Prognostic Value of Exercise Echo in Asymptomatic Aortic Stenosis
What is the prognostic value of stress echocardiographic data in patients with moderate or severe asymptomatic aortic stenosis (AS), in addition to standard physiologic and electrocardiographic stress parameters?
Patients with asymptomatic, moderate, or severe AS (mean pressure gradient [MPG] ≥20 mm Hg) who were referred for stress echocardiography at a single French center from 2005-2014 were enrolled. Patients with left ventricular ejection fraction (LVEF) <50%, estimated systolic pulmonary artery pressure (SPAP) >50 mm Hg, and other valve dysfunction of moderate or greater severity were excluded. Stress echocardiography was performed with a semi-supine bicycle. Abnormal exercise results, including occurrence of symptoms (dyspnea, angina, or syncope), fall in systolic blood pressure or rise <20 mm Hg, ST-segment depression ≥2 mm, or sustained ventricular arrhythmia prompted referral for aortic valve replacement (AVR). All patients without these findings were conservatively managed and followed. Abnormal stress echocardiographic results were defined as: 1) MPG increase ≥20 mm Hg, 2) SPAP >60 mm Hg at peak exercise, 3) reduction in LVEF, or 4) occurrence of regional wall motion abnormalities. The primary endpoint was a composite of AS-related events (development of symptoms or heart failure) and occurrence of AVR.
The study enrolled 148 patients (74% male, mean age 64 ± 13 years), of whom 36 (24%) had abnormal exercise results and were referred for AVR. Of the other 112 patients who were managed conservatively, 38 (34%) had abnormal stress echocardiographic results; 15 (41%) had a >20 mm Hg increase in MPG, 25 (66%) had a SPAP >60 mm Hg at peak exercise, and no patients had a drop in LVEF or occurrence of regional wall motion abnormalities. Mean follow-up for conservatively managed patients was 14 ± 8 months. A total of 30 patients (79%) met the primary endpoint. Patients with resting MPG ≥40 mm Hg were less likely to have event-free survival (p = 0.01). Exercise-induced MPG increase ≥20 mm Hg and peak SPAP >60 mm Hg were not significantly predictive of outcome.
This study does not support use of exercise echocardiographic assessment, in addition to standard exercise stress testing, for prognostication in moderate to severe asymptomatic AS.
Limitations of this study include small sample size, lack of blinding of clinicians, and limited feasibility of peak SPAP measurement (only 58%) as is common in real-world settings. Changes in LVEF with stress were not quantified. These results contradict findings of prior studies, which form the basis of the European Society of Cardiology IIb guideline recommendation that AVR may be considered in patients with exercise-induced MPG increase >20 mm Hg. As MPG increase is mediated by both valvular characteristics (changes in mobility and compliance) and myocardial characteristics (changes in inotropy and chronotropy), future studies isolating the relative contributions of these factors may be informative.
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