In many individuals sinus bradycardia is asymptomatic. However, a few individuals will present with the following symptoms:

• Vague chest pain
• Dizziness or falling episodes
• Exercise intolerance
• Lightheadedness
• Dyspnea
• Vertigo
• Syncope

When obtaining a history in a patient with sinus bradycardia, one should obtain the following information to decipher the cause:

• Prior history of myocardial infarction
• Previous medical illness
• Any toxic exposure to chemicals
• Use of medications (eg beta blockers or calcium channel blockers)

• Fatigue

  (palpitations) When to see a doctor If you have lightheadedness, dizziness, fainting, fatigue, shortness of breath or palpitations, talk to your doctor. [mayoclinic.org]

  A 28-year-old man presented with progressive fatigue. Physical examination and ECG revealed severe sinus bradycardia. Echocardiography showed features of noncompaction cardiomyopathy and moderate aortic valve regurgitation. [ncbi.nlm.nih.gov]

  dizziness, and alternating periods of bradycardia and atrial tachycardia, which is caused by sinoatrial node dysfunction A constellation of signs and symptoms which may include syncope, fatigue, dizziness, and alternating periods of bradycardia and [icd9data.com]

• Fever

  Abstract INTRODUCTION Sinus tachycardia is widely recognized as one of the classic features of active rheumatic fever, but the fact that an abnormally slow heart rate is often present during the acute phase of this disease has received little emphasis [annals.org]

  […] myocardial infarct raised intra-cranial pressure drugs eg beta-blockers, digitalis, hypotensives rapid rise in blood pressure sinoatrial disease ('sick sinus syndrome') transient increase in vagal tone eg after vomiting physical training convalescence from fever [gpnotebook.co.uk]

  Bradycardia in the course of an influenza-like illness in endemic areas should suggest several pathogens such as legionella, Q fever or PUUV virus infection. [ncbi.nlm.nih.gov]

  Hantaan virus, found throughout northeastern Asia, causes a life-threatening illness known as hemorrhagic fever with renal syndrome (HFRS). [wwwnc.cdc.gov]

• Weakness

  She also reported nausea, diaphoresis, and weakness. Initial examination revealed that she was diaphoretic with pale skin and in mild respiratory distress. [journals.lww.com]

  […] bradycardia (FSB). mutations in the hyperpolarization-activated nucleotide-gated channel (HCN4) are known to be associated with FSB. three males of Moroccan Jewish descent were hospitalized: 1 survived an out-of-hospital cardiac arrest and 2 presented with weakness [ncbi.nlm.nih.gov]

• Surgical Procedure

  Approximately 121,000 bariatric surgical procedures are performed annually, and salutary effects include a reduction in cardiovascular morbidity and mortality, risk factor modification, and improvement in sympathovagal tone. [ncbi.nlm.nih.gov]

  Although pacemaker implantation is a relatively low-risk surgical procedure, like any operation, there is both risk and cost. Furthermore, persistent inappropriate right ventricular pacing may have harmful effects on heart function. [choosingwisely.org]

  Knowing if you have situs inversus is important if you undergo another surgical procedure. Situs inversus is a very rare birth defect in which some organs are atypically placed. [healthline.com]

• Collapse

  Can also result in syncope and collapse. [vetstream.com]

  […] chest pain or collapse. [patient.info]

  Heart block : When the heart beats more slowly, which may cause a person to collapse. Ventricular fibrillation : The heart has a disorganized rhythm that leads to loss of consciousness and death if not treated. [medicalnewstoday.com]

  […] very dizzy suddenly when standing up from a lying or sitting position – this is caused by having low blood pressure (hypotension) Third-degree heart block Symptoms of third-degree or complete heart block include: fainting – this can cause someone to collapse [nhs.uk]

• Dyspnea

  Immediately following the fourth dose of intravenous methylprednisolone, she developed dyspnea, chest heaviness, and lightheadedness. [ncbi.nlm.nih.gov]

  When symptoms arise they manifest as fatigue, dizziness and dyspnea on exertion (chronotropic incompetence). [healio.com]

  Symptomatic Bradycardia• If a patient can’t tolerate bradycardia, he may develop these signs and symptoms: – Hypotension – Cool, clammy skin – Altered mental status – Dizziness – Blurred vision – Crackles, dyspnea – Chest pain – Syncope 8. [slideshare.net]

