Moderate-to-Severe Aortic Stenosis and Three-Dimensional Echocardiography

Abstract

A 75-YEAR-OLD MAN with recent onset of heart failure presented with symptoms of shortness of breath and a 2-dimensional (2D) transthoracic echocardiographic (TTE) examination was performed for diagnosis. The TTE examination showed a dilated left ventricle with global hypokinesia and an ejection fraction of 30%. Based on the continuity equation and left ventricular outflow tract (LVOT) diameter (1.38 cm2), the aortic valve area (AVA) was calculated to be 1.3 cm2. Further assessment of the aortic valve revealed moderate aortic insufficiency, aortic valve calcifications, and a maximum transvalvular gradient of 24 mmHg. A cardiac catheterization also was performed that showed severe 2-vessel coronary artery disease. The patient was scheduled for coronary artery bypass graft surgery (CABG) and possible aortic valve replacement (AVR). His other medical history was notable for ischemic cardiomyopathy, hypertension, insulin-dependent diabetes mellitus, and anemia. A precardiopulmonary bypass transesophageal echocardiographic (TEE) examination was performed with an IE-33 ultrasound system (Philips Medical Systems, Andover, MA). The midesophageal aortic short-axis view showed a moderately calcified aortic valve with fusion of the right and noncoronary cusps. The LVOT diameter was measured in the midesophageal aortic long-axis view (2.2 cm) with a maximal velocity of 47 cm/s and a maximal transvalvular velocity of 2.2 m/s, with a peak transaortic valvular gradient of 19 mmHg (normal <20 mm Hg) (Fig 1, Fig 2). Based on the continuity equation, the AVA was calculated to be 0.82 cm2 (Fig 2). Subsequently, a 3-dimensional (3D) live zoom image of the LVOT was acquired. These data were analyzed with multiplanar reformatting in QLAB 8.1.2 (DICOM Analysis Software; Philips, Andover, MA). With planimetry of the “en face” LVOT view an area of 4.63 cm2 was obtained (Fig 3). This was in contrast to the LVOT area measured with 2D TEE (3.80 cm2). Compared with the 3D calculation, the LVOT area was underestimated by 26% based on the 2D method. Why is this a remarkable finding?Fig 2AVA calculation with the continuity equation using 2D obtained LVOT data.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Fig 3The planimetered LVOT area. (Color version of figure is available online.)View Large Image Figure ViewerDownload Hi-res image Download (PPT) It was important for the surgical decision making regarding AVR to have an accurate AVA. There were several notable echocardiographic challenges. There was 26% discordance in LVOT area between the 2D and 3D obtained data (Table 1). The LVOT area discordance led to an AVA discordance of 0.82 cm2 (2D data) versus 1.1 cm2 (3D data). Based on the 2D data, the aortic stenosis (AS) would have been classified as severe, whereas the 3D data would classify it as moderate.Table 1Different Methods Used to Calculate AVAMethod UsedAVATransthoracic echocardiography1.3 cm2 (LVOT = 6.03 cm2)2D TEE0.82 cm2 (LVOT = 3.80 cm2)3D TEE1.1 cm2 (LVOT = 4.63 cm2) Open table in a new tab Which AVA should be used for clinical decision making? Severe AS is an indication for AVR, whereas moderate stenosis could mandate a more conservative nonsurgical approach. The surgeons wanted clear advice whether there was an indication for AVR or not? The authors had established that the aortic valve was at least moderately stenotic; there was at least moderate aortic insufficiency; and there was significant aortic valve calcification (Fig 4), which is a predictor of accelerated progression of AS. Based on the patient's age (75 years), aortic valve calcifications (grade 3), preoperative AVA of 1.3 cm2, and the indication for CABG surgery, the patient would have been at high risk for disease progression to severe AS within 3 to 5 years. Hemodynamic deterioration in patients older than 50 with AS occurs more rapidly when there is concomitant coronary artery disease or valve calcification. Therefore, the authors decided to replace the aortic valve together with the CABG procedure. The postoperative recovery was uneventful. The patient was discharged in good condition 5 days later. Clinical decision making in patients with AS is dependent partially on an established classification system; hence, it is imperative to have accurate data available. The authors present a clinical challenge in which a discrepancy in AVA was found when 2D echocardiography was substituted by 3D echocardiographic interrogation of the LVOT. The classification of AS changed from severe to moderate when the 2D obtained LVOT area (π*r2) was replaced by 3D planimetered LVOT area in the continuity equation (26% change in area). The challenge in the present case was how to deal with this new information in the setting of surgical decision making.