Absolute assessment of aortic valve stenosis by planimetry using cardiovascular magnetic resonance imaging: Comparison with transœsophageal echocardiography, transthoracic echocardiography, and cardiac catheterisation

https://doi.org/10.1016/j.ejrad.2006.02.011Get rights and content

Abstract

Objective

The aims of this study were to investigate absolute assessment of aortic valve area (AVA), before surgery for aortic stenosis, using cardiovascular magnetic resonance (CMR) in comparison with transœsophageal echocardiography (TEE) and with effective AVA indirectly obtained by routine techniques i.e. transthoracic echocardiography (TTE) and cardiac catheterisation.

Materials and methods

Absolute AVA planimetry was performed by TEE and CMR steady state free precession sequences obtained through the aortic valvular plane. Effective AVA was calculated by the continuity equation in TTE and by cardiac catheterisation (Gorlin formula).

Results

Thirty-nine patients with aortic valve stenosis, mean age 71.7 ± 7.6 years, with a mean AVA of 0.93 ± 0.31 cm2 as measured by TEE, were enrolled in the study. Mean differences were: between CMR and TEE planimetry: d = 0.01 ± 0.14 cm2, between CMR and cardiac catheterisation: d = 0.05 ± 0.13 cm2, between CMR and TTE: d = 0.10 ± 0.17 cm2, between TTE and TEE: d = 0.10 ± 0.18 cm2, between TTE and cardiac catheterisation: d = 0.06 ± 0.16 cm2, and between TEE and cardiac catheterisation: d = 0.07 ± 0.13 cm2. Mean intraobserver and interobserver differences of CMR planimetry were d = 0.02 ± 0.07 cm2 and d = 0.03 ± 0.14 cm2, respectively.

Conclusion

CMR planimetry of the AVA is a noninvasive and reproducible technique to evaluate stenotic aortic valves and can be used as an alternative to echocardiography or cardiac catheterisation.

Introduction

Assessment of aortic stenosis severity is usually obtained indirectly by calculation of aortic valve area (AVA) using the continuity equation in transthoracic echocardiography (TTE) and Gorlin formula in cardiac catheterisation [1], [2], [3], [4]. Nevertheless, poor echocardiographic windows may compromise measurement accuracy [5], cardiac catheterisation present some risks [6], and Gorlin formula is limited by variations of the empirical constant [7], [8]. Being flow-dependent, indirect methods are invalidated in presence of LV systolic dysfunction or significant aortic regurgitation. Transœsophageal echocardiography (TEE) allows direct evaluation of AVA by planimetry of the orifice but is semi-invasive. Cardiac magnetic resonance (CMR) imaging has been used especially for LV systolic function measurements [9], [10]. New sequences such as true fast imaging steady state free precession (True FISP SSFP) images provide excellent blood-myocardium contrast [11], [12], [13]. To date, only few studies have been performed to evaluate the accuracy of CMR for measurement of stenotic valve areas by jet velocity mapping [14], [15], [16], [17] or by planimetry [12], [18], [19]. Only two of them were performed using True FISP SSFP sequences [12], [18].

Therefore, the aims our study were (1) to evaluate the ability of CMR using True FISP SSFP sequences to perform planimetry of the aortic valve in comparison with TEE planimetry (2) to compare absolute value of AVA to effective AVA evaluation obtained with routine clinical techniques, TTE and cardiac catheterisation.

Section snippets

Patients

The study group consisted in 39 consecutive patients with mild, moderate or severe aortic valve stenosis documented by TTE. They were clinically stable without symptoms that would have contraindicated TEE or CMR. Exclusion criteria were those for TEE (gastro-œsophageal pathology, haemodynamic instability), and CMR suitability (exclusion of metallic implant, severe claustrophobia, pacemaker, valvular prostheses contraindicated in CMR) [20], subvalvular outflow tract obstruction and rapid

Patient population

Twenty (33%) out of 59 consecutive patients were excluded of the study; 12 (20%) patients because of CMR contraindication (four patients with pacemakers, six with metallic implants, and two with severe claustrophobia) and 8 (13%) patients because of TEE contraindication or impossibility to perform the examination. Thirty-nine patients (mean 71.7 ± 7.6 years, ranging from 54 to 83 years) completed the CMR, TTE and TEE protocols. During cardiac catheterisation, the aortic valve was crossed by the

Discussion

This prospective study evaluated AVA area in patients with aortic stenosis using four different imaging techniques. It showed good accordance between CMR planimetry, TEE planimetry and AVA measured by cardiac catheterisation, and good CMR intraobserver and interobserver reproducibilities.

Previous studies have shown the potential for quantitative evaluation of valve stenosis by CMR [14], [15]. Sondergaard et al. used velocity-encoded CMR to estimate orifice area with good correlation with

Conclusion

This work shows that evaluation of AVA by CMR planimetry with new SSFP sequences is accurate, non-invasive and reproducible, and provides a powerful tool for evaluating aortic stenosis. CMR also offers high spatial resolution analysis of myocardial function. CMR planimetry seems particularly helpful in patients with discrepant findings by other modalities and could be an alternative to echocardiography or cardiac catheterisation in selected cases.

Acknowledgment

The investigators are indebted to the staff of the catheterisation laboratory for their help in collecting the data reported in this manuscript.

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