see also: [[Atrial fibrillation]], [[SVT]] > [!key points] > - Atrial fibrillation and [[Atrial Flutter]] are both caused by macro reentry circuits occurring within the atrial myocardium. In **flutter**, the re-entering impulse cycles around a single circuit, resulting in regular "sawtooth" flutter waves In atrial fibrillation the reentering impulses cycles around multiple circuits, resulting in irregular fibrillory waves. > - length of re-entry circuit corresponds to *size or right atrium*, resulting in fairly predictable atrial rates ~300 BPM. ventricular rate determined by degree of physiological block occuring at AV node. most is 2:1 (vent rate 150), but can have 3:1 or 4:1 if disease of conducting system or antiarrhythmic drug therapy. usually would need WPW or sympathetic stimulation to get 1:1 flutter > lower risk of stroke than atrial fibrillation **Causes** → essentially any disorder that can cause atrial fibrillation can cause flutter - primary electrical disorders (usually young patients) - IHD including ACS - valvular heart disease, especially *mitral valve* - HTN - cardiomyopathy / CHF - chronic pulm disease (COPD) - PE - pericardial disease - [[hypokalemia]] - [[Hypothermia]] - myocarditis - myocardial contusion - sepsis - alcohol and caffeine | | AVNRT | Atrial flutter | | --------------- | ----------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------ | | pathophysiology | functional re-entrant circuit within AV node | re-entrant circuit in right atrium leading ot atrial rate of ~ 300 BPM and ↑ ventricular rate dependent on AV conduction | | ECG | - rate 140 - 240<br>- retrograde p waves, especially II, III, aVF | - regular atrial activity at 300 BPM<br>- vent rate often ~150<br>saw tooth pattern of inverted p waves, espec inferior | | Causes | - idiopathic<br>- stimulants, coffee, drugs | HTN, lung disease, obesity, PE | | ED Tx | - vagal manoevres<br>- adenosine 6mg IV<br>- verapamil 5mg IV | IV beta blockers (eg metoprolol)<br>treat underlying cause | > avoid 1a (quindine, procainamide) and 1c (flecainide) in flutter