References

Anatomy of the heart. In Hurst JW, ed. The Heart. 6th ed. New York McGraw-Hill, 1986 16-37. 2. Phibbs B, Friedman HS, Graboys TB, et al. Indications for pacing in the treatment of bradyarrhythmias report of an independent study group. JAMA 1984 252 1307-1311. 3. Gregorators G, Abrams J, Epstein AE. ACC AHA NASPE 2002 Guideline update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices Summary Article A Report of the American Heart College of Cardiology...

AV Delay Hysteresis AR Interval PR Interval

Schematic diagram of one manufacturer's differential AVI, designated AV delay hysteresis. (Modified from Chorus II Model 6234, 6244 Dual Chamber Pulse Generator Physician's Manual. Minnetonka, Minnesota ELA Medical, 1994.) One DDD pacemaker automatically calculates the AVI differential between paced and sensed atrial events.23 When an atrial paced event occurs, the AR interval is measured. When an atrial sensed event follows an atrial paced event, a new PR interval is measured. The...

Impedance

Impedance is the sum of all factors that oppose the flow of current in an electric circuit. Impedance is not necessarily the same as resistance. The relationship between voltage (V), current (I), and resistance (R) in an electrical circuit is estimated by Ohm's law, V IR. For circuits that follow Ohm's law, impedance and resistance are equal. If voltage is held constant, the current flow is inversely related to the resistance of the circuit (I V7R). The leading-edge voltage of a...

Isolated Implantable Cardioverter Defibrillator Discharge

Icd Egm Svt

Approximately 60 to 80 of ICD patients will receive a shock therapy within 5 years of implant.20'21 Although ICD shocks are an expected occurrence, each event may frighten the patient, and these warrant careful evaluation by the physician. A flow diagram for the evaluation of ICD shocks is shown in Figure 10.8. Before they are discharged from the hospital after ICD implantation, patients should be educated about the procedures to follow after an ICD shock. Our practice is to have the patient...

Factors Limiting Successful Transvenous Left Ventricular Lead Placement

Epicardial Pacing Wires

Complex and unpredictable anatomic and technical considerations may preclude successful delivery of the LV lead to an optimal pacing site. Inability to Cannulate the Coronary Sinus It is difficult to estimate the true percentage of cases in which the coronary sinus cannot be cannulated because this is clearly influenced by operator experience. It is probably in the range of 1 to 5 .When the coronary sinus cannot be located by the superior approach, an adaptation of the inferior approach...

Pulse Generators And Lead Systems

Pacing Leads Line Drawing

Early ICD pulse generators were large and bulky. The size 115 to 145 cm3 and weight 195 to 235 g of these devices mandated abdominal implantation, typically in the left upper quadrant either subcutaneously or most often under the rectus muscle. The surgical procedure for abdominal ICD implantation is more extensive than for endocardial pacemakers, in part because it requires tunneling leads from the chest. The abdominal location of the pulse generator and the surgical procedure required were...

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Transcutaneous Pacing

Transcutaneous pacing electrode positions. Upper left Anterior cathodal patch placement over cardiac apex. Upper right Alternate anterior cathodal patch position over position of electrocardiographic chest lead V3. Lower left Posterior anodal patch centered between lower aspect of the left scapula and the spine. Lower right Placement of anterior anodal patch on the right chest. Note that cathodal negative electrode must be positioned anteriorly. stimuli, but capture must be...

Cardiac Resynchronization Therapy

Recognition of the contribution of disordered electrical timing to reduced ventricular performance suggested the possibility that pacing techniques could favorably modulate contractile dyssynchrony and delayed AV timing. The fundamental premise of this therapeutic strategy is that left ventricular preexcita-tion may correct inter- and intraventricular conduction delays and permit optimization of left-sided AV delay, thereby improving ventricular pumping function. The first report of the...

