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Electrocardiogram, ECG

Electrocardiogram, ECG. Produced by JingquanGao April 19,2006. Blood circulation. Cardiac electrical activity. Electrocardiogram (EKG or ECG).

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Electrocardiogram, ECG

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  1. Electrocardiogram,ECG Produced by JingquanGao April 19,2006

  2. Blood circulation

  3. Cardiac electrical activity

  4. Electrocardiogram (EKG or ECG) • What is it?An electrocardiogram – abbreviated as EKG or ECG – is a test that measures the electrical activity of the heartbeat. With each beat, an electrical impulse (or “wave”) travels through the heart. This wave causes the muscle to squeeze and pump blood from the heart.

  5. The Heart is a pump has electrical activity (action potentials) generates electrical current that can be measured on the skin surface (the EKG)

  6. What is the function of ECG • In an ECG test, the electrical impulses made while the heart is beating are recorded and usually shown on a piece of paper. This is known as an electrocardiogram, and records any problems with the heart's rhythm, and the conduction of the heart beat through the heart which may be affected by underlying heart disease.

  7. At rest, Vm is constant No current flowing Inside of cell is at constant potential Outside of cell is at constant potential A piece of cardiac muscle inside ------------------------------ ++++++++++++++++++ outside - + Currents and Voltages 0 mV

  8. During AP upstroke, Vm is NOT constant Current IS flowing Inside of cell is NOT at constant potential Outside of cell is NOT at constant potential A piece of cardiac muscle AP inside ++++------------------------ ------++++++++++++++ outside current - + Currents and Voltages An action potential propagating toward the positive ECG lead produces a positive signal Some positive potential

  9. inside ++++------------------------ ------++++++++++++++ current - + A negative voltage reading More Currents and Voltages A piece of cardiac muscle An action potential propagating Away from the positive ECG lead produces a negative signal outside

  10. During Repolarization A piece of totally depolarized cardiac muscle A piece of cardiac muscle inside inside +++++++++++++++++++ ------------------------------- ------------+++++++++++ outside Vm not changing No current No ECG signal +++++++------------------- outside current Some negative potential - + More Currents and Voltages Repolarization spreading toward the positive ECG lead produces a negative response

  11. EKG

  12. 心电图运动负荷实验 平板运动实验 踏车运动实验

  13. 运动试验的生理和病理基础 生理情况下，运动时为满足肌肉组织需氧量的增加，心率相应加快，心排出量相应增加，而必然伴随心肌耗氧量增加，冠状动脉血流量增加。当冠状动脉发生病变而狭窄到一定程度时，病人在静息状态下可以不发生心肌缺血，但当运动负荷增加伴随心肌耗氧量增加时，冠状动脉血流量不能相应增加，即引起心肌缺氧，心电图上可出现异常改变。心肌耗氧量与心率快慢、心室大小、室壁张力、室内压力增加速度及心室射血时间有关。 运动负荷量分为极量与亚极量两档，以最大心率为指标。 最大心率粗略计算法为：220-年龄数； 亚极量是指心率达到85%-90%最大心率的负荷量，临床多采用该种。

  14. 运动平板心电图监测 冠状动脉粥样斑块形成，导致冠状动脉血供减少，心肌缺血。然而，有部分冠状动脉已有病变者，在安静时并不出现心肌缺血的心电图改变，临床症状不典型，体检无异常。而另一方面，出现了异常心电图表现，又不能肯定就是冠心病所致。 为提高冠心病诊断的敏感性和准确性，医生常采用一些运动负荷试验，让受检者进行一定量的运动，以使心脏作功负荷增加，同时监测因诱发而产生的一过性心肌缺血或心肌缺血加重，一过性心电图异常表现等。目前常用的是活动平板试验，受试者在平板上做步行运动，运动量由改变平板的转速及坡度而逐渐增加，运动中连续心电图监护，间断记录心电图及测量血压，保证其安全。对正常人，由于心脏贮备功能很大，这些运动量不会引起心肌缺血，心电图也不会有很大改变。而冠心病的人就经受不了这种负担，由于运动使心肌对氧的需要增多，就可能出现缺血的心电图改变称为运动试验阳性。

  15. 运动试验的主要评价如下： 1. 协助早期轻型冠心病及隐匿性冠心病的诊断。2. 判别胸痛性质是否为心绞痛。3. 对冠心病病变程度的估测。大致判断冠心病药物疗效。4. 对陈旧性心肌梗塞病人预后的估测。5. 对心律失常的发现（运动后往往增加）和治疗疗效的评价。6. 人群冠心病普查筛选（用运动负荷率估测冠心病发病率）。7. 对心脏负荷能力的评价。8. 对外科、介入治疗效果的评价。9. 稳定性高血压的早期发现。10. 制定冠心病、非心脏病人的运动治疗方案，康复计划及预防性措施。

  16. 为使您的试验结果更加准确，请您注意以下事项：为使您的试验结果更加准确，请您注意以下事项： 1.在试验前遵医嘱最好停用影响心脏功能及心电图的药物2-3天，或遵医嘱服药。2.试验前一晚应充分休息，当日最好空腹或在餐后2小时进行运动试验。3.试验前一餐应清淡，不食油腻、咖啡、茶和酒类。4.没有任何急性和严重的症状。5.因该试验有一定的风险，运动开始前请您详细告知病史，认真听取讲解注意事项；运动中将自觉变化及时通知医师，以确保试验安全。6.穿着合适的衣裤，舒适的平底鞋。

  17. 动态心电图： 是一种可以长时间连续记录并编集分析心脏在活动和安静状态下心电图变化的方法。24小时动态心电图监护系统是一种可随身携带、24小时连续记录监测人体心电变化的心电监测设备。这些信息经处理系统处理后能系统记录留下心电图，医生根据心电图可以清楚地了解人体24小时心电活动的情况。

  18. 方法： 将磁带记录盒与病人胸部导联电极相联，供患者随身携带。另有一回放系统，通过它医生可于数分钟内将磁带所记录的心电图波形全部查阅，并报出心搏总数，异常心律的类型与次数，最终将心肌缺血的情况展现在图纸上。记录期间病人除洗澡外可进行各种活动，但病人或其家属应将病人监测当天的活动记录在日程活动表格上，以便对照在什么时候或多大活动强度情况下出现心律失常或缺血性改变，借此可指导病人安排今后的生活和工作。

  19. 目前动态心图较多地应用于： 1．晕厥、心悸的鉴别诊断，查出严重心律失常所引起的晕厥和心悸； 2．病态窦房结综合征，特别是发作性快慢交替心律； 3．监测急性心肌梗塞出院病人在高危险期（发病后6个月内）的心律变化，及时检出恶性心律失常，预防猝死； 4．诊断冠心病：分析活动、静息或睡眠中的心电图变化，提高论断阳性率； 5．心血管疾病的药物，特别是抗心律失常和抗心绞痛药物的临床研究。

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