Evaluation and Management of Patients with Bradycardia and Cardiac Conduction Delay

Publication Date: November 6, 2018

Key Points

Key Points

  • Sinus node dysfunction is most often related to age-dependent progressive fibrosis of the sinus nodal tissue and surrounding atrial myocardium leading to abnormalities of sinus node and atrial impulse formation and propagation and will therefore result in various bradycardic or pause-related syndromes.
  • Both sleep disorders of breathing and nocturnal bradycardias are relatively common, and treatment of sleep apnea not only reduces the frequency of these arrhythmias but also may offer cardiovascular benefits. The presence of nocturnal bradycardias should prompt consideration for screening for sleep apnea, beginning with solicitation of suspicious symptoms. However, nocturnal bradycardia is not in itself an indication for permanent pacing.
  • The presence of left bundle branch block on electrocardiogram markedly increases the likelihood of underlying structural heart disease and of diagnosing left ventricular systolic dysfunction. Echocardiography is usually the most appropriate initial screening test for structural heart disease, including left ventricular systolic dysfunction.
  • In sinus node dysfunction, there is no established minimum heart rate or pause duration where permanent pacing is recommended. Establishing temporal correlation between symptoms and bradycardia is important when determining whether permanent pacing is needed.
  • In patients with acquired second-degree Mobitz type II atrioventricular block, high-grade atrioventricular block, or third-degree atrioventricular block not caused by reversible or physiologic causes, permanent pacing is recommended regardless of symptoms. For all other types of atrioventricular block, in the absence of conditions associated with progressive atrioventricular conduction abnormalities, permanent pacing should generally be considered only in the presence of symptoms that correlate with atrioventricular block.
  • In patients with a left ventricular ejection fraction between 36% to 50% and atrioventricular block, who have an indication for permanent pacing and are expected to require ventricular pacing >40% of the time, techniques that provide more physiologic ventricular activation (e.g., cardiac resynchronization therapy, His bundle pacing) are preferred to right ventricular pacing to prevent heart failure.
  • Because conduction system abnormalities are common after transcatheter aortic valve replacement, recommendations on postprocedure surveillance and pacemaker implantation are made in this guideline.
  • In patients with bradycardia who have indications for pacemaker implantation, shared decision-making and patient-centered care are endorsed and emphasized in this guideline. Treatment decisions are based on the best available evidence and on the patient’s goals of care and preferences.
  • Using the principles of shared decision-making and informed consent/refusal, patients with decision-making capacity or his/her legally defined surrogate has the right to refuse or request withdrawal of pacemaker therapy, even if the patient is pacemaker dependent, which should be considered palliative, end-of-life care, and not physician-assisted suicide. However, any decision is complex, should involve all stakeholders, and will always be patient specific.
  • Identifying patient populations that will benefit the most from emerging pacing technologies (e.g., His bundle pacing, transcatheter leadless pacing systems) will require further investigation as these modalities are incorporated into clinical practice.

