ICD and CRT indications in heart failure — viva

Stem

Practice viva. You are the cardiology registrar in the heart failure clinic. The examiner works through who needs an implantable cardioverter-defibrillator (ICD), when, who needs cardiac resynchronization therapy (CRT), and where conduction system pacing and wearable defibrillators fit, across European, North American and Australian guidance.^[1]

Branch A — Why an ICD at all?

Examiner: Why not just give amiodarone to patients with heart failure with reduced ejection fraction (HFrEF) at risk of sudden death?

• The 2026 European Society of Cardiology (ESC) heart failure guideline states that antiarrhythmic drugs such as amiodarone and dronedarone reduce ventricular arrhythmias but do not prolong survival and may shorten it.^[1]
• ESC 2026 reports that in SCD-HeFT, compared with amiodarone, an ICD reduced all-cause death by 23% in patients with HFrEF.^[1]
• ESC 2026 states that ICDs are effective in preventing sudden cardiac death (SCD) and prolonging survival in patients with HFrEF at high risk of SCD.^[1]

Examiner: So who benefits least?

• ESC 2026: the effect of ICD treatment depends on the competing risk of non-sudden death, so in patients with many comorbidities and older age the benefit may be substantially lower.^[1]
• 2022 American Heart Association/American College of Cardiology/Heart Failure Society of America (AHA/ACC/HFSA): ICD and CRT with defibrillation (CRT-D) are not indicated when comorbidities or frailty limit survival with good functional capacity to <1 year (COR 3: No Benefit, LOE C-LD).^[5]

Branch B — The primary-prevention rows

Examiner: Give me the ESC 2026 primary-prevention rows.

• Ischaemic: an ICD is recommended in symptomatic HFrEF (New York Heart Association [NYHA] class II/III) of ischaemic aetiology (unless there was a myocardial infarction [MI] in the prior 40 days), with left ventricular ejection fraction (LVEF) ≤35% despite ≥3 months of optimal foundational medical therapy (FMT), provided survival longer than 1 year with good functional status is expected, to reduce the risk of sudden death and all-cause death (Class I, Level B1).^[1]
• Non-ischaemic: with the same conditions, an ICD should be considered to reduce the risk of sudden death and all-cause death (Class IIa, Level B1).^[1]
• ESC 2026 bases selection on RCT LVEF thresholds and aetiology because non-ischaemic HF may derive less benefit, while noting a meta-analysis of RCTs showed an overall survival benefit even in non-ischaemic HF.^[1]

Examiner: And an asymptomatic post-infarct patient with LVEF 28%?

• ESC 2026 Recommendation Table 6 has no NYHA class I row, so among the guidelines checked for this topic the ESC 2022 chronic coronary artery disease (CAD) row applies: ICD therapy should be considered in CAD, NYHA class I and LVEF ≤30% despite ≥3 months of optimal medical therapy (Class IIa, Level B).^[3][1]
• 2022 AHA/ACC/HFSA had recommended ICD therapy for primary prevention of SCD to reduce total mortality at least 40 days post-MI with LVEF ≤30%, NYHA class I symptoms on guideline-directed medical therapy (GDMT) and reasonable expectation of meaningful survival for >1 year (COR 1, LOE B-R); that is an earlier row, and for post-MI patients the newer 2025 ACC/AHA ACS row below applies.^[5]
• For post-MI patients, the 2025 ACC/AHA acute coronary syndrome (ACS) guideline recommends an ICD in selected patients with LVEF ≤40% (its Table 17, where LVEF ≤30% covers NYHA class I, II or III) at least 40 days post MI and at least 90 days postrevascularization, to reduce death (COR 1, LOE A).^[8]

Branch C — Timing

Examiner: Why wait after an MI?

• ESC 2022 states that early routine prophylactic ICD in the first 40 days after MI did not reduce mortality in post-MI patients with reduced LVEF in two randomized trials (DINAMIT and IRIS), and is therefore not recommended.^[3]
• ESC 2026: ICD implantation for primary prevention is not recommended within 40 days of an MI (Class III, Level B1).^[1]
• ESC 2023 ACS: with pre-discharge LVEF ≤40%, repeat evaluation of LVEF 6–12 weeks after an ACS (and after complete revascularization and the institution of optimal medical therapy) is recommended to assess the potential need for a primary-prevention ICD (Class I, Level C).^[9]
• ESC 2022 had given a similar row: in patients with pre-discharge LVEF ≤40%, re-evaluation of LVEF 6–12 weeks after MI is recommended to assess the potential need for primary-prevention ICD implantation (Class I, Level C).^[3]
• 2022 AHA/ACC/HFSA supportive text: re-evaluation of EF >40 days after MI, >90 days after revascularization and >90 days after GDMT is useful to determine ICD or CRT candidacy.^[5]

Examiner: What does the wait cost?

• ESC 2026: delaying ICD implantation carries a risk of SCD of 2%–4% by 6 months and ∼7% by 1 year.^[1]
• ESC 2026 text (no class or level given) calls a 3-month period after uptitration of FMT before considering an ICD reasonable.^[1]

Branch D — CRT

Examiner: Which patient gets Class I CRT, and where does the evidence weaken?

