Atrial tachycardia and other ectopic atrial rhythms occur when a site outside of the sinus node, but within the atria, creates action potentials faster than the sinus node. This ectopic focus becomes the predominant pacemaker of the heart. When the atrial rate is greater than 100 beats per minute, the rhythm is atrial tachycardia. If less than 100 beats per minute, then the term “ectopic atrial rhythm” is used.
Because the origination of this electrical activity is not from the sinus node, the P wave would not have its normal sinus appearance ― that is, upright in lead II and biphasic in V1. However, it would have a different morphology depending on exactly where it originates. This is referred to as an “ectopic atrial rhythm” or “ectopic P wave.”
Ectopic P waves are also commonly seen in multifocal atrial tachycardia, or MAT, wandering atrial pacemaker, and premature atrial contractions, or PACs.
Atrial tachycardia is quite common. The 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, and 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 nondihydropyridine calcium channel blockers. Adenosine can terminate the rhythm at times, but not always. Ablation of atrial tachycardia is also an option, especially when medical therapy fails.
Special Situations – Ectopic Atrial Rhythms
Atrial Tachycardia with 2:1 Block. When atrial tachycardia occurs with a 2:1 conduction block, digoxin toxicity should be considered.
1. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
2. Surawicz B, et al. AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the Electrocardiogram. Circulation. 2009; doi:10.1161/CIRCULATIONAHA.108.191095.