Atrial Fibrillation
| This is part of: Supraventricular Rhythms |
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| Atrial rate | 400-600 bpm |
| Ventricular rate | 75-175 bpm |
| Regularity | irregular |
| Origin | atria (SVT) |
| P-wave | absebt |
| Effect of adenosine | reduces heart rate |
Example ECG: 
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| Example ECG2: {{{example2}}} | |
During atrial fibrillation the atria show chaotic depolarisation with multiple foci. Mechanically the atria stop contracting after several days to weeks of atrial fibrillation, the result of the ultra-rapid depolarisations that occur in the atria, typically around 400 bpm, but up to 600 bpm. At the AV node 'every now and then' a beat is conducted to the ventricles, resulting in an irregular ventricular rate, which is the typical ECG characteristic of atrial fibrillation. Sometimes atrial fibrillation results in a course atrial flutter wave on the ECG, but the baseline can also be flat. A flat baseline is more often seen in long standing atrial fibrillation. The cardiac stroke volume is reduced by 10-20% during atrial fibrillation, as the 'atrial kick' is missing and because the heart does not have time to fill at the often higher ventricular rate. Causes; age (+- 10% of 70+ year olds and 15% of 90+ year olds have AFIB [1]), ischemia, hyperthyreoidism, alcohol abuse. Risc: thrombo-embolisation of thrombi that form in the atrial caverns as a result of the reduced atrial motion. These thrombi can emblise to the brain and cause strokes.
Atrial fibrillation can be catechorized as follows:
- First documented episode:
- Recurrent atrial fibrillation: after two or more episodes.
- Paroxysmal atrial fibrillation: if recurrent atrial fibrillation spontaneously converts to sinus rhythm.
- Persisting atrial fibrillation: if an episode of atrial fibrillation persists more than 7 days.
- Permanent atrial fibrillation: if atrial fibrillation persists after an effort of electrical or chemical cardioversion
Lone AF is atrial fibrillation in patients younger than 60 years in whom no clinical or electrocardiographic signs of heart or lung disease are present. These patiens have a favourable prognosis regarding thrombo-embolic events.
Non-valvular atrial fibrillation is atrial fibrillation in patients without heart valve disease or heart valve replacement or repair. [2]
References
- Kelley GP, Stellingworth MA, Broyles S, and Glancy DL. Electrocardiographic findings in 888 patients > or =90 years of age. Am J Cardiol. 2006 Dec 1;98(11):1512-4. DOI:10.1016/j.amjcard.2006.06.055 |
- Fuster V, Rydén LE, Cannom DS, Crijns HJ, Curtis AB, Ellenbogen KA, Halperin JL, Le Heuzey JY, Kay GN, Lowe JE, Olsson SB, Prystowsky EN, Tamargo JL, Wann S, Task Force on Practice Guidelines, American College of Cardiology/American Heart Association, Committee for Practice Guidelines, European Society of Cardiology, European Heart Rhythm Association, and Heart Rhythm Society. ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation-executive summary: 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). Eur Heart J. 2006 Aug;27(16):1979-2030. DOI:10.1093/eurheartj/ehl176 |