Perspective: physiological role(s) of the vascular myogenic response

The vascular myogenic response is an inherent property of VSM in the walls of small arteries and arterioles, allowing these principal resistance segments of the microcirculation to respond to changes in transmural pressure. Elevated intraluminal pressure leads to myogenic constriction, whereas reduced pressure leads to myogenic dilation. This review focuses on the physiological significance of the myogenic response in microvascular networks. First, historical concepts related to the detection of stretch by the vessel wall are reviewed, including the wall tension hypothesis, and the implications of the proposal that the arteriolar network responds to Pp changes as a system of series-coupled myogenic effectors. Next, the role of the myogenic response in the local regulation of blood flow and/or Pc is examined. Finally, the interaction of myogenic constriction and dilation with other local control mechanisms, including metabolic, neural and shear-dependent mechanisms, is discussed. Throughout the review, an attempt is made to integrate historical and current literature with an emphasis on the physiological role, rather than the underlying signaling mechanisms, of this important component of vascular control.     

Delirium in diabetic ketoacidosis: a case report

A 15-year-old female patient with known type 1 diabetes mellitus was referred because of abdominal pain. On admission, she was alert but dehydrated with marked Kussmaul breathing. Blood glucose was 414 mg/dL (23 mmol/L). Blood gas analysis revealed severe metabolic acidosis (pH: 6.99) with an elevated anion gap (29.8 mmol/L) and an increased base excess (-25.2 mmol/L). At the sixth hour of treatment with intravenous fluids and insulin, the patient became delirious. The delirium persisted despite the normalization of the acidosis and became difficult to manage. Brain imaging studies revealed neither brain edema nor other intracranial pathology. No evidence of intoxication could be found. The patient gradually regained consciousness and was diagnosed as a case of severe diabetic ketoacidosis (DKA) associated with infection. We were unable to find a similar case in the pediatric literature and thought that reporting this unusual case would be a contribution to the literature on DKA in children.     

COVID-19 and Eye: A Review of Ophthalmic Manifestations of COVID-19

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has had health implications of unprecedented magnitude. The infection can range from asymptomatic, mild to life threatening respiratory distress. It can affect almost every organ of the body. Ophthalmologists world over are reporting various manifestations of the infection in the eye. This review was undertaken to help ophthalmologists recognize the possible manifestations and the stage of the viral disease when they commonly appear. Literature search was performed for the publications on ophthalmic manifestations of coronavirus disease-19 (COVID-19) between January 1, 2020 and January 31, 2021. 46 case reports, 8 case series, 11 cross sectional/cohort observational studies, 5 prospective interventional studies, 3 animal models/autopsy studies and 6 reviews/meta-analysis were included. Conjunctivitis is the most common manifestation and can develop at any stage of the disease. Direct effect due to virus, immune mediated tissue damage, activation of the coagulation cascade and prothrombotic state induced by the viral infection, the associated comorbidities and drugs used in the management are responsible for the findings in the eye. The viral ribonucleic acid (RNA) has been isolated from ocular tissues but the role of eye as a route for infection is yet to be substantiated. Ophthalmic manifestations may be the presenting feature of COVID-19 infection or they may develop several weeks after recovery. Ophthalmologists should be aware of the possible associations of ocular diseases with SARS-CoV-2 in order to ask relevant history, look for specific signs, advise appropriate tests and thereby mitigate the spread of infection as well as diagnose and initiate early treatment for life and vision threatening complications.     

Microvascular and functional changes according to the fundus location of the affected arteriovenous crossing in patients with branch retinal vein occlusion

Purpose:The aim of this study was to evaluate the structural and functional changes occurring in patients with branch retinal vein occlusion (BRVO) according to the distance of the affected arteriovenous (AV) crossing to the centers of the fovea and optic disc by optic coherence tomography angiography (OCTA).Methods:Forty-five patients with unilateral BRVO and 45 age- and sex-matched healthy controls were included in this retrospective observational study. Images of the macula (3 mm × 3 mm) and affected AV crossing sites were obtained by OCTA. The fovea-AV crossing distance (FAVD), optic disc-AV crossing distance (DAVD), and optic disc-fovea distance (DFD) were measured.Results:The FAVD/DFD ratio was positively correlated with the vessel density in the superficial and deep affected hemifields (r = 0.430, P < 0.05 and r = 0.308, P < 0.05, respectively) and negatively correlated with the superficial foveal avascular zone and logarithm of the minimum angle of resolution (logMAR) visual acuity (r = –0.412, P < 0.05 and r = –0.356, P < 0.05, respectively). The DAVD/DFD ratio was not correlated with the logMAR visual acuity, superficial FAZ area or vessel densities in the affected hemifield (all P > 0.05).Conclusion:The affected AV crossing site that was further away from the fovea had better visual acuity and quantitative microvascular parameters in the affected hemifields. However, this correlation was not observed for the distance between the affected AV crossing site and the optic disc.     

