Tryptase Levels as a Marker of Mast Cell Activity and the Prognostic Implication in Patients Post Transcatheter Aortic Valve Replacement

Inflammation is known to have a detrimental effect on outcome of patients with myocardial infarction (MI) [1, 2] as well as reperfusion injury (RI) [3]. Previous trials have shown correlation between the extent of an inflammatory response and postoperative complications and worse outcomes in patients undergoing cardiac surgery [4, 5, 6, 7] including valve replacement [8]. Transcatheter aortic valve replacement (TAVR) may be associated with inflammation [5, 9] as well. A few possible mechanisms may be responsible, such as tissue injury due to mechanical trauma, vascular complications, and possible suboptimal organ perfusion due to bleeding, ventricular pacing, balloon valvuloplasty, deployment, post-dilatation, or repositioning of the valve prosthesis [10]. Accumulating data show that peri-procedural inflammation is associated with worse outcomes and complications of TAVR [11, 12, 13, 14, 15], and may predict increased mortality in patients after TAVR [16, 17, 18, 19, 20].

Inflammation is a complex process and includes many types of cells including mast cells. The association between mast cells, as part of the inflammatory process, and RI has been thoroughly studied. Mast cells have been linked to RI in many organs [21], contributing to insult to the myocardium. This association has been suggested from animal models [22, 23, 24] as well as recent human trials which showed that tryptase, an abundant protease found in mast cell granules, is elevated in ST segment elevation myocardial infarction (STEMI) patients treated with primary percutaneous coronary intervention (PCI) [25].

Therefore, it is reasonable to assume that mast cells may have a role in the inflammation process involved in patients undergoing TAVR. Moreover, such association with mast cells may be used to predict adverse outcomes.

To our knowledge, an association between mast cells and outcomes of patients undergoing TAVR has not been studied.

METHODS Peripheral venous blood from 30 patients undergoing TAVR will be withdrawn to examine tryptase levels, as a marker of mast cell activity. Blood samples will be taken at 0 hours (before the procedure) and a second sample will be taken up to 2 hours post-procedure.