An oldie but a goodie from my first blog, “The Pipes Are Calling” on Medscape. This case came to mind when I recently diagnosed a pheochromacytoma from my clinic -middle aged man with difficult to control hypertension and unilateral renal artery stenosis. One of the most critical lessons learned from medical school, the Columbia University College of Physicians and Surgeons, was to be a complete physician, to be curious and engaged in the well being of your patient even outside the narrow focus of your specialty. This I learned especially from people like Drs. Harold Neu and Mark Hardy.
W. Michael Park, MD, Surgery, Vascular, 05:24PM Jun 23, 2010
The patient is a middle aged man who developed rest pain of his left leg after CABG for 3VCAD/MI. Workup revealed an occluded left iliac arterial system with diffuse atherosclerosis of his aorta and iliac arteries. He had a long history of bilateral calf claudication and his right SFA was occluded and his left SFA was diffusely diseased. CTA was performed and showed the described anatomy
And a “2.2cm peripherally enhancing mass” probably representing a lymph node with central necrosis, adjacent to the aorta.
I proceeded with aorto-right iliac and left femoral bypass, planning on later leg revascularization as needed after establishing inflow. During the retroperitoneal dissection over the aorta, I ran into this purplish mass and on manipulation, the patient’s blood pressure shot to 210mmHg. As my brain processed, my resident who had just finished reading his chapter on endocrine, said, “this could be a pheochromocytoma.”
That tumor was out quicker than you could say “snit.” Frozen section, and later final pathology returned paraganglionoma.
The patient recovered well and graciously gave permission, as all my patients here do, to allow this to be discussed. He noted that hypertension kept him out of Vietnam. Records showed an uneventful CABG.
Applying the retrospectocsope, I will now be far more wary of midline retroperitoneal lesions that are highly vascularizad.
I recently had to remove a stent graft for infection and got to thinking about how the number of people who could comfortably and confidently manage that has thinned out in the world through the unintended consequence of the medical device market place. In every surgical specialty over the past twenty years, many open procedures were replaced with a minimally invasive option which generally involved adoption of new technology and large costs to the hospital. These newer procedures were touted as easier on the patient while being easier to perform for the average physician than the open procedure that they were replacing. That was the other selling point -that one could do several of these operations in the time it took one open procedure. In most cases, they were at best almost as good as the open procedure but at higher cost.
In the marketplace, minimally invasive always wins. In many specialties it became untenable to practice without marketing these “advanced minimally invasive” skills. Hence, the wide adoption of robotics in urology outside major academic centers -during those years of rapid adoption the surgeons would get flown to a course, work on an animal model, then for their first case a proctor would be flown out and voila -a minimally invasive specialist is born. The problem comes when learning these skills displaces the learning of traditional open surgical skills. In general surgery, it is not uncommon to hear of residents graduating without having ever having done an open cholecystectomy. It is also the case that many vascular trainees graduate with but a few if any open aortic cases. What happens when minimally invasive options run out? Who will do my carotid endarterectomy or open AAA repair?
The first case is an elderly man with an enlarging AAA sac despite having had EVAR about seven years prior. No endoleak was demonstrated but the proximal seal was short on CT. Also, it was a first generation graft which is prone to “peek a boo” endoleaks from graft junctions and stent anchoring sutures. On that last point, I use the analogy of a patio umbrella -after seven seasons, they can leak where cloth is sewn to the metal struts. It is very hard to demonstrate leak of this kind on CTA or duplex ultrasound because they are small. The patient had his EVAR because he was considered high risk for open repair at the time of his operation -moderate COPD, mild cardiac dysfunction. His sac had enlarged to over 6cm in a short time, and therefore open conversion was undertaken. No clinical signs of infection were present. A retroperitoneal approach was undertaken. After clamps were positioned, the sac was opened.
The picture does not show it, but a leak from the posterior proximal seal zone was seen with clamp off. The clamp was reapplied and the graft transected flush to the aortic neck. A bifurcated graft was sewn to this neck incorporating the main body stent graft and aortic neck in a generous running suture. The left iliac limb came out well and the new graft limb sewn to the iliac orifice, the right iliac limb was harder to clamp and therefore I clamped the stent graft and sewed the open graft to the stent graft.
