Layer specific strain analysis and QTc interval in patients with STEMI and TIMI 3 early after percutaneous coronary intervention

Background

Heart rate-corrected (QTc) interval may increase in the setting of ST-elevation myocardial infarction (STEMI) even after complete reperfusion of the infarct-related artery. The remaining ischemia affects ventricular repolarization and may be associated with an increased susceptibility for malignant ventricular arrhythmias. Two-dimensional (2D) speckle tracking echocardiography (STE) is an angle-independent technique for evaluating myocardial function. The study aimed to analyze the layers specific strain using STE in patients after percutaneous coronary intervention (PCI) and find a possible correlation with QTc interval.

Methods

74 patients with STEMI and TIMI 3 flow after PCI were enrolled. The study did not include patients with bundle branch block, pacing, or treated with drugs that could increase the QTc interval. The evaluation consisted of clinical examination and laboratory tests. 12 leads electrocardiography evaluated QTc interval. Echocardiographic acquisitions were performed in the first 24–48 hours after PCI, and data were analyzed on the workstation. The global longitudinal strain was measured from apical views, at the level of the endocardium GLSAvgEndo, transmural GLSAvg, epicardium GLSAvgEpi; the difference bewtwen endocardium and epicardium longitudinal strain: GLSAvgEndo-GLSAvgEpi. Layer-specific GLS values were measured as the average of the longitudinal strain of 17 LV segments at each individual layer (Figure 1).

Results

Patients were diveded in two groups: the first included 32 patients with a single vessel disease (43.24%) and the second, 42 patients (56.75%) with multiple vessel damage, but without other indication for revascularization except the culprit lesion. Values for layers strain and QTc interval in the first group were: GLSAvgEndo: −16.2 (SD 2.98, CV 0.18), GLSAvg: −11.46 (SD 6.98, CV 0.6), GLSAvgEndo-GLSAvgEpi: 3.54 (DS 1.06, CV 0.29), QTc: 452.5 (SD 22.65, CV 0.05) and in the second group: GLSAvgEndo: −13.22 (SD 4.01, CV 0.3), GLSAvg: −11.3 (SD 3.39, CV 0.29), GLSAvgEndo-GLSAvgEpi: 3.47 (CV 1.28, CV 0.37), QTc: 490ms (SD 43.07, CV 0.08). QTc interval correlated with and layers strain in the first group: GLSAvgEndo: r=0.56, GLSAvg: r=0.67, GLSendo-GLSepi: r=0.54, and in the second group: GLSAvgEndo: r=0.73, GLSAvg: r=0.75, GLSAvgEndo-GLSAvgEpi: r=0.62.

Conclusions

1. The present study identified decreased longitudinal strain in all myocardial layers in the first days after STEMI, even after a successful PCI. 2. Alterations of QTc dynamicity were more frequent in patients with multivessel lesions 3. The electrical instability related by QTc interval correlated with the myocardial tissue damage related by STE. The correlation was more evident in patients with multivessel disease, even with remaining nonsignificant lesions, suggesting an ongoing process of microcirculatory perfusion damage.

Funding Acknowledgement

Type of funding sources: None.

Thrombogenicity assessment of Pipeline, Pipeline Shield, Derivo and P64 flow diverters in an in vitro pulsatile flow human blood loop model

Flow diversion is a disruptive technology for the treatment of intracranial aneurysms. However, these intraluminal devices pose a risk for thromboembolic complications despite dual antiplatelet therapy. We report the thrombogenic potential of the following flow diversion devices measured experimentally in a novel human blood in-vitro pulsatile flow loop model: Pipeline™ Flex Embolization Device (Pipeline), Pipeline™ Flex Embolization Device with Shield Technology™ (Pipeline Shield), Derivo Embolization Device (Derivo), and P64 Flow Modulation Device (P64). Thrombin generation (Mean ± SD; μg/mL) was measured as: Derivo (28 ± 11), P64 (21 ± 4.5), Pipeline (21 ± 6.2), Pipeline Shield (0.6 ± 0.1) and Negative Control (1.5 ± 1.1). Platelet activation (IU/μL) was measured as: Derivo (4.9 ± 0.7), P64 (5.2 ± 0.7), Pipeline (5.5 ± 0.4), Pipeline Shield (0.3 ± 0.1), and Negative Control (0.9 ± 0.7). We found that Pipeline Shield had significantly lower platelet activation and thrombin generation than the other devices tested (p < .05) and this was comparable to the Negative Control (no device, p > .05). High resolution scanning electron microscopy performed on the intraluminal and cross-sectional surfaces of each device showed the lowest accumulation of platelets and fibrin on Pipeline Shield relative to Derivo, P64, and Pipeline. Derivo and P64 also had higher thrombus accumulation at the flared ends. Pipeline device with Phosphorylcholine surface treatment (Pipeline Shield) could mitigate device material related thromboembolic complications.

Ultra-thin resin embedding method for scanning electron microscopy of individual cells on high and low aspect ratio 3D nanostructures

The preparation of biological cells for either scanning or transmission electron microscopy requires a complex process of fixation, dehydration and drying. Critical point drying is commonly used for samples investigated with a scanning electron beam, whereas resin-infiltration is typically used for transmission electron microscopy. Critical point drying may cause cracks at the cellular surface and a sponge-like morphology of nondistinguishable intracellular compartments. Resin-infiltrated biological samples result in a solid block of resin, which can be further processed by mechanical sectioning, however that does not allow a top view examination of small cell-cell and cell-surface contacts. Here, we propose a method for removing resin excess on biological samples before effective polymerization. In this way the cells result to be embedded in an ultra-thin layer of epoxy resin. This novel method highlights in contrast to standard methods the imaging of individual cells not only on nanostructured planar surfaces but also on topologically challenging substrates with high aspect ratio three-dimensional features by scanning electron microscopy.