Doppler Echocardiographic Quantitation of Aortic Valve Stenosis: A Science in Constant Evolution

Aliased Flow Signal Planimetry by Cardiovascular Magnetic Resonance Imaging for Grading Aortic Stenosis Severity: A Prospective Pilot Study

Objectives: Transthoracic echocardiography (TTE) is the standard technique for assessing aortic stenosis (AS), with effective orifice area (EOA) recommended for grading severity. EOA is operator-dependent, influenced by a number of pitfalls and requires multiple measurements introducing independent and random sources of error. We tested the diagnostic accuracy and precision of aliased orifice area planimetry (AOAcmr), a new, simple, non-invasive technique for grading of AS severity by low-VENC phase-contrast cardiovascular magnetic resonance (CMR) imaging. Methods: Twenty-two consecutive patients with mild, moderate, or severe AS and six age- and sex-matched healthy controls had TTE and CMR examinations on the same day. We performed analysis of agreement and correlation among (i) AOAcmr; (ii) geometric orifice area (GOAcmr) by direct CMR planimetry; (iii) EOAecho by TTE-continuity equation; and (iv) the "gold standard" multimodality EOA (EOAhybrid) obtained by substituting CMR LVOT area into Doppler continuity equation. Results: There was excellent pairwise positive linear correlation among AOAcmr, EOAhybrid, GOAcmr, and EOAecho (p < 0.001); AOAcmr had the highest correlation with EOAhybrid (R 2 = 0.985, p < 0.001). There was good agreement between methods, with the lowest bias (0.019) for the comparison between AOAcmr and EOAhybrid. AOAcmr yielded excellent intra- and inter-rater reliability (intraclass correlation coefficient: 0.997 and 0.998, respectively). Conclusions: Aliased orifice area planimetry by 2D phase contrast imaging is a simple, reproducible, accurate "one-stop shop" CMR method for grading AS, potentially useful when echocardiographic severity assessment is inconclusive or discordant. Larger studies are warranted to confirm and validate these promising preliminary results.

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 (SVI_Doppler) or biplane Simpson (SVI_Biplane) method. AVAI_Dopplerand AVAI_Biplaneoften show discrepancy due to differences between SVI_Dopplerand SVI_Biplane. 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 (AVA_Doppler<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. SVI_Dopplerwas significantly larger than SVI_Biplane(49±11 vs. 39±11 mL/m², P<0.01) and AVAI_Dopplerwas larger than AVAI_Biplane(0.51±0.15 vs. 0.41±0.14 cm²/m², P<0.01). An increase in (AVAI_Doppler- AVAI_Biplane) 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 AVAI_Doppleror AVAI_Biplaneenabled 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.

Multimodality Imaging for Discordant Low-Gradient Aortic Stenosis: Assessing the Valve and the Myocardium

Aortic stenosis (AS) is a disease of the valve and the myocardium. A correct assessment of the valve disease severity is key to define the need for aortic valve replacement (AVR), but a better understanding of the myocardial consequences of the increased afterload is paramount to optimize the timing of the intervention. Transthoracic echocardiography remains the cornerstone of AS assessment, as it is universally available, and it allows a comprehensive structural and hemodynamic evaluation of both the aortic valve and the rest of the heart. However, it may not be sufficient as a significant proportion of patients with severe AS presents with discordant grading (i.e., an AVA ≤ 1 cm² and a mean gradient <40 mmHg) which raises uncertainty about the true severity of AS and the need for AVR. Several imaging modalities (transesophageal or stress echocardiography, computed tomography, cardiovascular magnetic resonance, positron emission tomography) exist that allow a detailed assessment of the stenotic aortic valve and the myocardial remodeling response. This review aims to provide an updated overview of these multimodality imaging techniques and seeks to highlight a practical approach to help clinical decision making in the challenging group of patients with discordant low-gradient AS.

