A basic recipe for treating complicated aortic dissection
#aorticsurgery #tevar
Category: aortic dissection
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.
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.
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.
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.
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.
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:
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.
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.
- 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.
- 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.
- 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.
I was invited by Dr. Martin Maresch to speak on complicated type B aortic dissections. Should be an exciting day.
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.
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.
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.
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.
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.
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.
His 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 9Â 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.
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.
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.
I recently repaired a traumatic aortic dissection and was struck by how far along things had progressed since I was a resident. I remember seeing a Q&A in the mid nineties where Dr. Mattox expounded on the gold standard for diagnosing traumatic aortic injuries which at that time was contrast aortography. This caused many struggles trying to arrange for arteriography in the middle of the night (these accidents usually occur then). The repairs were open and very morbid for severely injured patients, particularly those with closed head injuries and fractures. This all changed in the early 2000’s as I had mentioned in an earlier post (link). The grafts were homemade (figure)
and this was literal -the picture is from my kitchen back in the Bronx in 2004. The grafts were cumbersome to deploy and required long 24-28F sheaths that frequently required iliac and aortic exposures.
The revolutionary breakthrough was the fact that thoracotomy and partial cardiac bypass could be avoided. Durability was largely assumed as these patients rarely came back for followup.
Fastforward to 2015. CTA is done with 64 slice CT scanner with EKG and respiratory gating eliminating the artifacts that caused Dr. Mattox to assert that aortography was the gold standard. Software based image reconstruction can aid treatment planning in ways that greatly exceed the caliper and ruler methods we had in 2004.
The grafts are currently into their second generation of development and have small profile and trackability that allows for percutaneous delivery and treatment.
The aortogram shows the tear along the inner curve. These lesions typically require coverage either partial or total of the left subclavian artery origin. This patient had a dominant right vertebral artery and I felt he would tolerate even full coverage of the left subclavian.
The device, a Gore C-TAG device which has an FDA trauma indication, is clearly better than our homemade device. Deployment does not require pharmacologic or electrical bradycardia or asystole.
The idea behind this design is conformability of the smaller stent elements. The aortic injury is even outlined by the stents in the aortogram above. The bird-beaking that was common to the prior generation of graft is not seen in this aortogram.
Where does this need to go next? At 18-24F access requirements need to become 12-18F and for the same reason, the grafts need to be available down to 14-18mm as trauma doesn’t just happen in middle aged men. Aside from that, it is a definite improvement over what we had in 1995 and in 2004.
The figure above shows the summarizes the problem that brought the patient to his local hospital and triggered his transfer to our acute aortic syndrome unit. The concept is that all chest pain of cardiovascular origin gets intake through a vast intensive care unit staffed by cardiovascular intensivists. Stabilization, workup, transfer to operating room or interventional suite all happens in an ICU that encompasses almost a city block.
The patient is an older middle aged man with sudden onset of back and abdominal pain. He was on coumadin for a prior SMV thrombosis and treatment for a ruptured appendicitis -antibiotics with plan for staged appendectomy. CT at his local hospital revealed a type B aortic dissection (TBAD) that extended into his superior mesenteric artery.
The dissection started at the left subclavian artery origin. The false lumen compressed the true lumen up at the proximal descending thoracic aorta. This is an important finding because in this configuration with much of the filling of the dissection from the distal reentry sites, the false lumen acts like a pressurized, compressive lesion. With time, the adventitia around the false lumen may become aneurysmal if the false lumen fails to thrombose or obliterate. When the dissection is acute, the flap may cause a direct obstruction to flow or a dynamic one that depends on the pressure difference between true and false lumen.
In this patient, thrombosis occured in the SMA beyond the origin due to dissection and decreased flow. This was consistent with the patient’s complaint of generalized abdominal pain and examination findings of pain out of proportion to the exam, indicating acute mesenteric ischemia.
His laboratory findings were within normal ranges, indicating this was early in the process. It is important to remember that no lab value correlates with acute mesenteric ischemia except very late in the process, and acute mesenteric ischemia remains a clinical diagnosis (reference 1) that is associated with a high mortality rate.
He was taken to the hybrid operating room. Right groin access was achieved and wire access to the arch was achieved. IVUS (Intravascular ultrasound, Volcano) was used to confirm the location of the wire -I believe this is an important adjunct as simply passing the wire doesn’t guarantee travel up the true lumen.
Wire access was achieved across the thrombus. At this point, I had a range of options for thrombectomy including simply aspirating which retracting a catheter. This was not optimal as I could lose subsequent wire access or reenter the false lumen. The other option was an open thrombectomy and patch angioplasty -the thighs were prepped in case we had to harvest vein. Again, in the setting of dissection and going into the mesentery, an open revascularization while feasible, is challenging.
Thrombectomy catheters like Angiojet were available, but I chose to try the Export aspiration catheter (Medtronic). It is simple to set up and goes over a 0.14 wire. It is designed for the coronaries which have a similar lumenal diameter as the SMA. It worked well in this setting in retrieving thrombus which had a pale element that may have indicated some chronicity.
The completion arteriogram was satisfying.
The SMA completely filled as did the celiac axis and both renal arteries. I opted not to treat the right renal artery as we had given 250mL of contrast, and it was filling well without intervention. The patient was making excellent urine and his blood pressure had been maintained with mean arterial pressures above 70mmHg. At this point, IVUS confirmed good deployment of the stent.
The sheath was removed and the access site repaired. The general surgeons explored the patient and found all the bowel to be well perfused with pulsatile flows seen in the mesenteric arcade. The appendix was removed.
On waking, the patient was noted to not move his legs. A spinal drain was expertly placed by our cardiac anesthesia staff and his blood pressure was raised to MAP’s above 80. He recovered motor function in his legs soon after. I usually don’t place preop CSF drains in this scenario in the presence of good pelvic circulation, no history of infrarenal aortic interventions, and patency of the left subclavian artery. That said, with TEVAR of TBAD, there is a small incidence of paraplegia (1-5%) which I emphasize in my preoperative discussion.
He was started on heparin anticoagulation postop because of his history of SMV and now SMA thrombosis, interrupting it briefly to remove the CSF drain. A CTA was obtained to confirm absence of bleeding showing obliteration of the dissection in the aorta and good patency through the true lumen of the SMA.
Most importantly, he had complete relief of his abdominal pain.
The treatment of acute mesenteric ischemia has greatly evolved since I presented my paper in 2002. While open revascularization remains a gold standard, it is becoming increasingly apparent that good to better results may be obtained with an endovascular approach. Dan Clair, our chair, has made the comment that early revascularization with endovascular technique is analogous to emergent PTCA in occlusions of the coronary system and that re-establishing flow is a critical first step.
Open exploration still is the mainstay of managing acute mesenteric ischemia, but laparoscopic exploration remains feasible. This patient underwent open conversion after an initial laparoscopic exploration to remove a ruptured retrocecal appendix that had been treated for over a month on antibiotics. Without bowel necrosis, a second look is usually unnecessary, but is critical when threatened bowel is left behind.
Reference
- Park WM et al. J Vasc Surg. 2002 Mar;35(3):445-52.
A Surgeon's Notes 