Recovery of Hypoxic Regions in a Rat Model of Microembolism

OBJECTIVES

Endovascular treatment (EVT) has become the standard of care for acute ischemic stroke. Despite successful recanalization, a limited subset of patients benefits from the new treatment. Human MRI studies have shown that during removal of the thrombus, a shower of microclots is released from the initial thrombus, possibly causing new ischemic lesions. The aim of the current study is to quantify tissue damage following microembolism.

MATERIALS AND METHODS

In a rat model, microembolism was generated by injection of a mixture of polystyrene fluorescent microspheres (15, 25 and 50 µm in diameter). The animals were killed at three time-points: day 1, 3 or 7. AMIRA and IMARIS software was used for 3D reconstruction of brain structure and damage, respectively.

CONCLUSIONS

Microembolism induces ischemia, hypoxia and infarction. Infarcted areas persist, but hypoxic regions recover over time suggesting that repair processes in the brain rescue the regions at risk.

Granulocyte colony-stimulating factor attenuates myocardial remodeling and ventricular arrhythmia susceptibility via the JAK2-STAT3 pathway in a rabbit model of coronary microembolization

Background

Coronary microembolization (CME) has a poor prognosis, with ventricular arrhythmia being the most serious consequence. Understanding the underlying mechanisms could improve its management. We investigated the effects of granulocyte colony-stimulating factor (G-CSF) on connexin-43 (Cx43) expression and ventricular arrhythmia susceptibility after CME.

Methods

Forty male rabbits were randomized into four groups (n = 10 each): Sham, CME, G-CSF, and AG490 (a JAK2 selective inhibitor). Rabbits in the CME, G-CSF, and AG490 groups underwent left anterior descending (LAD) artery catheterization and CME. Animals in the G-CSF and AG490 groups received intraperitoneal injection of G-CSF and G-CSF + AG490, respectively. The ventricular structure was assessed by echocardiography. Ventricular electrical properties were analyzed using cardiac electrophysiology. The myocardial interstitial collagen content and morphologic characteristics were evaluated using Masson and hematoxylin-eosin staining, respectively.

Results

Western blot and immunohistochemistry were employed to analyze the expressions of Cx43, G-CSF receptor (G-CSFR), JAK2, and STAT3. The ventricular effective refractory period (VERP), VERP dispersion, and inducibility and lethality of ventricular tachycardia/fibrillation were lower in the G-CSF than in the CME group (P < 0.01), indicating less severe myocardial damage and arrhythmias. The G-CSF group showed higher phosphorylated-Cx43 expression (P < 0.01 vs. CME). Those G-CSF-induced changes were reversed by A490, indicating the involvement of JAK2. G-CSFR, phosphorylated-JAK2, and phosphorylated-STAT3 protein levels were higher in the G-CSF group than in the AG490 (P < 0.01) and Sham (P < 0.05) groups.

Conclusion

G-CSF might attenuate myocardial remodeling via JAK2-STAT3 signaling and thereby reduce ventricular arrhythmia susceptibility after CME.

Cutaneous Microembolism of Fingers and Toes

A macro vascular embolism is a well-known emergency. In contrast, cutaneous microembolism is a lesser known symptom. However, cutaneous microembolism of fingers and toes is a red flag symptom for vascular emergencies. The underlying cause may involve infectious, immunological, metabolic and physical disorders, coagulation disorders and malignancies. Early recognition can help to live safe.

Microembolism of single cortical arterioles can induce spreading depression and ischemic injury; a potential trigger for migraine and related MRI lesions

Increasing epidemiological evidence suggests an association between migraine with aura (MA) and cardiovascular events. There is experimental as well as clinical evidence implying cerebral microembolism as a potential trigger for MA attacks. Microembolism may also account for some of the ischemic MRI lesions more commonly observed in MA than in general population. Limited size of clinically-silent MRI lesions suggests isolated occlusion of a small vessel. However, it is not known whether selective thrombosis of a small arteriole (e.g. single mouse penetrating arteriole - PA), can induce cortical spreading depression (CSD), the putative cause of migraine aura and, hence, trigger an MA attack. For this, we mimiced thrombosis of a small vessel caused by microembolism by selectively occluding a PA just before diving into the cortex (radius; 10-25 µm) in the mouse. Clotting was induced with FeCl₃ applied focally over the PA by a glass micropipette for 3 min. DC potential changes were recorded and the alterations in cortical blood flow were monitored by laser speckle contrast imaging. Mice were kept alive for 1-4 weeks and brain sections were stained with H&E or luxol-fast blue to evaluate changes induced by PA occlusion. We found that single PA occlusion consistently triggered a CSD originating from the tissue around the PA soon after occlusion and induced delayed, small ischemic lesions within territory of the affected vessel a few weeks later. These findings suggest that cerebral microembolism can lead to MA attacks and may account for some of the silent brain lesions.

