Aorto–Right Atrial Fistula: A Rare Complication of Aortic Dissection

Abstract

We describe the successful surgical repair of an acute aortic dissection that had caused an aorto–right atrial fistula in a 67-year-old man. The patient was admitted to the hospital on an emergency basis because of severe heart failure. The diagnosis of acute aortic dissection with rupture into the right atrium was confirmed by use of intraoperative transesophageal echocardiography, although rupture of a sinus of Valsalva aneurysm into the right atrium had been suggested initially by 2-dimensional and Doppler transthoracic echocardiography.

At surgery, we found the patient to have aortic arch dissection with complete separation of the right coronary artery from the sinus of Valsalva and a false lumen that had ruptured into the right atrium. The aortic arch was repaired directly. The ascending aorta was successfully replaced with a composite graft.

Aortic dissection with rupture into the right atrium is extremely rare and leads to death rapidly. As shown in this case, such a condition might be mistaken for an aneurysmal rupture of the sinus of Valsalva, with use of transthoracic echocardiography alone. Transesophageal echocardiography is a useful noninvasive method to further define or confirm the diagnosis. Early surgical intervention is necessary in patients with this condition to prevent profound shock and end-organ failure.

Aortic dissection generally results in aortic rupture into the pleural and pericardial spaces, often resulting in sudden cardiovascular collapse and death. Rupture into the right atrium is an extremely rare condition that is also rapidly fatal. ¹ A few cases of successful repair of this condition have been reported. ^2–7 We describe a patient who underwent successful surgical repair of an aortic dissection that had caused an aorto–right atrial fistula.

Case Report

In March 1999, a 67-year-old man was brought to the emergency room because of dyspnea and oliguria. He had a history of systemic hypertension and chronic atrial fibrillation. He had been well until 3 months earlier, when he had begun experiencing exertional dyspnea and dull chest pain. Subsequently, orthopnea, oliguria, and cold sweating developed.

Physical examination revealed agonizing respiration and signs of congestive heart failure, with pulmonary rales and elevated jugular venous pressure. The skin was cold and clammy. A grade 2/6 continuous murmur was heard over the right sternal border. The electrocardiogram showed atrial fibrillation with a rapid ventricular rate. Chest radiography showed cardiomegaly and pulmonary congestion. Liver and renal function were impaired. Two-dimensional transthoracic echocardiography revealed an enlarged right atrium and right ventricle with moderate-to-severe tricuspid regurgitation. The ascending aorta was slightly dilated, with an area of echogenic density near the aortic valve and moderate-to-severe aortic regurgitation. Doppler echocardiography revealed a high-velocity continuous signal consistent with a fistula from the aortic root to the right atrium (Fig. 1). Pulmonary artery catheterization confirmed a large left-to-right shunt with a Qp/Qs flow ratio of 3.75. Infective endocarditis of the aortic valve and a ruptured aneurysm of the sinus of Valsalva into the right atrium were diagnosed, and the patient was taken to the operating room immediately because of intractable heart failure.

Fig. 1 Transthoracic echocardiography: A) 2-dimensional parasternal short-axis view showing the fistula between the aortic root and the right atrium, and B) pulsed Doppler study showing continuous flow through the fistula.

A = Aorto–right atrial fistula; LA = left atrium; RA = right atrium; RVOT = right ventricular outflow tract; AA = aortic aneurysm

Before the skin incision, intraoperative transesophageal echocardiography disclosed an intimal flap—previously interpreted on transthoracic echocardiography as echogenic density near the aortic valve—that extended from the ascending aorta to the distal arch. Aortic dissection with a false lumen that had ruptured into the right atrium was confirmed, and surgery was initiated to repair the dissection and fistula.

Cardiopulmonary bypass was established with cannulation of the femoral artery and each vena cava. Under deep hypothermic circulatory arrest and on retrograde selective cerebral perfusion, the patient was found to have an aortic dissection that originated from a large intimal tear over the aortic arch and progressed in a retrograde direction to the aortic root. The right coronary artery was completely separated from the sinus of Valsalva, leaving only a patent ostial stump (Fig. 2). With use of the modified Bentall operation, the ascending aorta was resected and replaced with a composite graft, and the coronary arteries were reimplanted with button construction. Because of the disrupted right coronary artery and the possibility of tension if the right coronary artery was directly implanted, 1 saphenous vein graft was interposed for a right coronary artery anastomosis. The aorto–right atrial fistula was over the interatrial septum, but because of tissue fragility, it was quite difficult to define the location of the fistula through the aortic side. Therefore, we made a right atriotomy and repaired the fistula with 2 interrupted 4-0 pledgetted Prolene sutures.

Fig. 2 Drawing shows the aortic dissection found at operation.

A = intimal tear over aortic arch; B = right coronary artery disruption; C = aorto–right atrial fistula; FL = false lumen; RA = right atrium; TL = true lumen

On the day following surgery, the patient underwent re-exploration for a mediastinal hematoma. His postoperative course was complicated by transient hepatic and renal dysfunction. He convalesced gradually and was discharged 1 month postoperatively. Repeat echocardiography showed good ventricular function and no recurrence of the fistula. At the patient's follow-up visit at the outpatient clinic, 1 year after surgery, he remained well.

Discussion

Aortic dissection may obtrude into the right atrium, right ventricle, or pulmonary artery, ⁸ producing a left-to-right shunt and congestive heart failure. Kuipers and Schatz ¹ 1st reported the rupture of a chronic aortic dissection into the right atrium in 1963. During the next few years, this diagnosis was generally made only at postmortem. The 1st report of the successful surgical repair of an aortic dissection and aorto–right atrial fistula was published by Temple and colleagues ² in 1966. Clinicians for some time usually established the diagnosis through a combination of physical examination, cardiac catheterization, ^2,3,7 echocardiography, ^4,5 and magnetic resonance imaging. ⁶ Recently, 2-dimensional and pulsed Doppler echocardiography have enabled both the diagnosis and the precise localization of the communication between the dissecting aneurysm and the right atrium. ^4,5 However, the less accurate diagnosis of a rupture of a sinus of Valsalva aneurysm is still possible with these methods if the intimal flap is not identified. In this case, our patient developed an aorto–right atrial fistula, which was diagnosed preoperatively as infective endocarditis of the aortic valve and the rupture of a sinus of Valsalva aneurysm into the right atrium. Intraoperative transesophageal echocardiography served as another useful noninvasive method to better define the ascending aorta and thus to enable confirmation of the diagnosis.

Aortic dissection with aorto–right atrial fistula usually originates from an intimal tear near the aortic root (because of its proximity to the right atrium). More than one third of the reported cases involve patients who have undergone prior cardiac surgery. In such patients, the dense pericardial adhesions resulting from the previous surgery probably contain the free rupture and contribute to the formation of the aorto–right atrial fistula. ^4,5,7 Associated right coronary artery disruption, as seen in our patient, has rarely been reported. ⁸ Our case is different from other reported cases in that the retrograde dissection of the intimal tear extended from the aortic arch to the aortic root, causing separation of the right coronary artery and an aorto–right atrial fistula. There was no intimal tear over the ascending aorta. In our opinion, it was the right coronary artery disruption, rather than the aortic arch tear, that resulted in the aorto–right atrial fistula.

In conclusion, aortic dissection with rupture into the right atrium is an extremely rare condition that requires immediate surgical intervention in order to prevent profound shock and end-organ failure. Transthoracic echocardiography alone may not provide sufficient information for an accurate diagnosis. Transesophageal echocardiography is a useful noninvasive method to further define or confirm the diagnosis.