不同体位对收缩时间间期(STI)和每搏输出量(SV)的影响

用心阻抗法测算了30名男性青年学生在卧、蹲、垂直(坐、站)等不同体位状态下的收缩时间间期、每搏输出量和心输出量。结果表明,QS_2、LVET、LVETc、SY、CO均随卧、蹲、坐、站位递减;而PEP、QS_1、IVCT、PEP/LVET则按上述体位的顺序递增。本文认为,STI可反映不同体位状态下的血液动力学改变,其中LVET和PEP/LVET两个指标更为敏感。     

测定心脏收缩时间间期在房间隔缺损中的应用

我们曾测量分析了房缺、室缺和动脉导管未闭患者中的心脏收缩时间间期(STI),发现心内分流和心外分流的心功变化有其不同的特点,其中房缺患者在STI上的变化是以PEP、ICT和Q-S_1延长,LVET缩短,PEP/LVET和ICT/LVET比值增大为特征的。本文在此基础上进一步分析了房缺患者中分流量、肺动脉压、年龄等与STI异常的关系,并比较手术前     

心脏收缩时间间期与冠状动脉狭窄程度或范围的相关性研究

心脏收缩时间间期(STI)通过单笔心电图机叠加记录ECG、心音图和颈动脉图后测得。对83例患者进行了STI均值与选择性冠状动脉造影(CAG)及左室造影的相关研究。患者除陈旧性心肌梗塞及室壁瘤外,根据冠状动脉(CA)狭窄程度而分组。STI随CA狭窄程度及范围的增加而显著异常,提示心功能随心肌缺血程度加重而进行性恶化。左室射血分数(LVEF)的降低也支持这一点。CA狭窄程度、范围与射血前时间/左室射血时间(PEP/LVET)呈正相关。在决定左室功能的异常方面,PEP/LVET和LVEF的临床意义完全相同。提示STI在评价冠心病心功能上是有用的。排除影响STI的某些因素后,PEP/LVET≥0.38可作为判断冠心病左心功能减退的标志。但轻度CA狭窄患者的STI可正常,这可能与静息时尚有足够的CA贮备力有关。     

无创伤心功能监护仪

近年来心功能指标的无创伤检测已日益引起国内外人士的关注,因为它安全、可靠,便于推广和应用。无创伤检测心功能指标的方法主要有:超声心动图,颈动脉搏动图指脉波和心阻抗法等等,这些方法都从不同角度和不同程度上实现了对心功能的无损伤检测。超声心动图得到的是心脏运动情况的切面图,图像清晰直观,但是仪器成本较高,不便作监护之用;颈动脉搏波和指脉波虽然方法简单,但一般只能测出STI指标,(包括Q-S_2,PEP,LVET等);而阻抗法其特点是方法简便。准确性较高,除了能够测出常     

急性心肌缺血对血液流变学和心脏收缩功能改变的影响

在麻醉开胸狗观察了急性心肌缺血对血液流变学和心脏收缩功能改变的影响。在阻断狗前降支冠脉1h内,血液流变学各参数发生异常变化,表现为高、低切变率下全血粘度(ηbh、ηb1)、血浆粘度、血细胞压积和纤维蛋白原升高,红细胞电泳时间缩短。同步描记心电、心音和颈动脉搏动图而记录的心脏收缩时间间期,表现为射血前期(PEP)延长、左室射血时间(LVET)缩短和PEP/LVET比值增大。此外,动脉舒张压(DAP)升高,心输出量(CO)减少。上述各参数均与对照值有明显差异,P<0.05。缺血40min时,对ηb1和PEP/LVET或DAP进行相关分析,呈明显正相关,P<0.05;ηb1和CO呈明显负相关,P<0.01。结果提示,心肌缺血后发生的血液流变学异常变化,具有增加射血阻力和减少心输出量的作用。     

应激状态下人群心脏储备的调研

目的:研究应激状态下人群心脏储备动用情况。方法:选择运动员81名进行心音图运动试验,分别记录其静息状态和运动后即刻的第1心音幅值与第2心音幅值之比(S1/S2)、舒张期与收缩期时限之比(D/S)和心率(HR);选择心血管病人以及对照组-健康人群各25名,健康孕妇320名(孕周≥28周)以及对照组-健康育龄妇女100名,记录静息状态下的S1/S2、D/S和HR。结果:运动员静息状态和运动后即刻S1/S2和HR升高,D/S降低,有显著性差异(P<0.01);心血管病人相对于健康人S1/S2和HR较高,D/S较低(P均<0.01)相对于健康育龄妇女,孕妇S1/S2和HR较高,D/S较低(P均<0.01)。应激状态下D/S比值会减低,S1/S2升高,HR越快。结论:应激导致心脏负担加重、会调用心力储备和心率储备,心脏功能上调。     

