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
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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
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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
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which therapeutic decisions can be based.
��The only effective treatment for symptomatic bradycardia is permanent
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cardiac pacing.
��The optimal pacing system for prevention of symptomatic bradycardia in
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SND is unknown.
Treatment
����Permanent pacemaker implantation is indicated for:
������ SND with documented symptomatic bradycardia, including frequent sinus pauses
that produce symptoms. (I-C)
������ symptomatic chronotropic incompetence. (I-C)
������ symptomatic sinus bradycardia that results from required drug therapy for medical
conditions. (I-C)
����Permanent pacemaker implantation is reasonable for:
������ SND with heart rate <40 bpm when a clear association between significant
symptoms consistent with bradycardia and the actual presence of bradycardia has
not been documented. (IIa-C)
������ syncope of unexplained origin when clinically significant abnormalities of sinus
node function are discovered or provoked in electrophysiological studies. (IIa-C)