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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • Cyclic heart rate variation with respiration

  • Nonrespiratory form may be related to sick sinus syndrome or digitalis intoxication

  • Variability of P-P cycle length at least 160 ms or 10% of the minimum cycle length

  • P-wave morphology identical to normal sinus rhythm

GENERAL CONSIDERATIONS

  • Sinus arrhythmia is seen in young patients or those treated with digitalis or morphine

  • It is rarely associated with increased intracranial pressure

  • The respiratory form is common in young people because of enhanced vagal tone

  • The respiratory form becomes less pronounced with advancing age and in autonomic dysfunction such as diabetes

  • The nonrespiratory form is seen in diseased hearts

  • Sinus arrhythmia with bradycardia can develop during recovery from acute illness or 2–3 days after inferior myocardial infarction

  • P-P intervals that contain a QRS complex are shorter than those that do not (ventriculophasic sinus arrhythmia); this may be secondary to vagal influence responding to changes in stroke volume

  • Loss of sinus rhythm variability is a marker for sudden cardiac death

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • Usually causes no symptoms

  • The nonrespiratory form with sick sinus syndrome may cause features of cerebral hypoperfusion such as lightheadedness

PHYSICAL EXAM FINDINGS

  • Normal exam in most patients

DIFFERENTIAL DIAGNOSIS

  • Sinoatrial exit block

  • Sinus pause

  • Nonconducted premature atrial beats

DIAGNOSTIC EVALUATION

LABORATORY TESTS

  • None required

ELECTROCARDIOGRAPHY

  • ECG with a rhythm strip to diagnose and document rhythm disorder

IMAGING STUDIES

  • Usually none required

DIAGNOSTIC PROCEDURES

  • Electrophysiology study not indicated

TREATMENT

CARDIOLOGY REFERRAL

  • Not required in most situations

HOSPITALIZATION CRITERIA

  • Not required in most situations

MEDICATIONS

  • Treat underlying cause

  • Withdraw offending drug

THERAPEUTIC PROCEDURES

  • None required

SURGERY

  • None required

MONITORING

  • None required in the respiratory form

  • In nonrespiratory form, ECG monitoring in hospital may be useful

DIET AND ACTIVITY

  • General healthy lifestyle

ONGOING MANAGEMENT

FOLLOW-UP

  • Not required except for the nonrespiratory form

  • In the nonrespiratory form, patients should be reevaluated once there are symptoms of cerebral hypoperfusion

COMPLICATIONS

  • Usually none

PROGNOSIS

  • Very good

RESOURCES

PRACTICE GUIDELINES

  • This is a benign arrhythmia

  • Reassurance may be needed in ...

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