There have been vast technological advances that have enabled the final frontier of the aorta, the diseased ascending aorta and arch, to be treated by completely endovascular means. Simultaneously, there have also been advances in open repair. Also, with perioperative stroke remaining a principal risk with TEVAR, the high incidence of cerebral embolisation with the procedure is a problem that needs wider recognition, delegates heard yesterday.
In a panel discussion during the session on interventions for ascending aorta and aortic arch, Roger Greenhalgh, chairman of the CX Organising Board, pressed the panel to comment on patient mortality after open repair and endovascular repair.
The mortality rate for open repair is around 3%, even when there is involvement of the aortic valve, said Stephen Large, Cambridge, UK. With endovascular repair, it approaches 10%, said Dittmar Böckler, Heidelberg, Germany. Subsequently, 65% of the CX 2015 audience voted against the motion that the heyday of open aortic surgery is over.
Richard Gibbs, London, UK, told CX delegates yesterday that there was a high rate of embolisation during arch and descending thoracic intervention that could be observed as silent cerebral infarction on new imaging techniques. The results from the study he presented showed that there is a 70% silent cerebral infarction on MRI and that there is postoperative neurocognitive decline in patients with silent cerebral infarctions.
Gibbs made the point that stroke, which was caused by cerebral embolisation, was a relatively crude surrogate, but a clinically relevant measure of microembolisation. The stroke rate for TEVAR ranges between 3% and 6%, said Gibbs, with embolisation being caused by the passage of stiff wires, soft wires, devices and manipulation within the diseased aorta. The risk factors are the atheromatous burden within the aorta and using a proximal landing zone. Hypotension is also very important, he said.
“A much subtler way of looking at microembolisation is with diffusion-weighted MR that detects acute ischaemia that is due to cerebral oedema. These lesions appear within 24 hours of the insult and last up to 14 days, and show as hyperintense bright areas that are easy to recognise,” Gibbs noted.
Gibbs then showed diffusion-weighted cerebral MR images from a patient who had silent cerebral infarctions but did not develop signs or symptoms of clinical stroke following TEVAR. “Therefore what we see here is silent stroke, or silent cerebral infarction, which is imaging evidence of cerebral infarction, without a history of acute neurological dysfunction attributable to the lesion,” Gibbs said.
He qualified that he believed the term silent cerebral infarction is a misnomer because there is an increasing body of evidence that suggests that silent cerebral infarction is associated with depression, dementia, Alzheimer’s, future increased risk of stroke and mortality.
Published literature shows a significant rate of cerebral infarction with various different interventions involving the arch and unsurprisingly transcatheter aortic valve implantation (TAVI), which is the biggest device and causes the most cerebral infarction, he explained.
“When it comes to TEVAR, there is very little literature, and one paper suggests that there is a 63% risk of cerebral infarction with the procedure,” said Gibbs referring to the data from 19 patients from Kahlert et al published in the Annals of Thoracic Surgery in 2014 that found diffusion-weighted MR evidence of cerebral infarction after TEVAR in 12 of 19 (63%) undergoing the procedure for a variety of indications. There was no overt clinical stroke seen in these patients.
Gibbs then presented the pilot work done by his team on the rates of silent cerebral infarctions during TEVAR, the presence of silent cerebral infarction on MR and whether there are neurocognitive changes afterwords.
“We included 44 patients undergoing TEVAR and looked at the burden of atheroma within the arch of the descending aorta based on the American Heart Association grading method. The patients had bidirectional transcranial Doppler, which is a direct measure of cerebal microembolisation. “A subset of these patients had pre-and postoperative MR looking for more evidence of infarction (23 patients). Another subset had neurocognitive assessment before the intervention, after the intervention in hospital and eight weeks later to see if any changes persist,” said Gibbs.
Forty one TEVAR procedures involving the arch and descending aorta were performed for a variety of pathologies. Of these 21 were standard and 20 were complex involving the use of branches, scallops or adjunctive surgical procedures. “We had fairly proximal landing zones,” he noted.
“Looking at the specific procedural steps, we see clearly that stent graft deployment carries the most significant rate of embolisation,” said Gibbs. He then showed a transcranial Doppler during stent graft deployment where a burst of cerebral embolisation was visible in both hemispheres. “The highest activity of cerebral embolisation was when the device was deployed. Increased embolisation was associated with the left hemisphere more than the right; stent manipulation more than wire and catheter passage; a higher grade of atheroma compared to a lower grade (so a higher burden of disease); chronic rather than acute disease. Patients who had a stroke had the highest rate of embolisation. A proximal landing zone rather than distal one had a higher rate of cerebral embolisation. In the group where we looked for evidence of silent cerebral infarction, 70% (16/23) of our patients had this, mostly in the left hemisphere and mostly in the territory served by the middle cerebral artery. Ten per cent of these patients had a clinical stroke,” said Gibbs.
When the researchers selected out the data for older patients from the group, they found that executive function diminished and stayed down at eight weeks, memory diminished and manual dexterity got worse.
“There is a significantly high rate of cerebral embolisation during TEVAR and the more proximal you go, the worse it is. There is a definitive and radiologically proven damage to the brain and these patients do pay a price for this. We have to be thinking about how we can intervene [either pharmacologically or by using devices],” concluded Gibbs.
Scarcity of literature on proximal landing zone and TEVAR outcomes
Dittmar Böckler stated that while the relationship between the proximal landing zone and outcome was well-documented in the EVAR literature, there were very few publications focused on how the proximal landing zone influences patient outcomes with TEVAR in the arch, and noted the low level of evidence.
