Risk Stratification for Subclinical Leaflet Thrombosis Post TAVI Using Thromboelastography

Aortic stenosis is the most common primary valve disease in high-income countries with increasing importance. Throughout the last 15 years, transcatheter aortic valve implantation (TAVI) has become an alternative to surgical aortic valve replacement, the former standard of care. Nowadays, the use of TAVI in elderly patients at increased surgical risk is favored. There is still an important lack of evidence concerning the optimal antithrombotic strategy post TAVI. Recently, it has been shown that the prevalence of subclinical leaflet thrombosis after intervention has been underestimated and may be present in around 15 % up to 40% (PORTICO IDE trial) of transcatheter valves. One study demonstrated that transient ischemic attacks are significantly increased in these patients.

European guidelines are undecided towards the length of the dual antiplatelet therapy (DAPT) after TAVI and recommend optional treatment durations between 3 to 6 months. The optimal duration of DAPT is not known, although DAPT duration is associated with an increased bleeding risk. The most recent update of AHA guidelines for valvular heart disease state that oral anticoagulation with a VKA (INR of 2.5) may be reasonable for at least 3 months after TAVI in patients at low risk of bleeding. Without favoring one over the other recommendation, the current AHA guidelines also maintain the prior statement (from 2014) that clopidogrel 75 mg daily may be reasonable for the first 6 months after TAVI in addition to life-long aspirin, which is in accordance with the European Guideline recommendation. On the other hand, the GALILEO trial has recently been stopped as patients receiving rivaroxaban after TAVI (no prior atrial fibrillation) had a higher mortality and thromboembolic events as well as higher bleeding event rates.

The TEG(R) 6S analyzer is a point-of-care system evaluating a patient's individual hemostasis profile by thrombelastography (TEG(R)), a potentially superior tool compared to conventional platelet function testing. The TEG(R) system has been able to predict thrombotic complications in different clinical contexts.

In classic coronary interventional cardiology, the strength of adenosine diphosphate (ADP)-induced and thrombin-induced platelet-fibrin clots were found to be indicators of long-term poststenting ischemic events. As the pathophysiologic mechanism of subclinical leaflet thrombosis has not been examined in detail, the investigators hypothesize that several TEG(R) assays may provide insight in finding predictive TEG(R) markers. Furthermore, as the onset of subclinical leaflet thrombosis is not clear and may possibly increase over time, the design with subsequent TEG(R) analyses at 3 timepoints (0, 3, 6 months) will help to hopefully identify predictors that may become evident at later time points.

It is intriguing to hypothesize that the better predictive marker may be found using the Global Hemostasis Assay. This is relevant as leaflet thrombosis develops despite dual antiplatelet therapy and anticoagulation has been shown to fully resolve subclinical leaflet thrombosis. The Global Hemostasis Assay may deliver prediction beyond platelet function, which may improve antithrombotic therapy post TAVI. Finding a predictive TEG marker (examining Platelet Mapping and Global Hemostasis together) holds the promise for future individualized clinical decision-making by identifying individual risk.