Atrial fibrillation diagnosis overview
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| Conduction | ||
Sinus rhythm  | Atrial fibrillation  | |
| Atrial fibrillation Classification and external resources | |
 | |
|---|---|
| The P waves, which represent depolarization of the atria, are irregular or absent during atrial fibrillation. | |
| ICD-10 | I48. |
| ICD-9 | 427.31 |
| DiseasesDB | 1065 |
| MedlinePlus | 000184 |
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 Discuss Atrial fibrillation diagnosis overview further in the WikiDoc Cardiology Network |
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Synonyms and related keywords: AF, Afib, fib
Diagnosis of atrial fibrillation
The evaluation of atrial fibrillation involves diagnosis, determination of the etiology of the arrhythmia, and classification of the arrhythmia. A minimal evaluation performed should be performed in all individuals with atrial fibrillation. This includes a history and physical examination, surface electrocardiogram, transthoracic echocardiogram, and routine blood work. Certain individuals may benefit from an extended evaluation which may include an evaluation of the heart rate response to exercise, exercise stress testing, a chest x-ray, trans-esophageal echocardiography, and other studies.
- Screening and routine primary care visit for atrial fibrillation
- History and physical examination for atrial fibrillation
- Electrocardiogram for diagnosis of atrial fibrillation
- Chest x-ray for diagnosis of atrial fibrillation
- Echocardiography for diagnosis of atrial fibrillation
- Recorders (Holter monitors) for diagnosis of atrial fibrillation
- Exercise stress tests (Tilt-Table Test) for diagnosis of atrial fibrillation
- Electrophysiologic Testing or Electrophysiologic Studies for diagnosis of atrial fibrillation
Screening and routine primary care visit
Screening for atrial fibrillation is not generally performed, although a study of routine pulse checks or electrocardiograms during routine office visits, found that the annual rate of detection of atrial fibrillation in elderly patients improved from 1.04% to 1.63%; selection of patients for prophylactic anticoagulation would improve stroke risk in that age category.[1]
Estimated sensitivity of the routine primary care visit is 64%. This low result probably reflects the pulse not being checked routinely or carefully.[1]
History and physical examination for atrial fibrillation
The history of the individual's atrial fibrillation episodes is likely the most important part of the evaluation. Distinctions should be made to those who are entirely asymptomatic when they are in atrial fibrillation (in which case the atrial fibrillation is found as an incidental finding on an electrocardiogram or physical examination) and those who have gross and obvious symptoms due to atrial fibrillation and can pinpoint whenever they go into atrial fibrillation and revert to sinus rhythm.
Detailed history and physical examination are essential to define;
- The presence and nature of symptoms associated with AF
- The clinical type of AF (first episode, paroxysmal, persistent, or permanent)
- The onset of the first symptomatic attack or date of discovery of AF
- The frequency, duration, precipitating factors, and modes of termination of AF
- The response to any pharmacological agents that have been administered
- The presence of any underlying heart disease or other reversible conditions (e.g., hyperthyroidism or alcohol consumption)
Routine blood work
While many cases of AF have no definite cause, it may be the result of various other problems (Blood tests of thyroid function are required, especially for a first episode of AF, when the ventricular rate is difficult to control, or when AF recurs unexpectedly after cardioversion)
Hence, renal function and electrolytes are routinely determined, as well as thyroid-stimulating hormone (commonly suppressed in hyperthyroidism and of relevance if amiodarone is administered for treatment) and a blood count.[2]
In acute-onset AF associated with chest pain, cardiac troponins or other markers of damage to the heart muscle may be ordered. Coagulation studies (INR/aPTT) are usually performed, as anticoagulant medication may be commenced.[2]
Electrocardiogram
Atrial fibrillation is diagnosed on an electrocardiogram, an investigation performed routinely whenever irregular heart beat is suspected. Characteristic findings are the absence of P waves, with unorganized electrical activity in their place, and irregularity of R-R interval due to irregular conduction of impulses to the ventricles.[2]
EKG is helpful to identify;
- Rhythm (verify AF)
- LV hypertrophy
- P-wave duration and morphology or fibrillatory waves
- Preexcitation
- Bundle-branch block
- Prior MI
- Other atrial arrhythmias
- To measure and follow the RR, QRS, and QT intervals in conjunction with antiarrhythmic drug therapy
Summary of Electrocardiographic findings
- Absent P waves
- Irregularly irregular ventricular response rate. Regular RR intervals are possible in the presence of AV block or interference due to ventricular or junctional tachycardia.
- An atrial rate that ranges from 400 to 700 BPM.
- sometimes V1 may look as though there is atrial flutter. This may be because the electrode overlies a portion of the RA with rhythmic activity.
- Some authors believe that fine f waves (<.5 mm) are associated with coronary artery disease and that coarse F waves are associated with LA enlargement and rheumatic heart disease.
- the ventricular rate is usually between 100 and 180 BPM.
- if the atrial rate is greater than 200 BPM, then consider WPW or an accessory pathway.
- In the presence of AV junctional disease, the ventricular rate may be below 70 bpm.
- a rapid, irregular, sustained, wide-QRS-complex tachycardia strongly suggests AF with conduction over an accessory pathway or AF with underlying bundle-branch block.
- Complete AV block is indicated by a slow ventricular rhythm with a regular RR interval.
- In patients with electronic pacemakers, diagnosis of AF may require temporary inhibition of the pacemaker to expose atrial fibrillatory activity.
- Differential diagnosis includes tremor due to artifact. The oscillations in this case are largest in the limb leads.
