Pacemakers are electronic devices that stimulate the heart with electrical impulses to maintain or restore a normal heartbeat. In 1952, Zoll described an effective means of supporting the patients with intrinsic cardiac pacemaker activity and/or conducting tissue by an artificial, electric, external pacemaker. The pacing of the heart was accomplished by subcutaneous electrodes but could be maintained only for a short period. In 1957, complete heart block was treated using electrodes directly attached to the heart. These early observations instilled the idea that cardiac electrical failure can be controlled. It ultimately led to the development of totally implantable pacemaker by Chardack, Gage, and Greatbatch. Since then, there have been several advancements in the pacemakers, and the modern-day permanent pacemaker is subcutaneously placed device.[1][2][3]There are 3 types of artificial pacemakers:
All cardiac pacemakers consist of 2 components: a pulse generator which provides the electrical impulse for myocardial stimulation and 1 or more electrodes or leads which deliver the electrical impulse from the generator to the myocardium. This discussion focuses on the indications of pacemaker placement.
The most common indications for permanent pacemaker implantation are sinus node dysfunction (SND) and high-grade atrioventricular (AV) block. Guidelines for implantation of cardiac pacemakers have been established by a task force formed jointly by the American College of Cardiology (ACC), the American Heart Association (AHA), and the Heart Rhythm Society (HRS). The European Society of Cardiology has established similar guidelines. [4] ACC/AHA/HRS divides indications of pacemaker implantation into 3 specific classes:
Following conditions are included in the ACC/AHA/HRS guidelines for the pacemaker insertion.[5][6][4][7][8] We will discuss Class I and II recommendations.
Sinus Node Dysfunction
Class I indications
Class II indications
Acquired Atrioventricular (AV) Block
Class I indications
Class II indications
Chronic Bifascicular Block
Class I indications
Class II indications
After Acute Phase of Myocardial Infarction
Class I indications
Class II indications
Neurocardiogenic Syncope and Hypersensitive Carotid Sinus Syndrome
Class I indications
Class II indications
Post Cardiac Transplantation
Class I indications
Class II indications
Hypertrophic Cardiomyopathy (HCM)
Class I indications
Class II indications
Pacing to Prevent Tachycardia
Class I indications
Class II indications
Cardiac Resynchronization Therapy (CRT) in Patients with Severe Systolic Heart Failure
Class I indications
Class II indications
Congenital Heart Disease
Class I indications
Class II indications
Like in any procedure, the insertion of pacemaker insertion should be chosen wisely for a particular patient. There are situations in which pacemaker insertion is not beneficial or is not enough data to support its use. These are sometimes also called class III indications in ACC/AHA/HRS guidelines or European Society of Cardiology guidelines.
The pacing and CRT are associated with complications. The majority of complications occur in the hospital or during first 6 months. Lead complications are the main reason for the re-implantation of the pacemaker and CRT devices. Other complications include, but are not limited to infections, hematoma formation, pericardial effusion or tamponade, pneumothorax, coronary sinus dissection, or perforation. Some old pacemakers are not MRI safe. [10]
Pacemaker implantation has shown a mortality benefit. The CARE-HF (Cardiac Resynchronization in Heart Failure) trial limited subjects to the QRS duration greater than 150 ms (89% of patients) or QRS duration 120 to 150 ms with echocardiographic evidence of dys-synchrony (11% of patients). It was the first study to show a significant (36%) reduction in the death rate for resynchronization therapy unaccompanied by backup defibrillation compared with guideline-directed medical therapy (GDMT). There has been evidence from the multiple randomized trials of CRT-D in patients with reduced LVEF and NYHA class II shows that CRT can provide functional improvement and decrease the risk of HF events and composite outcomes. In clinical trials, CRT-D has not shown improvement in NYHA class I Heart failure. The ACC/AHA/HRS guidelines from 2012 thoroughly reviewed the conditions of hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia/cardiomyopathy, genetic arrhythmia syndrome, terminal care, and congenital heart disease, and no changes were made as compared to 2008 guidelines in these conditions. There was a change in guidelines for indications of CRT insertion in the 2012 ACC/AHA/HRS guidelines as compared to 2008 guidelines. These are incorporated in the indications for pacemaker section mentioned above.
