Assessment of Normal-Flow Aortic Stenosis

The increasing complexity of assessing aortic stenosis (AS) will perhaps haunt cardiologists in years to come. Did we over-complicate it, were we overly ambitious in trying to identify those who might benefit from intervention? These are questions that we will be held accountable for by the vast numbers of patients who now carry some form of this diagnosis, and we have reason to be concerned. The previously accepted interventional indicators in AS, predominantly defined by a mean gradient >40 mm Hg and AVA <1 cm with accompanying symptoms, have now almost become a distant memory. There are currently 4 different subtypes: classic low-flow low-gradient (LFLG), paradoxical LFLG, normalflow low-gradient (NFLG), and normal-flow high-gradient (NFHG). With these added layers of complexity in AS grading has come some unease regarding appropriate management, with many patients falling below current thresholds for intervention. Indeed, although NFLG AS is included in current guidelines, much thought is now directed toward deciphering its true hemodynamic cost, with some concern that it does not actually represent severe stenosis. With the obvious exception of NFHG, what is lacking is a defining level of evidence regarding expected interventional outcomes, with inconsistent reports of survival advantage. This is an unfavorable situation and has led to debate concerning optimal management, and variation in clinical practice.