Major updates from the 2013 ESC guidelines include:
CRT-HFrEF criteria refined: LVEF ≤35% with LBBB QRS ≥150ms now Class I (Class IIa for QRS 120-149ms)
Non-LBBB recognition: QRS ≥150ms without LBBB morphology upgraded to Class IIa for CRT (was Class IIb)
His-bundle pacing emphasis: HBP now Class IIa as alternative/backup to RV apical pacing with specific scenarios outlined
AF and CRT: AV node ablation guidance ensures ≥90-95% biventricular pacing capture rates
CSP standardization: Conduction system pacing expanded with LBBP emerging data; lead positioning refined (quadripolar recommended)
MRI updates: Expanded criteria for MRI-conditional device programming and imaging alternatives
Quality indicators: First standardized CIED registry quality metrics with complications tracking (target <5% at 30 days)
Sinus Node Dysfunction (SND) Pacing
Definition & Diagnosis
Symptomatic SND requires documented bradycardia on ambulatory ECG monitoring (≥2-second pause in sinus rhythm or heart rate <40 bpm during wake hours) in patients with specific symptoms: syncope, presyncope, dyspnea, chest discomfort, or fatigue temporally related to bradycardia.
SND Subtype
COR
Evidence
Indication Details
Symptomatic SND with documented bradycardia
Class I
A
DDD pacing preferred; VVI if AF present/anticipated
Bradycardia-tachycardia syndrome
Class I
B
DDD with rate control or VVI if AF develops
SND without documented bradycardia
Class IIb
C
Limited evidence; consider EP study results
DO: SND Best Practices
Document bradycardia (≥2-second pause, HR <40) on ambulatory ECG before pacing decision
Use DDD pacing mode in SND without AF to minimize unnecessary RV pacing
Program shorter AV delay to optimize LV filling and reduce apical RV pacing burden
Monitor patients with PM for new AF development; upgrade to CRT-D if HF develops
Avoid VVI pacing in SND unless AF present; DDD preserves AV synchrony
DON'T: Common SND Pitfalls
Pace asymptomatic bradycardia or sinus pauses without symptoms
Implant VVI pacer for SND without AF documented
Place RV lead in apical position if mid-septal alternative available
Forget frequent AF screening in SND patients post-implant
Atrioventricular Block Indications
AVB Type
COR
Evidence
Pacing Recommendation
First-degree AVB
Class III
C
No pacing needed unless AV delay >200 ms with symptoms
Second-degree Type I (Wenckebach)
Class IIb
C
Pacing only if symptomatic; rarely needed if HR >40 at rest
Second-degree Type II (Mobitz II)
Class I
B
Permanent pacing indicated (progresses to 3° AVB)
High-degree AVB
Class I
B
Permanent pacing indicated
Third-degree AVB (complete)
Class I
A
Permanent pacing; DDD preferred if AV dissociation
AVB in Special Contexts
Acute Myocardial Infarction: Persistent 3° AVB after anterior MI → permanent pacing (Class I, Evidence C). Inferior MI AVB often transient; observe 5 days before implanting.
Post-Cardiac Surgery: Complete AVB observed for ≥5 days post-op before permanent pacing (Class I). If HPS injury suspected, implant earlier (Class IIa).
Pearl: In Mobitz II, the blocked P wave appears without PR prolongation—QRS is wide and infranodal block. Wenckebach (Type I) shows progressive PR lengthening with eventual dropped beat. Mobitz II is more dangerous and requires pacing.
CRT Indications for Heart Failure
CRT candidacy hinges on three parameters: LVEF ≤35%, QRS morphology & duration, and medical optimization. The 2021 update significantly strengthens LBBB ≥150ms recommendations.
Class I Indications (Recommended)
LVEF ≤35% + LBBB QRS ≥150ms + Symptomatic HF (NYHA II-IV) on OMT
Class I, Evidence B. This is the strongest indication. LBBB morphology (broad notching, prolonged upstroke in V1-V2) predicts best response (>70% response rate).
LVEF ≤35% + LBBB QRS 120-149ms + Symptomatic HF on OMT
Class IIa, Evidence A. Smaller QRS benefit; consider if patient highly symptomatic or recurrent hospitalizations.
Class IIa Indications (Should Be Considered)
LVEF ≤35% + Non-LBBB QRS ≥150ms + Symptomatic HF on OMT
Class IIa, Evidence B. Right bundle branch block (RBBB) or non-specific morphology with wide QRS can benefit; response rates lower (~40-50%) than LBBB.
Upgrade from conventional PM to CRT
Class IIa, Evidence B. Consider in patients with systolic dysfunction (<35%), HF symptoms, and >40% RV pacing burden on conventional pacemaker.
