TAVI Stroke Risk
Transcatheter aortic valve implantation (TAVI) is rapidly is rapidly emerging as a potential therapeutic option for patients with severe symptomatic aortic stenois. The clinical outcome data coming out of trials is making routine headlines with regards to patients with aortic valve disease who are not surgical candidates (PARTNER B study) and for those patients as an alternative to surgery (PARTNER A study). Though the clinical benefit of TAVI in PARTNER A was non-inferior to surgical aortic valve replacement, an unquestionably impressive performance, the associated stroke risk has caught the attention of the cardiovascular community, as highlighted by the data presented at the American Association for Thoracic Surgery national meeting. The 30 day rate of stroke and TIA was 2.6% in the surgical arm and 5.6% with TAVI (p=0.05), however in the transfemoral eligible group the stroke and TIA rates were 1.4% and 4.6% with surgery and TAVI respectively, p=0.04. As 69% of all neurological events in the TAVI group and 25% in the surgical groups were TIA, 30 day major stroke rates overall were 2.3% with surgery versus 3.8% with TAVI (p=0.25); whereas for the transfemoral eligible group it was 1.4% (surgery) and 2.5% (TAVI), (p=0.37).
What causes these strokes? MRI studies show multifocal areas of cerebral infarction, suggesting embolization. The following are considered to play a role:
(1) Embolization from the valve, during balloon valvuloplasty and valve deployment
(2) Embolization of aortic atheroma during device passage
(3) Air embolism (given placement of a large caliber (26F) catheter in the left ventricular cavity over a prolonged period and multiple wire, catheter and device exchanges and repeated flushing)
(4) Hypotension, during valve deployment especially in patients with carotid disease could contribute towards this risk.
Importantly, presence of atrial fibrillation was not an independent predictor of stroke in these patients. Review of the transesophageal images obtained during TAVI and surgical valve replacement could provide useful clues.
I would like to invite all to a thorough multi-specialty, multi-dimensional discussion leading us towards a better understanding and possible solutions to this problem. My own perspective is not to write it off exclusively related to the atherosclerotic disease burden of this patient group and bury the problem as a mere cost for engaging in the business of TAVI. I am confident that like many such challenges in the past the collaborative approach of cardiologists, cardiac surgeons, vascular, imaging specialists and neurologists can pinpoint the leading predictors of stroke during TAVI and work out specific solutions.
