Development of paradoxical low-flow, low-gradient severe aortic stenosis

Objective: Among patients with severe aortic stenosis (sAS) and preserved LVEF, those with low-flow, low-gradient sAS (LFLG-sAS) have an adverse prognosis. It has been proposed that LFLG-sAS represents an end-stage point of sAS, but longitudinal information has not been described. The aim was to determine whether LFLG-sAS represents an end-stage consequence of normal-flow, high-gradient sAS (NFHG-sAS) or a different entity. Methods: From our transthoracic echocardiogram (TTE) database, we identified patients with sAS (aortic valve area <1 cm²) and preserved LVEF (≥50%), and from these, patients with LFLG-sAS (stroke volume index <35 mL/m² and mean transvalvular gradient <40 mm Hg) who had ≥1 additional TTE within five years prior to the index TTE. Patients were age/sex/ date matched 2:1 with patients with NFHG-sAS and normal-flow, low-gradient (NFLG)-sAS who also had ≥1 TTE. Included were 1203 TTEs (383 index studies and 820 preceding studies). Results: In 78 patients with LFLG-sAS, an HG stage preceded the index TTE in only 4 (5%). During the five years preceding the index TTE, patients with LFLG-sAS developed increasing relative wall thickness (0.42 to 0.49; p<0.001) without change in LV mass index. Patients with NFHG-sAS had a marked increase in LV mass index (87 to 115 g/m²; p<0.001). Patients with LFLG-sAS demonstrated the greatest reduction in LV enddiastolic diameters (-3 vs -1 for NFLG-sAS vs +2 mm for NFHG-sAS; p=0.001), deceleration time (-55 vs -3 vs +3 ms, respectively; p<0.01) and LVEF (-4 vs 0 vs 0%, respectively; p=0.01). Conclusions: LFLG-sAS is a distinct presentation of sAS preceded by a unique remodelling pathway and is uncommonly preceded by an HG stage.