present a case of post – coronary artery bypass grafting (CABG) peristernal wound infection complicated by mediastinal fistula communicating with the right bronchial tree, which might be due to the retention of temporary epicardial pacing wires.

Case report

A 53-year-old male was referred to our Department in April 2008 due to evolving symptoms of unstable angina. His diagnosis of quadruple – vessel coronary artery disease, hyperlipidemia and arterial hypertension was confirmed and a surgical treatment plan was settled. His medical history revealed an anterior wall myocardial infarction two years before the admission. Neither obesity nor features of diabetes mellitus were found. The left ventricular function was preserved (LVEF 55%) and the Logistic EuroSCORE was 3.1%. Due to the patient’s condition an emergency on – pump CABG was performed. One arterial [left internal thoracic artery (LITA) to left anterior descending (LAD)] and three venous [saphenous vein graft (SVG) to IM, right coronary artery (RCA) and OM) aorto-coronary bypasses were implanted. The atrial and ventricular temporary epicardial pacing wires were placed due to bradycardia and unsatisfactory cardiac output. The sternum was closed with the aid of six metallic sutures – five simple wires and one figure-of-eight. The early postoperative course was complicated by low cardiac output syndrome which required continuous infusions of inotropic agents, antidysrrhythmics and institution of intra-aortic balloon pumping (IABP). Over the period of five days, the patient’s condition stabilized allowing us to discharge him on the ninth postoperative day.

On the discharge sternum was stabile and the wound completely healed. His follow-up visit took place eight weeks later. The patient’s condition was unremarkable and post sternotomy wound did not display any signs of infection.

One month later, the patient was admitted to the general surgery ward after he had been diagnosed with soft tissue abscess in the lower aspect of the wound. The patient presented with the subscapular back pain and concomitant fever up to 39°C.

Within the period of twelve months, the patient was hospitalized several times due to peristernal pain, fever, and suspicion of pneumonia. Along this period, multiple, recurrent skin abscesses with several fistulas at the lower part of the sternum were observed. The patient was treated with three courses of antibiotics, given both orally and parenterally. None of this gave durable effect. A year after the initial procedure the patient was readmitted to our unit. The responsible pathogen was identified as methicillin sensitive Staphylococcus aureus (MSSA). Under general anesthesia two metallic sutures were removed from the lower sternum, and the surgical debridement was performed. Infection was treated according to the antibiogram. Soon after, a resolution of the inflammation was observed.

One month after, a follow-up CT revealed a pacing wire situated correctly on the right atrium wall and purulent discharge with CT – visible gaseous bubbles forming a right peristernal abscess. Several days later, a new onset of skin fistula at the upper part of the sternum was encountered.

During the routine abscess cavern irrigation with an antiseptic fluid, the patient had a cough salvo and expecto­rated. Suspicion of the bronchial tree fistula was made at this point. Although gastrofiberoscopy, bronchoscopy and CT were performed no confirmation was obtained. On the classic fistulography, after the water soluble contrast medium was injected to the skin fistula at the lower aspect of the sternum, the contrast medium filled not only the lower peristernal area but also the right bronchial tree (Fig. 1). In the projection of purulent canal communicating the skin with the bronchial tree, the shadow of the atrial epicardial pacing wire could be observed (Fig. 2). On the same day all epicardial wires were explanted under the local anestesia. With the help of CT scans the tips of electrodes were explored beneath the xiphoid process and retracted. A follow-up diagnostics revealed complete resolution of the infection and inflammation. To the present day, the patient remains asymptomatic.

Discussion

Mandak et al. were the first to report the case of a ster­no – bronchial fistula due to sternal wound infection [1]. Sakellaridis T. and colleagues presented the second case [2]. To our best knowledge the above case is the third.

Patophysiology of the sterno-bronchial fistula remains unclear. No data are available to support the thesis that the epicardial wires and/or metallic sternal sutures are responsible for the formation of the fistula. We find it peculiar, that the infectious process can migrate from the pericardial sac to the bronchial tree without disseminating to the pleural cavity. It is also surprising that in all three cases MSSA was cultured, and named an etiologic factor of the entity. Above that we argue with the functioning name of the entity which suggests that the sternum is involved in the inflammatory process. Surprisingly in all three cases the peristernal tissue was involved, but the sternal bone remained untouched.

All epicardial pacing wires were explanted under the local anesthesia, as we feared that residual communication between the bronchial tree and the pericardial sac may cause a pneumopericardium with the symptoms of the acute tamponade during the positive pressure ventilation. To our content this simple procedure produced the awaited outcome with no further complications.

In contrast to previous reports, our patient was managed be open explantation of pacing wires whereas in the other cases this was not performed due to lack of the patient consent in one case and the poor clinical status in the other. Previous reports did not specify the treatment results. The twelve – month long follow – up of our patient was longer than any in the remaining reports hence permanent resolution of the symptoms might be suggested.

Acknowledgements

The authors would like to thank Mrs. Agnieszka Albińska-Marczak for the editorial insights.



The Abstract was presented at the Thoracic Baltic Meeting 2010, 30th September – 2nd October 2010, Jurata, Poland.

References

1. Abu-Omar Y, Guerrieri-Wolf L, Taggart DP. Indications and positioning of temporary pacing wires. Interact Cardio Vasc Thorac Surg doi:10.1510/mmcts.2005.001248

2. Johnson LG, Brown OF, Alligood MR. Complications of epicardial pacing wire removal. J Cardiovasc Nurs 1993; 7: 32-40.

3. Mandák J, Lonský V, Sedlácek Z. Sternobronchial fistula – uncommon complication after Coronary Surgery (a case report). Acta Medica (Hradec Kralove) 2000; 43: 29-31.

4. Sakellaridis T, Argiriou M, Panagiotakopoulos V, Charitos Ch. Bilateral sternobronchial fistula after coronary surgery – are the retained epicardial pacing wires responsible? A case report. J Cardiothorac Surg 2009; 4: 26.