心阻抗血流图在次极量自行车负荷试验中使用价值的初步探讨

<正> 了解运动负荷中的血流动力学变化,不但能提高运动试验对缺血性心脏病的预测准确性,而且对客观地评定心血管功能也有意义。尤其在心血管病患者康复训练期,对于辅助判定运动强度、确定适当的“运动处方”以及评     

Syncope and neurologic deficits in a track athlete: a case report

Exercise-related syncope may result from various underlying medical conditions, with vasovagal reactions being the most common cause in young athletes. However, psychological causes also need to be considered in the differential diagnosis of syncope. This case report presents an athlete who suffered a syncopal event with residual motor and sensory deficits. The athlete was diagnosed with a conversion disorder and was able to return to full competition following psychotherapy and physical therapy.     

A comparison of myocardial function in former athletes and non-athletes.

Heart rate (HR), total electromechanical systole (Q-S2), left ventricular ejection time (LVET), pre-ejection period (PEP), and diastole (D) were compared in 350 former athletes and 156 non-athletes, age 27-74. The two cohorts had been equated according to habitual leisure time physical activity. Former athletes exhibited significantly longer Q-S2 and PEP at rest, and significantly lower HR and lengthened Q-S2, LVET, PEP, and D at one minute following a standard two minute step test (less than 0.05). Significantly differences were observed between athletes and non-athletes in the light and moderate activity categories. There were no significant differences between former athletes and non-athletes currently engaged in strenuous leisure time physical activity. Comparisons were made among the three levels of habitual leisure time physical activity with each group and revealed that HR was lower and Q-S2, LVET, PEP, and D were longer at rest and following exercise as the level of physical activity increased. There were more significant differences among former athletes than among non-athletes. Most of these differences were between light to moderate and light to strenuous levels of activity. The evidence suggests an advantage in myocardial function among former athletes compared to their non-athlete counterparts.     

急性高原反应高原肺水肿的心脏结构心功能及血气改变

本文采用自身对比实验,观察了急性高原反应(HAAR)、高原肺水肿(HAPE)患者治疗前及恢复后的心脏结构、功能及血气变化。发现HAAR及HAPE患者动脉血氧分压(PaO_2)动脉血氧饱和状(SaO_2)发病时明显降低,二者相比HAPE降低更明显,HAAP及HAPE患者的左心室舒张末期容量缩小,右心室舒张末期容量明显扩大,射血分数(EF)、心搏量(SV)及心输出量(CO)发病时明显下降,左心室射血时间(LVET)、喷血前期(PEP)及PEP/LVET也明显异常。HAPE的心脏结构和功能改变较HAAP明显。提示左右心功能不全也是HAPE发病的原因之一。     

海拔4300m地区高原居民红细胞压积与心缩间期的关系

为探讨高原居民红细胞及其压积对心缩间期的影响 ,在海拔 43 0 0m地区用心阻抗图法和心机械图法对 1 1 3名不同红细胞压积者的左室收缩功能进行了检测。结果 :红细胞压积与每搏量、射血分数呈显著负相关 ,而与射血前期与射血时间比值呈显著正相关(P <0 .0 0 1 )。随着红细胞压积值的增高 ,受试者的射血前期延长、左室射血时间缩短 ,射血前期与射血时间比值增大 ,射血分数下降。高原红细胞增多症患者的每搏量、心排出量明显下降。结论 :红细胞及其压积的高低对心缩间期和心泵功能的影响较大 ,红细胞增多是引起高原人体心功能降低的重要因素之一。     

田径运动员心缩间期的研究

<正> 近年来在运动医学领域中,心缩间期(STI)被认为是评定运动员心脏功能状况的指标之一。为了进一步探讨STI对于评定田径运动员的心脏功能状况的意义,我们进行了下列研究。     

Head-up tilt test for recurrent syncope in pilots

Syncope is defined as a sudden temporary loss of consciousness and postural tone that is associated with spontaneous recovery. Vasovagal or neurocardiogenic syncope is a common and usually benign cause of syncope. The mechanism may be cardioinhibitory, vasodepressor, or both. Diagnosis is usually made by a typical patient history with a definite trigger. Although vasovagal syncope is considered a benign condition, its occurrence in an aviator is worrisome, especially if recurrent and without a definite trigger. The head-up tilt test (HUTT) is used as a vasovagal syncope challenge test. A drop in BP and asystole during HUTT suggest a tendency to recurrent vasovagal syncope. We describe two military aviators with recurrent episodes of vasovagal syncope, one with definite triggers and one without. Both had positive HUTTs. The aviator with trigger-defined vasovagal syncope was disqualified from high-performance platforms due to his positive HUTT. The second case was disqualified from all platforms, irrespective of his HUTT result, because a definite trigger was not definable for all his syncopal episodes.     