New guidelines recommend CRT in a patient with QRS duration greater than or equal to 150 ms instead of 120 ms based on multiple analysis/studies (class I indication). An additional difference in CRT recommendations includes patients with QRS duration greater than or equal to 150 ms with LBBB as class I indication. Newer guidelines based on multiple studies suggest that in patients who have QRS greater than or equal to 120 ms but does not have complete LBBB, the evidence of benefit from CRT is less compelling. The European Society of Cardiology guidelines are similar to the ACC/AHA/HRS guidelines, but there are few differences. One major difference noted is ESC guidelines have CRT indication for QRS less than or equal to 120 ms in patients with atrial fibrillation (in whom we have inadequate rate control requiring AV node ablation) and heart failure with EF less than or equal to 35%. The ACC/AHA/HRS guidelines have no such indication.
There are some areas where the indications for a pacemaker are clear, but there are few areas where clinical judgment and expertise plays a greater role. Although the guidelines attempt to define practices that meet the needs of most patients, the ultimate decision for the patient should be based on particular patient presenting scenario, clinician judgment, and discussion with the patient about risks and benefits of the procedure. There are specific pacemaker generators that are used for patients with AV block and sinus node dysfunction depending upon presentation. The different types of generators include a single chamber, dual chamber, and biventricular. A cardiology consult is highly recommended prior to the insertion of a pacemaker.
[1] | Carrión-Camacho MR,Marín-León I,Molina-Doñoro JM,González-López JR, Safety of Permanent Pacemaker Implantation: A Prospective Study. Journal of clinical medicine. 2019 Jan 1; [PubMed PMID: 30609668] |
[2] | Parkash R,Sapp J,Gardner M,Gray C,Abdelwahab A,Cox J, Use of Administrative Data to Monitor Cardiac Implantable Electronic Device Complications. The Canadian journal of cardiology. 2019 Jan; [PubMed PMID: 30595171] |
[3] | Polimenakos AC,Mathis L,Shafer B,Kamath MV, Selective Use of Temporary Epicardial Pacing Leads in Early Infancy Following Cardiac Surgery: Feasibility and Determinants of Clinical Application. Pediatric cardiology. 2018 Dec 18; [PubMed PMID: 30564866] |
[4] | Bob-Manuel T,Nanda A,Latham S,Pour-Ghaz I,Skelton WP 4th,Khouzam RN, Permanent pacemaker insertion in patients with conduction abnormalities post transcatheter aortic valve replacement: a review and proposed guidelines. Annals of translational medicine. 2018 Jan; [PubMed PMID: 29404357] |
[5] | Kosztin A,Boros AM,Geller L,Merkely B, Cardiac resynchronisation therapy: current benefits and pitfalls. Kardiologia polska. 2018; [PubMed PMID: 30091132] |
[6] | Proclemer A,Zecchin M,D'Onofrio A,Boriani G,Facchin D,Rebellato L,Ghidina M,Bianco G,Bernardelli E,Pucher E,Gregori D, [The Pacemaker and Implantable Cardioverter-Defibrillator Registry of the Italian Association of Arrhythmology and Cardiac Pacing - Annual report 2016]. Giornale italiano di cardiologia (2006). 2018 Feb; [PubMed PMID: 29531385] |
[7] | Proclemer A,Zecchin M,D'Onofrio A,Botto GL,Facchin D,Rebellato L,Ghidina M,Bianco G,Bernardelli E,Pucher E,Gregori D, [The Pacemaker and Implantable Cardioverter-Defibrillator Registry of the Italian Association of Arrhythmology and Cardiac Pacing--Annual report 2014]. Giornale italiano di cardiologia (2006). 2016 Feb; [PubMed PMID: 27029759] |
[8] | Samii SM, Indications for pacemakers, implantable cardioverter-defibrillator and cardiac resynchronization devices. The Medical clinics of North America. 2015 Jul; [PubMed PMID: 26042883] |
[9] | Zartner P, [Antibradycardia therapy : Indication and implementation]. Herzschrittmachertherapie [PubMed PMID: 27221084] |
[10] | Poh PG,Liew C,Yeo C,Chong LR,Tan A,Poh A, Cardiovascular implantable electronic devices: a review of the dangers and difficulties in MR scanning and attempts to improve safety. Insights into imaging. 2017 Aug; [PubMed PMID: 28624970] |