Circumferential Stanford Type A Acute Aortic Dissection with Proximal Intimo-Intimal Intussusception: A Case Report and Literature Review

Introduction

Circumferential acute aortic dissection is a rare condition, occurring in 2% of ascending aortic dissections, as reported by Rosenzweig [1]. Proximal intimo-intimal intussusception can be fatal and may result in severe aortic regurgitation and coronary artery malperfusion. We report a surgical case of a 76-year-old woman presenting with circumferential Stanford type A acute aortic dissection with proximal intimo-intimal intussusception.

Case Report

A 76-year-old woman living on a remote island approximately 250 km from our hospital visited a local general hospital with the chief concern of sudden anterior thoracic strangulation. Contrast-enhanced computed tomography (CT) was performed, leading to a diagnosis of Stanford type A acute aortic dissection (Figure 1A–1D). Twenty minutes after the contrast-enhanced CT, the patient vomited and showed decreased consciousness. She was immediately intubated and started on a respirator (Figure 1E). The physician contacted our hospital for emergency surgery, and we agreed to accept the patient. While preparing for transport, the patient went into shock, and the electrocardiography (ECG) monitor displayed ST-segment elevation. The physician thought that the aortic dissection had progressed, resulting in coronary artery malperfusion, and consulted us about the need for coronary angiography. We advised that no coronary angiography should be performed and that transport to our hospital should be the first priority. Consequently, the patient’s vital signs improved while administering inotropic drugs, and she arrived at our hospital approximately 5 h after the request for transport. After arrival at our hospital, she was transported directly to the operating room, and surgery was initiated immediately. Contrast-enhanced CT at the previous hospital showed that the ascending aorta was 53 mm in diameter and the true lumen was prominently compressed; however, the intimal flap was still visible. Transesophageal echocardiography after anesthesia induction showed that the intimal flap had moved to and from the left ventricle through the aortic valve (Figure 2). The prolapse of the intimal flaps resulted in severe aortic regurgitation (AR).

After a median sternotomy, a pericardiotomy was performed, which revealed a large amount of blood in the pericardial effusion but no obvious rupture of the aorta. Cardiopulmonary bypass was then initiated by cannulation of the right femoral artery and superior and inferior vena cava, and circulatory arrest was induced at the esophageal temperature of 25°C. The ascending aorta was opened, and the intima was completely and circumferentially dissected. The flapped intima plunged into the left ventricle (Figure 3). Inspection of the aortic root revealed that the dissection extended into the sinus of Valsalva; however, the bilateral coronary artery ostium and aortic valve remained intact. Therefore, we decided to perform an ascending aortic replacement. Selective antegrade cerebral perfusion was initiated by cannulating the right brachiocephalic and left common carotid arteries. BioGlu (CryoLife, Inc., Kennesaw, GA, USA) was applied to the false lumen of the sinus of Valsalva to adequately repair the proximal side. The distal and proximal sides of the anastomosis were reinforced with internal and external Teflon felt strips, and the ascending aorta was replaced with a 26-mm J Graft (Japan Lifeline, Tokyo, Japan). The operation, cardiopulmonary bypass, aortic clamping, and circulatory arrest times were 334, 176, 97, and 66 min, respectively. She was extubated on postoperative day 5; echocardiography on day 7 showed only mild AR, and cardiac function was normal. Contrast-enhanced CT performed on postoperative day 32 revealed no graft complications (Figure 4). On postoperative day 37, the patient was discharged uneventfully.

Discussion

Aortic dissection with intimo-intimal intussusception is very rare; therefore, surgeons are unlikely to operate on them. This case report aimed to assist more surgeons in treating patients with such condition in the future.

In general, aortic dissection is a fatal vascular disorder characterized by tears in the intimal layer of the aorta and separation of the aortic wall layer. Blood enters the space between the intima and media, allowing the dissection to propagate proximally or retrogradely, resulting in impaired blood flow to vital organs. Acute aortic dissection has a very high mortality rate, and many patients die before being transported to the emergency department. CT is the imaging modality of first choice in the definitive diagnosis of aortic dissection in most cases because of its high sensitivity and specificity, wide availability, and rapid imaging. This method provides detailed images of the aorta, showing complications such as intimal flaps, true and false lumens, aortic dilatations, hematomas, contrast leaks (indicating rupture), and branching vascular lesions. Aortic dissection is anatomically classified according to two systems, namely the “Stanford” classification system and the “DeBakey” classification system, although the former is often used in determining the indication for surgery. Stanford type A is defined as a dissection involving the ascending aorta and proximal to the brachiocephalic artery regardless of the site of the primary intimal tear. Type A dissection is also considered a surgical emergency because of the risk of fatal complications such as cardiac tamponade, severe aortic regurgitation, myocardial infarction, and aortic rupture. Surgical mortality rates range from 5% to 20% [2].

In acute aortic dissection, the intimal disruption rarely exceeds half the aortic circumference [3]. In 1962, Hufnagel et al first reported intimo-intimal intussusception, a complication resulting from obstruction of the true lumen or branch vessels due to the inversion of a circumferentially dissected flap [4]. Rosenzweig et al reported that this incidence is <2% in Stanford type A aortic dissection [1]. Intussusception of a mobile intimal flap can lead to severe complications. Proximally, the intimal flap may prolapse retrogradely into the left ventricle outflow tract (LVOT), causing severe AR or occluding the coronary artery ostium during diastole [5]. Distally, the intimal flap may prolapse antegrade into the aortic arch, occluding the aortic arch vessels and affecting cerebral perfusion [5].

