Cardiovascular

Bradyarrhythmias and pacemaker indications

Clinical Overview and When to Suspect Bradyarrhythmia

— Sinus node dysfunction (SND): sinus bradycardia, sinus pauses, sinoatrial exit block, tachy-brady syndrome, chronotropic incompetence

— AV conduction disease: 1st-degree, Mobitz I (Wenckebach), Mobitz II, high-grade (2:1, 3:1), and complete (3rd-degree) AV block

— Conduction system disease: bifascicular/trifascicular block, alternating bundle branch block

— Syncope or near-syncope, especially without prodrome (suggests Stokes-Adams)

— Fatigue, exertional intolerance, dyspnea out of proportion to comorbidities → think chronotropic incompetence

— Falls in the elderly with unexplained mechanism

— New CHF symptoms in a patient with known conduction disease (loss of AV synchrony)

— Patient on rate-slowing meds (β-blocker, diltiazem, verapamil, digoxin, ivabradine, donepezil) with new symptoms

Definition: Resting heart rate <60 bpm with symptoms, or <50 bpm regardless of symptoms in clinically relevant settings. The Step 3 task is rarely "is this bradycardia?" — it is "is this bradycardia pathologic, and does this patient need a pacemaker?"

Pathophysiologic buckets:

When to suspect in clinic:

Reversible causes to rule out first (the "DIVISIONS" mental model): Drugs, Ischemia (especially inferior MI → AV nodal ischemia from RCA), Vagal tone, Infection (Lyme, endocarditis with abscess), Sleep apnea, Intracranial pressure (Cushing reflex), Oxygen/hypoxia, Neurologic (autonomic), Systemic — hypothyroidism, hypothermia, hyperkalemia

Step 3 management: Before pacemaker referral, always document that the bradyarrhythmia is symptomatic AND irreversible. Pacing for transient causes (drug toxicity, Lyme carditis, acute inferior MI in first 7–10 days) is generally inappropriate.

Board pearl: Asymptomatic sinus bradycardia in a trained athlete (HR 35–45) is normal — no workup, no pacemaker. Symptoms drive intervention in SND.

Presentation Patterns and Key History

— Sick sinus syndrome (SSS): elderly patient with alternating palpitations (AF/atrial tachycardia) and fatigue/dizziness/syncope (bradycardia/pauses) → tachy-brady syndrome. Often unmasked when rate control is started for AF.

— Complete heart block: abrupt syncope without warning ("drop attack"), recovers spontaneously, no postictal state. ECG: AV dissociation with ventricular escape.

— Carotid sinus hypersensitivity: syncope while shaving, turning head, or with tight collar. Pause >3 sec or SBP drop >50 mmHg with carotid massage.

— Neurocardiogenic (vasovagal): prodrome of nausea, diaphoresis, tunneling vision after standing/pain/fear; not a pacemaker indication in most cases.

— Trigger pattern: positional, post-prandial, with micturition/defecation/cough → reflex-mediated

— Medication review (highest yield): β-blockers including ophthalmic timolol, non-DHP CCBs, digoxin, amiodarone, sotalol, dofetilide, ivabradine, clonidine, donepezil/rivastigmine, lithium

— Recent illness: tick exposure (Lyme), travel (Chagas), febrile illness with new conduction disease (endocarditis with aortic root abscess → AV block)

— Cardiac history: prior MI (especially inferior), cardiac surgery (post-op AV block), TAVR (high rate of new LBBB/AV block), infiltrative disease (sarcoid, amyloid)

— Sleep history: witnessed apneas, snoring → OSA-mediated nocturnal bradycardia

— Family history: sudden death, congenital heart block, Lamin A/C cardiomyopathy (conduction disease + DCM)

Classic syndromes to recognize on the stem:

History essentials to extract:

Board pearl: Syncope with injury (facial laceration, fracture) in an elderly patient strongly favors a cardiac etiology over vasovagal — pursue ECG, echo, and ambulatory monitoring aggressively.

Key distinction: Pre-syncope with prodrome and recovery in seconds = reflex. Sudden syncope without warning = arrhythmic until proven otherwise.

Physical Exam Findings and Hemodynamic Assessment

— Palpate radial and auscultate apex simultaneously — pulse deficit suggests AF with variable conduction or frequent ectopy

— Orthostatics to exclude volume/autonomic contribution

— Document HR response to standing, exercise (chronotropic incompetence: failure to reach 80% of age-predicted max = 0.8 × [220−age])

— Cannon A waves in the JVP — atrial contraction against closed tricuspid during AV dissociation

— Variable intensity of S1 (changing PR relationship)

— Variable systolic BP beat-to-beat

— Wide pulse pressure if ventricular escape is slow with augmented stroke volume

— Carotid sinus massage (after auscultating for bruits, no recent TIA/stroke/MI): pause >3 sec or symptomatic = carotid sinus hypersensitivity

— Valsalva lowers HR via vagal tone — exaggerated response suggests SND

— Exercise (walk in hallway): inadequate HR rise → chronotropic incompetence

— Signs of poor perfusion: altered mental status, cool/mottled extremities, hypotension (SBP <90), chest pain, acute CHF, ischemic ECG changes → unstable bradycardia, proceed to ACLS algorithm

— Stable bradycardia with adequate perfusion → time to investigate cause

Vital signs and rhythm assessment:

Findings specific to complete (3rd-degree) AV block:

Mobitz I (Wenckebach): group beating on pulse palpation — clusters of beats followed by a pause; usually benign, vagally mediated

Mobitz II / high-grade block: regular dropped beats; concerning, often infranodal

Maneuvers at bedside:

Hemodynamic assessment in acute bradycardia:

CCS pearl: In a CCS case of symptomatic bradycardia, your first orders should be: continuous cardiac monitor, IV access, 12-lead ECG, pulse oximetry, BMP/Mg, TSH, troponin, and place transcutaneous pacer pads even before deciding on atropine vs. transvenous pacing — pad placement is "free" preparation.

