CLE Care of Aortic Disease: Thoracoabdominal Aortic Aneurysm

Podcast Transcript

Announcer:

Welcome to Cleveland Clinic Cardiac Consult brought to you by the Sydell and Arnold Miller Family Heart, Vascular and Thoracic Institute at Cleveland Clinic.

Sean Lyden, MD, PhD:

And I want to invite up Paul Cremer. He's a cardiologist in the Section of Cardiovascular Imaging. He's the Associate Director of the Cardiac Intensive Care Unit. He's the Associate Director for Cardiovascular Medicine Training Program at the Cleveland Clinic. And he's going to talk to us about the preoperative phase imaging modalities for detection and assessment. Paul.

Paul Cremer, MD:

Excellent. Thank you Sean. And thank you for the invitation to speak with you today. I think my perspective is somewhat unique in that I'm a cardiologist and a cardiovascular imager. So one day I may be reading the CT scans on the patient and the next day I'll be caring for them in our ICU during the preoperative management. So what I'd like to do is really two things. The first of course is to highlight the preoperative imaging evaluations. And I'm going to spend most of the time talking about how we think about our CTA protocols because that ends up being a lot of the questions that I get as an imager from the trainees in the middle of the night. And then also highlight just some case examples that may be indicative of aneurysmal instability.

But the first thing I want to emphasize is that symptomatic aneurysms are auto launches. So these are patients who just come immediately to our ICU. And we often get that of course, with the dissections, but I always emphasize to the trainees that if the patient is having chest or abdominal pain and have got an aneurysm, they come here immediately. So the imaging always has to be placed within a clinical context. And then we're set up in a way where the images arrive to us before the patients. So we're able to review those images and have a tentative plan in place. And it's particularly important that a lot of these patients have had prior studies and we definitely want to compare those to appreciate any subtle findings.

So again, I think this is familiar to this audience, but it's important to emphasize that especially for us as cardiologists, as cardiovascular imagers, that we need to make sure we're speaking the same language in terms of the Crawford classification Type 1 being above the six intercostal space to the origin of the celiac access and SMA, Type 2 from above the six intercostal space to the infrarenal segment, Type 3 from the distal half of the descending thoracic aorta into the abdominal aorta and Type 4 involving the entire abdominal aorta. So again, you just need to know these classifications so that we're all on the same page.

Similarly, and all the dissections, aortic pathology, we always refer to the zones as was noted in the case in terms of where the pathology begins and ends. And as it relates to endo leaks, again, just to remind everyone that Type 1 is when there's incompetent seal at the proximal or distal site. Type 2 is when there's flow into the sac from patent vessels, usually intercostals or lumbars or IMA, Type 3 is dissociation of the modular components, and Type 5 is the endo tensions when the aneurysmal sac is expanding and you can't identify a leak.

All right, so the echocardiogram evaluation for the thorough abdominal aneurysms is pretty straightforward. And I think it's worth noting that every patient upon arrival to the ICU has a surface echocardiogram as the vascular and cardiothoracic surgical teams are doing their evaluation. And in this context, our assessment is really focusing just on left and right ventricular systolic function. Is there any significant valvular disease? Again, usually the aortic pathology is well defined from the CTA that's been previously obtained. But I would note that if there are any remaining questions regarding the aorta, with echo it often requires off axis imaging to better delineate that with ultrasound.

Okay, so I want to spend the next few minutes just talking about how we think about our CT assessments of these patients. And there's really four basic components as it relates to the field of view, what we do with contrast, our slice thickness, and whether or not we need ECG gating. So for the first thing, field of view, of course we want to see the entire aorta, so our field of view is from the thoracic inlet to the ischail tuberosities. And the reason we do this is because we need a continuous data set for the entire aorta for appropriate procedural and surgical planning. And it's also essential to have this so that we can use our centerline multiplanar reconstruction to make bi-dimensional measurements orthogonal through a centerline through the aorta. And it's been shown that that approach is the most reproducible in terms of intra and inter observer variability.

Okay, the next question that comes up is what do you do with the contrast? Obviously a lot of these patients are getting three phase scans, non-contrast, arterial and delayed phases. And I'll touch upon why we have that approach. But first, here's just an example of what we typically do, which is boulus tracking. And this is a patient that has an ascending type an aortic dissection. But I just highlight this case because in the setting of a descending aortic dissection, often if it's there, your region of interest may miss the boulus tracking. So, your technologists really need to be aware in watching these patients and be able to automatically trigger the scan if necessary.