When electrocardiograms are used for screening? The SAFE trial found that electronic software, primary care physicians and the combination of the two had the following sensitivities and specificities:[3]:
- Interpreted by software: sensitivity = 83%, specificity = 99%
- Interpreted by a primary care physician: sensitivity = 80%, specificity = 92%
- Interpreted by a primary care physician with software: sensitivity = 92%, specificity = 91%
If paroxysmal AF is suspected but the electrocardiogram shows a regular rhythm, episodes may be documented with the use of Holter monitoring (continuous ECG recording for 24 hours). If the symptoms are very infrequent, longer periods of continuous monitoring may be required.[2]
EKG Examples of atrial fibrillation
External EKG Sources
Chest X-ray
A chest X-ray is generally only performed if a pulmonary cause of atrial fibrillation is suggested. This may reveal an underlying problem in the lungs or the blood vessels in the chest. [2] In particular, if an underlying pneumonia is suggested, then treatment of the pneumonia may cause the atrial fibrillation to terminate on its own.
As a summary a chest radiograph is required to evaluate;
- The lung parenchyma, when clinical findings suggest an abnormality
- The pulmonary vasculature, when clinical findings suggest an abnormality
Echocardiography
Performing an echocardiogram is essential to identify;
- Valvular heart disease
- Left and right atrial size
- LV size and function
- Peak RV pressure (pulmonary hypertension)
- LV hypertrophy
- LA thrombus (low sensitivity)
- Pericardial disease
Transthoracic echocardiography (TTE)
A transthoracic echocardiogram is generally performed in newly diagnosed AF, as well as if there is a major change in the patient's clinical state. This ultrasound-based scan of the heart may help identify valvular heart disease (which may increase the risk of stroke manifold), left and right atrial size (which indicates likelihood that AF may become permanent), left ventricular size and function, peak right ventricular pressure (pulmonary hypertension), presence of left ventricular hypertrophy and pericardial disease.[2]
Significant enlargement of both the left and right atria is associated with long-standing atrial fibrillation and, if noted at the initial presentation of atrial fibrillation, suggests that the atrial fibrillation is likely of a longer duration than the individual's symptoms.
Transesophageal echocardiography (TEE)
A normal echocardiography (transthoracic or TTE) has a low sensitivity for identifying thrombi (blood clots) in the heart. If this is suspected - e.g. when planning urgent electrical cardioversion - a transesophageal echocardiogram (TEE) is preferred.[2]
The TEE has much better visualization of the left atrial appendage than transthoracic echocardiography. This structure, located in the left atrium, is the place where thrombus most commonly is formed in the setting of atrial fibrillation or flutter. TEE has a very high sensitivity for locating thrombus in this area and can also detect sluggish bloodflow in this area that is suggestive of thrombus formation.
If no thrombus is seen on TEE, the incidence of stroke immediately after cardioversion is performed is very low.
Ambulatory Holter monitoring
A holter monitor is a wearable ambulatory heart monitor that continuously monitors the heart rate and heart rhythm for a short duration, typically 24 hours. In individuals with symptoms of significant shortness of breath with exertion or palpitations on a regular basis, a holter monitor may be of benefit to determine if rapid heart rates (or unusually slow heart rates) during atrial fibrillation are the cause of the symptoms.
Exercise stress testing
Some individuals with atrial fibrillation do well with normal activity but develop shortness of breath with exertion. It may be unclear if the shortness of breath is due to a blunted heart rate response to exertion due to excessive AV node blocking agents, a very rapid heart rate during exertion, or due to other underlying conditions such as chronic lung disease or coronary ischemia. An exercise stress test will evaluate the individual's heart rate response to exertion and determine if the AV node blocking agents are contributing to the symptoms. As a summary the main benefits of performing an exercise stress testing;
- If the adequacy of rate control is in question (permanent AF)
- To reproduce exercise-induced AF
- To exclude ischemia before treatment of selected patients with a type IC antiarrhythmic drug
See Also
References
- ↑ 1.0 1.1 Fitzmaurice DA, Hobbs FD, Jowett S, et al (2007). "Screening versus routine practice in detection of atrial fibrillation in patients aged 65 or over: cluster randomized controlled trial". doi:10.1136/bmj.39280.660567.55. PMID 17673732.
- ↑ Cite error 8; No text given.
- ↑ Mant J, Fitzmaurice DA, Hobbs FD, et al (2007). "Accuracy of diagnosing atrial fibrillation on electrocardiogram by primary care practitioners and interpretative diagnostic software: analysis of data from screening for atrial fibrillation in the elderly (SAFE) trial". doi:10.1136/bmj.39227.551713.AE. PMID 17604299.
Further Readings
- Fuster V, Rydén LE, Cannom DS, et al (2006). "ACC/AHA/ESC 2006 Guidelines for the Management of Patients with Atrial Fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society". Circulation 114 (7): e257-354. doi:10.1161/CIRCULATIONAHA.106.177292. PMID 16908781.
- Estes NAM 3rd, Halperin JL, Calkins H, Ezekowitz MD, Gitman P, Go AS, McNamara RL, Messer JV, Ritchie JL, Romeo SJW, Waldo AL, Wyse DG. ACC/AHA/Physician Consortium 2008 clinical performance measures for adults with non valvular atrial fibrillation or atrial flutter: a report of the American College of Cardiology/American Heart Association Task Force on Performance Measures and the Physician Consortium for Performance Improvement (Writing Committee to Develop Performance Measures for Atrial Fibrillation). Circulation 2008; 117:1101–1120
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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 .
