Left Ventricular Strain from Myocardial Perfusion Positron Emission Tomography imaging: Method Development and Comparison to 2-Dimensional Echocardiography

Abstract

Objectives: The aim of this study was to develop a measure of longitudinal, radial, and circumferential myocardial strain at rest and during pharmacologic stress using ⁸²Rb-positron emission tomography (PET) electrocardiography-gated myocardial perfusion imaging (MPI). Methods: We retrospectively identified 80 patients that underwent rest/regadenoson-stress CT-attenuation corrected ⁸²Rb PET and had a standard resting transthoracic echocardiogram (TTE) with global longitudinal strain analysis within 3 months. A method was developed to compute strain from PET MPI in the longitudinal, radial, and circumferential directions at stress and at rest. PET MPI derived strain and LV function were compared to resting TTE measures as the clinical “reference standard,” respectively. Inter-observer agreement of PET MPI strain and left ventricular ejection fraction (LVEF) processing were reported. Results: Longitudinal strain assessed with resting TTE GLS showed good correlation with PET MPI at stress (r = 0.68, P < .001) and rest (r = 0.58, P <.001). Resting TTE GLS was also correlated with PET MPI radial strain at stress (r = -0.70, P < .001) and at rest (r = -0.59, P < .001), and with circumferential strain at stress (r = 0.67, P < .001) and at rest (r = 0.69, P < .001). LVEF showed good correlated between resting TTE and PET MPI at stress (r = 0.83, P < .001) and at rest (r = 0.80, P < .001). The Bland-Altman indicated a positive bias of TTE GLS compared to PET MPI longitudinal strain at stress (mean difference = 5.1%, 95%CI = (-2.5,12.7)) and rest (mean difference = 4.2%, 95%CI = (-4.3,12.8)). Reproducibility of PET MPI longitudinal strain showed good agreement at stress (CCC = 0.73, P < .001) and rest (CCC = 0.74, P < .001) with the Bland-Altman showing a small bias in the longitudinal direction at stress (mean difference = 0.2 %) and rest (mean difference = -1.0 %). Conclusion: Strain measured with PET MPI using a novel automated technique correlated well with resting GLS strain obtained by TTE and the measure is reproducible. Strain from PET MPI should be investigated further to establish normal ranges and assess its value in routine clinical practice.