So usually if there is an endovascular stent that's known or we see that on a scout, we're going to do a non-contrast. That again, is if there's any hyperattenuating surgical material that may be difficult to distinguish from an endovascular leak. All the patients are going to get an arterial phase study. And in the delayed phase, there's several considerations. Of course if there's an endovascular leak, you may appreciate it on the delayed phase, which you don't see on the arterial phase imaging. If there's a large aneurysm, you may not pacify the entire sac. You may not be able to see the branch vessels. Similarly in the setting of a dissection, you may not see opacification of the false lumen, just on the arterial phase. And in the setting of rupture, if there's active extravasation, you may only see it on the delayed imaging and not the arterial phase.

The next thing we consider is slice thickness. So we routinely will do three millimeter and one millimeter or sub-millimeter slices. And these thinner reconstructions are very helpful for endo stent planning and allows visualization of the fenestrated grafts and endo leaks. So here you can see an example, same patient, same scan of three millimeters and one millimeter, and the increased signal you get with the smaller slice thickness. The final consideration is ECG gating. Now for thoraco evaluations, we don't usually need this. And it's usually necessary if we're interested in motion of the heart and the air recruit during the cardiac cycle. Now this can be often a fake out. This is an example of a patient who was sent for auto launch or question of an auto launch for an ascending aortic dissection and this is clearly just a lot of motion at the aortic route. I would say with our modern scanners, with our Siemens flash and force scanners, we can often perform high pitch spiral imaging of the entire chest abdomen and pelvis with ECG gating.

So what's our approach? So for our patients, we really have two protocols that we use most often. The first is our ICU dissection protocol where we're doing an arterial phase acquisition of the chest, abdomen and pelvis. And then we follow that by a delayed acquisition that's ECG gated of the chest in case we're looking for any concern for aortic group pathology. And then we also have a stent protocol where we're doing arterial phase spiral acquisitions of the chest, abdomen and pelvis, followed by delayed imaging. And again, if patients have a known endo stent seen on scout imaging, we'll do a non-con as well.

Okay, so I'll conclude just by highlighting a few case examples. So this was a patient who was relatively recently auto launched to us, and the outside read was there's intramural hemorrhage, there's disrupt in calcium, this patient needs to come right away. And again, this just speaks to one, I guess, knowing kind of how to interpret the images, but two, also having prior imaging available. And this is something that we commonly see. So there's clearly been progression of the aneurysm over the intervening years. But this is really just layering of mural thrombus and the pattern of calcification looks quite similar. And I think what on the outside this sometimes gets confused with is the crescent sign, which is when you have hyperattenuating intramural hemorrhage. This is on a non-contrast, so you can appreciate this hyperattenuation here. And importantly, after you give intravenous contrast, the crescent should be brighter, should have more attenuation than the psoas muscle.

So here's an example of a focal outpouching and a contained rupture of the visceral aorta. And in terms of other signs of aneurysm instability, here's an example of periaortic hematoma. So this is soft tissue attenuation, often a posterior lateral but can be circumferential around the aorta. And then of course, this is a ruptured abdominal aortic aneurysm, which actually Dr. Lyden recently treated a few months ago where you can see obvious right retroperitoneal blood products.

So to conclude my talk, the key takeaways for us are really to speak the same language, to know the classifications, the Crawford, the aortic segmentation, how we describe endo leaks. And then as you approach your CT scanning, really know what you want and the basic considerations are your field of view, what do you want to do with the contrast timing, the slice sickness, and whether or not you need ECG gating, and then knowing some of the signs of aneurysm instability. But again, I would emphasize that these really need to be placed in a clinical context and it's essential to compare to prior imaging if available. Thank you.

Sean Lyden, MD:

Andrew Bauer, who's one of our cardiothoracic anesthesia staff, and he's going to talk about the cardiothoracic anesthesia perspective. What should the anesthesiologist know in terms of getting us through these cases together?

Andrew Bauer, MD:

Thank you, Sean. Thank you for the invitation. We'll talk briefly about the anesthesia perspective and role in the care patients with open thoraco abdominal aortic procedures. We'll talk about basic principles and kind of run through the basic workflow of how we prepare and carry out one of these procedures in the process. So key points, and the first one I put up here that I think is very important, and it was just mentioned at the conclusion of the previous talk is effective communication during these procedures is paramount between everybody involved. Experienced personnel as well as active preparation is essential for good outcomes in these procedures. And then we're just going to break down the basic management principles into sort of three segments of one is resuscitation during these open procedures. This is an ongoing process throughout the entire procedure, which is different from a lot of other procedures that cardiothoracic anesthesiologists are involved in, management of spinal cord perfusion throughout the perioperative period and continuing into the postoperative period, and then understanding of some of the distal reperfusion techniques that are used during open surgery.

