Atrial fibrillation pacemaker

Common supraventricular tachycardias requiring drug treatment are atrial fibrillation (AF) or atrial flutter, paroxysmal supraventricular tachycardia (PSVT), and automatic atrial tachycardias. Other common supraventricular arrhythmias that usually do not require drug therapy are not discussed in this chapter (e.g., premature atrial complexes, wandering atrial pacemaker, sinus arrhythmia, sinus tachycardia). 

Contraindications Atrial fibrillation or flutter, second-or third-degree AVblock or sick sinus syndrome (with functioning pacemaker), ventricular tachycardia... 

Amiodarone and carvedilol have been used in combination in 109 patients with severe heart failure and left ventricular ejection fractions of 0.25 (16). They were given amiodarone 1000 mg/week plus carvedilol titrated to a target dose of 50 mg/day. A dual-chamber pacemaker was inserted and programmed in back-up mode at a basal rate of 40. Significantly more patients were in sinus rhythm after 1 year, and in 47 patients who were studied for at least 1 year the resting heart rate fell from 90 to 59. Ventricular extra beats were suppressed from 1 to 0.1/day and the number of bouts of tachycardia over 167 per minute was reduced from 1.2 to 0.3 episodes per patient per 3 months. The left ventricular ejection fraction increased from 0.26 to 0.39 and New York Heart Association Classification improved from 3.2 to 1.8. The probability of sudden death was significantly reduced by amiodarone plus carvedilol compared with 154 patients treated with amiodarone alone and even more so compared with 283 patients who received no treatment at all. However, the study was not randomized, and this vitiates the results. The main adverse effect was s)mptomatic bradycardia, which occurred in seven patients two of those developed atrioventricular block and four had sinoatrial block and/or sinus bradycardia one patient developed slow atrial fibrillation. 

Sweeney MO, Hellkamp AS, Ellenbogen KA, et al. Adverse effect of ventricular pacing on heart failure and atrial fibrillation among patients with normal baseline QRSd in a clinical trial of pacemaker therapy for sinus node dysfunction. Circulation 2003 23 2932-7. 

Steven D, Rostock T, Lutomsky B, et al. What is the real atrial fibrillation burden after catheter ablation of atrial fibrillation A prospective rhythm analysis in pacemaker patients with continuous atrial monitoring. Eur Heart J 2008 29 1037-42. 

Pacing in the right ventricle can have deleterious effects in terms of the development of heart failure and atrial fibrillation. This has led to the development of algorithms that minimize ventricular pacing in patients whose bradycardia is because of the dysfunction of their sinus node (which functions as the heart s natural pacemaker), rather than the dysfunction of their heart s intrinsic conduction system. Excellent discussions of this issue and other sophisticated pacemaker algorithms can be found in Al-Ahmad et al. (2010). 

If the procedure is to proceed in a smooth and expeditious fashion, careful preoperative planning is essential. The first such decision is whether the patient requires a single-chamber or dual-chamber pacemaker. As a rule, if the patient has intact atrial function, every effort is made to preserve atrial and ventricular relationships. Single-chamber ventricular pacing is usually reserved for the patient with chronic atrial fibrillation or atrial paralysis. A device is selected with acceptable size, longevity, and progranunability. If the heart is chronotropically incompetent, a device that offers some form of rate adaptation... 

Stambler BS, Ellenbogen KA, Zhang X, et al. Right ventricular outflow versus apical pacing in pacemaker patients with congestive heart failure and atrial fibrillation. J Cardiovas Electrophysiol 2003 14 1180. 

The only effective treatment for symptomatic sinus node dysfunction is cardiac pacing. Despite two decades of clinical investigation, the optimal pacing mode, pacing system and site of ventricular stimulation for bradycardia support for sinus node dysfunction remain uncertain. Selection of pacing mode may be important for the clinical outcomes of quality of life, pacemaker syndrome, atrial fibrillation, heart failure, thromboembolism, and mortality in patients with sinus node dysfunction. 

No differences in death or stroke. Atrial fibrillation, heart failure and pacemaker syndrome slightly less and quality of life slightly better with DDDR vs. WIR... 

In summary, the lowest risk of atrial fibrillation is achieved with maintenance of both AV and interventricnlar synchrony where possible. However, the benefits appear to be relatively small and only become evident years after pacemaker implant. Mnltisite and alternate site pacing as well as pacing algorithms have not yet proven to be of significant benefit in atrial fibrillation prevention. 

Reduction in the incidence of atrial fibrillation consequent to atrial pacing could plausibly decrease the incidence of thromboembolic stroke. However, as discussed above, the reduction in atrial fibrillation is relatively small and in the elderly pacemaker population, atrial fibrillation is only one of several causes of stroke. Additionally, the high use of anticoagulation in pacemaker patients (72% in the MOST study (50)) may substantially reduce the magnitude of benefit of prevention of atrial fibrillation with atrial-based pacing. 

Stambler BS, Ellenbogen KA, Orav EJ, Sgarbossa EB, Estes NA, Rizo-Patron C, Kirchhoffer JB, Hadjis TA, Goldman L, Lamas GA. Predictors and clinical impact of atrial fibrillation after pacemaker implantation in elderly patients treated with dual chamber versus ventricular pacing. Pacing Clin Electmphysiol. 

