Premature atrial contraction
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| Premature atrial contraction Classification and external resources | |
 | |
|---|---|
| 12 lead EKG shows Premature Atrial Contractions and bifascicular block (RBBB + LAFB) | |
| ICD-10 | I49.1 |
| ICD-9 | 427.61 |
| MeSH | D018880 |
| Cardiology Network |
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Overview
Premature atrial contractions or (PACs) are a type of premature heart beat, irregular heart beat or benign arrhythmia which start in the upper two chambers of the heart, also called atria. These aren't as serious as a Premature Ventricular Contraction and usually require no medical care. Individuals with the condition may report feeling that his or her heart "stops" after a symptom. PVCs are also called heart palpitations (although there are many other forms of arrhythmia).
In many cases doctors are unable to determine a cause. Some cells in the heart (ectopic foci) start to fire or go off before the normal heart beat is supposed to occur in the SA node. These can be cells that are damaged or sick from a virus, or from some other cause that a doctor can't determine, many times, doctors don't know why they happen. Sometimes people who have them feel a skipped beat or a thump in their chest or neck. In many cases, the person feels nothing.
Usually a doctor will do or order an EKG, Holter, or Cardiac Event Monitor for the person to wear. Without an EKG, it is impossible to determine the existence of PACs or whether they aren't a PAC at all. Once proven, the person may be referred to a cardiologist for further testing to determine whether the heart is damaged or deteriorated. In the case that it isn't, sometimes simple lifestyle changes can alter and/or prevent the occurances of PAC's. Exercising, eating right, and lowering stress levels are the most effective ways of reducing the occurences.
In rare cases, a PAC can, like a PVC, trigger a more serious arrhythmia such as Atrial flutter or fibrillation. This is seldom seen in a healthy heart, but in a case that it does happen, medical attention should be sought to see what might have caused the problem and what steps can be taken to fix it. Unlike PVC's, PAC's generally do not compromise the hemodynamic system because the conduction throughout the AV node, and the ventricles of the heart are activated in a normal sequence. a PAC usually will also on the EKG be characterized by: - a normal QRS complex - a normal T wave repolarization (not inverted to the other T waves) - an odd, mis-shapen P wave depolarization
Electrocardiographic Findings:
- By definition the P waves are premature
- Morphology of the P' wave is different than the NSR P wave. If its origin is close to that of the sinus node, then the P' morphology is hard to distinguish from the native sinus P wave.
- A PAC differs from a Premature Junctional Contraction (PJC) in that the PR interval is > 0.12 second in a PAC.
- The PR interval may be shorter than that in Normal Sinus Rhythm (NSR) if it is located closer to the AV node.
- The PR interval tends to lengthen when the coupling time to the PAC is short.
- A PAC may not be conducted to the ventricles and this is called a blocked PAC.
- The differential diagnosis in this scenario includes second degree AV block. In second degree AV block, the PP intervals remain constant.
- Usually the QRS is of normal duration, but occasionally there is aberrant conduction, most frequently of Right Bundle Branch Block (RBBB) morphology.
- Aberrancy is more likely to occur when the coupling time is shorter.
- Usually there is not a compensatory pause. The PAC resets the sinus node.
- Most these patients do not have organic heart disease.
- 64% of healthy subjects will have PACs on 24 hour Holter monitoring.
- Frequency higher in the elderly
- In some patients they are related to emotional stress, mental and physical fatigue, excessive smoking, or intake of alcohol and coffee.
- The incidence of PACs is increased among patients with organic heart disease.
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
Examples
 Premature Atrial Contractions |
 Premature Atrial Contractions |
12 lead EKG shows Premature Atrial Contractions in patient with RBBB + LAFB |
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