From an anesthesia perspective, these can kind of be divided into three stages. The stage prior to the aortic clamping, which involves induction of anesthesia and then the surgical exposure and dissection, during the aortic clamp period and distal reperfusion, and then after unclamping and discontinuation of distal reperfusion. In terms of preparation, one of the key things is to have a multiple disciplinary discussion, any specific patient issues. This can include any differences from normal and cannulation strategy positioning, and any differences in anatomy that might alter the normal conduct of the operation that the team needs to know about. Blood product availability and the antibody status should be confirmed in advance. If there are any issues or any specific difficult to find antibodies, it's probably a good idea to talk to the transfusion medicine service ahead of time about what the alternative strategy would be. If you have extensive bleeding and you exhaust your cross specific blood, ability to have a rapid infusion should be available and ready to use. Spinal drain should be placed. This can be done either in an interventional radiology suite preoperatively if the patient is admitted or it can be done in the OR on the day of surgery and the ability to monitor CSF pressure.

From a management of the airway and ventilation, these procedures require an extensive period of time where the left lung is deflated. We prefer to use a double lumen tube for this because it allows for better isolation of the lung. It allows for better management of edema or bleeding in the left lung if it were to occur. When this does occur, it usually occurs around the time of reinflation of that lung.

In terms of access, we usually obtain large central venous access in both the upper extremity and lower extremity venous systems. This allows both for rapid resuscitation and it also allows for a degree of redundancy should any issues arise with either of those access sites. Arterial pressure also needs to be monitored above and below. This allows monitoring of both pressures during aortic clamping and during distal reperfusion. Femoral access is usually preferred on the right as the left side will be prepped into the surgical field for our cannulation for distal reperfusion.

In terms of resuscitation during the first stage of the procedure prior to the clamping of the aorta, the resuscitation goals are mainly to replace fluids that are lost. You have large open thoracic and abdominal cavity, lots of evaporative and insensitive losses. There are many endpoints that can be followed to try to maintain adequacy of resuscitation, but the key goal here is that the patient should be euvolemic and stable prior to clamping and opening of the aorta. Need for blood products at this point is typically going to depend a lot on the degree of difficulty of the dissection, how much surgical bleeding there is, and then of course any preoperative anemia or coagulation deficiencies that the patient may have.

Once rapid blood loss does occur, which usually ensues around the time of clamping and opening the aorta, it's important to replace this blood loss with blood products. We utilize a rapid infusion system while the patient is heparinized that allows suctioning and re-transfusion of the patient's blood directly. If large amounts of red cells or red cells vs cell salvage are required, it's important at this point to add in FFP in a balanced way to maintain circulating coagulation factors. It's also important to order platelets and cryoprecipitate in proportion to the degree of bleeding and any expected coagulopathy. And these are usually given after discontinuation of distal reperfusion and in reversal of any anticoagulation.

Frequent laboratory monitoring is essential, usually every 30 minutes to maintain adequate anticoagulation, assess the adequacy of your resuscitation and treat any metabolic derangements that may occur. Thromboelastography and coagulation studies are useful to monitor the progress on treatment of coagulopathy. However, during periods of rapid blood loss and rapid resuscitation, treatment of clinical coagulopathy should see without waiting for lab results to come back.

In terms of spinal cord protection, the main role we have as anesthesiologists is optimization of spinal cord blood flow. Recall that the spinal cord perfusion is dependent on your mean pressure minus your spinal pressure. This is compounded by the fact that placement of an aortic cross clamp is going to raise your CSF pressure, lower the distal aortic pressure and interrupt flow to the intercostal profusing vessels. A multimodal strategy is utilized that involves CSF drainage, monitoring of CSF pressure to determine how much blood pressure augmentation is necessary, augmentation of blood pressure and avoidance of hypotension, that should continue throughout the perioperative period and into the postoperative period, distal reperfusion techniques, and mild systemic hypothermia.

In terms of distal reperfusion techniques, there are several that are available. There's veno-arterial ECMO. There's left atrial femoral bypass. There's proximal to distal aortic bypass. And while they different implementation, the goals of these techniques are essentially the same. They provide distal spinal cord perfusion by providing blood flow and perfusion pressure to the pelvic and hypogastric arterial inflow. They attenuate the pre-load and after load increases that you see with a high aortic cross clamp. And they allow for a selective reperfusion of the visceral and renal vessels. Flow is usually about one and a half to two liters depending on the size of the patient. And this gives you an index of around one to the lower body of the patient.