• Jaundice

  Links: hypothyroidism hypothermia vomiting drug-induced bradycardia hypersensitive carotid sinus syndrome neurocardiogenic syndrome raised intracranial pressure jaundice [gpnotebook.co.uk]

  Abstract Obstructive jaundice is often listed among the causes of sinus bradycardia. The latter is usually attributed to the effect of bile salts on the sino-atrial node. [ncbi.nlm.nih.gov]

• Tachycardia

  In general, a heart rate of over 100 BPM is considered tachycardia. Sinus tachycardia can increase the risk of serious complications, including heart failure, stroke, or cardiac arrest. [leveluprn.com]

  […] rhythm His bundle tachycardia Idiojunctional tachycardia Idioventricular rhythm Inappropriate sinus tachycardia Inappropriate sinus tachycardia (rapid heart beat) Incessant atrial tachycardia Incisional tachycardia Labile pulse Left atrial incisional [icd9data.com]

  Interestingly, this patient also suffered from inappropriate sinus tachycardia due to autonomic involvement of multiple sclerosis. [ncbi.nlm.nih.gov]

  Typical sinus bradycardia [1] Sinus bradycardia is a heart disorder characterized by the sinus node firing at a slow ( Causes of sinus bradycardia include: Sick sinus syndrome ('brachy-tachy' syndrome) [2] associated with mitral dysplasia Atrial tachycardia [vetbook.org]

• Heart Disease

  […] of heart disease and issues with the heart’s neural signaling. [en.wikibooks.org]

  CONTINUE SCROLLING OR CLICK HERE FOR RELATED SLIDESHOW QUESTION In the U.S., 1 in every 4 deaths is caused by heart disease. See Answer [medicinenet.com]

  Etiology Sinus bradycardia has many intrinsic and extrinsic etiologies.[5]][6][7][8][9][10] Inherent Etiologies Chest trauma Ischemic heart disease Acute myocardial infarction Acute and chronic coronary artery disease Repair of congenital heart disease [ncbi.nlm.nih.gov]

  Common causes of bradycardia include: Congenital heart disease (i.e., condition you were born with) Certain side effects or heart medications The natural aging process Scar tissue from a heart attack Sick sinus syndrome, also called sinus node dysfunction [medtronic.com]

• Hypertension

  We present a case of a 76-year-old Japanese man with hypertension and multiple myeloma (MM) presented with syncope and sinus bradycardia. Thalidomide therapy for MM was added to longstanding atenolol therapy one month prior to presentation. [ncbi.nlm.nih.gov]

  The ECG above is from a 68 years-old woman with systemic hypertension and atrial fibrillation. [metealpaslan.com]

• Hypotension

  Within 24 h of receiving intravenous steroids, loperamide, and mesalamine, she developed symptomatic hypotension, severe sinus bradycardia, sinus pauses, and junctional escape beats. [ncbi.nlm.nih.gov]

  Causes: congenital hypothyroidism hypothermia post myocardial infarct raised intra-cranial pressure drugs eg beta-blockers, digitalis, hypotensives rapid rise in blood pressure sinoatrial disease ('sick sinus syndrome') transient increase in vagal tone [gpnotebook.co.uk]

• Slow Pulse

  Trained athletes are prone to bradycardia (slow pulses) with heart rates below 40 beats per minute common at rest. [rjmatthewsmd.com]

  Possible situations include: sinus bradycardia - where the abnormally slow pulse is the result of pacemaking from the sino-atrial node. [gpnotebook.com]

  Symptoms of SSS include: fainting or fainting sensations fatigue dizziness palpitations (abnormal heart beats) very slow pulse (bradycardia) difficulty breathing chest pain mental confusion memory problems disrupted sleep It’s important to see your doctor [healthline.com]

• Dermatitis

  ) blood disorders ( D56 - D76 ) contact dermatitis ( L23 - L25 ) dermatitis due to substances taken internally ( L27.- ) nephropathy ( N14.0- N14.2 ) Includes adverse effect of correct substance properly administered poisoning by overdose of substance [icd10data.com]

• Dizziness

  Following titration of thalidomide to a maximum dose of 400 mg/d, our patient's heart rate decreased markedly, resulting in intermittent symptoms of lightheadedness and dizziness. [ncbi.nlm.nih.gov]

  As a result, you may feel dizzy or have chronic lack of energy, shortness of breath, or even fainting spells. CAUSES Bradycardia can occur for several reasons. [medtronic.com]

  (palpitations) When to see a doctor If you have lightheadedness, dizziness, fainting, fatigue, shortness of breath or palpitations, talk to your doctor. [mayoclinic.org]

