ABCDEG Stress Echocardiography in Aortic Stenosis

Abstract

Rest and stress echocardiography (SE) plays a pivotal role in the evaluation of valvular heart disease. The use of SE is recommended in valvular heart disease when there is a mismatch between resting transthoracic echocardiography findings and symptoms. In aortic stenosis (AS), rest echocardiographic analysis is a stepwise approach that begins with the evaluation of aortic valve morphology and proceeds to the measurement of the transvalvular aortic gradient and aortic valve area (AVA) using continuity equations or planimetry. The presence of the following three criteria suggests severe AS: AVA < 1.0 cm², a peak velocity > 4.0 m/s, or a mean gradient > 40 mmHg. However, in approximately one in three cases, we can observe a discordant AVA < 1 cm² with a peak velocity < 4.0 m/s or a mean gradient <40 mmHg. This is due to reduced transvalvular flow associated with LV systolic dysfunction (LVEF < 50%) defined as "classical" low-flow low-gradient (LFLG) AS or normal LVEF "paradoxical" LFLG AS. SE has an established role in evaluating LV contractile reserve (CR) patients with reduced LVEF. In classical LFLG AS, LV CR distinguished pseudo-severe AS from truly severe AS. Some observational data suggest that long-term prognosis in asymptomatic severe AS may not be as favorable as previously thought, offering a window of opportunity for intervention prior to the onset of symptoms. Therefore, guidelines recommend evaluating asymptomatic AS with exercise stress in physically active patients, particularly those younger than 70 years, and symptomatic classical LFLG severe AS with low-dose dobutamine SE. A comprehensive SE assessment includes evaluating valve function (gradients), the global systolic function of the LV, and pulmonary congestion. This assessment integrates considerations of blood pressure response, chronotropic reserve, and symptoms. StressEcho 2030 is a prospective, large-scale study that employs a comprehensive protocol (ABCDEG) to analyze the clinical and echocardiographic phenotypes of AS, capturing various vulnerability sources which support stress echo-driven treatment strategies.

Keywords: aortic stenosis; coronary flow reserve; echocardiography; left ventricular contractile reserve; stress echocardiography.

Figure 1

The ABCDEG protocol in AS. The entire test takes roughly 30 min to be completed, including the preparation phase and the written response. Step A and step C require the very same images. Step E requires only one electrocardiogram lead. Step B can be completed before starting the SE and in the early recovery phase. Step D requires peak diastolic Doppler evaluation of the mid-distal part of the left anterior descending coronary artery; evaluations should be performed at rest and peak stress. Step G requires the maximal and mean trans-aortic gradient and the integral flow in the outflow tract and involves assessment at rest and at peak stress. Modified from Ciampi Q et al. [3].

Figure 2

Rest and at peak stress of low doses of dobutamine SE. SVi: stroke volume index; COi: cardiac output index; AVA: aortic valve area.

Figure 3

Rest and at peak stress of low-dose of dobutamine SE. EDV: end-diastolic volume; ESV: end-systolic volume; LV EF: left ventricular ejection fraction; SBP: systolic blood pressure; AVPG: aortic valve peak gradient; NV: normal value.