The patient recovered well and went home within the week. He was relieved at no longer needing annual CT scans.
Who needs annual CT scans? Patients with metastatic cancer in remission.
The second patient was an older man referred for enlarging AAA sac without visible endoleak. The aneurysm had grown over 7cm and was causing discomfort with bending forward. He too had been deemed high risk for open repair prior to his EVAR. If he had had an early generation Excluder graft, the possibility of ultrafiltration would be more likely and relining the graft would be reasonable (link). This was again a cloth and metal stent graft which can develop intermittent bleeding from graft to stent sutures, and I don’t think relining will help.
The patient was taken for open repair (above), and on opening the AAA sac, bleeding could be seen coming from the flow divider. It stopped with pressure, but I replaced the graft in a limited fashion from the neck to the iliac limbs as in the first case. This patient did very well and was discharged home under a week.
The third patient was another fellow referred from outside who had an EVAR for a very short and angulated neck, and a secondary procedure with an aortic extension in an attempt to seal the leak had been done. This failed to seal the type Ia leak. This patient too was deemed too high risk for open surgery of what was basically a juxtarenal AAA with very tortuous anatomy.
The patient was taken for open repair, and the stent grafts slid out easily (below).
A tube graft was sewn to the short aortic neck and distally anastomosed to the main body of the stent graft -with pledgets because of the thin PTFE graft material in this particular graft. This patient did well and went home within a week.
All three cases are patients who were deemed originally too high risk for open repair, who underwent EVAR, then underwent explantation of their failing stent graft. Only one involved a patient whose graft was placed off the IFU (short angled neck), but the rationale was that he was too high risk.
What is high risk? In non-ruptured, non-infected explantation of failing stent graft, the mortality is 3% (ref 2) from an earlier series from Cleveland Clinic. With stent graft infection, the 30-day mortality of surgical management from a multi-institutional series was 11% (ref 3) when there was no rupture. From a Mayo Clinic series, stent graft resection for infection came with a 4% 30-day mortality (ref 4). These were nominally all high risk patients at the time of the original EVAR.
Real world risk is a range at the intersection of patient risk and the expertise of the operating room, critical care, and hospital floor teams. The constant factor is the surgeon.
Endografts for AAA disease (EVAR, endovascular aortic aneurysm repair), makes simple work of a traditionally complex operation, the open aortic aneurysm repair. The issue has been the cost and risks of long term followup as well as endograft failure and aneurysm rupture. The Instructions For Use on these devices recommend a preop, a followup 1 month, 6 month, and 12 month CTA (with contrast) and annual followup with CTA for life. These devices were meant to treat high risk patients but high risk patients with limited life spans do not benefit from EVAR (ref 1, EVAR-2 Trial). These have lead the NHS in the UK to propose that EVAR has no role in the elective repair of abdominal aortic aneurysms in their draft proposal for the NICE guidelines for management of AAA (link). While this is a critical discussion, it is a discussion that is coming at least ten years too late. A generation of surgeons have been brought up with endovascular repair, and to suddenly announce that they must become DeBakey’s, Wiley’s, Imperato’s, and Rutherford’s is wishful thinking at best or wilful rationing of services at worst.
In 2006, Guidant pacemakers were recalled because of a 1000 cases of possible capacitor failure out of 28,000 implants for a failure rate of 3.7% -there were 2 deaths for a fatality rate of 0.00007%. EVAR-1 Trial’s 8 year result (ref 5) reported 16 aneurysm related deaths out of 339 patients (1.3%) in the EVAR group compared to 3 aneurysm related deaths out of 333 patients (0.2%) in the OPEN group.
Academic medical centers, behemoths though they are, serve a critical function in that they are critical repositories of human capital. The elders of vascular surgery, that first and second generation of surgeons who trained and received board certification, are still there and serving a vital role in preserving open aortic surgery. My generation -the ones who trained in both open and endovascular, are still here, but market forces have pushed many of my colleagues into becoming pure endovascularists. The younger generation recognizes this and last year, I sat in on an open surgical technique course at the ESVS meeting in Lyons organized by Dr. Fernando Gallardo and colleagues. It was fully attended and wonderfully proctored by master surgeons. This is of critical importance and not a trivial matter. As in the 2000’s when endovascular training was offered as a postgraduate fellowship in centers of excellence, there is no doubt in my mind that today, exovascular fellowships need to be considered and planned and that current training must reinvigorate and reincorporate their open surgical components.
