AAI起搏心电图

AAI起搏心电图 在我国，AAI起搏器占整个植入起搏器数目的10%左右。随着对生理性起搏认识的增加，AAI起搏器的植入数目逐年增加。前面我们已经介绍了VVI起搏心电图，在此我们将讨论AAI起搏心电图。 一(AAI起搏器工作原理 心房单腔起搏器包括AAI、AAT和AOO起搏器，但后两者在临床上极少使用。AAI起搏器是指心房起搏、心房感知型起搏器，起搏器感知自身信号后的反应是抑制起搏脉冲的发放。尽管AAI起搏器的工作原理与VVI相同，但有其自己的特点。 1(电极放置的部位 AAI起搏器的电极导线放置在右心房的心耳部。正常情况下，右心耳位于右心房的前上方，内腔较小，表面有丰富的肌小梁。目前最常使用的是被动固定型J型电极导线，在放置时可很容易“钩住”肌小梁而固定。少部分病人采用主动固定电极导线，使右心房起搏的部位变异较大。 2(AAI起搏器的计时周期 ?基础起搏间期:基础起搏间期是指AAI起搏器正常工作时，在无自身心律的情况下连续两个起搏信号之间的时距(图1)。与基础起搏间期相对应的是基础起搏频率，两者为同一概念，只是表述不同而异。基础起搏频率(ppm)=60000?基础起搏间期(ms)。 ?逸搏间期:逸搏间期是指起搏信号与前一个自身P波之间的时距，即自身P波起始到下一个相邻起搏信号之间的时距。如果起搏器没有滞后功能或滞后功能没有打开，基础起搏间期应等于逸搏间期。在实际起搏心电图上，逸搏间期常略长于自动起搏间期，其机制与VVI起搏器相似。 基础起搏间期和逸搏间期均可以程控。根据临床需要，可将起搏器设置为负性频率滞后或正性频率滞后。设置为负性频率滞后时,逸搏间期长于基础起搏间期;反之，逸搏间期短于基础起搏间期。 ?心房不应期:指起搏器在发放一次电脉冲后或感知一次自身P波后，感知线路关闭，不感知任何心电信号的间期(图1)，通常为300,500ms。不应期的设置可以防止感知起搏器的起搏脉冲本身、起搏产生的极化电位以及自身的QRS波。 ?磁铁频率 进行磁铁试验时，AAI起搏器的起搏模式多为AOO，此时的起搏频率称为磁铁频率。磁铁频率的特点和作用与VVI起搏器相似。 图1 AAI起搏器计时间期 前3个P′波由起搏脉冲夺获心房产生，在第3个起搏脉冲发出后635ms感知到自身窦性P波(P4波)，起搏器以此点为起点重新按照857ms的间期发放下一次冲动。因此感知使起搏器发生节律重整 二(AAI起搏心电图特点 for computer software engineering GB/T50314-2000 of electrical installations code for construction and acceptance of GBJ232- 92 intelligent building weak design construction figure set GJBT-471 2. system description this times engineering weak design including: hours a Kok information facilities system integrated wiring system (containing room network, communications part) wired TV system information guide and the released system hours II Kok public security system fire automatically alarm system (containing public broadcast part) security technology prevention system security monitoring system out entrance control system car library management system hours three Kok building equipment monitoring system hours four Kok information application system queued station ICU visitation system operation the system monitoring and training system call intercom system hours, five hours Kok Kok intelligent integrated system of information system (1) cabling systems (including computer room network, communication component) computer network systems and voice communications systems Center of information on medical floor computer room located in the engine room. Voice communication system using a local telecommunications operator providing voice service, configuration-independent integrated services digital program-controlled switchboards. Operators providing communications ... If any compatibility requirements, by way of increased access to the Communications Board within the chassis to meet 1(心房起搏图形 由人工起搏信号和其后的心房波(P’波)组成。如果房室传导完好，则每一个起搏的P’波后跟随着一个QRS波(图2)。当房室传导呈二度阻滞时，则起搏的P波中一部分不能下传心室，造成其后无继随的QRS波，使起搏的P’波之后出现QRS波群规律性缺失。 心房起搏部位和除极顺序的不同，起搏的P’波形态也不同。右心房起搏最常见的部位是右心耳，由于主动固定电极的使用，其它部位如右心房下部、房间隔等部位的起搏也可见到。 ?高位右心房(右心耳):由于右心耳在窦房结附近，因此右心耳起搏的P’波形态与窦性P波近似，特别是肢体导联上，表现在?、?、aVF导联的P’波直立，在aVR导联上倒置。由于右心耳比窦房结更靠前，故在胸前导联上，起搏P’波的的正向部分较窦性P波的振幅更低或倒置(图2)。 图2 AAI起搏心电图 ?右心房其它部位起搏:低位右心房起搏的心电图特点是P?、P?、PaVF倒置，PaVL、PaVR直立。 2(房性融合波 与VVI起搏可产生室性融合波一样，AAI起搏也可产生房性融合波。