Incremental value of strain rate imaging to wall motion analysis for prediction of outcome in patients undergoing dobutamine stress echocardiography

Background - Wall motion score at dobutamine stress echocardiography is an independent predictor of mortality. We sought to determine whether quantification of DSE by strain rate imaging was incremental to wall motion score for predicting outcome. Methods and Results - In 646 patients undergoing dobutamine stress echocardiography for the evaluation of known or suspected coronary disease, customized software was used to automatically measure peak systolic strain rate (SRs) and end-systolic strain (Se-s) in 18 segments. Results were expressed as the number of abnormal segments and the mean SRs and S-es per patient. All-cause mortality was identified over 7 years of follow-up (mean, 5.2 +/- 1.5 years). Contributions of clinical, wall motion, and SRs and S-es data to outcome were analyzed with Cox models, which also were used to define cut points for SRs and S-es. Ischemia (new or worsening wall motion abnormalities) was detected in 45%, and 39% had a previous myocardial infarction. In patients with no ischemia, annualized mortality without and with previous myocardial infarction were 2% and 3% compared with 5% in patients with ischemia. Peak wall motion score index, mean SRs, segmental S-es, and segmental SRs were all predictors of mortality, but only segmental SRs (hazard ratio, 3.6; 95% CI, 1.7 to 7.2) was independently predictive. In sequential Cox models, the model based on clinical data (overall chi(2), 12.7) was improved by peak wall motion score index (18.4, P = 0.002) and further increased by either segmental SRs (31.8, P < 0.001) or mean SRs (25.7, P = 0.009). Conclusions - Segmental analysis by SRs, derived from automated strain rate imaging analysis of dobutamine stress echocardiography response, offers prognostic information that is independent and incremental to standard wall motion score index.