Carlson MD, Ip J, Messenger J, Beau S, Kalbfleisch S, Gervais P, Cameron DA, Duran A, Val-Mejias J, MackaU J, Gold M. A new pacemaker algorithm for the treatment of atrial fibrillation results of the Atrial Dynamic Overdrive Pacing Trial (ADOPT). JAm CoU Cardiol. 2003 42 627-633. 

When selecting the type of pacemaker, the first question should be, What is the status of the atrium and can it be paced and/or sensed The relatively unimportant contribution of AV synchrony to the cardiac output on exercise (as opposed to the increase in heart rate) should not detract from the well-established benefits of maintaining AV synchrony at rest for the prevention of hanodynamic (such as the pacemaker syndrome) and electrophysiological complications of atrial dysfunction (atrial fibrillation). One should be guided by the statement by the British Pacing and Electrophysiology Group that the atrium should be paced/sensed unless contraindicated (35). Therefore, the... 

Fig. 12.1 The cumulative risk of developing atrial fibrillation according to the mode of cardiac pacing. Patients with an atrial or dual chamber pacemaker were significantly less likely to develop AF compared to patients receiving a ventricular pacemaker. Reprinted with permission from Kerr CR, Connolly SJ, Abdollah MB et al. Circulation 2004 109 357-62.

Fig. 12.2 An example of atrial fibrillation (AF) organizing into atrial flutter. A. The upper strip in the top panel demonstrates the atrial electrogram (EGM) and the lower strip demonstrates the annotated markers indicating how the pacemaker classifies each atrial and ventricular event as well as the cycle length (in ms) between each interval. The atrial electrogram shows the rapid irregular atrial rhythm which subsequently transitions into an organized atrial tachycardia. B. Atrial antitachycardia pacing (ATP) therapy - a burst train followed by two premature extrastimuli is delivered restoring atrial paced rhythm. The marker channel notations indicate how the device classifies each beat. Inter-beat intervals are also shown (in ms). AP - atrial paced event VP - ventricular paced event AR - atrial event sensed in atrial refractory period FS - AF sensed event TD - tachycardia detected TS - tachycardia sensed event. Courtesy AM Gillis.

Ozcan C, Jahangir A, Friedman PA, et al. Long-term survival after ablation of the atrioventricular node and implantation of a permanent pacemaker in patients with atrial fibrillation. N Engl J Med. 2001 344 1043-51. 

McComb JM, Gribbin GM. Chronic atrial fibrillation in patients with paroxysmal atrial fibrillation, atrioventricular node ablation and pacemakers. Europace 1999 1 30-34. 

The book is divided into four sections. The first section describes pacing leads and pacemaker function. The second section focuses on device implantation. New to this edition is a chapter on implantation of left ventricular leads, used in the biventricular pacing systems intended to treat patients with heart failure. Purposely we have asked two experienced implanters to discuss then-personal methods for placing leads in the cardiac venous systems to illustrate the diversity of techniques and tricks of the trade. The third section reviews the use of implantable cardiac devices in particular clinical situations. All of the chapters from the first edition have been extensively revised new to this edition are chapters on device use for patients with atrial fibrillation, heart failure, and syncope, providing further evidence for the expanding indications... 

The authors of a review of the cardiac toxicity associated with paclitaxel treatment concluded that the overall incidence of serious cardiac events is low (0.1%). The causal relation of paclitaxel to atrial and ventricular dysrhythmias and cardiac ischemia is not entirely clear [32 ]. Reported events include ventricular tachycardia, Mobitz I (Wenckebach syndrome), Mobitz U atrioventricular block, complete atrioventricular block (requiring pacemaker insertion), acute myocardial infarction, supraventricular tachycardia, and atrial fibrillation. 

This pacemaker may be used in patients who have chronic atrial fibrillation with slow ventricular response and those who need infrequent pacing. 

Another use for defibrillators is to shock either atrial flutter or fibrillation, which are abnormally rapid atrial rhythms. These atrial rhythms are much less likely to spontaneously proceed rapidly to death than ventricular arrhythmias. Using electrical shock to treat rapid heart arrhythmias other than VF is usually referred to as cardioversion and hence some users refer to the tachycardia treatment devices as cardioverter—defibrillators. Cardiovertor and defibrillator treatment is different from pacemaker treatment (discussed elsewhere in this book) because a pacemaker stimulates a slowly beating heart and uses much weaker shocks. Pacemaking increases the rate of the relatively healthy heart, which increases blood flow. 

Undersensing. Inappropriate delivery of pacing stimuli when the pacemaker system fails to sense P-waves or QRS complexes defines undersensing. Delivery of stimuli can be harmful if they occur during the atrial and ventricular relative refractory periods that are predisposed to tachyarrhythmia induction. Of particular concern is the induction of ventricular tachycardia or fibrillation when ventricular pacing occurs on the terminal portion of the T-wave ( R-on-T ), especially in the critical care setting where concomitant ischemia, metabolic and electrolyte abnormalities are frequently present. 

---