应激条件下人群心脏储备动用趋势的特征研究

目的:探讨应激条件下人群心脏储备动用趋势的复杂度特征。方法:应用运动心力监测仪采集运动员(A组,n=15)和普通大学生(B组,n=15)静息和不同负荷运动后即刻的心音信号,分析心动周期里心音信号的样本熵。结果:静息状态、1 750J、3 500 J、5 250 J、7 000 J 4种不同负荷后即刻运动员和普通大学生的心动周期心音样本熵值均呈下降趋势,且运动员样本熵值均低于普通大学生的。静息时两人群样本熵值未显统计学差异,而运动负荷后即刻表现出显著性差异(P0.05)。静息状态、1 750J、3 500 J、5 250 J、7 000 J 4种不同负荷后即刻运动员心率均低于普通大学生心率,而且普通大学生和运动员的心音样本熵与心率和运动负荷均呈显著(P0.05)相关关系,相关系数分别为-0.671和-0.745。结论:样本熵可以作为评估应激条件下人群心脏储备动用趋势的指标,且能区分普通大学生与运动员的心脏储备动用趋势差异。     

蝮蛇抗栓酶治疗冠心病

应用蝮蛇抗栓酶治疗15例冠心病患者,其中12例为慢性冠心病患者,3例为急性心肌梗塞患者.治疗结果表明:治疗后心电图示心肌缺血改善者达72.7%,心脏 B 超示室壁运动改善者达80%,心阻抗血流图示 PEP/LVET 明显下降,P<0.01,CI 明显增高.P<0.05,说明蝮蛇抗栓酶具有明显的改善心肌缺血和左心室功能的作用。     

应激状态下被检出第三心音的人群的调查研究

目的:调查研究应激状态下检出第三心音(S3)的人群及其心脏所受负荷的关系。方法:选择92名运动员和42名普通大学生进行心音图运动试验,分别记录其静息状态和运动后即刻出现的S3及心率。另选90名孕妇(孕周≥28周)和90名非妊娠育龄妇女作对照研究,记录静息状态下出现的S3和心率。分析两组人群检出S3的频率与心脏负荷的关系。结果:静息状态和运动后即刻检出S3的频率有显著性差异(P0.01),而运动员与普通大学生检出S3的频率无显著差异(P0.05)。孕妇与非妊娠育龄妇女静息状态下检出S3的频率有显著性差异(P0.01)。应激状态下的人群被检出第三心音的频率显著性增加。结论:第三心音的出现是心脏负荷加重所产生的一个反应。     

高原人体左心室舒张功能和顺应性的改变

应用同步描记心电图、心音图、颈动脉搏动图和心尖搏动图以测定高原人体的左心室舒张功能和顺应性。在4个不同海拔高度进行实验,即76m(海平对照)、2161m、3270m和4179m,每一高度40名健康男性青年,高原3组世居、移居各20名。结果显示:随着海拔增高,主动舒张时间指数(TRTI)有减小趋势,RF波相对振幅(F/H)逐渐降低,A波相对振幅(A/D)则渐趋增大,3270m以上增大明显(p<0.05),舒张振幅时间指数(DATI)逐渐降低,3270m以上差异极显著(p<0.001)。高原世居与移居者相比,在海拔4179m出现明显差别,移居组TRTI、DATI、F/H较低而A/D较高(D<0.05)。测定射血前期与左室射血时间比值(PEP/LVET)、射血分数(EF)及左室周径纤维平均缩短速度(mVcf)3项指标作对照,显示在此高度左室收缩功能仍能保持。高原慢性心肌缺氧可能是导致左室舒张功能和顺应性轻度降低的原因。     

Effect of static exercise and muscle ischemia on cardiac function as evaluated by the systolic time intervals

To determine the role of muscle chemoreflex in the cardiac response to static exercise the effect of the forearm muscle ischemia on systolic time intervals (STI), heart rate (HR) and blood pressure (BP) recovery following static handgrip was studied in 7 healthy men. During handgrip maintained for 4 min at 30% maximal voluntary contraction HR and BP increased significantly while duration of the pre-ejection period (PEP) and isovolumic contraction time (ICT) were shortened with a significant lowering in the ratio of PEP to the left ventricle ejection time (LVET). Occlusion of the circulation to the forearm muscles for 2 min after cessation of exercise did not prevent a rapid decline of HR or increment in PEP, ICT and PEP-to-LVET ratio while BP remained elevated for as long as blood flow to muscles was restricted. The study failed to demonstrate an appreciable effect of muscle chemoreflex on HR or myocardial contractility, suggesting that input from muscle afferents activated by metabolic stimuli induces the pressor response mainly by the peripheral vasoconstriction.     