Leriche Syndrome -one of those disease names that adds to our work in a way that an ICD codes and even the “aortoiliac occlusive disease” fails to describe. When I hear someone described as having Leriche Syndrome, I think about a sad, chain smoking man, unmanned, complaining of legs that cramp up at fifty feet, pulseless.
The CT scan will occasionally show an aorta ringed by calcium in the usual places that are targetrs for clamping below and above the level of the renal arteries. Even without the circumferential calcium, a bulky posterior plaque presages the inability to safely clamp the aorta. Woe to the surgeon who blithely clamps a calcified lesion and finds that the rocky fragments have broken the aorta underneath the clamp! The first way to deal with this is to look for ways not to clamp the aorta, by planning an endovascular procedure, but circumstances may necessitate the need to control the aorta despite the unclampability.
The traditional methods of avoiding clamping the calcifed peri-renal aorta are extra-anatomic bypasses including femorofemoral bypass and axillo-femoral bypass. I propose these following options for the consideration when the patient needs a more durable solution while avoiding a heavily diseased aorta.
Not Clamping I:
EndoABF does work to avoid clamping -these are common femoral endarterectomies supplemented by stenting of the aortoiliac segment, including in those with appropriate anatomy, a bifurcated aortic stent graft. This is often not possible to treat both sides, but one side is usually more accessible. Often, people will compromise and perform an AUI-FEM-FEM, but I have found the fem-fem bypass to be the weak link, as you are drawing flow for the lower half of the body through a diseased external iliac artery. The orientation of the proximal anastomosis is unfavorable and in the instance of highly laminar or organized flow, the bypass is vulnerable to competitive flow on the target leg, leading to thrombosis.
The femorofemoral bypass is the option of patients whose options have largely run out. It is made worse when fed by an axillofemoral bypass. Sometimes, you have no choice, but in the more elective circumstance, you do.
Not Clamping II:
The second method is performing a aorto-uni-iliac stent graft into a conduit sewn end to end to the common iliac aftery, oversewing the distal iliac bifurcation.
The conduit is 12mm in diameter, the key is to deliver the stent graft across the anastomosis, sealing it. The conduit is then sewn to the side of a fem-fem bypass in the pelvis, maintaining antegrade flow to both legs. The other option is to sew the conduit to a 14×7 bifurcated graft. Illustrated above is this 12mm conduit sewn end to end to the diseased common iliac artery with wire access into the aorta and a aorto-uni-iliac device. Typically, a small AUI converter (Cook, Medtronic) can be used, but the aorta is often too small even for a 24mm device, and an iliac limb with a generous sized docking segment (Gore) ending in a 12mm diameter fits nicely. Below is a CTA from such a case, where the stent graft is deployed across the anastomosis, sealing it off from anastomotic leaks (exoleaks).
Not Clamping III:
Often, the infrarenal aorta is soft anteriorly and affected only by posterior plaque at the level of the renal arteries. While a clamp is still not entirely safe (I prefer clamping transversely in the same orientation as the plaque with a DeBakey sidewinder clamp), a balloon is possible. I do this by nicking the aorta -simple application of a finger is sufficient to stop the bleeding if you have ever poked the ascending aorta to place cardioplegia line.
A Foley catheter is inserted and inflated. The Foley’s are more durable and resist puncture better than a large Fogarty. This is usually sufficient for control, although supraceliac control prior to doing this step is advised. The aorta can be endarterectomized and sewn to the graft quite easily with this non-clamp.
This has worked well, Although pictured above with an end-to end anastomosis planned, it works just as well end-to-side. I actually prefer end to side whenever possible because it preserves the occluded native vessels for future intervention in line.