When diagnosing aortic dissection, determining whether it is accompanied by intimo-intimal intussusception can be challenging. In particular, when aortic dissection with proximal intima-intimal intussusception is complicated by coronary artery occlusion, the symptoms may be similar to those of acute coronary syndrome, which can lead to preoperative misdiagnosis. Coronary angiography is sometimes the differential diagnosis of choice; however, it may not provide an accurate diagnosis because the intimal flap may occlude the coronary artery ostium [6]. Aortography can detect aortic dissection with an intimal flap prolapsing into the LVOT during diastole [6]; however, it is unlikely to provide sufficient accurate information to distinguish intimal valves from aortic valves [5]. CT and echocardiography are useful and practical tools for diagnosing aortic dissection with intimo-intimal intussusception. Multidetector row CT and electrocardiography-gated CT can provide clear images, detect aortic dissection with circumferential intimal flaps prolapsing into the LVOT during diastole, and distinguish between intimal flaps and aortic valves [5,7]. In contrast, in cases of intima-intimal intussusception, the intimal flap may fold back proximally or distally, leaving only the adventitia in the area of aortic dissection. Thus, contrast-enhanced CT on axial images may show flap loss. This imaging finding was called the “missing flap” phenomenon by Sanders et al. and should be noted because it is sometimes a cause of misdiagnosis [3,8,9]. Transesophageal echocardiography (TEE) can detect continuous real-time movement of the intimal flap, degree of coronary artery occlusion, left ventricular function, and degree of intussusception causing AR [5,10]. Intraoperative TEE is considered the most practical and reliable diagnostic tool for acute aortic dissection with intima-intimal intussusception [5]. In this case, the contrast-enhanced CT scan at the onset of aortic dissection showed no obvious findings suggestive of intimo-intimal intussusception; however, the previous physician noted ST-segment elevation on the ECG monitor 20 min later. This suggests that the intima completely ruptured during preparation for transport, resulting in impaired blood flow in the coronary arteries. Intraoperative TEE at our hospital showed that the intimal flap was in a to and fro state, and aortic dissection with intimo-intimal intussusception was diagnosed. Therefore, as stated in the 2022 ACC/AHA Aortic Disease Guidelines [2], in cases where aortic dissection is suspected to be complicated by coronary artery occlusion, awareness of potential intimo-intimal intussusception is crucial, necessitating prompt transfer of the patient to the operating room.

Aortic dissection with intimo-intimal intussusception can result in severe AR with intimal flap inversion, as in this case. Moreover, determining the need for aortic valve replacement for AR can be challenging. However, in patients with AR due to proximal intimo-intimal intussusception, the structure and function of the aortic valve are usually intact and can be preserved in the aortic valve [11]. Ito et al reported a valve-sparing aortic root replacement in a patient with localized aortic dissection and intimo-intimal intussusception [5]. Nakamura et al reported a surgical case of circumferential aortic dissection with intimo-intimal intussusception that did not involve aortic valve repair or replacement, similar to the present case [12]. Therefore, the indications for aortic valve replacement in aortic dissection with intimo-intimal intussusception are similar to those for typical aortic dissection. As suggested by Contreras et al, aortic root aneurysms, bicuspid aortic valves with lesions or advanced calcification, and aortic dissection involving the aortic valve ring are indications for aortic valve replacement [13]. In general, only approximately 5% of patients with Stanford type A aortic dissection require aortic valve replacement, and another 5% to 10% could benefit from aortic valve resuspension [13]. In this case, intraoperative TEE showed severe AR; however, proximal inspection revealed that, although the dissection extended to the sinus of Valsalva, the bilateral coronary artery ostium and aortic valve were not affected. Although aortic valve-sparing root replacement was considered, the Valsalva sinus was sufficiently repairable with BioGlu (CryoLife, Inc., Kennesaw, GA, USA) application, and the patient had prolonged preoperative shock vitals; therefore, the surgeon decided to perform only ascending aortic artery replacement.

Finally, although there have been several case reports of aortic dissection with intimo-intimal intussusception, the present one is particularly valuable in that it presents intraoperative findings. Surgical cases of aortic dissection with intimo-intimal intussusception are extremely rare, and surgeons are unlikely to encounter them. Therefore, it is essential for surgeons to know what intraoperative findings are obtained during surgery to make surgical decisions. Consequently, we believe that this case report, which provides intraoperative findings, will be helpful to many surgeons.

Conclusions

Here, we describe a case of Stanford type A acute aortic dissection with intimo-intimal intussusception. The patient developed circumferential aortic dissection with intimo-intimal intussusception during preparation for transport to our hospital, which led to shock. In such cases, transportation is considered a priority over any procedure for immediate surgical intervention. An important goal of emergency surgery for Stanford type A acute aortic dissection is to save the patient’s life. Therefore, the selection of the surgical procedure should consider factors such as the patient’s clinical status, echocardiographic evaluation of the proximal aorta, and surgical experience.