Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ 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... Your Access profile is currently affiliated with [InstitutionA] and is in the process of switching affiliations to [InstitutionB]. Please select how you would like to proceed. Keep the current affiliation with [InstitutionA] and continue with the Access profile sign in process Switch affiliation to [InstitutionB] and continue with the Access profile sign in process Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Error: Incorrect UserName or Password Username Error: Please enter User Name Password Error: Please enter Password Sign in Forgot Password? Forgot Username? Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free profile for additional features.