Treatment of Tachycardias with Temporary Pacing
Temporary cardiac pacing has been used for the termination and or prevention of a variety of arrhythmias. Pacing-termination of ventricular tachycardia is discussed in detail in Chapter 8 on the implantable cardioverter defibrillator and will not be dealt with here. Type I atrial flutter can be successfully pace-terminated approximately 65 of the time in an unselected population and in over 90 of patients in whom atrial flutter develops after surgery.58 Due to the development of radiofrequency...
Thoracotomy for Lead Extraction
There has been a natural reticence even among surgeons to remove leads at thoracotomy. While there is no randomized data comparing the two techniques, the Accufix experience suggests no clinically significant difference in the incidence of death or major complications. This is not surprising considering the advanced age and co-morbidity of many pacemaker patients. Surgery however may be the only alternative in situations in which percutaneous techniques have failed and there is an absolute...
Ventricular Asynchronous Pacing Atrial Asynchronous Pacing and AV Sequential
Ventricular asynchronous VOO pacing is the simplest of all pacing modes because there is neither sensing nor mode of response.The timing cycle is shown in Figure 6.1. Irrespective of any other events, the ventricular pacing artifacts occur at the programmed rate. The timing cycle cannot be reset by any intrinsic event. In the absence of sensing, there is no defined refractory period. Atrial asynchronous AOO pacing behaves exactly like VOO, but the pacing artifacts occur in the atrial chamber....
Transcutaneous Cardiac Pacing
Transcutaneous cardiac pacing has emerged as the preeminent initial mode of cardiac pacing for bradyasystolic arrest situations and prophylactic pacing applications. The technique can be quickly and safely initiated by minimally trained personnel. A variable incidence of cardiac capture and poor patient tolerance represent the disadvantages to transcutaneous pacing. Transcutaneous cardiac pacing produces depolarization of myocardial tissue by pulsed electrical current conducted through the...
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Figure 7.1. Pacing stimuli present with intermittent failure to capture. The large unipolar stimuli are readily identified. The gentle downslope following the ineffective pacing stimulus is an RC decay curve. The pause is due to appropriate sensing of a native QRS, which is virtually isoelectric in this lead. RC resistance capacitance. Figure 7.1. Pacing stimuli present with intermittent failure to capture. The large unipolar stimuli are readily identified. The gentle downslope following the...
Ventricular Inhibited Pacing
By definition, ventricular demand inhibited VVI pacing incorporates sensing on the ventricular channel, and pacemaker output is inhibited by a sensed ventricular event Fig. 6.3 .VVI pacemakers are refractory after a paced or sensed ventricular event, a period known as the ventricular refractory period VRP . Any ventricular event occurring within the VRP is not sensed and does not reset the ventricular timer Fig. 6.4 . Figure 6.4. If, in the VVI mode, a ventricular event occurs during the VRP...
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Note Recommendations are based on extensive animal studies and mathematical modeling, appropriate testing in each patient is mandatory. See Singer I, Lang D. The defibrillation threshold. In Kroll MW, Lehmann MH, eds. Implantable Cardioverter Defibrillator Therapy. The Engineering Clinical Interface. Norwell Kluwer Academic, 1996 89-129. Note Recommendations are based on extensive animal studies and mathematical modeling, appropriate testing in each patient is mandatory. See Singer I, Lang D....
Rate Sensing
Sensing of ventricular tachyarrhythmias is a critically important function of an ICD system. The ability to sense small amplitude signals rapidly during ventricular fibrillation, while not oversensing T waves or noise in the absence of tachyarrhythmias, is mandatory for proper ICD function. This goal was difficult to achieve with fixed gain sensing,33 as is used in pacemaker systems. An example of undersensing of ventricular fibrillation by such a fixed gain sensing circuit is shown in Figure...
Complications of Biventricular Pacing
Implantation of a coronary venous lead is the major procedural difference between biventricular and simple dual-chamber pacemaking. It is subject to all the complications associated with dual-chamber systems plus those unique to left ventricular pacing.71 The left ventricular lead must be placed in a lateral wall vein that has been a challenge especially in the early experience with this modality. Inability to achieve a left ventricular lead placement by a transvenous approach has been reported...
Summary 1
As mentioned at the beginning of this chapter, it is important to maintain appropriate records containing all the baseline data and results of the periodic detailed evaluations of the pacing system. These records provide the substrate on which to assess a new observation or information. For biventricular systems, it is helpful to have 12-lead ECGs showing the native depolarization, RV pacing, LV pacing, and biventricular pacing. Depending on the capabilities of the implanted system, it may need...
Dualchamber Pacing System Malfunction
There are five major classes of dual-chamber pacing system malfunction. The first class includes all the abnormalities previously discussed as occurring with single-chamber pacing systems. The abnormalities in this case occur on one or both of the two channels of the dual-chamber system and, in recent years, this has been extended to either lead in a multisite atrial or ventricular system. Although this may sometimes be obvious, there are situations in which the problem will not be readily...
