Transient ischemic attack and stroke
Stroke is probably the most feared neurological complication following aortic valve surgery. The incidence of stroke after traditional AVR in all patients is approximately 1.6% 23, but may be greater in high risk patients and those with previous coronary artery bypass surgery 24. Stroke is a major source of morbidity in patients following TAVR, with an incidence of 2.4–9.1% after TF-TAVR and 1.5–6.7% after TA-TAVR 24. In a recent study of 31 patients who underwent TAVR, diffusion-weighted MRI identified new cerebral infarcts in 77% of patients postoperatively 25. The authors identified increased severity of aortic atheroma as a risk factor for new cerebral infarcts.
Neurologic events following TAVR peak in the first week postoperatively. In an analysis of patients enrolled in the PARTNER trial, 12/31 events (stroke or TIA) occurred between postoperative days 0–2 24. In a study of 253 patients who underwent TAVR (who were not part of the PARTNER trial), the risk of stroke or TIA was greatest in the first 24 hours after surgery 26.
While perioperative and intraoperative hypotension may be responsible, neurologic events occurring in the first 24 hours are likely related to embolization of calcium and debris, or thrombi that may form on wires and surgical devices intraoperatively 24, 26. Indeed, a smaller aortic valve area index is associated with a greater risk of early stroke, possibly due to increased propensity for calcium embolization 24. New devices are in development to reduce the incidence of cerebral emboli, including the SMT Embolic Deflection Device, which acts as a filter in the aortic arch, reducing emboli to the brain 27.
Infarcts affecting the distribution of the middle cerebral artery, the posterior circulation, or involving multiple sites are often embolic in nature, and are characteristic of the cerebral infarcts seen immediately after TAVR 26. We believe knowledge of the clinical presentation of embolism to these vessels is critical in order to rapidly diagnose and treat any events. In recognition of the risk of embolic stroke, in the absence of significant postoperative bleeding, anticoagulation is usually initiated on postoperative day 1. Dual antiplatelet therapy (aspirin and clopidogrel) may be used, or aspirin and warfarin if a patient is already taking warfarin for concomitant atrial fibrillation. Although there are no absolute guidelines, anticoagulation is often continued for several months following surgery.