  PROBLEM – Prompt attention is critical – Can lead to more serious problems • Hypotension and dizziness • Ventricular tachycardia and ventricular fibrillation 7. [slideshare.net]

• Seizure

  Inappropriate Sinus Bradycardia Inappropriate Sinus Tachycardia can be caused by numerous factors, including: hypothermia, hypothyroidism, sick sinus syndrome), seizure and poisoning. [practicalclinicalskills.com]

  Roemheld syndrome Seizure. Sleep Diagnosis[edit] ECG characteristics Rate: Less than 60 beats per minute. Rhythm: Regular. P waves: Upright, consistent, and normal in morphology and duration. PR interval: Between 0.12 and 0.20 seconds in duration. [en.wikipedia.org]

• Asthenia

  Diagnosis Code R55 Syncope and collapse 2016 2017 2018 2019 Billable/Specific Code Applicable To Blackout Fainting Vasovagal attack Type 1 Excludes cardiogenic shock ( R57.0 ) carotid sinus syncope ( G90.01 ) heat syncope ( T67.1 ) neurocirculatory asthenia [icd10data.com]

Physical exam

The physical exam in a patient with sinus bradycardia is often unremarkable. Palpation of the peripheral pulses may indicate a slow but regular heart rate. Other features on a physical exam may include the following:

• Some patients may appear lethargic and drowsy. They may have difficulty getting up from a rested position.
• There may be bluish discoloration of skin and lips due to decreased perfusion (cyanosis).
• Peripheral edema may be present bilaterally, especially in the lower extremities.
• Auscultation may reveal crackles and rales.
• Mild to moderate dyspnea may be present at rest or from even the slightest exertion.

Laboratory studies

There is no specific laboratory study that has any definitive value in making the diagnosis of sinus bradycardia. The important thing is to order tests to exclude reversible causes of the disorder. When sinus bradycardia is suspected, levels of drugs like digoxin, lithium and electrolytes should be obtained. Other studies that may help depend on the clinical presentation and may include the following:

• Blood glucose levels
• Thyroid function tests
• Toxicological screen

Imaging 

Without any specific indication, the role of X-rays is limited in evaluating a patient with sinus bradycardia.

Electrocardiography

The diagnosis of sinus bradycardia is confirmed with a 12-lead ECG. The ECG will reveal a regular heart rate, with upright P waves and a QRS complex of less than 0.12 seconds.

Holter monitor

In individuals in whom the disorder is intermittent, the use of a holter monitor may help identify sinus bradycardia. The holter monitor is usually worn for 24 hours and records the electrical activity of the heart.

Event recorder

In the last decade, miniature devices have been developed which can be surgically inserted under local anesthesia. These devices can monitor electrical activity of the heart from a few weeks to few months. Once the diagnosis is made, these tiny devices can be removed under local anesthesia without any adverse effects.

Exercise stress test

In some patients an exercise stress test may be done to ensure that the heart rate does increase while walking on a treadmill or riding a stationary bike. The test can determine if the heart rate increase is appropriate to the physical activity.

• Torsades De Pointes

  Symptoms included syncope (n = 2), torsades de pointes (n = 7), and hemodynamic failure (n = 6). Three infants with 2:1 AVB died during the first month of life. [ncbi.nlm.nih.gov]

  Magnesium Magnesium is recommended for the treatment of torsades de pointes VT with or without cardiac arrest, but it has not been shown to be helpful for treatment of non-torsades pulseless arrest. [ahajournals.org]

  Immediate evaluation should focus on the ABCs: airway, breathing, and circulation (bedside echocardiogram). one more reason to fear bradycardia: torsade de pointes Torsade de pointes is a pause-dependent arrhythmia, which is more likely to occur at slower [emcrit.org]

  de pointes 心室細動 ventricular fibrillation ジギタリス不整脈 digitalis arrhythmia 心室不整脈 ventricular arrhythmia 心房不整脈 atrial arrhythmia QT延長症候群 long QT syndrome アンダースン症候群 Andersen's syndrome ジャーベル・ランゲ-ニールセン症候群 Jervell and Lange-Nielsen syndrome ロマノ･ワード症候群 Romano-Ward [jams.med.or.jp]

  Overall, therapy for bradycardia aims to (1) avoid asystole, (2) improve haemodynamic status, or (3) avoid tachycardia (e.g., in the setting of a prolonged QT interval with torsades de pointes). [cardiovascmed.ch]