Definitions

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Term Definition or Description
Sinus node dysfunction (with accompanying symptoms)
  • Sinus bradycardia: Sinus rate <50 bpm
  • Ectopic atrial bradycardia: Atrial depolarization attributable to an atrial pacemaker other than the sinus node with a rate <50 bpm
  • Sinoatrial exit block: Evidence that blocked conduction between the sinus node and adjacent atrial tissue is present. Multiple electrocardiographic manifestations including “group beating” of atrial depolarization and sinus pauses.
  • Sinus pause: Sinus node depolarizes >3 s after the last atrial depolarization
  • Sinus node arrest: No evidence of sinus node depolarization
  • Tachycardia-bradycardia (“tachy-brady”) syndrome: Sinus bradycardia, ectopic atrial bradycardia, or sinus pause alternating with periods of abnormal atrial tachycardia, atrial flutter, or AF. The tachycardia may be associated with suppression of sinus node automaticity and a sinus pause of variable duration when the tachycardia terminates.
  • Chronotropic Incompetence: Broadly defined as the inability of the heart to increase its rate commensurate with increased activity or demand, in many studies translates to failure to attain 80% of expected heart rate reserve during exercise.
  • Isorhythmic dissociation: Atrial depolarization (from either the sinus node or ectopic atrial site) is slower than ventricular depolarization (from an atrioventricular nodal, His bundle, or ventricular site).
Atrioventricular block
  • First-degree atrioventricular block: P waves associated with 1:1 atrioventricular conduction and a PR interval >200 ms (this is more accurately defined as atrioventricular delay because no P waves are blocked)
  • Second-degree atrioventricular block: P waves with a constant rate (<100 bpm) where atrioventricular conduction is present but not 1:1
    • Mobitz type I: P waves with a constant rate (<100 bpm) with a periodic single nonconducted P wave associated with P waves before and after the nonconducted P wave with inconstant PR intervals
    • Mobitz type II: P waves with a constant rate (< 100 bpm) with a periodic single nonconducted P wave associated with other P waves before and after the nonconducted P wave with constant PR intervals (excluding 2:1 atrioventricular block)
    • 2:1 atrioventricular block: P waves with a constant rate (or near constant rate because of ventriculophasic sinus arrhythmia) rate (<100 bpm) where every other P wave conducts to the ventricles
    • Advanced, high-grade or high-degree atrioventricular block: ≥2 consecutive P waves at a constant physiologic rate that do not conduct to the ventricles with evidence for some atrioventricular conduction
  • Third-degree atrioventricular block (complete heart block): No evidence of atrioventricular conduction
  • Vagally mediated atrioventricular block: Any type of atrioventricular block mediated by heightened parasympathetic tone
  • Infranodal block: Atrioventricular conduction block where clinical evidence or electrophysiologic evidence suggests that the conduction block occurs distal to the atrioventricular node
Conduction tissue disease
  • RBBB (as defined in adults):
    • Complete RBB:
1. QRS duration ≥120 ms
2. rsr′, rsR′, rSR′, or rarely a qR in leads V1 or V2. The R′ or r′ deflection is usually wider than the initial R wave. In a minority of patients, a wide and often notched R wave pattern may be seen in lead V1 and/or V2.
3. S wave of greater duration than R wave or >40 ms in leads I and V6 in adults
4. Normal R peak time in leads V5 and V6 but >50 ms in lead V1
Incomplete RBBB: Same QRS morphology criteria as complete RBBB but with a QRS duration between 110 and 119 ms
  • LBBB (as defined in adults):
    • Complete LBBB:
1. QRS duration ≥120 ms in adults
2. Broad notched or slurred R wave in leads I, aVL, V5, and V6 and an occasional RS pattern in V5 and V6 attributed to displaced transition of QRS complex
3. Absent Q waves in leads I, V5, and V6, but in the lead aVL, a narrow Q wave may be present in the absence of myocardial pathology
4. R peak time >60 ms in leads V5 and V6 but normal in leads V1, V2, and V3, when small initial R waves can be discerned in the precordial leads
5. ST and T waves usually opposite in direction to QRS
    • Incomplete LBBB:
1. QRS duration between 110 and 119 ms in adults
2. Presence of left ventricular hypertrophy pattern
3. R peak time >60 ms in leads V4, V5, and V6
4. Absence of Q wave in leads I, V5, and V6
  • Nonspecific intraventricular conduction delay (as defined in adults): QRS duration
>110 ms where morphology criteria for RBBB or LBBB are not present
  • Left anterior fascicular block:
    • QRS duration <120 ms
    • Frontal plane axis between -45° and -90°
    • qR (small r, tall R) pattern in lead aVL
    • R-peak time in lead aVL of ≥45 ms
    • rS pattern (small r, deep S) in leads II, III, and aVF
  • Left posterior fascicular block: QRS duration <120 ms
    • Frontal plane axis between 90° and 180° in adults. Because of the more rightward axis in children up to 16 years of age, this criterion should only be applied to them when a distinct rightward change in axis is documented.
    • rS (small r, deep S) pattern in leads I and aVL
    • qR (small q, tall R) pattern in leads III and aVF
Maximum predicted heart rate for age calculated as 220 – age (y).

General Evaluation

4.1. History and Physical Examination of Patients With Documented or Suspected Bradycardia or Conduction Disorders

1. In patients with suspected bradycardia or conduction disorders a comprehensive history and physical examination should be performed. (I, C-EO)
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Noninvasive Evaluation

4.2.1. Electrocardiogram (ECG) in Patients With Documented or Suspected Bradycardia or Conduction Disorders

1. In patients with suspected bradycardia or conduction disorder, a 12-lead ECG is recommended to document rhythm, rate, and conduction, and to screen for structural heart disease or systemic illness. (I, B-NR)
573

Treatment

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...cise Electrocardiographic Testing i...

...ts with suspected chronotropic incompe...

...ients with exercise-related symptoms suspicious...

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...Rhythm MonitorsHaving trouble viewing table...

.... Cardiac Imaging in Bradycardia or Conduction Di...

...tients with newly identified LBBB, second-...

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...with bradycardia, laboratory tests (e.g., thyroid...

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...ts in whom a conduction disorder-causative...


...with inherited conduction disease, genetic c...

...eep Apnea Evaluation and Treatment in Pa...

...n patients with documented or suspected bradyca...

...ients with sleep-related bradycardi...

3. In patients who have previously rec...


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Bradycardia Attributable...

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5.4.3. Additional Testing of Bradycardi...

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...n patients who develop symptomatic s...

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2. In patients with LBBB who require pulm...

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3. In patients undergoing coronary artery bypas...

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...n patients undergoing surgery for AF who will li...

...3.1. Pacing After Aortic Valve Sur...

...patients undergoing surgical aortic valve...

.... In patients who have new postoperative SND or...

...ndergoing aortic valve surgery who will likely re...

....1.2.3.2. Pacing After Mitral V...

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...Pacing After Tricuspid Valve Surg...

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.... In patients with indications for perm...

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