当植入起搏器患者的自身心律与起搏节律发生干扰时，就产生了房性融合波或(和)假性房性融合波。 房性融合波的形态介于自身的P波和起搏的P’波之间，根据融合的程度不同可有多种形态。当起搏脉冲发放较迟时，由于自身的心房电活动已使电极部位的心房肌除极，使该脉冲正好落入该部位心房肌的有效不应期，因此不能夺获心房而成为无效起搏，在心电图上表现为假性融合(图3)。 图3 AAI起搏的房性融合波 P′(?)的形态介于正常起搏P′波(?)与窦性P波之间。?为假性房性融合波 房性融合波较心室融合波少见，因为心房的起搏激动可直接影响窦房结，使其发生节律重整的机会比VVI起搏器要多得多。由于右心耳与窦房结相邻，加上P波本身的电压较低，故形成的融合波的形态与完全起搏产生的P’波形态相比变化不大，有时在体表心电图上不易分辨。 三(AAI起搏器正常心电图表现 1(起搏功能 AAI起搏器的起搏功能是指起搏器按一定的周期、电压、脉宽发放刺激脉冲使心房除极的功能，因此，在心电图上，AAI起搏器的起搏功能可通过心电图上的起搏信号及相应的P’波加以认定。 for computer software engineering GB/T50314-2000 of electrical installations code for construction and acceptance of GBJ232- 92 intelligent building weak design construction figure set GJBT-471 2. system description this times engineering weak design including: hours a Kok information facilities system integrated wiring system (containing room network, communications part) wired TV system information guide and the released system hours II Kok public security system fire automatically alarm system (containing public broadcast part) security technology prevention system security monitoring system out entrance control system car library management system hours three Kok building equipment monitoring system hours four Kok information application system queued station ICU visitation system operation the system monitoring and training system call intercom system hours, five hours Kok Kok intelligent integrated system of information system (1) cabling systems (including computer room network, communication component) computer network systems and voice communications systems Center of information on medical floor computer room located in the engine room. Voice communication system using a local telecommunications operator providing voice service, configuration-independent integrated services digital program-controlled switchboards. Operators providing communications ... If any compatibility requirements, by way of increased access to the Communications Board within the chassis to meet 当采用双极心房电极导线进行起搏时，起搏信号很小甚至不能分辨，但会出现与基础起搏频率相对应的P’波和QRS波。如果起搏频率较快或房室传导功能较差时，起搏信号及P’波后跟随的QRS波可能有脱漏，多表现为文氏型二度阻滞，有时也可出现二度?型房室阻滞。 2(感知功能 AAI起搏器具有感知功能，感知后的反应为抑制(I)。在心电图上，AAI起搏器的感知功能通过心房起搏间接地反映出来。当自身节律使起搏器从感知信号开始按照基础起搏周期重新发放起搏脉冲时，提示起搏器感知了自身节律并发生节律重整(图4)。当窦性心率超过基础起搏频率时，起搏器的脉冲发放可被完全抑制而表现为“静止状态”。 图4 AAI起搏器的正常感知和起搏功能 基础起搏频率80ppm，感知度1.2mV，起搏电压3.0V。房性期前收缩P′波或窦性P波(*)均被感知而抑制起搏脉冲发放。下一次起搏脉冲以感知的P波为起点按基础起搏器期发放 四(AAI起搏的异常心电图表现 1(感知异常 起搏器的感知异常可分为感知不良(感知低下)和感知过度(超感知)。 ?感知不良:AAI起搏器的感知不良是指对心脏自身正常的P波不能感知，仍按自身的基础起搏周期发放起搏脉冲(图5)。AAI起搏器感知不良的结果是造成不适当的起搏，可以引起竞争性心律，甚至严重的快速房性心律失常。 图5 AAI起搏器感知不良 心房电极导线为双极，起搏电压2.5V，感知灵敏度1.0v，*为起搏信号。A.起搏信号落入窦性P波的前后，当心房脱离不应期时，起搏刺激可以夺获心房(第2、6个刺激信号)。B.数分后，起搏信号落在心动周期不同位置都不能夺房，提示起搏器感知功能低下，间歇性起搏功能障碍 感知不良的原因主要是起搏器感知灵敏度设置不合适和心内电信号的振幅和(或)斜率不够高，因为P波的振幅较QRS波要低得多。心电图判断感知功能不良的最简单方法是当自主心律出现时，起搏节律不能被之干扰，即不能发生起搏器的节律重整。第二个心电图表现是容易出现房性融合波和假性融合波。