生脉液对犬心肌缺血时左心室收缩时间间期的影响

用微米狭窄器在12条麻醉开胸犬上,造成急性心肌缺血,以左室排血时间(LVET)、排血前时间(PEP)、等容收缩时间(ICT).PEP/LVET比值和ICT/LVET比值,观察心肌缺血时生脉液用药前后心脏功能的改变.结果表明,急性心肌缺血时LVET值变小,PEP、ICT、PEP/LVET和ICT/LVET值增大,给药后,该药可使心脏功能明显好转.     

Pilots with vasovagal syncope: fit to fly?

Two pilots who had experienced vasovagal syncope were grounded by the aeromedical service. Pilot A had experienced three episodes of syncope in medical settings, none during flight. Pilot B had experienced four episodes of syncope in emotional/medical settings, one during flight. Whether a pilot who experienced one or more episodes of vasovagal syncope is declared fit to fly now depends on the number of episodes experienced. We propose that pilots should be assessed individually. Certainty of the diagnosis of vasovagal syncope, the chance and predictability of recurrences during flight, and the possibility of effective therapy should be assessed. Chance of recurrence during flight is low when the triggering factor is known and avoidable. Pilots with syncopal episodes in predictable (e.g., medical) situations, with clear prodromal symptoms and/or effective therapy, should be declared fit to fly. A symptom-free period and/or restriction to fly 'as or with a co-pilot' can be considered.     

Exertional Syncope and Presyncope

Physicians often see patients who have syncope or presyncope, but episodes associated with exercise are uncommon. Transient syncopal episodes usually require minimal evaluation and intervention. Most cases of exercise-associated syncope have neurocardiogenic origins and are benign, but fainting may signal a potentially fatal underlying problem. More serious causes of exertional syncope include structural cardiovascular abnormalities and cardiac arrhythmias. All physicians who care for active patients should be aware of the potential seriousness of this early warning sign and evaluate patients accordingly. Familiarity with the Bethesda guidelines will help clinicians decide when it is safe for an athlete to return to play following a syncopal episode.     

Cardiac response to whole-body heating.

Changes in ventricular function, as described by systolic time interval analysis, have been studied during heat stress and the time course of these changes, as well as changes in heart rate, have been investigated. Seven male and female subjects, 22-35 years of age, immersed their lower legs in water 42-44 degrees C for 30 min; their trunks and upper legs were enclosed in nonpermeable plastic to prevent evaporative heat loss. Total beat interval (R-R), left ventricular ejection time (LVET), pre-ejection period (PEP), arterial blood pressure, and oral temperature were monitored periodically during heating and recovery (post-hearing) periods. The stress induced significant (p less than 0.05) decreases in R-R and LVET by 5 min of heating which continued decreasing throughout the 30-min heating period. Heart rate accelerated from 72 up to 97 beats/min. LVET's during heat stress were shorter than those at similar resting heart rates. R-R and LVET were increased significantly by 1-min recovery but had not returned to preheating levels at 15 min. PEP, on the other hand, was not reduced until 15 min of heating, and did not start to recover until 3 min post-heating, after which it reached values exceeding control. A small increase in systolic blood pressure was maintained throughout heating and remained at 15 min recovery. Oral temperature increased approximately 1 degree C during the heating procedure; 50% of this was dissipated by 15 min recovery. Results are consistent with a two-stage cardiac response to heat-vagal withdrawal followed by a strong sympathetic outflow to the heart affecting both inotropic and chronotropic characteristics.     

Postexercise hypotension and hemodynamics: the role of exercise intensity

AIM: Although postexercise hypotension (PEH) has already been extensively demonstrated, the influence of exercise intensity on its magnitude and mechanisms is still controversial. METHODS: Twenty-three normotensive subjects were submitted to a control (45 minutes of rest) and 3 exercise sessions (cycle ergometer, 45 minutes at 30%, 50% and 75% of .VO(2peak)) to investigate the role of exercise intensity on PEH. Blood pressure (BP - auscultatory), heart rate (HR - ECG), and cardiac output (CO - CO2 rebreathing) were measured before and after the control and exercise sessions. RESULTS: Systolic BP decreased significantly after exercise at 50% and 75% of .VO(2peak). Diastolic BP increased significantly during the control session, did not change after exercise at 30% of .VO(2peak), and decreased significantly after exercise at 50% and 75% of .VO(2peak). This fall was greater and longer after more intense exercise. CO and systemic vascular resistance (SVR) responses were similar between sessions, CO increased whereas SVR decreased significantly. Stroke volume (SV) increased and heart rate (HR) decreased following control and exercise at 30% of .VO(2peak) whereas SV decreased and HR increased after exercise at 50% and 75% of .VO(2peak). CONCLUSION: PEH is greater and longer after more intense exercise. BP profile is followed by a decrease in SVR and an increase in CO, what was not influenced by previous exercise. The increase in CO is caused by an increase in SV after rest and low intensity exercise and by an increase in HR after moderate and more intense aerobic exercise.     