Board pearl: Cannon A waves + variable S1 + bradycardia = 3rd-degree AV block until proven otherwise.

Diagnostic Workup — Initial Labs, ECG, and Biomarkers

— Sinus bradycardia: P before every QRS, normal axis P (upright I, II, aVF)

— Sinus pause/arrest: absent P-QRS-T; if pause is multiple of P-P interval, suspect SA exit block

— 1st-degree AVB: PR >200 ms, every P conducts

— Mobitz I: progressive PR prolongation → dropped QRS, then resets; usually narrow QRS (AV nodal)

— Mobitz II: fixed PR, sudden dropped QRS, often wide QRS (infranodal — His-Purkinje)

— 2:1 AVB: ambiguous — look at neighboring conduction, QRS width, response to atropine/exercise

— 3rd-degree AVB: AV dissociation with atrial rate > ventricular rate; junctional escape (narrow, 40–60) vs ventricular escape (wide, 20–40)

— Narrow QRS escape, responds to atropine → AV nodal (often reversible, often inferior MI)

— Wide QRS escape, no atropine response → infranodal → pacemaker indicated

— BMP (K, Ca, Mg), magnesium, TSH, troponin, CBC

— Consider digoxin level, drug screen if applicable

— Lyme serology in endemic areas with new high-grade AVB in young patient

— In suspected infiltrative disease: SPEP/free light chains (amyloid), ACE level (low yield for sarcoid)

— Elevated troponin → consider ischemic etiology, get coronary evaluation

— Hyperkalemia ECG: peaked T, then PR prolongation, then wide QRS, then sine wave — treat before assuming primary conduction disease

— TTE for structural disease, EF, valvular vegetation/abscess

— CXR to exclude alternative cause of syncope/dyspnea

12-lead ECG (always first): define the rhythm precisely

Localize the block:

Initial labs:

Biomarker logic:

Imaging at presentation:

Step 3 management: A young patient with new AVB and a recent rash/arthralgia in the Northeast US → send Lyme serology, start IV ceftriaxone, hold off on permanent pacemaker — Lyme carditis resolves with treatment.

Board pearl: Wide-QRS escape in 3rd-degree AVB = infranodal disease = unstable = permanent pacemaker.

Diagnostic Workup — Advanced and Confirmatory Studies

— 24–48 hr Holter: symptoms daily

— 14–30 day event/patch monitor (Zio): symptoms weekly to monthly

— 30-day external loop recorder: intermittent symptoms with prodrome

— Implantable loop recorder (ILR, Reveal LINQ): unexplained syncope with negative initial workup, especially with structural heart disease — monitors up to 3 years. Class I for recurrent unexplained syncope.

— Diagnoses chronotropic incompetence (HR fails to reach 80% predicted max)

— Useful when symptoms are exertional

— Can unmask exercise-induced AV block (often infranodal → pacemaker)

— Indicated when noninvasive testing is non-diagnostic but suspicion for conduction disease remains high

— Measures HV interval: HV >70 ms abnormal, HV >100 ms or block below His with pacing = pacemaker indication

— Useful in bifascicular block + syncope when ambulatory monitoring is unrevealing

Ambulatory rhythm monitoring — choose by symptom frequency:

Exercise stress testing:

Tilt-table testing: for suspected vasovagal/neurocardiogenic syncope when diagnosis unclear; not indicated if cardiac syncope is suspected

Electrophysiology (EP) study:

Cardiac MRI: suspected infiltrative disease (sarcoidosis with patchy late gadolinium enhancement, amyloid with diffuse subendocardial LGE) — particularly in young patients with unexplained AVB

FDG-PET: confirms cardiac sarcoid; bradyarrhythmia + young/middle-aged patient + nonischemic CM is a classic stem

Polysomnography: nocturnal bradycardia/pauses on monitor, especially during sleep → rule out OSA

Coronary angiography: if ischemic etiology suspected, particularly inferior MI presenting with AV block

Key distinction: Holter vs ILR — match the device duration to symptom frequency. Daily symptoms = Holter. Once-every-few-months syncope = ILR.

Board pearl: Bifascicular block + syncope + negative Holter = EP study or ILR, do not stop the workup.