Class IIb Indications (May Be Considered)
LVEF ≤35% + Non-LBBB QRS 120-149ms + Symptomatic HF
Class IIb, Evidence C. Limited data; response unpredictable.
LVEF 35-40% + LBBB QRS ≥120ms with reduced functional capacity
Class IIb, Evidence C. Mildly reduced EF; selectiveuse if significant symptoms.
AF and CRT
Patients with AF eligible for CRT should undergo AV nodal ablation to ensure ≥90-95% biventricular pacing capture. Intrinsic QRS must be ≥120ms LBBB morphology for CRT benefit if native rhythm preserved.
DO: CRT Selection Best Practices
Confirm LVEF ≤35% on recent echo (within 3 months preferred)
Optimize ACE/ARB, beta-blocker, aldosterone antagonist ≥3-6 weeks before CRT decision
Implant CRT for non-LBBB QRS <120ms (limited benefit, Class III)
Use CRT for LVEF >40% without compelling HF symptoms/HF hospitalization
Delay CRT in eligible patient due to borderline EF (35-40%); ICD + CRT can be beneficial if NYHA II-III
Forget RV-LV optimization window closes; reassess at 4 weeks post-implant
Conduction System Pacing (CSP)
CSP techniques (His-bundle pacing, left bundle branch pacing) aim to maintain intrinsic ventricular conduction, narrowing QRS and potentially improving outcomes versus RV apical pacing.
His-Bundle Pacing (HBP)
Class IIa, Evidence B: HBP considered for patients requiring RV pacing (SND, AVB, high-degree block) in centers with expertise. Maintains narrow QRS (<120 ms) by capturing His bundle directly.
Advantages
Preserves intrinsic RV-LV conduction; narrower QRS vs RV apical pacing
Potential reduction in RV pacing-induced cardiomyopathy risk
Can correct prolonged PR intervals (Class IIa indication)
May reduce AF incidence vs RV apical pacing (observational data)
Long-term durability data still accumulating (limited RCTs)
Left Bundle Branch Pacing (LBBP)
Class IIb, Evidence C: LBBP is emerging technique with promising early data but limited RCT evidence. Recommendations not yet standardized due to small patient series.
Direct LBB capture may offer superior resynchronization in HF patients vs RV apical pacing. However, procedural complexity, lead positioning challenges, and need for specialized training limit current use.
Pearl: CSP achieves narrower QRS (≈100-120 ms) vs RV apical (~140-160 ms), potentially reducing adverse ventricular remodeling. However, long-term HF outcomes vs CRT-D unclear. Reserve for specialized centers pending larger trials.
Class I, Evidence A Indicated in patients with chronotropic incompetence (inability to increase HR appropriately during exertion). Used in DDDR or VVIR modes to sensor-mediate rate response when intrinsic AV node cannot accommodate increased metabolic demand.
RV Pacing Minimization Strategies
Short AV delay programming: 50-100 ms intrinsic AV intervals favor native conduction over pacing
Search algorithm: Periodic high-rate testing to detect intrinsic conduction recovery
Atrial pacing only: AAI/AAIR mode if AV node intact and SND isolated (Class IIa)
Use DDD in SND without AF; program short AV delay (50-100 ms) to minimize RV pacing
Assess for chronotropic incompetence in active patients; add rate-response sensor if needed
Monitor AF burden regularly; if persistent AF develops, consider VVI mode conversion
Program appropriate lower rate limit (60-70 bpm in awake, higher during sleep if needed)
Avoid unnecessary ventricular pacing; use threshold testing to confirm lead capture
CIED Complications & Management
Lead-Related Complications
Complication
Incidence
Risk Factors
Management
Lead dislodgement
2.4% (most common)
Inexperienced operator, active patient, young age
Percutaneous repositioning or replacement; monitor for pacing loss
Lead perforation
0.3-0.7%
Thin RV wall, active motion, stiff leads
Urgent pericardiocentesis if tamponade; lead removal/replacement
Lead fracture
1-2%
Subclavian approach, crush injury, lead age >10 years
New lead placement; remove broken lead if high risk
Insulation breakdown
0.5-1%
Manufacturing defect, extrinsic damage, age >7 years
Lead replacement; monitor for device recall
Infection
Class I, Evidence A Antibiotic prophylaxis required within 1 hour of skin incision (cefazolin 1-2g IV preferred). Device-related bacteremia/endocarditis necessitates early device removal (Class I, Evidence A) with consideration for reimplantation after IV antibiotic course (typically 2-4 weeks).
Frequency: 2.1-9.5% (usually manageable). Most hematomas resolve with pressure and immobilization. Consider reversal of anticoagulation if INR >2 or consider bridging strategy pre-implant. Evacuation needed if hematoma expands or signs of infection.
