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Discordance in Grading Methods of Aortic Stenosis by Pre-Cardiopulmonary Bypass Transesophageal Echocardiography
George Whitener1, Jeff McKenzie, Igor Akushevich
1From the *Department of Anesthesiology, †Social Science Research Institute, and ‡Department of Biostatistics and Bioinformatics, Duke University, Durham, North Carolina.
Insights
Discordance in grading severe aortic stenosis (AS) is higher with transesophageal echocardiography (TEE) before surgery than with transthoracic echocardiography (TTE). This impacts patient assessment for aortic valve replacement.
Area of Science:
- Cardiology
- Echocardiography
- Cardiac Surgery
Background:
- Severe aortic stenosis (AS) is defined by aortic valve area (AVA) ≤1.0 cm² and mean gradient (ΔPm) ≥ 40 mm Hg.
- Discordance between AVA and ΔPm measurements can occur when classifying AS severity.
- Previous studies using transthoracic echocardiography (TTE) reported discordance in approximately one-third of patients.
Purpose of the Study:
- To investigate the rate of discordance between ΔPm and AVA measurements during pre-cardiopulmonary bypass (pre-CPB) transesophageal echocardiography (TEE).
- To compare this discordance rate with previously reported rates from TTE studies.
- To explore potential reasons for observed differences in discordance rates.
Main Methods:
- Retrospective analysis of pre-CPB TEE data from patients undergoing aortic valve replacement (2000-2012).
- Exclusion criteria included low ejection fraction, emergency surgery, repeat sternotomy, and moderate/severe mitral or aortic regurgitation.
- Patients were categorized by AS severity (mild, moderate, severe) based on AVA and ΔPm; discordance was defined as disagreement between classifications.
Main Results:
- Of 277 patients, 227 had AVA ≤ 1.0 cm²; 54% of these had a ΔPm < 40 mm Hg.
- The discordance rate (54%) during pre-CPB TEE was significantly higher than the 37% rate reported for TTE (P < 0.001).
- Patients with ΔPm < 40 mm Hg were more likely to have a discordant AVA (80%) compared to those with ΔPm ≥ 40 mm Hg (8%).
Conclusions:
- Pre-CPB TEE demonstrates a higher discordance rate in grading AS severity by ΔPm and AVA compared to TTE.
- The reasons for this increased discordance remain unclear, potentially involving general anesthesia, imaging modality differences, or inaccuracies in current grading cutoffs.
- Further investigation is needed to understand the clinical implications of these discrepancies in the pre-operative assessment of AS.
Background:
Current guidelines define severe aortic valve stenosis (AS) as an aortic valve area (AVA) ≤1.0 cm by the continuity equation and mean gradient (ΔPm) ≥ 40 mm Hg. However, these measurements can be discordant when classifying AS severity. Approximately one-third of patients with normal ejection fraction and severe AS by AVA have nonsevere AS by ΔPm when measured by preoperative transthoracic echocardiography (TTE). Given the use of positive pressure ventilation and general anesthesia in the pre-cardiopulmonary bypass (pre-CPB) period, we hypothesized that discordance between ΔPm and AVA during pre-CPB transesophageal echocardiography (TEE) would be higher than previously reported by TTE.
Methods:
We retrospectively examined pre-CPB TEE data for patients who had aortic valve replacement, with or without coronary artery bypass grafting, from 2000 to 2012. Patients were excluded if they had ejection fraction <55%, emergency surgery, repeat sternotomy, moderate or severe mitral regurgitation, or severe aortic regurgitation. Only patients with both pre-CPB AVA and ΔPm measurements were included. Patients were grouped according to severity (mild, moderate, and severe) by AVA or ΔPm. Discordance was defined as disagreement between severities based on either parameter.
Results:
A total of 277 patients met inclusion criteria. There were 227 patients with AVA ≤ 1.0 cm. The proportion of these patients with a ΔPm < 40 mm Hg was 54% (95% confidence interval, 47%-61%). The rate of discordance was significantly higher than the rate (37%; P < 0.001) found in previously reported analyses using TTE. Of the patients with a ΔPm ≥ 40 mm Hg, only 8% (n = 9/113) had a discordant AVA. In contrast, of the patients with ΔPm < 40 mm Hg, 80% (n = 131/164) had a discordant AVA.
Conclusions:
We confirmed our hypothesis that grading AS by ΔPm and AVA during pre-CPB TEE exhibits higher discordance than reported for TTE by others. It remains unclear whether these discrepancies reflect the effect of general anesthesia, imaging modality (TTE versus TEE) differences, inaccuracies in AS grading cutoffs when applied to pre-CPB TEE, or selection bias of the surgical population.
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