Summary

Comprehensive guideline on evaluation and management of adult patients (>18 years) with bradycardia and cardiac conduction delay, including sinus node dysfunction (SND), atrioventricular (AV) block, and intraventricular conduction disorders. Supersedes the 2008 device-based therapy guidelines and 2012 focused update. Emphasizes symptom-rhythm correlation for pacing decisions in SND, mandatory pacing for acquired Mobitz II/high-grade/third-degree AV block regardless of symptoms, screening for sleep apnea when nocturnal bradycardia is found, and use of more physiologic pacing (CRT, His bundle) when significant ventricular pacing is anticipated with LVEF 36-50%.

Key Recommendations

Permanent pacing for SND requires symptom-bradycardia correlation; no minimum heart rate or pause duration alone justifies pacing.
Acquired second-degree Mobitz II, high-grade, or third-degree AV block not from reversible/physiologic causes warrants permanent pacing regardless of symptoms.
Nocturnal bradycardia should prompt screening for sleep apnea and is not by itself an indication for permanent pacing.
Echocardiography is the appropriate initial test in patients with LBBB because of high likelihood of underlying structural heart disease and LV systolic dysfunction.
For atrial-based pacing in SND, atrial or dual-chamber pacing is preferred over single-chamber ventricular pacing to reduce AF and pacemaker syndrome.
In patients with LVEF 36-50% and AV block expected to require >40% ventricular pacing, use CRT or His bundle pacing rather than RV pacing to prevent heart failure.
Atropine 0.5-1 mg IV is first-line for acute symptomatic bradycardia from SND or AV nodal block; avoid in post-heart transplant patients (paradoxical block).
For beta-blocker or calcium channel blocker overdose, use IV calcium, glucagon, and high-dose insulin therapy; digoxin toxicity is treated with digoxin-specific Fab fragments.
Lyme carditis causing AV block is almost always reversible with antibiotics and rarely requires permanent pacing.
After TAVR with new persistent LBBB or high-grade AV block beyond 24-48 hours, careful surveillance and consideration of permanent pacing is warranted.
Alternating bundle branch block (LBBB and RBBB morphologies) warrants permanent pacing because of high risk of complete AV block.
Shared decision-making, including the right to refuse or withdraw pacemaker therapy even if pacemaker-dependent, is endorsed; withdrawal is not physician-assisted suicide.

Thresholds & Doses

Bradycardia definition: HR <60 bpm (NIH); guideline uses sinus rate <50 bpm and/or sinus pause >3 seconds for SND.
First-degree AV block: PR interval >200 ms; severe first-degree AV block (pseudo-pacemaker syndrome): PR >300 ms.
Bundle branch block: QRS duration ≥120 ms (complete); 110-119 ms (incomplete).
Chronotropic incompetence: failure to reach 80% of expected heart rate reserve (max HR = 220 - age).
Abnormal corrected sinus node recovery time (SNRT): >500-550 ms.
HV interval ≥70 ms predicts high-grade AV block in patients with myotonic dystrophy and bundle branch block.
Atropine: 0.5-1 mg IV, repeat every 3-5 min to max 3 mg.
Dopamine: 5-20 mcg/kg/min IV (start 5, titrate by 5 every 2 min).
Isoproterenol: 20-60 mcg IV bolus, then 10-20 mcg boluses or 1-20 mcg/min infusion.
Epinephrine: 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min.
Aminophylline: 250 mg IV bolus for AV block in acute inferior MI; 6 mg/kg in 100-200 mL over 20-30 min for post-transplant or spinal cord injury.
Theophylline: 300 mg IV then oral 5-10 mg/kg/d (target level 10-20 mcg/mL).
Calcium chloride 10%: 1-2 g IV every 10-20 min or infusion 0.2-0.4 mL/kg/h.
Calcium gluconate 10%: 3-6 g IV every 10-20 min or 0.6-1.2 mL/kg/h.
Glucagon: 3-10 mg IV bolus, then 3-5 mg/h infusion.
High-dose insulin: 1 unit/kg IV bolus, then 0.5 units/kg/h infusion.
Digoxin Fab: 1 vial (40 mg) binds ~0.5 mg digoxin; administer over ≥30 min.
Ventricular pacing burden cutoff for adverse remodeling: >40% (possibly as low as 20%).
Pacemaker implantation rates after valve surgery: mitral alone 3.5%, aortic alone 5.1%, tricuspid alone 12%, AV+MV 10%, MV+TV 16%, all three 25%.
Generally avoid permanent pacemaker implantation <72 hours after cardiac surgery or MI to allow conduction recovery; typically wait 5-7 days for CABG/MV, 3-5 days for AVR/TV.

Citations

Top 10 Take-Home Messages — overarching principles of bradycardia management
Section 2.2/Table 3 — definitions of SND, AV block grades, and conduction disorders
Section 5.4.4/Figure 6 — chronic SND management algorithm and pacing indications
Section 5.3.2/Table 8 — acute medical management drug doses for bradycardia
Section 6.4.4/Figure 7 — chronic AV block management algorithm
Section 6.4.4.1 — pacing mode selection and CRT/His bundle pacing for LVEF 36-50%
Section 4.2.7 — sleep apnea evaluation in nocturnal bradycardia
Section 8.1.2.4 — transcatheter aortic valve replacement conduction abnormalities
Section 11 and 14 — shared decision-making and end-of-life pacemaker management