成人左心辅助心电触发方式下辅助延迟时间的探讨

本文旨在寻找一个经验公式以有效地指导成人左心辅助装置触发延迟时间.目的:以R Ao代表心电QRS波峰点与主动脉瓣关闭结束的间隔时间,以RR代表RR间期,找出RR与R Ao的相关方程R Ao=A@(RR)n+B.通过加权平均法计算RR的平均值,再求出R Ao预期值,对R Ao做安全较正后,以此做为辅助的延迟时间.方法:选择14岁以上行升主动脉导管的成人患者,经筛选,测量877例心导管记录图中心电部分的RR间期以及与此心电对应的主动脉压力波形,测量主动脉下降波切迹与QRS波起始点间的间隔,以R Ao为因变量,以(RR)n为自变量,绘散点图,找出相关模型,并求出相关方程.结论:当心率小于120次/分时,相关系数为0.5066,回归系数为-0.0948,P值为1.968E 58;截距为0.655,P值为8.097E 109,相关方程为:R Ao=(-0.0948)RR 1/3+0.6551.     

心电RR间期序列的延迟时间研究

目的:探究心电RR间期序列的延迟时间的计算方法,并研究RR间期序列的延迟时间与其复杂度及年龄的关系。方法:以年轻(21~34岁)与年老(68~81岁)二组健康人的心电RR间期时间序列为实验数据,采用等概率符号分析方法计算其互信息,再按互信息极小原则确定其延迟时间。结果:年老组的延迟时间明显大于年轻组的(P0.015),并使用统计检验对其延迟时间与近似熵的分析,得出二者呈很强的负相关性(P-0.6)。结论:结果表明,RR间期序列的延迟时间直接反应了心电RR间期序列的复杂性特征,其大小与心率变异活动性和心血管的复杂程度负相关。     

双心室辅助对缺血性左右心功能不全血流动力学影响的实验研究

比较在缺血性左右心功能不全时左心辅助和双心室辅助对血流动力学的不同影响 ,为自制气动隔膜泵(罗叶泵 )的临床应用提供实验依据。采用 8只健康成年犬 ,植入左心辅助装置和右心辅助装置。结扎左前降支 ,3mins后在窦房结支发出处远侧端结扎右冠状动脉 ,以建立缺血性左右心功能不全的动物模型。先行左心辅助 5mins,再行双心室辅助。分别记录中心静脉压 ,心输出量 ,平均动脉压 ,肺动脉压 ,肺毛细血管楔压等血流动力学指标。结果表明 :双心室辅助时心输出量显著上升 (0 .82 2± 0 .0 9L / min vs 1.33± 0 .12 L / m in,P<0 .0 1)与正常对照值相比无显著差异 ;平均动脉压上升达正常范围 (37.4± 8.8mm Hg vs 84.2± 9.7mm Hg,P<0 .0 1) ;中心静脉压显著下降 (14.6± 2 .3cm H2 O vs 4.2± 1.5 cm H2 O,P<0 .0 1) ;肺动脉压无显著性变化 ;肺毛细血管楔压下降 (14± 3.9vs 1.6± 0 .9mm Hg,P<0 .0 1)。结论是全心功能不全时 ,单纯应用左心辅助并不能有效地改善血流动力学状况 ,应用双心室辅助可提高心输出量和动脉压至正常水平 ,可最大限度地减少心脏作功 ,降低氧耗 ,促进心肌组织的修复和代谢。因此 ,在左右心功能明显受损对药物和主动脉内球囊反搏 (IABP)治疗无效时 ,单行左心辅助应慎重 ,双心室辅助是推荐     