“There are no randomised controlled trial data on open versus endovascular approaches and there are no meta-analyses. The data come from limited European registry data from the Relay registry, Traviata registry and European CTAG registry,” he noted.
Böckler drew attention to the fact that there was no consensus in the literature and guidelines on the appropriate proximal neck length and that this variation was reflected in the instructions for use from manufacturers, as the target landing zone is depending on stent graft diameter.
“The appropriate proximal landing zone for TEVAR is not defined. Arch type and atheroma seem to influence stroke risk during TEVAR in the arch. “There is strong need for new refined conformable devices in the arch including branched stent graft technology,” Böckler said.
Value of medication
Frank Lederle, Minneapolis, USA, speaking on the value of medication such as statins before aortic arch catheterisation, stated that there was very little trustworthy randomised controlled trial data to go by. He reviewed evidence that bears on whether perioperative statins or aspirin benefit patients having a thoracic aortic procedure. “Analyses showing benefit of perioperative use rely on weak and doubtful studies. When it comes to aspirin, there are no data on perioperative benefit, but there is an increased major and minor bleeding,” he said.
Lederle drew attention to the fact that many patients with aortic aneurysm have arteriosclerotic cardiovascular disease and should be on statins and aspirin long-term. “There is no good evidence that statins or aspirin improve long-term outcomes for patients with aortic arch patients without arteriosclerotic cardiovascular disease, so some of these patients will not be on these medications. Questions remain on when whether or not patients are on them long-term and whether they should be used perioperatively,” he said.
Stephen Large, Cambridge, UK, a cardiac surgeon, outlined the case for open surgery in interventions for ascending and arch of the aorta, the current gold standard approach.
Large noted that not operating resulted in a “dreadful attrition”. “We know that there is an increase in attrition correlated with the increase in aneurysm size, the hingepoint being around 5.5cm in the ascending and arch, which is associated with an acceleration in terms of stroke, dissection rupture and death,” he said.
“What we very often do in the ascending aorta is deal with an associated post-aortic valvular lesion either by an interposition graft, that is something placed above the coronary artery ostia, really at the level of the sinotubular junction, and right up to the origin of the innominate artery—a true ascending aortic replacement. We can, if we are in trouble (of course with involvement of pathology within the aortic root), replace the aortic root and that always requires reimplantation of the coronary ostia, which brings a raft of problems of threatening ischaemia with it. Up until relatively recently, this involved automatic replacement of the aortic valve. There is now a keen interest in considering valve preservation procedures, something that I have fought against for many years, because the aortic valve is embryologically of the same origin as the ascending aorta. However, counterintuitively, it appears that the aortic valve fares very well. So what to do with the arch? We can replace it with a tube graft and address each of the usual three arch vessels. Or we can translocate the whole of the aortic arch vessels permitting the use of either replacement or stenting. As cardiac surgeons, we find ourselves replacing the ascending aorta in an emergency as a life-saving procedure for dissection. We, of course, will look at ascending aortic aneurysms for elective surgery for prognostic issues and this is often in conjunction with other procedures in the chest such as aortic valve replacement,” he said.
Endovascular procedures a valid alternative in selected patients
Piergiorgio Cao, Rome, Italy, speaking on branched stent grafts for the treatment of complex arch lesions, said that any repair of aortic arch remains demanding and exposes patients to mortality and stroke risks that are “not negligible”. Open repair is the gold standard, and hybrid and endovascular repair are valid alternatives, mostly in patients who are at high risk for surgery, he noted.
Cao defined the morphological feasibility to receive endovascular treatment as the presence of a proximal landing ≥2cm in length and ≤4.2cm in diameter. The challenges for TEVAR in the arch include conformability of the stent graft, endoleak and retrograde dissection occurence, he said.
He then alluded to a recent publication in the Journal of Vascular Surgery from Paola De Rango et al that analysed total aortic arch reconstruction in a contemporary comparison of current open and endovascular repair.
De Rango et al entered endovascular and open arch procedures performed from 2007 to 2013 into a prospective database and then retrospectively analysed the data. Endovascular repair (proximal landing zones 0-1), with or without a hybrid adjunct, was selected for patients who were sicker but who had a fit anatomy. Operations involving coverage of left subclavian artery only (zone 2 proximal landing) and open hemiarch replacement were excluded.
As reported in the journal, the authors concluded that despite the older age and a higher comorbidity profile in patients with challenging aortic arch disease who were suitable and selected for endovascular arch repair, no significant differences were detected in perioperative and four-year outcomes compared with the younger patients undergoing open arch total repair.
Yesterday, Cao concluded by saying: “The endovascular approach is a valid alternative to open surgery for all patients, when morphologically feasible. A safer proximal landing zone with longer coverage of the ascending aorta may be the key for long-term durability and to prevent retrograde dissection. Branched stent grafts might be useful in avoiding arch manipulations and decreasing the risk of major adverse events,” he said.
Greenhalgh then commented that the audience might like to have some idea of the expected mortality associated with both the open and endovascular methods in the case of a 70-year-old patient with an ascending dilating disease process in which the valve becomes incompetent. Mortality is 3% with open repair and 10% with endovascular repair, the audience learned.
He further commented on the resurgence of the classification of aneurysmal disease: “The starting point seems to be aneurysmal disease. We are seeing comments on syphilitic, fusiform and saccular aneurysms and this is beginning to look like an old surgical textbook, he commented.
In a debate, Hans-Henning Eckstein, Munich, Germany, argued against the motion “The heyday of open aortic surgery is over” to garner majority support that open repair still had a valid place in the treatment of the ascending aorta and aortic arch. He persuaded 65% of the delegates to vote against the motion. Frank Veith, New York, USA, spoke for the motion.