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Welcome to the European Society of Cardiology. Our mission: to reduce the burden of cardiovascular disease in Europe
 
01 Sep 2008

Imaging valve disease in 2008 

Albert Hagege 

Albert Hagege
Topics: Non-invasive imaging: Echocardiography, MR/CT, Nuclear
Session number: 1857-1858-1859-1860
Session title: Imaging valve diseases in 2008
Authors: Hagege, Albert (Paris, France)


Resting Echocardiography
James D Thomas (Cleveland Clinic, USA) nicely showed that resting echocardiography remains a major tool to evaluate valve diseases. Anatomy is accurately approached with 2D transthoracic (TTE) and transoesophageal (TEE) echocardiography, as the recent 3D TTE and TEE techniques with better planimetry of aortic/mitral stenosis and optimisation of left ventricular (LV) volumes and ejection fraction (EF) quantification. For quantification of stenosis, the mean pressure gradient approach using the Bernouilli equation and orifice area measurements using the continuity equation have been largely validated in clinical practice. Semi-quantitative evaluation of regurgitations using the colour jet area approach is subject to many pitfalls (underestimation of the severity for lateral mitral regurgitation - MR - impinging the atrial wall, gain- and scale-dependancy) while the different stroke volume methods are difficult to apply on a routine basis. The proximal convergence method based on the PISA measurement should be simplified for MR quantification : assuming a 100 mmHg for LA-LV pressure gradient and setting the colour aliasing around 40 cm/s, regurgitant orifice area (ROA) (mm²) = r²/2 (r being the first aliasing diameter) (Pu, JASE 2001).

Finally, guidance of interventions using 2D and most frequently 3D TEE is more and more widely used, in the operative room to optimize assessment of results of valve repair or myectomy, as well as in the cath lab during percutaneous mitral stenosis dilatation, closure device insertion or percutaneous implantation of aortic bioprosthesis for aortic stenosis (AS). Clearly, in all these cases, resting echo is the clear winner among all techniques.

Functional Assessment
Luc Pierard (Liège, BE) insisted on the growing role of stress echocardiography for assessing valve severity (Table I), particularly in the asymptomatic patient. In severe asymptomatic AS, exercise testing is a class IIb indication according to the AHA guidelines, and markers of worse prognosis have been indicated with exercise echocardiography (Table II & III). In the asymptomatic patient with AS, dobutamine echocardiography gives useful diagnostic and prognostic information. Concerning diagnosis, increased gradient with unchanged ROA signals fixed AS, while unchanged gradient with increased ROA > 0.3 cm² indicates pseudo severe AS. Concerning prognosis, presence of a contractile reserve is a validated predictor of good outcome after surgery, while the operative risk is increased in its absence.

In severe asymptomatic mitral stenosis (MS), indications for repair/surgery are severe exercise limitation, mean pressure gradient > 15 mmHg, systolic pulmonary artery pressure > 60 mmHg, capillary wedge pressure > 25 mmHg and significantly increased MR. In organic MR, a larger exercise end-systolic volume and an increase < 4% in post-exercise LVEF are markers of bad operative results. For ischemic MR, ROA at rest is not related to exercise ROA (while exercise ROA is related to the severity of dyspnea). Exercise echo might be more widely indicated before by-pass graft surgery when moderate MR is present at rest. In the asymptomatic patient with aortic regurgitation, the impact of the regurgitation on the LV at rest and exercise provides the main information. To conclude, functional assessment at exercise is not yet mandatory but is frequently useful.

Value of magnetic resonance imaging and computed tomography
Jean-Louis Vanoverschelde (Brussels, BE) underlined the recent interest for MRI and CT-scan techniques. These techniques are better than echo for measuring LV volumes and EF and allow visualisation of the coronary arteries (CT). Valve planimetry has been validated using MRI or CT in valve stenosis and gives accurate access to anatomical ROA. The phased-contrast imaging technique by CMR allows a very accurate measurement of velocity and gradient through a stenotic aortic valve. MRI using that technique is actually the gold standard for regurgitant volume measurement in aortic regurgitation. Finally, MRI and CT give also access to associated lesions (dilatation of the aortic root…), and aetiology (prolapse, leaflet restriction…).

Cardiac Catheterization: Limited Indication
Bernard Prendergast (Oxford, GB) insisted on the limited indication of cardiac catheterization in 2008. It must not be systematically performed according to current guidelines (ESC 2007). In the EuroHeart Survey registry (2001, published 2003), cardiac catheterization remained performed in 1/3 to 2/5 of all patients (mean 31%, 63% if surgery is indicated), in 51% of the cases to assess the valve disease severity and in 23% to assess LV function. These numbers are probably actually lower. It has to be underlined that the radiation exposure during the procedure is high (for the patient and for the cardiologist) and that silent brain emboli are not infrequent: among 101 patients explored for AS, 22 (22%) were found to have silent brain emboli by MRI, and 3 (3%) showed symptomatic stroke (Lancet 2003).

Table I: Why perform stress echo in valve diseases?

  • To unmask symptoms
  • To determine objectively the level of physical activity
  • To Stratify risk
  • In combination with resting echo

Table II: Interest of stress echo in aortic stenosis

  • Assessment of symptom severity

  • Assessment of valve disease severity
    • Pressure gradient
    • Aortic valve area
    • Ejection fraction
    • LV filling pressure
    • Severity of functional MR
    • Pulmonary artery pressure
  • Assessment of contractile reserve
    • Tissue Doppler imaging
    • 2D strain rate
  • Inducible myocardial ischemia

Table III: Prognostic indicators using exercise echo in AS

  •  New exercise ECG abnormalities
  • Increase in pressure gradient ≥ 18 mmHg
  • Signs of impaired contractile reserve
    • Absence of increase in LVEF
    • Decrease in global longitudinal strain (DTI)
  • Increased Em/Ea (indicating increased exercise LVEDP)
  • Biphasic response at exercise, with increased mean gradient at low level and secondary decreased gradient at peak exercise (indicating decreased contractile reserve +/- concomitant coronary artery disease).


Notes to editor
Webcast Webcasts of Presentations availableJ D Thomas , LA Pierard , BD Prendergast ,

This congress report accompanies a presentation given at the ESC Congress 2008. Written by the author himself/herself, this report does not necessarily reflect the opinion of the European Society of Cardiology.
References Pu M, Prior DL, Fan X, Asher CR, Vasquez C, Griffin BP, Thomas JD.
Calculation of mitral regurgitant orifice area with use of a simplified proximal convergence method: initial clinical application.
J Am Soc Echocardiogr. 2001;14(3):180-5

Omran H, Schmidt H, Hackenbroch M, Illien S, Bernhardt P, von der Recke G, Fimmers R, Flacke S, Layer G, Pohl C, Lüderitz B, Schild H, Sommer T.
Silent and apparent cerebral embolism after retrograde catheterisation of the aortic valve in valvular stenosis: a prospective, randomised study.
Lancet. 2003;361(9365):1241-6

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.