左心辅助对犬右心室的影响

目的 :观察左心辅助对犬右心室的影响。方法 :2 1条健康犬按不同左心辅助流量随机分为 3组 ,每组 7条。Ⅰ组辅助流量为 5 0ml·kg- 1 ·min- 1 ;Ⅱ组辅助流量为 70ml·kg- 1 ·min- 1 ;Ⅲ组辅助流量为 90ml·kg- 1 ·min- 1 。应用气动左心辅助装置行左心房至升主动脉辅助 5h。观察辅助前 ,辅助 5h ,停辅助 10min等时间位点的右心血流动力学变化。结果 :辅助 5h ,Ⅰ、Ⅱ、Ⅲ组左房压 (LAP) ,平均肺动脉压 (MPAP) ,全肺阻力 (TPR) ,右室最大压力上升速率 (Rvdp dtmax)均较辅助前明显减小 (P <0 0 5 ) ,且辅助流量越大下降幅度越明显 (P <0 0 5 ) ,Ⅰ、Ⅱ组右心排血指数 (PCI)较辅助前明显增高 (P <0 0 5 ) ,Ⅲ组无明显变化 (P >0 0 5 ) ,Ⅰ、Ⅱ组右心搏动指数 (RCWI)无明显变化 (P >0 0 5 ) ,Ⅲ组明显减小 (P <0 0 5 ) ,停辅助 10min时各组右心血流动力学指标均恢复至辅助前 (P >0 0 5 )。结论 :左心辅助流量越大对右心血流动力学影响越明显 ,短期左心辅助不会导致右心室的功能减退     

左心辅助循环后心肌功能恢复的预测研究

左心辅助装置 (left ventricular assist device,L VAD)作为一种重度心衰的抢救措施及等待心脏移植阶段的过渡支持 ,近年来已取得长足进步 ,临床应用的病例数不断增加 ,抢救了许多濒死患者的生命。患者是否可以撤离 L VAD,何时撤离 L VAD,目前主要依据患者心功能的恢复情况而定。能否在用 L VAD前通过测定一些简单的、无创伤的指标来预测患者的愈后 ,该用什么指标 ,这对于临床有着重要意义 ,然而这些问题尚未弄清楚。本文就该方面研究的近况作一综述     

心电图各波的逐拍形态差异分析

对心电数据库中的正常人、心绞痛病人和心肌梗塞病人的体表心电图进行分析,得到P波、QRS波和T波的形态差异序列和RR间期序列,用DFA(Detrended fluctuation analysis)方法分析其变异性。结果表明,从正常态到病态RR间期的DFA指数的变化模式同P波、QRS波和T波形态差异序列的DFA指数的变化模式不同。三种状态下RR间期的DFA指数都近似为1,从正常态到病态没有明显不同。而P波、QRS波和T波形态差异序列的DFA指数正常态近似为0 .5 ,且从正常态到病态呈减小趋势。     

一种基于单通道腹部信号的胎儿心电提取算法

设计一种基于单通道孕腹部信号的胎儿心电提取算法,分别提取出母亲心电和胎儿心电,并计算出母亲心率和胎儿心率。首先对单通道孕腹部信号进行k-TEO(k=19)变换,突出母亲心电的QRS波,从而通过简单的阈值法确定母亲心电的R波位置,接着通过在相邻R波间重采样以获得相同的R-R间期T,这样经过一个间隔为T的梳状滤波器就可以分离出相同R-R间期的母亲心电,然后再一次在相邻R波间进行重采样恢复原来的R-R间期就可以获得实际的母亲心电了。原始腹部信号减去上面提取的母亲心电后,胎儿心电QRS波的信噪比大大提高,通过再次应用提取母亲心电的算法即可得到“干净”的胎儿心电波形。选取Physionet数据库中的8 组(26 通道)孕腹部信号数据进行分析,计算每个通道数据的胎儿心电QRS波位置识别灵敏度、阳性检测率和准确性。结果表明,胎儿心电QRS波的识别准确率达到87.1%,其中有6 个通道达到100%。另外计算每个通道的母亲心率和胎儿心率并做统计分析,发现每一组中各个通道的母亲平均心率和胎儿平均心率都非常接近,同一组中各通道间母亲平均心率最大误差为0.1次/min, 而胎儿平均心率最大误差也只有0.9次/min,进一步证明算法的可靠性。     

