QRS interval

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Duration

The precordial leads are approximately 0.01 or 0.02 seconds longer than the standard leads.

Amplitude

Definitions of Low Voltage:

• If the total amplitude above and below the isoelectric line is < 5 mm in all 3 standard leads.
  
• An average voltage in the limb leads of < 5 mm with an average of < 10 mm in the chest leads (1).
  
• Should be at least 5 mm in V1 and V6 , 7 mm in V2 and V5 and 9 mm in V3 and V4.
  
  

Differential diagnosis of low voltage:

• Diffuse Coronary artery disease
• Congestive heart failure
• Pericardial effusion (See also Diseases of the Pericardium)
• Myxedema
• Amyloidosis
• Emphysema
• Obesity

Definition of maximal voltage:

Can be up to 20 to 30 mm in lead 2 and can be up to 25 to 30 mmm in the precordial leads.

References

1. Unverferth, Chest 1979: 75, 157.

Additional resources

• ECGpedia: Course for interpretation of ECG
• The whole ECG - A basic ECG primer
• 12-lead ECG library
• Simulation tool to demonstrate and study the relation between the electric activity of the heart and the ECG
• ECG information from Children's Hospital Heart Center, Seattle
• ECG Challenge from the ACC D2B Initiative
• National Heart, Lung, and Blood Institute, Diseases and Conditions Index
• A history of electrocardiography
• EKG Interpretations in infants and children

v • d • e Electrocardiography
Overview	History of the EKG • EKG interpretation basics • Normal sinus rhythm
EKG Complexes	P wave • QRS complex • ST Segment • T wave • U wave Osborn wave • H wave • K wave • Delta wave NSSTW changes
EKG Intervals	PR Interval • QRS Interval • ST Interval • QT Interval
Conduction System & Bradycardia	Cardiac pacemaker • SA node • AV node• Bundle of His • Purkinje fibers • Sinus bradycardia • First Degree AV Block • Second Degree AV Block • Complete or Third-Degree AV Block • Concealed conduction • AV Junctional Rhythms • LBBB • LAHB • LPHB • RBBB • Trifascicular block
Atrial Arrhythmias	Sinus tachycardia • Premature Atrial Contractions (PACs) • Ectopic Atrial Rhythm • Paroxysmal Atrial Tachycardia (PAT) • Paroxysmal Atrial Tachycardia (PAT) with Block • Multifocal Atrial Tachycardia (MAT) • Atrial Flutter • Atrial Fibrillation • Wandering atrial pacemaker
Ventricular Arrhythmias	Differential Diagnosis of Tachycardia with a Wide QRS Complex • Accelerated Idioventricular Rhythm • Ventricular Parasystole • Premature Ventricular Contractions (PVCs) • Ventricular tachycardia • Ventricular Fibrillation • Sudden cardiac death
EKG Abnormalities in Disease States	Hypertrophy & Dilatation • Right atrial enlargement • Left atrial enlargement • Biatrial enlargement • Left Ventricular Hypertrophy • Right Ventricular Hypertrophy • Biventricular Hypertrophy • Acute myocardial infarction • NSTEMI • STEMI • Right ventricular myocardial infarction • Atrial infarction Pre-excitation Syndromes • Wolff-Parkinson-White Syndrome • Lown Ganong Levine Syndrome • Mahaim Type Preexcitation Cardiomyopathies • Arrhythmogenic Right Ventricular Dysplasia • Dilated Cardiomyopathy • Hypertrophic Cardiomyopathy Drug Effects on the EKG • Adenosine • β-blockers • Digitalis • Quinidine • Procainamide • Disopyramide • Lidocaine • Tocainide and Mexiletine • Phenytoin • Encainide, Flecainide and Propafenone • Amiodarone • Bretylium • Ca Channel Blockers • Phenothiazines • Tricyclic Antidepressants • Lithium Congenital Heart Disease • Dextrocardia • Atrial Septal Defect • Ventricular Septal Defect • Tetralogy of Fallot • Conjoined Twins or Siamese Twins • Congenital heart block Electrolyte Disturbances • Hyperkalemia • Hypokalemia • Hypercalcemia • Hypocalcemia • Nonspecific Changes Other Heart Diseases • Pericarditis • Myocarditis • Tamponade • Heart Transplantation • Sick Sinus Syndrome • Long QT Syndrome Inherited Disease • Brugada Syndrome Systemic Diseases • CNS Disease • Cardiac Tumors Heart Transplantation • EKG Changes in patient with Heart Transplantation Exogenous Effects • Hypothermia • Chest Trauma • Insect Bites • Electric Injuries
Technical Issues and Potential Errors in Interpretation	Artifacts • Lead Placement Errors • The EKG in a Patient with a Pacemaker • EKG in athletes