Embolic Protection Devices in Saphenous Vein Graft and Native Vessel Percutaneous Intervention: A Review

The clinical benefit of percutaneous intervention (PCI) depends on both angiographic success at the site of intervention as well as the restoration of adequate microvascular perfusion. Saphenous vein graft intervention is commonly associated with evidence of distal plaque embolization, which is correlated with worse clinical outcomes. Despite successful epicardial intervention in the acute MI patient treated with primary PCI, distal tissue perfusion may still be absent in up to 25% of cases [1-3]. Multiple devices and pharmacologic regimens have been developed and refined in an attempt to protect the microvascular circulation during both saphenous vein graft intervention and primary PCI in the acute MI setting. We will review the evidence for various techniques for embolic protection of the distal myocardium during saphenous vein graft PCI and primary PCI in the native vessel.     

糖尿病性黄斑水肿与肾功能受损的相关性

目的 探讨糖尿病性黄斑水肿（diabetic macular edema,DME）与肾功能受损及其严重程度的相关性。设计 回顾性病例系列。研究对象 2016年1月至2020年12月北京老年医院内分泌科住院患者中在眼科会诊的2型糖尿病患者1023例。方法 通过调阅病历获得研究对象的年龄、收缩压、舒张压、血肌酐、空腹静脉血血糖、糖化血红蛋白以及尿微量白蛋白。应用CKD-EPI scr(2009)公式计算估算肾小球滤过率（estimated glomerular filtration rate,eGFR)）。eGFR≥90 ml/min/1.73m2为肾功能正常,60~90 ml/min/1.73m2为肾功能受损,﹤60 ml/min/1.73m2为肾功能不全。调取患者立体彩色眼底像、相干光断层扫描图像。根据美国“糖尿病视网膜病变早期治疗小组”标准诊断DME。比较不同eGFR分级组患者DME的发生率,并采用Logistics回归分析黄斑水肿与肾功能受损程度的相关性。主要指标 DME的发生率。结果 120例患者被诊断为DME。DME的发生与eGFR分级相关,肾功能正常、肾功能受损和肾功能不全患者中,DME患者的比例分别为8.30%、20.51%和24.63%,显示随肾功能异常者DME患者比例显著增加（χ2=34.252,P=0.000）。Logistic回归显示肾功能受损、肾功能不全者发生DME的风险分别是肾功能正常者的1.604倍及2.573倍。结论 DME的发生与肾功能受损及其严重程度相关。（眼科,2021, 30： 232-235）     

Current Hot Potatoes in Atrial Fibrillation Ablation

Atrial fibrillation (AF) ablation has evolved to the treatment of choice for patients with drug-resistant and symptomatic AF. Pulmonary vein isolation at the ostial or antral level usually is sufficient for treatment of true paroxysmal AF. For persistent AF ablation, drivers and perpetuators outside of the pulmonary veins are responsible for AF maintenance and have to be targeted to achieve satisfying arrhythmia-free success rate. Both complex fractionated atrial electrogram (CFAE) ablation and linear ablation are added to pulmonary vein isolation for persistent AF ablation. Nevertheless, ablation failure and necessity of repeat ablations are still frequent, especially after persistent AF ablation. Pulmonary vein reconduction is the main reason for arrhythmia recurrence after paroxysmal and to a lesser extent after persistent AF ablation. Failure of persistent AF ablation mostly is a consequence of inadequate trigger ablation, substrate modification or incompletely ablated or reconducting linear lesions. In this review we will discuss these points responsible for AF recurrence after ablation and review current possibilities on how to overcome these limitations.     

Systems Biology and Biomechanical Model of Heart Failure

Heart failure is seen as a complex disease caused by a combination of a mechanical disorder, cardiac remodeling and neurohormonal activation. To define heart failure the systems biology approach integrates genes and molecules, interprets the relationship of the molecular networks with modular functional units, and explains the interaction between mechanical dysfunction and cardiac remodeling. The biomechanical model of heart failure explains satisfactorily the progression of myocardial dysfunction and the development of clinical phenotypes. The earliest mechanical changes and stresses applied in myocardial cells and/or myocardial loss or dysfunction activate left ventricular cavity remodeling and other neurohormonal regulatory mechanisms such as early release of natriuretic peptides followed by SAS and RAAS mobilization. Eventually the neurohormonal activation and the left ventricular remodeling process are leading to clinical deterioration of heart failure towards a multi-organic damage. It is hypothesized that approaching heart failure with the methodology of systems biology we promote the elucidation of its complex pathophysiology and most probably we can invent new therapeutic strategies.