尾部悬吊及恢复过程中大鼠动脉血管收缩反应的变化

目的 探讨模拟失重下动脉收缩反应变化的时程特征及其可逆性。方法 采用尾部悬吊大鼠模型模拟失重,利用离休动脉环测定血管收缩反应的变化。结果 尾部悬吊２ｗｋ后,大鼠的腹主动脉、肠系膜动脉和股动脉收缩反应明显降低,而颈总动脉无明显改变;悬吊４ｗｋ后,肠系膜动脉和股动脉的收缩反应与悬吊２ｗｋ相比有进一步的降低;悬吊８ｗｋ大鼠的动脉血管收缩反应性与悬吊４ｗｋ相比无明显差异;４ｗｋ尾部悬吊大鼠解除悬吊后５ｗｋ     

Impaired cerebral vasoreactivity in white coat hypertensive adolescents

Background and purpose: Although its incidence is not high, adolescent hypertension may predict hypertension and increased cardiovascular risk in adulthood. Therefore, the aim of the present study was to assess whether cerebrovascular reactivity is altered in adolescent white coat and sustained hypertensive patients compared to healthy teenagers. Methods: Fifty‐nine normotensive, 47 white coat hypertensive (WCH), and 73 sustained hypertensive (SH) adolescents were studied. WCH and SH were differentiated by ambulatory blood pressure monitoring. Cerebrovascular reactivity was assessed by transcranial Doppler breath‐holding test and was expressed in percent (%) change to the resting cerebral blood flow velocity value. Results: The percent increase in middle cerebral artery mean blood flow velocity after 30 s of breath holding was lower in both WCH (5.3 ± 3.1%) and SH (9.5 ± 2.6%) groups indicating lower vasodilatory reactivity compared to healthy adolescents (12.1 ± 2.2%). Additionally, serum nitric oxide (NOx) concentrations were lower in both WCH (30.6 ± 11 μM) and SH (30.7 ± 22.4 μM) groups compared to controls (38.8 ± 7.6 μM). Conclusions: Both white coat and sustained hypertension result in decreased vasodilatory reaction to CO₂ in adolescents, suggesting involvement of the cerebral arterioles. The present study underlines the importance of early recognition and proper treatment of adolescent hypertension in order to prevent long‐term cardiovascular complications.     

Ultrafine particulate matter exposure impairs vasorelaxant response in superoxide dismutase 2-deficient murine aortic rings

Studies have linked exposure to ultrafine particulate matter (PM) and adverse cardiovascular events. PM-induced oxidative stress is believed to be a key mechanism underlying observed adverse vascular effects. Advanced age is one factor known to decrease antioxidant defenses and confer susceptibility to the detrimental vascular effects seen following PM exposure. The present study was designed to investigate the vasomotor responses following ultrafine PM exposure in wild type (WT) and superoxide dismutase 2-deficient (SOD2^+/–) mice that possess decreased antioxidant defense. Thoracic aortic rings isolated from young and aged WT and SOD2^+/– mice were exposed to ultrafine PM in a tissue bath system. Aortic rings were then constricted with increasing concentrations of phenylephrine, followed by relaxation with rising amounts of nitroglycerin (NTG). Data demonstrated that ultrafine PM decreased the relaxation response in both young WT and young SOD2^+/– mouse aortas, and relaxation was significantly reduced in young SOD2^+/– compared to WT mice. Ultrafine PM significantly diminished the NTG-induced relaxation response in aged compared to young mouse aortas. After ultrafine PM exposure, the relaxation response did not differ markedly between aged WT and aged SOD2^+/– mice. Data demonstrated that the greater vascular effect in aortic rings in aged mice ex vivo after ultrafine PM exposure may be attributed to ultrafine PM-induced oxidative stress and loss of antioxidant defenses in aged vascular tissue. Consistent with this conclusion is the attenuation of NTG-induced relaxation response in young SOD2^+/– mice.