Risk Stratification and Management Logic

1. Are symptoms attributable to the bradyarrhythmia?

2. Is the cause reversible?

— Symptomatic SND (sinus bradycardia, pauses, chronotropic incompetence) when symptom-rhythm correlation established

— Symptomatic Mobitz I (uncommon, usually benign)

— Mobitz II, regardless of symptoms

— High-grade AVB (2:1 with bundle branch block, advanced AVB)

— 3rd-degree AVB, acquired, non-reversible

— Permanent AF with symptomatic bradycardia or pauses >5 sec

— Alternating bundle branch block

— Post-AV node ablation for refractory AF/SVT

— Syncope + bifascicular block + HV >70 ms or block below His on EP

— Asymptomatic Mobitz II with narrow QRS

— Atropine 1 mg IV q3–5 min, max 3 mg (first line)

— If no response or AV block with wide QRS: transcutaneous pacing + sedation, OR dopamine 5–20 mcg/kg/min OR epinephrine 2–10 mcg/min

— Refractory: transvenous pacing

— Atropine often ineffective in infranodal block and may worsen it (paradoxically slows escape) — go to pacing

Two questions drive all decisions:

If symptomatic AND irreversible → permanent pacemaker

If symptomatic AND reversible (drug, ischemia, Lyme, electrolyte, hypothyroid) → treat the cause, reassess; consider temporary pacing as bridge

If asymptomatic → pacemaker only if the rhythm itself confers prognostic risk (advanced AVB, long pauses on monitor)

Pacemaker indications — Class I (memorize):

Class IIa (reasonable):

Acute unstable bradycardia (ACLS algorithm):

CCS pearl: For unstable bradycardia in CCS, order in this sequence: cardiac monitor → IV → O2 → atropine → pacer pads → transcutaneous pacing with sedation → cardiology consult for transvenous/permanent pacing.

Board pearl: Mobitz II and 3rd-degree AVB → never rely on atropine alone — proceed to pacing.

Pharmacotherapy — Acute and Bridging Agents

— Mechanism: vagolytic, accelerates SA node firing and AV conduction

— Effective for vagally mediated bradycardia, sinus bradycardia, and AV nodal (Mobitz I) block

— Avoid/ineffective in: infranodal block (Mobitz II, complete AVB with wide escape), post–cardiac transplant (denervated heart — use isoproterenol or epinephrine)

— May paradoxically worsen high-grade AVB by speeding sinus rate without conducting → 2:1 or higher block

— Dopamine 5–20 mcg/kg/min IV — easy to titrate; β1 stimulation increases HR and contractility; useful when atropine fails

— Epinephrine 2–10 mcg/min IV — preferred in shock or when β-blocker/CCB toxicity overlaps

— Isoproterenol — pure β-agonist, classic for torsades prophylaxis and complete heart block in transplant heart, less commonly stocked

— β-blocker overdose: glucagon 3–10 mg IV bolus then infusion; high-dose insulin/euglycemia therapy; IV calcium; lipid emulsion for lipophilic agents (propranolol)

— Calcium channel blocker overdose: IV calcium gluconate/chloride, glucagon, high-dose insulin (1 unit/kg bolus then 0.5–1 unit/kg/hr with dextrose), vasopressors

— Digoxin toxicity (bradycardia, AV block, regularized AF, hyperkalemia, yellow vision): digoxin immune Fab (DigiFab) for hemodynamic instability, K >5, dig level >10–15 ng/mL, or ingestion >10 mg

— Hyperkalemia: IV calcium for membrane stabilization, insulin/D50, albuterol, then potassium removal (diuresis, kayexalate/patiromer, dialysis)

— All AV nodal blockers, ophthalmic β-blockers, donepezil if temporally related

Atropine 1 mg IV bolus, repeat q3–5 min up to 3 mg total:

Beta-agonists (chronotropic infusions):

Specific antidotes/reversal:

Drugs to discontinue/hold:

Step 3 management: When a nursing home patient on donepezil + metoprolol + diltiazem presents with new symptomatic bradycardia, hold all three first before reaching for pacing decisions — polypharmacy is the most common reversible cause in the elderly.

Board pearl: Transplanted heart is denervated → atropine does not work → use isoproterenol or epinephrine.

Pacemaker Selection, Implantation, and Procedural Management

— Position 1: chamber paced (A/V/D/O)

— Position 2: chamber sensed (A/V/D/O)

— Position 3: response (I=inhibit, T=trigger, D=dual, O=none)

— Position 4: R = rate-responsive

— SND with intact AV conduction: AAIR or DDDR with minimized RV pacing (managed ventricular pacing algorithm) — avoid unnecessary RV pacing (causes pacing-induced cardiomyopathy)

— AV block: DDD(R) — maintains AV synchrony

— Permanent AF + AV block: VVIR (no atria to track)

— Carotid sinus hypersensitivity, vasovagal with cardioinhibitory component: DDD with rate-drop response

— LV dysfunction (EF ≤35%) requiring >40% ventricular pacing: CRT (biventricular) pacemaker — Class I in HF with LBBB QRS ≥150 ms

— Indication for ICD coexists (e.g., EF ≤35%, ischemic >40 days post-MI): CRT-D or dual-chamber ICD

— Ideal for: limited vascular access, prior device infection, high infection risk (dialysis), permanent AF needing ventricular pacing only

— Pre-op: hold anticoagulation per device (uninterrupted warfarin INR <3 is safer than bridging with heparin — BRUISE CONTROL trial); DOACs typically held 24–48 hr

— Antibiotic prophylaxis: cefazolin 1 hr pre-incision

— Post-implant: CXR to confirm lead position and exclude pneumothorax; device check

Pacemaker nomenclature (NBG code) — first 3 letters:

Device selection by indication:

Leadless pacemakers (Micra): single-chamber VVI(R), implanted in RV via femoral approach

Procedural management:

Acute complications: pneumothorax (1–2%), hematoma, lead dislodgement (first 24–48 hr — restrict ipsilateral arm above shoulder ×4–6 weeks), cardiac perforation/tamponade, infection

CCS pearl: After implant, order CXR, device interrogation, restrict arm elevation, continue antibiotics if directed, schedule 1-week wound check and 2–4 week device check.

