Atrial Rhythms
Wandering Atrial Pacemaker
| Parameter | Definitions |
|---|---|
| HR | Less than 100 |
| Regularity | Irregular |
| P | At least 3 different P wave shapes |
| QRS | (Mostly) narrow QRS complexes |
| P:QRS Ratio | 1:1 (though some P waves may be difficult to see) |
Wandering Atrial Pacemaker is observed with at least three different P wave shapes. It's named as such due to the theory that the initial electrical impulse is coming from multiple sites in the atria. This results in P waves of varying shapes such as upright, peaked, inverted, broad, notched, etc. The remainder of the cardiac electrical pathway is relatively untouched (so the QRS complexes should appear "normal").
By itself, Wandering Atrial Pacemaker does not produce any other symptoms and treatment is generally not required. The exact mechanism is unclear, but likely related to increased vagal tone.
Multifocal Atrial Tachycardia
| Parameter | Definitions |
|---|---|
| HR | Greater than 100 |
| Regularity | Irregular |
| P | At least 3 different P wave shapes |
| QRS | (Mostly) narrow QRS complexes |
| P:QRS Ratio | 1:1 (though some P waves may be difficult to see) |
Multifocal Atrial Tachycardia is observed with at least three different P wave shapes and a heart rate greater than 100. The mechanism for Multifocal Atrial Tachycardia is similar to Wandering Atrial Pacemaker, but the triggers for it are largely related to some sort of stressor. It is commonly associated with the elderly and with pulmonary disease. The "treatment" for Multifocal Atrial Tachycardia is simply treating the underlying condition.
Multifocal Atrial Tachycardia is commonly confused for Atrial Fibrillation, but it's important to distinguish the distinct P waves in this rhythm and the lack of a fibrillating isoelectric line. Neither antiarrhythmics or electrical cardioversion will "fix" Multifocal Atrial Tachycardia.
If the fast heart rate is presumably causing hemodynamic instability, beta-blockers or calcium-channel blockers could be administered, but they shouldn't be given routinely to all patients with Multifocal Atrial Tachycardia. Primary treatment is to deal with the underlying cause.
Atrial Flutter
| Parameter | Definitions |
|---|---|
| Regularity | Generally regular, QRS may be regular depending on P:QRS ratio |
| P | Sawtooth-like P waves |
| QRS | (Mostly) narrow QRS complexes |
| P:QRS Ratio | More P waves than QRS |
Atrial Flutter is a result of single areas of the atria continuously discharing (due to either spontaneous generation or "short-circuit" loops in the atria). This results in an excessive P-wave rate - often around 200-300 - and showing on the ECG as a "sawtooth" waveline. Because the AV node is still able to filter these impulses, usually every nth P-wave is transmitted through. A ratio of 4:1 would mean that for every 4 P waves, 1 QRS was transmitted through.
Atrial Fibrillation
| Parameter | Definitions |
|---|---|
| Regularity | Irregular |
| P | Fibrillating P wave line |
| QRS | (Mostly) narrow QRS complexes |
| P:QRS Ratio | Not available |
Atrial Fibrillation is a result of multiple areas of the atria continuously discharing (due to either spontaneous generation or "short-circuit" loops in the atria). This results in an excessive P-wave rate - often greater than 500 - and showing on the ECG as a "fibrillating" isoelectric line. However, the AV node is still filtering these impulses coming from the atria, and so the QRS rate is markedly less though still irregular.
Treating Atrial Flutter and Fibrillation
In the emergency department setting, the treatment for atrial flutter and fibrillation is largely the same.
Because the atria are not contracting appropriately, blood may begin to stagnate in the atria and form a thrombus. Thus, in patients where the rhythm may be reversible, converstion of the rhythm may cause the atria to propel the thrombus into the vascular system. For this reason, careful conversion is required and there are many protocols that could be used to help manage these patients. This dictionary will be using the 2021 CAEP Acute Atrial Fibrillation/Flutter Best Practices Checklist for reference.
For patients where "rhythm control" is not feasible (e.g. because their condition is chronic), then rate-control medications such as beta-blockers or calcium-channel blockers are used to ensure the heart rate is at a slower, controlled rate.
Ensure that a cogaulation panel has been done, especially if the osnet of atrial fibrillation was greater than 12-24 hours or if they are already on anticoagulants.
If the atrial fibrillation/atrial flutter is most likely secondary to a medical cause (e.g. significant COPD exacerbation, excessive alcohol consumption), then attempt to treat the underlying cause first!
In the emergency department, Atrial Fibrillation and Atrial Flutter is treated as per ACLS guidelines and an established protocol, such as the 2021 CAEP Acute Atrial Fibrillation/Flutter Best Practices Checklist.