Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ KEY FEATURES +++ ESSENTIALS OF DIAGNOSIS ++ Sinus rate is less than 60 bpm P waves have normal contour with a constant PR interval PR interval exceeds 120 ms Sinus arrhythmia often coexists +++ GENERAL CONSIDERATIONS ++ May be a manifestation of sick sinus syndrome High vagal tone (young adults and athletes) or medications (eg, beta blockers) are possible causes Increased intracranial pressure and myxedema are among several other causes Acute myocardial infarction (particularly inferior) is associated with sinus bradycardia Patients with anorexia nervosa may have sinus bradycardia Not uncommon in cardiac transplant recipients During sleep, the heart rate can fall to 35–40 bpm especially in young adults; pauses ≥ 2 seconds are not uncommon Hypothermia, severe hypoxia, coronary angiography, eye surgery, mediastinal tumors, and convalescence from infection are possible causes Obstructive jaundice is a possible cause Eye drops containing beta blockers are an easily overlooked cause Bradycardia after resuscitation from cardiac arrest carries a poor prognosis +++ CLINICAL PRESENTATION +++ SYMPTOMS AND SIGNS ++ Generally asymptomatic +++ PHYSICAL EXAM FINDINGS ++ Rarely causes hemodynamic decompensation in acute myocardial infarction +++ DIFFERENTIAL DIAGNOSIS ++ Ectopic atrial bradycardia +++ DIAGNOSTIC EVALUATION +++ LABORATORY TESTS ++ Depends on clinical situation Thyroid-stimulating hormone +++ ELECTROCARDIOGRAPHY ++ ECG to document rhythm Rhythm strip to define mechanism +++ IMAGING STUDIES ++ Usually none required +++ DIAGNOSTIC PROCEDURES ++ ECG and clinical examination are sufficient for diagnosis +++ TREATMENT +++ CARDIOLOGY REFERRAL ++ If part of sick sinus syndrome, referral to an electrophysiologist is required for evaluation of permanent pacemaker +++ HOSPITALIZATION CRITERIA ++ Does not require hospitalization by itself Hospitalization may be for concomitant illness +++ MEDICATIONS ++ Usually no specific treatment is needed If patients are symptomatic acutely, atropine may be used to increase the sinus rate Medications such as theophylline and ephedrine may be used cautiously without overshooting to sinus tachycardia +++ THERAPEUTIC PROCEDURES ++ Patients with recurrent symptoms are treated with a pacemaker +++ SURGERY ++ None required +++ MONITORING ++ ECG monitoring if hospitalized +++ DIET AND ACTIVITY ++ General healthy lifestyle +++ ONGOING MANAGEMENT +++ HOSPITAL DISCHARGE CRITERIA ++ Depends on concomitant illness +++ FOLLOW-UP ++ Usually none required except when symptoms are suggestive of sick sinus syndrome ++... Your MyAccess profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. 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 Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth