Abdominal Stroke Alert!

It is a rare day that passes without the announcement of a stroke alert at CCAD. A reflex arc of activity is initiated, as time becomes the critical metric of success. Patients with strokes have a limited window of time to reverse the effects of the arterial occlusion, and the whole hospital is organized around getting the patient into the angiographic suite to open up blood vessels. If you watch it happen, it is the pinnacle of modern medicine, to achieve what only a decade ago was deemed unachievable. It was built around a foundation laid by cardiologists for heart attacks -the STEMI alert. The teams practice like racing pit crews with a stopwatch to get a patient from the emergency room, to CT scan, to angio suite. A long time ago, as a young surgeon, I had to work hard to get institutional support of ruptured AAA and cold legs. Vascular surgery has traditionally struggled to get recognition for its patients, their diseases, and its work, which is nothing less than the most important safety net for any large general multi-specialty hospital, critical infrastructure like oxygen plumbing and backup generators. As I transition to that weird designation of mid-career surgeon (please don’t call me a senior surgeon), I have also appreciated that Steve Jobs aphorism about good artists copying, great artists stealing. It’s only stealing if you don’t give credit. Here is what I borrowed from the neurologists.

Acute mesenteric ischemia is an abdominal stroke. Use it in your conversations with other people as you speed your patients way into the angio suite. The reflex arc is in there. For the emergency department, the operating room, and all the physicians, acute mesenteric ischemia sounds like tummy trouble, but abdominal stroke brings sudden clarity to conversations like:

“Well, you’re in line behind a gallbladder and a cystoscopy. Is the patient NPO?”

Me: “It’s an abdominal stroke. We literally only have a few hours before the patient dies…”

“I’ll bring the backup team in!”

The patient is a middle aged man with risk factors of NIDDM and prior history of DVT who developed severe mid-abdominal pain at 5pm. He came to the ED at around 11pm and had a general surgery consultation who ordered a CT Angiogram showing SMA occlusion (pictured below).

Acute Mesenteric Ischemia case presentation

Acute Mesenteric Ischemia case presentation (1)
Heparin was started, and at 11:30, vascular surgery was consulted. The patient had a soft, doughy texture to his abdomen, but great pain with palpation -classic pain out of proportion to the exam. Determining the patient to have acute mesenteric ischemia from a thromboembolism, I took the patient to our hybrid angiographic OR suite with the plan for arteriography, possible open thrombectomy, and exploratory laparotomy.
Arteriography from femoral access showed an occlusion of the SMA beyond the middle colic artery, a typical pattern for an embolism that occurs when embolism lodges distally and propogates proximally (image below).

Acute Mesenteric Ischemia case presentation (2)
I got Glidewire access into the ileocolic terminus of the SMA, exchanged for a Rosen wire, over which I placed an 8F sheath into the proximal SMA. This was a rather large sheath meant to catch thrombus as I suctioned it out with a 6F Penumbra catheter. This is another technique I borrowed from the neurointerventionalists. Whenever a stroke alert is going on, curiosity drives me to peak in and see what marvelous gadget or gewgaw they are using, and I was impressed by how efficiently the neurointerventionalists were able to get to the smallest thrombus in the furthest branch vessels. I was prepped for open thrombectomy, consented for bypass if necessary, but having experience in suctioning clot through single catheters and sheaths, I thought the simple design of the Penumbra and its efficacy in the cerebral system could easily translate into the mesenteric.The problem with open thrombectomy is the inability to see if you have cleared thrombus from all the branches unless you do an arteriogram after you’ve completed your procedure. This may be a significant contributor to the 20-30% bowel resection rate that occurs on second look laparotomy in my old paper and in the literature since its publication.

The Penumbra was effective in removing much of the fresh thrombus, but I was also cognizant of the fact that pulling out the catheter will draw clot into the 8F sheath that did not make it into the catheter. I placed a wire, and removed the sheath to expel much of the bulky thrombus (picture below).

Acute Mesenteric Ischemia case presentation (3)

The completion angiogram (below) doesn’t show the intermediate angiograms showing thrombus that embolized to other arteries as I manipulated the catheters and thrombectomized -I was able to successfully retrieve these with selective catheterization, another neurointerventional series of maneuvers that I have successfully borrowed.

Acute Mesenteric Ischemia case presentation (4)
After being satisfied with the completion, I removed the sheaths and explored the abdomen finding this segment of infarcted small bowel (next image).

