Cardiac pacing in humans with implantable devices began on 8 October 1958, when Professor ─éÔÇĞke Senning implanted the first pacemaker in a 43-year old Swedish engineer at Karolinska Hospital in Stockholm, Sweden. 1Today, it is estimated that about three million people worldwide have a pacemaker and each year, about 600,000 pacemakers are implanted. The objective of this article is to give an overview about what can be considered to be standard pacemaker therapy in developed countries and what might be expected from this therapy in the future.
Pacemaker Therapy Today
The heart’s ‘natural’ pacemaker is called the sinoatrial node or sinus node (see Figure 1). It produces the electrical impulses that cause the heart to beat. These impulses travel down specific electrical pathways to reach the ventricles.
Figure 1: Schematic Illustration of the Heart and its Structures
Heart rhythm problems occur when the natural pacemaker is defective1 or when the heart’s electrical pathways are blocked, 2 causing the heartbeat to be too slow.
The most frequent rhythm disorders are the sick sinus syndrome, if the sinus node is too slow; and the first, second or third degree atrioventricular (AV) block, if electrical pathways are blocked. The resulting slow heart rate, below 50 beats per minute, is called bradycardia and usually causes symptoms such as fainting, or dizzy spells. These symptoms require therapy: in this case, the implantation of a permanent cardiac pacemaker.
Today, there is general agreement about the symptoms and findings that should be present to justify pacemaker implantation. These agreements have been summarised in pacemaker guidelines, e.g. the joint American College of Cardiology (ACA), American Hospital Association (AHA) and North American Society of Pacing and Electrophysiology (NASPE) guidelines, which have recently been updated. 2
The next question to be answered is what kind of pacemaker device should be chosen in an individual patient. Basically, three different kinds of pacemaker systems are available:
- the single-chamber ventricular pacemaker (see Figure 2);
Figure 2: Schematic Illustration of a Single-chamber Ventricular Pacemaker
- the single-chamber atrial pacemaker (see Figure 3); and
Figure 3: Schematic Illustration of a Singlechamber Atrial Pacemaker
- the dual-chamber, AV universal pacemaker (see Figure 4).
Figure 4: Schematic Illustration of a Dual Chamber Pacemaker
All the available guidelines recommend using a pacemaker device with atrial contribution – i.e. a single-chamber atrial or dual-chamber pacemaker – whenever possible.
- B Larsson, H Elmquist, L Ryd─é┬®n and H Sch─é─¢ller, ├óÔé¼┼øLessons from the First Patient with an Implanted Pacemaker ├óÔé¼ÔÇ£ 1958├óÔé¼ÔÇ£2001├óÔé¼┼Ñ, P. A. C. E., 26 (2003), pp. 114├óÔé¼ÔÇ£124.
- G Gregoratos, J Abrams, A Epstein, et al., ├óÔé¼┼øACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices: Summary Article ├óÔé¼ÔÇ£ A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/NASPE Committee to Update the 1998 Pacemaker Guidelines)├óÔé¼┼Ñ, Circulation, 106 (2002), pp. 2,145├óÔé¼ÔÇ£2,161.
- H R Andersen, J C Nielsen, P E B Thomsen, L Thuesen, P T Mortensen, T Vesterlund and A K Pedersen, ├óÔé¼┼øLongterm Follow-up of Patients from a Randomised Trial of Atrial Versus Ventricular Pacing for Sick-sinus Syndrome├óÔé¼┼Ñ, Lancet, 350 (1997), pp. 1,210├óÔé¼ÔÇ£1,216.
- G A Lamas, E J Orav, B S Stambler, et al., for the Pacemaker Selection in the Elderly Investigators, ├óÔé¼┼øQuality of Life and Clinical Outcomes in Elderly Patients Treated with Ventricular Pacing as Compared with Dual-chamber Pacing├óÔé¼┼Ñ, N. Engl. J. Med., 338 (1998), 1,097├óÔé¼ÔÇ£1,104.
- S J Connolly, C R Kerr, M Gent, R S Roberts, S Yusuf, A M Gillis, M H Sami, M Talajic, A S L Tang, G J Klein, C Lau and D M Newman, ├óÔé¼┼øEffects of Physiologic Pacing Versus Ventricular Pacing on the Risk of Stroke and Death Due to Cardiovascular Causes├óÔé¼┼Ñ, N Engl J Med, 342 (2000), 1,385├óÔé¼ÔÇ£1,391.
- C R Kerr, S J Connolly, H Abdollah, R S Roberts, M Gent, S Yusuf, A M Gillis, A S L Tang, M Talajic, G J Klein and D M Newman, for the Canadian Trial of Physiological Pacing (CTOPP) Investigators, ├óÔé¼┼øCanadian Trial of Physiological Pacing: Effects of Physiologic Pacing During Long-term Follow-up├óÔé¼┼Ñ, Circulation, 109 (2004), pp. 357├óÔé¼ÔÇ£362.
- G A Lamas, L L Kerry, M O Sweeney, R Silverman, A Leon, R Yee, R A Marinchak, G Flaker, E Schron, E J Orav, A S Hellkamp and L Goldman, ├óÔé¼┼øVentricular Pacing or Dual-chamber Pacing for Sinus-node Dysfunction├óÔé¼┼Ñ, N. Engl. J. Med., 346 (2002), pp. 1,854├óÔé¼ÔÇ£1,862.
- A V Mattioli, D Vivoli and G Mattioli, ├óÔé¼┼øInfluence of Pacing Modalities on the Incidence of Atrial Fibrillation in Patients Without Prior Atrial Fibrillation: A Prospective Study├óÔé¼┼Ñ, Eur. Heart J., 19 (1998), pp. 282-286.
