SavR电压标准与Rv5（6）＋Sv1电压标准联用诊断左室肥厚的价值

该文探讨心电图aVR导联的S波电压在诊断左室肥厚（LVH）中的价值。方法：以超声心动图结果为诊断标准，测量LVH者60例（A组）及无LVH者40例（B组）的心电图RV5（6），＋Sv1电压和SaVR电压，计算RV5（6）＋SV1电压标准和SaVR电压标准（心电图诊断LVH的标准：1）SaVR≥1．5mV。2）Rv5（6）＋Sv1男≥4．0mV，女性≥3．5mV及两者联用标准诊断LVH的敏感性、特异性及准确性，并进行显著性检验。结果：     

S_(aVR)与R_(aVL)+S_(V_3)标准诊断左室肥大的价值

目的探讨SaVR与RaVL+SV3电压标准诊断左室肥大(LVH)的价值。方法以超声心动图结果为诊断标准,测量有LVH者100例(A组)及无LVH者100例(B组)的心电图(ECG)SaVR和RaVL+SV3电压。计算B组SaVR和RaVL+SV3电压的均数及标准差,获取诊断LVH的ECG新标准,并与传统标准比较,检验不同标准对诊断LVH的敏感度、特异度及准确度。结果①SaVR诊断LVH的灵敏度低(36%),特异度高(100%),准确度为68%;传统标准及RaVL+SV3诊断LVH的灵敏度提高(52%及58%),但特异度明显下降(70%及84%),准确度60%及71%。②两者联用诊断LVH的灵敏度及准确度提高,特异度无明显降低,分别为68%、76%、84%;③两者联用对诊断LVH伴电轴左偏者的灵敏度显著提高,为77.9%,准确度与特异度相近,分别为78.8%、82.3%;④两者联用在成人各年龄组中及不同体型中诊断LVH的价值无差异。结论SaVR及RaVL+SV3标准诊断LVH具有临床实用价值,两者联用则更为理想,可弥补单用的不足。     

S_aVR与R_aVL+S_V_3在诊断左心室肥大中的价值

目的探讨心电图（ECG）aVR导联的S波电压在诊断左心室肥大（LVH）中的价值。方法以超声心动图（UCG）结果为诊断标准，测量有LVH者100例（A组）及无LVH者100例（B组）的RaVL＋Sv3电压和SaVR电压，计算RaVL＋Sv3电压、SaVR电压及两者联用标准在诊断LVH中的敏感性、特异性及准确性。结果①SvVR电压诊断LVH的敏感性低（35％），特异性高（100％），准确性为67．5％；②RaVL＋Sv3电压诊断LVH的敏感性（60％）较SaVR电压的敏感性高，但特异性下降（84％），准确性为72％；③两者联用可提高诊断LVH的敏感性及准确性，特异性却无明显降低，分别为：69％、76．5％、84％；与QRS波电轴的关系：伴QRS波电轴左偏者，诊断LVH的敏感性显著提高，为77．9％，准确性与特异性相近，分别为：78．8％、82.3％；④两者联用的标准在成人各年龄组及不同体型者诊断LVH的价值差异无显著意义（x^2=3．021，x^2=1．916，P〉0．05）。结论SaVR标准诊断LVH具有临床实用价值，与RaVL＋SV3标准联用更理想，可弥补单用的不足。     

心电图对完全性左束支传导阻滞伴左心室肥大的诊断价值

目的探讨心电图对左束支传导阻滞(LBBB)合并左心室肥大(LVH)的诊断价值。方法分析30例LBBB合并LVH(A组)与30例单纯LBBB(B组)的心电图。结果A组SV3>SV2、SV1+RV5、SV1+RV6、SV3+RV6、QRS时间与B组比较有显著性意义(P<0.05)。SV3>2.7mV,敏感性为80%,特异性为75.3%,准确性为77.5%;SV3+RV6>4.3mV,敏感性为80%,特异性为60%,准确性为70%;SV3>SV2,敏感性为53.3%,特异性为86.7%,准确性为70%;QRS>0.15s,敏感性为53.3%,特异性为80%,准确性为67%。结论SV3>2.7mV、SV3+RV6>4.3mV、SV3>SV2、QRS时间>0.15s是LBBB合并LVH的有效心电图参数。     