v • d • e Circulatory system pathology (I, 390-459)
Hypertension	Hypertensive heart disease - Hypertensive nephropathy - Secondary hypertension (Renovascular hypertension)
Ischaemic heart disease	Angina pectoris (Prinzmetal's angina) - Myocardial infarction (heart attack) - Dressler's syndrome
Pulmonary circulation	Pulmonary embolism - Cor pulmonale
Pericardium	Pericarditis - Pericardial effusion - Cardiac tamponade
Endocardium/heart valves	Endocarditis - mitral valve (regurgitation, prolapse, stenosis) - aortic valve (stenosis, insufficiency) - pulmonary valve (stenosis, insufficiency) - tricuspid valve (stenosis, insufficiency)
Myocardium	Myocarditis - Cardiomyopathy (Dilated cardiomyopathy, Hypertrophic cardiomyopathy, Loeffler endocarditis, Restrictive cardiomyopathy) - Arrhythmogenic right ventricular dysplasia
Electrical conduction system of the heart	Heart block: AV block (First degree, Second degree, Third degree) - Bundle branch block (Left, Right) - Bifascicular block - Trifascicular block Pre-excitation syndrome (Wolff-Parkinson-White, Lown-Ganong-Levine) - Long QT syndrome - Adams-Stokes syndrome - Cardiac arrest - Sudden cardiac death Arrhythmia: Paroxysmal tachycardia (Supraventricular, AV nodal reentrant, Ventricular) - Atrial flutter - Atrial fibrillation (Familial) - Ventricular fibrillation - Premature contraction (Atrial, Ventricular) - Ectopic pacemaker - Sick sinus syndrome
Other heart conditions	Heart failure - Cardiovascular disease - Cardiomegaly - Ventricular hypertrophy (Left, Right)
Cerebrovascular diseases	Stroke - Transient ischemic attack - Intracranial hemorrhage/cerebral hemorrhage: Extra-axial hemorrhage (Epidural hemorrhage, Subdural hemorrhage, Subarachnoid hemorrhage) Intra-axial hematoma (Intraventricular hemorrhages, Intraparenchymal hemorrhage) - Anterior spinal artery syndrome - Binswanger's disease - Moyamoya disease
Arteries, arterioles and capillaries	Atherosclerosis (Renal artery stenosis) - Aortic dissection/Aortic aneurysm (Abdominal aortic aneurysm) - Aneurysm - Raynaud's phenomenon/Raynaud's disease - Buerger's disease - Vasculitis/Arteritis (Aortitis) - Intermittent claudication - Arteriovenous fistula - Hereditary hemorrhagic telangiectasia - Spider angioma - Dissection (Carotid artery, Vertebral artery)
Veins, lymphatic vessels and lymph nodes	Thrombosis/Phlebitis/Thrombophlebitis (Deep vein thrombosis, May-Thurner syndrome, Portal vein thrombosis, Venous thrombosis, Budd-Chiari syndrome, Renal vein thrombosis, Paget-Schroetter disease) - Varicose veins / Portacaval anastomosis (Hemorrhoid, Esophageal varices, Varicocele, Gastric varices, Caput medusae) - Superior vena cava syndrome - Lymph (Lymphadenitis, Lymphedema, Lymphangitis)
Other	Hypotension (Orthostatic hypotension) - Rheumatic fever
See also congenital (Q20-Q28, 745-747)

v • d • e WikiDoc Research Resources for QRS interval
Articles on QRS interval	Most recent articles on QRS interval • Most cited articles on QRS interval • Review articles on QRS interval • Articles on QRS interval in N Eng J Med, Lancet, BMJ
Media (Slides, Video, Images, MP3) on QRS interval	Powerpoint slides on QRS interval • Images of QRS interval • Photos of QRS interval • Podcasts & MP3s on QRS interval • Videos on QRS interval
Evidence Based Medicine Regarding QRS interval	Cochrane Collaboration on QRS interval • Bandolier on QRS interval • TRIP on QRS interval
Cost Effectiveness of QRS interval	Cost Effectiveness of QRS interval
Clinical Trials Involving QRS interval	Ongoing Trials on QRS interval at Clinical Trials.gov • Trial results on QRS interval • Clinical Trials on QRS interval at Google
Guidelines / Policies / Government Resources (FDA/CDC) Regarding QRS interval	US National Guidelines Clearinghouse on QRS interval • NICE Guidance on QRS interval • NHS PRODIGY Guidance • FDA on QRS interval • CDC on QRS interval
Textbook Information on QRS interval	Books and Textbook Information on QRS interval
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Newstories on QRS interval	QRS interval in the news • Be alerted to news on QRS interval • News trends on QRS interval
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Patient Resources on QRS interval	Patient resources on QRS interval • Discussion groups on QRS interval • Patient Handouts on QRS interval • Directions to Hospitals Treating QRS interval • Risk calculators and risk factors for QRS interval
Healthcare Provider Resources on QRS interval	Symptoms of QRS interval • Causes & Risk Factors for QRS interval • Diagnostic studies for QRS interval • Treatment of QRS interval
Continuing Medical Education (CME) Programs on QRS interval	CME Programs on QRS interval
International Resources on QRS interval	QRS interval en Espanol • QRS interval en Francais
Business Resources on QRS interval	QRS interval in the Marketplace • Patents on QRS interval
Informatics Resources on QRS interval	List of terms related to QRS interval