Board pearl: Minimize RV pacing in SND — chronic high-burden RV pacing causes dyssynchrony and HF.

Special Populations — Elderly and Renal/Hepatic Impairment

— Most common indications: SND and acquired complete AVB from age-related fibrosis (Lev disease — fibrocalcific degeneration of cardiac skeleton) and Lenègre disease (idiopathic conduction system fibrosis)

— Polypharmacy review is paramount — eye drops with β-blockers, donepezil/rivastigmine, rate-control meds for AF

— Falls workup: orthostatics, gait, vision, medications — bradyarrhythmia is one bucket

— Frailty assessment before device implantation — discuss goals of care; leadless pacemaker may be preferable for limited life expectancy or recurrent infection risk

— Pacemaker syndrome (VVI pacing without AV synchrony): fatigue, dyspnea, neck pulsations (cannon A waves), hypotension → upgrade to dual-chamber

— Hyperkalemia is a common, reversible cause of bradycardia/AV block in CKD/ESRD — always check K+ first

— Dialysis patients have elevated infection risk → consider leadless pacemaker; avoid subclavian vein access on AV fistula side

— Contrast use during EP/device procedures: minimize in CKD stage 4–5; venography for lead placement uses small volumes

— Affects metabolism of β-blockers (propranolol, metoprolol), amiodarone, verapamil — bradycardia risk increased; dose-reduce or avoid

— Coagulopathy increases pocket hematoma risk — correct INR <1.5 pre-procedure if possible

— AVB after TAVR is common (especially with self-expanding valves like Evolut, and pre-existing RBBB) — monitor ≥48 hr post-procedure; permanent pacemaker if persistent high-grade AVB

— Post-surgical AVB after valve replacement: wait 5–7 days before permanent pacing (may recover); after isolated CABG, AVB rarely persistent

Elderly (highest pacemaker prevalence):

Renal impairment:

Hepatic impairment:

Post-cardiac surgery patients:

Step 3 management: Elderly patient on ophthalmic timolol presenting with syncope and HR 38 — stop the drops, do not implant immediately; recheck rhythm after washout.

Board pearl: Post-TAVR new persistent LBBB + PR prolongation → high risk for delayed complete AVB → close monitoring or prophylactic pacing.

Special Populations — Pregnancy, Pediatrics, and Athletes

— Physiologic resting HR rises 10–20 bpm; true bradycardia is uncommon and warrants workup

— Causes: supine hypotensive syndrome (positional, IVC compression — left lateral decubitus), congenital AVB, prior repaired CHD

— Pacemaker implantation during pregnancy: feasible, ideally after 8 weeks, use echocardiographic or electroanatomic mapping guidance to minimize fluoroscopy; lead shielding for fetus

— Maternal complete AVB with stable escape and asymptomatic — close monitoring may suffice; delivery planning multidisciplinary

— Associated with maternal anti-Ro/SSA and anti-La/SSB antibodies (neonatal lupus) — screen mother

— Indications for pediatric pacing: symptoms, wide-QRS escape, ventricular rate <55 (or <70 with CHD), prolonged QTc, ventricular dysfunction, complex ventricular ectopy

— Congenital heart disease post-repair (TGA, AVSD, tetralogy) — AVB common after VSD closure

— Epicardial leads in small children; transvenous after sufficient growth

— Long-term lead management: extraction, generator changes over decades — favor MRI-conditional systems

— Resting sinus bradycardia 30s–40s, sinus arrhythmia, 1st-degree AVB, Wenckebach during sleep are normal adaptations

— Concerning: symptoms with exertion, Mobitz II, complete AVB, pauses >3 sec while awake

— Detraining trial can clarify before invasive workup in equivocal cases

— AVB in patient <60 with no other cause → CMR/FDG-PET → if confirmed, immunosuppression (steroids) AND device (often ICD given arrhythmic risk, not just pacemaker)

— Family history of sudden death + conduction disease + DCM → consider ICD even at higher EF than usual cutoffs

Pregnancy:

Congenital complete AV block:

Pediatric/young adult considerations:

Athletes:

Cardiac sarcoidosis (often young/middle-aged):

Lamin A/C cardiomyopathy:

Board pearl: Young patient with new high-grade AVB → think sarcoid, Lyme, Lamin A/C, congenital, or myocarditis — get CMR, Lyme serology, family history.

Key distinction: Athlete's heart vs pathologic bradycardia — symptoms and exercise response are the dividing line.