轴流血泵对心衰动物的辅助试验研究

选择 2 0只雄性健康成年绵羊 ,采用结扎冠脉方法建立心衰模型后 ,随机分为两组 ;心衰后实验组运用自制轴流血泵进行左心辅助 ,分别在结扎冠脉前、心衰后和左心辅助 1h测量两组动物各项血液动力学参数 ,探讨血泵的动力学输出和对衰竭心脏的辅助功能 ,并取标本进行光、电镜检查。通过测试实验组血液的FHB、Fib和主要器官的栓塞情况 ,观察血泵对血液的破坏程度。结果得出 :(1)选择性结扎冠脉比较适合作为LVAD的左心衰动物模型。 (2 )血泵的压力、流量输出能够达到辅助要求 ,血泵辅助流量可占总流量的 10 0 %。 (3)并联于左心房和腹主动脉的血泵是通过部分分流和提高主动脉舒张压方式促进心肌的恢复 ;病理检查结果与血液动力学结果推测一致。 (4 )实验组短期在体试验辅助 2 4h ,标准溶血指数NIH为 0 .0 8g/ 10 0L ,试验结束肾脏有散在白色斑块 ,血泵的进、出口与管道接口处覆盖一层薄薄白膜 ;血泵表面温度变化较小。     

新型气动左心辅助循环装置动物存活实验

目的　应用自行研制的气动左心辅助泵 (罗叶泵 )进行动物存活实验 ,探讨其对血流动力学、血液有形成分和肝肾功能的影响及其临床应用的可行性 ;方法　健康山羊 12只 ,体重 2 9.7～ 39.4kg ,平均 34.1kg ,从左心房至降主动脉间转流 ,进行左心辅助循环 (LVAD) ,辅助频率为 6 0次 /分 ,流量为 2～ 3L/min ;结果　本组山羊LVAD时间为 13～174小时 ,平均 89小时 ,LVAD过程中 ,动物血压、中心静脉压稳定 ,尿液正常 ,肝肾病理检查未见坏死及出血灶 ;肌酸激酶同功酶、乳酸脱氢酶在辅助 4 8小时较术前明显升高 ,分别为 396 8.70± 15 6 1.2 5U/L ,2 0 18 0 0± 6 4 9 12U/L ,但 72小时后逐渐恢复正常 ,游离血红蛋白LVAD 4 8小时为 4 81 12± 116 .16mg/L ,在LVAD 72小时降至正常范围 (2 91.13±12 1.13mg/L) ;结论　罗叶泵能有效地维持血流动力学稳定 ,性能稳定、可靠 ,说明该血泵已具备条件进行短期临床试用     

携带式远程实时心电监测仪在心律失常诊断中的应用

目的通过与动态心电图（Hoher）记录的心电图比较,检验携带式远程实时心电检洲仪（AKM—N1型,简称心电检测仪）临床应用的价值。方法选取2011年10～11月存北京安贞医院心内科住院和门诊以心律失常为主要表现的心脏病患者36例,其中男性2l例,女性15例,平均年龄（43．0±14．8）岁。所有人选患者同时行心电检测仪和Holier监测,比刈’两行同步记录的心电蚓数据（包括P波时限、PR间期、QRS波群时限、QT间期、RR间期、有无伪差与干扰、有无心律失常及心律失常类,型）足否一致。两组分别选取相同时间点比对上述参数,包括记录的第10分钟、第20分钟、第30分钟、筇40分钟和第50分钟开始的30S心电数据,以及在受试者心脏不适或临床医生指示的情情下,2次同步按压两者的“捕捉键”进行心电捕捉的30S记录。结果36例入选患者有29例检测到心律失常。两种榆测方法得到的不同时间的P波时限、QRS波群时限、PR间期、QTM期与RR间期无差异,两种方法检出心律失常的情况高度关联（P〈0．001）,检出心律失常的比例无差异（P=1．0）。两种检测方法出现伪差与干扰的比例无差别,但出现伪差与干扰情况的关联性不肯定。临床试验过程无不良反应。结论携带式远程实时心电监测仪（AKM—N1型）获得的心电数据准确,对心律失常的诊断能力与Holter相当,借助网络传输,可及时指导患者治疗。     

Different sympathovagal modulation of heart rate during social and nonsocial stress episodes in wild-type rats