当起搏频率高于窦性心率时，心电图表现为完全起搏心律，不能表现出感for computer software engineering GB/T50314-2000 of electrical installations code for construction and acceptance of GBJ232- 92 intelligent building weak design construction figure set GJBT-471 2. system description this times engineering weak design including: hours a Kok information facilities system integrated wiring system (containing room network, communications part) wired TV system information guide and the released system hours II Kok public security system fire automatically alarm system (containing public broadcast part) security technology prevention system security monitoring system out entrance control system car library management system hours three Kok building equipment monitoring system hours four Kok information application system queued station ICU visitation system operation the system monitoring and training system call intercom system hours, five hours Kok Kok intelligent integrated system of information system (1) cabling systems (including computer room network, communication component) computer network systems and voice communications systems Center of information on medical floor computer room located in the engine room. Voice communication system using a local telecommunications operator providing voice service, configuration-independent integrated services digital program-controlled switchboards. Operators providing communications ... If any compatibility requirements, by way of increased access to the Communications Board within the chassis to meet 知功能不良，也不会引发竞争性心律，这是与VVI起搏不同之处。 ?感知过度:AAI起搏器对幅度较低或不应该感知的信号发生感知，称为感知过度。由于P波的振幅低，AAI起搏器的感知灵敏度设置得要较VVI高，故较VVI起搏器更容易发生感知过度。常见的感知对象为肌电位和QRS波。图6为AAI起搏器感知QRS波引起起搏间期延长。 图6 AAI起搏器感知过度 感知QRS波群引起起搏间期延长，起搏频率80ppm; A.感知灵敏度1.0mV,出现980和720ms两种起搏间期，在长间期中，QRS波群至其后起搏信号的时间刚好等于短起搏间期(720ms)，提示起搏器感知了心室的QRS波群。B.将感知灵敏度调至2mV后，长起搏间期消失，仪有短起搏间期，证实长间期(980ms)是起搏器对心室Q阳波群超感知所致 2(起搏功能障碍 AAI起搏功能异常可表现为间歇或持续性的心房起搏停止，在心电图上表现为起搏间期长于基础起搏间期或逸搏间期。AAI起搏障碍的原因与VVI起搏器相似，心电图表现也因此不同(图7)。 图7 AAI起搏器电池耗竭 A图:植入时的磁铁试验，磁铁频率为100ppm; B图:植入后7年 10个月记录的磁铁试验，磁铁频率为84ppm，降低了16,，提示起搏器电池耗竭，建议更换起搏器 3(竞争性房性心律失常 竞争性房性心律失常是起搏器参与的心律失常，是由AAI起搏器感知低下或无感知所引起。 发生机制:与VVI起搏相似，AAI起搏也可发生各种类型的竞争性房性心律失常。正常情况下，AAI起搏器的节律与自身的窦性节律之间呈交互抑制，即AAI起搏器发放的起搏脉冲即可抑制窦性节律，又可被窦性节律所抑制。当AAI起搏器发生感知功能不良时，由于起搏器节律不受正常心律的抑制，因此会按自己的节律发放冲动。当起搏频率高于窦性心律时，可使窦性心律完全被抑制;当起搏频率等于或低于窦性心律时，可存在两个并行节律点，并形成多种形式的相互干for computer software engineering GB/T50314-2000 of electrical installations code for construction and acceptance of GBJ232- 92 intelligent building weak design construction figure set GJBT-471 2. system description this times engineering weak design including: hours a Kok information facilities system integrated wiring system (containing room network, communications part) wired TV system information guide and the released system hours II Kok public security system fire automatically alarm system (containing public broadcast part) security technology prevention system security monitoring system out entrance control system car library management system hours three Kok building equipment monitoring system hours four Kok information application system queued station ICU visitation system operation