Systolic time intervals in burn injury

Systolic time intervals were studied in 28 young, previously healthy burn patients (TBS 10-90%) on 145 occasions. A NEK 116 type 3 channel recorder of 100 mm/sec paper speed was used. Synchronous ECG recordings in lead II, PCG in the m "1" frequency band, and external carotid pulse tracings were recorded. RR, QS2, S1S2, LVET, PEP, PEP/LVET and QT, QTc, QS2-QT intervals were measured in 5-10 cardiac cycles in each of the examinations. Calculation of the additional parameters ICT, LVET/ICT, DT, EVR, PRP, EF and SV values were correlated to the extent of, and the time elapsed since, burn injury. The derivated parameters and statistical analysis were performed on a Commodore 64 type computer based on a software program. Elongation of QTc (greater than 440 msec) and frequent electrodynamic failure (QT-QS2 greater than 40 msec) especially during the first postinjury week were found characteristic in severe injury. In 53% the PEP/LVET ratio was less than 0.31, mean 0.32 +/- 0.093. In 21 cases of severe hypovolaemia the increase of PEP raised this value beyond 0.41. With the exception of 3 examinations, QS2I was normal or shortened. Calculated EF were normal or increased, SV reduced being interdependent with burn extent and shortening of DT. In patients with severe burns, oxygenization was inadequate (EVR less than 0.8); it showed an inverse correlation to HR. The simultaneously high LVET/ICT ratio and shortened ICT values pointed to an increase in contractility.     

Dynamics of changes in the cardiovascular response to submaximal exercise during low-intensity endurance training with particular reference to the systolic time intervals

Eighteen male volunteers (aged 20-23 years), not involved in any sporting activities, were submitted to 13 weeks of training consisting of 30 min exercise [at 50%-75% maximal oxygen intake (VO2max)] on a cycle ergometer, performed 3 times a week. Every 4 weeks cardiac function was evaluated by measuring the systolic time intervals at rest and during submaximal cycle exercise. Stroke volume (SV), heart rate (HR) and blood pressure (BP) responses to submaximal exercise, VO2max and anaerobic threshold (AT) were also determined. Significant increases in VO2max, increases in AT and SV at the submaximal exercise intensities, as well as decreases in HR and BP were found after 4 weeks of training. Resting systolic time intervals were not affected by training, but during the submaximal cycle exercise the values of the pre-ejection period (PEP) and isovolumic contraction time (ICT) corresponding to HR of 100 beats.min-1 were significantly lowered after 13 weeks of training, whereas PEP, ICT and total electromechanical systole corresponding to HR of 130 beats.min-1 were significantly shortened by the 4th week. The ratios of PEP:LVET (left ventricular ejection time) and ICT:LVET during submaximal exercise were significantly lowered by training starting from the 8th week. These changes might be interpreted as evidence of the training-induced enhancement of the "contractility reserve", i.e. the ability to increase heart muscle contractility with increasing exercise intensity.     

Ultra short-term heart rate recovery after maximal exercise: relations to aerobic power in sportsmen

The main aim of the study was to investigate whether different levels of aerobic power influence heart rate (HR) responses during the first minute of recovery following maximal exercise in athletes. Thirty-two young male soccer players were recruited for the study during the final week of their training prior to [corrected] the competition. Following the maximal exercise on treadmill the participants were placed supine for 60 s of HR recording. The time between exercise cessation and the recovery HR measurement was kept as short as possible. At the end of exercise (i.e., the start of recovery), HRs were [corrected] was similar in both trials. At both 10 s and 20 s of recovery period, the players characterized by high aerobic power (> 60 ml/kg/ min) revealed significantly lower HR as compared to their sub-elite counterparts (< 50 ml/kg/min; P < 0.05). No differences between the groups were found at later stages of the analyzed post-exercise HR. The data suggest that the athletes characterized by high aerobic capacity could be better adapted to maximal exercise with faster recovery HR immediately following an exercise test. These results generally suggest that the aerobic power along with autonomic modulation might have played a role in the ultra short-term cardiovascular responses to all-out exercise.     