The acute consequences of a social aversive stimulus (defeat) on the autonomic control upon the electrical activity of the heart were measured and compared to those observed in three nonsocial stress paradigms, namely restraint, shock-probe test, and swimming. Electrocardiograms were recorded from rats via radiotelemetry, and the autonomic neural control of the heart was evaluated via measures of heart rate and heart rate variability, such as the average R-R interval (RR), the standard deviation of RR (SD), the coefficient of variance (SD/RR), and the root-mean-square of successive R-R interval differences (r-MSSD). Although all stressors induced significant reductions of average R-R interval, the effect of defeat was significantly larger (p < 0.05). The social stimulus also determined a significant decrease in the variability indexes (p < 0.01 for all), whereas in the other stress conditions they were either unchanged or increased (SD/RR during restraint, p < 0.05; SD and SD/RR during swimming, p < 0.05 and p < 0.01). Cardiac arrhythmias (mostly ventricular premature beats, VPBs) were far more frequent during defeat than during the other challenging situations (p < 0.01), with an average of 33.5 +/- 6.5 VPBs per 15-min test recording. These data suggest that during defeat autonomic control was shifted toward a sympathetic dominance, whereas in rats exposed to nonsocial stressors, although significant heart rate accelerations were also found, sympathovagal balance was substantially maintained. These differences in autonomic stress responsivity explain the different susceptibility to ventricular arrhythmias and indicate that a social challenge can be far more detrimental for cardiac electrical stability than other nonsocial aversive stimuli.     

Frequency distribution,variance, and moving average of left ventricular rhythm and contractility during atrial fibrillation in dog

Mean levels of left ventricular rhythm and contractility averaged over arrhythmic beats would characterize the average cardiac performance during atrial fibrillation (AF). However, no consensus exists on the minimal number of beats for their reliable mean values. We analyzed their basic statistics to find out such a minimal beat number in canine hearts. We produced AF by electrically stimulating the atrium and measured left ventricular arrhythmic beat interval (RR) and peak isovolumic pressure (LVP). From these, we calculated instantaneous heart rate (HR = 60,000/RR), contractility (E(max) = LVP/isovolumic volume above unstressed volume), and beat interval ratio (RR1/RR2). We found that all their frequency distributions during AF were variably nonnormal with skewness and kurtosis. Their means +/- standard deviations alone cannot represent their nonnormal distributions. A 90% reduction of variances of E(max) and RR1/RR2 required a moving average of 15 and 24, respectively, arrhythmic beats on the average, whereas that of RR and HR required 60 beats on the average. These results indicate that a statistical characterization of arrhythmic cardiodynamic variables facilitates better understanding of cardiac performance during AF.     

全数据库评估概率密度函数法利用R-R间期检测房颤精度

研究整个MIT-BIH心律失常数据库评估概率密度函数法利用R-R间期检测房颤的精度。研究发现正常窦性心律含较多早搏时[（早搏次数/总心搏次数）>9.3%],识别房颤的精度下降到约70%;左束支传导阻滞含较多早搏时,识别房颤的精度下降到约80%;而房颤心电中频繁早搏对辨别房颤精度影响很小,仍达91%。可见该算法适用于区分关联性强的序列与关联性弱的序列。正常窦性心律和左束支传导阻滞心律相邻R-R间期关联性强,频繁早搏使其相邻R-R间期关联性减弱,从而降低识别房颤的精度;而房颤相邻R-R间期无关联性,频繁早搏对检测精度无影响。尽管数据库中有种类繁多的心律失常,且伴有频繁的早搏,算法全数据库共约110 000次心跳辨别房颤精度达82%~86%。     

R-R interval-blood pressure interaction in subjects with different tolerances to orthostatic stress

In addition to the gain, the time delay in the input-output response in a feedback system is crucial for the maintenance of its stability. Patients with posturally related (vasovagal) syncope have inadequate control of blood pressure and one possible explanation for this could be prolonged latency of the baroreflex. We studied 14 patients with histories of syncope and poor orthostatic tolerance (assessed by a progressive orthostatic stress test) and 16 healthy controls. We performed spontaneous sequence analysis of the fluctuations of R-R period (ECG) and systolic arterial pressure (SAP, Finapres) recorded during a 20 min supine period and during 20 min 60 deg head-up tilt (HUT). The baroreflex latency was determined by identifying the lag between the changes in SAP and in R-R interval from which the highest correlation coefficient was obtained. During the supine period, 74% of sequences in control subjects and 54% in patients occurred with zero beats of delay (i.e. R-R interval changed within the same R-R interval). The remaining sequences occurred with delays of up to four beats. HUT shifted the baroreflex delay to be approximately one heartbeat slower and again patients showed more sequences with prolonged response. The delay in heartbeats was transformed into delay in time. In control subjects, 75% of baroreflex responses occurred within 1 s. In patients, 75% of baroreflex responses took more than 2 s to occur. The results showed that syncopal patients with poor orthostatic tolerance have increased baroreflex latency. This may lead to instability and inadequate blood pressure control and may predispose to vasovagal syncope.     