the system monitoring and training system call intercom system hours, five hours Kok Kok intelligent integrated system of information system (1) cabling systems (including computer room network, communication component) computer network systems and voice communications systems Center of information on medical floor computer room located in the engine room. Voice communication system using a local telecommunications operator providing voice service, configuration-independent integrated services digital program-controlled switchboards. Operators providing communications ... If any compatibility requirements, by way of increased access to the Communications Board within the chassis to meet 扰，包括窦性心律被起搏节律的激动抑制，起搏节律的激动可落入自主心律后的不应期内而不能有效地夺获心房，但等率分离的现象较VVI起搏要少见得多。当起搏脉冲(冲动)落入自主心律的心房易损期时，则可能引起严重的竞争性房性心律失常，如房性心动过速(房速)、心房扑动(房扑)、心房颤动(房颤)。 心电图特点:在感知不良的基础上发生的快速性房速、房扑或房颤。如果能记录到起搏脉冲落入心房激动后的易损期引发了房性心律失常更能说明问题。但是，应该指出的是，AAI起搏合并快速房性心律失常不一定是竞争性心律失常，必须同时存在感知不良。与VVI起搏相比，由于AAI起搏节律容易抑制窦性心律，故在心电图上表现为竞争性节律较少。AAI起搏引发的竞争性心律的处理主要是感知不良的处理。 五(AAI起搏心电图的 尽管AAI起搏器与VVI起搏器有相似的工作原理，而且许多厂家也都生产即能作AAI起搏器用又能作VVI起搏器用的SSI型单腔起搏器，但两者心电图的表现有所不同。在分析AAI心电图时，要注意以下特点。 1(起搏心电图记录的要求 由于P波振幅较低，故要求记录的起搏心电图要有清晰的P波，这样才能准确地判定起搏器的起搏与感知功能。必要时，应记录同步12导联心电图或Holter及心内心电图(可通过程控仪显示和打印出来)。 2(了解AAI起搏器的起搏和感知使用的是单极还是双极 由于双极电极导线使用比例的增加，分析心电图时，一定要了解AAI起搏器的起搏和感知使用的是单极还是双极。单极导线的起搏信号大，容易识别，而双极起搏信号小，不容易识别。此外，单极感知时，起搏器容易发生超感知。 3(仔细分辨心电图上在起搏信号有无P波及相应的QRS波 如果P波不能清楚地显示，但每一个起搏信号后跟随有QRS波，也能说明AAI起搏器的起搏功能正常，而心房激动产生的P’波在心电图上不能清楚地显示。 for computer software engineering GB/T50314-2000 of electrical installations code for construction and acceptance of GBJ232- 92 intelligent building weak design construction figure set GJBT-471 2. system description this times engineering weak design including: hours a Kok information facilities system integrated wiring system (containing room network, communications part) wired TV system information guide and the released system hours II Kok public security system fire automatically alarm system (containing public broadcast part) security technology prevention system security monitoring system out entrance control system car library management system hours three Kok building equipment monitoring system hours four Kok information application system queued station ICU visitation system operation the system monitoring and training system call intercom system hours, five hours Kok Kok intelligent integrated system of information system (1) cabling systems (including computer room network, communication component) computer network systems and voice communications systems Center of information on medical floor computer room located in the engine room. Voice communication system using a local telecommunications operator providing voice service, configuration-independent integrated services digital program-controlled switchboards. Operators providing communications ... If any compatibility requirements, by way of increased access to the Communications Board within the chassis to meet