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Device-Based Therapy
Diagnosis and Treatment
Diagnosis and Treatment
Pacing
Permanent Pacing in Sinus Node Dysfunction (SND)
Key Points
- SND refers to a broad array of abnormalities in sinus node and atrial impulse formation and propagation.
- These include persistent sinus bradycardia and chronotropic incompetence without identifiable causes, paroxysmal or persistent sinus arrest with replacement by subsidiary escape rhythms in the atrium, atrioventricular (AV) junction, or ventricular myocardium.
- The frequent association of paroxysmal atrial fibrillation (AF) and sinus bradycardia or sinus bradyarrhythmias, which may oscillate suddenly from one to the other, usually accompanied by symptoms, is termed "tachy-brady syndrome."
- SND is primarily a disease of the elderly and is presumed to be due to senescence of the sinus node and atrial muscle.
- The clinical manifestations of SND are diverse, reflecting the range of typical sinoatrial rhythm disturbances.
- The most dramatic presentation is syncope.
- However, in many patients, the clinical manifestations of SND are more insidious and relate to an inadequate heart rate response to activities of daily living that can be difficult to diagnose.
- The term "chronotropic incompetence" is used to denote an inadequate heart rate response to physical activity.
- No single metric has been established as a diagnostic standard upon which therapeutic decisions can be based.
- The only effective treatment for symptomatic bradycardia is permanent cardiac pacing.
- The optimal pacing system for prevention of symptomatic bradycardia in SND is unknown.
Treatment
minimally symptomatic patients with chronic heart rate <40 bpm while awake. ( C , IIb )
Permanent pacemaker implantation is NOT indicated for SND:
Figure 1. Sinus Node Dysfunction
Acquired Atrioventricular (AV) Block in Adults
Key Points
- Patients with abnormalities of AV conduction may be asymptomatic or may experience serious symptoms related to bradycardia, ventricular arrhythmias, or both.
- AV block can sometimes be provoked by exercise.
- Type I second-degree AV block is characterized by progressive prolongation of the PR interval before a nonconducted beat and a shorter PR interval after the blocked beat.
- Type I second-degree AV block is usually due to delay in the AV node irrespective of QRS width.
Because progression to advanced AV block in this situation is uncommon, pacing is usually not indicated unless the patient is symptomatic.
- Type II second-degree AV block is characterized by fixed PR intervals before and after blocked beats and is usually associated with a wide QRS complex.
- Type II second-degree AV block is usually infranodal (either intra- or infra-His), especially when the QRS is wide.
In these patients, symptoms are frequent, prognosis is compromised, and progression to third-degree AV block is common and sudden. Thus, type II second-degree AV block with a wide QRS typically indicates diffuse conduction system disease and constitutes an indication for pacing even in the absence of symptoms.
- When AV conduction occurs in a 2:1 pattern, block cannot be classified unequivocally as type I or type II, although the width of the QRS can be suggestive.
- Advanced second-degree AV block refers to the blocking of ≥2 consecutive P waves with some conducted beats, which indicates some preservation of AV conduction.
In the setting of AF, a prolonged pause (eg, >5 seconds) should be considered to be due to advanced second-degree AV block.
- Third-degree AV block (complete heart block) is defined as absence of AV conduction.
- In a patient with third-degree AV block, permanent pacing should be strongly considered even when the ventricular rate is >40 bpm, because the choice of a 40 bpm cutoff in these guidelines was not determined from clinical trial data.
Indeed, it is not the escape rate that is necessarily critical for safety but rather the site of origin of the escape rhythm (ie, in the AV node, the His bundle, or infra-His).
Treatment
Permanent Pacing in Chronic Bifascicular Block
Key Points
- Bifascicular block refers to ECG evidence of impaired conduction below the AV node in the right and left bundles.
Alternating bundle-branch block (also known as bilateral bundle-branch block) refers to situations in which clear ECGbranch block) refers to situations in which clear ECGbranch block) refers to situations in which clear ECGbranch block) refers to situations in which clear ECGbranch block) refers to situations in which clear ECG evidence for block in all 3 fascicles is manifested on successive ECGs.
- Patients with first-degree AV block in association with bifascicular block and symptomatic, advanced AV block have a high mortality rate and a substantial incidence of sudden death.
- Syncope is common in patients with bifascicular block, but it is not associated with an increased incidence of sudden death.
Therefore, pacing relieves the neurological symptoms but does not reduce the occurrence of sudden death.
