Premature atrial contraction
28,571views
00:00 / 00:00
Videos
Notes
Premature atrial contraction
Pathology
Vascular disorders
Arterial disease
Angina pectoris
Stable angina
Unstable angina
Myocardial infarction
Prinzmetal angina
Coronary steal syndrome
Peripheral artery disease
Subclavian steal syndrome
Aneurysms
Aortic dissection
Vasculitis
Behcet's disease
Kawasaki disease
Hypertension
Hypertensive emergency
Renal artery stenosis
Coarctation of the aorta
Cushing syndrome
Conn syndrome
Pheochromocytoma
Polycystic kidney disease
Hypotension
Orthostatic hypotension
Abetalipoproteinemia
Familial hypercholesterolemia
Hypertriglyceridemia
Hyperlipidemia
Chronic venous insufficiency
Thrombophlebitis
Deep vein thrombosis
Lymphedema
Lymphangioma
Shock
Vascular tumors
Human herpesvirus 8 (Kaposi sarcoma)
Angiosarcomas
Congenital heart defects
Truncus arteriosus
Transposition of the great vessels
Total anomalous pulmonary venous return
Tetralogy of Fallot
Hypoplastic left heart syndrome
Patent ductus arteriosus
Ventricular septal defect
Coarctation of the aorta
Atrial septal defect
Cardiac arrhythmias
Atrial flutter
Atrial fibrillation
Premature atrial contraction
Atrioventricular nodal reentrant tachycardia (AVNRT)
Wolff-Parkinson-White syndrome
Ventricular tachycardia
Brugada syndrome
Premature ventricular contraction
Long QT syndrome and Torsade de pointes
Ventricular fibrillation
Atrioventricular block
Bundle branch block
Pulseless electrical activity
Valvular disorders
Tricuspid valve disease
Pulmonary valve disease
Mitral valve disease
Aortic valve disease
Cardiomyopathies
Dilated cardiomyopathy
Restrictive cardiomyopathy
Hypertrophic cardiomyopathy
Heart failure
Heart failure
Cor pulmonale
Cardiac infections
Endocarditis
Myocarditis
Rheumatic heart disease
Pericardial disorders
Pericarditis and pericardial effusion
Cardiac tamponade
Dressler syndrome
Cardiac tumors
Cardiac tumors
Cardiovascular system pathology review
Acyanotic congenital heart defects: Pathology review
Cyanotic congenital heart defects: Pathology review
Atherosclerosis and arteriosclerosis: Pathology review
Coronary artery disease: Pathology review
Peripheral artery disease: Pathology review
Valvular heart disease: Pathology review
Cardiomyopathies: Pathology review
Heart failure: Pathology review
Supraventricular arrhythmias: Pathology review
Ventricular arrhythmias: Pathology review
Heart blocks: Pathology review
Aortic dissections and aneurysms: Pathology review
Pericardial disease: Pathology review
Endocarditis: Pathology review
Hypertension: Pathology review
Shock: Pathology review
Vasculitis: Pathology review
Cardiac and vascular tumors: Pathology review
Dyslipidemias: Pathology review
Assessments
Premature atrial contraction
Flashcards
0 / 6 complete
USMLE® Step 1 questions
0 / 1 complete
High Yield Notes
5 pages
Flashcards
Premature atrial contraction
of complete
Questions
USMLE® Step 1 style questions USMLE
of complete
Image reproduced from Wikimedia Commons
Which of the following features of this patient's electrocardiogram can be used to localize the anatomic origin of this arrhythmia?
External Links
Transcript
Content Reviewers
Rishi Desai, MD, MPHThe heart has two upper chambers, which are called the atria, and a premature atrial contraction, or PAC, is when the atria contract earlier than normal in the cardiac cycle.
So normally, the sinoatrial, or SA, node sends an electrical signal called a depolarization that propagates out through the walls of the heart and causes both upper chambers to contract. Then, that signal moves to the atrioventricular, or AV, node, where it’s delayed for a split second. Then, the signal travels down into the ventricles, or lower chambers, where it moves down the bundle of His into the left and right bundle branches and into each ventricle’s Purkinje fibers, causing them to contract as well. This trip is called a depolarization wave, and in a healthy heart, it makes sure that the upper chambers contract before the lower chambers contract. On an electrocardiogram, or ECG, which measures the electrical activity of the heart via electrodes that are placed on the skin, the atrial depolarization and its contraction are seen as a P-wave, the ventricular contraction is seen as a QRS complex, and the ventricular repolarization and its relaxation are seen as a T-wave.
If an atrial cell outside of the SA node initiates a depolarization, that’s called an atrial ectopic focus. Now, this could be initiated by a cell that’s part of the conduction system, or it could just be initiated by another cardiac muscle cell. This typically happens when atrial cells are irritated and stressed by electrolyte imbalances, drugs like cocaine or methamphetamines, ischemic damage like a heart attack, or anything that increases sympathetic activity, like anxiety. Another type of atrial ectopic focus is a reentrant loop, which is when there’s some tissue that doesn’t depolarize properly, which could happen in scar tissue after a heart attack. As a result of this damage, the depolarization wave ends up circling around and around that tissue. A reentrant loop basically starts sending out depolarization waves to the rest of the heart tissue each time the wave goes around.
Summary
Premature atrial contraction is when the atria contract too early because of depolarization from an ectopic focus. While the sinoatrial node typically regulates the heartbeat during normal sinus rhythm, premature atrial contractions occur when another region of the atria depolarizes before the sinoatrial node and thus triggers a premature heartbeat. The ECG will show an early and abnormal P-wave, as well as one of three patterns, depending on when the PAC occurs: normal ventricular conduction, aberrant ventricular conduction, or a conduction block.
Sources
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "Premature atrial contraction-induced cardiomyopathy" EP Europace (2013)
- "Excessive Premature Atrial Complexes and the Risk of Recurrent Stroke or Death in an Ischemic Stroke Population" Journal of Stroke and Cerebrovascular Diseases (2017)
Copyright © 2023 Elsevier, except certain content provided by third parties
Cookies are used by this site.
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.