When distal reperfusion is initiated, you usually want to make sure that pre-load is adequate, that you can both maintain your distal reperfusion flow and maintain adequate pressure in both arterial lines. This gives you good flow to the lower body, good unloading, and it also allows you to have a good perfusion pressure to both the cottle and cephalad inflow to your spinal arterial system. Temperatures should be monitored in both core and peripheral sites. This allows for uniform cooling and then uniform rewarming. Any adjunctive therapies such as atropine and lidocaine or intrathecal should be discussed before initiating distal reperfusion and cooling and are typically administered before cross clamping.

Just a brief overview of the distal reperfusion setup that we're currently using. This is a modification of a cardiopulmonary bypass circuit. You can see that there's a venous line that bypasses the reservoir and goes directly to a centrifugal pump. This venous line can be connected to a cannula either in the systemic venous system for VA ECMO or in the left atrium for atrial femoral bypass. This is then pumped through a heat exchanger oxygenator which is typically used primarily for heating and cooling, although it can support oxygenation and ventilation partially if needed, and the blood is then returned to the femoral artery via the arterial catheter.

There is a secondary line that comes off after the heat exchanger that goes over to that roller pump that's on the right and then is pumped through a secondary heat exchanger. This is the setup that's used for cardioplegia during pump cases. But in the case of open thoraco abdominal aortic surgery, use it to be able to control the flow rate and the degree of cooling to the blood that will be sent back to the field to be used to perfuse the celiac SMA and the renal arteries. After the aorta is unclamped from the patient's rewarmed and distal reperfusion is discontinued, the keys here from an anesthesia perspective are to continue resuscitation and addressably treat coagulopathy until the point that hemostasis is adequate for closure to ensue.

Management of spinal cord profusion follows the same goals as prior. And CSF drainage and maintenance of augmented mean arterial pressure will continue into the ICU in the early postoperative period. It's also important at this point to maintain an adequate hematocrit to maintain adequate oxygenation carrying capacity. And communication remains important here in particular. Progress on treatment of the surgical bleeding, progress from our end on treatment of the coagulopathy, and then any changes in transfusion needs or bleeding should be communicated amongst the team. Overall transfusion needs should be improving with time. If transfusion needs are staying high or they're worsening, then that should prompt a more aggressive treatment of coagulopathy and a search for additional sites of bleeding.

So just a few key takeaways from the anesthesia perspective. Resuscitation is an ongoing process throughout the procedure. It's probably one of the most important things that we can impact in these procedures and it's important to treat the coagulopathy aggressively as well as replace the circulating volume. Management of spinal cord perfusion is a multimodal strategy that's really a total perioperative strategy that needs to be continued into the ICU. And understanding and discipline managing of distal reperfusion is key. At the end, I put keep it simple because I think if there's one takeaway for anesthesiologists, it's to focus on the basic core principles and to execute them well.

Sean Lyden, MD:

Thank you, Andrew.

Andrew Bauer, MD:

Thank you.

Sean Lyden, MD:

Next we're going to go onto the post offer of management considerations. I'm going to invite Sagar Kalahasti. He's the Director of the Marfan Syndrome and Connective Tissue Disorder Clinic, and he's a member of the Aortic Center and a staff cardiologist at the Cleveland Clinic.

Sagar Kalahasti, MD:

Thank you, Sean, and good morning to everybody. So my task over the next eight to 10 minutes is to talk about post-operative management and considerations. What I wanted to do with this is to talk about a case just to show the advantage of being in a comprehensive aortic center and what treatment options can be offered. It's a 76 year old female who's been seen at the Cleveland Clinic, myself and Eric for many years now, since 2013. She has a classical risk factors of hypertension and smoking. She was in good medical therapy, but she has had very slow increase in aortic dimensions and she was recommended elective repair. And her coronary angiography showed non-obstructive CAD. So this was a scan from 2013 when we first saw her. She had moderate dilation of the assenting as well as descending. She has diffused aneurysmal disease. And upon follow up until 2020, she had continued increase in size and reached a size where we felt that elective surgery would be better for her. So, I'm going to move on to the next slide.

So she had a stage repair with a stage one with an ascending and transfer [inaudible] replacement with the frozen elephant trunk along with the tricuspid valve repair and clipping of the left radial appendage. Her post-operative course was notable for atrial fibrillation and mental status changes, but no stroke was diagnosed on non-neuro imaging. And she returned. So this was after her initial surgery with the ascending graft and the frozen elephant trunk with stenting of the left subclavian artery. So she came back in January and had a TEVAR extension up to the zone five. This time, her post-op course was sustainable for severe bleeding in the fecal sac from spinal drain placement that had led to binary incontinence and retention. But both of these improved with time and did not require any specific intervention. So, this was the imaging done when she returned for follow up in April of 2021.

