The Flow Rate in Patients With Low-Gradient Aortic Stenosis

PURPOSE

 The decision to assess the severity and determine the ideal timing of intervention for low-gradient aortic stenosis poses a greater challenge. Recently, a novel method for determining the flow status of patients with aortic stenosis has been introduced, utilizing flow rate measurements. In this study, we investigated whether the flow status of patients with low-gradient aortic stenosis is linked to mortality within a three-year timeframe.

METHODS

Twenty-nine patients diagnosed with low-gradient aortic stenosis and valve area ≤ 1 cm were identified during 2010-2015. Each patient's flow rate across the aortic valve was computed, and the study scrutinized echocardiographic parameters to ascertain their correlation with mortality over a three-year timeframe.

RESULTS

 We observed that among patients with low-gradient aortic stenosis and a valve area of ≤1 cm, a decreased flow rate across the aortic valve emerged as an independent predictor of mortality. A flow rate < 210 ml/s was linked with a three-year mortality rate of 66.7%, whereas a low stroke volume index < 35 ml/m² did not show an association with three-year mortality. This observation might be attributed to the smaller body sizes prevalent among these older patients, particularly females, which could influence the calculation of the stroke volume index.

CONCLUSION

 In older patients with low-gradient aortic stenosis, the flow rate can better reflect flow status than the stroke volume index, and it also suggests a prognostic significance in predicting mortality. Additional studies are warranted to validate these findings across broader patient populations and to assess the potential efficacy of early intervention strategies in this particular patient cohort.

Prognostic value of flow-status in severe aortic stenosis patients undergoing percutaneous intervention

PURPOSE

Low-flow status is a mortality predictor in severe aortic stenosis (SAS) patients, including after transcatheter aortic valve implantation (TAVI) treatment. However, the best parameter to assess flow is unknown. Recent studies suggest that transaortic flow rate (FR) is superior to currently used stroke volume index (SVi) in defining low-flow states. Therefore, we aimed to evaluate the prognostic value of FR and SVi in patients undergoing TAVI.

METHODS

A single-centre retrospective analysis of all consecutive patients treated with TAVI for SAS between 2011 and 2019 was conducted. Low-FR was defined as < 200 mL/s and low-SVi as < 35 mL/m2. Primary endpoint was all-cause five-year mortality, analyzed using Kaplan-Meier curves and Cox regression models. Secondary endpoint was variation of NYHA functional class six months after procedure. Patients were further stratified according to ejection fraction (EF < 50%).

RESULTS

Of 489 cases, 59.5% were low-FR, and 43.1% low-SVi. Low-flow patients had superior surgical risk, worse renal function, and had a higher prevalence of coronary artery disease. Low-FR was associated with mortality (hazard ratio 1.36, p = 0.041), but not after adjustment to EuroSCORE II. Normal-SVi was not associated with survival, despite a significative p-trend for its continuous value. No associations were found for flow-status and NYHA recovery. When stratifying according to preserved and reduced EF, both FR and SVi did not predict all-cause mortality.

CONCLUSION

In patients with SAS undergoing TAVI, a low-FR state was associated with higher mortality, as well as SVi, but not at a 35 mL/m2 cut off.

Low Transvalvular Flow Rate in Patients Undergoing Transcatheter Aortic Valve Implantation (TAVI) Is a Predictor of Mortality: The TFR-TAVI Study

BACKGROUND

Transvalvular flow rate (TFR) represents a better reflection of transvalvular flow than the stroke volume index (SVi), and has recently emerged as a useful prognostic tool in patients undergoing surgical aortic valve replacement. There is a paucity of data investigating the role of TFR and its relationship with other clinical or echocardiographic factors in patients undergoing transcatheter aortic valve implantation (TAVI).

METHOD

This was a retrospective single-centre study of 629 consecutive patients who underwent TAVI between March 2009 and September 2020. Pre-TAVI low TFR was defined as <200 c/s. The primary study end point was all-cause mortality.

RESULTS

Low TFR was observed in 41.8% (263/629) of included patients and was associated with increasing age, low body surface area, hypertension, diabetes, atrial fibrillation, left ventricular (LV) dysfunction, and significant mitral regurgitation. LV function status and severity of aortic valve disease were independent predictors of low TFR. Low TFR was significantly associated with long-term all-cause mortality even after adjustment for other risk factors (adjusted hazard ratio [aHR] 1.44; 95% confidence interval [CI] 1.02-2.03; p=0.038). When data were stratified according to SVi, low TFR was an independent predictor of long-term all-cause mortality in patients with normal SVi (aHR 1.98; 95% CI 1.06-3.69; p=0.032) but not in patients with low SVi (HR 1.23; 95% CI 0.71-2.11; p=0.46; p=0.016 for interaction).

CONCLUSIONS

Low TFR is common in patients undergoing TAVI and is an independent predictor of all-cause mortality, particularly in patients with normal SVi.

Using Discrete Multiphysics Modelling to Assess the Effect of Calcification on Hemodynamic and Mechanical Deformation of Aortic Valve

This study proposes a 3D particle-based (discrete) multiphysics approach for modelling calcification in the aortic valve. Different stages of calcification (from mild to severe) were simulated, and their effects on the cardiac output were assessed. The cardiac flow rate decreases with the level of calcification. In particular, there is a critical level of calcification below which the flow rate decreases dramatically. Mechanical stress on the membrane is also calculated. The results show that, as calcification progresses, spots of high mechanical stress appear. Firstly, they concentrate in the regions connecting two leaflets; when severe calcification is reached, then they extend to the area at the basis of the valve.