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ISBN-13 978-1-4051-0447-0 ISBN-10 1-4051-0447-3 Library of Congress Cataloging-in-Publication Data Cardiac pacing and ICDs edited by Kenneth A. Ellenbogen, Mark A.Wood. 4th ed. p. cm. Includes bibliographical references and index. ISBN-13 978-1-4051-0447-0 pbk. ISBN-10 1-4051-0447-3 pbk. 1. Cardiac pacing. 2. Implantable cardioverter-defibrillators. DNLM 1. Cardiac Pacing,Artificial. Implantable. 3. Pacemaker,Artificial. WG 168 C26333 2005 I. Ellenbogen,Kenneth A. II. Wood RC684.P3C29 2005...
Preoperative Pacing
One of the questions most frequently asked of a consulting cardiologist by both surgeons and anesthesiologists is whether it is necessary to insert a temporary pacing catheter in patients with bifascicular block undergoing general anesthesia. The results of several studies have shown that the incidence of intraoperative and perioperative complete heart block is quite low. There does not appear to be any benefit from preoperative prophylactic pacemaker insertion. Even in patients with...
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High-impedance leads typically exceed these values check with manufacturer for acceptable values. High-impedance leads typically exceed these values check with manufacturer for acceptable values. lead, which facilitates its entry into the appendage. When using active-fixation leads, there are advantages and disadvantages to preformed devices. The non-J lead may be easier to place in areas other than the appendage however, dis-lodgment may result in the lead's falling into the right ventricle...
Endlessloop Tachycardia
Endless-loop tachycardia ELT is not a portion of the timing cycle, but understanding the timing cycle of dual-chamber pacing is crucial to understanding ELT, and vice versa. ELT has also been referred to as pacemaker-mediated tachycardia PMT , pacemaker-mediated reentry tachycardia, and pacemaker circus movement tachycardia.9 ELT has been defined as a reentry arrhythmia in which the dual-chamber pacemaker acts as the anterograde limb of the tachycardia and the natural pathway acts as the...
Lead Implantation
A variety of leads are available for endocardial placement. They differ in composition, shape, electrode configuration, and method of fixation. Special leads that contain steroid-eluting collars or biosensors have been developed. Passive fixation leads have tines or fins that anchor them in the trabeculated right ven- Easier removal of chronic implant More difficult chronic removal Higher early dislodgment rate tricle or atrial appendage active-fixation leads employ a helix that provides a...
Rateadaptive Sensors
Widespread appreciation of the importance of rate modulation in the augmentation of cardiac output with exercise has led to the development of a variety of physiologic sensors. Although the normal sinus node may be an ideal rate-adaptive sensor for many patients who require pacemakers, the frequent occurrence of sinus node dysfunction and atrial fibrillation in clinical practice limits the applicability of atrial sensing for reliably modulating pacing rate in many individuals. Thus, artificial...
Lead Placement
Arrhythmia The introduction, manipulation, and positioning of the pacemaker leads in the heart may give rise to a number of complications. Arrhythmia may be a manifestation of the patient's underlying disease, or it may be procedurally 1. Increase central venous pressure. Elevate legs Trendelenburg position . Have patient perform Valsalva maneuver when sheath is open. 2. Awaken patient and caution against deep inspiration. 3. Use smallest sheath compatible with task. 4. Pinch or occlude neck of...
Bifurcated Bipolar Connector
11 ' -RING PROXIMAL ELECTRODE RING ELECTRODE TIP ELECTRODE Two Designs of Bipolar Leads Figure 2.28. A white band marks the conductor leading to the distal electrode on a standard bifurcated bipolar lead connector with two connector pins. On a low-profile Medtronic type bipolar connector that has a single pin, the distal electrode connects to the pin. RING ELECTRODE TIP ELECTRODE Two Designs of Bipolar Leads Figure 2.28. A white band marks the conductor leading to the distal electrode on a...
Stimulation Threshold
Cardiac pacing involves the delivery of a polarizing electrical impulse from an electrode in contact with the myocardium with the generation of an electrical field of sufficient intensity to induce a propagating wave of cardiac action potentials.19 The stimulating pulse may be either anodal or cathodal in polarity, although with somewhat different stimulation characteristics. In addition, the stimulation characteristics are related to the source of the stimulating pulse, with constant-voltage...
Revision of the Implanted Pacemaker System and Pulse Generator Change
Revision of an implanted pacing system may involve replacement of the pulse generator, the pacing leads, or both Fig. 5.13 . The uncomplicated generator change is usually a simple procedure however, the preparation is in many ways Figure 5.13. PA chest radiograph of woman with congenital heart disease referred for biventricular pacing system upgrade. She has a dual chamber pacing system comprising two separate sets of unipolar transvenous leads arrowheads to both the atrium and ventricle. These...