Complications and Adverse Outcomes

— Syncope with injury (head trauma, fractures, MVC)

— Sudden cardiac death in advanced AVB with unreliable escape

— Cerebral hypoperfusion → cognitive decline, falls in elderly

— Heart failure exacerbation from loss of AV synchrony and inadequate cardiac output

— Atrial fibrillation in SND (tachy-brady cycle)

— Thromboembolism in tachy-brady syndrome with paroxysmal AF (CHA2DS2-VASc applies)

— Early (≤30 days): pneumothorax, hemothorax, hematoma, lead dislodgement, cardiac perforation/tamponade, infection

— Late: lead fracture, insulation breach, exit block (rising thresholds), Twiddler syndrome (patient manipulates generator causing lead displacement), venous thrombosis/stenosis

— Pacemaker syndrome: VVI pacing in patient with intact retrograde conduction → atria contract against closed AV valves → cannon waves, fatigue, hypotension; treat by upgrading to dual-chamber

— Pacing-induced cardiomyopathy: chronic high-burden RV pacing (>40%) causes dyssynchrony, drop in EF; upgrade to CRT

— Pocket infection / endocarditis: any device infection → complete system extraction + IV antibiotics 4–6 weeks (longer for endocarditis); re-implant on contralateral side after sterile blood cultures

— Lead-related TR: mechanical interference with tricuspid leaflet

— Pacemaker-mediated tachycardia (PMT): endless-loop tachycardia in dual-chamber devices with retrograde VA conduction — treated by magnet application or reprogramming PVARP

— Runaway pacemaker: rare, generator malfunction → very rapid pacing

From bradyarrhythmia itself:

Pacemaker-related complications:

Special pacemaker syndromes:

CCS pearl: Suspected pacemaker pocket infection (erythema, drainage, fever) → blood cultures ×2 + TEE (lead vegetations) + ID and EP consults + plan for complete device extraction, not just antibiotics.

Board pearl: Fever + bacteremia + pacemaker = device infection until proven otherwise; antibiotic suppression alone fails — extract the system.

When to Escalate Care — ICU, Consult, Inpatient Triage

— Hemodynamic instability: SBP <90, altered mentation, ischemic chest pain, acute pulmonary edema

— Mobitz II or 3rd-degree AVB in any context

— Symptomatic pauses >3 sec while awake

— Bradycardia in setting of acute MI, particularly anterior MI with new AVB (signals large infarct — anterior MI + new AVB carries higher mortality than inferior + AVB)

— Drug toxicity with refractory bradycardia (β-blocker, CCB, digoxin)

— Post-cardiac surgery or post-TAVR persistent high-grade AVB

— Stable symptomatic SND awaiting EP consultation

— Stable 1st-degree AVB or Mobitz I with concerning features

— Drug-induced bradycardia improving with med hold

— Asymptomatic sinus bradycardia in otherwise well patient

— 1st-degree AVB, asymptomatic Mobitz I (especially nocturnal)

— Resolved single episode of syncope with normal ECG, normal exam, and low-risk profile (young, no structural heart disease, prodrome)

— Cardiology/EP: all suspected pacemaker indications

— ID: suspected device infection or endocarditis

— Cardiac surgery: in case of perforation, lead extraction with risk for tear

— Cardiothoracic anesthesia: complex extractions

— Sleep medicine: nocturnal pauses, suspected OSA

— Rheumatology: suspected sarcoid or autoimmune myocarditis

— Need for transvenous pacing at facility without cath lab → arrange transfer with transcutaneous pacing in place, IV chronotrope, escort with ACLS capability

Immediate ICU admission with telemetry/cardiology consult:

Stepdown/telemetry floor:

Outpatient workup acceptable:

Consults to order:

Transfer criteria:

Step 3 management: For any unstable bradycardia at a facility without EP capability, place transcutaneous pacer pads and start a chronotrope before initiating transfer — do not transport a patient relying solely on atropine.

CCS pearl: "Change location" to ICU when ordering transvenous pacing or any inotrope/chronotrope drip.

Key Differentials — Same-Category (Bradyarrhythmia Mimics and Variants)

— Sinus bradycardia: P precedes every QRS, normal axis P, regular rhythm → physiologic vs SND

— Sinus arrhythmia: rate varies with respiration, normal in young — not pathologic

— SA exit block: missed P-QRS where the pause = exact multiple of P-P interval (e.g., 2× P-P) → SA node fires but signal blocked from leaving

— Sinus arrest: pause not a multiple of P-P → SA node fails to fire

— Junctional escape rhythm: narrow QRS at 40–60, absent or retrograde (inverted) P waves — emerges when SA fails

— Ventricular escape: wide QRS at 20–40, AV dissociation if 3rd-degree block

— Ectopic atrial bradycardia: abnormal P morphology, slow rate

— Mobitz I (Wenckebach): progressive PR lengthening, eventual dropped QRS, increment decreases with each beat, RR intervals shorten before drop — AV nodal, usually narrow QRS, often vagal/drug, atropine helps

— Mobitz II: fixed PR intervals before dropped beat, often wide QRS — infranodal, unpredictable progression to complete block, pacemaker indicated

— 2:1 AVB: cannot label as I or II from rhythm strip alone — assess QRS width, response to atropine/exercise, EP study if needed

— High-grade AVB: ≥2 consecutive non-conducted P waves with some conducted

— 3rd-degree AVB: complete AV dissociation, atrial rate > ventricular rate

— Often iatrogenic (rate-control meds) — different from bradyarrhythmia with sinus rhythm

— Regularized AF on digoxin → think digoxin toxicity with junctional escape

Within the bradyarrhythmia family, sort by P-QRS relationship:

AV block tiers (most common Step 3 trap is Mobitz I vs II):

AF with slow ventricular response:

Board pearl: Mobitz I shortens the RR interval just before the dropped beat (because each PR increment is smaller than the prior) — a classic test trick.