Abbreviations: H₂O₂: hydrogen peroxide; NTG: nitroglycerin; PAH: polycyclic aromatic hydrocarbons; PE: l-phenylephrine; PM: particulate matter; ROS: reactive oxygen species; SOD2: superoxide dismutase 2 deficient; WT: wild type     

Challenges and Special Aspects of Pulmonary Hypertension in Middle- to Low-Income Regions: JACC State-of-the-Art Review

Challenges and special aspects related to the management and prognosis of pulmonary hypertension (PH) in middle- to low-income regions (MLIRs) range from late presentation to comorbidities, lack of resources and expertise, cost, and rare options of lung transplantation. Expert consensus recommendations addressing the specific challenges for prevention and therapy of PH in MLIRs with limited resources have been lacking. To date, 6 MLIR-PH registries containing mostly adult patients with PH exist. Importantly, the global prevalence of PH is much higher in MLIRs compared with high-income regions: group 2 PH (left heart disease), pulmonary arterial hypertension associated with unrepaired congenital heart disease, human immunodeficiency virus, or schistosomiasis are highly prevalent. This consensus statement provides selective, tailored modifications to the current PH guidelines to address the specific challenges faced in MLIRs, resulting in the first pragmatic and cost-effective consensus recommendations for PH care providers, patients, and their families.     

Vascular reactivity in sepsis: regional differences

Summary In the course of severe sepsis, blood flow distribution is altered, so that regional blood flow may not match demand and focal ischemia ensues. Apart from circulating factors, altered reactivity of the vasculature could partly account for blood flow maldistribution. Indeed, changes in both the endothelium-dependent, acetylcholine-induced vascular relaxation, induction of inducible NO synthase and impaired vascular smooth muscle constrictor responses, differ among isolated small arteries from various vascular beds, incubated with endotoxin. However, it is difficult to define the effect of these changes, elaborated in this review, on blood flow maldistribution. Nevertheless, studies for the treatment of human septic shock with the help of drugs intervening in vascular reactivity should incorporate evaluation of regional blood flow, in order to avoid focal ischemia. Received: 21 December 2001 Accepted: 24 June 2002     

Cerebral CO2 vasoreactivity evaluation by transcranial Doppler ultrasound technique: a standardized methodology

Objective: In normal subjects cerebral CO₂ vasoreactivity is measured during spontaneous hyperventilation, breathholding, or adding CO₂ to inspiratory gases. The correlation between CO₂ and cerebral blood flow may, however, be invalidated by the effects of a modified respiratory pattern on venous return, sympathovagal balance, and cathecolamine release. Moreover, the duration of the test, usually not considered, may play an important role. This may justify the scattering of values found in literature. We evaluated a new standardized method for overcoming these confounding factors.¶Design: Experimental.¶Participants: Twenty-one healthy volunteers.¶Methods: Subjects were connected through a mouthpiece to a mechanical ventilator set in the intermittent positive pressure ventilation mode. The ventilator was fed by two 40-l tanks, one of which contained 5 % CO₂. The inspiratory CO₂ concentration was varied at fixed time intervals from 0 % to 5 % without modifying ventilator settings. End-tidal CO₂ was measured at the mouthpiece. Mean blood velocity (V_m) and pulsatility index (PI) in the middle cerebral artery were measured by means of transcranial Doppler ultrasound.¶Results: The test was easily applicable and well tolerated. No hemodynamic alterations were observed during the tests. The correlation between CO₂ and V_m was always linear and highly significant (R ² > 0.8, p < 0.0001). A low intersubject variability was observed. No difference was found between the two hemispheres, nor between the sexes.¶Conclusions: The strict standardization of the technique, avoiding hemodynamic interference, may explain the low intersubject variability. The value of this technique in ventilated neurosurgical patients is still speculative, but it might allow the collecting of valuable data together with a reduction in exposure to CO₂, and hence cerebral blood flow modifications.     