Quantification of aortic valve area: comparison of different methods of echocardiography with 3-D scan of the excised valve

Accurate determination of severity of aortic valve stenosis (AS) by aortic valve area (AVA) is essential for choosing the best treatment strategy. We compared AVA quantified by 4 different in vivo echocardiographic methods with AVA measured by 3D ex vivo scanning of the excised AV. The data on 38 patients who underwent aortic valve replacement were assessed. The AVA was determined by 4 echocardiographic methods of planimetry in 2D transesophageal echocardiography [planimetry (2D-TEE)], plainemetry by multiplanar reconstruction approach in 3D transesophageal echocardiography [MPR (3D-TEE)], and two continuity equation (CE) approaches; conventional CE (2D-TTE) in which left ventricular outflow tract [LVOT] area derived by LVOT diameter obtained in 2D transthoracic echocardiography and CE (3D-TEE) in which LVOT area obtained by 3D MPR. After the surgical removal of the AV, AVA was determined by 3D ex vivo scanning. Lowest AVA mean difference with 3D ex vivo scanning was found between CE (2D-TTE), followed by CE (3D-TEE). Planimetry (2D-TEE) in male patients as well as severely and non-severely calcified valves revealed a significant higher AVA mean difference with 3D ex vivo scanning than CE (2D-TTE) and CE (3D-TEE) methods. However, with a nonsignificant effect, CE (2D-TTE) and planimetry (2D-TEE) had the least mean difference with 3D ex vivo scanning possibly due to less frequent bicuspid AV in females. CE (2D-TTE) was more accurate than other methods of AVA calculation. Moreover, CE (3D-TEE) and MPR (3D-TEE) methods had acceptable accuracy in comparison with planimetry (2D-TEE) for definition of AS severity.

Evaluation of mechanical prosthetic valves: the role of three dimensional echocardiography in calculating effective orifice area in obese vs non-obese individuals

Calculation of effective orifice area (EOA) is crucial for the evaluation of prosthetic valve (PV) function and there is lack of data on the best method, particularly in obese patients, in whom two-dimensional (2D) transthoracic echocardiography (TTE) is cumbersome. We sought to compare two methods of calculating EOA through Continuity equation; one using standard 2D-TTE and other three-dimensional (3D) stoke volume (SV), in patients with bileaflet mechanical PV stratified by body mass index (BMI). On conventional TTE, SV mas measured using standard 2D derived data and 3D derived SV in 38 aortic and 62 mitral PV patients who were referred for further evaluation for mild/moderate symptoms of dyspnea. Patients were categorized with regard to transprosthetic flow into 'normal-flow' and 'high-flow' groups and several echocardiographic data including 2D and 3D EOA were compared. Rates of obesity (BMI ≥ 30) were similar within high and normal flow groups of mitral and aortic PV patients. Correlation and agreement of 2D and 3D EOA was sought in patients with and without obesity. After identifying patients with possible severe obstruction, ROC analysis was carried out to identify whether 2D and 3D derived EOA could discriminate those with obstruction. There was good correlation and agreement between two methods in patients without obesity in both mitral and aortic PV. In obese individuals, however, there was no correlation between 2D and 3D EOA; in whom echocardiographic criteria showing severe obstruction revealed that 3D EOA measurements were more accurate. ROC analysis supported that 3D EOA performs better to identify patients with obstructive characteristics. In patients with bileaflet PV, measurement of EAO by 3D derived SV yields more accurate results irrespective of BMI.

Estimation of Stroke Volume and Aortic Valve Area in Patients with Aortic Stenosis: A Comparison of Echocardiography versus Cardiovascular Magnetic Resonance

BACKGROUND

In aortic stenosis, accurate measurement of left ventricular stroke volume (SV) is essential for the calculation of aortic valve area (AVA) and the assessment of flow status. Current American Society of Echocardiography and European Association of Cardiovascular Imaging guidelines suggest that measurements of left ventricular outflow tract diameter (LVOTd) at different levels (at the annulus vs 5 or 10 mm below) yield similar measures of SV and AVA. The aim of this study was to assess the effect of the location of LVOTd measurement on the accuracy of SV and AVA measured on transthoracic echocardiography (TTE) compared with cardiovascular magnetic resonance (CMR).

