Tips and tricks in redo aortic surgery

Abstract

Redo aortic surgery is challenging, and the operative risk is higher than that in primary aortic surgery. Preoperative imaging is a crucial guide for a safe re-entry. Scrutinized preparing in cannulation and organ protection strategies have affected surgical outcomes. With comprehensive planning and meticulously executed surgery, mortality and morbidity can be acceptable.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12055-021-01322-x.

Introduction

The number of patients requiring redo surgery has been increasing due to various etiologies, and common causes include previous aortic dissection type A repair, aneurysmal changes, false aneurysms, and prosthetic valve infection. The hospital mortality rate has been reported to be 1.2 –16.4% [1–16] (Table 1). Re-operation presents many concerns, such as the risk of re-entry injury, complicated anatomy and pathology associated with disease, the extent of aortic root and arch surgery, and organ protection issues.

Table 1.

Early and late outcomes of redo proximal thoracic aortic surgery

Study author	Year	Number of patients (n)	Early mortality (%)	Late survival (%)
				1 year	3 years	5 years	8 years	10 years
Dougenis D et al.[1]	1997	81	8.6	89		81		69
Schepens MA et al. [2]	1999	134	6.6	89		83		62
Dossche KM et al. [3]	1999	56	5.4	91.2 ± 4.2		84 ± 6.3		76.4 ± 9.2
David TE et al. [4]	2004	165	7.2			80 ± 4	68 ± 6
Estrera AL et al. [5]	2004	104	13.5	83		80		62
Pacini D et al. [6]	2005	73	16.4	93.8		77.7		37
Szeto WY et al. [7]	2007	156	11.5	86.4 ± 2.7		72.6 ± 4.3		58.4 ± 7.8
Silva J et al. [8]	2010	58	12.1	77.9 ± 1.11	75.3 ± 0.11
Di Eusanio M et al. [9]	2011	174	12.6	81.6		74.2		44.5
Keeling WB et al. [10]	2012	122	11.5	85.9	81.6	74.2
Malvindi PG et al. [11]	2013	104	7.7	92		82		58
Di Bartolomeo R et al. [12]	2013	224	12.1	84.4 ± 2.5	79.0 ± 2.9	72.5 ± 3.4		48.5 ± 5.2
Czerny M et al. [13]	2013	60	13	83		69
Mookhoek A et al. [14]	2015	86	1.2				89
Chong BK et al. [15]	2016	66	4.5			81.5 ± 5.1		57.6 ± 9.3
Esaki J et al. [16]	2017	280	14.3			74

In this review, we have discussed about etiology, indications for redo surgery, preoperative imaging, operative planning, cannulation strategies, organ protection, and bailout strategies in redo aortic surgery.

Patient presentation and evaluation

Patients frequently present with complications after aortic valve or root surgery, such as infective aortic valve endocarditis, aortic graft infection, pseudoaneurysm after root surgery, aortic valve pathology after valve-sparing aortic root replacement, and aortic dissection post coronary artery bypass or aortic valve replacement. Patients with acute type A aortic dissection repair may develop aneurysmal changes in the residual aortic root or arch dissection during follow-up. Previous operative details are useful and can guide careful operative planning. Physical examination can be normal or reveal signs of chronic aortic regurgitation (AR). Chronic granulation of sternal wounds may be present. Widening of the mediastinum and a calcified aortic wall may be observed on chest films. Sternal wires and surgical ligation clips at the mammary artery can be observed on chest films. Lateral chest films can display the retrosternal space. Imaging by computed tomography angiography (CTA) of the thoracic aorta or magnetic resonance imaging (MRI) is the standard method used to evaluate and plan management. CTA of the whole aorta is preferred and routinely performed for preoperative planning to delineate the relationship between the aorta, aneurysms or conduits, and bony structures of the chest wall (Fig. 1). Luminal thrombosis, wall calcification, and dissection can be observed on CTA imaging. Transthoracic and transesophageal echocardiography are very useful for evaluating the aortic valve and root, other valve pathologies, and cardiac function. The severity of aortic insufficiency is considered in cases where cardiopulmonary bypass initiation is required before opening the sternum. Coronary angiography is indicated in patients with an age > 40 years and a history of coronary disease or coronary artery bypass.

