Dr. Gonzalo Baron Esquivias,
This article is written by the author for the newsletter of the Council for Cardiology Practice. It reflects the opinion of the author. Six years after the last ESC Guidelines for cardiac pacing and resynchronization therapy (2007), 18 Task Force members, 26 ESC Committee for Practice Guidelines members and 26 reviewers contributed to a practical, new and short guideline on cardiac pacing and cardiac resynchronization therapy (CRT). With only 40 pages the document outlines an innovative classification of bradyarrhythmias by mechanism and also focuses on the strength of indications for CRT mainly in the presence or absence of left bundle branch block.
The document contains 65 recommendations: 30 for pacing indications (ten less compared with ESC 2007 guidelines) and 15 for CRT indications (ten more compared with ESC 2007 guidelines).
Among these 65 recommendations:
In regard to levels of evidence:
After a short preamble, the document is divided in two sections: 1. Indications for pacing and 2. Indications for cardiac resynchronization therapy. In both sections, after the indications, specific modes of pacing recommendations are suggested and clinical perspectives are recommended at the end of each chapter.
The first innovation is the classification of bradyarrhythmias according to mechanism i.e. the clinical presentation because it is more useful for selecting patients for permanent cardiac pacing therapy than their aetiology. The first fourteen pages divide the pacing indications in three main groups:
In the diagnosis of bradyarrhythmia the document highlights how it is usually made from a standard ECG when persistent, and from a standard ECG or more prolonged ECG recordings [ambulatory monitoring or implantable loop recorder (ILR)] when intermittent. When a bradycardia is suspected but not documented, provocative testing or an electrophysiological study (EPS) may be required. Since there is no defined heart rate below which treatment is indicated, correlation between symptoms and bradyarrhythmia is essential when deciding on the need for cardiac pacing therapy. This can be difficult to establish in patients with competing mechanisms for their symptoms. In general, an attempt to obtain ECG documentation during syncope (symptom-arrhythmia correlation) is warranted (see below).
1A. Pacing is indicated in patients with persistent bradicardia (sinus bradycardia or AV block):
1B. Pacing is indicated in patients with intermittent documented bradycardia (sinus bradycardia or AV block):
1C. Pacing is indicated in patients with syncope and suspected (undocumented ) bradycardia:
Based on current guideline criteria only a small proportion of patients with heart failure (HF) (perhaps 5–10%) have cardiac dyssynchrony and are therefore indicated for CRT but this is still a large number of patients. Cardiac dyssynchrony is complex and multifaceted. Prolongation of the AV interval delays systolic contraction, inter- and intra-ventricular conduction delays lead to asynchronous contraction of LV wall regions (ventricular dyssynchrony). Cardiac resynchronization therapy (CRT) helps to restore AV, inter- and intra-ventricular synchrony, improving LV function, reducing functional mitral regurgitation and inducing LV reverse remodelling.
The Task Force reviewed the profuse literature and ascertained how the strength of indications for CRT focuses mainly on the presence or absence of left BBB. A spectrum of response to CRT, as with most other treatments, is recognized: the beneficial effects of CRT may be greater in females, patients with non-ischaemic cardiomyopathy and patients with QRS duration >150 ms (the longer the QRS duration, the greater the benefit). Recommendations are divided in three different issues:
2A. Indications for CRT in patients with heart failure and low ejection fraction in sinus rhythm
2B. Different recommendations are given for patients with atrial fibrillationThese patients are subdivided into patients with an indication for CRT and patients with an indication for AV junction ablation.
B1. Patients with HF, wide QRS and reduced LVEF:
B2. Patients with uncontrolled heart rate who are candidates for AV junction ablation CRT should be considered in patients with reduced LVEF. 2C. Different recommendations are given for an upgrade or “de novo“ implantation of CRT in patients with a brady indication for pacingC1. Upgrade from conventional PM or ICD. CRT is indicated in HF patients with LVEF <35% and high percentage of ventricular pacing who remaining NYHA class III and ambulatory IV despite adequate medical treatment.C2. “De novo” CRT implantation. CRT may be considered in HF patients, reduced EF and expected high percentage of ventricular pacing in order to decrease the risk of worsening HF.Finally the Task Force suggests a clinical guidance to the choice between CRT-P or CRT-D in primary prevention. The rate of complications in the CRT implant is not low, so in the decision process for indication for pacing/CRT and for the choice of the best modality attention should be paid to a careful evaluation of the risk of complications. In general the risk of complications is higher when implanting more complex devices and for re-intervention and upgrades.
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