Premature atrial contraction
| Premature atrial contraction | |
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| 12 lead EKG shows Premature Atrial Contractions and bifascicular block (RBBB + LAFB) | |
| ICD-10 | I49.1 |
| ICD-9 | 427.61 |
| MeSH | D018880 |
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Premature atrial contraction Microchapters |
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Differentiating Premature atrial contraction from other Diseases |
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Diagnosis |
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Treatment |
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Case Studies |
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Premature atrial contraction On the Web |
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American Roentgen Ray Society Images of Premature atrial contraction |
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Risk calculators and risk factors for Premature atrial contraction |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Mugilan Poongkunran M.B.B.S [3]
Synonyms and keywords: PAC, PACs, premature atrial contractions, premature atrial complex, premature atrial complexes, APC, APCs, atrial premature contraction, atrial premature contractions, atrial premature complex, atrial premature complexes, APB, atrial premature beat, atrial premature beats, extrasystole, premature atrial beat, premature atrial beats, premature supraventricular beat, premature supraventricular beats
Overview
Premature atrial contractions is a benign type of premature heart beat which originates in one of the upper two chambers of the heart (the atria). PACs occur frequently in subjects with normal heart, however patients with structural heart disease and coronary heart disease are at increased risk. PACs usually reflect one of the conditions listed in the differential diagnosis of underlying causes below, and the treatment involves removing or treating the underlying cause. PACs are to be distinguished from premature ventricular contractions (PVCs) that originate in one of the lower pumping chambers (the ventricles).
Causes
Life Threatening Causes
Life-threatening causes include conditions which result in death or permanent disability within 24 hours if left untreated.
Common Causes
- Calcium channel blocker
- Cardiac stress test
- COPD
- Coronary heart disease
- Dehydration
- Ephedrine
- Hypokalemia
- Hypomagnesemia
- Obstructive sleep apnea
- Pneumonia
- Subclinical hyperthyroidism
- Sympathomimetic agents
Causes by Organ System
Causes in Alphabetical Order
Prognosis
In general the prognosis of PACs is good, and their occurrence and prognosis is determined by the underlying condition that triggered the PACs. In rare cases, a PAC can, like a PVC, trigger a more serious arrhythmia such as atrial flutter or atrial fibrillation. Unlike PVC's, PAC's generally do not cause hemodynamic compromise because the conduction throughout the AV node and ventricles is normal, and the filling and contraction of the heart is therefore normal.
Diagnosis
Symptoms
There may be a sense of "a skipped beat" or "a thump in the chest" or neck. In many cases, the person feels nothing.
Physical Examination
Pulse
The pulse may feel irregular in a patient who actively has frequent PACs.
Laboratory Findings
- Consider checking Thyroid Function Tests to rule out hyperthyroidism
- Consider checking hemoglobin and hematocrit to rule out anemia
Electrocardiogram
The presence of PACs is diagnosed based upon either an EKG, Holter, or Cardiac Event Monitor.
- By definition the P waves are premature
- Morphology of the P' wave is different than the P wave in normal sinus rhythm. 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 no compensatory pause. The PAC resets the sinus node.
- Most of 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
- The QRS complex is normal
- There is normal T wave repolarization (not inverted to the other T waves)
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EKG Examples
Shown below is an example of an EKG showing sinus rhythm with atrial premature beats in trigemini.
Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:Rhythm_premature.png
Shown below is an example of an EKG showing premature atrial contractions with evident negative p-wave.
Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:Bes.png
Shown below is an example of a 12 lead EKG showing premature atrial contractions in a patient with RBBB + LAFB
Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/Main_Page
Shown below is an EKG showing sinus rhythm with atrial premature beats in trigemini.
Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:E287.jpg
Shown below is an EKG showing sinus rhythm with premature atrial complexes. The P' wave can be seen deforming the T wave in the lead II rhythm strip. Note also that the atrial premature complexes reset the sinus node and hence there is no compensatory pause before the next sinus P wave. The QRS is deformed with a rsR' in V1 and a broad S in I with a duration of > 120 ms. diagnostic of aberrance with a right bundle branch morphology. The S1 Q3 and the right ward axis of the aberrant complexes suggest an additional left posterior fasicular block.
Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:E000746.jpg
Shown below is an EKG showing an atrial premature beat (3rd beat). In fact note the QT interval of the second beat is short and in fact this was an artifact from a paper jam in the EKG recorder. The EKG also shows a first degree A/V block and abnormal Q waves in the inferior and anterior leads consistent with inferior and anterior myocardial infarctions which are probably old.
Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:E281.jpg
Treatment
Removal or treatment of the underlying cause of PACs listed in the differential diagnosis is generally sufficient. Beta-blockers may be helpful if the patient remains symptomatic.