Stress Echo in Morbid Obesity for Assessment of CAD
What is the clinical value of stress echocardiography among morbidly obese patients referred for assessment of suspected coronary artery disease (CAD)?
A prospective, multicenter observational study was conducted in two district hospitals and one tertiary center in London, United Kingdom. Individuals with body mass index ≥35 kg/m2 referred for stress echocardiography were evaluated. The percentage of patients with obstructive CAD on coronary angiography following abnormal stress echocardiography was assessed. Patient outcomes were assessed during follow-up for a composite endpoint of all-cause mortality, myocardial infarction, and late revascularization.
During a 13-month period, 209 morbidly obese patients (body mass index 39.3 ± 4.6 kg/m2) underwent stress echocardiography (126 [60%] dobutamine, 83 [40%] exercise); a contrast agent was used in 96% of patients. A diagnostic result was obtained in 200/209 (96%) patients. Of 32 (15%) patients with inducible ischemia, 25 underwent angiography. Of these, 22 (88%) had corresponding significant CAD, and 16 of those (77%) underwent revascularization. Conversely, only 2 of 157 patients (1.3%) with normal stress echocardiography underwent angiography, and none underwent revascularization. Over a mean follow-up period of 17.8 ± 5.4 months, there were nine clinical cardiac events. The annualized cardiac event rate after normal stress echocardiography was 0.95%. Events were more frequent in patients with inducible ischemia versus those without ischemia (5 of 32 [15.6%] vs. 4 of 153 [2.6%]; p = 0.002). Ejection fraction <50% (hazard ratio [HR], 9.5; 95% confidence interval [CI], 2.4-38.0; p = 0.002) and inducible ischemia (HR, 9.4; 95% CI, 2.5-35.8; p = 0.001) were predictors of outcome on univariable Cox regression analysis.
The authors concluded that contemporary stress echocardiography has excellent feasibility and positive predictive value, and results in appropriate risk stratification of symptomatic patients with significant obesity. Also, a normal stress echocardiogram portends an excellent outcome over the short- to intermediate-term in this high-risk patient population.
Noninvasive cardiac imaging may be compromised by poor image quality in morbidly obese patients. This study suggests that, using currently available imaging options (in this study, frequently including intravenous ultrasound contrast), stress (dobutamine and exercise) echocardiography could be reliably performed in the vast majority of morbidly obese patients. Test sensitivity was good. As with most studies on noninvasive imaging, test specificity is not reported (because most patients with a normal test are not referred for invasive testing); however, adverse clinical cardiac events were rare among patients with a negative stress echo. It is reasonable to conclude that, using currently available imaging techniques, morbid obesity should not be considered a contraindication to stress echocardiography.
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