- J M Wharton, R A Sorrentino, P Campbell, et al., ├óÔé¼┼øEffect of Pacing Modality on Atrial Tachyarrhythmia Recurrence in the Tachy-bradycardia Syndrome: Preliminary Results of the Pacemaker Atrial Tachycardia (PAC-A-TACH) Study [Abstract]├óÔé¼┼Ñ, Circulation, 98 (1998), p. 2,601.
- K A Ellenbogen, A S Hellkamp, B L Wilkoff, J L Camunas, J C Love, T A Hadjis, K L Lee and G A Lamas, ├óÔé¼┼øComplications Arising after Implantation of DDD Pacemakers: The MOST Experience├óÔé¼┼Ñ, Am. J. Cardiol., 92 (2003), pp. 740├óÔé¼ÔÇ£749.
- M O Sweeney, A S Hellkamp, K A Ellenbogen, A J Greenspon, R A Freedman, K L Lee and G A Lamas, for the MOST Investigators, ├óÔé¼┼øAdverse Effect of Ventricular Pacing on Heart Failure and Atrial Fibrillation Among Patients with Normal Baseline QRS Duration in a Clinical Trial of Pacemaker Therapy for Sinus Node Dysfunction├óÔé¼┼Ñ, Circulation, 107 (2003), pp. 2,932├óÔé¼ÔÇ£2,937.
- B L Wilkoff, J R Cook, A E Epstein, H L Greene, H P Hallstrom, H Hsia, S P Kutalek and A Sharma, ├óÔé¼┼øDualchamber Pacing or Ventricular Backup Pacing in Patients with an Implantable Defibrillator: The Dual-chamber and VVI Implantable Defibrillator (DAVID) Trial├óÔé¼┼Ñ, J. A. M. A., 288 (2002), pp. 3,115├óÔé¼ÔÇ£3,123.
- The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) Investigators, ├óÔé¼┼øA Comparison of Rate Control and Rhythm Control in Patients with Atrial Fibrillation├óÔé¼┼Ñ, N. Engl. J. Med., 347 (2002), pp. 1,825├óÔé¼ÔÇ£1,833.
- I C Van Gelder, V E Hagens, H A Bosker, et al., ├óÔé¼┼øA Comparison of Rate Control and Rhythm Control in Patients with Recurrent Persistent Atrial Fibrillation├óÔé¼┼Ñ, N. Engl. J. Med., 347 (2002), pp. 1,834├óÔé¼ÔÇ£1,840.
- V E Hagens, A V Ranchor, E Van Sonderen, et al., ├óÔé¼┼øEffect of Rate or Rhythm Control on Quality of Life in Persistent Atrial Fibrillation: Results from the Rate Control Versus Electrical Cardioversion (RACE) Study├óÔé¼┼Ñ, J Am Coll Cardiol., 43 (2004), pp. 241├óÔé¼ÔÇ£247.
- A Auricchio, C Stellbrink, S Sack, et al., ├óÔé¼┼øLong-term Clinical Effect of Hemodynamically Optimized Cardiac Resynchronization Therapy in Patients with Heart Failure and Ventricular Conduction delay├óÔé¼┼Ñ, J. Am. Coll. Cardiol., 39 (2002), pp. 2,026├óÔé¼ÔÇ£2,033.
- S Cazeau, C Leclercq, T Lavergne, et al., for the Multisite Stimulation In Cardiomyopathies (MUSTIC) Study Investigators, ├óÔé¼┼øEffects of Multisite Biventricular Pacing in Patients with Heart Failure and Intraventricular Conduction Delay├óÔé¼┼Ñ, N. Engl. J. Med., 344 (2001), pp. 873├óÔé¼ÔÇ£880.
- C Leclercq, S Walker, C Linde, J Clementy, A J Marshall, P Ritter, P Djiane, P Mabo, T Levy, F Gadler, C Bailleul and J C Daubert, on behalf of the MUSTIC Study Group, ├óÔé¼┼øComparative Effects of Permanent Biventricular and Right-univentricular Pacing in Heart Failure Patients with Chronic Atrial Fibrillation├óÔé¼┼Ñ, Eur. Heart J., 23 (2002), pp. 1,780├óÔé¼ÔÇ£1,787.
- W T Abraham, W G Fisher, A L Smith, D B Delurgio, A R Leon, E Loh, D Z Kocovic, M Packer, A L Clavell, D L Hayes, M Ellestad and J Messenger, for the MIRACLE Study Group, ├óÔé¼┼øCardiac Resynchronization in Chronic Heart Failure├óÔé¼┼Ñ, N. Engl. J. Med., 346 (2002), pp. 1,845├óÔé¼ÔÇ£1,853.
- J B Young, W T Abraham, A L Smith, A R Leon, R Lieberman, B Wilkoff, R C Canby, J S Schroeder, L B Liem, S Hall and K Wheelan for The Multicenter InSync ICD Randomized Clinical Evaluation (MIRACLE ICD) Trial Investigators, ├óÔé¼┼øCombined Cardiac Resynchronization and Implantable Cardioversion Defibrillation in Advanced Chronic Heart Failure: The MIRACLE ICD Trial├óÔé¼┼Ñ, JAMA, 289 (2003), pp. 2,685├óÔé¼ÔÇ£2,694.
- T V Salukhe, D P Francis and R Sutton, ├óÔé¼┼øComparison of Medical Therapy, Pacing and Defibrillation in Heart Failure (COMPANION) Trial Terminated Early; Combined Biventricular Pacemaker-defibrillators Reduce Allcause Mortality and Hospitalization├óÔé¼┼Ñ, Int. J. Cardiol., 87 (2003), pp. 119├óÔé¼ÔÇ£120.