Tricuspid Regurgitation (TR)
CIED leads may induce or worsen TR, especially with apical RV lead placement. RV pacing duration and lead type associated. No preventive lead selection established. Monitor TR progression on serial echos if hemodynamically significant.
Pitfall: Delayed recognition of lead dislodgement—patient may develop loss of capture or sensing acutely. Always assess 12-lead ECG post-implant for QRS morphology baseline and compare at follow-up visits.
MRI-Conditional Devices & Imaging Safety
MRI-Conditional Pacemakers & ICDs
Class I, Evidence A MRI-conditional devices (labeled as such by manufacturer) are safe during 1.5T or 3T MRI scanning if manufacturer-specific programming conditions are followed (e.g., programmer in-room, specific coil selection, pacemaker-dependent patients require monitoring).
Non-MRI-Conditional Devices
Class IIa, Evidence B If MRI necessary in non-conditional device patients, consider alternatives first (ultrasound, CT). If MRI unavoidable, high-risk protocol with cardiology/EP monitoring, magnet deactivation, and post-procedure interrogation required.
Alternative Imaging
Class IIa, Evidence B Epicardial leads present contraindication to MRI (ferromagnetic heating risk). Consider CT angiography or ultrasound as alternatives.
Leadless pacing: Class IIb, Evidence C. Leadless pacers (no transvenous lead) eliminate ferromagnetic lead concerns, making MRI safer; however, limited long-term data on device longevity and specific MRI protocols still emerging.
Age alone not contraindication to pacing. Symptomatic bradycardia in octogenarians with adequate functional status warrants pacing (Class I). Dual-chamber preferred over single-chamber for SND preservation of AV synchrony. Minimize unnecessary interventions; shared decision-making essential.
Congenital Heart Disease (CHD)
Class I, Evidence C Pacing indicated if anatomic/congenital abnormalities warrant (e.g., 3° AVB post-surgical repair, complex Tetralogy of Fallot). Lead positioning challenging; epicardial leads often required. Multidisciplinary team approach recommended.
Neuromuscular Diseases
Myotonic Dystrophy:Class I, Evidence C Pacing for AVB. High risk of arrhythmias; ICD preferred if LV dysfunction or family history of sudden cardiac death.
Duchenne/Becker Muscular Dystrophy:Class IIb, Evidence C Pacing for conduction disease in context of cardiomyopathy.
Emery-Dreifuss: High sudden death risk; ICD preferred over PM if LVEF <40%.
Pregnancy
Pacing may be necessary or deferred based on maternal/fetal risk assessment. No routine indication changes but timing/approach differs. Device implantation preferred in second trimester if urgent. Remote monitoring recommended to minimize fluoroscopy during pregnancy.
Hypertrophic Cardiomyopathy (HCM)
Class IIb, Evidence B AV sequential pacing with short AV delay (70-100 ms) may reduce LV outflow tract gradient in select symptomatic HCM patients refractory to medical therapy. ICD preferred if high sudden death risk.
Long QT Syndrome (LQTS)
ICD generally preferred over pacemaker for primary prevention. High-dose beta-blocker + genetic counseling essential. Pacing may reduce torsades burden in select cases but insufficient evidence for Class I recommendation.
Pearl: Neuromuscular disease patients often have conduction system disease progression. Baseline ECG + periodic ECG monitoring recommended; escalate to ICD if LVEF declines or arrhythmias develop despite pacing.
Continue warfarin (target INR 2-3); delay bridging anticoagulation if INR >2. Continue DOAC without interruption if possible (if not, restart immediately post-implant). Continue aspirin monotherapy without interruption. Heparin bridging use limited unless high-risk (mechanical valve, recent VTE).
In-Office Follow-up Schedule
Device Type
First Follow-up
Routine Interval
Single/dual-chamber PM
2-12 weeks post-implant
≥12 months (Class IIa, Evidence A)
CRT-P/HBP
2-4 weeks post-implant
Every 6 months (Class I, Evidence C)
ICD
2-12 weeks post-implant
3-6 months (device/clinical factors)
Remote Device Monitoring
Class I, Evidence A Recommended for patients with difficulty attending in-office visits or device recalls. Enables real-time transmission of arrhythmia detection, lead/battery status, and alerts.
Battery End-of-Life (EOL) Assessment
Elective replacement indicator (ERI): When reached, schedule generator change within 2-4 weeks
This quick reference summarizes key recommendations from the 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy.
For complete details, refer to the full guideline: 10.1093/eurheartj/ehab364
Last Updated: March 2026 | For Medical Professionals Only