Adaptation of the circulatory system to frequently repeated submaximal workloads in the light of left ventricular contraction analysis

In two groups of healthy men aged 20-22 years the left ventricular systolic time intervals were evaluated by the method of Weissler et al. during frequently repeated workloads and restitution. Each exercise was carried out on a Zimmerman cycle ergometer during 10 minutes, and was repeated five times at 50-minutes intervals from 8.00 o'clock a.m. Group I (15 subjects) performed the exercise at a stable workload which produced during the first exercise heart rate acceleration to 170/min, but gave a successive further rise in the heart rate during consecutive exercises. Group II (11 subjects) performed all exercises to a stable rise in heart rate to 170/min with decreasing workloads. It was found that successive exercises caused in both groups a similar decrease of the left ventricular ejection time index (LVETI), pre-ejection period (PEP), isovolumetric contraction time (ICT), and decrease of the PEP/LVET index (p less than 0.05). Each successive exercise began with higher values of LVETI, PEP, ICT and PEP/LVET than the first one. No significant differences were found in the values of left ventricular systolic time intervals in both groups (p greater than 0.05). The duration of restitution of normal values of the left ventricular systolic time intervals after successive exercises was not changing but the tolerance of these exercises measured by heart rate increase and work performed decreased successively.     

Cardiovascular, metabolic and plasma catecholamine responses to passive and active exercises.

Eight healthy male volunteers (aged 19.6+/-3.0 years) were submitted to the unloaded active (AE) and passive (PE) cycling exercise-tests performed on an adapted cycle ergometer at a pedalling rate of 50 rpm. Intensity of active exercise was about 10% of VO2 max. In the PE exercise test the ergometer was moved electrically. During both tests the systolic time intervals (STI), stroke volume (SV), heart rate (HR), blood pressure (BP), oxygen uptake (VO2), rating of perceived exertion (RPE), electrical muscle activity (EMG), plasma adrenaline (A), noradrenaline (NE) and blood lactate (LA) concentrations were measured. Exercise induced changes in VO2, RPE and EMG were significantly higher during AE than PE. Shortening of the pre-ejection period (PEP) and diminishing of the PEP to ejection time (ET) ratio were similar in both types of exercise, whereas HR increased only during AE. A significant increase in cardiac output (p<0.01) resulted from increased SV (p<0.01) during PE and from increased HR (p <0.01) during AE. MAP increased only during PE and it was higher than at rest and during AE (p<0.01). Absence of changes in SV and MAP during AE may be considered as a secondary effect of the decrease in TPR. Plasma catecholamines did not increase above resting values in either type of exercise. Blood LA concentration increased during both PE and AE but it reached higher values (p<0.01) after the latter test. The present data suggest that the inotropic state depends on the mechanoreflexes originated in skeletal muscles. However, contribution of changes in preload to shortening of PEP can not be excluded.     

Polycardiographic evaluation of left ventricular function in the elderly]

Polycardiographic recordings have been carried out in 57 individuals (16 men and 41 women), aged between 70 and 97 years (mean age 78.3 years), both at rest and during the stimulation of circulatory system by the cooling of hand. Systolic time intervals of the left ventricle and QT/QS2 ratio have been evaluated. It was found, that systolic time intervals at rest did not differ significantly from those given by Weissler. Cooling of hand has been manifested by: prolongation of LVETI, decrease in PEP/LVET, prolongation of QS2I, and decrease in QT/QS2. Results suggest indirectly that myocardium of the elderly adapts to the stimulation through Frank-Sterling mechanism.     

Variation of cardiac cycle during prolonged cycling exercise

The purpose of this study was to elucidate the changes in heart rate (HR), systolic and diastolic time intervals accompanying prolonged cycling exercise. Seven healthy male students (N group) and seven male collegiate long distance runners (LDR group) underwent 60-min bicycle ergometer exercise loaded at 30% and 50% HRmax. Electrocardiogram (ECG) and phonocardiogram (PCG) were recorded throughout the exercise and recovery period, and then left ventricular ejection time (LVET) and left ventricular diastolic time (LVDT) were calculated from tracings of the cardiac cycle. In the N group, HR increased to the target HR level (30% and 50% HRmax) in the initial phase of exercise, but there was a tendency to increase 10-15 b/min in the latter half of the exercise period. The LDR group showed the same trend as in the N group at 50% HRmax level (i.e., 120 b/min) exercise. These increments of the HR were due to the decrease of stroke volume, the elevation of body temperature and changes in the volume of the venous return. In the initial phase of exercise (within five minutes), LVDT decreased markedly resulting in a rapid increase of the HR in both groups. The decrease in LVDT was 250-400 msec (60-70% decrement for resting value) at the 30% HRmax level load and 270-480 msec (73-80% decrement for resting value) at the 50% HRmax level load, and then transient slight increment was recognized. Subsequently, there was a tendency to decrease. The major factor for the increase of the HR was that the LVDT decreased markedly that implied the shortening of the inflow time to the left ventricle.(ABSTRACT TRUNCATED AT 250 WORDS)