Microembolism after Endovascular Treatment of Unruptured Cerebral Aneurysms: Reduction of its Incidence by Microcatheter Lumen Aspiration

PURPOSE

Diffusion-weighted MR images (DWI) obtained after endovascular treatment of cerebral aneurysms frequently show multiple high-signal intensity (HSI) dots. The purpose of this study was to see whether we could reduce their incidence after embolization of unruptured cerebral aneurysms by modification of our coiling technique, which involves the deliberate aspiration of the microcatheter lumen right after delivery of each detachable coil into the aneurysm sac.

MATERIALS AND METHODS

From January 2011 to June 2011, all 71 patients with unruptured cerebral aneurysms were treated using various endovascular methods. During the earlier period, 37 patients were treated using our conventional embolization technique (conventional period). Then 34 patients were treated with a modified coiling technique (modified period). DWI was obtained on the following day. We compared the occurrence of any DWI HSI lesions and the presence of the symptomatic lesions during the two time periods.

RESULTS

The incidence of the DWI HSI lesions differed significantly at 89.2% (33/37) during the conventional period and 26.5% (9/34) during the modified period (p < 0.0001). The incidence of symptomatic lesions differed between the two periods (29.7% during the conventional period vs. 2.9% during the modified period, p < 0.003).

CONCLUSION

Aspiration of the inner content of the microcatheter right after detachable coil delivery was helpful for the reduction of the incidence of microembolisms after endovascular coil embolization for the treatment of unruptured cerebral aneurysms.

Non-thrombotic fatal pulmonary embolism with a 'rule-out' CT scan

We report on a 36‐year‐old woman suffering from metastasized breast cancer and severe dyspnoea owing to right heart failure. Symptoms and findings were highly suggestive of pulmonary embolism. In rare cases, pulmonary embolism is caused not by migration of venous thrombi but by emboli of other origin. Patients with cancer can suffer from non‐thrombotic pulmonary embolism, either by (macroscopic) embolization of tumour mass or by microembolism also known as microscopic tumour microangiopathy. In patients with cancer with clinical presentation highly suggestive of pulmonary embolism, with echocardiographic findings confirming right ventricular dysfunction, and with negative CT angiography, pulmonary tumour microembolism should be considered as possible diagnosis.

Pulmonary oil micro-embolism (POME) syndrome: a review and summary of a large case series

The use of steroid compounds formulated in oil for depot injection can be associated with acute pulmonary reactions characterized primarily by cough, but sometimes with other associated symptoms. The pathophysiology of these reactions remains unclear, although they are reported in the literature as 'POMEs' or pulmonary oil micro-embolism events. We report on a large case series and propose a case definition for these events. These events can raise significant concern even though they are often self-limited. It is hoped that clinicians will recognize these events more readily and be able to inform patients better, and that future reports and assessments can benefit from our proposed case definition.

Hot-clot artifacts in the lung parenchyma on F-18 fluorodeoxyglucose positron emission tomography/CT due to faulty injection techniques: two case reports

F-18-fluorodeoxyglucose (FDG) positron emission tomography/CT is an important whole-body imaging tool in the oncology and widely utilized to stage and restage various malignancies. The findings of significant focal accumulation of FDG in the lung parenchyma in the absence of corresponding CT abnormalities are related to the lung microembolism and known as hot-clot artifacts. Herein we present two cases with focal FDG uptake in the lung parenchyma with no structural lesions on the CT scan and discuss the possible mechanisms.

Bubble stream reveals functionality of the right-to-left shunt: detection of a potential source for air embolism

The existence of a right-to-left shunt may increase the likelihood of micro-embolism by allowing a flux of bubbles under hyperbaric conditions. The aim of the study was to measure the relationship between these shunts and bubbles in 10 consecutive subjects using trans-thoracic and trans-esophageal echocardiography. In video frames, all cardiac chambers were segmented and bubbles were analyzed by our proposed method and two other methods. The relationship with bubbles and shunts was divided into three classes: no bubbles, 1-20 bubbles, >20 bubbles and measured over 2160 frames. Our sensitivity was 100% and our specificity was between 90.1% and 96.4%. There were 4.32-23.78 bubbles/frame in the left atrium according to our method. After the automatic analysis, shunts were graded double-blinded by two cardiologists. Consequently, we noted that aperture size does not necessarily reflect how active the right-to-left shunt is. Instead, our proposed decay curves constitute a better tool for determining functionality.