Key distinction: Mobitz II = wide QRS, fixed PR, pacemaker. Mobitz I = narrow QRS, lengthening PR, watch.

Key Differentials — Other-Category Causes of Syncope/Bradycardia

— Vasovagal: prodrome of nausea, warmth, tunnel vision; triggers include prolonged standing, pain, fear, blood draw; recovery quick; not a pacemaker indication except in older patients with recurrent severe cardioinhibitory subtype documented on tilt or ILR

— Situational: cough, micturition, defecation, swallow

— Carotid sinus hypersensitivity: older men, head turning/shaving; carotid massage diagnostic

— Volume depletion, autonomic failure (Parkinson, MSA, diabetic autonomic neuropathy), medications (α-blockers, diuretics, TCAs)

— Distinguished by orthostatic vitals; HR usually rises (unless concurrent autonomic failure)

— VT/VF — wide complex tachycardia, syncope without prodrome; consider ICD

— Aortic stenosis — exertional syncope, systolic ejection murmur, pulsus parvus et tardus

— HOCM — young athlete, syncope with exertion, dynamic outflow murmur

— Pulmonary embolism, pulmonary hypertension — exertional syncope, hypoxia

— Seizure (postictal state, tongue bite, urinary incontinence, witnessed convulsion)

— Vertebrobasilar TIA (rare, focal neurologic deficits)

— Subclavian steal

— Hypothyroidism, myxedema — bradycardia, hyporeflexia, hypothermia

— Hypothermia — Osborn (J) waves on ECG

— Hyperkalemia — bradycardia with classic ECG progression

— Hypoglycemia — usually with diaphoresis, altered mentation

— Lyme carditis — high-grade AVB in endemic area, recent erythema migrans

— Endocarditis with aortic root abscess — fever, new AVB, valvular regurgitation

— Acute rheumatic fever — prolonged PR is a minor Jones criterion

— Viral myocarditis — bradycardia uncommon but can occur with conduction system involvement

Reflex (neurally mediated) syncope:

Orthostatic hypotension:

Cardiac syncope mimics not from bradycardia:

Neurologic mimics:

Metabolic/endocrine mimics:

Infectious/inflammatory:

Board pearl: Young patient + fever + new heart block = think endocarditis with aortic root abscess → TEE immediately, surgical consult.

Secondary Prevention, Discharge Medications, Long-Term Plan

— Activity restriction: no ipsilateral arm abduction above shoulder ×4–6 weeks (prevents lead dislodgement); no heavy lifting >10 lbs; no driving for 1 week (private) or per state law

— Wound care: keep dry ×48 hr, no submersion ×2 weeks; watch for redness/drainage/fever

— Antibiotic prophylaxis for dental work: NOT indicated for pacemaker alone (unlike prosthetic valves)

— Medication reconciliation: discontinue unnecessary AV nodal blockers; continue indicated β-blockers (e.g., post-MI, HFrEF) — pacing enables appropriate β-blocker use

— GDMT: ACEi/ARB/ARNI, β-blocker, MRA, SGLT2 inhibitor

— Consider CRT upgrade if RV pacing burden >40% and EF declines

— Private driver after pacemaker: typically 1 week if asymptomatic

— Commercial: 4 weeks

— After syncope due to bradycardia, before pacing: avoid driving until rhythm controlled

— Most modern devices are MRI-conditional — verify model; non-conditional devices require risk/benefit assessment, often feasible at experienced centers

— In-person device check at 2–6 weeks post-implant

— Then every 3–12 months in-person or via remote monitoring (preferred — reduces clinic visits, detects arrhythmias and lead issues earlier; reimbursed under value-based care)

— Pacemaker deactivation is ethically permissible at patient/surrogate request; not considered physician-assisted death

— Pacemakers do not typically prolong dying for pacemaker-independent patients; ICDs more often deactivated to prevent shocks at end of life

After permanent pacemaker implantation — discharge orders:

Anticoagulation if AF coexists: apply CHA2DS2-VASc; pacing does not reduce stroke risk, even with successful rhythm control

Heart failure optimization if applicable:

Driving recommendations (AHA/HRS):

MRI compatibility:

Device monitoring schedule:

End-of-life and device deactivation:

Step 3 management: At every follow-up, review battery longevity (usually 6–12 yr), threshold trends, and AF burden — escalate if AF burden ≥6 min predicts stroke risk (anticoagulate per CHA2DS2-VASc).