Fig. 1.

CTA demonstrated false aneurysm attached posterior table of the sternum

Indications for redo surgery

Indications for redo aortic surgery can be classified into 3 categories [17]:

1. Aortic diseases

   • Degenerative aneurysm
   • Acute type A dissection with progressive root dilatation or distal aortic dilatation
   • False aneurysm
   • Chronic dissection
   • Aneurysm due to medial degenerative disease
2. Infective disease

   • Native or prosthetic valve infection
   • Vascular graft infection
3. Valvular diseases

   • Structural valve dysfunction
   • Paravalvular leak
   • Pulmonary autograft failure
   • Failure of valve-sparing root replacement (VSRR)
   • Mechanical valve dysfunction

Surgical planning

Preoperative planning is a crucial step and involves reviewing previous operative procedures and all imaging techniques. CTA provides extremely useful information for identification of vital structures beneath the sternum, such as the right atrium, right ventricle, innominate artery, aortic aneurysm, pseudoaneurysms, and coronary grafts. Cannulation sites and cerebral protection strategies can be selected based on CTA imaging. The patient should be prepared from neck to ankle such that arterial cannulation sites, including the carotid artery, axillary artery, and femoral artery, and venous cannulation sites can be accessed. Both the legs and thighs are prepared for saphenous vein harvesting if coronary bypass is required. Arterial monitoring at both radial arteries and the lower extremities is performed. Cerebral oximetry is mandatory, especially with circulatory arrest, in aortic arch surgery. External defibrillator pads are attached to the patient, and nasal and rectal temperature probes are placed. A central venous pressure catheter is inserted into the right internal jugular vein. A pulmonary artery catheter is used only in critically ill patients with severe left ventricular dysfunction. Transesophageal echocardiography (TEE) is used to guide the position of the femoral venous cannula and the deairing process and evaluate cardiac function. Cardiopulmonary bypass is initiated before opening the sternum in cases with close adhesions between the sternum and the anterior cardiac surface, the ascending aorta or bypass grafts and in patients with severe functional tricuspid regurgitation, hemodynamic instability, previous mediastinitis, or a depressed ejection fraction (EF < 25%) [18]. In patients with aortic aneurysms in close contact with the sternum or with an aorta-to-sternum distance < 10 mm, presternotomy cardio-pulmonary bypass (CPB) initiation is necessary [12]. The sternum is divided using an oscillating saw, and sternal wires are left in place if a high risk of organ injury is a concern. The sternal wires can be removed if the likelihood of organ injury is low or CPB is initiated before opening the chest. Sternal retractors and sharp dissection starting from the subxiphoid region to the anterior cardiac border can be applied. The ascending aorta and right atrium are identified for central cannulation. Heparin is administered after all structures are dissected to avoid raw surface bleeding (Video 1).

Cannulation strategies

Cannulation strategies and good surgical planning have markedly affected surgical outcomes in redo aortic surgery. The most crucial initial step is completely gathering information from previous operative notes and preoperative imaging. The goals of cannulation are to ensure adequate organ perfusion, divert circulatory blood flow from the heart to ameliorate bleeding in cases of cardiac injury, and decrease the likelihood of cardiac and aortic injury during sternal re-entry. Moreover, the cannulation strategy should minimize embolic complications. Central cannulation is associated with protective effects on in-hospital mortality and permanent neurologic deficits compared to peripheral cannulation [19].

