Diet for stroke prevention

Lifestyle is far more important than most physicians suppose.Dietary changes in China that have resulted from increased prosperity are probably responsible for a marked rise in coronary risk in the past several decades,accelerating in recent years.Intake of meat and eggs has increased,while intake of fruits,vegetables and whole grains has decreased.Between 2003 and 2013,coronary mortality in China increased 213%,while stroke mortality increased by 26.6%.Besides a high content of cholesterol,meat(particularly red meat)contains carnitine,while egg yolks contain phosphatidylcholine.Both are converted by the intestinal microbiome to trimethylamine,in turn oxidised in the liver to trimethylamine n-oxide(TMAO).TMAO causes atherosclerosis in animal models,and in patients referred for coronary angiography high levels after a test dose of two hard-boiled eggs predicted increased cardiovascular risk.The strongest evidence for dietary prevention of stroke and myocardial infarction is with the Mediterranean diet from Crete,a nearly vegetarian diet that is high in beneficial oils,whole grains,fruits,vegetables and legumes.Persons at risk of stroke should avoid egg yolk,limit intake of red meat and consume a diet similar to the Mediterranean diet.A crucial issue for stroke prevention in China is reduction of sodium intake.Dietary changes,although difficult to implement,represent an important opportunity to prevent stroke and have the potential to reverse the trend of increased cardiovascular risk in China.

Recent Advances in Stroke Prevention

Stroke is the most important cause of death and disability in China,and most strokes(~80-90%)are preventable.Recent advances in a number of measures to reduce stroke are discussed in this narrative review,including smoking cessation,a Mediterranean pattern of eating,salt restriction,B vitamins to lower homocysteine,antiplatelet therapy,anticoagulants and the management of patent foramen ovale and carotid stenosis.Lowering of homocysteine with B vitamins does prevent stroke,but patients with variants of MTHFR require higher doses of folic acid,and because of harm from cyanocobalamin among persons with renal impairment,we should use methylcobalamin or oxocobalamin instead.Aspirin resistance appears to be due to enteric coating,and>50% of Chinese have a reduced response to clopidogrel because of variants of CYP2C19,required to convert the prodrug to its active form.Direct acting oral anticoagulants(DOACs)have revolutionized anticoagulation;important differences among the DOACs are discussed.Percutaneous closure of patent foramen ovale(PFO)does reduce the risk of stroke,but in most patients with stroke and PFO the PFO is incidental;it is important to identify the subgroup in whom paradoxical embolism was the probable cause of the stroke.Some patients with PFO would be better treated with anticoagulants because of the risk of pulmonary embolism.Carotid stenting carries a higher risk in older patients,and most patients with asymptomatic carotid stenosis would be better treated with intensive medical therapy than with either stenting or endarterectomy;the few who could benefit can be identified.

Blood pressure gradients in cerebral arteries:a clue to pathogenesis of cerebral small vessel disease

rationale The role of hypertension in cerebral small vessel disease is poorly understood.At the base of the brain(the‘vascular centrencephalon’),short straight arteries transmit blood pressure directly to small resistance vessels;the cerebral convexity is supplied by long arteries with many branches,resulting in a drop in blood pressure.Hypertensive small vessel disease(lipohyalinosis)causes the classically described lacunar infarctions at the base of the brain;however,periventricular white matter intensities(WMIs)seen on MRI and WMI in subcortical areas over the convexity,which are often also called‘lacunes’,probably have different aetiologies.Objectives We studied pressure gradients from proximal to distal regions of the cerebral vasculature by mathematical modelling.Methods and results Blood flow/pressure equations were solved in an Anatomically Detailed Arterial Network(ADAN)model,considering a normotensive and a hypertensive case.Model parameters were suitably modified to account for structural changes in arterial vessels in the hypertensive scenario.Computations predict a marked drop in blood pressure from large and medium-sized cerebral vessels to cerebral peripheral beds.When blood pressure in the brachial artery is 192/113 mm Hg,the pressure in the small arterioles of the posterior parietal artery bed would be only 117/68 mm Hg.In the normotensive case,with blood pressure in the brachial artery of 117/75 mm Hg,the pressure in small parietal arterioles would be only 59/38 mm Hg.conclusion These findings have important implications for understanding small vessel disease.The marked pressure gradient across cerebral arteries should be taken into account when evaluating the pathogenesis of small WMIs on MRI.Hypertensive small vessel disease,affecting the arterioles at the base of the brain should be distinguished from small vessel disease in subcortical regions of the convexity and venous disease in the periventricular white matter.