Sensing And Pacing Thresholds

Pacemaker Mediated Tachycardia Icd

For manual sensing threshold determination, the device should first be re-programmed below the intrinsic rate to assess sensing. In single-chamber devices, ventricular sensing thresholds may be determined by then decreasing sensitivity i.e., increasing the millivolt values in the VVI mode to determine at what value Figure 11.10. Stored atrial top and ventricular bottom electrograms from a pacemaker with automated electrogram capture triggered by a high ventricular rate. The patient experienced...

Lead Design

Two Lead Pacemake

Permanent pacing leads have five major components 1 the electrode s 2 the conductor s 3 insulation 4 the connector pin and 5 the fixation mechanism. Each of these components has critical design considerations, as well as failure modes. In this section, the factors that are important for design of leads are reviewed. As discussed previously in this chapter, the stimulation threshold is a function of the current density generated at the electrode.26,34-36 In general, the smaller the radius of the...

Mechanical Cardiac Pacing

Percussion Pacing

Mechanical cardiac pacing techniques stimulate myocardial tissue by direct or transmitted physical forces. Clinically, these techniques include percussion pacing chest thumps administered by a medical attendant and cough-induced cardiac resuscitation performed by patients themselves. Although they are lacking in technical sophistication, these techniques persist as useful clinical maneuvers by virtue of their sheer simplicity and immediacy of application. Percussion pacing for bradyarrhythmias...

Info

Pacemakers with proven 5-yr longevity gt 90 and nonabrupt decline in output over gt 3mo. Pacemakers with inability to demonstrate 5-yr longevity gt 90 and nonabrupt decline in output over gt 3 mo applies to most pacemakers . Every 6 mo thereafter until approaching elective replacement indicators. Twice in first 6 mo. after implant, then Once every 12 mo. Dual chamber 2nd to 48th mo Every 12wk. 49th to 72nd mo Every 8wk. 2nd to 30th mo Every 12wk. 31st to 48th mo Every 8 wk. receives a...

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Temporary Pacemaker Sensitivity

The instability of atrial leads and unpredictable effects of autonomic tone and ischemia on AV nodal conduction frequently preclude its use. Although patients without underlying cardiac disease usually demonstrate similar hemodynamic responses to atrial and ventricular pacing, the maintenance of AV synchrony through atrial or dual-chamber pacing is beneficial in patients with left ventricular systolic and or diastolic dysfunction.31,32 In these patients, AV sequential pacing may...

Sinus Node Dysfunction

Bradycardia Patient

Sinus node dysfunction, or sick sinus syndrome and its variants, is a heterogeneous clinical syndrome of diverse etiologies.11 This disorder includes sinus bradycardia, sinus arrest, sinoatrial block, and various supraventricular tachycardias atrial or junctional alternating with periods of bradycardia or asystole. Sinus node dysfunction is quite common and its incidence increases with advancing age. In patients with sinus node dysfunction, the correlation of symptoms with the bradyarrhythmia...

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Pacemaker Dddr Mode

VP VP VP VP VP VP VP VP VP VP VP VP VP VP Figure 6.32. Resting ECG tracing demonstrating AV sequential pacing at lower rate 55 ppm followed by paroxysmal atrial flutter with ventricular tracking at MTR 110 ppm . Diagram shows atrial paced events AP , atrial sensed events AS , and ventricular paced events VP , with the PVARP noted by the rectangle. Short, unlabeled ticks represent atrial activity that occurs in the PVARP and is not sensed. Diagram is based on Marker Channel, Medtronic, Inc.,...

Indications

The indications for ICD implantation remained unchanged for many years. Initially, the devices were only implanted in patients who had survived an aborted cardiac arrest or an episode of sustained ventricular tachycardia that was refractory to antiarrhythmic drug therapy. The use of ICDs for the secondary prevention of sudden cardiac death was the standard for more than a decade. However, several landmark studies established the role of ICD therapy for primary prevention of sudden death in...

Pharmacologic And Metabolic Effects On Stimulation Threshold

Stimulation Threshold Pacemaker

The stimulation threshold may demonstrate considerable variability over the normal 24-hour period, generally increasing during sleep and falling during the waking hours.54'55 The changes in threshold parallel fluctuations in autonomic tone and circulating catecholamines, and consequently there is a decreased threshold during exercise. The stimulation threshold is inversely related to the level of circulating corticosteroids. The stimulation threshold may increase following eating, during...

