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Echocardiography. 2014 Mar;31(3):340-6. doi: 10.1111/echo.12372. Epub 2013 Oct 15.

Prognostic value of treadmill stress echocardiography at extremes of exercise performance: submaximal <85% maximum predicted heart rate versus high exercise capacity ≥ 10 metabolic equivalents.

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  • 1Valley Health System, Ridgewood, New Jersey.

Abstract

BACKGROUND:

Submaximal stress testing or achieving <85% maximum predicted heart rate (MPHR) may lead to nondiagnostic results and indeterminate outcomes. High exercise capacity (≥ 10 metabolic equivalents, METS) is a predictor of favorable prognosis. The purpose of this study was to evaluate the prognostic value of submaximal or high exercise capacity stress echocardiography.

METHODS:

We evaluated 1781 patients (55 ± 13 years; 59% male) undergoing treadmill stress echocardiography divided into 811 patients with submaximal (<85% MPHR) and 970 patients with high exercise capacity (≥ 10 METS). Resting left ventricular ejection fraction and regional wall motion were assessed. The left ventricle was divided into 16 segments and scored on 5-point scale of wall motion. Abnormal stress echocardiography was defined as stress-induced ischemia (wall-motion score of ≥ 1 grade). Follow-up (3.3 ± 1.5 years) for nonfatal myocardial infarction (MI) (n = 40) and cardiac death (n = 52) were obtained.

RESULTS:

By univariate analysis, echocardiographic variables of ejection fraction, peak wall-motion score index (WMSI) and number of new ischemic wall-motion abnormalities were significant predictors of cardiac events. Cumulative survival was significantly worse in patients with abnormal (ischemic) versus normal (nonischemic) stress echocardiography in submaximal (4.4%/year vs. 1.3%/year, P < 0.0001) and high exercise capacity (1.5%/year vs. 0.2%/year, P < 0.0001) studies. Multivariate Cox proportional hazards analysis identified number of new ischemic wall-motion abnormalities as the strongest predictor of cardiac events (P < 0.05) in both groups.

CONCLUSIONS:

Despite normal stress echocardiography, the inability to achieve 85% MPHR conferred a higher, intermediate cardiac event rate of 2.9%/year. The ability to achieve 9 minutes (≥ 10 metabolic equivalents, METS) conferred an overall low cardiac event rate of 0.4%/year. However, the absence or presence of ischemia by stress echocardiography was able to further risk stratify patients with either submaximal or high exercise capacity studies.

KEYWORDS:

echocardiography; exercise capacity; prognosis; stress

PMID:
24304167
DOI:
10.1111/echo.12372
[PubMed - indexed for MEDLINE]
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