The Non-Thoraco-Bi-Femoral Bypass
The typical board answer for the non-clampable aorta is taking the inflow from the thoracic aorta or from the axillary artery -neither of which are good options. The first because the patient is positioned in right lateral decubitus and tunneling is not trivial. The second because of long term durability. The supraceliac aorta, technically it is the thoracic aorta, is often spared from severe plaque and clampable. Retropancreatic tunelling is straightforward, and a 12 or 14mm straight graft can be tunelled in this fashion from the lesser sac to the infrarenal retroperitoneum. It then sewn to the supraceliac aorta and then anastomosed to a 12x6mm or 14x7mm bifurcated aorto-bifemoral bypass, of which limbs are tunneled to the groins.
This worked very well recently, allowing a middle aged patient with severe medical problems, occluded aorta and iliac arteries, with critical limb ischemia, survive with minimal blood loss and home under 5 days. It delivers excellent flow to both legs in an antegrade fashion. Dr. Lew Schwartz gave me a list of references showing that this is not novel, but represents a rediscovery as the papers were published in the 80’s [reference], and buttresses the principle that innovations in open vascular surgery are exceedingly rare, largely because we have been preceeded by smart people.
Conclusion: All of these come about through application of some common sense and surgical principles. The most important this is that the aorta is the best inflow source and reconstructing it with the normal forward flow of down each leg and not reversing directions as in a fem-fem bypass gives each of these options a hemodynamic advantage.
References for Supraceliac Aorta to Lower Extremity Bypass
Surgery [Surgery] 1987 Mar; Vol. 101 (3), pp. 323-8.
Patient is a 77 year old man with history of HTN, hyperlipidemia, former smoking, and CAD with CABGx5 and bilateral lower extremity bypasses who developed unstable angina consisting of neck and throat pain. He underwent catheterization at an outside hospital and found to have 100% LAD occlusion, a diseased, small patent left main and left circumflex (the profunda femoral artery of the heart!), 100% RCA occlusion, a patent but diseased SVG to distal RCA, and a patent LIMA graft to distal LAD but with severe plaque and near occlusion of his proximal left subclavian artery.
He had an NSTEMI. His vitals signs stabilized in the coronary care unit and he was sent to a telemetry floor. Whenever he walked, he would get the jaw pain, and this would also occur sporadically while recumbent.
On examination, he had no left brachial pulse, only a monophonic signal there, and bounding femoral pulses where there were the origins of bilateral femoral-tibial bypasses. His radial artery pulse was diminished on the right and absent on the left. Both saphenous veins had been harvested as were arm veins for the left leg bypass.
CTA shows the left subclavian artery to be occluded at its origin.
Cardiac surgery, interventional cardiology, and vascular surgery were called in for consultation. Cardiology consultation (Drs. Kapadia and Shisheboor) felt, and I agreed, that the left subclavian lesion was a poor candidate for recanalization and stenting. CT Surgery (Dr. Faisal Bakaeen) and I had a long discussion regarding alternate conduits, as he had unknown radial but likely radial artery disease, and had all usable veins previously harvested. I brought up a free RIMA graft -I had worked with Dr. Daniel Swistel, in NYC as a resident, who was Dr. George Green’s protege, and as a medical student at P&S I scrubbed Dr. Green’s final cardiac case. He routinely performed bilateral ITA bypasses decades before all-arterial revascularizations were routine. I get enthusiastic talking about cardiac disease! Walking through all the options -does anyone use deep femoral vein as coronary bypass conduit -we agreed ultimately that the best option would be a carotid-subclavian bypass with plenty of backup.
At its heart, it would be this vascular surgeon’s attempt at an off-pump single vessel CABG (above). Preparations were made with cardiac anesthesia and cardiac surgery to place an IABP (intra-aortic balloon pump) if he became unstable. For my part, the operation was straightforward, but I was going to have to go about it efficiently. I also figured that with a clamp beyond the LIMA takeoff, no significant change would occur to the coronary flow from the LIMA graft. So I hoped as I worked very deliberately. We kept him on the hypertensive side during the case.
The operation went well. The patient’s angina resolved and a followup CT showed the patent bypass feeding the LIMA and LAD.
His resting angina resolved. He followed up a month later and was very pleased. Moreover, he had a brachial and radial artery pulse and a general weakness of the left arm that he never complained about before lifted.