Interventricular Delay

Mitral Regurgitation Wigger

Optimal inter- and intraventricular coupling is more important than AV coupling for maximum ventricular pumping function. Normal ventricular electrical activation is rapid and homogeneous with minimal temporal dispersion throughout the wall. This elicits a synchronous mechanical activation and ventricular contraction. Exploration of the link between the sequence of cardiac electrical activation and mechanical function is one of the most exciting contemporary areas of research in heart failure...

Surgical Approach to Left Ventricular Lead Placement

Epicardial Lead

The first clinical trial of CRT used a hybrid epicardial LV, endocardial RV pacing lead configuration for multisite ventricular stimulation simply because the technique for transvenous epicardial LV pacing had not been developed.36 There are several current approaches to surgical placement of LV pacing leads. Many surgeons still use a full left lateral thoracotomy, which permits full visualization of the LV free wall, but results in significant postoperative pain and an extended recovery...

Comparison of Atrial Based and Ventricular Based Systems

Atrial Based Timing

When the heart rate is considered, usually the ventricular rate is paramount, because it, not the atrial rate, causes the effective hemodynamic pulse. During periods of 2 1 AV block at the lower rate, a ventricular-based timing system Figure 6.27. Ventricular-based versus atrial-based timing. The lower portion demonstrates atrial escape timing after an atrial A pace in atrial-based timing. With this timing, the AVI after atrial pacing PAV always times out, regardless of ventricular inhibition....

Pacing for Children and Adolescents Including Congenital Heart Block

The general indications for pacing in children and adolescents are similar to those for adults with several additional considerations. The diagnosis of significant bradycardia in children depends on age, presence and type of congenital heart disease, and cardiac physiology. Following surgery for congenital heart disease, patients may have postoperative AV block that if untreated by pacing will worsen their prognosis.33 Congenital heart disease patients may also have tachycardia-bradycardia...

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A 3-lead standard leads V,, II, and V5 rhythm strip in a 58-year-old man with an acute inferior wall myocardial infarction and complete AV block the arrows in lead V, identify the P waves with an escape rate of 45 ppm. Despite the slow rate, the patient did not exhibit signs or symptoms of hemodynamic compromise, so no therapy was required. Normal conduction resumed approximately 24 hours later. Figure 1.19. A 3-lead standard leads V,, II, and V5 rhythm strip in a 58-year-old man...

1

Endless Loop Tachycardia

Crosstalk that occurs in the presence of a special crosstalk detection window triggers a ventricular output pulse rather than inhibiting it. This usually occurs at a shorter-than-programmed AV interval. Intermittent AV-interval shortening is seen in the two tracings. This reflects episodes of crosstalk triggering a ventricular output pulse. In the top tracing, for example, the second and ninth beats show AV-interval shortening. Figure 7.21. Crosstalk that occurs in the presence of...

Bipolar Versus Unipolar Stimulation

Bipolar Unipolar Pacemaker

The term unipolar pacing is technically a misnomer, as both bipolar and unipolar configurations require an anode and a cathode to complete the electrical Figure 2.10. The relationship between the voltage waveform of a constant-voltage pulse and the development of polarization effect at the electrode-myocardial interface is illustrated. Note that the polarization effect rises during application of the stimulating pulse and decays exponentially. The trailing edge of the output pulse is less than...

Ventricular Undersensing Pvc Av Delay

Xray Pacemaker Header Set Screw Loose

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...

Dualchamber Pacing System Malfunction

Atrial Oversensing

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...

Endlessloop Tachycardia

Pacemaker Mediated Tachycardia Breaking

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...

Revision of the Implanted Pacemaker System and Pulse Generator Change

Epicardial Biventricular Pacing

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...

The Cephalic Vein Approach

Pacemaker Cephalic 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...