Arterial cannulation site

Median sternotomy

The site for arterial cannulation is determined by whether safe sternal re-entry can be achieved, the extent of the disease/operation, disease along the descending aorta down to abdominal aorta, and the severity of the cardiac pathology, such as the severity of aortic valve regurgitation and left ventricular ejection fraction compromise.

Sternal re-entry injury with exsanguinous bleeding is catastrophic and can increase mortality to as high as nearly 50% [17]. If a patient has a high risk of sternal re-entry injury, peripheral aortic cannulation is mandatory. The following conditions are considered when performing peripheral cannulation (such as axillary or femoral artery cannulation) with CPB support before sternal re-entry [18].

1. Close adhesions between the sternum and the anterior cardiac surface, the ascending aorta or bypass grafts (computed tomography scans)

2. Functional tricuspid regurgitation

3. Hemodynamic/electrical instability

4. Poor left ventricular function (LVEF < 25%)

5. Previous mediastinitis

However, performing CPB before the operation has some drawbacks due to early systemic heparinization and a prolonged CPB time, which might increase the risk of bleeding. The CPB time can be minimized by temporary CPB suspension after safe re-entry.

Another concern is that although CPB before sternal re-entry facilitates safer re-entry and easier dissection due to more working space because of the collapsed heart, this technique does not totally prevent exsanguinous bleeding from aortic injury. Therefore, in cases of unavoidable aortic injury from sternal entry, such as giant aneurysms that adhere behind the entire sternum, hypothermia with a circulatory arrest technique must be applied. Two options for antegrade cerebral perfusion during circulatory arrest are available, including right axillary cannulation with a cervical incision to control the proximal innominate artery and bilateral carotid artery cannulation with proximal control [20] so continuous cerebral perfusion can be maintained. For the first technique, preoperative computed tomography (CT) scans must be thoroughly examined to determine whether the innominate artery can be accessed through a cervical incision.

In operations involving the aortic arch or requiring circulatory arrest, right axillary cannulation should be the first choice, which allows uninterrupted cerebral blood flow and can reduce the risks of stroke and in-hospital mortality [21, 22]. In our institute, an 8-mm Dacron graft is end-to-side anastomosed to the axillary artery for cannulation. Axillary cannulation via the side branch is our standard technique due to reduced cannulation site complications, such as arm ischemia and artery dissection [23, 24]. Another option in this scenario is innominate artery cannulation. This technique may be preferred in cases with a low risk of sternal re-entry injury and an innominate artery with an adequate size and good quality. Both direct cannulation and Dacron graft conduits can be used based on individual preference. Innominate artery cannulation also provides the benefit of cerebral protection. Moreover, this technique has shown comparable outcomes to those of axillary cannulation [25, 26]. The femoral artery is used in young patients with clear descending aorta and small axillary arteries and in emergencies. In cases where safe re-entry can be performed and circulatory arrest or associated aortic arch surgery is not required, standard central cannulation can be employed. However, in every case, both groins should be prepared such that femoral cannulation can be implemented rapidly if unexpected situations occur.

If disease along the descending and/or abdominal aorta is observed, especially in patients with a high burden of thrombosis or atheromatous debris, retrograde flow from femoral cannulation should be avoided because of a high associated incidence of neurological complications [27]. Antegrade flow from the ascending aorta or a previous graft or axillary cannulation should be better options [5, 28, 29].

For patients with moderate to severe aortic regurgitation, especially those with poor left ventricular function, the heart may be distended, and ventricular fibrillation can occur after CPB initiation. Therefore, if chest re-entry is not a concern, CPB should be initiated after the ascending aorta is controlled. On the other hand, if CPB initiation is necessary before sternal re-entry, transapical left ventricular venting via mini left anterolateral thoracotomy may be useful [1, 17]. A target body temperature must be designated before sternotomy to balance the safety margin of organ protection, especially cerebral protection, and the risk of ventricular fibrillation due to a decreased body temperature.

