Assessment of aortic valve disease - a clinician oriented review

Abstract

Aortic valve disease [aortic stenosis (AS) and aortic regurgitation (AR)] represents an important global health problem; when severe, aortic valve disease carries poor prognosis. For AS, aortic valve replacement, either surgical or interventional, may provide definite treatment in carefully selected patients. For AR, valve surgery (either replacement or - in selected cases - aortic valve repair) remains the gold standard of care. To properly identify those patients who are candidates for surgery, the clinician has to carefully assess the severity of valve disease with an understanding of the potential pitfalls involved in these assessments. This review focuses on the practical issues concerning the evaluation of patients with AS and AR from a general cardiologist's perspective. The most important issues regarding the documentation of the severity of AS and AR are summarized. More specific issues, such as the role of stress echocardiography, other imaging techniques and details regarding the treatment options (medical, surgical, or interventional), are mentioned briefly.

Keywords: Aortic regurgitation; Aortic stenosis; Echocardiography; Evaluation; Treatment.

Figure 1

Relationship between flow, area and velocity. Calculation of the aortic valve area (AVA) based on the continuity equation. Flow (mL) equals the cross-sectional area (cm²) of the vessel multiplied by the mean flow velocity through that cross-sectional area during a period of time [measured as velocity-time-integral, VTI (cm)]. The flow is constant throughout the length of the vessel without ramifications. Thus, at the aortic valve level, the flow below the valve (in the left ventricular outflow tract, LVOT) equals flow through the aortic valve. Therefore, the AVA equals the LVOT area multiplied by the mean flow velocity through the LVOT area during ejection [LVOT velocity-time-integral, VTI_LVOT (cm)] divided by the transaortic mean flow velocity during ejection [transaortic velocity-time-integral, VTI_Ao (cm)]. The LVOT area, given the theoretical circular shape of the LVOT, is calculated by measuring its internal diameter [D_LVOT (cm)]. A: Area; V: Velocity; D_LVOT: Left ventricular outflow tract diameter; VTI: Velocity-time-integral.

Figure 2

The role of dobutamine stress echocardiography in diagnosing low-flow, low-gradient/low-ejection fraction severe[24]. LVEF: Left ventricular ejection fraction; CT: Computed tomography; AVR: Aortic valve replacement; AVA: Aortic valve area; AS: Aortic stenosis.

Figure 3

Classification of severe aortic stenosis with preserved left ventricular ejection fraction based on flow and transaortic pressure gradients[29]. iSV: Indexed stroke volume; NF: Normal flow; LF: Low flow; HG: High gradient; LG: Low gradient; AVA: Aortic valve area; AS: Aortic stenosis.