Prediction for Improvement and Remodeling in First-Onset Myocardial Infarction by Speckle Tracking Echocardiography: Is Global or Regional Selection Better?

Ultrasound-targeted microbubble destruction-mediated Ang1 gene transfection improves left ventricular structural and sympathetic nerve remodeling in canines with myocardial infarction

Background

The present study aimed to determine whether ultrasound-targeted microbubble destruction (UTMD)-mediated angiopoietin 1 (Ang1) gene transfection can improve angiogenesis and potentially reverse left ventricular (LV) structural and sympathetic nerve remodeling in canines with myocardial infarction (MI).

Methods

Thirty dogs were randomly divided into groups (n=10/group) as follows: the MI group (MI dogs without UTMD treatment), the UTMD group (MI dogs with UTMD-mediated negative control plasmid treatment), and the UTMD-Ang1 group (MI dogs with UTMD-mediated Ang1 plasmid treatment). LV dimensions, systolic function, and synchrony were used to reflect the structural remodeling. The density of tyrosine hydroxylase (TH)- and growth-associated protein 43 (GAP43)-positive nerve fibers were calculated to assess the sympathetic nerve remodeling.

Results

One month after treatment, the UTMD-Ang1 group showed lower LV end-diastolic dimension (LVEDD: 31.2±2.3 mm) and higher LV ejection fraction (LVEF: 44.6%±4.3%) than the MI group (LVEDD: 34.5±2.2 mm, t=2.282, P=0.014; LVEF: 37.3%±3.1%, t=3.718, P=0.003) and the UTMD group (LVEDD: 34.1±2.8 mm, t=2.264, P=0.040; LVEF: 39.3%±4.5%, t=2.408, P=0.030). LV synchrony was higher in the UTMD-Ang1 group compared with the MI group by 2-dimensional speckle-tracking echocardiography. Angiogenic density was higher in the UTMD group than the MI group but was highest in the UTMD-Ang1 group according to immunohistochemistry of CD31 and α-smooth muscle actin staining. The density of TH- and GAP43-positive nerve fibers were decreased in the UTMD-Ang1 group (TH: 1,928.2±376.6 μm²/mm²; GAP43: 2,090.8±329.2 μm²/mm²) compared with the MI group (TH: 2916.5±558.4 μm²/mm², t=4.069, P=0.001; GAP43: 3,275.4±548.6 μm²/mm², t=5.153, P=0.000) and the UTMD group (TH: 2,552.7±408.1 μm²/mm², t=3.181, P=0.007; GAP43: 2,630.5±419.3 μm²/mm², t=2.863, P=0.013). The relative Ang1 and sarcoplasmic reticulum Ca²⁺-ATPase 2a protein levels were significantly higher in the UTMD-Ang1 group than the UTMD and MI groups by Western blot, while the phospholamban levels exhibited the opposite trend. Plasma norepinephrine and N-terminal pro-B-type-natriuretic peptide were significantly reduced in the UTMD-Ang1 group from day 1 to 1 month after MI.

Conclusions

UTMD-mediated Ang1 transfection can promote angiogenesis, reverse LV structural and sympathetic nerve remodeling, and improve LV synchrony after MI.

Layer-Specific Strain for Long-Term Outcome Prediction After First-Onset Myocardial Infarction

Many studies have reported the prognostic value of global strain obtained with speckle tracking echocardiography (STE) in patients with acute myocardial infarction (AMI). However, as a novel method derived from STE, layer-specific strain has seldom been evaluated with respect to prediction of AMI outcomes. We sought to investigate the predictive value of layer-specific strain and whether it has incremental value compared with conventional parameters, such as left ventricular ejection fraction and wall motion score index, and STE parameters. Our study was prospective. Ninety-two patients with first-onset AMI were enrolled and underwent echocardiography before coronary intervention for analysis of global and layer-specific strain. Cox proportional hazard ratio (HR) and receiver operating characteristic curve analyses were performed for the prediction of cardiac events and cardiac death. Fifty-three patients have had cardiac events during follow-up. Endocardial longitudinal strain has received relatively higher HRs for risk predictions of both cardiac events (HR = 1.69) and cardiac death (HR = 3.21) adjusted with clinical data. The areas under the receiver operating characteristic curves of the longitudinal strain at the endocardial layer from layer-specific strain were higher than those of global strain and conventional parameters for cardiac event prediction (p ˂ 0.05, all). Layer-specific strain is valuable for cardiac risk prediction after infarction and has incremental values in addition to conventional and global STE parameters. Myocardial damage at the endocardial layer was closely related to outcomes of AMI patients at long-term follow-ups.