Investigation of the time delay between variations in heart rate and blood pressure

Relationships between fast variations in heart rate and blood pressure are known mainly to reflect parasympathetic activity. To assess parasympathetic function, relationships are investigated using a mutual information analysis, by assuming an information channel between blood pressure (BP) and inter-R-wave interval (RR) derived from the electrocardiogram. The differential sequences of BP and RR are coded into 'alphabets' for analysing fast variations. The averaged mutual information (AMI) is obtained as a function of delay d (beats) of the differential sequence of RR with reference to BP. The AMIs for supine and standing positions are compared. For 23 patients with renal failure, the AMI against d shows posture-independent and delayed-transfer characteristics from fast variations in BP to those in RR. The closest relationship is found with a 2-beat delay with an out of phase relationship. The 28 control subjects exhibit the 2-beat delayed transfer characteristics in the standing position, but are almost synchronous in the supine position. The mutual information analysis of the delay between fast variations in BP and RR explicitly shows a deficit in the parasympathetic regulation in the patients with renal failure.     

Investigation of the time delay between variations in heart rate and blood pressure

Relationships between fast variations in heart rate and blood pressure are known mainly to reflect parasympathetic activity. To assess parasympathetic function, relationships are investigated using a mutual information analysis, by assuming an information channel between blood pressure (BP) and inter-R-wave interval (RR) derived from the electrocardiogram. The differential sequences of BP and RR are coded into ‘alphabets’ for analysing fast variations. The averaged mutual information (AMI) is obtained as a function of delay d (beats) of the differential sequence of RR with reference to BP. The AMIs for supine and standing positions are compared. For 23 patients with renal failure, the AMI against d shows posture-independent and delayed-transfer characteristics from fast variations in BP to those in RR. The closest relationship is found with a 2-beat delay with an out of phase relationship. The 28 control subjects exhibit the 2-beat delayed transfer characteristics in the standing position, but are almost synchronous in the supine position. The mutual information analysis of the delay between fast variations in BP and PR explicitly shows a deficit in the parasympathetic regulation in the patients with renal failure.     

利用Lyapunov指数提取心电动态生理及病理信息的研究

对心电信号的研究，一般都集中在对个别异常波形进行检测和识别从而判断心脏病变方面。而心电波形及其Ｒ－Ｒ间期序列的Ｌｙａｐｕｎｏｖ指数反映了心脏的总体动态特征。利用ＭＩＴ－ＢＩＨ数据库进行的初步研究表明：１）正常人、室性失常病人和束支传导阻滞病人的心电波形的Ｌｙａｐｕｎｏｖ指数有显著差别；２）正常人和室性失常病人的Ｒ－Ｒ间期序列的Ｌｙｓｐｕｎｏｖ指数有显著差别，正常人和束支传导阻滞病人的Ｒ－Ｒ间期序列的Ｌｙａｐｕｎｏｖ指数没有显著差别。值得指出的是，这一研究的前景在于，当心电信号中的异常波形还不足以被识别时，有可能利用Ｌｙａｐｕｎｏｖ指数进行早期诊断。     

Sinus rhythm heart rate estimation in high noise environments by application of a priori RR interval statistics

