Reliability of Aortic Stenosis Severity Classified by 3-Dimensional Echocardiography in the Prediction of Cardiovascular Events

Prediction of symptom development and aortic valve replacement in patients with low-gradient severe aortic stenosis

Aims

Current evidence on the prognostic value of exercise stress echocardiography (ESE) in asymptomatic patients with low-gradient severe aortic stenosis (AS) is limited. Therefore, this study aimed to elucidate its prognostic implications for patients with low-gradient severe AS and determine the added value of ESE in risk stratification for this population.

Methods and results

This retrospective observational study included 122 consecutive asymptomatic patients with either moderate [mean pressure gradient (MPG) < 40 mmHg and aortic valve area (AVA) 1.0-1.5 cm2] or low-gradient severe (MPG < 40 mmHg and AVA < 1.0 cm2) AS and preserved left ventricular ejection fraction (≥50%) who underwent ESE. All patients were followed up for AS-related events. Of 143 patients, 21 who met any exclusion criteria, including early interventions, were excluded, and 122 conservatively managed patients [76.5 (71.0-80.3) years; 48.3% male] were included in this study. During a median follow-up period of 989 (578-1571) days, 64 patients experienced AS-related events. Patients with low-gradient severe AS had significantly lower event-free survival rates than those with moderate AS (log-rank test, P < 0.001). Multivariable Cox regression analysis showed that the mitral E/e' ratio during exercise was independently associated with AS-related events (hazard ratio = 1.075, P < 0.001) in patients with low-gradient severe AS.

Conclusion

This study suggests that asymptomatic patients with low-gradient severe AS have worse prognoses than those with moderate AS. Additionally, the mitral E/e' ratio during exercise is a useful parameter for risk stratification in patients with low-gradient severe AS.

Physical and physiological effects of dobutamine stress echocardiography in low-gradient aortic stenosis

Dobutamine stress echocardiography (DSE) is a useful tool for assessing low-gradient significant aortic stenosis (AS) and contractile reserve (CR), but its prognostic utility has become controversial in recent studies. We evaluated the impact of DSE on aortic valve physiological, structural, and left ventricular parameters in low-gradient AS. Consecutive patients undergoing DSE for low-gradient AS evaluation from September 2010 to July 2016 were retrospectively studied, and DSE findings were divided into four groups: with and without severe AS and/or CR. Relationships between left ventricular chamber quantification, CR, aortic valve Doppler during DSE, and calcium score [by computerized tomography (CT)] were analyzed. There were 258 DSE studies performed on 243 patients, mean age 77.6 ± 10.8 yr and 183 (70.1%) were males. With increasing dobutamine dose, apart from systolic blood pressure, left ventricular ejection fraction, flow, cardiac power output, and longitudinal strain magnitude, along with aortic valve area and mean aortic gradient were all significantly increased (P < 0.05). Flow and mean gradient increased in both the presence and absence of CR, whereas stroke volume and aortic valve area increased mainly in those with CR only. The aortic valve area increased in both patients with low and high calcium scores; however, the baseline area was lower in those with a higher calcium score. During DSE, aortic valve area increases with increase in aortic valve gradient. Higher calcium score is associated with lower baseline aortic valve area, but the aortic valve area still increases with dobutamine even in presence of a high calcium score.NEW & NOTEWORTHY We show that even in most severe aortic stenosis, there is some residual valve pliability. This suggests that a complete loss of pliability is not compatible with survival.

Application of the proximal isovelocity surface area method for estimation of the effective orifice area in aortic stenosis