Assessment of pulmonary hypertension in the pediatric catheterization laboratory: Current insights from the magic registry

Objectives: To assess protocols, demographics, and hemodynamics in pediatric patients undergoing catheterization for pulmonary hypertension (PH). Background: Pediatric specific data is limited on PH. Methods: Review of the Mid‐Atlantic Group of Interventional Cardiology (MAGIC) collaboration PH registry dataset. Results: Between November 2003 and October 2008, seven institutions submitted data from 177 initial catheterizations in pediatric patients with suspected PH. Pulmonary arterial hypertension associated with congenital heart disease (APAH‐CHD) (n = 61, 34%) was more common than idiopathic PAH (IPAH) (n = 36, 20%). IPAH patients were older with higher mean pulmonary arterial pressures (mPAP) (P < 0.01). Oxygen lowered mPAP in patients with IPAH (P < 0.01) and associated PAH not related to congenital heart disease (APAH‐non CHD) (P < 0.01). A synergistic effect was seen with inhaled Nitric Oxide (iNO) (P < 0.01). Overall 9/30 (29%) patients with IPAH and 8/48 (16%) patients with APAH‐non CHD were reactive to vasodilator testing. Oxygen lowered pulmonary vascular resistance index (PVRI) in patients with APAH‐CHD (P < 0.01). There was no additive effect with iNO but a subset of patients required iNO to lower PVRI below 5 WU·m². General anesthesia (GA) lowered systemic arterial pressure (P < 0.01) with no difference between GA and procedural sedation on mPAP or PVRI. Adverse events were rare (n = 7) with no procedural deaths. Conclusions: Pediatric patients with PH demonstrate a higher incidence of APAH‐CHD and neonatal specific disorders compared to adults. Pediatric PH patients may demonstrate baseline mPAP < 40 mm Hg but > 50% systemic illustrating the difficulty in applying adult criteria to children with PH. Catheterization in children with PH is relatively safe. © 2010 Wiley‐Liss, Inc.     

脑动静脉畸形血液动力学研究

目的 建立脑动静脉畸形（ＡＶＭ）的是生理学模型，检测血液动力学改变。方法 将大鼠左侧颈外静脉与颈总动脉行端侧吻合，结扎吻合口近尾端的颈总动脉，测定吻合前后及模型动物饲养１６周后的局部脑血流量、右侧颈外静脉压力、颈总动脉压力、颈总动脉的血流速度。结果 大鼠静脉动脉的端侧吻合形成动静脉分流，左侧局部脑血流量显著降低，右侧颈外静脉压增加、颈总动脉压降低、颈总动脉血流速度增快。１６周后，局部脑血流量较动静     

Doppler study of the ophthalmic artery in patients with carotid occlusive disease

Assessing the adequacy of collateral circulatory pathways has become increasingly important in the investigation of cerebral circulation. Using transorbital Doppler ultrasonography (TOD), we examined the ophthalmic artery (OA) in patients with hernodynamic significant internal carotid artery (ICA) occlusive disease. The velocity and the direction of flow in the OA were studied in 45 patients (occlusion n = 27, stenosis > 75% n = 18), and in 30 age matched controls, under baseline conditions and within 30 minutes after the i.v. administration of 1 g acetazolamide as a vasodilatory stimulus. Based on the direction of flow before and after acetazolamide, the 45 patients could be separated into four groups with increasing degree of ICA lesions. In group I the OA flow was anterograde, but the velocity decreased after acetazolamide. In group II the OA direction became retrograde after acetazolamide, indicating collateral flow to the brain. In patients with retrograde OA flow following acetazolamide injection (group 11-IV), the vessel reacted similarly to an intracranial artery, with marked increase in velocity when vasoreactivity was tested. TOD and the acetazolamide test provide useful information about potential collateral OA flow to the brain in patients with ICA occlusive disease.