In conclusion, axillary artery cannulation is the first choice due to its many advantages, as described above. The femoral artery is used in urgent situations and when the thoracoabdominal aorta is free of atherothrombotic pathology. Ascending aorta or previous proximal graft cannulation can be applied in cases where safe sternal re-entry is achievable.

Left thoracotomy

In patients requiring distal aortic reoperation through thoracotomy, left common femoral vessel cannulation is preferred due to the patient position. However, emboli from retrograde flow and questionable perfusion adequacy in chronic dissection are concerning issues; thus, central cannulation at a previous proximal graft or the proximal aorta can be considered.

Venous cannulation

The most common site for venous cannulation is the right common femoral vein because of simple access, and patients can benefit from full CPB support through this cannulation site [1, 5, 17, 28]. This access is useful if the right atrium is small or if the right atrium is obscured by an aneurysm. The anatomy of the right side is more favorable because the left common iliac vein may be compressed by the left common iliac artery. Intraoperative transesophageal echocardiography is a valuable tool to guide cannulation and confirm the position of the cannula. The proper cannula tip position is at the middle of the right atrium [1, 17]. The superior vena cava (SVC) is cannulated if direct retrograde cardioplegia is required or full CPB cannot be achieved through a single femoral venous cannula or an adjunct mitral/tricuspid valve is needed. In general, if sternal re-entry can be safely performed, regular central right atrium cannulation can be employed with either 2-stage or direct bicaval cannulation.

Organ protection

Cardiac protection

One of the major causes of early mortality after redo-aortic surgery is cardiac complications [1, 2, 30]. The keys to good cardiac protection include effective cardioplegia delivery, adequate left ventricular venting/avoidance of left ventricular distension, and avoidance of exsanguinous bleeding that compromises cardiac perfusion. Exsanguinous bleeding affects not only the heart but also all organs, especially the brain/central nervous system (CNS), which is the most susceptible organ/system to malperfusion damage. Prevention techniques have already been discussed in the section on cannulation strategies.

Direct retrograde cardioplegia is a valuable technique in this challenging situation. After entering the pericardial space, another SVC cannula is directly inserted. Then, the right atrium is opened, and a purse string suture with 4–0 or 5–0 polypropylene sutures is created around the coronary sinus opening. Next, a retrograde cardioplegic catheter is inserted shallowly into the coronary sinus opening such that the tip of the catheter does not block the middle cardiac vein, and right ventricular protection can be achieved. This technique is very useful in patients with significant aortic regurgitation, leakage from a previous proximal anastomosis at the aortic root level or a false aneurysm communicating with the cardiac chamber, and previous coronary artery bypass grafting (CABG) and in cases in which the ascending aorta cannot be controlled. However, after cardiac arrest, another half dose of cardioplegia is administered directly into the right coronary ostium to ensure good right ventricular protection. Another alternative option for retrograde cardioplegia is direct antegrade cardioplegia through both coronary ostia and previous vein grafts. Advantages of this technique include fewer suture lines and fewer cannulas causing interference during surgery. In cases where the ascending aorta can be controlled and no leakage from the aortic root or aortic regurgitation is noted, simple antegrade cardioplegia via the aortic root is normally applied.

With the thoracotomy approach, another method to administer cardioplegia is by using an endovascular aortic occlusion balloon. After circulatory arrest, the distal aortic arch is opened, selective antegrade cerebral perfusion is established, followed by retrograde placement of an aortic occlusion balloon at the ascending aorta, and antegrade cardioplegia is administered through the central lumen of the balloon catheter.

Redo cases post CABG with a patent left internal mammary (LIMA) graft are very challenging. The most important step is to avoid graft injury during sternal re-entry and adhesiolysis. The next concern is managing patent LIMA grafts, and at least 2 options can be considered. With the first option, LIMA grafts must be isolated and controlled before cardioplegia administration. The second choice is leaving the LIMA in place and cooling the patient with frequent cardioplegia administration. The first method involves a risk of graft injury during dissection but may provide better cardiac protection [16].