- Ventricular arrhythmias are common in patients with bifascicular block.
Treatment
Permanent Pacing After the Acute Phase of Myocardial Infarction (MI)
Key Points
- Indications for permanent pacing after MI in patients experiencing AV block are related in large measure to the presence of intraventricular conduction defects.
- The criteria for patients with MI and AV block do not necessarily depend on the presence of symptoms. Furthermore, the requirement for temporary pacing in acute myocardial infarction (AMI) does not by itself constitute an indication for permanent pacing.
Treatment
persistent second- or third-degree AV block at the AV node level, even in the absence of symptoms.
( B , IIb )Permanent Pacing in Hypersensitive Carotid Sinus Syndrome and Neurocardiogenic Syncope
Key Points
- The hypersensitive carotid sinus syndrome is defined as syncope or presyncope resulting from an extreme reflex response to carotid sinus stimulation. There are 2 components of the reflex:
- Cardioinhibitory, which results from increased parasympathetic tone and is manifested by slowing of the sinus rate or prolongation of the PR interval and advanced AV block, alone or in combination.
- Vasodepressor, which is secondary to a reduction in sympathetic activity that results in loss of vascular tone and hypotension.
This effect is independent of heart rate changes.
- Hyperactive response to carotid sinus stimulation is defined as asystole due to either sinus arrest or AV block of >3 seconds, a substantial symptomatic decrease in systolic blood pressure, or both.
- Permanent pacing for patients with an excessive cardioinhibitory response to carotid stimulation is effective in relieving symptoms.
- Because 10%-20% of patients with this syndrome may have an important vasodepressive component of their reflex response, it is desirable that this component be defined before one concludes that all symptoms are related to asystole alone.
Among patients whose reflex response includes both cardioinhibitory and vasodepressive components, attention to the latter is essential for effective therapy in patients undergoing pacing.
Treatment
for recurrent syncope caused by spontaneously occurring carotid sinus stimulation and carotid sinus pressure that induces ventricular asystole of >3 seconds. ( C , I )
syncope without clear, provocative events and with a hypersensitive cardioinhibitory response of ≥3 seconds. ( C , IIa )
significantly symptomatic neurocardiogenic syncope associated with bradycardia documented spontaneously or at the time of tilt-table testing. ( B , IIb )
Permanent pacing is NOT indicated for:
Pacing After Cardiac Transplantation
Key Points
- The incidence of bradyarrhythmias after cardiac transplantation varies from 8% to 23%.
Treatment
persistent inappropriate or symptomatic bradycardia not expected to resolve and for other Class I indications for permanent pacing. ( C , I )
Permanent pacing may be considered:
Permanent Pacemakers That Automatically Detect and Pace to Terminate Tachycardias
Treatment
symptomatic recurrent supraventricular tachycardia (SVT) that is reproducibly terminated by pacing when catheter ablation and/or drugs fail to control the arrhythmia or produce intolerable side effects. ( C , IIa )
in the presence of an accessory pathway that has the capacity for rapid anterograde conduction. ( C , III (harm) )
Pacing to Prevent Tachycardia
Treatment
sustained pause-dependent VT, with or without QT prolongation. ( C , I )
high-risk patients with congenital long-QT syndrome. ( C , IIa )
prevention of symptomatic, drug-refractory, recurrent AF in patients with coexisting SND. ( B , IIb )
Permanent pacing is NOT indicated for:
Pacing to Prevent Atrial Fibrillation
Treatment
The prevention of AF in patients without any other indication for pacemaker implantation. ( B , III (harm) )
Cardiac Resynchronization Therapy (CRT)
Key Points
- Progression of LV systolic dysfunction to clinical HF is frequently accompanied by impaired electromechanical coupling, which may further diminish effective ventricular contractility.
- The most common disruptions are prolonged AV (first-degree AV block) and prolonged interventricular conduction, most commonly left bundle-branch block (LBBB).
- Prolonged interventricular and intraventricular conduction causes regional mechanical delay within the left ventricle that can result in reduced ventricular systolic function, altered myocardial metabolism, functional mitral regurgitation, and adverse remodeling with ventricular dilatation.
- Prolongation of the QRS duration occurs in approximately one-third of patients with advanced HF and has been associated with ventricular electromechanical delay ("dyssynchrony").
- QRS duration and dyssynchrony both have been identified as predictors of worsening HF, sudden cardiac death (SCD), and total death.