Acute Mesenteric Ischemia case presentation (6)
There was no question in my mind that there would be some dead bowel based on the time course described by the patient. Despite my excitement about calling for GIA staplers -I am general surgery boarded- I called in the general surgeons for their help in resecting and anastomosing this segment of bowel. They would be the ones taking the patient back for any second look laparotomy, although in this patient, I determined that there would likely be no need. After the anastomosis was completed, I did a Wood’s Lamp examination (pictured), which is accomplished with a black light after giving the patient an ampule or two of Fluorescein.

Acute Mesenteric Ischemia case presentation (7)
The bowel had a splotchy fluorescence pattern which is typical of ischemia-reperfusion. This is where you have to ask the anesthesiologist and any critical care specialist who follows -no pressors please! Edema won’t kill an anastomosis as badly as ischemia will, and the gut is as sensitive to norepinephrine as are the toes. Workup in the hospital including echocardiography and CTA of the entire aorta failed to reveal a proximal source or cardiac shunts or thrombus. The patient recovered and has recently followed up, eating well, and tolerating his anticoagulation which he will be on for life.
I sent out the pictures to my neurointerventional friends with some glee, but also with the purpose of informing them that in the case that the vascular surgeons become incapacitated or quarantined due to the COVID-19 pandemic, their skills would be recruited in the care of an abdominal stroke -a blood vessel is a blood vessel.
Acute mesenteric ischemia should be the first thing on everyone’s differential of sudden onset abdominal pain because of its time dependence, yet it does not have the same resonance to the unfamiliar as abdominal stroke. Survival is dismal when too much time and intestinal death has occurred. When associated with the stroke alert concept, it translates into processes already in place throughout the hospital and it becomes natural for everyone to appreciate the urgency of treating abdominal stroke. This is the system adopted by Roussel et al. in France, where they have regionalized care of intestinal stroke. They report mortality rate of 6.9%, which is in a selected population, but significantly lower than the traditionally reported 30-60% mortality.

I am still an advocate of an open approach, especially when angiographic resources are unavailable, and every trainee needs to be able to describe the exposure of the SMA, and management of acute mesenteric ischemia. Hopefully, everyone will appreciate the urgency of all the various ischemic conditions manifest in the peripheral circulation, but rebranding them as a stroke (leg stroke, hand stroke, intestinal stroke…) is helpful. Finally, there is no survival with dead bowel -it must be found through exploration and resected.

Reference:

Roussel A, Castel Y, et al. Revascularization of acute mesenteric ischemia after creation of a dedicated multidisciplinary center. 2015 Nov;62(5):1251-6. doi: 10.1016/j.jvs.2015.06.204.

Complicated Aortic Dissection Talk

A basic recipe for treating complicated aortic dissection

#aorticsurgery #tevar

Life imitates social media: a ruptured type V thoracoabdominal aortic aneurysm or IT saves a life

ARTERIAL (2) (2)
Type V TAAA Rupturing into Right Pleural Cavity

It was only last month when I came across a post of an aortic aneurysm in a difficult spot (link) and I couldn’t help chiming in some comments. Reading it now, I sound insufferable, because I wrote,

“Depends on etiology and patient risk stratification. Also assuming aneurysm goes to level of SMA and right renal artery origins and involves side opposite celiac. Options depending on resources of your institute: 1.Open repair with cannulation for left heart bypass and/or circulatory arrest 2.Open debranching of common hepatic, SMA, R. Renal from infrarenal inflow and then TEVAR 3.FEVAR from custom graft from manufacturer on protocol 4.Parallel grafting to CA, SMA, R. RA with TEVAR 5.Surgeon modified FEVAR 6.Open Repair We would have a multidisciplinary huddle around this patient -Vascular, Cardiac Surgery, Cardiology, Anesthesia, and ID (if needed) to help choose. Be ready to refer to a center with more resources -including prepping patient for transfer and imaging -including uploading images to the cloud for transfer with patient’s permission. More info please”

More Info Please, Indeed

The post I commented on was of a saccular aneurysm in the transdiagphragmatic segment of aorta. Ironically, only a few weeks later, I got called from hospital transfer center about a patient with a leaking aortic aneurysm, a type V thoracoabdominal aortic aneurysm as it turned out, from an outside hospital, needing urgent attention, and we accepted in transfer based on the conversation I had with the tranferring physician. And that was the problem -usually in taking these inter-hospital transfers, you have to pray that the precious CT scans come along with the patient burned correctly onto a CD-ROM. You can buy and watch a movie in 4K resolution over the internet -about 4 gigabytes, but a patient’s CT scan which is about 200 megabytes -because of various self imposed limits, overly restrictive interpretations of laws, and lack of computer skills, these life saving images get transferred on CD in 2019. That last time I purchased a CD for anything was over 15 years ago.