• ESC 2026: CRT is recommended in symptomatic HFrEF with LVEF ≤35% despite optimal FMT, in sinus rhythm (SR) with left bundle branch block (LBBB) and QRS ≥150 ms, in order to improve symptoms and reduce the risk of hospitalizations and death (Class I, Level A).^[1]
• In the same population (symptomatic HFrEF, LVEF ≤35% despite optimal FMT, in SR), ESC 2026 says CRT should be considered with non-LBBB QRS ≥150 ms or LBBB 130–149 ms, in order to improve symptoms and reduce morbidity and death (both Class IIa, Level C), may be considered with non-LBBB 130–149 ms in order to improve symptoms and reduce morbidity and death (Class IIb, Level C), and is not recommended with QRS <130 ms without an indication for pacing due to high-degree atrioventricular (AV) block (Class III, Level A).^[1]
• ESC 2021 explained that MADIT-CRT, REVERSE and RAFT suggest that there is likely to be potential benefit in all patients with LBBB regardless of QRS duration, whereas benefit with non-LBBB is evident mostly with QRS ≥150 ms.^[2]
• 2022 AHA/ACC/HFSA starts its sinus-rhythm CRT rows at 120 ms and does not recommend CRT with QRS <120 ms (COR 3: No Benefit, LOE B-R), or with NYHA class I or II and non-LBBB with QRS <150 ms (COR 3: No Benefit, LOE B-NR).^[5]

Examiner: A patient needs a pacemaker for complete heart block and has LVEF 45% with HF symptoms. RV pacing?

• ESC 2026 defines HFrEF as LVEF <50% with symptoms and/or signs of HF, and says CRT, rather than right ventricular (RV) pacing, should be considered in HFrEF regardless of NYHA class or QRS width with an indication for ventricular pacing for high-degree AV block, in order to reduce the risk of HF hospitalization and death (Class IIa, Level B1).^[1]
• 2022 AHA/ACC/HFSA: in high-degree or complete heart block with LVEF 36% to 50%, CRT is reasonable to reduce total mortality, reduce hospitalizations, and improve symptoms and QOL (COR 2a, LOE B-R).^[5]
• The 2023 HRS guideline: in patients with a pacing indication and LVEF 36%−50% who are anticipated to require substantial ventricular pacing, cardiac physiologic pacing (CPP) is reasonable to reduce the risk of pacing-induced cardiomyopathy (COR 2a, LOE B-R for CRT and B-NR for HBP and LBBAP).^[6]
• ESC 2021 had given a His bundle pacing row for this LVEF band: HBP may be considered as an alternative to RV pacing in patients with AV block and LVEF >40% who are anticipated to have >20% ventricular pacing (Class IIb, Level C).^[2] That is an earlier row: with LVEF 45% he has HFrEF under ESC 2026, and for HFrEF the later ESC 2026 HF guideline makes no recommendation on conduction system pacing because no RCT with patient-centred outcomes has evaluated it.^[1]
• The dated NHFA/CSANZ 2018 row says CRT should be considered in HFrEF with LVEF ≤50% and high-grade AV block requiring pacing, to decrease hospitalisation for HF (Weak recommendation FOR; moderate quality of evidence).^[7]

Branch E — Conduction system pacing

Examiner: Would you offer left bundle branch area pacing instead of biventricular CRT?

• ESC 2026 states that left bundle branch area pacing may prove a feasible alternative to CRT when implantation is challenging, but that no RCT with patient-centred outcomes has evaluated CSP in HFrEF and no recommendations can currently be made.^[1]
• HRS 2023: in LVEF ≤35%, SR, LBBB with QRS ≥150 ms and NYHA class II-IV on GDMT, CSP with HBP with LBBB correction or LBBAP is reasonable if effective CRT cannot be achieved with biventricular pacing based on anatomical or functional criteria (COR 2a, LOE C-LD), and may be considered as an alternative to CRT with biventricular pacing (COR 2b, LOE C-LD).^[6]
• HRS 2023 also has a crossover row: in patients undergoing CRT with biventricular pacing implantation via the coronary sinus, crossover to CSP with HBP or LBBAP is reasonable when the coronary sinus left ventricular lead placement is unsuccessful or suboptimal (COR 2a, LOE C-LD).^[6]
• ESC 2021 had said that when coronary sinus lead implantation is unsuccessful in a CRT candidate, His bundle pacing (HBP) should be considered as a treatment option along with other techniques such as a surgical epicardial lead (Class IIa, Level B).^[2] That is an earlier row: for HFrEF, the later ESC 2026 statement that no recommendations on CSP can currently be made is the ESC position.^[1]

Branch F — Wearable and subcutaneous defibrillators

Examiner: When would you use a wearable defibrillator, and when a subcutaneous ICD?

• ESC 2026: a wearable cardioverter-defibrillator (WCD) may be considered in patients with HF at risk of SCD for a limited period, to increase survival as a bridge to decision for permanent ICD implantation or while listed for heart transplantation (Class IIb, Level C); its text adds that no mortality benefit has been shown in RCTs.^[1]
• ESC 2022 says the WCD should be considered for adults with a secondary-prevention ICD indication who are temporarily not candidates for ICD implantation (Class IIa, Level C). For patients with HF, the later ESC 2026 HF WCD row above, with its own conditions, is the later ESC row on WCD use.^[3][1]
• ESC 2022: a subcutaneous defibrillator should be considered as an alternative to a transvenous defibrillator when pacing therapy for bradycardia, cardiac resynchronization or anti-tachycardia pacing is not needed (Class IIa, Level B).^[3]

Branch G — Australia and New Zealand

Examiner: What does the Australian guideline say?

• The 2018 National Heart Foundation of Australia/Cardiac Society of Australia and New Zealand (NHFA/CSANZ) guideline predates the other guidelines here, so its rows are dated.^[7]
• NHFA/CSANZ 2018: an ICD should be considered for primary prevention at least 1 month following MI with LVEF ≤30% (Strong recommendation FOR; high quality of evidence), and may be considered in HFrEF with dilated cardiomyopathy and LVEF ≤35% (Weak recommendation FOR; low quality of evidence).^[7]
• NHFA/CSANZ 2018: CRT is contraindicated with QRS duration of less than 130 ms, because of lack of efficacy and possible harm (Strong recommendation AGAINST; moderate quality of evidence).^[7]