Transvalvular Flow Rate Determines Prognostic Value of Aortic Valve Area in Aortic Stenosis

J Am Coll Cardiol. 2020 Apr 21;75(15):1758-1769. doi: 10.1016/j.jacc.2020.02.046.

Abstract

Background: Aortic valve area (AVA) ≤1.0 cm2 is a defining characteristic of severe aortic stenosis (AS). AVA can be underestimated at low transvalvular flow rate. Yet, the impact of flow rate on prognostic value of AVA ≤1.0 cm2 is unknown and is not incorporated into AS assessment.

Objectives: This study aimed to evaluate the effect of flow rate on prognostic value of AVA in AS.

Methods: In total, 1,131 patients with moderate or severe AS and complete clinical follow-up were included as part of a longitudinal database. The effect of flow rate (ratio of stroke volume to ejection time) on prognostic value of AVA ≤1.0 cm2 for time to death was evaluated, adjusting for confounders. Sensitivity analysis was performed to identify the optimal cutoff for prognostic threshold of AVA. The findings were validated in a separate external longitudinal cohort of 939 patients.

Results: Flow rate had a significant effect on prognostic value of AVA. AVA ≤1.0 cm2 was not prognostic for mortality (p = 0.15) if AVA was measured at flow rates below median (≤242 ml/s). In contrast, AVA ≤1.0 cm2 was highly prognostic for mortality (p = 0.003) if AVA was measured at flow rates above median (>242 ml/s). Findings were irrespective of multivariable adjustment for age, sex, and surgical/transcatheter aortic valve replacement (as time-dependent covariates); comorbidities; medications; and echocardiographic features. AVA ≤1.0 cm2 was also not an independent predictor of mortality below median flow rate in the validation cohort. The optimal flow rate cutoff for prognostic threshold was 210 ml/s.

Conclusions: Transvalvular flow rate determines prognostic value of AVA in AS. AVA measured at low flow rate is not a good prognostic marker and therefore not a good diagnostic marker for truly severe AS. Flow rate assessment should be incorporated into clinical diagnosis, classification, and prognosis of AS.

Keywords: aortic stenosis; flow rate; low flow; low gradient; outcome; prognosis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Algorithms
  • Aortic Valve / diagnostic imaging
  • Aortic Valve / physiopathology*
  • Aortic Valve / surgery
  • Aortic Valve Stenosis / mortality*
  • Aortic Valve Stenosis / physiopathology
  • Aortic Valve Stenosis / surgery*
  • Echocardiography, Doppler
  • Female
  • Follow-Up Studies
  • Heart Valve Prosthesis Implantation / statistics & numerical data
  • Hemodynamics
  • Humans
  • Male
  • Prognosis
  • Sex Factors
  • Stroke Volume / physiology*