The carotid subclavian bypass is something that really needs to be in the armamentarium of a modern vascular surgeon. Though out of print, Wylie’s Atlas (the unabridged, multivolume version) is available used through online sellers, and is useful for elucidating the anatomy which boils down to avoiding cutting the important structures -the phrenic nerve, the vagus nerve, the brachial plexus, branches of the subclavian including the vertebral artery, while cutting away muscles -lateral head of sternocleidomastoid, any part of the omohyoid, the anterior scalene muscle. And dividing the lymphatic duct if encountered. And tunneling under the jugular vein. And minding the buttery fragility of the SCA. The best technical paper out there is by Dr. Mark Morasch and it mostly deals with carotid-subclavian transposition (reference 1) but has excellent figures on bypass as well. I do both transposition and bypass, but for brevity, I prefer bypass.
This is not a unique problem, having been reported in the literature. An unusual variant of this is coronary sbuclavian steal syndrome (reference 2), which refers to reversal of flow in the LIMA bypass in the setting of subclavian artery occlusion and left arm exertion -which was not the case here, but interesting enough to mention. Here, it was a straightforward case of managing the hemodynamics. The key point of operating on such a patient was having the surety of quick response in the case of ischemic heart failure -we operated in the cardiovascular operating rooms with rows of perfusion pumps and balloon pumps and VADs and ECMOs at the ready. Indeed, this result could not have been so straightforward and routine seeming without the combined effort and experience of the whole Heart and Vascular Institute from nursing to consultant staff.
Morasch MD. Technique for subclavian to carotid transposition, tips, and tricks. J Vasc Surg 2009;49:251-4.
Cua B et al. Review of coronary subclavian steal syndrome. J Cardiol. 2017 Apr 14. pii: S0914-5087(17)30090-4. doi: 10.1016/j.jjcc.2017.02.012. [Epub ahead of print]
The development of metachronous common iliac artery aneurysm, or progression of them, after prior treatment with EVAR (endovascular aneurysm repair), particularly with “bell bottoming” is typically treated with coil embolization of the internal iliac artery and extension of the stent graft into the external iliac artery. While CH-EVAR has been in the news with the recent results from the PERICLES registry, I have never been entirely convinced of its durability. That is different in the case of building parallel grafts in an iliac limb of an EVAR graft (reference).
Here, the geometries, thrombosis, and forces combine to make gutter flow and endoleak unlikely. Choosing the right size of stent grafts to channel to the external and internal iliacs seems to be a challenge, but is easily solved by this scheme -which I can’t claim as my own, but was thought up by a surgeon in upstate New York who choses to remain anonymous.*
The diameter of the stent graft to be sealed to is measured and an area calculated. The sum of the areas of the two grafts to be placed need to equal or slightly exceed the area of this inflow stent graft. If you have decided the size of the external iliac graft, for example, then the diameter of other graft is merely a few geometric formulas away.
Here is a table that can be helpful in avoiding those formulas.
The inflow graft area is taken from its measured diameter. Then usually one or the other artery has an obligate size -a size the graft has to be while the other has more “wiggle room.” The other thing that comes from experience is that the AFX graft’s iliac limb extension don’t get the B-infolding that can affect an oversized stent graft placed in a small artery and it accomodates a neighbor well.
For example, take this patient who after EVAR of aortic aneurysm with AFX developed metachronous dilatation of the common iliac artery to 3.9cm with abdominal pain. The average diameter is 18.5mm. From the table, that rounds to 19mm corresponding to 283.53 square mm. If the internal iliac artery requires a 13mm graft, that is 132.73 square mm, the difference being 150.80 square mm. That corresponds to a 14mm diameter graft, but a slightly larger graft is preferred for oversizing. The external iliac artery is 8mm, and putting a 13mm Viabahn (largest available) in that would result in the B-infolding in the 8mm external iliac. Here, I bailed myself out by simply placing a 20mm AFX iliac limb extension, which by virtue of its design is resistent to infolding and tolerant of parallel grafts laid alongside in constricted channels. I found that the AFX iliac limb, a 20-13mm x 88mm length extension well suited for this.
