What Our Eyes See Is Not Necessarily What Our Heart Feels

• Published in: Cardiology Vol. 109; no. 2; pp. 122 - 125
• Main Authors: Pibarot, Philippe, Larose, Éric
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland S. Karger AG 01.01.2008
• Subjects: Aortic Valve - diagnostic imaging; Aortic Valve - pathology; Aortic Valve Stenosis - diagnostic imaging; Aortic Valve Stenosis - pathology; Aortic Valve Stenosis - physiopathology; Cardiology; Coronary vessels; Echocardiography, Doppler; Editorial Comment; Hemodynamics; Humans; Magnetic Resonance Imaging; Medical imaging
• ISSN: 0008-6312; 1421-9751; 1421-9751
• DOI: 10.1159/000105553

Sorry, there is no abstract. Read the first few lines of the text instead! The accurate assessment of hemodynamic significance is crucial for clinical decision making in patients with aortic stenosis (AS) [1]. Over the past decades, echocardiography has become the clinical standard for the evaluation of AS severity and the most frequently used index for this purpose is the aortic valve area (AVA). According to ACC/AHA recommendations [2], the stenosis is considered mild if the AVA is >1.5 cm2, moderate if less than or equal to 1.5 cm2 and >1.0 cm2, and severe if less than or equal to 1.0 cm2. The AVA can be measured by planimetry on the bidimensional images obtained by transthoracic (TTE) or transesophageal (TEE) echocardiography. It can also be measured by Doppler echocardiography (Doppler TTE) with the use of the continuity equation. Unfortunately, the accuracy of the echocardiographic measurement of AVA may be affected by several factors. For example, inadequate acoustic windows hinder accurate measurements in up to 10% of subjects. Furthermore, bright echoes and shadowing caused by the valvular calcifications present in many patients with severe AS may render difficult or unreliable the planimetric measurement of the valve orifice area. When using the continuity equation method, the AVA may be overestimated if the Doppler beam is not well aligned with the direction of the transvalvular flow jet. Moreover, patients with severe AS generally have a marked concentric left ventricular (LV) hypertrophy that is often associated with a protrusion of the interventricular septum into the LV outflow tract. This may cause a subvalvular acceleration of the flow and thus an overestimation of the AVA. On the other hand, an underestimation of the left ventricular outflow tract diameter may lead to an underestimation of the AVA. Alternatively, the AVA can be measured by catheterization with the use of the Gorlin formula. Unfortunately, this method is invasive and is associated with a substantial risk of cerebral embolism in the presence of severe AS [3, 4]. Moreover, it is also subject to significant measurement errors that may be related to nonsimultaneous recording of LV and aortic pressures (pullback method), to inaccurate measurement of transvalvular flow, and to the occurrence of reverse pressure gradient at the end of systolic ejection [1, 4, 5]. There is clearly much room for improvement, creating a strong impetus for the development of new noninvasive methods that could provide an accurate estimate of the AVA in AS patients. Such a method would be particularly useful in the situations where the echocardiographic measurement of the AVA is not feasible or is potentially inaccurate or when there are inconsistencies between the measured AVA and the symptomatic status of the patient. Cardiovascular magnetic resonance imaging (CMR) is particularly appealing because of its ability to noninvasively measure precisely and reproducibly cardiac anatomy and physiology. Cine sequences such as the steady-state free-precession method provide superior temporal and spatial resolution, with less susceptibility to blood flow artifacts and shorter scan times compared to previous sequences. Furthermore, CMR is appealing compared to Doppler echocardiography because of its ability to image the valve and measure blood flow velocities and derive pressure gradients in precise scan planes, rendering the technique less susceptible to 'interrogation angle error'. Additionally, imaging is not impaired by 'poor window quality' and much less susceptible to artifacts associated with calcified AS. Like echocardiography, CMR offers a complete assessment including cardiac function and chamber dimensions, with the added ability of accurately reporting ventricular mass. It must be noted, however, that in its current iteration CMR has not yet reached the rapid real-time processing abilities of Doppler ultrasound for which TTE remains the foremost screening tool available for initial assessment of valvular disease. Copyright [copy 2006 S. Karger AG, Basel