Transcatheter aortic valve implantation (TAVI) is known to carry a relatively high stroke risk, at least in part related to embolisation from the valve and aorta. The number of emboli can be measured using Transcranial Doppler (TCD), but this picks up both solid and gaseous emboli, whereas neurological outcomes are more likely to be related to solid emboli based on previous surgical studies. No previous studies have been done which differentiated solid from gaseous emboli in TAVI patients. We aimed to use software to differentiate solid from gaseous emboli and see at which time points solid emboli in particular were generated. This could help with the design of neuroprotective devices for TAVI.Methods
We prospectively enrolled consecutive TAVI patients and used TCD to record emboli from May 2012 to October 2013, where suitable unilateral or bilateral TCD windows were obtained. We used QLab 10.0 software (DWL Gmbh), to automatically count emboli and differentiate between solid and gaseous emboli.Results
Over the period of May 2012–October 2013, a total of 39 patients had adequate windows and underwent TCD examination during their TAVI procedure. Where TCD windows were found bilaterally, the mean number of emboli at each time interval was used. The total number of emboli per middle cerebral artery was 389.2 (± 227.8), of which the solid emboli were 89.4 (±51.9). The number of solid emboli generated at each time point in order of frequency were: valve positioning (27.4 ± 18.1 emboli), crossing the valve and exchanging catheters (20.6 ± 19.1), valve deployment (14.6 ± 27.2), removing the delivery system (9.3 ± 9.9), insertion of diagnostic catheters (7.1 ± 10.4), balloon valvuloplasty (6.5 ± 8.2), late emboli after removal of delivery system (4.1 ± 4.0), positioning the balloon for valvuloplasty (2.5 ± 3.2) and moving the valve through the aortic arch (1.5 ± 2.6).Conclusion
Solid emboli during TAVI occur most frequently during valve positioning, crossing the valve and valve deployment. This could be important when designing embolic protection strategies to prevent stroke in high risk patients undergoing TAVI. Further work is needed to assess factors which influence the rate of embolisation and the neurocognitive outcomes associated with this.