Cardiac function monitored by impedance cardiography during changing seatback angles and anti-G suit inflation

Impedance cardiography (IC) appears to be a promising noninvasive technique for monitoring small changes in pilot cardiovascular status during conditions simulating flight. Heart rate (HR), stroke volume (SV), cardiac output (CO), ventricular ejection time (VET), and thoracic impedance (Zo) were monitored in ten volunteers for 5 min at each of four seatback angles from vertical: 12 degrees, 30 degrees, 45 degrees, and 60 degrees. Data were also obtained at three seatback angles (12 degrees, 30 degrees, 60 degrees) for 6 min each before, during, and after inflation of the standard USAF anti-G suit to 1.5 psi. Significant differences (p less than 0.05) in HR, SV, CO, VET and Zo were observed among the four positions. Inflation of the standard anti-G suit to 1.5 psi at 1.0 +Gz did not significantly alter HR, SV, or CO; whereas, 1 min of deflation of the anti-G suit significantly altered HR, SV, CO compared to inflation values. The results suggest IC can detect small differences in HR, SV, CO, VET, and Zo within subjects as a function of minor changes in body position.     

头低位暴露后直立位下体负压作用的耐力变化和心血管反应

目的观察头低位后直立位下体负压暴露的耐力和心血管反应。方法8名被试者在下体负压倾斜床上进行“直立位-倒立位30s-直立位联合下体负压(-60mmHg)致晕厥前症状”的模拟推拉效应试验及单纯直立位 下体负压(-60mmHg)致晕厥前症状的对照试验,用阻抗法测量了试验过程中心血管功能指标的变化。结果在模拟推拉效应试验中,8名被试者出现晕厥前症状的平均耐受时间为4.5±2.4min,显著低于对照试验时的8.4±2.1min(P<0.01)。在倒立位,被试者HR较直立位基础值降低,SV和CO较直立位基础值升高,均有显著性意义。和基础值相比,直立位下体负压时HR增加的百分比显著低于对照试验(P<0.05),而直立位下体负压时SV和CO降低的百分比均显著高于对照试验时SV和CO降低的百分比(P<0.05)。在直立位下体负压暴露时,对照试验的PP和基础值比较显著降低(P<0.05),TPR比基础值显著增加(P<0.05)。结论倒立位后,再进行直立位下体负压作用,出现晕厥前症状的平均耐受时间缩短,心血管反应降低。     

21d头低位卧床期间心功能的变化及最后一周下体负压锻炼的影响

目的 观察21d头低位卧床期间被试者心功能的变化及最后一周下体负压锻炼（LBNP）的影响。方法 12名健康男性志愿者,随机分为对照组和LBNP组,每组6人,均参加头低位倾斜卧床实验。对照组在卧床期间不做任何处理,LBNP组在卧床最后一周,每天进行1h、－4．0kPa的下体负压锻炼。测量心脏收缩和泵血功能等指标。结果 在卧床期间,两组的心输出量、心指数及每搏输出量较卧床前均显著降低或有降低趋势,射血前期（PEP）均显著延长,总外周阻力、等容收缩时间／左室射血时间（LVET）、PEP／LVET均显著升高而有升高趋势,起床后第2天基本恢复。LBNP组PEP和PEP／LVET在第21天及起床后第2天较对照组显著升高。结论 21d头低位卧床可引起心脏泵血和收缩功能显著降低;在21d头低位卧床的最后一周进行下体负压锻炼,不能有效对抗头低位卧床模拟失重引起的心脏泵血和收缩功能的降低,但对提高立位耐力有利。     

Hypovolemic intolerance to lower body negative pressure in female runners.

