We read the report by Nuis et al on the frequency and cause of stroke during and after transcatheter aortic valve implantation (TAVI). The investigators reported a 9% stroke incidence (19 of 214 patients), with early (<24 hours after TAVI) stroke in 8 patients and delayed (>24 hours, mean 3.5 days after TAVI) stroke in 11 patients. They used brain computed tomographic findings to further analyze the cause of stroke. Interestingly, they found that 26% of strokes (5 patients) revealed lacunar lesions, which is widely regarded as caused by cerebral hypoperfusion in the presence of local atherosclerosis. Therefore, the investigators implied that all efforts should be made during TAVI to maintain adequate brain perfusion.

In the study by Nuis et al, the Medtronic CoreValve System (Medtronic, Inc., Minneapolis, Minnesota) was used, which necessitates only short-term use of rapid ventricular pacing (RVP) during valvuloplasty. However, during application of the Edwards Sapien valve (Edwards Lifesciences, Irvine, California), a transient partial cardiac standstill by RVP (180 to 220 beats/min) is induced to minimize cardiac motion and pulsatile transaortic flow. Although RVP is advantageous for valve positioning, the combination of a rapid heart rate and ventricular hypertrophy can induce a complete loss of cardiac output. In most cases, this hemodynamic deficit is well tolerated, most likely because of the brief duration of the RVP. However, in view of these results published by Nuis et al, more attention should be paid to maintain adequate cerebral perfusion (and oxygenation) during TAVI, especially during these RVP periods when using the Edwards Sapien valve.

In recent years, near-infrared spectroscopy (NIRS) has been introduced as a useful noninvasive cerebral monitoring technique assessing the adequacy of cerebral oxygenation. It measures regional cerebral oxygen saturation at the microvascular level (arterioles, venules, and capillaries only). The principle of NIRS is based on the fact that near-infrared light passes through skin and skull readily and is absorbed by certain biologic molecules in the brain. Low cerebral oxygen saturation values (<55%), as measured by NIRS, observed during cardiac surgery have been correlated with worsened postoperative neurologic outcomes.

In recent months, we applied NIRS monitoring during TAVI procedures (using the Edwards Sapien valve), and we did observe an immediate decrease in cerebral oxygen saturation during RVP to 54% (37% to 70%). Moreover, in 1 patient with severe concomitant heart failure, cerebral oxygen saturation remained <55% for 87 minutes (despite ongoing cardiopulmonary resuscitation efforts) and returned to baseline after the institution of extracorporeal membrane oxygenation. The patient’s hemodynamic status perfectly stabilized, but unfortunately, the patient was declared brain dead 48 hours later.

Referring to Nuis et al and to our own experience, we should be aware that transcutaneous cardiac interventions, especially those with transient partial cardiac standstill, can induce long-lasting intraprocedural inadequacy of cerebral perfusion, despite immediate restoration of normal blood pressure. Future strategies should therefore be focused on integrating noninvasive continuous cerebral monitoring, such as NIRS, providing real-time estimation of the adequacy of cerebral perfusion, during TAVI procedures.