Prognostic value of transvalvular flow rate in patients with low-gradient severe aortic stenosis: A dobutamine stress echocardiography study

BACKGROUNDS

There are limited data on the clinical relevance of transvalvular flow rate (Qmean ) at rest (Qrest) and at peak stress (Qstress ) during dobutamine stress echocardiography (DSE) in patients with low-gradient severe aortic stenosis (LG-SAS).

METHODS

We retrospectively analyzed the clinical data of patients with LG-SAS who underwent DSE. LG-SAS was defined as an aortic valve (AV) area index of < .6 cm2 /m2 and a mean AV pressure gradient (AVPG) of < 40 mm Hg. The primary endpoint included all-cause death and heart failure hospitalization.

RESULTS

Of 100 patients (mean age 79.5 ± 7.3 years; men, 45.0%; resting left ventricular ejection fraction [LVEF] 52.1% ± 15.9%; resting stroke volume index 35.8 ± 7.7 mL/m2 ; Qrest 171.8 ± 34.9 mL/s), the primary endpoint occurred in 51 patients during a median follow-up of 2.84 (interquartile range 1.01-5.21) years. When the study patients were divided into three subgroups based on Qrest and Qstress , the multivariate analysis showed that Qrest < 200 mL/s and Qstress ≥200 mL/s (hazard ratio 3.844; 95% confidence interval 1.143-12.930; p = .030), as well as Qrest and Qstress < 200 mL/s (hazard ratio 9.444; 95% confidence interval 2.420-36.850; p = .001), were significantly associated with unfavorable outcomes with Qrest and Qstress ≥200 mL/s as a reference after adjusting for resting LVEF, resting mean AVPG, chronic kidney disease, New York Heart Association functional class III/IV, and AV replacement.

CONCLUSIONS

Flow conditions based on the combination of Qrest and Qstress are helpful for risk stratification in LG-SAS patients.

Stroke volume index and transvalvular flow rate trajectories in severe aortic stenosis treated with TAVR

AIMS

The prognostic impact of flow trajectories according to stroke volume index (SVi) and transvalvular flow rate (FR) in patients with severe aortic stenosis (AS) undergoing transcatheter aortic valve replacement (TAVR) remains poorly assessed. We evaluated and compared SVi and FR prior and after TAVR for severe AS.

METHODS AND RESULTS

Patients were categorized according to SVi (<35 mL/m2) and FR (<200 mL/s). The association of pre- and post-TAVR SVi and FR with all-cause mortality up to 3 years was assessed with multivariable Cox regression models. Among 980 patients with pre-TAVR flow assessment, SVi was reduced in 41.3% and FR in 48.1%. Baseline flow status was not an independent mortality predictor [SVi: hazard ratio (HR) 1.22, 95% confidence interval (CI) 0.85-1.82, FR: HR 0.78, 95% CI 0.48-1.27]. Among 731 patients undergoing early (5 days, interquartile range 2-29) post-TAVR flow assessment, SVi recovered in 40.1% and FR in 49.0% patients with baseline low flow. Reduced FR following TAVR was an independent predictor of mortality (HR 1.67, 95% CI 1.02-2.74), whereas SVi was not (HR 0.97, 95% CI 0.53-1.78). Three-year estimated mortality in patients with recovered FR was lower than that in patients with reduced FR (13.3 vs. 37.7% vs, P = 0.003) and similar to that in patients with normal baseline FR (P = 0.317).

CONCLUSION

Baseline flow status was not an independent predictor of mid-term mortality among all-comers with severe AS undergoing TAVR. Flow recovery early after TAVR was frequent. Post-TAVR FR, but not SVi, was independently associated with mid-term all-cause mortality. By impacting flow status, AV replacement modifies the association of flow status with outcomes.

Value of Left Ventricular Indexed Ejection Time to Characterize the Severity of Aortic Stenosis

Aims: The assessment of aortic stenosis (AS) severity is still challenging, especially in abnormal hemodynamic conditions. Left ventricular ejection time (LVET) has been historically related to AS severity, but it also depends on heart rate (HR) and systolic function. Our aim was to verify if correcting LVET (LVET index, LVETI) by its determinants is helpful for the assessment of AS severity, irrespective of hemodynamic conditions. Methods and results: We retrospectively studied 152 patients with AS and 378 patients with heart failure and no-AS. At multivariate analysis, LVET (assessed with pulsed-wave Doppler) showed a strong correlation with stroke volume index (SVI) (Beta 0.354; p < 0.001), HR (−0.385; p < 0.001), AS grade (Beta 0.301; p < 0.001) and, less significantly, ejection fraction (LVEF) (Beta 0.108; p = 0.001). AS grade was confirmed to be a major determinant of LVET, irrespective of forward flow (assessed by SVI and transvalvular flow rate) and LVEF (above and below 50%). A regression equation was derived to index LVET (LVETI) to HR and SVI. By using this formula, LVETI detected severe AS more accurately (AUC 0.812, p < 0.001) than LVET alone (AUC 0.755, p for difference = 0.005). Similar results were observed in patients with abnormal flow status. As an exploratory finding, we observed that the highest tertile of LVETI was associated with a higher rate of aortic valve interventions during follow-up. Conclusions: LVETI correlates with AS severity better than uncorrected LVET, independently from hemodynamic conditions, and may help to discriminate severe AS. This finding needs confirmation in larger prospective multicenter studies.

Comparison of transvalvular flow rate in aortic stenosis subtypes

OBJECTIVES

Evaluate ET and TVFR in normal patients, PLFLGAS, LGLFAS, and classic pre and post TAVR.

BACKGROUND

Severe aortic stenosis (AS) is defined echocardiographically. Generating a pressure gradient to meet diagnostic criteria is dependent on left ventricular contractility, stroke volume, and ejection time.  Abnormalities in these decrease the mean pressure gradient across the valve creating pathology termed low flow, low gradient AS. This occurs in two subtypes, low ejection fraction LFLGAS and paradoxical LFLGAS (PLFLGAS), in which EF is normal but stroke volume is < 35 ml/m² . Paradoxical LFLGAS is difficult to diagnose and does not have a confirmatory echocardiographic parameter. Transvalvular flow rate (TVFR), which is defined as stroke volume divided by the ejection time, provides a direct measure of flow across the aortic valve.

METHODS

A retrospective study of patients who underwent transcatheter aortic valve replacement (TAVR) at the University of Cincinnati Medical Center between 2016 and 2019 was performed. Patients were classified by AS subtype. ET and TVFR were measured pre and post TAVR and statistically compared using SPSS statistics software and ANOVA analysis.

RESULTS

Pre TAVR TVFR in the normal population, severe AS population, and LFLGAS were not significantly different. The pre TAVR TVFR in paradoxical LFLGAS patients was significantly lower than other groups. TVFR improved to the greatest degree post TAVR in PLFLGAS but did not meet statistical significance.

CONCLUSIONS

The significantly lower TVFR demonstrated in PLFLGAS provides a comprehensive, direct measurement of aortic valve hemodynamics and PLFLGAS pathology and can aid in diagnosis.