Usefulness of post-systolic index in facilitating stratification of risk in patients with intermediate- or low-risk non-ST-segment elevation acute coronary syndrome.

Background: Although there is reportedly a usefulness of left ventricular global longitudinal strain (LV GLS) on 2D speckle-tracking echocardiography in excluding significant coronary artery disease (CAD) in suspected intermediate- or low-risk non-ST-segment elevation-acute coronary syndrome (NSTE-ACS), the efficacy of post-systolic index (PSI) in this context is yet unknown. Therefore, we explored the usefulness of PSI in facilitating stratification of risk in patients with intermediate- or low-risk NSTE-ACS.

Methods and results: We assessed 50 consecutive patients suspected of intermediate- or low-risk NSTE-ACS, and finally analyzed 43 patients whose echocardiographic images were suitable for strain analysis. All patients underwent CAG. Among the 43 analyzed patients, 26 had CAD, and 21 underwent percutaneous coronary intervention (PCI). Patients with CAD had higher PSI (25% [20.8-40.3%] vs 15% [8.0-27.5%], P = 0.007). Receiver-operator characteristic curve analysis identified that a PSI of > 20% detected performance of PCI (sensitivity 80.7%, specificity 70.6%, area under curve [AUC] 0.72, 95% confidence interval [CI] 0.57-0.88). Moreover, the AUC obtained using the GRACE risk score was 0.57 (95% CI 0.39-0.75), and increased to 0.75 (95% CI 0.60-0.90) when PSI and LV GLS were added. Thus, the addition of PSI and LV GLS improved the classification of performance of PCI (net reclassification improvement [95%CI] 0.09 [0.0024-0.18], P = 0.04).

Conclusions: Post-systolic index is a useful parameter that can facilitate stratification of risk in patients with intermediate- or low-risk NSTE-ACS. We recommend measuring PSI in routine clinical practice.