Atrial tachycardia (AT) is a supraventricular rhythm originating in the atria outside of the SA node at a rate between 120 and 250 bpm.
- Digitalis toxicity
- Valvular (especially rheumatic) heart disease
- Coronary Artery Disease
- Acute Myocardial Infarction
- Electrolyte disturbances
- Regular rhythm (equal R-R intervals)
- Atrial rate 120-250 bpm (equal P-P intervals)
- Conduction is commonly 1:1 (one P wave for every QRS complex). However, conduction may be 2:1 or greater (> or = 2 Pwaves for every QRS complex with an isoelectric baseline between successive P waves), especially in the presence of digitalis toxicity. This phenomenon is sometimes called atrial tachycardia with AV block. The abnormal conduction ratios (2:1, 3:1. and so on) that often accompany digitalis toxicity reflect drug-induced conduction block (digitalis inhibits conduction through AV node) as well as efforts by the AV node to triage the impulse that are bombarding it.
- PR interval short when conduction through the AV node is 1:1. The speed of conduction through the AV node accelerates as the rate increases, thereby shortening the PR interval.
- P wave morphology is often different from that seen in normal sinus rhythm (NSR). At faster rates, the ectopic P waves may be difficult to see and may distort the T wave of the preceeding beat. Leads II, III, aVF, and V1 should be examined properly for their presence.
- The shape of QRS is unchanged from that seen during NSR unless conduction in the ventricles is disturbed.
- AT may occur in paroxysms (bursts); when it terminates, there may be a long pause before NSR resumes.
- Withhold digoxin
- Treat underlying heart disease
- Correct electrolyte abnormalities such as hypokalemia and hypomagnesemia that commonly accompany this dysrhythmia during digitalis toxicity.