Atrial Tachycardia - Paroxysmal
Atrial tachycardia is a form of supraventricular tachycardia that occurs when one focus in the atria begins to fire rapidly, overwhelming the sinoatrial node.
This results in rapid conduction of action potentials through the atrioventricular node, causing elevated ventricular rates. The atrial rate during atrial tachycardia is usually between 100 and 200 beats per minute. A narrow complex tachycardia results with P wave morphologies that are different than normal sinus P waves. The QRS complex can be wide if aberrancy is present (ie, right or left bundle branch blocks).
Causes of atrial tachycardia include chronic hypertension, congestive heart failure, valvular heart disease and, simply, aging of the heart. Brief atrial tachycardia is seen very commonly on ambulatory ECG monitoring in the elderly and is frequently asymptomatic.
Symptoms of atrial tachycardia depend on the ventricular rate and the duration of the tachycardia. The symptoms include palpitations from the rapid heart rate. If hypotension ensues, dizziness and weakness can occur. The shortened diastolic filling time during tachycardic states can lead to decreased cardiac output and symptoms of congestive heart failure.
Atrial tachycardia is best treated with AV blocking medications, such as beta-blockers or non-dihydropyridine calcium channel blockers. Adenosine can, at times, terminate the rhythm, but not always. Ablation of atrial tachycardia is also an option, especially when medical therapy fails.
Atrial tachycardia with 2:1 block; when atrial tachycardia occurs with a 2:1 conduction block, digoxin toxicity should be considered.