An Interested Party

The technical solution –to use the internet to transfer critical life saving information between hospitals – came about when our IT folks took an interest in my quarterly complaint email about using the newfangled internet for sharing files. After mulling various solutions ranging from setting up a server to using commercial cloud solutoins, we came upon the compromise of using our internal cloud with an invitation sent to the outside hospital. I would send this invitation to upload the DICOM folder of the CD-ROM to an outisde email address. It was simple and as yet untried until this night. “Would the patient agree to have his CT scan information transmitted to us electronically?” I asked the other physician. He assured me that the patient was in agreement.

It Takes Two to Tango

Of course, being able to transfer these pictures requires a willing partner on the other side, and the referring physician made it clear he did not have the technical expertise to do so. It took a bit of social engineering to think about who would have that ability. Basically, aside from myself, who spend all their time in dark rooms in the hospital in front of giant computer monitors? The radiologists! I got through to the radiologist who had interpreted the report and explained the simple thing I needed. Gratefully, he agreed, and I sent him a link to our cloud server. I explained to him, “When you receive this, clicking the link opens a browser window and then you open the CD-ROM and find the DICOM folder and drag and drop it on the browser window.” The 200-500 megabytes of data then get sent in electronic form, as it was meant to in 2019.

The Internet Saves a Life

The brutal truth is that in locking down a computer system, many hospitals make it impossible to even load an outside CD-ROM, creating many self imposed barriers to care. Thankfully, at CCAD, we were able to work together to find a secure solution. With the CTA on our servers, I was able to review the study within 15 minutes of accepting the patient, and arrange for the right team to be assembled, and confirm that we had the right material (stent grafts) for treating the patient. When the patient arrived, OR was ready to go, saving hours of time that normally would have been required if the CT scan had to be reviewed from the CD-ROM that came with the patient. Sometimes, the CD-ROM does not come, and in a critical situation, the CTA has to be repeated with some risk to the patient for complications of the contrast and radiation.

What to Do

The patient had a 8cm sphere shaped aneurysm arising in the transdiagphragmatic aorta, leaking into the right pleural cavity.

Screen Shot 2019-06-19 at 9.29.15 PM

The patient was otherwise a healthy middle aged man with risk factors of smoking and hypertension. The centerline reconstructions showed the thoracic aorta above the aneurysm to be around 20mm in diameter and same below, with the celiac axis and superior mesenteric artery in the potential seal zone of a stent graft. The only plaque seen was around the level of the renal arteries and was focal and calcified. Looking at the list I had made as a comment to the Linked-In post, I realized that I really only had one viable option.

ARTERIAL (10).jpeg

Open repair, usually the most expeditious option, was made challenging by the right hemothorax, making a left thoracotomy hazardous if the lung had to be deflated. Cardiopulmonary bypass would have to be arranged for, and that adds a metabolic hit that greatly raises the stakes. Of the endovascular solutions, the only viable option was TEVAR to exclude the rupture and debranching of the celiac axis and superior mesenteric artery. To those who would advocate for parallel grafts, there was no room in the normal 20mm diameter aorta. And branch systems for rupture are some time in the future. Also, the patient was becoming hypotensive. So the planned operation was first TEVAR to stop the bleeding, and then open surgical debranching. A hybrid repair.

plan sketch.PNG

The smallest stent graft we have is a 21mm graft, but it would not be suitable for this aorta. In practice, the normal aorta is quite elastic and will dilate much more than what is captured on a CTA. The next size we have is 28mm graft and I chose this to exclude the rupture, which was done percutaneously.