• Prominent U Wave

  Note the prominent U waves in the precordial leads, a common finding in sinus bradycardia. [lifeinthefastlane.com]

  Note the prominent U waves in the precordial leads, a common finding in sinus bradycardia. Sinus node dysfunction (Sick sinus syndrome) Sinus arrhythmia Sinus tachycardia Advanced Reading Online Wiesbauer F, Kühn P. [litfl.com]

Emergency treatment

In many cases the patient has no symptoms and the finding of sinus bradycardia is made on a physical exam or an incidental ECG. If a patient with known sinus bradycardia is symptomatic and presents to the ED, then IV access should be obtained and the patient should be provided with oxygen. The patient should then be monitored. If the sinus bradycardia persist and is symptomatic, atropine may need to be administered intravenously. If the symptoms and bradycardia persists, transcutaneous pacing may be required in the ED [7].

Inpatient treatment

Once the patient’s condition has stabilized, the cause of bradycardia should be investigated. All unstable patients should be closely monitored and some may even require endotracheal intubation and transvenous pacing. These patients are best managed in the ICU [8][9].

When a patient is hemodynamically stable, the cause of sinus bradycardia can be worked up. Never send a symptomatic patient with sinus bradycardia for any tests like imaging without monitoring. A healthcare worker should accompany the patient in such scenarios.
The current guidelines state that in adult patients who have persistent sinus bradycardia with symptoms, cardiac pacing is recommended. In individuals with sinus bradycardia but no symptoms or with a reversible cause, pacing should be deferred.

In patients with sinus bradycardia due to drugs like beta blockers or digoxin, simple discontinuation of these agents is adequate. In some cases, a change in medications or reduction in dose may be beneficial. Some patients on digoxin may have an extended period of symptomatic bradycardia and these patients may benefit from temporary transvenous pacing and/or IV atropine.

In patients with post infectious bradycardia, recovery often takes a long time and in some cases may not occur. Permanent pacing is recommended in these individuals.

Patients with hypothermia who have sinus bradycardia should not be administered atropine because it can cause irritation of the myocardium and generation of ectopic beats. Rather, these patients fully recover with supportive treatment and rewarming measures. Sinus bradycardia is a common observation during open-heart surgery, esp. during the cooling process. If perfusion of organs remains normal, then no specific treatment is recommended. Those who develop inadequate organ perfusion may require atropine, pressor support and temporary pacing.

Patients with sleep apnea who develop sinus bradycardia usually require multifaceted treatment including weight loss, use of CPAP and rarely surgery.

In all patients with sinus bradycardia who are admitted to the hospital, it is important to have an intravenous line and a vial of atropine at the bedside, in case of an emergency. Once the patient’s condition has stabilized, he/she may be discharged and followed up a general practitioner.

Drug therapy

In general, sinus bradycardia is not treated with medications unless the patient has symptoms. In all symptomatic patients, any underlying electrolyte deficiency including hypoxia should be corrected. The drug of choice in symptomatic patients is atropine given intravenously. In the past, isoproterenol was frequently used to treat sinus bradycardia but its use has declined over the years because of adverse effects.

Pacing

If the cause of sinus bradycardia is felt to be temporary then one may utilize either transcutaneous or transvenous pacing. This can be done at the bedside and can help stabilize the symptomatic patient. If the cause is felt to be irreversible, then a permanent pacemaker should be inserted [10].

Permanent pacemakers are inserted by both cardiologists and cardiac surgeons. The procedure is performed under local anesthesia and use of fluoroscopy. The type of pacemaker inserted depends on the patient’s medical condition, age, comorbid conditions and cost.

The prognosis for patients with sinus bradycardia depends on the cause. Patients who develop the disorder after exposure to a drug or toxic chemical usually have a good prognosis if the offending agent is removed. Those patients who have a structural defect in the sinus node have a guarded prognosis and may require a pacemaker if they are symptomatic. Patients who develop sinus bradycardia after open-heart surgery or hypothermia generally have a good prognosis as they do tend to recover with time.

The causes of sinus bradycardia include the following:

• Sick sinus syndrome is perhaps one of the most common pathologic causes of symptomatic sinus bradycardia.
• Use of medications like beta blockers, digoxin, class 1 antiarrhythmic agents, amiodarone and calcium channel blockers.
• Bradycardia may also occur as a result of toxic exposure due to lithium, toluene, dimethyl sulfoxide, paclitaxel, topical acetylcholine, clonidine, and fentanyl.
• Systemic disorders like sleep apnea, hypothermia and hypoglycemia
• Rarely infections like rheumatic fever,diphtheria or viral myocarditis may be a cause of sinus bradycardia.
• Collagen vascular disorders like systemic lupus erythematosus, scleroderma or sarcoidosis.