SV5，值增大、SV6〉SV5对左心室肥大的诊断价值

目的探讨SV5值增大、SV6〉SV5对左心室月巴大（LVH）的诊断价值。方法经超声心动图（UCG）查分为LVH组（A组）120例和正常组（B组）90例,对其心电图相关指标进行对比分析,并计算各参数电压标准诊断LVH的敏感性、特异性和准确性。结果各参数电压标准对诊断LVH的特异性尚可,但敏感性较低。结论SV5值增大、SV6〉SV5与其它诊断条件综合应用,可提高心电图对LVH诊断的敏感性、特异性、准确性。     

SaVR与Rv5＋Sv1联用诊断高血压左心室肥大的临床价值

目的 探计心电图SaVR与Rv5＋Sv1联用诊断高血压左心室肥大的临床价值.方法 超声心动描记术诊断左心室肥大的高血压患者82例及无左心室肥大的健康人100例.测量SaVR和Rv5＋Sv1电压,计算SaVR、Rv5＋Sv1及两者联用诊断左心室肥大的敏感性、特异性及准确性.结果 SaVR诊断左心室肥大的敏感性低（45.0%）,特异性高（99.0%）,准确性为74.7%;而Sv5＋Sv1的敏感性（54.8%）较SaVR高,但特异性（85.0%）较低,准确性为71.4%;两者联用可明显提高诊断的敏感性及准确性（分别为87.8%、85.7%,均P〈0.01）.结论 SaVR与Rv5＋Sv1联用诊断高血压左心室肥大的敏感性和准确性较高.     

心电图C值在左心室肥大诊断中的应用

目的 探讨心电图(ECG)新标准C值在诊断左心室肥大(LVH)中的价值.方法 以超声心动图(UCG)结果为诊断LVH标准,对无LVH的健康人200例(A组)、有LVH之非健康者100例(B组)及无LVH非健康者100例(C组)的各项心电指标进行分析.计算A组SaVR及C值的均数及标准差,按照统计学原理确定其正常值范围,大于正常值上限作为ECG诊断LVH的新标准,并与传统标准[1]、罗氏等标准[2]比较,检验不同标准对诊断LVH的敏感性、特异性及准确性.结果 ①A组SaVR的电压均值(mm)为9.25±2.65,正常值范围为4～14; C值电压均值(mm)为男性24.88±6.78、女性19.46±6.52,正常值(mm)范围男性11～38、女性7～32.以SaVR>14;C值男性>38、女性>32作为ECG诊断LVH的新标准.②SaVR、C值、传统标准及罗氏等[1]标准诊断LVH的价值比较:敏感性分别为37%、75%、52%、61%;特异性分别为99%、92%、70%、90%;准确性分别为68%、83.5%、60%、77.5%.③C值男性>38mm、女性>32mm同时有QRS波电轴左偏或ST～T改变者诊断LVH的敏感性、准确性及特异性分别为88.6%、89.7%、94.1%;C值男性>38mm、女性>32mm无QRS波电轴左偏或ST-T改变者诊断LVH的敏感性、准确性及特异性分别43.3%、78.8%、91.5%.④C值在成人各年龄组中及不同体型中诊断LVH的价值差异无统计学意义.结论 SaVR标准诊断LVH具有临床实用价值,新标准C值是传统标准及罗氏等标准很好的补充,可大大提高ECG诊断LVH的准确性.     

完全性左束支传导阻滞时Sv3〉Sv2、Rv6〉Rv5对左心室肥厚的诊断价值

目的　对 5 0例左束支传导阻滞 (LBBB)合并左心室肥厚 (LVH) (A组 )的心电图诊断 ,与 4 0例单纯完全性LBBB(B组 )对照。结果　A组RⅠ SⅢ 、SⅢ >RⅡ 、SV2 、SV3、SV3>SV2 、RV6 >RV5、SV1 RV5、S V3 RV6 、SV1 SV6 等指标 ,与B组相比P <0 0 1 ,SV3>2 7mV ,敏感性为 89 2 %,准确性为 85 3%,特异性为 87 9%;其次为SV3>SV2 ,敏感性为 5 8 1 %,准确性为 6 1 6 %,特异性为 73 6 %;SV3 RV6 >4 3mV ,敏感性为 6 8 8%,准确性为 6 3 7%,特异性为 74 1 %;RV6 >RV5,敏感性为 5 2 4%,准确性为 6 0 4%,特异性为 70 6 %。结论　SV3、SV3 RV6 >4 3mV、SV3>SV2 、RV6 >RV5、QRS >0 1 5s是LBBB合并LVH的有效参数。     

心电图RavL+Sv3电压诊断左室肥大价值探讨

目的探讨心电图RavL+Sv3电压在诊断左室肥大(LVH)中的临床价值.方法测定观察组250例和对照组230例的心电图传统标准电压和RavL+Sv3电压,计算其诊断LVH的敏感性、特异性、准确性.结果①与传统标准比较,RavL+Sv3标准及二者联用时,诊断LVH的敏感性、准确性显著提高,特异性相近;②随电轴左偏,RavL+Sv3电压诊断LVH的敏感性升高更显著,而特异性、准确性相近.结论RavL+Sv3标准及二者联用诊断LVH优于传统标准,并可弥补传统标准的某些不足.     