TEVAR angio.png

As seen below, the graft excluded the celiac and SMA. Late in the phase of the final aortogram (second panel) there was an endoleak that persisteed despite multiple ballooning. The timing suggested the intercostals and phrenic vessels contributed to a type II endoleak, but it was concerning.

postangio.png
Find the Endoleak

The bypasses were sent from the infrarenal aorta to the common hepatic artery and the SMA close to its origin, and the origins of the celiac axis and SMA were clipped. The bypasses were then done with a 10x8mm bifurcate Dacron graft originally for axillofemoral bypassing. It had spiral rings which I removed at the anastomosis and this resulted in a kink at the closer bypass. Usually, I loop this for iliomesenteric bypass but there was not enough distance from the infrarenal aorta. I have to add a little trick I modified from my pediatric surgery experience as a resident -a Heinecke-Mikulwicz graftoplasty:

IMG_2646.JPG

This worked to relieve the kink as evidenced on the aortogram above. After closing the laparotomy, I placed a chest tube in the right chest. The patient had a course prolonged by a classic systemic inflammatory response syndrome, with fevers, chills, and leukocytosis. He bled for a while but stopped with correction of his coagulopathy. All blood cultures were negative, but a CT scan was performed out of concern for the endoleak, and the possibility of continued bleeding.

postCTA.jpg

No endoleak was detected as the sac was fully thrombosed. There was a consolidation of the blood in the right chest, but it resolved with fibrinolytic therapy.

Discussion

This case illustrates several points I have been making on this blog.

  1. Hybrid repairs are not some kind of compromise but the full realization of a complete skill set. When students ask me how to judge a training program, one of the best metrics is how frequently are hybrid operations performed. It means either the endovascularist and open surgical operator are in complete synchrony or there are individual surgeons competent in both open and endovascular surgery. Hybrid operations, rather than being a compromise, are an optimization.
  2. Time -Laying the stent graft across the celiac and SMA origins starts a warm ischemia clock. The liver and intestines, in my reckoning, should be able to tolerate the 2 hours of work to get the bypasses working. Cardiopulmonary bypass may give you less ichemia but at the metabolic cost of the pump time. These negative factors add up, but were surmounted by the fact that early control of hemorrhage was achieved. Stopping the bleeding and restoring flow are the core functions of vascular surgery.
  3. Planning and preparation. The ability to see the CT images and prepare the teams and materiel before the patient transferred was lifesaving. This is where our IT gets credit for responding to a critical need and formulating a solution that meets internal policies, external regulations, and saves a life. It illustrates so many opportunities particularly with electronic medical records and their processes which focus more on documentation for billing. A discharge summary should be multimedia like this blog post and it should be normal and easy to generate. And finally, as clinicians, we should mind technology with as much attention as we give to the latest medical devices and techniques.

When good enough is better than perfect: a case of end stage visceral segment aortic occlusive disease

The patient is a woman in her 60’s who self referred for complaint of abdominal pain, weight loss, and rest pain of the lower extremities. She is a 40 pack year smoker and had severe COPD, hypertension, congestive heart failure with mitral regurgitation, chronic kidney disease stage IV, and ischemic rest pain of the legs. She had a 30 pound weight loss due to severe postprandial abdominal pain. She had bloody stools. Her kidney function was worsening, and dialysis was being planned for likely renal failure but she was against dialysis. She had consulted several regional centers but was felt to be too high risk for surgery and with her refusal of dialysis, would be a high risk for renal failure and death with intervention. Physical examination revealed weakened upper extremity pulses, and nonpalpable lower extremity pulses and a tender abdomen. In clinic, she developed hypoxia and dyspnea and was admitted directly to the ICU.

preop-cta

CTA (above) revealed severely calcified atherosclerotic plaque of her visceral segment aorta occluding flow to her mesenteric and renal arteries and to her leg. The right kidney was atrophic. The left kidney had a prior stent which looked crushed. The infrarenal aorta was severely diseased but patent and there were patent aortic and bilateral iliac stents.

Echocardiography revealed a normal ejection fraction of 60%, diastolic failure,  +2 to+3 mitral regurgitation, and pulmonary artery hypertension. She did respond to diuresis and stabilized in the ICU. Intervention was planned.

Options that I considered were an extranatomic bypass to her legs and revascularization from below. I have come across reports of axillo-mesenteric bypass, and I have performed ascending and descending thoracic aorta to distal bypass for severe disease, but concluded, as did the outside centers, that she was a formidable operative risk. Also, there was a high likelihood of great vessel occlusive disease. Looking at her CTA, I felt that she needed just a little improvement in flow -not perfect but good enough. The analogy is like drilling an airline through a cave-in. Also, her left kidney gave a clue -it was normal sized and survived the stress test of a contrast bolus for the CTA without dying. A discussion with the patient green lighted an attempt -she understood the cost of failure but did not wish to linger with this abdominal pain.