Risk factors

The most significant factors for development of sinus bradycardia are advanced age, use of certain medications and open-heart surgery. Other risk factors that have been identified that increase the risk of bradycardia include:

• Chronic heavy alcohol use
• Hypertension
• Psychological stress
• Smoking
• Use of recreational drugs

The exact number of individuals with sinus bradycardia is not known because many who have no symptoms never come to medical attention. Data from cardiology clinics reveal that the frequency may be anywhere about 1 in 10,000 individuals. These numbers are under estimates [2].

Sinus bradycardia is not always pathological as it may be an incidental observation in young healthy adults or in those who are asleep. Most cases of sinus bradycardia are associated with an increase in vagal nerve activity. An increase in vagal tone is often a normal finding in well-conditioned athletes [3]. Pathological causes of sinus bradycardia include electrolyte deficiencies, inferior wall myocardial infarction, hypothyroidism, hypothermia, hypoglycemia, adverse drug effects, sepsis, sleep apnea [4] and elevated intracranial pressure (5).

Another very common cause of sinus bradycardia is due to an inability of the sinus node to generate an action potential in the atria. Also referred to as sick sinus syndrome, this disorder may present with symptoms related to under perfusion of the brain. In addition, sick sinus syndrome may present with alternating periods of tachycardia and bradycardia. Sick sinus syndrome is most common in elderly individuals who tend to have associated heart disease (6). The disorder has an unpredictable course with varied symptoms. Research in patients with sick sinus syndrome has revealed that some individuals have a quantitative decrease in sinus nodal neural cells and others have a variety of antinodal antibodies circulating in blood. Overall, the most cases of sick sinus syndrome are idiopathic.

It is very rare for sinus bradycardia to progress into heart block. Sudden death or cardiac arrest are rare events in people with sinus bradycardia.

To prevent sinus bradycardia one should avoid use of illicit agents, eat a healthy diet, exercise regularly and not smoke. Excessive alcohol consumption is not recommended.

When the resting heart rate is 60 beats per minute or less, it is defined as sinus bradycardia. Fortunately most patients do not develop symptoms until the heart rate drops to less than 45-50 beats per minute. In most cases, sinus bradycardia is diagnosed incidentally when evaluating a patient for some different disorder [1] [2].

Bradycardia is defined as a heart rate of under 60 beats per minute. In most cases, sinus bradycardia is diagnosed incidentally. Common symptoms are shortness of breath, lightheadedness, dizziness, vertigo, and syncope.

Prior to discharge the patient must be educated about the disorder and what symptoms to watch out for. Most patients are able to follow up with their primary care physician. In cases where the sinus bradycardia is recurrent, a consultation should be made with a cardiologist. All patients should be told to return to the ED if they develop syncope, dizziness, chest pain and shortness of breath. Even after a permanent pacemaker has been inserted, long term follow up is required because the battery may wear out and needs replacement.

Patients should be educated about endocarditis prophylaxis if they have a permanent a pacemaker inserted.

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2. Kumar P, Kusumoto FM, Goldschlager N. Bradyarrhythmias in the elderly. Clin Geriatr Med. 2012;28(4):703-15.
3. McClaskey D, Lee D, Buch E. Outcomes among athletes with arrhythmias and electrocardiographic abnormalities: implications for ECG interpretation. Sports Med. 2013;43(10):979-991
4. Holty JE, Guilleminault C. REM-related bradyarrhythmia syndrome. Sleep Med Rev. 2011;15(3):143-51.
5. Liu EF, Chen L, Gao BX. Sinus bradycardia: normal phenomenon or risk factor? Evaluation based on recent evidence. J Insur Med. 2012;43(2):102-11.
6. Semelka M, Gera J, Usman S. Sick sinus syndrome: a review. Am Fam Physician. 2013;87(10):691-6.
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9. Seiler J. Treatment of bradycardias - who needs a pacemaker?. Ther Umsch. 2014;71(2):105-10
10. Vardas PE, Simantirakis EN, Kanoupakis EM. New developments in cardiac pacemakers. Circulation. 2013;127(23):2343-50.