心电图RavL+Sv3电压诊断左室肥大价值探讨

目的探讨心电图RavL+Sv3电压在诊断左室肥大(LVH)中的临床价值。方法测定观察组250例和对照组230例的心电图传统标准电压和RavL+Sv3电压,计算其诊断LVH的敏感性、特异性、准确性。结果①与传统标准比较,RavL+Sv3标准及二者联用时,诊断LVH的敏感性、准确性显著提高,特异性相近;②随电轴左偏,RavL+Sv3电压诊断LVH的敏感性升高更显著,而特异性、准确性相近。结论RavL+Sv3标准及二者联用诊断LVH优于传统标准,并可弥补传统标准的某些不足。     

Electrocardiogram voltage discordance: interpretation of low QRS voltage only in the limb leads

Introduction

Low voltage on the surface electrocardiogram (ECG) is defined as QRS voltage less than 5 mm in all limb leads and less than 10 mm in all precordial leads. The clinical correlate of an ECG with low voltage in the limb leads but normal precordial QRS amplitudes is unclear.

Methods

Twelve-lead ECGs with QRS voltage less than 5 mm in all limb leads and more than 10 mm in at least 2 contiguous precordial leads were collected. Presence of clinical conditions associated with low voltage was determined from clinical data and chest imaging.

Results

Fifty-one of 100 patients had voltage discordant ECGs that correlated with conditions known to cause diffuse low voltage. Among those without associated conditions, 63% had dilated ventricles, with an average ejection fraction of 33%.

Conclusions

Low voltage isolated to the limb leads is associated with the same conditions that cause diffuse low voltage in only half of patients. In the remainder, more than 60% have dilated cardiomyopathies.     

Precordial voltage variation in the normal electrocardiagram

Intra-individual precordial voltage variation was examined in serial 12 lead electrocardiograms (ECGs) performed at 10 minute and 24 hour intervals in sixteen young, healthy males forming two age matched groups. Significant variation was found in repeat ECGs at both periods. When precordial electrodes remained in situ between serial 10 minute recordings variation was reduced by approximately 60%We conclude that significant precordial voltage variation is present in serial electrocardiography, even when performed over the short term. Alteration in precordial electrode placement accounts for the major proportion of variation and this may be sufficiently large to interfere with the accurate interpretation of serial precordial voltage changes in an individual subject.     

Electric fingerprint of voltage sensor domains

A dynamic transmembrane voltage field has been suggested as an intrinsic element in voltage sensor (VS) domains. Here, the dynamic field contribution to the VS energetics was analyzed via electrostatic calculations applied to a number of atomistic structures made available recently. We find that the field is largely static along with the molecular motions of the domain, and more importantly, it is minimally modified across VS variants. This finding implies that sensor domains transfer approximately the same amount of gating charges when moving the electrically charged S4 helix between fixed microscopic configurations. Remarkably, the result means that the observed operational diversity of the domain, including the extension, rate, and voltage dependence of the S4 motion, as dictated by the free energy landscape theory, must be rationalized in terms of dominant variations of its chemical free energy.Voltage sensor (VS) domains are electrically charged membrane proteins made of four packed helices (1). The fourth segment (S4) contains four highly conserved positively charged amino acids, R₁ through R₄. By interchanging its conformation between two main states (resting and activated) in response to voltage variations, VS domains displace the S4 charges across the membrane capacitance, giving rise to ΔQ, the so-called gating charge (2). As a result of their function of converting voltage variations into molecular motions, VS domains are ubiquitous in a number of electrically mediated processes, either as domain components of phosphatases (2) or proton (3) and ion channels (4–8).Despite the conservation of S4 sequences, nature has designed a variety of constructs (2) that present a wide range of voltage dependence and absolute rates of activation. For instance, the VS kinetics is markedly distinct between voltage-gated Na⁺ and K⁺ channels (9), a feature that complies with their respective role in the fast and slow phases of the action potential. Drastic kinetic shifts can even be observed in VS differing by point mutations (10, 11). In all of these constructs, the S4 operation results from the fine balance between the chemical and the electrical components of the relative free energy of the segment. Whereas the former depends on the S4 energy in the absence of an electrical driving force, the latter arises essentially from ?(r) (12), a dimensionless scalar field that reports the fraction of the membrane voltage coupled to every S4 charge q_i. As mostly embodied in the transporter model (13), the reshaping of ?(r) along with S4 displacements appears as one potential mechanism impacting the sensing process. Facing the VS diversity, it has been unknown to which extent the field reshaping may impact the S4 operation in distinct constructs and account for its energetic differences.Here, by benefiting from an increasing number of atomistic structures of VS-containing channels or enzymes made available recently, we use all-atom molecular dynamics (MD) simulations (14–16) in combination with electrostatic calculations (17, 18) to investigate voltage-coupling properties of sensor domains. Anticipating our results, we find that, although primarily conformation independent, ?(r) is minimally modified over the VS variants. This finding points to marginal dynamic contributions of the membrane voltage field to the energetics and diversity of VS proteins.     

