This series we're focusing on the diagnosis and management of bradyarrhythmias.
Tish week we'll focus primarily on one of the treatments: cardiac pacing.
1.What clinical features establish the need for cardiac pacing?
2.What are the advantages of cardiac pacing over medications?
3.What are the disadvantages of cardiac pacing?
4.What methods of temporary cardiac pacing are available?
5.Is transcutaneous pacing as effective as the invasive pacing routes previously described?
1 需要心脏起搏的临床特征有哪些？
2 心脏起博与应用药物比较，有点有哪些？
3 心脏起搏的缺点有哪些？
4 可利用的临时心脏起博的方法有哪些？
5 经皮起搏是否如以前描述的那样，和有创起搏途径一样有效？
参考答案，请战友指正：
1 需要心脏起搏的临床特征有哪些？
非可逆性原因导致的有症状的心动过缓是植入起搏器的指征。围术期可能需要临时起搏器，尤其是心外科手术，需生理稳态和组织痊愈后撤掉临时起搏器。此外，对于术前存在与病窦相关的心动过缓时应考虑预防性使用临时起搏器。在植入临时起搏器前应考虑停掉可能导致心动过缓的药物，这些药物通常用于控制快速型心律失常。
2 心脏起博与应用药物比较，优点有哪些？
心脏起搏器有很多的优点，包括：
•起效迅速
•易于滴定有效“剂量”，如模式、速率、电流等
•没有不希望有的副作用，如节律障碍加重
•可改善冠脉循环血流动力学
3 心脏起搏的缺点有哪些？
应用心脏起搏器潜在的缺点，包括如下：
•存在败血症、出血、或直接的心肌损伤的风险
•快速型心律失常的刺激
•某些患者起搏失败
4 可利用的临时心脏起博的方法有哪些？
临时起搏途径包括心外膜、经静脉（心内膜）、经皮和经食道等途径。在心外手术中，通常应用心外膜、心内膜和经食道途径起搏增加心率、抑制心动过缓依赖性心动过速、超速起搏逸搏节律、抑制房性或室性期外收缩和终止折返性室上性心动过速或心房扑动。心房或双腔起搏（相对于室性起搏）可对心房的运输功能具有保护作用。飘浮导管肺动脉起搏导管可在无x线透视检查下进行临时起搏，并认为是有效的起搏途径。
经食道途径起搏逐渐增加，部分是由于其能够提供生理性（房性）和室性起搏。近期由于成功处置心动过缓、快速型心律失常、折返性室上性心动过速或房扑，经食道起搏逐渐引起大家兴趣。
5 经皮起搏是否如以前描述的那样，和有创起搏途径一样有效？
如预料中一样胸壁和心脏组织间存在各种电阻，经皮起搏效果不如其他有创性起搏。经皮起搏受限的原因包括：
•非生理性（室性）起搏
•某些患者起搏无效
•途径受限（消毒区域、患者体位）
•有意识患者有不舒服感
英文参考答案
1 What clinical features establish the need for cardiac pacing?
Symptomatic bradycardia not related to reversible causes is the cardinal feature requiring the placement of a pacemaker. Perioperatively, a temporary pacemaker may be necessary, particularly after cardiac surgery, until physiologic homeostasis and tissue recovery occurs. In addition, consideration of a prophylactic temporary pacemaker prior to surgery should be given in patients with preexisting bradydysrhythmias associated with sinus node dysfunction. Consideration should also be given to discontinuing agents which are potentially causing the bradycardia prior to pacemaker placement, however, often these medications are necessary to control tachyarrhythmias.
2 What are the advantages of cardiac pacing over medications?
A number of advantages exist with cardiac pacing including (1):
•prompt effect
•easier to titrate effective "dose" i.e. mode, rate, current
•no undesired side effects or dysrhythmia aggravation
•may improve coronary hemodynamics (2)
3 What are the disadvantages of cardiac pacing?
There are potential disadvantages of the use of cardiac pacing, including (1):
•risk of sepsis, hemorrhage, or direct myocardial injury
•stimulation of tachydysrhythmias
•inability to pace some patients
4 What methods of temporary cardiac pacing are available?
Epicardial, transvenous (endocardial), transcutaneous, and transesophageal routes are used for temporary pacing. During cardiac surgery, epicardial, endocardial, and transesophageal routes are utilized to increase heart rate, suppress bradycardia-dependent tachycardia, overdrive escape rhythms, suppress atrial or ventricular extrasystoles, and to terminate reentrant SVT or atrial flutter (3). The preservation of atrial transport function is supported through the use of atrial or dual chamber pacing (versus ventricular pacing). Balloon flotation pulmonary pacing catheters can be placed for temporary use without fluoroscopy, and have been noted to be effective (4).
Transesophageal pacing is growing in popularity, in part due to its ability to provide physiologic (atrial) and ventricular pacing (5). Recent success in the management of bradycardia, tachydysrhythmias, and reentrant SVT or atrial flutter has added to the interest in this modality.
5 Is transcutaneous pacing as effective as the invasive pacing routes previously described?
As would be expected by the various resistances of the tissues between the chest wall and the heart, transcutaneous pacing has not been as successful as more invasive routes. Reasons for this limitation include (1):
•provision of nonphysiologic (ventricular) pacing,
•inability to capture in some patients
•restricted access (sterile field, patient position)
•uncomfortable in conscious patients
References:
1.Atlee JL. Perioperative cardiac dysrhythmias: diagnosis and management. Anesthesiology 1997 Jun;86:1397-424.
2.Kyriakides ZS, Kolettis TM, Kremastinos DTh. Cardiac pacing and coronary hemodynamics. Prog Cardiovasc Dis 1999;41:471-80.
3.Gammage MD. Temporary cardiac pacing. Heart 2000;83:715-20.
4.Plewan A, Valina C, Herrmann R, Alt E. Initial experience with a new balloon-guided single lead catheter for internal cardioversion of atrial fibrillation and dual chamber pacing. Pacing Clin Electrophysiol 1999;22(1 Pt 2):228-32.
5.Kitahata H, Tanaka K, Kimura H, Kawahito S, O***a S. The feasibility of gastrothoracic ventricular pacing during transesophageal echocardiography. Anesth Analg 1999 Jul;89(1):21-5.