Although the echocardiographic effective orifice area (EOA) calculated using the continuity equation is widely used for the assessment of severity in aortic stenosis (AS), the existence of high flow velocity at the left ventricular outflow tract (LVOT) potentially causes its overestimation. The proximal isovelocity surface area (PISA) method could be an alternative tool for the estimation of EOA that limits the influence of upstream flow velocity. EOA was calculated using the continuity equation (EOA_Cont) and PISA method (EOA_PISA), respectively, in 114 patients with at least moderate AS. The geometric orifice area (GOA) was also measured using the planimetry method in 51 patients who also underwent three-dimensional transesophageal echocardiography. Patients were divided into two groups according to the median LVOT flow velocity. EOA_PISA could be obtained in 108 of the 114 patients (95%). Although there was a strong correlation between EOA_Cont and EOA_PISA (r = 0.78, P < 0.001), EOA_Cont was statistically significantly larger than EOA_PISA (0.86 ± 0.33 vs 0.75 ± 0.29 cm², P < 0.001). Both EOA_Cont and EOA_PISA similarly correlated with GOA (r = 0.70, P < 0.001 and r = 0.77, P < 0.001, respectively). However, a fixed bias, which is hydrodynamically supposed to exist between EOA and GOA, was not observed between EOA_Cont and GOA. In contrast, there was a negative fixed bias between EOA_PISA and GOA with smaller EOA_PISA than GOA. The difference between EOA_Cont and GOA was significantly greater with a larger EOA_Cont relative to GOA in patients with high LVOT flow velocity than in those without (0.16 ± 0.25 vs - 0.07 ± 0.10 cm², P < 0.001). In contrast, the difference between EOA_PISA and GOA was consistent regardless of the LVOT flow velocity (- 0.07 ± 0.12 vs - 0.07 ± 0.15 cm², P = 0.936). The PISA method was applied to estimate EOA in patients with AS. EOA_PISA could be an alternative parameter for AS severity grading in patients with high LVOT flow velocity in whom EOA_Cont would potentially overestimate the orifice area.

Higher rate of aortic stenosis progression in patients with bicuspid versus tricuspid aortic valve - A single center experience

PURPOSE

We sought to investigate aortic stenosis (AS) progression rate (pr) with the comparison between bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV) morphology.

MATERIALS AND METHODS

We compared ASpr in patients with BAV and TAV examined by transthoracic echocardiography (TTE) in the years 2004-2019.

RESULTS

Data from 363 TTEs in 161 AS patients (median age 70 [61-77] years; 63% men; 25% with BAV; 20% with severe AS) performed at different time points (median time interval 10 months) was analyzed. We assessed changes of AS severity with peak velocity through aortic valve (Vmax), mean/peak pressure gradients (MG/PG), aortic valve area by planimetry and continuity equation (AVAce). We compared pr (defined as parameter change per year) between the BAV and the TAV groups. BAV patients showed faster ASpr with odds ratio 3.467 and 95% confidence intervals 1.36 to 8.86, moreover, expressed as a quicker AVAce decrease 0 (-0.4-0.0) in the BAV vs. 0 (-0.15 - 0.0) cm²/year in the TAV group, p ​= ​0.02. Furthermore, in BAV, female sex was associated with lower ASpr (p ​= ​0.01), and in the whole group a larger aortic diameter was a predictor of faster progression (p ​< ​0.001).

CONCLUSION

The ASpr, expressed as a decrease in the AVAce, was faster in BAV. Moreover, ASpr depends on both: valve morphology being faster in BAV and Vmax increase. Furthermore, the female sex was related to slower pace of AVA reduction in BAV subgroup whereas the larger baseline aortic diameter associated to faster AS progression in the whole studied group.

Discrepancy of Aortic Valve Area Measurements by Doppler vs. Biplane Stroke Volume Measurements and Utility of Combining the Different Areas in Aortic Valve Stenosis - The Asian Valve Registry

BACKGROUND

The aortic valve area index (AVAI) in aortic stenosis (AS) is measured by echocardiography with a continuity equation using the stroke volume index by Doppler (SVIDoppler) or biplane Simpson (SVIBiplane) method. AVAIDopplerand AVAIBiplaneoften show discrepancy due to differences between SVIDopplerand SVIBiplane. The degree of discrepancy and utility of combined AVAIs have not been investigated in a large population of AS patients, and the characteristics of subjects with larger discrepancies are unknown.

METHODS AND RESULTS

We studied 820 patients with significant AS (AVADoppler<1.5 cm2) enrolled in the Asian Valve Registry, a prospective multicenter registry at 12 Asian centers. All-cause death and aortic valve replacement were defined as events. SVIDopplerwas significantly larger than SVIBiplane(49±11 vs. 39±11 mL/m2, P<0.01) and AVAIDopplerwas larger than AVAIBiplane(0.51±0.15 vs. 0.41±0.14 cm2/m2, P<0.01). An increase in (AVAIDoppler- AVAIBiplane) correlated with shorter height, lower weight, older age, smaller left ventricular (LV) diameter and increased velocity of ejection flow at the LV outflow tract. Severe AS by AVAIDoppleror AVAIBiplaneenabled prediction of events, and combining these AVAIs improved the predictive value of each.