Most existing heart beat detection algorithms serially process peaks, which can be either noise or true beats. Serial processing can result in inaccurate detections in the context of high noise. The proposed method relies on the relative regularity of sinus rhythm RR interval changes to select the best sequences of peaks in a 5–10?s long segment of cardiac data. The best sequences with a current data segment are subjected to a trending analysis, to determine whether their associated RR intervals fit within a pattern of prior best segments. The RR regularity scores and the results of the trending analysis are combined into a single sequence score and the final sequence for a segment is chosen from the best sequences based on this overall score. The current heart rate estimate is updated with the final sequence’s RR interval by an adaptive filter that weights the overall score. Twenty-four hour RR interval records for 54 normal individuals were parsed into 10-s segments and corrupted with spurious ‘noise’ peaks, which resulted in a revised RR interval series that included a number of false RR intervals. The algorithm was run on these corrupted RR interval series. The percentages of mean heart rate values within 5 beats min^?1 of the true value were 95%, 88% and 77% for 10, 20 and 30 added noise spikes, respectively. The percentages of mean heart rate values within 10 beats min^?1 of the true value were 98%, 96% and 91% for 10, 20 and 30 added noise spikes, respectively. Accuracy was higher for data segments characterized by relatively low RR interval variability. The proposed algorithm shows promise for estimating average heart rate for sinus rhythm in high noise environments.     

Autonomic function tests as related to age and gender in normal man

Summary To obtain a comparative assessment of 5 different clinical autonomic function tests as related to age and gender in normal man, the beat-to-beat variation during deep breathing (BBV), orthostatic 30/15 R-R ratio, heart rate response to the Valsalva manoeuvre, blood pressure response to sustained handgrip and orthostatic blood pressure response were evaluated in 120 healthy subjects (60 women and 60 men) aged 22 to 92 yrs. Each of the functional parameters depending on cardiac parasympathetic integrity, i.e. the beat-to-beat variation, orthostatic 30/15 R-R ratio and Valsalva ratio, decreased (P<0.0001) progressively with increasing age. The blood pressure response to handgrip, which depends on the efferent sympathetic function, was unchanged, while the orthostatic response of systolic blood pressure, which depends on the function of the entire reflex arch, was augmented only minimally (P<0.001) with increasing age. No significant dependence on gender was noted, although blood pressure responses to handgrip tended to be slightly greater in men than women. Beat-to-beat variation expressed as the standard deviation of the mean R-R interval correlated with mean heart rate (P<0.05), while the coefficient of variation and the exspiration/inspiration ratio of beat-to-beat variation did not. The orthostatic 30/15 R-R ratio and beat-to-beat variation tended to be more closely interrelated (r=0.56 to 0.63) than any of these tests with the Valsalva ratio (r=0.51). The findings indicate that consideration of age may improve the diagnostic value of the orthostatic 30/15 R-R ratio. Beat-to-beat variation expressed as exspiration/inspiration ratio may serve as a simple, complementary test of parasympathetic cardiac integrity, and the handgrip test as a sympathetic screening procedure which is also applicable in the geriatric age group.Abbreviations BBV beat-to-beat variation - BP blood pressure - SDRR standard deviation of mean R-R interval expressed in mm - SDHR standard deviation of mean R-R interval as translated into beats per min - CVRR coefficient of variation of R-R intervals This study was supported in part by the Swiss National Science Foundation     

Respiratory variability in R-R interval during sinusoidal exercise

The R-R interval varies with the cycles of respiration. The response of the variability in the R-R interval with respiration was examined during sinusoidal cycle exercise in 12 healthy young male subjects. Work rate varied sinusoidally between 30 W and 60% maximal oxygen uptake for an 8-min period. The higher the heart rate (HR), the smaller was the magnitude of the variation in R-R interval with respiration (ΔRR). When HR increased with an increase in exercise intensity, however, ΔRR tended to decrease more markedly at lower HR. On the other hand, since ΔRR generally increased linearly during the decrease in HR with a reduction in exercise intensity, ΔRR was greater during decreases in HR than during increases in HR at a similar HR. These results suggest that the contribution of the withdrawal of cardiac parasympathetic activity to increases in HR with increases in exercise intensity during sinusoidal exercise were greater at lower HR, and that the cardiac parasympathetic system was more activated during HR decreases than during HR increases at the same HR. From our findings it would seem that such complex parasympathetic HR regulaltion during sinusoidal exercise, which depends on the level of HR and the direction of the change in HR, may be influenced by factors other than the parasympathetic system, such as the cardiac sympathetic system.