Routine reduction of pulse generator voltage

The porous-tip electrode has led to a significant advancement in pacing system technology. Experience with 38 patients with unipolar tined CPI porous endocardial electrodes, is reported. All patients had programmable pulse generators, CPI model number 531. The voltage in this pulse generator can be reduced from 5 to 2.5 volts. The pulse width threshold (PWT) at implantation was 0.06 ms at 5 volts in all 38 patients, and the PWT at implantation varied between 0.06 and 0.16 ms at 2.5 volts, with a mean PWT of 0.092 +/- 0.026 ms. The 38 patients were restudied six months later. The mean PWT measured at 5 volts was 0.076 +/- 0.018 ms. The PWT measured at 2.5 volts varied between 0.08 and 0.30 ms with a mean PWT of 0.178 +/- 0.067 ms. Twenty-three patients were restudied one year after lead implantation. The PWT measured at 2.5 volts varied between 0.08 and 0.30 ms with a mean PWT of 0.156 +/- 0.061 ms. All of the pulse generators were reprogrammed to 2.5 volts. This permitted a substantial prolongation of the pulse generator life (three to five years) with an improvement in the cost effectiveness of the pulse generator.     

Reduced voltage sensitivity in a K+-channel voltage sensor by electric field remodeling

Propagation of the nerve impulse relies on the extreme voltage sensitivity of Na⁺ and K⁺ channels. The transmembrane movement of four arginine residues, located at the fourth transmembrane segment (S4), in each of their four voltage-sensing domains is mostly responsible for the translocation of 12 to 13 e_o across the transmembrane electric field. Inserting additional positively charged residues between the voltage-sensing arginines in S4 would, in principle, increase voltage sensitivity. Here we show that either positively or negatively charged residues added between the two most external sensing arginines of S4 decreased voltage sensitivity of a Shaker voltage-gated K⁺-channel by up to ≈50%. The replacement of Val363 with a charged residue displaced inwardly the external boundaries of the electric field by at least 6 Å, leaving the most external arginine of S4 constitutively exposed to the extracellular space and permanently excluded from the electric field. Both the physical trajectory of S4 and its electromechanical coupling to open the pore gate seemed unchanged. We propose that the separation between the first two sensing charges at resting is comparable to the thickness of the low dielectric transmembrane barrier they must cross. Thus, at most a single sensing arginine side chain could be found within the field. The conserved hydrophobic nature of the residues located between the voltage-sensing arginines in S4 may shape the electric field geometry for optimal voltage sensitivity in voltage-gated ion channels.     

Tuning the threshold voltage in electrolyte-gated organic field-effect transistors

Low-voltage organic field-effect transistors (OFETs) promise for low power consumption logic circuits. To enhance the efficiency of the logic circuits, the control of the threshold voltage of the transistors are based on is crucial. We report the systematic control of the threshold voltage of electrolyte-gated OFETs by using various gate metals. The influence of the work function of the metal is investigated in metal-electrolyte-organic semiconductor diodes and electrolyte-gated OFETs. A good correlation is found between the flat-band potential and the threshold voltage. The possibility to tune the threshold voltage over half the potential range applied and to obtain depletion-like (positive threshold voltage) and enhancement (negative threshold voltage) transistors is of great interest when integrating these transistors in logic circuits. The combination of a depletion-like and enhancement transistor leads to a clear improvement of the noise margins in depleted-load unipolar inverters.