METHODS

One hundred six patients with aortic stenosis underwent both TTE and CMR. SV was estimated on TTE using the continuity equation with LVOTd measurements at four locations: at the annulus and 2, 5, and 10 mm below annulus. SV was also determined on CMR using phase contrast acquired in the aorta (SV_CMR-PC), and a hybrid AVA_CMR-PC was calculated by dividing SV_CMR-PC by the transthoracic echocardiographic Doppler aortic velocity-time integral. Comparison between methods was made using Bland-Altman analysis.

RESULTS

Compared with the referent method of phase-contrast CMR for the estimation of SV_CMR-PC and AVA_CMR-PC (SV_CMR-PC 83 ± 16 mL, AVA_CMR-PC 1.27 ± 0.35 cm²), the best agreement was obtained by measuring LVOTd at the annulus or 2 mm below (P = NS), whereas measuring 5 and 10 mm below the annulus resulted in significant underestimation of SV and AVA by up to 15.9 ± 17.3 mL and 0.24 ± 0.28 cm², respectively (P < .01 for all). Accuracy for classification of low flow was best at the annulus (86%) and 2 mm below (82%), whereas measuring 5 and 10 mm below the annulus significantly underperformed (69% and 61%, respectively, P < .001).

CONCLUSIONS

Measuring LVOTd at the annulus or very close to it provides the most accurate measures of SV and AVA, whereas measuring LVOTd 5 or 10 mm below significantly underestimates these parameters and leads to significant overestimation of the severity of aortic stenosis and prevalence of low-flow status.

Possible predictive role of electrical risk score on transcatheter aortic valve replacement outcomes in older patients: preliminary data

Objectives

To evaluate the predicative power of the electrical risk score (ERS), a noninvasive and inexpensive test obtained by means of a standard 12-lead electrocardiogram (ECG), in a cohort of elderly patients who had undergone transcatheter aortic valve replacement (TAVR).

Methods

Survivors and non-survivors after TAVR at 1-year follow-up were compared in respect to the pre-procedural ERS as well as a number of other clinical and instrumental variables. ERS is composed of seven simple ECG markers: heart rate (>75 bpm); QRS duration (>110 ms); left ventricular hypertrophy (Sokolow–Lyon criteria); delayed QRS transition zone (≥ V4); frontal QRS-T angle (>90°); long QT_Bazett (>450 ms for men and >460 in women) or JT_Bazett (330 ms for men and >340 ms for women); and long Tpeak to Tend interval (T_p-e) (>89 ms). The trial was registered in ClinicalTrials.gov as NCT03145376.

Results

A total of 40 patients were evaluated. During the follow-up, the all-cause mortality rate was 25% (ten patients) with 15% of cardiovascular death (six patients). The ERS was the strongest predictor of all-cause (odds ratio 3.73, 95% CI: 1.44–9.66, P<0.05) or cardiovascular (odds ratio 3.95, 95% CI: 1.09–14.27, P<0.05) mortality. Receiver operating characteristic curves showed that ERS had the widest significant sensitivity-specificity area under the curve (AUC) predicting all-cause (AUC: 0.855, P<0.05) or cardiovascular mortality (AUC: 0.908, P<0.05).

Conclusion

ERS seems to be a useful noninvasive tool able to stratify the risk of mortality in 1-year follow-up of TAVR patients. These findings, however, require larger trials to be confirmed.

Misconceptions and Facts About Aortic Stenosis

Aortic stenosis is the most common valvular heart disease leading to intervention, and it is typically a disease of the elderly. Recent clinical advances have expanded the role of transcatheter aortic valve intervention in patients with severe aortic stenosis, making aortic valve intervention feasible and effective even in patients at intermediate, high, and prohibitive surgical risk. With the rapid advances in treatment, proper diagnosis becomes crucial for a wide range of patients with aortic stenosis: from "concordant" high-gradient aortic stenosis to "discordant" low-gradient aortic stenosis. The latter group commonly presents a clinical challenge requiring thoughtful and comprehensive evaluation to determine eligibility for aortic valve intervention. Providers at all levels should be familiar with basic diagnostic caveats and misconceptions when evaluating patients with possible aortic stenosis.