The use of Implantable Cardioverter Defibrillators (ICDs) for both primary (patient with symptomatic HF (NYHA class II–III) and an EF ≤ 35%) and secondary prevention (survivors of cardiac arrest and in patients with sustained symptomatic ventricular arrhythmias) is presented and the key evidence supporting the recommendation and levels of evidence is clearly and concisely reviewed. The importance of ventricular dysrhythmia in causing sudden death in patients with heart failure is emphasized. Approximately one half of the deaths in these patients are sudden and, notably, this mode of death is most common in patients with milder symptoms. The Guidelines continue to provide the strongest class of recommendation for both primary and secondary prevention in appropriate patients (I A).
The use of Cardiac Resynchronisation Therapy (CRT) is reviewed and the key evidence supporting the class of recommendation and levels of evidence are provided. A distinction is made between the recommendations where the trial evidence is convincing and the recommendations concerning indications where the evidence is less certain. Two recent randomised clinical trials (MADIT-CRT and RAFT) have confirmed that CRT is of benefit in patients with mild (NYHA class II) symptoms. Efficacy in more symptomatic patients has been established by earlier trials.
There is consensus that patients expected to survive with good functional status for >1 year should receive a CRT device (CRT-P/CRT-D) if they are in sinus rhythm, their LVEF is low (<30%), the QRS duration is markedly prolonged (150 ms), and the ECG shows a left bundle branch pattern, irrespective of the severity of symptoms (I A). The Guideline recommendations distinguish between LBBB and non-LBBB morphology in all symptomatic patients regardless of the severity of symptoms, and require a wider QRS complex (>150 ms) for patients with non-LBBB morphology (IIa A).
There is less consensus concerning the indications for CRT in patients with atrial fibrillation (AF) as well as in patients with a conventional indication for pacing. In AF, the Guidelines recommend that CRT-P/CRT-D may be considered in patients in NYHA functional class III or ambulatory class IV with a QRS duration > 120 ms and an EF ≤ 35%, who are expected to survive with good functional status for > 1 year, to reduce the risk of worsening HF (IIb C). The recommendations emphasize the importance of adequate control of the ventricular rate, either by pharmacologic treatment or via AV node ablation, in order to ensure pacing dependency and adequate delivery of CRT .
In patients with a conventional indication for pacing, the guidelines state that CRT should be considered in patients in NYHA functional class III or IV with an EF ≤ 35%, irrespective of QRS duration (IIa C) and may be considered in patients in NYHA functional class II with an EF ≤ 35%, irrespective of QRS duration, to reduce the risk of worsening HF due to a pacing-induced prolongation of intraventricular conduction (IIb C).
There remain potential CRT candidates for whom the current trial evidence is inadequate to make evidence-based recommendations. The efficacy of upgrading from a previously implanted ICD or pacemaker to a CRT in selected patients remains to be addressed. The potential role of CRT in patients with a narrow QRS duration and demonstrable “mechanical dyssynchrony” detected by an imaging technique is currently being addressed.
Interestingly, we still do not have adequate trial evidence to make clear recommendations concerning the choice of device; CRT-P vs. CRT-D. The ICD component is clearly preferable in patients more likely to suffer from arrhythmic death, especially in younger patients. In the absence of RCT evidence, clinicians are advised to consider the patient´s biological age and prognosis, the severity of symptoms, the extent of comorbidity as well as the efficient use of health resources in making this frequently difficult clinical decision.