To avoid ventricular distension, in patients with significant aortic valve regurgitation, adequate venous drainage to decompress the heart should be performed before establishing flow through the arterial cannula, followed by adequate left ventricular venting. In redo cases, ventricular venting through the right superior pulmonary vein as usual may be difficult due to adhesions. Venting through the pulmonary artery can be a simple and useful method. Transapical venting through minithoracotomy is another solution in severe aortic regurgitation cases.

For the thoracotomy approach, the left superior pulmonary vein or left atrial appendage is another site for venting catheter insertion. Nevertheless, if both sites are difficult to access, the pulmonary artery is another choice, as in the median sternotomy approach.

Cerebral protection

Neurological complications are a concern in aortic arch surgery and operations requiring circulatory arrest. In reoperation cases, brain protection is far more challenging due to previous adhesion and sometimes when early or unplanned circulatory arrest is needed. Two major factors can affect outcomes: (1) patient pathology and risk factors for cerebral complications and (2) cerebral protection techniques and cerebral blood flow monitoring.

Patient factors have a considerable effect on surgical planning. Most information is derived from preoperative imaging, such as atheromatous lesion/thrombus locations, the degree of carotid artery stenosis or arch branch lesions, the blood supply to the brain from the true or false lumen, and the degree of false lumen thrombosis, among others. The surgical planning goal is to prevent emboli to the brain and malperfusion. Many studies have shown that embolic phenomena and/or patient pathologies affect neurological outcomes more than cerebral perfusion techniques [31–33]. Indeed, meticulous preoperative imaging interpretation is a crucial step.

In our institution, selective antegrade cerebral perfusion (SACP) through all three aortic branches with a cold blood flow rate of 15 ml/kg/min with moderate hypothermia (20–25 °C) is a standard protocol. Bilateral radial arterial lines are used to monitor the adequacy of perfusion pressure (the target pressure is 40–60 mmHg). Near infrared spectroscopy (NIRS) is used to monitor brain perfusion. Parameters from NIRS are used to adjust perfusion flow or even surgical interventions during the operation, such as revision of arch branch anastomoses due to stenosis, kinking, or an inappropriate length. The SACP method is used because deep hypothermic circulatory arrest alone has a limited safe duration (the stroke rate increases after 40 min), and when comparing SACP and retrograde cerebral perfusion, although 2 large studies showed no differences in neurological outcomes [34, 35], only SACP has been reported to have a safe perfusion time up to > 90 min and was not related to mortality or adverse neurological outcomes [36]. Unilateral cerebral perfusion has also been used [16], but an incomplete circle of Willis can be found in 20–30% of cases [37]. Moreover, bilateral brain perfusion has a longer safety duration than unilateral perfusion [38].

Bailout strategies

During a redo operation, many problems can be encountered, such as organ injury during re-entry and cerebral protection, myocardial protection, and bleeding issues. A well-planned strategy and team orientation, communication, and coordination are very important to prevent such devastating events.

Re-entry problems

Preoperative imaging is always thoroughly evaluated. Tubing and cannulas are prepared for use in the operative field. In an eventful situation, if an underlying structure is injured while sawing the sternum, especially the aorta, tight swab packing and chest compression are performed. Full heparinization is administered, the femoral artery and vein are urgently cannulated, and CPB is established. The patient is cooled to 25 °C, and then CPB flow is decreased before opening the sternum. Bleeding at the right atrium or right ventricle is carefully controlled by local suturing. If local control is not possible, the ascending aorta is cross-clamped, and cardioplegia is administered. In the case of ascending aortic aneurysm injury, the patient is cooled to 20–22 °C to achieve circulatory arrest and adjunctive brain perfusion, and then the entire sternum is opened.