- Modification of ventricular electromechanical delay with multisite ventricular pacing (commonly called "biventricular pacing" or CRT) can improve ventricular systolic function, reduce metabolic costs, ameliorate functional mitral regurgitation, and, in some patients, induce favorable remodeling with reduction of cardiac chamber dimensions.
Treatment
CRT is indicated for:
patients who have left ventricular ejection fraction (LVEF) ≤35%, sinus rhythm, LBBB with a QRS duration ≥150 ms, and NYHA class II, III, or ambulatory IV; symptoms on guideline-directed medical therapy (GDMT).
- the patient requires ventricular pacing or otherwise meets CRT criteria and
- AV nodal ablation or pharmacologic rate control will allow near 100% ventricular pacing with CRT
CRT may be considered for patients who have:
CRT is NOT recommended for patients:
Pacing in Patients With Hypertrophic Cardiomyopathy (HCM)
Treatment
- SND or AV block in patients with HCM as described previously (See "Permanent Pacing in Sinus Node Dysfunction" And "Acquired Atrioventricular Block in Adults").
- in medically refractory symptomatic patients with HCM and significant resting or provoked LV outflow tract obstruction.
Permanent pacemaker implantation is NOT indicated for:
Permanent Pacing in Children, Adolescents, and Patients With Congenital Heart Disease
Key Points
- symptomatic sinus bradycardia
- the bradycardia-tachycardia syndromes
- advanced second- or third-degree AV block, either congenital or postsurgical.
Treatment
Permanent pacemaker implantation is reasonable for:
Permanent pacemaker implantation is NOT indicated for:
transient postoperative AV block with return of normal AV conduction in the otherwise asymptomatic patient.
( C , III (no benefit) )asymptomatic bifascicular block with or without first-degree AV block after surgery for congenital heart disease in the absence of prior transient complete AV block.
( C , III (no benefit) )asymptomatic type I second-degree AV block.
( C , III (no benefit) )asymptomatic sinus bradycardia with the longest relative risk interval <3 seconds and a minimum heart rate >40 bpm.
( C , III (no benefit) )Implantable Cardioverter-Defibrillator (ICD)
Key Points
- The options for management of patients with ventricular arrhythmias include antiarrhythmic agents, catheter ablation, and surgery.
- Patient selection, device and lead implantation, follow-up, and replacement are parts of a complex process that requires familiarity with device capabilities, adequate case volume, continuing education, and skill in the management of ventricular arrhythmias, thus mandating appropriate training and credentialing.
Treatment
ICD therapy is indicated in patients:
Pediatric Patients and Patients With Congenital Heart Disease
Catheter ablation or surgical repair may offer possible alternatives in carefully selected patients.
for patients with congenital heart disease with recurrent syncope of undetermined origin in the presence of either ventricular dysfunction or inducible ventricular arrhythmias at electrophysiological study. ( B , IIa )
for patients with recurrent syncope associated with complex congenital heart disease and advanced systemic ventricular dysfunction when thorough invasive and noninvasive investigations have failed to define a cause. ( C , IIb )
Table 1. Minimum Frequency of Cardiovascular Implantable Electronic Devices (CIEDs) In-Person or Remote Monitoringa
Type and Frequency | Method |
---|---|
Pacemaker/ICD/CRT | |
Within 72 h of CIED implantation | In person |
2-12 wk postimplantation | In person |
Every 3-12 mo for pacemarker/CRT-Pacemaker | In person or remote |
Every 3-6 mo for ICD/CRT-D | In person or remote |
Annually until battery depletion | In person |
Every 1-3 mo at signs of battery depletion | In person or remote |
Implantable loop recorder | |
Every 1-6 mo depending on patient symptoms and indication | In person or remote |
Implantable hemodynamic monitor | |
Every 1-6 mo depending on indication | In person or remote |
More frequent assessment as clinically indicated | In person or remote |
Modified from Wilkoff B et al. Heart Rhythm 2008;5(6):907–25.
Figure 2. Indications for Cardiac Resychronization Therapy
Table 2. Choice of Pacemaker Generator in Selected Indications for Pacing
Pacemaker Generator | Sinus Node Dysfunction | Atrioventricular Block | Neurally Mediated Syncope or Carotid Sinus Hypersensitivity |
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Single-chamber atrial pacemaker |
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Single-chamber ventricular pacemaker |
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Dual-chamber pacemaker |
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Single-lead, atrial-sensing ventricular pacemaker |
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