The AFX graft limb seems to adapt to the presence of the parallel “sandwich” graft which is deployed second and ballooned last. In followup, there was shrinkage of the common iliac artery aneurysm sac and no endoleak.
Compared to my other parallel graft case treating a metachronous saccular common iliac aneurysm years after an EVAR with a Gore endograft (link), which by table calculation, resulted in 8% oversize in calculated areas, this particular technique with a large AFX graft and an appropriately sized Viabahn seemed to work well the setting of a previously placed AFX graft. It allows one to avoid hypogastric occlusion.
The final option of a femoral or external iliac to internal iliac bypass after extension across the bifurcation to the external iliac artery is still a reasonable choice, although it seems to be receding into history.
Smith, Mitchell T. et al. “Preservation of Internal Iliac Arterial Flow during Endovascular Aortic Aneurysm Repair Using the ‘Sandwich’ Technique.” Seminars in Interventional Radiology 30.1 (2013): 82–86. PMC. Web. 9 Dec. 2016.
*While these grafts are not FDA approved for use in this manner, many times, with a prior endograft or graft in place, using the currently available and approved Gore Iliac Branch Endoprosthesis (IBE) in this common scenario would still be off label usage of an approved device, and only if it is feasible, which most times is not. For nonmedical readers, many commonly available devices and medications are used off-label, such as aspirin for blood thinning.
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.
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.
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.
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.
Patient is a middle aged man with history of DVT and PE who in preoperative workup for another operation was found to have a popliteal venous aneurysm affecting his right leg. Unlike the recently posted case (link) which was fusiform, this aneurysm was saccular (CT above, duplex below). Popliteal venous aneurysms have a high risk of pulmonary embolism because: they tend to form clot in areas of sluggish flow and once loaded with clot, will eject it when compressed during knee flexion.
When I perform open vascular surgery, I tend to get a CTA not just because it is minimally invasive and convenient, but because it gives important information for operative planning. The volume rendering function, which takes the 3 dimensional data set from a spiral CT scan, and creates voxels (3 dimensional pixels) of density information and creates stunning images such as the one featured on the current September 2016 issue of the Journal of Vascular Surgery. But these are not just pretty pictures.
In fact, I use these images to plan open surgery, even to the location of incisions. Vital structures are seen in 3D and injuries are avoided. Take for example the CT Venogram on the panel below. By adjusting the window level, you have first the venographic information showing the saccular popliteal venous aneurysm on the left panel, you can also see where it is in reference to the muscles in the popliteal fossa. The greater saphenous vein and varicose veins below are well seen.
By adjusting the level, subcutaneous structures are better seen including the small saphenous vein which could be harvested to create a patch or a panel graft from a posterior approach. A final adjustment of the window level on the right shows the skin, and I can now plan the curvilinear incision.
By changing the orientation, I can also recreate the surgeon’s eye view of the leg in the prone position (below).
And you can see how well it matches up to the actual operation shown below:
This was treated with plication of the saccular aneurysm and unlike the fusiform aneurysm, I did not sew over a mandrill (a large 24F foley) inserted through a transverse venotomy, but rather ran a Blalock type stitch under and over a clamp.
The several weeks postoperatively showed no further trace of the saccular aneurysm.
The volume rendering software grew out of the 3D gaming industry. The voxel data that paints flesh and bone on skeletons and costumes and weapons is far more complex than what is applied for the 3DVR packages that are available. The images shown for this post comes from TeraRecon/Aquarius, but they are also available as open source software from Osirix, Vitrea, and various software packages sold with CT scanners. While those that are tied to the scanners are often tied to dedicated workstations -limiting you to going to Radiology and taking over their workstation, many will work in the cloud for both the DICOM data and for virtual desktop access through mobile. Contrast is not necessary if the patient has kidney dysfunction -the vessels can be manually centerlined -ie. a line can be dropped in the center of the artery to illustrate its course when viewing the VR images.
I will plan the surgery while in the clinic with the patient, actually tracing out the incisions and dissections necessary to achieve success. It is a wonderful teaching tool for trainees. But most critically, it helps me imagine the operation and its successful completion.