CONCLUSIONS

Discrepancy in AVAI by Doppler vs. biplane method was significantly more pronounced with increased LV outflow tract flow velocity, shorter height, lower weight, older age and smaller LV cavity dimensions. Combining the AVAIs enabled mutual and incremental value in predicting events.

Contemporary Outcomes in Low-Gradient Aortic Stenosis Patients Who Underwent Dobutamine Stress Echocardiography

Background

Detection of flow reserve (FR) by dobutamine stress echocardiography is used for risk stratification in low‐gradient aortic stenosis (AS). Prognostic significance of dobutamine stress echocardiography in the transcatheter aortic valve replacement era is unclear. We aimed to assess the current relevance of FR.

Methods and Results

We studied 235 patients with low‐gradient severe AS (rest aortic valve area ≤1.0 cm² or indexed aortic valve area ≤0.60 cm²/m²; mean aortic valve gradient <40 mm Hg) and left ventricular ejection fraction <50%) with dobutamine stress echocardiography done September 2010 through July 2016. FR was defined by ≥20% stroke volume increase. We diagnosed “true‐severe AS” if peak aortic valve velocity ≥4 m/s occurred with aortic valve area ≤1.0 cm² (or indexed aortic valve area ≤0.6 cm²/m²). At a median time of 51 days, 128 patients underwent aortic valve replacement,either surgical aortic valve replacement (n=42) or transcatheter aortic valve replacement (n=86). FR was observed in 138 patients, while 86 patients had true‐severe AS. During median follow‐up of 2.3 years, 138 patients died. In a multivariable model, aortic valve replacement (hazard ratio 0.41, 95% CI: 0.29–0.58, P <0.001) and lower Society of Thoracic Surgeons score (hazard ratio 1.06, 95% CI: 1.04–1.09, P<0.001) were associated with better survival, while FR was not predictive. aortic valve replacement was associated with survival regardless of the presence or absence of FR or AS severity stratification.

Conclusions

In low‐gradient AS with reduced ejection fraction, FR or AS severity stratification by dobutamine stress echocardiography was not associated with survival. Aortic valve replacement was associated with better survival in low‐gradient AS independent of FR.

See Editorial by Annabi et al

Geometry of the left ventricular outflow tract assessed by 3D TEE in patients with aortic stenosis: impact of upper septal hypertrophy on measurements of Doppler-derived left ventricular stroke volume

BACKGROUND

It is unclear how upper septal hypertrophy (USH) affects Doppler-derived left ventricular stroke volume (SV) in patients with AS. The aims of this study were to: (1) validate the accuracy of 3D transesophageal echocardiography (TEE) measurements of the left ventricular outflow tract (LVOT), (2) evaluate the differences in LVOT geometry between AS patients with and without USH, and (3) assess the impact of USH on measurement of SV.

METHODS

In protocol 1, both 3D TEE and multi-detector computed tomography were performed in 20 patients with AS [aortic valve area (AVA) ≤ 1.5 cm²]. Multiplanar reconstruction was used to measure the LVOT short and long diameters in four parts from the tip of the septum to the annulus. In protocol 2, the same 3D TEE measurements were performed in AS patients (AVA ≤ 1.5 cm², n = 129) and controls (n = 30). We also performed 2D and 3D transthoracic echocardiography in all patients.

RESULTS

In protocol 1, excellent correlations of LVOT parameters were found between the two modalities. In protocol 2, the USH group had smaller LVOT short and long diameters than the non-USH group. Although no differences in mean pressure gradient, or SV calculated with the 3D method existed between the two groups, the USH group had greater SV calculated with the Doppler method (73 ± 15 vs. 66 ± 15 ml) and aortic valve area (0.89 ± 0.26 vs. 0.73 ± 0.24 cm²) than the non-USH group.

CONCLUSIONS

3D TEE can provide a precise assessment of the LVOT in AS. USH affects the LVOT geometry in patients with AS, which might lead to inaccurate assessments of disease severity.