PURPOSE: An attenuated baroreflex response and orthostatic intolerance have been reported in endurance-trained male athletes; however, it is still unknown whether this occurs also in females. The purpose of the present study was to examine whether endurance exercise-trained women had a predisposition to orthostatic compromise, and if so, what causative factor(s) may induce orthostatic intolerance. METHODS: We studied cardiovascular and hormonal responses to graded lower body negative pressure (LBNP) (0 to -60 mm Hg) in 26 middle-distance female runners (18.6 +/- 0.1 yr) as the exercise-trained (ET) subjects and 23 age-matched untrained (UT) control subjects. On the basis of the occurrence of syncope episodes during LBNP, ET and UT subjects were further allocated to two groups; ET with presyncope (ET+syncope) and without presyncope (ET-syncope) and UT with presyncope (UT+syncope) and without presyncope (UT-syncope). RESULTS: Occurrence of presyncope episodes during LBNP was higher in ET (65.4%, P < 0.05) than that for UT (34.8%). Leg compliance was higher (P < 0.05) in ET than in UT. LBNP reduced stroke volume (SV) more (P < 0.05), increased heart rate (HR) higher (P < 0.05), and increased forearm vascular resistance (FVR) more in ET+syncope as compared with the other groups. Response of vasoactive hormones to LBNP was higher in ET+syncope (P < 0.05) than that of the other groups except for norepinephrine (NE); high in both ET+syncope and UT+syncope. The relationship between SV and NE, an index of sympathetic neuronal response, had no training-related changes during LBNP. CONCLUSION: We conclude that exercise-trained females have a high incidence of orthostatic intolerance during LBNP, with a greater reduction of SV independent of changes in baroreflex and neurohumoral function. A lower incidence of LBNP intolerance in UT may be accounted for by a lower reduction of SV during LBNP. An increase in leg compliance in the exercise-trained females may play an important role in inducing pronounced reduction of SV and hence the intolerance to LBNP.     

Peripheral and systemic circulation after local dynamic exercise and recovery using passive foot movement and electrostimulation

AIM: This study analyzed the effect of additional means of recovery (passive foot movements [PFM] and electrical stimulation [ES]), on peripheral and systemic circulation. METHODS: The subjects were 16 endurance athletes. A period of passive rest (PR), ES and PFM were applied in 3 trials during which arterial blood flow in calf muscles, stroke volume (SV), heart rate (HR) and cardiac output (CO) were recorded. Repetitive exercise loading at 75% of maximum voluntary contraction to exhaustion was performed. RESULTS: A 15-min period of PR did not appreciably decrease residual fatigue of the exercised muscles, and working capacity during the second physical loading decreased by 84.9+/-28.3 Nm (P<0.05). After ES and PFM, muscle working capacity decreased insignificantly versus the values after the first loadings. After PR, SV (78+/-4.5 mL, P<0.05) and CO (5+/-0.3 L/min, P<0.05) decreased versus baseline values (95+/-6.6 mL and 5.8+/-0.3 L/min, respectively). After additional ES and PFM, SV and CO decreased insignificantly versus baseline values. CONCLUSION: ES and PFM improve blood return to the heart. After dynamic exercise, ES and PFM, applied as additional means of recovery, can enhance recovery and restore muscle working capacity.     

Transcranial Doppler evaluation of syncope: an application in aerospace physiology.

A non-invasive method which combines the simultaneous measurement of mean arterial blood pressure (MBP), heart rate (HR) and mean cerebral blood flow velocity (MFV) was used to monitor patients with history of syncope, in horizontal and vertical posture tilt at 80 degrees. MFV in the right middle cerebral artery was measured using a transcranial Doppler instrument (TCD). MFV decreased concurrently with the onset of symptoms, and at the time of syncope reached an average of 68% below pre-tilt values. At the same time MBP showed an average decline of 25%, and HR increased by 38%. There was no correlation between MBP and MFV, at the onset of tilt, presyncope and syncope. MFV, but not HR or MBP, showed significant transition from one condition to the other. These data suggest that there may be a useful application of TCD measurements of MFV in aeromedical evaluation of syncope or syncopal tendency. These measurements would necessarily be used in conjunction with a tilt-table procedure. The possibility exists that MFV might be useful to preclude the actual occurrence of syncope in test subjects, or to show an abnormal tendency toward syncope, but will require more extensive testing than that carried out in the present study.     

儿童在连续运动负荷过程中心率与心搏量的关系

<正> 心泵功能的强弱对运动成绩的重要影响早已确认,在运动中如何充分利用与发展心泵功能也就成为教练与运动员所关心的问题。德国心脏学家赖因德尔和教练员格希勒的早期研究曾提出了一个“间歇训练的格希勒——赖因德尔定律”:在负荷时心率达170——180次/1′,间歇恢复时至100～125     

女子中长跑运动员在安静、不同负荷与恢复状态下STI的变化特征

应用微机STI检测系统,观察女子中长跑运动员在功率自行车上从事三级不同负荷时与恢复期间STI 13个指标的变化,分析各个指标的变化特征及各指标变化之间的相互关系,发现LVET、EMT、MST、ICT、PEP等指标的变化有一临界值;EML与Q-U/LVET是不同负荷状态下最稳定的指标,同时还发现HWT在实验过程中呈现出独特的变化。