Sinus bradycardia - wikipedia Sinus bradycardia This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( August 2014 ) Sinus bradycardia Sinus bradycardia seen in lead II with a heart rate of about 50. Classification and external resources ICD - 9 - CM 427.81 MeSH D001146 ( edit on Wikidata ) Sinus bradycardia is a sinus rhythm with a rate that is lower than normal. In humans, bradycardia is generally defined to be a rate of under 60 beats per minute. Contents 1 Signs and symptoms 2 Causes 3 Diagnosis 4 See also 5 References Signs and symptoms The decreased heart rate can cause a decreased cardiac output resulting in symptoms such as lightheadedness, dizziness, hypotension, vertigo, and syncope. The slow heart rate may also lead to atrial, junctional, or ventricular ectopic rhythms. Bradycardia is not necessarily problematic. People who regularly practice sports may have sinus bradycardia, because their trained hearts can pump enough blood in each contraction to allow a low resting heart rate. Sinus bradycardia can also be an adaptive advantage ; for example, diving seals may have a heart rate as low as 12 beats per minute, helping them to conserve oxygen during long dives. Sinus bradycardia is a common condition found in both healthy individuals and those who are considered well conditioned athletes. Heart rates considered bradycardic vary by species ; for example, in the common housecat, a rate of under 120 beats per minute is abnormal. Generally, smaller species have higher heart rates while larger species have lower rates. Causes This rhythm may be caused by one of the following : Increased vagal tone. Sleep Hypothermia Hypothyroidism Roemheld syndrome Intrinsic disease of the SA node ( E.g. sick sinus syndrome ). An effect of drugs, such as the use of digitalis, beta - blockers, quinidine, adenosine, calcium channel blocker chest pains Seizure. It could also be a normal finding in a healthy, well - conditioned person. It may be secondary to infections like diphtheria, acute rheumatic fever, viral myocarditis. Increased intracranial pressure. Rhodotoxin poisoning. As a result of an eating disorder, such as anorexia nervosa. as in carotid sinus syndrome, acute myocardial infarction. Diagnosis ECG characteristics Rate : Less than 60 beats per minute. Rhythm : Regular. P waves : Upright, consistent, and normal in morphology and duration. P-R Interval : Between 0.12 and 0.20 seconds in duration. QRS Complex : Less than 0.12 seconds in width, and consistent in morphology. See also Sinus tachycardia Long QT syndrome References Jump up ^ THORNTON ( 2004 ). `` Oxygen and the diving seal '' ( PDF ). The Journal of Hyperbaric Medicine. 31 ( 1 ) : 81 -- 95. Retrieved 29 July 2014. Cardiovascular disease ( heart ) ( I00 -- I52, 390 -- 429 ) Ischaemic Coronary disease Coronary artery disease ( CAD ) Coronary artery aneurysm Spontaneous coronary artery dissection ( SCAD ) Coronary thrombosis Coronary vasospasm Myocardial bridge Active ischemia Angina pectoris Prinzmetal 's angina Stable angina Acute coronary syndrome Myocardial infarction Unstable angina Sequelae hours Hibernating myocardium Myocardial stunning days Myocardial rupture weeks Aneurysm of heart / Ventricular aneurysm Dressler syndrome Layers Pericardium Pericarditis Acute Chronic / Constrictive Pericardial effusion Cardiac tamponade Hemopericardium Myocardium Myocarditis Chagas disease Cardiomyopathy : Dilated ( Alcoholic ), Hypertrophic, and Restrictive Loeffler endocarditis Cardiac amyloidosis Endocardial fibroelastosis Arrhythmogenic right ventricular dysplasia Endocardium / valves Endocarditis infective endocarditis Subacute bacterial endocarditis non-infective endocarditis Libman -- Sacks endocarditis Nonbacterial thrombotic endocarditis Valves mitral regurgitation prolapse stenosis aortic stenosis insufficiency tricuspid stenosis insufficiency pulmonary stenosis insufficiency Conduction / arrhythmia Bradycardia Sinus bradycardia Sick sinus syndrome Heart block : Sinoatrial AV 1 ° 2 ° 3 ° Intraventricular Bundle branch block Right Left Left anterior fascicle Left posterior fascicle Bifascicular Trifascicular Adams -- Stokes syndrome Tachycardia ( paroxysmal and sinus ) Supraventricular Atrial Multifocal Junctional AV nodal reentrant Junctional ectopic Ventricular Accelerated idioventricular rhythm Catecholaminergic polymorphic Torsades de pointes Premature contraction Atrial Junctional Ventricular Pre-excitation syndrome Lown -- Ganong -- Levine Wolff -- Parkinson -- White Flutter / fibrillation Atrial flutter Ventricular flutter Atrial fibrillation Familial Ventricular fibrillation Pacemaker Ectopic pacemaker / Ectopic beat Multifocal atrial tachycardia Pacemaker syndrome Parasystole Wandering pacemaker Long QT syndrome Andersen -- Tawil Jervell and Lange - Nielsen Romano -- Ward Cardiac arrest Sudden cardiac death Asystole Pulseless electrical activity Sinoatrial arrest Other / ungrouped hexaxial reference system Right axis deviation Left axis deviation QT Short QT syndrome T wave alternans ST Osborn wave ST elevation ST depression Strain pattern Cardiomegaly Ventricular hypertrophy Left Right / Cor pulmonale Atrial enlargement Left Right Other Cardiac fibrosis Heart failure Diastolic heart failure Cardiac asthma Rheumatic fever Retrieved from `` https://en.wikipedia.org/w/index.php?title=Sinus_bradycardia&oldid=778657310 '' Categories : Cardiac arrhythmia Hidden categories : Articles needing additional references from August 2014 All articles needing additional references Talk Contents About Wikipedia Čeština Italiano Nederlands Português Sicilianu Svenska Edit links This page was last edited on 4 May 2017, at 13 : 57. 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Question: which sinus rhythm has a rate of less than 60 beats per minute
Answer: humans