Original ArticleLeft Ventricular Outflow Tract Area Measurements by Planimetry Using Two-Dimensional Simultaneous Orthogonal Plane Imaging During Transesophageal Echocardiography
Introduction
LEFT VENTRICULAR OUTFLOW TRACT (LVOT) measurements have important clinical applications, including the accurate calculation of aortic valve area and stroke volume. Errors could therefore impact patient care and treatment decisions. The LVOT long has been assumed to be circular in its cross-section1 and echocardiography typically is used to determine its diameter. Computed tomography (CT), magnetic resonance imaging (MRI), and three-dimensional (3D) echocardiographic imaging have demonstrated an elliptically shaped LVOT in a majority of the population2, 3, 4 and in only a minority of patients. During two-dimensional transesophageal echocardiography (2D TEE), the LVOT is visualized frequently in its long axis and its area is calculated using the diameter (0.785×diameter squared). This diameter corresponds to the minor diameter of an ellipse and hence tends to underestimate the true cross-sectional area of an elliptical LVOT. The authors hypothesized that planimetric measurements of the LVOT in the short-axis view by 2D TEE was plausible and closely approximated 3D planimetric measurements. The goal of this study was to demonstrate the feasibility of obtaining a short-axis view of the LVOT and to directly measure the area using planimetry during 2D TEE.
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Methods
With IRB approval, 55 adult patients with no evidence of aortic stenosis who were undergoing intraoperative TEE for surgery were enrolled in the study. TEE images were acquired by physician anesthesiologists with advanced certification from the National Board of Echocardiography. LVOT image acquisition and assessment were performed in real time in the operating room using a standard surgical protocol. A 3D-matrix array TEE probe (iE33 or Epic 7; X7-2t; Philips Healthcare Inc., Andover, MA) was
Results
Of the 55 enrolled subjects, the LVOT area using 2D planimetry could be assessed in 94.5%. Three could not be assessed because of poor image quality and alignment of the LVOT and were excluded from the analysis. The assessable subjects were 48% male, with a median age of 61.5 years (range, 42-85 years). The median body surface area was 1.96 cm2 (range, 1.42-2.33 cm2) (Tables 1 and 2). Of the subjects undergoing cardiac surgery involving cardiopulmonary bypass, there were 33 coronary artery
Discussion
With advances in imaging technology, there are now multiple modalities well suited to imaging the LVOT, including CT angiography, magnetic resonance angiography, and echocardiography. No single modality is preferred for all patients or all clinical situations. The choice of imaging modality should be individualized to the patient’s clinical situation, diagnostic questions to be answered, and other factors, such as performer expertise and availability. Accurate LVOT area measurements are
Conclusion
The technique tested in this study appeared to provide a rapid and more accurate measurement of the LVOT area than when indirectly estimating the LVOT area under the assumption that the LVOT is circular, as is done customarily. Simultaneous orthogonal plane imaging enables visualization of the LVOT in the short axis, and planimetry of this live 2D image allows for a direct measurement of the area. In this study, the area measured using planimetry was greater in all subjects, thus providing
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Cited by (2)
Appraising the Left Ventricular Outflow Tract: An Ongoing Challenge
2021, Journal of Cardiothoracic and Vascular AnesthesiaA Review of the 2017 American Society of Echocardiography Guidelines for Evaluation of Aortic Stenosis: Considerations for Perioperative Echocardiography
2018, Journal of Cardiothoracic and Vascular AnesthesiaCitation Excerpt :Additional studies examining outcomes with patients diagnosed with AS based on 3D measurements are necessary to answer this question, and the current ASE guidelines do not provide clarity on this subject. The LVOT area can be determined using 3D TEE by obtaining a 2D midesophageal long-axis view.39 A 4-beat, full-volume electrocardiogram gated loop subsequently is saved and analyzed using 3D software.