Access for intervention was via the left brachial artery. Aortography showed the severe stenosis at the origin of the SMA and the nearly occlusive plaque in the visceral segment aorta.

preintervention-aortogram

The plaque was typical of the coral reef type, and had an eccentric channel that allowed passage of a Glidewire. Access into the left renal artery was achieved. Its stent was patent but proximally and distally there were stenoses; this was treated with a balloon expandable stent. The path to it was opened with a balloon expandable stent to 8 mm from femoral access. This was the improvement the renal needed. A large nitinol stent was placed from this access in the infrarenal aorta when severe disease above the iliac stents was encountered.  The SMA was then accessed and treated with a bare metal stent.

post intervention.jpg
Renal stent was reaccessed and ballooned in this pentultimate angiogram

Her creatinine improved, as did her intestinal angina. She was discharged home. She later returned a month after the procedure with complaints of nausea and vomiting and right lower quadrant abdominal pain and was discovered to have an ischemic stricture of her small bowel. This was removed laparoscopically and she recovered well. She recovered her lost weight and now a year and a half later, remains patent and symptom free.

Discussion: Dr. Jack Wiley includes in the preface to his atlas of vascular surgery the words of Dr. Joao Cid Dos Santos, the pioneer of endarterectomy techniques, “Vascular surgery is the surgery of ruins.” And in that context, good enough is sufficient.

 

Moneyballing a Type II Thoracoabdominal Aortic Aneurysm


The innovation of sabremetrics in baseball management and finance as described in Michael Lewis’ wonderful book Moneyball wasn’t just the ability to quantify skill to predict outcomes, it was the ability to assemble that skill without overpaying. For a baseball team on a budget, spending all your payroll on a superstar makes no sense when you can get equivalent quants of skill in a statistical aggregate of no-name players with proven metrics. Rather than pay for an A-Rod, you can recruit, and pay for, 5 players that in aggregate, statistically achieve what you would get with a healthy A-Rod, so the thinking goes. How does this translate into vascular surgery? Can we arbitrage complication rates?

The open repair of type II thoracoabdominal aortic aneurysms is a heroic endeavor, putatively best done by surgeons wearing cowboy boots, and classically comes with sobering complication rates that exceed 20% for death and paralysis. Is it possible to reduce this risk by subdividing this most enormous of cardiovascular operations into component parts?

The patient is a middle aged man in his 50’s who presented with a type B aortic dissection. His dissection flap spanned from his left subclavian artery to the infrarenal aorta. He was a long time smoker and had hypertension that was difficult to control, made much worse after his dissection. He had a moderate dilatation of his thoracic aorta, maximally 36mm and tapering to 35mm in visceral segment. There was a 4.9cm infrarenal AAA where the dissection terminated.

CTA at presentation

His chest pain resolved with blood pressure control and he was discharged, but in followup his thoracic aortic segment grew and his blood pressure worsened, never getting below a 150mmHg systolic despite multiple agents. CTA two months after presentation, showed growth of his TAA to 44mm from  36mm in two months  and the visceral segment showed that his dissection flap impinged on flow to the right renal artery. His AAA remained the same. He continued to have bouts of chest pain related to hypertension.

CTA at 2mo post presentation

Twenty years ago, the board answer would have been to replace the whole aorta. In young, otherwise healthy man who had been working in road construction up to the dissection, he would have been considered a candidate for a direct open repair of the type II thoracoabdominal aortic aneurysm. From the landmark paper out of Houston by Dr. Svensson in 1993, open type II TAAA repair was associated with about a 10% death rate and 30 percent paralysis rate. Waiting a few months for the aneurysms to grow further in this patient, in the 90’s this patient would probably have ended up with an open TAAA repair. Good thing we have better options.

The goals of modern therapy are to treat the urgent indication while holding off repair of less critical segments of the aorta, and to do so in a way that each operation builds on the previous one.

This patient needed a left subclavian artery debranching and then TEVAR of his dissecting thoracic aortic aneurysm, and intervention on his right renal artery. We did this in one setting performing first a left carotid subclavian artery transposition and then percutaneous TEVAR from the left common carotid artery origin to the supraceliac abdominal aorta.