How to identify which patients with asymptomatic carotid stenosis could benefit from endarterectomy or stenting

Offering routine carotid endarterectomy(CEA)or carotid artery stenting(CAS)to patients with asymptomatic carotid artery stenosis(ACS)is no longer considered as the optimal management of these patients.Equally suboptimal,however,is the policy of offering only best medical treatment(BMT)to all patients with ACS and not considering any of them for prophylactic CEA.In the last few years,there have been many studies aiming to identify reliable predictors of future cerebrovascular events that would allow the identification of patients with high-risk ACS and offer a prophylactic carotid intervention only to these patients to prevent them from becoming symptomatic.All patients with ACS should receive BMT.The present article will summarise the evidence suggesting ways to identify these high-risk asymptomatic individuals,namely:(1)microemboli detection on transcranial Doppler,(2)plaque echolucency on Duplex ultrasound,(3)progression in the severity of ACS,(4)silent embolic infarcts on brain CT/MRI,(5)reduced cerebrovascular reserve,(6)increased size of juxtaluminal hypoechoic area,(7)identification of intraplaque haemorrhage using MRI and(8)carotid ulceration.The evidence suggests that approximately 10%-15%of patents with asymptomatic stenosis might benefit from intervention;this will become more clear after publication of ongoing studies comparing stenting or endarterectomy with best medical therapy.In the meantime,no patient should be offered intervention unless there is evidence of high risk of ipsilateral stroke,from modalities such as those discussed here.

Controlling resistant hypertension

Resistant hypertension(failure to achieve target blood pressures with three or more antihypertensive drugs including a diuretic)is an important and preventable cause of stroke.Hypertension is highly prevalent in China(>60%of persons above age 65),and only~6%of hypertensives in China are controlled to target levels.Most strokes occur among persons with resistant hypertension;approximately half of strokes could be prevented by blood pressure control.Reasons for uncontrolled hypertension include(1)non-compliance;(2)consumption of substances that aggravated hypertension,such as excess salt,alcohol,licorice,decongestants and oral contraceptives;(3)therapeutic inertia(failure to intensify therapy when target blood pressures are not achieved);and(4)diagnostic inertia(failure to investigate the cause of resistant hypertension).In China,an additional factor is lack of availability of appropriate antihypertensive therapy in many healthcare settings.Sodium restriction in combination with a diet similar to the Cretan Mediterranean or the DASH(Dietary Approaches to Stop Hypertension)diet can lower blood pressure in proportion to the severity of hypertension.Physiologically individualised therapy for hypertension based on phenotyping by plasma renin activity and aldosterone can markedly improve blood pressure control.Renal hypertension(high renin/high aldosterone)is best treated with angiotensin receptor antagonists;primary aldosteronism(low renin/high aldosterone)is best treated with aldosterone antagonists(spironolactone or eplerenone);and hypertension due to overactivity of the renal epithelial sodium channel(low renin/low aldosterone;Liddle phenotype)is best treated with amiloride.The latter is far more common than most physicians suppose.

卒中预防新进展

在中国,卒中是死亡及致残的最重要原因,而且大部分卒中(约80-90%)是可以预防的。本文对近期卒中预防措施方面的进展进行综述,包括戒烟、地中海饮食、限制盐摄入量、使用B族维生素降低同型半胱氨酸、抗血小板治疗、抗凝、治疗卵圆孔未闭和颈动脉狭窄。使用B族维生素降低同型半胱氨酸水平的确能预防卒中,但是携带MTHFR变异的患者需要更高剂量的叶酸,并且由于氰钴胺对肾损伤患者有害,我们应该使用甲钴胺或羟钴胺。阿司匹林抵抗似乎是肠溶衣导致,而超过50%的中国人因存在细胞色素酶CYP2C19变异而对氯吡格雷反应减弱,该酶将药物从前体转化为活性状态。作为目前抗凝治疗的重大变革,新型口服抗凝药(DOACs)因其直接效应而备受关注,本文将着重讨论各个DOACs之间的主要差异。经皮卵圆孔封堵可降低卒中风险,但是在大多数有卵圆孔未闭的卒中患者中卵圆孔未闭是偶然出现的,因此识别出以反常栓塞为可能卒中机制的患者亚组十分重要。一些卵圆孔未闭的患者由于肺栓塞的风险更适宜使用抗凝治疗。颈动脉支架给高龄患者带来更高的风险,大多数无症状颈动脉狭窄患者接受强化药物治疗更优于支架置入术或内膜剥脱术,而只有少数患者可从颈动脉支架或内膜剥脱术中获益。