Asymptomatic Aorto-Atrial Fistula Secondary to Surgical Repair of Ascending Aortic Dissection: When to Do Nothing.

Secondary aorto-atrial fistula is a rare but potentially life-threatening complication of ascending aortic dissection surgical repair. Secondary aorto-atrial fistulas commonly lead to symptomatic heart failure requiring emergent repair. We present a rare case of secondary aorto-atrial fistula after surgical repair of aortic dissection that remained asymptomatic for a decade. (Level of Difficulty: Intermediate.).

Acute type A aortic dissection (ATAD) is a life-threatening emergency with an incidence in Western countries of 40 to 70 cases per 1,000,000 residents and a mortality risk of ≤60%. The optimal surgical intervention on the aortic root (AR) is debatable and includes AR reconstruction and replacement. We present a patient who underwent AR reconstruction and experienced an aorto-atrial fistula (AAF).

Case Presentation

A 71-year-old man presented in our outpatient clinic for follow-up care. Ten years earlier, he presented with chest pain, facial cyanosis, and upper extremity pulse discrepancies. Physical examination demonstrated a blood pressure of 108/70 mm Hg, heart rate of 62 beats/min, respiratory rate of 18 breaths/min, and no murmur. He received a diagnosis of ATAD and underwent emergent hemiarch replacement, reconstruction of the aortic root with aortic valve resuspension, and relamination of dissected planes. Intraoperative hemodynamics demonstrated central venous pressure 14 cm H2O, pulmonary artery pressure 21/15 mm Hg, and pulmonary capillary wedge pressure 12 mm Hg.

A postoperative transesophageal echocardiogram and CT angiogram revealed an aortic root pseudoaneurysm with flow entering at the noncoronary aortic sinus and exiting through a fistula into the left atrium (LA) (Video 1). Conservative management of the aorto-atrial fistula (AAF) was chosen, given the complexity of his initial operation and development of renal failure. Over the past 10 years his condition has remained stable, without the development of any heart failure symptoms. However, recent physical examinations have noted a left sternal border systolic murmur. Follow-up echocardiograms demonstrated no change in left ventricular (LV) function and stability of the AAF (Figure 1). However, his left atrial size has increased, and his tricuspid valve regurgitation has slightly worsened (Tables 1 and 2).

Figure 1

Computed Tomography Angiogram and Echocardiogram Findings of Aortic Root Pseudoaneurysm and Aorto-Left Atrial Fistula

(A) Follow-up computed tomography angiogram demonstrating an aorto-atrial fistula (white arrow) at the noncoronary sinus entering an aortic root pseudoaneurysm and then into the left atrium (LA). (B) Follow-up computed tomography angiogram demonstrating the aorto-atrial fistula (white arrow) in relation to the noncoronary sinus and left coronary sinus entering an aortic root pseudoaneurysm and then into the LA, also demonstrating a chronic ascending aortic dissection (orange arrow). (C) 3-dimensional volume rendered computed tomography image demonstrating an aorto-atrial fistula (white arrow) with an enlarged LA. (D) Follow-up transesophageal echocardiogram demonstrating an aortic root pseudoaneurysm (orange arrow) with flow entering at the noncoronary sinus and exiting through a fistula (white arrow) into the LA. AO = aorta; LA = left atrium; LV = left ventricle.

Table 1

Comparison of Echocardiogram Measurements at Diagnosis of Aorto-Left Atrial Fistula and 10 Years Later

Initial Echocardiogram at Diagnosis		Follow-Up Echocardiogram 10 Years After Diagnosis
Characteristic	Measurement	Characteristic	Measurement
Interventricular septal end diastole	0.96 cm	Interventricular septal end diastole	1.31 cm
Left atrium diameter	3.79 cm	Left atrium diameter	6.5 cm
Aortic root diameter	4.1 cm	Aortic root diameter	4.1 cm
Left ventricular internal diameter end-diastole	5.65 cm	Left ventricular internal diameter end-diastole	6.7 cm
Left ventricular posterior wall dimensions	1.12 cm	Left ventricular posterior wall dimensions	1.31 cm
Right ventricular systolic pressure	35.1 mm Hg	Right ventricular systolic pressure	52.5 mm Hg
Ejection fraction	50%-55%	Ejection fraction	50%-55%

Table 2

Comparison of Valvular Functions at Diagnosis of Aorto-Left Atrial Fistula and 10 Years Later

Initial Echocardiogram at Diagnosis		Follow-Up Echocardiogram 10 Years After Diagnosis
Valve	Function	Valve	Function
Aortic valve	Trileaflet and normal appearing with mild regurgitation	Aortic valve	Trileaflet and normal appearing with mild stenosis and regurgitation
Mitral valve	Normal appearing with mild regurgitation	Mitral valve	Normal appearing with mild to moderate regurgitation
Tricuspid valve	Normal appearing with trace regurgitation	Tricuspid valve	Normal appearing with mild regurgitation
Pulmonic valve	Normal appearing with trace regurgitation	Pulmonic valve	Normal appearing with trace regurgitation

Discussion

Secondary AAF should be acknowledged as a serious complication of ATAD repair. Without prompt diagnosis, symptomatic secondary AAF has a mortality rate >40%. However, in the absence of symptoms, the management of AAF can vary.

Anatomically, the right atrium contacts a greater portion of the ascending aorta and is thus more predisposed to secondary AAF., Our case is unique in that the AAF involved the LA and noncoronary aortic sinus, which is rare., This case also demonstrates an atypical clinical course of secondary AAF. Most patients with secondary AAF present with heart failure symptoms shortly after the condition develops and require emergent repair. Invasive treatment options for AAF include surgical and percutaneous closure, both demonstrating similar outcomes. Interestingly, our patient remained asymptomatic for 10 years. Given the rare presentation, we question whether the aortic root pseudoaneurysm contributed to the atypical clinical progression of this AAF.

Although our patient remained asymptomatic, he has demonstrated increasing LV dimensions and PA pressures as well as worsening mitral regurgitation (Tables 1 and 2). Therefore, great caution must be placed on close monitoring of asymptomatic AAF for volume overload caused by worsening LV function and mitral valve insufficiency. Prompt referral for percutaneous or surgical closure is necessary at symptom onset, echocardiographic evidence of shunt progression, or decreasing ventricular function.

Funding Support and Author Disclosures

The authors have reported that they have no relationships relevant to the contents of this paper to disclose.