Cardiovascular autonomic dysfunction in normotensive awake subjects with obstructive sleep apnoea syndrome

Cardiovascular autonomic function in normotensive awake patients with obstructive sleep apnoea syndrome was studied in 21 normotensive (mean age 48 ± 14 years), drug-free men with obstructive sleep apnoea syndrome. Cardiovascular reflex tests with continuous blood pressure monitoring and biochemical indices were performed the morning after a standard polygraphic sleep recording. A group of 20 agematched (mean age 49 ± 19 years) normal subjects was used as controls. The obstructive sleep apnoea syndrome patients showed higher heart rate and noradrenaline plasma levels (p < 0.05) at rest and a higher blood pressure response to head-up tilt (p < 0.01), suggesting sympathetic overactivity. Respiratory arrhythmia, baroreflex sensitivity index and Valsalva ratio were significantly lower in the obstructive sleep apnoea syndrome group (p < 0.01) whereas the decrease in heart rate induced by the cold face test was significantly higher (p < 0.05) showing a blunting of reflexes dependent on baroreceptor or pulmonary afferents with normal or increased cardiac vagal efferent activity. These abnormalities in autonomic regulation may predispose obstructive sleep apnoea syndrome patients to cardiovascular complications like hypertension and cardiac arrhythmias.     

Cystic brain stem necrosis in a premature infant after prolonged bradycardia

Summary A case is described of symmetrical cavitating brain stem necrosis produced by cardiac arrest in a premature infant. Two months after birth this 25-week gestational age infant suffered a prolonged episode of bradycardia. She was resuscitated and then died 3 weeks later. The autopsy revealed striking bilateral cavitation of the brain stem tegmentum extending in a columnar fashion from the upper portion of the spinal cord to the hypothalamus. The findings in this case are identical to the brain stem injury experimentally produced by complete cardiac arrest in the rhesus monkey.     

Central and peripheral contributions to control of heart rate during heat acclimation

The contributions of the autonomic nervous system and the cardiac pacing cells in the development of heat-acclimation-induced bradycardia were analyzed, and the effect of heat acclimation on the chronotropic response of the heart to heat stress (40° C) was studied. Rats were acclimated at 34° C for 0, 5, 14, 30 and 60 days. Heart rate (HR) was measured in conscious animals, using chronic subcutaneous electrodes. Sympathetic and parasympathetic influences were studied by IP administration of 0.1 and 1 mg/100 g body weight atropine and propranolol respectively, while intrinsic HR (HR_i) was measured following administration of both drugs simultaneously. The effects of carbamylcholine and norepinephrine on the beating rate of isolated rat atria were investigated to study pacemaker responsiveness to neutrotransmitters. Up to day 14 of heat acclimation, bradycardia was attained by tonic parasympathetic acceleration (18%) and temporal sympathetic withdrawal (0.8% on day 14), to compensate for the gradually augmented HR_i (2.5% and 8% on days 5 and 14, respectively). Following long-term acclimation HR_i declined below pre-acclimation rate. This was associated with resumed sympathetic activity (16% and 10% on days 30 and 60 respectively) while parasympathetic activity continued to be high (18%). Tachycardia, known to occur with severe uncontrolled body hyperthermia, was attenuated following heat acclimation by 42%. It was concluded that during the initial phase of heat acclimation bradycardia is achieved primarily by changes in autonomic influences, while following long-term acclimation, changes in the intrinsic properties of the pacing cells (HR_i) and the autonomic system both play a role.     

Naloxone-provoked vaso-vagal response to head-up tilt in men

A double-blind paired protocol was used to evaluate, in eight male volunteers, the effects of the endogenous opiate antagonist naloxone (NAL; 0.05 mg· kg^–1) on cardiovascular responses to 50° head-up tilt-induced central hypovolaemia. Progressive central hypovolaemia was characterized by a phase of normotensive-tachycardia followed by an episode of hypotensive-bradycardia. The NAL shortened the former from 20 (8–40) to 5 (3–10) min (median and range; (P < 0.02). Control head-up tilt increased the means of thoracic electrical impedance [from 35.8 (SEM 2.1) to 40.0 (SEM 1.8) ; P < 0.01 of heart rate [HR; from 67 (SEM 5) to 96 (SEM 8) beats · min^–1, P < 0.02], of total peripheral resistance [TPR; from 25.5 (SEM 3.2) to 50.4 (SEM 10.5)mmHg min 1^–1,P < 0.05] and of mean arterial pressure [MAP; from 96 (SEM 2) to 101 (SEM 2)mmHg, P < 0.02]. Decreases were observed in stroke volume [from 65 (SEM 12) to 38 (SEM 9) ml, P < 0.01], in cardiac output [from 3.7 (SEM 0.7) to 2.5 (SEM 0.5) 1 · mint, P < 0.01], in pulse pressure [from 55 (SEM 4) to 37 (SEM 3)mmHg, P < 0.01] and in central venous oxygen saturation [from 73 (SEM 2) to 59 (SEM 4)%, P < 0.01]. During NAL, mean HR increased from 70 (SEM 3); n.s. compared to control) to only 86 (SEM 9) beats · min^–1 (P < 0.02 compared to control) and MAP remained stable. The episode of hypotensive-bradycardia appeared as mean control HR decreased to 77 (SEM 7)beats · min^–1, TPR to 31.4(SEM 7.7)mmHg · min · 1^–1 and MAP to 60 (SEM 5)mmHg (P < 0.01), and the volunteers were tilted supine. Cardiovascular effects of naloxone on central hypovolaemia included a reduced elevation of HR and blood pressures and provocation of the episode of hypotensive-bradycardia.     