TEVAR with carotid SCA transposition

completion TEVAR.png

The completion aortography showed good deployment of the CTAG device from the left common carotid artery origin to the celiac axis origin. The false lumen was no longer visualized. The right renal artery which was narrowed was treated with a balloon expandable stent.

The distal thoracic aorta, the true lumen was constrained by a chronic dissection flap. It is here I gently dilate the distal thoracic stent graft with the hopes of eliminating the distal false lumen. This is different from the acute dissection where I rarely balloon.

The TEVAR was done percutaneously, minimizing the overall time in the operating room. The technical details of the transposition can be found in the excellent paper by Dr. Mark Morasch.

 

renal PTAS

When I do this procedure for acute dissection, I quote the patient a general risk of stroke, paralysis of about 2-5% and death of 1-2 percent for someone with low cardiopulmonary risk like this patient had. He recovered rapidly and went home post op day 5.

 

Followup post TEVAR

He at 6 month post TEVAR followup, CTA showed stablility in his thoracic aorta. in infrarenal AAA grew from 5.0 to 5.7cm between the 1 month CT and the 6 month CT.

6 month CTA imaging

The terminus of the stent graft excluded the false lumen in the thoracic aorta but also resulted in filling and pressurization of the false lumen beyond and can be seen as a 44mm lateral dilation of the visceral segment of the aorta which had developed in the 6 month interval since the TEVAR.
The infrarenal neck continued the dissection and had dilated to about 36mm, but was parallel for a good length above the AAA. I decided to treat the inrarenal aorta with direct transabdominal repair. This would allow me to fenestrate the aorta, and possibly prevent further growth of the viseral segment while reserving the retroperitoneum for the visceral segment repair if it came to it. The neck diameter was 36mm.

tube graftHis operation was performed via an anterior approach with the patient supine. A tube graft repair was performed expeditiously and included resecting the dissection flap up to the clamp. Care was taken to avoid injury to the renal stent. The proximal anastomosis went well – the dilated aorta yet had strong tissue strength. A felt strip was used to buttress the aortic side of the anastomosis. The estimated risk of paralysis was less than 1% and risk of death was less than 2%. The patient recovered uneventfully and went home on POD 5.

He did well in subsequent followup, having successfully quit smoking. He retired early on disability and was becoming more active, but the visceral segment dilatation was concerning. At 6 months post infrarenal AAA repair, he underwent CTA and it showed patent thoracic stent graft and infrarenal abdominal graft. The intervening visceral segment continued to enlarge and was now 46mm. The decision was to wait another interval 9 months to see if this would stabilize. The segment grew some more and was 49mm. He wanted to give it another 6 months and at that time, CTA showed further growth over 5cm, and he had developed some abdominal discomfort. He was taken to the operating room.

IMG_8659

A four branch repair of the visceral segment thoracoabdominal aortic aneurysm was performed. The diaphragm was taken down and the stent graft was clamped as was the infrarenal tube graft. A premade Coselli graft was used to bypass to the right renal, SMA, celiac, and left renal in those order. The patient had a CSF drain for the case which was removed on postoperative day 2. He recovered rapidly and went home on postoperative day 6. His estimated risk of paralysis was about 2-5%, mitigated by a protocol centered on CSF drainage and blood pressure control. His risk of death was 5%. Telephone followup reveals the he is pain free at a month out and functional nearly at baseline.

This illustrates the notion that three smaller operations in an aggregate over three years achieved the equivalent of the single big open type II TAAA repair.

equivalence
Illustration on left from Svensson et al.

The idea is to make each step achievable -like coming down a mountain taking three days on well marked paths rather than base jumping off the summit.

Clearly, the patient was younger and a fast healer, and credit must also be given to the anesthesia/critical care team who see high acuity cases in volume every day and not every patient can expect to have such short stays and excellent outcome, but these are far more likely if operations are planned out in such a manner.

Reference

Svensson LG, Crawford ES, Hess KR, Coselli JS, Safi HJ. Experience with 1509 patients undergoing thoracoabdominal aortic operations.  J Vasc Surg 1993;17(2):357-36.

