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

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 (p>0.05); 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, p<0.001 and ß=3.2, 95% CI: 1.5–5.0, p<0.001, respectively) and >75% transmurality (ß=8.1, 95% CI: 4.8–11.4, p<0.001; ß=3.3, 95% CI: 1–5.9, p=0.002 and ß=10.1, 95% CI: 6.2–14.0, p<0.001, 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.