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