Follow-Up, Monitoring, and Counseling

— Wound check: 1–2 weeks post-implant

— First device interrogation: 2–6 weeks (programming optimization)

— Routine in-person check: every 6–12 months

— Remote monitoring: every 3 months (detects lead issues, arrhythmias, battery status, AF burden)

— End-of-life replacement: when battery indicator triggers (elective replacement indicator → 3-month window before mandatory replacement)

— Pacing thresholds (rising threshold suggests exit block or lead issue)

— Sensing amplitudes

— Lead impedance (sudden drop = insulation breach; sudden rise = fracture)

— Percent atrial/ventricular pacing (high RV pacing burden flag)

— AF/atrial high-rate episode burden

— Battery longevity estimate

— Electromagnetic interference: safe with microwaves, cell phones (keep >6 inches from device); avoid prolonged contact with strong magnets; airport security generally safe (request hand wand if concerned)

— MRI: confirm device is conditional; provide device ID card

— Diathermy and arc welding: avoid

— TENS units, lithotripsy, electrosurgery: require precautions

— Symptoms requiring urgent attention: syncope/near-syncope, persistent palpitations, hiccupping in time with heartbeat (diaphragmatic pacing from lead displacement), fever, wound drainage

— Indicated if underlying ischemic disease, post-MI, post-CABG, HF, or significant deconditioning

— Improves functional capacity and reduces re-hospitalization

— Treat OSA if present

— Maintain hydration in vasovagal-prone patients

— Avoid medications that exacerbate bradycardia without clinical benefit

Pacemaker clinic cadence:

What to monitor at each visit:

Patient counseling — common concerns:

Cardiac rehabilitation:

Driving counseling: revisit based on indication and symptom recurrence

Lifestyle:

CCS pearl: Schedule device clinic follow-up at 2 weeks, primary care follow-up at 1 month, and cardiology at 3 months — overlapping appointments minimize transition-of-care gaps.

Board pearl: AF burden ≥6 minutes on pacemaker interrogation in patient with CHA2DS2-VASc ≥2 → strongly consider anticoagulation.

Ethical, Legal, and Patient Safety Considerations

— Discuss alternatives: pharmacologic temporizing, no intervention with palliative focus, leadless vs transvenous

— Risks: pneumothorax, hematoma, infection, lead complications, future extraction, lifestyle restrictions, MRI considerations

— Document capacity, especially in elderly or post-syncope patient with concern for cognitive impairment

— Surrogate decision-making when patient lacks capacity — follow advance directive, durable POA for healthcare, then surrogate hierarchy by state law

— Patient with decision-making capacity (or surrogate per advance directive) may request deactivation of a pacemaker; this is ethically and legally equivalent to withdrawing other life-sustaining treatment

— Not euthanasia or physician-assisted death

— Multidisciplinary discussion (cardiology, palliative care, ethics if needed) before deactivation

— ICDs more commonly deactivated to prevent painful shocks; pacemakers in pacemaker-dependent patients are more nuanced

— Physicians must counsel patients about state-specific driving restrictions after syncope or pacemaker implant; document the conversation

— Some states have mandatory reporting of impaired drivers — know your jurisdiction

— Discharge handoff to PCP within 1 week, cardiology/EP within 2–4 weeks

— Medication reconciliation: explicitly stop bradycardia-causing meds that prompted admission

— Provide device identification card and remote monitoring setup before discharge

— Confirm patient has support for wound care and activity restrictions

— Lead dislodgement from premature arm use → patient education effectiveness measure

— Pocket infection → surgical site infection bundle adherence

— Failure to identify reversible cause before implantation (overuse measure)

— Insurance coverage varies; leadless devices and CRT have prior authorization barriers

— Advocate for appropriate device based on indication, not formulary

Informed consent for pacemaker implantation:

Device deactivation at end of life:

Driving and public safety:

Transitions of care (Step 3 high-yield):

Patient safety events to track:

Equity and access:

Step 3 management: Document symptom-rhythm correlation, reversible cause exclusion, and informed consent in the chart — these three elements protect both patient and clinician medicolegally.

High-Yield Associations and Rapid-Fire Clinical Facts

— Cannon A waves + variable S1 + bradycardia → 3rd-degree AVB

— Erythema migrans + new AVB in summer in Connecticut → Lyme carditis (IV ceftriaxone, no pacemaker)

— Fever + new murmur + new heart block → aortic root abscess from endocarditis

— Young patient + nonischemic CM + AVB → cardiac sarcoidosis (CMR, FDG-PET)

— Yellow vision + bradycardia + regularized AF + hyperkalemia → digoxin toxicity (DigiFab)

— Peaked T waves + wide QRS + bradycardia → hyperkalemia (IV calcium first)

— Syncope while shaving → carotid sinus hypersensitivity

— Group beating on pulse → Wenckebach

— Tachy-brady syndrome + AF in elderly → sick sinus syndrome

— New LBBB + AVB after TAVR → conduction system injury → permanent pacemaker

— Family history of sudden death + DCM + AVB → Lamin A/C cardiomyopathy (ICD)

— Inferior STEMI + AVB → RCA occlusion, often transient, observe (don't rush to permanent pacing)

— Anterior STEMI + new AVB → large infarct, septal damage, worse prognosis, often needs pacing