参松养心胶囊及曲美他嗪联用对慢性心力衰竭合并窦性心动过缓患者心功能和HRV相关指标的影响

目的:研究参松养心胶囊与曲美他嗪联用对慢性心力衰竭合并窦性心动过缓患者心功能和HRV相关指标的影响。方法:选取2015年7月至2016年8月石景山医院收治的慢性心力衰竭合并窦性心动过缓患者94例。按照就诊顺序分为观察组与对照组,每组47例。对照组患者予以曲美他嗪治疗,观察组则在对照组的基础上加用参松养心胶囊治疗。分别比较2组临床疗效,治疗前后心功能、24 h动态心电图平均心率以及HRV相关指标变化情况。结果:观察组患者治疗总有效率为97.87%(46/47),显著高于对照组的85.11%(40/47)(P0.05)。治疗前2组患者各项心功能水平比较,差异无统计学意义,分别治疗后观察组患者LVEF、CO、SV、6 min步行距离分别为(53.6±4.1)%、(5.0±0.7)L/min、(46.1±6.9)mL/次、(394.2±60.4)m,均显著高于对照组的(49.2±3.9)%、(4.2±0.6)L/min、(41.4±5.7)mL/次、(363.6±58.2)m(均P0.05)。治疗后观察组与对照组患者24 h动态心电图平均心率分别为(66.8±6.1)次/min、(55.2±6.7)次/min,均显著高于治疗前,而观察组又显著高于对照组(均P0.05)。治疗后观察组患者SDANN、SDNN、r MSSD、PNN50水平分别为(112.6±20.1)ms、(129.2±21.5)ms、(25.2±5.7)ms、(6.0±0.8)%,均显著高于对照组的(85.7±19.2)ms、(94.1±14.5)ms、(20.1±5.8)ms、(2.8±0.7)%(均P0.05)。结论:参松养心胶囊与曲美他嗪联合治疗慢性心力衰竭合并窦性心动过缓的疗效显著,可有效改善患者心功能以及HRV相关指标,有利于促进患者早日康复。     

右美托咪啶在心脏术后患者中应用的临床研究

目的：研究右美托咪啶用于ICU心脏术后患者的镇静效果及安全性。方法：选择收住我院重症监护病房（ICU）心脏术后需机械通气的患者13例,随机分为右美托咪啶组（n=6）和丙泊酚组（n=7）,两组分别给予右美托咪啶和丙泊酚镇静治疗并同时给予吗啡镇痛,镇静目标为Ramsay评分2-4分。监测用药期间呼吸频率、心率、血压、脉搏血氧饱和度,并记录镇静药物剂量、机械通气时间、停药后唤醒时间、意外拔管情况以及镇静药物相关并发症（谵妄、低血压、心动过缓）。结果：两组患者镇静达标时间的比例无显著差异（P〉0.05）,右美托咪啶组停药后躁动的比例明显少于丙泊酚组（0%比28.57%,P〈0.05）,右美托咪啶组谵妄发生率明显少于丙泊酚组（0%比14.28%,P〈0.05）,两组机械通气时间无明显差异[（10.51±5.11）h比（11.07±4.91）h,P〉0.05],两组意外拔管率无明显差异（0%比0%,P〉0.05）。两组患者低血压发生率（33.33%比42.86%,P〉0.05）、需要干预的低血压比例（16.67%比28.57%,P〉0.05）均无显著差异,两组心动过缓发生率（33.33%比28.57%,P〉0.05）无显著差异。结论 ：右美托咪啶用于心脏术后患者能够实现镇静目标,对呼吸、循环无显著影响,可安全使用。     

心脏起搏对心动过缓患者心功能及房性心律失常的影响

目的:评价不同起搏方式(DDD方式和VVI方式)对长期心脏起搏患者心功能及心律失常的影响。方法:分别对43例VVI起搏治疗和32例DDD起搏治疗患者进行临床、心电图、超声心动图的定期随访,随访时间平均为34±6.8个月和32±8.3个月。结果:与治疗前比较,R波抑制型起搏器(VVI)组随访期左房内径明显增大,左室射血分数(LVEF)显著减退(P均<0.05);房室全能型起搏器(DDD)组左房内径、LVEF无显著差异;与DDD组比较,VVI组左房内径明显增大(P<0.01),LVEF显著减退(P<0.01),房性心律失常明显增加(P<0.01),心功能显著恶化(级别显著增加),P<0.05。结论:DDD心脏起搏器可显著改善心功能,减少房性心律失常,比VVI起搏器为佳。