 

Reversing paralysis with a bypass

Dissection CTA

The patient is middle aged and had a type B thoracic aortic dissection (TBAD) as a consequence of recreational substances that acutely raised his blood pressure. At the outside hospital, he had a CTA showing the dissection extending from his left subclavian artery and causing occlusion of his superior mesenteric artery (SMA). He developed abdominal pain and was swiftly transported to our acute aortic syndrome unit. He was taken to the operating room and underwent a TEVAR of the dissection and stenting of his SMA -this is similar to other cases I have discussed in prior posts so I am omitting the technical details. The stent covered the left subclavian artery origin to exclude the origin of the dissection. The stent was extended to the distal thoracic aorta but did not go to the celiac origin. 

TBAD post stent

Post procedure, his lactate never rose and he was maintained on the usual post procedure protocol of keeping MAP’s (mean arterial pressure) above 80mmHg. His left subclavian artery was covered but I do not routinely bypass, especially when the left vertebral artery is at least equal in size to the contralateral one. I don’t often place spinal drains for urgent/emergent cases particularly in patients who have never had infrarenal aortic surgery and patent hypogastric arteries. He was kept sedated overnight and awoke in the morning unable to move his legs to command. He had no pain sensation up to his umbilicus.

A spinal drain was emergently placed and his blood pressure was raised to MAPs of 90+, but these failed to reverse his paralysis. After discussion among my world class partners, I chose to take the patient back for a carotid subclavian bypass which was done through a single incision with a dacron bypass graft.

Carotid subclavian bypass CTA

His paralysis resolved. He was discharged home, ambulating without assistance. Spinal cord complications are reported to occur between 1-5 percent of patients undergoing TEVAR for complicated TBAD. They were seen in 2 of 72 patients in the TEVAR arm of the INSTEAD trial (Circulation, 2009 vol. 120(25) pp. 2519-28), and was permanent in 1. While there are some who routinely place prophylactic drains, it is unclear to me that they have a significant effect if placed unselectively. I will place a Preop drain in the instance of infra renal graft, hypogastric arterial occlusive disease. In the instance of a dominant left vertebral, I will perform concomitant bypass, but just as often not. This is a gratifying and rare outcome of paralysis reversed with a carotid subclavian bypass when spinal drain and permissive hypertension did not. 

Complicated type B thoracic aortic dissections: an explanation of the hemodynamics

sketch1450798979755
A Wind Sock

Type B aortic dissections (TBAD) are frequently seen here at the Clinic as we serve as a regional referral center. As a trainee, I read the chapters discussing all the classifications and discussions of the biomechanics and felt quite intimidated by the all the moving parts involved in an aortic dissection, and I missed the main point about TBAD. Aside from the rupture risk due to the attenuation of the adventitia and hypertension, the acute TBAD is a rapidly developing stenosis of the aorta due to the inflation of a wind sock balloon created by the dissection flap. You can assume any flow that occurs in the false lumen is limited by the area of the proximal tear which is always smaller than the area of the aortic lumen. The true lumen is still perfusing the lower half of the body, and because of the volume filling effect of the flap, flow is restricted. The equivalent physiology is seen in aortic coarctation. Long term, the false lumen behaves like a pseudoaneurysm and may thrombose, continue to grow, or both.

Our group looked at CT’scans on 80 consecutive patients and found that the true lumen to false lumen ratio of less than 0.37 is predictive of the need for intervention.

true lumen false lumen ratio

This makes hemodynamic sense as it approximates the 70% critical stenosis borderline for other arteries. It explains why closing the opening of the dissection, the opening of the wind sock, and expanding the true lumen effectively treats malperfusion.

CTA on transfer 1

This patient whose CTA is shown above was transferred with increasing abdominal pain, inability to control blood pressure, and worsening lactic acidosis.

cta on transfer 2

There was nearly complete obliteration of the true lumen throughout the aorta and occlusion of the left renal artery and dissection into the celiac and superior mesenteric arteries.

pre aortography

Aortography showed the dissection, and absence of visceral vessels from the injection which was from the aortic root. True lumen position was confirmed with IVUS.

Post-Stent aortography

A thoracic stent graft was delivered across the left subclavian artery origin up to the innominate artery origin -the patient had a bovine arch. Immediately, there was filling of the visceral vessels with re-establishment of true lumen flow.

renal stent

The renal occlusion appeared improved but there was still a stenosis due to deflated dissection flap and this was stented (panel right above).

His abdominal pain remitted and his lactate normalized. His creatinine stabilized and has since normalized.

 

lactate
Lactate

Again, if the true-lumen is compressed, the aorta is stenotic because there is a wind sock inflated in it. TEVAR offers a minimally invasive option, frequently percutaneous, for treating this.