Cerebral protection

Bilateral cervical areas are always prepared under the assumption of a high risk of re-entry injury, especially in patients with large aneurysms posterior to the sternum. CPB should be established and cooling applied until the temperature is 20–22 °C, and then the chest is carefully opened. With the head-down position and cold pack application around the patient’s head, the innominate artery and left common carotid artery are directly cannulated, and SACP is initiated. Occasionally, combined retrograde brain perfusion via SVC cannulation can be useful for cerebral cooling and to prevent cerebral air embolism or thromboembolism.

Myocardial protection

Systemic cooling and regular cardioplegic perfusion are mandatory. Local topical cooling may be inadequate due to limited dissection of the whole cardiac chamber from the pericardium. In cases of severe aortic valve insufficiency, the ventricular venting route is a challenging issue. Direct coronary and retrograde coronary perfusion can be used as a combined technique. We usually use Custodiol-HTK cardioplegia (Custodiol-HTK Koheler Chemie, GmbH, Bensheim, Germany) or del Nido cardioplegia solution to perform uninterrupted surgery in these complicated cases. In redo aortic root surgery, coronary button mobilization and reimplantation require meticulous techniques to avoid tension and kinking. The Cabrol/Svensson modification which comprises ascending aortic replacement with graft interposition for the left main coronary artery and using the button technique for the right coronary artery [39] or coronary artery bypass can be bailout procedures if direct coronary implantation cannot be executed perfectly.

Bleeding problems

Severe coagulopathy can be observed in complex redo surgery after a long CPB time. Meticulously secured sutures at all anastomoses are crucial. Many areas of raw surfaces can be secured by cauterization, blood components, or tissue sealants. Recombinant activated factor VII and the factor IX complex can be useful in diffuse bleeding situations. Rotational thromboelastometry (ROTEM) can be used to evaluate disorders of blood clotting factors and fibrinolytic processes and guide blood transfusion. Finally, if generalized oozing is encountered despite all possible hemostasis efforts, mediastinal packing with a negative-pressure wound dressing is a practical method. Most bleeding will stop within 12–24 h after coagulopathy correction.

Management of post CABG dissection

Preoperative chest X-ray, CTA, and coronary imaging can provide the information of graft location, patency, and mobility. Re-entry must be careful to avoid injury to all graft conduits and aortic dissecting aneurysm.

Long venous cannulation from femoral vein is preferred if right atrium cannulation is obstructed by overlaying graft conduit. Minimize graft manipulation is necessary to avoid squeezing debris into proximally and distally of the vessels. Retrograde cardioplegia is an enormous advantage if preoperative conduit occlusion was detected.

Dissected aorta was resected, the proximal graft conduits can be reimplanted to aortic graft if their quality is good.

The dissection may involve proximal vein graft anastomosis. In this situation, the new graft conduit may be used.

Management of post aortic valve replacement (AVR) aneurysm/dissection

Aortic valve prosthetic function is mandatory to evaluate preoperatively. If valve is normal function, the cardioplegia can be given with antegrade route and valve can be left in place. Retrograde cardioplegia is used if the prosthetic valve is malfunction. Dissected aortic tissue is removed, then ascending aortic graft or aortic root is replaced. Coronary reimplantation can be performed as button technique or Cabrol/Svensson modification technique. The good prosthetic valve can be kept in place.

Management of pseudoaneurysm and endocarditis

Preoperative CTA imaging is mandatory to evaluate relationship between pseudoaneurysm and sternum.

CPB is commenced before re-entry if large aneurysm is closed to the posterior wall of the sternum. The left ventricle is vented in severe AR before opening the sternum. Deep hypothermic with circulatory may be necessary. Aortic root replacement is performed if perivalvular infection is present.

Conclusion

Redo aortic surgery can be performed safely with acceptable mortality and morbidity in experienced centers. With good preoperative planning and re-entry strategies, meticulously executed surgery, and optimal organ protection, a low operative risk can be achieved.

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Conflict of interest

The authors have no relevant financial or non-financial interests to disclose.