First - degree atrioventricular block - wikipedia First - degree atrioventricular block First - degree AV block Classification and external resources Specialty cardiology ICD - 10 I44. 0 ICD - 9 - CM 426.11 DiseasesDB 10477 eMedicine emerg / 233 ( edit on Wikidata ) First - degree atrioventricular block ( AV block ), or PR prolongation, is a disease of the electrical conduction system of the heart in which the PR interval is lengthened beyond 0.20 seconds. In first - degree AV block, the impulse conducting from atria to ventricles through the atrioventricular node ( AV node ) is delayed and travels slower than normal. It has a prevalence in the normal ( young adult ) population of 0.65 - 1.1 % and the incidence is 0.13 per 1000 persons. Contents 1 Causes 2 Diagnosis 3 Treatment 4 Prognosis 5 See also 6 References Causes The most common causes of first - degree heart block are an AV nodal disease, enhanced vagal tone ( for example in athletes ), myocarditis, acute myocardial infarction ( especially acute inferior MI ), electrolyte disturbances and medication. The drugs that most commonly cause first - degree heart block are those that increase the refractory time of the AV node, thereby slowing AV conduction. These include calcium channel blockers, beta - blockers, cardiac glycosides, and anything that increases cholinergic activity such as cholinesterase inhibitors. Digitalis is a sodium / potassium ATPase inhibitor and also prolongs AV conduction. Diagnosis In normal individuals, the AV node slows the conduction of electrical impulse through the heart. This is manifest on a surface electrocardiogram ( ECG ) as the PR interval. The normal PR interval is from 120 ms to 200 ms in length. This is measured from the initial deflection of the P wave to the beginning of the QRS complex. In first - degree heart block, the diseased AV node conducts the electrical activity more slowly. This is seen as a PR interval greater than 200 ms in length on the surface ECG. It is usually an incidental finding on a routine ECG. First - degree heart block does not require any particular investigations except for electrolyte and drug screens, especially if an overdose is suspected. Investigations may also be warranted with a prolonged interval that is greater than 0.2 sec. Treatment The management includes identifying and correcting electrolyte imbalances and withholding any offending medications. This condition does not require admission unless there is an associated myocardial infarction. Even though it usually does not progress to higher forms of heart block, it may require outpatient follow - up and monitoring of the ECG, especially if there is a comorbid bundle branch block. If there is a need for treatment of an unrelated condition, care should be taken not to introduce any medication that may slow AV conduction. If this is not feasible, clinicians should be very cautious when introducing any drug that may slow conduction ; and regular monitoring of the ECG is indicated. Prognosis Isolated first - degree heart block has no direct clinical consequences. There are no symptoms or signs associated with it. It was originally thought of as having a benign prognosis. In the Framingham Heart Study, however, the presence of a prolonged PR interval or first degree AV block doubled the risk of developing atrial fibrillation ( irregular heart beat ), tripled the risk of requiring an artificial pacemaker, and was associated with a small increase in mortality. This risk was proportional to the degree of PR prolongation. A subset of individuals with the triad of first - degree heart block, right bundle branch block, and either left anterior fascicular block or left posterior fascicular block ( known as trifascicular block ) may be at an increased risk of progression to complete heart block. See also Atrioventricular block Second - degree atrioventricular block Third - degree atrioventricular block References Jump up ^ `` Lesson VI - ECG Conduction Abnormalities ''. Retrieved 2009 - 01 - 07. Jump up ^ Cheng S, Keyes MJ, Larson MG, McCabe EL, Newton - Cheh C, Levy D, Benjamin EJ, Vasan RS, Wang TJ ( 2009 ). `` Long - term outcomes in individuals with prolonged PR interval or first - degree atrioventricular block ''. JAMA. 301 ( 24 ) : 25712577. doi : 10.1001 / jama. 2009.888. 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 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=First-degree_atrioventricular_block&oldid=779612254 '' Categories : Cardiac arrhythmia Hidden categories : Infobox medical condition Talk Contents About Wikipedia Italiano Português Edit links This page was last edited on 9 May 2017, at 22 : 52. 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Question: what is first degree av block in ecg
Answer: a disease of the electrical conduction system of the heart in which the PR interval is lengthened beyond 0.20 seconds