Evaluation of myocardial viability: a comparative study between parametric 15o water PET/CT imaging and speckle tracking echocardiography

Abstract Background Assessment of myocardial viability is important in patients with ischemic cardiomyopathy to guide revascularization decisions and provides prognostic information after acute myocardial infarction (AMI). 15o water PET myocardial perfusion imaging is established tool for detecting myocardial ischemia, but the value of 15o water PET in evaluating myocardial viability is incompletely understood. Purpose To evaluate the diagnostic performance of myocardial blood flow (MBF), relative MBF (rMBF), and perfusable tissue fraction (PTF) from 15o water PET in assessing myocardial viability determined by echocardiographic segmental longitudinal strain (LS) in patients with AMI. Methods We prospectively studied 31 patients (mean age 64 ± 9 years) with acute ST-elevation myocardial infarction and left ventricular ejection fraction (LVEF) 50% who underwent primary percutaneous coronary intervention. Echocardiography was performed 8 days after AMI on the same day as the 15o water PET scan (baseline) and repeated at the 6-month follow-up. Absolute MBF values from resting 15o water PET polar maps were normalized to the average MBF of the best-perfused coronary territory to generate rMBF. Myocardial segments were categorized into three groups according to myocardial infarction (MI) transmurality (0–50%, 51–75%, and 75%) based on predefined LS cutoff 1,2. PET-derived MBF, rMBF, and PTF were analyzed against transmurality to assess diagnostic performance using ROC analysis and logistic regression. Results Mean LVEF was 55.8 ± 6.8% at baseline and 57.5 ± 7.3% at follow-up (p0.05); Global LS was 14.9 ± 4.6% and 15.4 ± 3.9%, respectively (p 0.05). Mean resting MBF was 0.84 ± 0.19 ml/g/min. Based on segmental LS, 337 segments showed 0–50%, 115 segments 51–75% and 36 segments 75% MI transmurality. MBF and rMBF showed statistically significant differences between all three transmurality groups (p 0.001), while PTF was similar in segments with 0–50% and 51–75% transmurality (p = 0.5)(Table 1). In identifying segments with 50% MI transmurality, the AUCs were 0.683 for MBF, 0.659 for rMBF, and 0.584 for PTF (Figure 1A). In detecting segments with 75% MI transmurality, MBF, rMBF and PTF demonstrated high diagnostic performance with AUCs of 0.892, 0.805 and 0.870, respectively (Figure 1B). In multivariate models, MBF, rMBF and PTF remained independent predictors at both 50% (ß=1.8, 95% CI: 1.2–3.9, p=0.004; ß=2.5, 95% CI: 0.6- 3.1, p0.001 and ß=3.2, 95% CI: 1.5–5.0, p0.001, respectively) and 75% transmurality (ß=8.1, 95% CI: 4.8–11.4, p0.001; ß=3.3, 95% CI: 1–5.9, p=0.002 and ß=10.1, 95% CI: 6.2–14.0, p0.001, respectively). Conclusion Cardiac 15o water PET parameters—including MBF, rMBF and PTF, demonstrated comparable diagnostic accuracy for detecting myocardial viability. These findings suggest that integrating multiple PET-derived parameters may enhance the accuracy of viability assessment in patients with ischemic cardiomyopathy.