— Osborn waves + bradycardia → hypothermia

— Pause = multiple of P-P → SA exit block

— Donepezil, rivastigmine (cholinesterase inhibitors)

— Ophthalmic timolol (often missed in med rec)

— Ivabradine (selective HCN inhibitor)

— Clonidine

— Lithium (sinus node depression)

— HR <50 in symptomatic patient = pacing consideration

— Pause >3 sec awake or >5 sec in AF = abnormal

— HV interval >70 ms abnormal, >100 ms or block below His with pacing = pacemaker

— AF burden ≥6 min on device = stroke risk signal

— Atropine max dose 3 mg

— RV pacing burden >40% with EF ≤35% = consider CRT

Buzzwords → diagnosis:

Drug-bradycardia pairings:

Numbers to memorize:

Board pearl: "Mobitz II or 3rd-degree → pacemaker" — the most testable single sentence in this topic.

Board Question Stem Patterns

— 78-year-old with syncope, HR 32, BP 88/50, ECG shows AV dissociation with wide QRS escape at 30

— Answer: transcutaneous pacing → transvenous pacing → permanent pacemaker (NOT atropine — won't work in infranodal block)

— 60-year-old with chest pain, ST elevation in II/III/aVF, complete AVB with narrow escape at 50, hemodynamically stable

— Answer: reperfusion (PCI), atropine if symptomatic, observe — usually resolves within days; no permanent pacemaker initially

— 28-year-old hiker in Vermont, EM rash 2 weeks ago, new syncope, ECG complete AVB

— Answer: IV ceftriaxone × 14–21 days, temporary pacing if symptomatic, no permanent pacemaker — resolves

— 75-year-old with intermittent palpitations and fatigue, Holter shows AF alternating with sinus pauses 4 sec

— Answer: permanent dual-chamber pacemaker (DDDR) + anticoagulation per CHA2DS2-VASc

— 70-year-old man with syncope while shaving, carotid massage → 5-sec pause

— Answer: dual-chamber pacemaker (DDD with rate-drop response)

— Elderly on metoprolol + diltiazem + donepezil with syncope, HR 38

— Answer: hold offending agents, observe; pacemaker only if persistent after washout

— RBBB + LAFB + unexplained syncope, Holter unrevealing

— Answer: EP study (HV interval) or ILR; pacemaker if HV >70 ms or recurrent symptomatic bradyarrhythmia captured

— Patient with VVI pacer reports new fatigue, neck pulsations, near-syncope

— Answer: upgrade to dual-chamber (DDD)

— New persistent LBBB + PR prolongation 48 hr after TAVR

— Answer: continued telemetry; permanent pacemaker if high-grade AVB persists

— 45-year-old, new AVB, no CAD on cath, CMR shows patchy LGE

— Answer: steroids + ICD (not just pacemaker)

Pattern 1 — Wide-complex 3rd-degree AVB in elderly:

Pattern 2 — Inferior MI with AVB:

Pattern 3 — Lyme carditis:

Pattern 4 — Sick sinus syndrome:

Pattern 5 — Carotid sinus hypersensitivity:

Pattern 6 — Drug-induced bradycardia:

Pattern 7 — Bifascicular block + syncope:

Pattern 8 — Pacemaker syndrome:

Pattern 9 — Post-TAVR AVB:

Pattern 10 — Cardiac sarcoid:

Board pearl: When the stem describes a reversible cause (Lyme, ischemia, drug, electrolyte), the correct answer is treat the cause, not implant a pacemaker.

One-Line Recap

Bradyarrhythmias warrant permanent pacing when they are symptomatic and irreversible, with Mobitz II and third-degree AV block as nearly automatic indications regardless of symptoms.

Symptom-rhythm correlation + exclusion of reversible causes (drugs, ischemia, Lyme, electrolytes, hypothyroid, OSA) must be documented before any permanent pacemaker implantation.

Atropine works at the AV node; for infranodal block (wide-QRS escape, Mobitz II, complete AVB with wide escape), go directly to transcutaneous → transvenous → permanent pacing, and remember atropine is ineffective in the denervated transplant heart.

Device selection follows indication: DDD(R) for AV block, AAIR/DDD with minimized RV pacing for SND, VVIR or leadless for permanent AF with bradycardia, CRT when EF ≤35% and high RV pacing burden or LBBB ≥150 ms.

Step 3 priorities — outpatient management: anticoagulate based on CHA2DS2-VASc when AF burden ≥6 min on device, schedule remote monitoring every 3 months, counsel on driving and EMI, recognize device infection requires complete system extraction (not antibiotic suppression), and remember pacemaker deactivation at end of life is ethically permissible and not euthanasia.

Highest-yield one-liners: Mobitz II = pacemaker; 3rd-degree AVB = pacemaker; inferior MI AVB = usually transient; anterior MI AVB = ominous; Lyme AVB = ceftriaxone, no device; sarcoid AVB = steroids + ICD; tachy-brady AF = pacemaker + anticoagulation; donepezil + β-blocker + CCB in elderly with syncope = stop the drugs first.

CCS pearl: Order set for unstable bradycardia — monitor, IV, O2, ECG, BMP/Mg/TSH/troponin, atropine, pacer pads, transcutaneous pacing with sedation, cardiology consult, ICU transfer.