Accufix Wire Fragment Retrieval
As noted previously, fracture of the J retention wire in the Accufix family of atrial leads may produce protrusion of a wire fragment Fig. 5.23 , which has the potential to lacerate the heart and other mediastinal structures. It may be possible to selectively retrieve the protruding fragment if it is the distal portion of the proximal part of the wire. This is achieved using an Amplatz gooseneck snare passed through an 8F coronary guide catheter of a shape matching the specifics of the case....
DualChamber Pacing and Sensing with Inhibition and Tracking
Although the DDD timing cycle involves more intervals, standard dual-chamber pacing and sensing with inhibition and tracking DDD are reasonably easy to comprehend on the basis of the timing cycles already discussed.7-12 The basic Figure 6.13. The timing cycle of VDD consists of an LRL, an AVI, a VRP, a PVARP, and a URL. A sensed P wave initiates the AVI during the AVI, the atrial sensing channel is refractory . At the end of the AVI, a ventricular pacing artifact is delivered if no intrinsic...
Chronic Bifascicular Or Trifascicular Block
Patients with chronic bifascicular block right bundle branch block and left anterior hemiblock, right bundle branch block and left posterior hemiblock, or complete left bundle branch block and patients with trifascicular block any of the above and first-degree AV block are at an increased risk of progression to complete AV block. In the 1980s, the results of several prospective studies of the role of His bundle recordings in asymptomatic patients with chronic bifascicular block were...
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diastolic potentials, skeletal muscle signals, and pacing stimuli. In this section, the basic determinants of electrogram sensing will be discussed. Intracardiac electrical signals are produced by the movement of electrical current through myocardium. An electrode that overlies a region of resting myocardium records from the outside of cardiac myocytes, which are positively charged with respect to the inside of the cell. Despite this, an electrode in one region of resting myocardium will record...
The Cephalic Vein Approach
The cephalic vein resides in the sulcus between the deltoid and pectoral muscles. This area is readily identified by palpation and is occupied by loose connective tissue and fat, which is easily separated to reveal the underlying vein that sometimes lies fairly deep in this groove. The consistent course of this vessel, its reasonable size, and the direct path it takes to the central venous system recommend it for lead placement. On occasion, however, this vessel is small, consists of a plexus...
The Axillary Vein Approach
There is evidence that the traditional percutaneous subclavian approach results in access to the medial aspect of the vein, which may result in entrapment of the lead between the subclavius muscle and the costoclavicular ligament.18,19 Forces exerted on leads in this position may predispose them to insulation failure. This may be most problematic for some polyurethane leads especially those made with Pellethane 80A which appear to be particularly susceptible to failure when placed via the...
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Figure 5.6. Anatomy of the subclavian venous system. A Anatomy of the subclavian venous system and skeletal landmarks relevant to percutaneous access. The subclavius muscle and costoclavicular ligament complex are shown between the clavicle and first rib. Accessing the subclavian vein medially requires the lead to pass through these structures. This may be associated with a higher risk of lead fracture due to compressive forces on the lead. By accessing the cephalic vein or axillary vein...
The Pacemaker Pocket
The pacemaker is usually placed in a subcutaneous position near the site of venous entry. Generators have continued to decrease in size and can be placed quite easily in most patients, including those having a paucity of subcutaneous tissue. Most often, the device is placed in the infraclavicular area through the incision used to obtain venous access. Local anesthesia is applied to the subcutaneous tissue, which is then dissected down to the prepectoral fascia. Placing the pocket too...
Indications For Temporary Cardiac Pacing
The following section reviews the clinical settings in which temporary cardiac pacing is indicated. Chapter 4 presents a review of the techniques and complications of temporary cardiac pacing. A summary of the general indications for temporary pacing is given in Box 1.4. In the setting of an acute myocardial infarction, several different types of conduction disturbances may become manifest. They include abnormalities of sinus Table 1.3. Clinical Trials of AV Sequential versus VVI Pacing for...
References Nta
1. Falk RH, Ngai STA. External cardiac pacing influence of electrode placement on pacing threshold. Crit Care Med 1986 14 931-932. 2. Sado DM, Deakin CD, Petley GW, Clewlow F. Comparison of the effects for removal of chest hair with doing nothing before external defibrillation on transthoracic impedance. Am J Cardiol 2004 93 98-100. 3. Madsen JK, Pedersen F, Grande P, Meiborn J. Normal myocardial enzymes and normal echocardiographic findings during noninvasive transcutaneous pacing. Pacing Clin...
Other Temporary Pacing
Temporary pacing is indicated in patients with new AV or BBB in the setting of acute bacterial endocarditis. The development of a new conduction system abnormality generally suggests that there is a perivalvular ring abscess that has extended to involve the conduction system near the AV node and or the His bundle. The endocarditis generally involves the non-coronary cusp of the aortic valve. In one study, high-grade or complete heart block developed in 22 of patients with aortic valve...