So as Paul had already mentioned, and many of you in this audience already know the different classifications of repairs. And so if you look at the open repairs, the highest risk of complications, typically when we think about renal impairment or spinal cord ischemia, it's mainly with the Type 2 and Type 3 repairs. And I'm going to take a journey through the years with regards to the outcomes. And Gustavo has already highlighted some of these. Talking about where we were and where we are. If you look at all these publications going back from 1993 when Dr. Svensson was at Houston and 30-day mortality about 8 percent in that series and incidence of paraplegia was about 16 percent. And as you continue to move along the timeline from 93 to 2000, the progressive reduction in mortality as well as in paraplegia, and I can keep going on with multiple different studies looking at that.

As you move through this timeline, you can begin to see the endovascular treatment approaches have begun to become more and more common with Dr. Greenberg being here and Eric working with him. And you can see the improvement with regards to mortality as well as the decrease in complications and the combination of different techniques between open repair and combination with endovascular stenting. And you can see that there is more and more awareness about the safety and feasibility of endovascular stenting and also decrease in risk of complications. So, as we go along with this, as Gustavo has recently showed in his talk that it seems like endovascular treatment may become a favored approach in the majority of these patients and more and more of fenestrated and branched endovascular stent options are available in this current day and age.

So if you were to think about most of the patients with TAAs, most of them are degenerative type aneurysms compared to genetically mediated diseases. And this is one of the papers that Tony had mentioned yesterday that you could use a combination approach in some of these patients. And this is one of the studies that Eric had published. Looking at beyond the aortic root and staged open and endovascular repair of the arts and descending aorta, patients with connective tissue disorders and operative mortality was about two and a half percent and a very small number had complications. And if you look at their overall survival was some excellent up to 10 years of follow up. So one of the goals of immediate post-operative management, there are two different parts of it. One is the immediate post-op management, and some of this was highlighted by Andrew with regards to what are the things that you look for.

This was an excellent paper published from the Houston Group recently in JTCVS looking at the post-operative care. And if you look at the overall goals, you can divide them into many different organs and systems. If you look at brain and spinal cord, you want to recognize the underlying defect or underlying complication and how do you manage them immediately. And that's where the teamwork comes into the picture. And if you recognize any focal neurologic deficits, calling neurology immediately and doing imaging to understand what the underlying problem is and treat accordingly. I'll not go more in details of the spinal cord protection because Andrew had covered it pretty well. And looking at lung protective ventilation and also local heart function on adjusting the pulmonary status, based on what the patient's recovery has been. It's very important. Again, volume resuscitation is an important thing, and if patients end up in atrial fibrillation, then restoring sinus rhythm would be very helpful in maintaining proper perfusion.

And if you look at renal function, again, adequate resuscitation with fluids and constantly checking on labs to make sure that you are staying on top of the complications and not catching up, again, renal transfusion that's needed based on the patient's parameters. So how about if you look at long-term care, again, yesterday's [inaudible] and some of the other speakers have covered about long-term management with blood pressure control. I'll not going into details of all the different mechanisms of action, but you can understand that beta blockers, ACE inhibitors, and ARBs are very helpful in managing blood pressure over the long term. Diuretics, and if needed, dihydropyridine, calcium terminal blockers would be useful in long-term control of hypertension. Lipid management, statins. Smoking cessation is a very important element of management of these patients.

As many of the speakers have already spoke about. Avoidance of fluroquinolones and even after post repair is an important thing. We don't know the causation, but long association studies have shown that. Some of the other factors that was talked about yesterday's regular exercise and maintaining their cardiovascular status and avoid of isometric exercise would be very important.

So as far as surveillance with regards to imaging, there is no clear guidelines with regards to when the surveillance imaging. And again, it depends on whether it was an endovascular repair or an open repair. I think the 2010 Thoracic Aortic Guidelines had mentioned for patients with endovascular stenting, you should obtain a CT before discharge, three and 12 months and annually, depending on the stability of the endovascular repair. And in patients with open repair, again, this is one of the guidelines that was presented by the European Society looking at six months, 12 months, and every three to five years for open repairs. As again, as I said, there are no specific guidelines. To summarize, most of these patients, you need both strategy of immediate post-operative management as well as long-term care and understanding what the underlying etiology would go a long way in managing those patients. Thank you.

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