Noise in the signal-averaged electrocardiogram and accuracy for identification of patients with sustained monomorphic ventricular tachycardia after myocardial infarction

Late potentials are detected at various noise levels in clinicalstudies. The aim of this study was, in a case-control design,to assess the effect of residual noise level on the identificationof patients with sustained monomorphic ventncular tachycardiaafter myocardial infarction. Electrocardiograms from 16 patientswith prior myocardial infarction and documented sustained monomorphicventricular tachycardia and 41 patients with prior myocardialinfarction and without ventncular tachycardia, were analysedby two signal averaging procedures to noise level 0·2and 0·4 µV Standard time domain parameters weremeasured. Two definitions of late potential were analysed: (1)if any two of the following criteria were present (signal-averagedQRS duration >120 ms, late potential duration >40 ms,and root-mean-square voltage of the terminal 40 ms of the filteredQRS <25µV); or (2) if the signal-averaged QRS duration120 ms. Overall the signal-averaged electrocardiogram performedbetter at noise level 0·4µV compared to noise level0·2µV with respect to identification of patientswith or without ventricular tachycardia after myocordial infarction.Reducing noise level from 0·4 to 0·2 µVincreased the sensitivity, but the consequence was a substantialdecrease in specificity. Our data indicate that when a highsensitivity is the goal, the definition based only on signal-averagedQRS duration 120 ms should be applied; sensitivity was 88% andspecificity 59% at noise level 0·4 µV. If a highspecificity is the goal, the definition should be based on thedefinition with two abnormal parameters; sensitivity was 69%and specificity 68% at noise level 0·4µV.     

心电图在肺心病病程变化和预后判断中的作用

目的 :评价心电图在慢性肺心病肺动脉压力变化及判断预后中的作用。方法 :对150例进行过右心导管肺动脉压力测定和心电图检查的缓解期慢性肺心病患者随访观察5年 ,5年后对全部存活患者重复行右心导管肺动脉压力测定和心电图检查。结果 :(1)150例患者,5年随访期内死亡83例 ,病死率为55.33 %;心电图观察指标如QRS电轴≥90°、V1R/S≥1、R V1+S V5≥1.05mV在死亡组和存活组有明显差异 ,平均肺动脉压 (mPAP)大于30mmHg 者 ,其5年累积生存率明显降低。(2)25例平均肺动脉压 (mPAP)波动≥5mmHg 者 ,心电图均有改变 ,21例mPAP上升 ,4例下降 ,前者心电图改变呈右房室负荷增加 ,后者呈右房室负荷降低。结论 :(1)QRS电轴≥90°、V1 R/S≥1、R V1+S V5≥1.05mV等心电图指标出现或肺动脉压力大于30mmHg提示预后不良。(2)心电图随访可作为评估肺动脉压力动态变化的一种手段。     

心肌缺血对QT间期变异性的影响

目的 :探讨QT间期变异性 (QTV)在心肌缺血中的意义。方法 :对 37例动态心电图有明显心肌缺血和 42例无心肌缺血患者进行QT间期动态分析。结果 :心肌缺血组的QT间期变异性明显大于无心肌缺血组。结论 :心肌缺血影响QT间期变异性。     

高分辨心电图鉴别室速与预激综合征逆向折返性心动过速

目的 :应用高分辨心电图鉴别室性心动过速 (室速 )与预激综合征逆向折返性心动过速。方法 :对17例室律整齐的室速和12例预激综合征逆向折返性心动过速患者进行心电信号叠加高频滤波分析 ,观测QRS波与P波的关系。结果 :在心电信号叠加高频滤波图上 ,17例室速中16例未见P波 ,12例预激综合征逆向折返性心动过速者全部见到P波 ,两组差异有统计学意义 (P<0.001)。结论 :应用心电信号叠加高频滤波分析显示P波的方法有助于室律整齐的室速与预激综合征逆向折返性心动过速的鉴别诊断     

急性心肌梗死溶栓后ST段的下降幅度对预后的影响

目的探讨急性心肌梗死(AMI)溶栓后心电图ST段的下降幅度对预后的影响及进一步治疗的价值。方法将78例AMT患者按溶栓后60分钟、120分钟、180分钟、1天、3天等各时段记录的心电图ST段恢复情况,分为ST段基本回到基线(恢复≥90%)(A组)、ST段恢复50%≤恢复<90%(B组)和ST段恢复<50%(C组)。比较3组的住院心脏性病死率和左室功能,对ST段反复波动者、左室功能差者进一步治疗。结果C组较A组、B组CPK峰值、心脏性病死率和左室射血分数存在显著性差异(P<0.01),尤以A组预后最佳、左室功能良好,C组建议进一步行PTCA术及冠脉内支架植入术为多。结论心电图监测AMI溶栓后ST段的变化,有助于对预后评估并及时为高危患者进一步治疗提供依据。     

Meta‐Analysis of P‐Wave Dispersion Values in Healthy Individuals: The Influence of Clinical Characteristics

Background: P‐wave dispersion (Pd) is an appealing marker for predicting the risk of developing atrial fibrillation. At present, no definitive cutoff value has been determined as to the diagnosis of high‐risk patients. Our aims were to evaluate P‐wave parameters of healthy subjects published in the literature, determine normal range and weighted means of Pd and P‐wave parameters, and investigate the influences of gender, age, and BMI on the weighted results. Methods: A systematic search of studies published in PubMed was conducted. Only studies which included control groups of healthy individuals were included. Results: Of the 657 studies initially identified, 80 were eligible for inclusion. The total number of participants was 6,827. The highest reported Pd values were 58.56 ± 16.24  ms; the lowest were 7 ± 2.7  ms. The weighted mean was 33.46 ± 9.65  ms; weighted median was 32.2  ms. Gender and age were not found to be associated with significant influences on P‐wave parameter values. High‐normal BMI was not found to be associated with increased P‐wave parameter values. Conclusions: Pd, Pmax, and Pmin span a wide range of values in healthy individuals. Seemingly, abnormal values were often reported in healthy adults. The high variability of P‐wave parameters in healthy individuals, and overlapping of the results with those reported for patients with increased risk for atrial fibrillation, might suggest that this technique has limited sensitivity and specificity. The variability between studies may stem from methodological issues and, therefore, there is a definite need for methodological standardization of Pd measurements. Ann Noninvasive Electrocardiol 2012;17(1):28–35     

Augmented Vector Right ST-Segment Elevation: Pearls and Pitfalls

ST-segment elevation myocardial infarction (STEMI) is characterized by ST-segment elevation in at least 2 contiguous leads, chest discomfort, and the release of biomarkers requiring emergent revascularization. In 2013, the American College of Cardiology Foundation/American Heart Association revised STEMI guidelines to include augmented vector right (aVR) ST-segment elevation to be treated as a STEMI equivalent. However, aVR ST-segment elevation with multilead ST depression can occur in presentations other than occlusive myocardial infarctions. The purpose of this clinical feature is to provide a brief review of aVR ST-segment elevation, explore approaches to clinical decision making, and provide tools to support nurse practitioners caring for patients with cardiac issues.