Atrial tachycardia can be characterized as focal and multifocal.

Focal Atrial Tachycardia
Focal atrial tachycardia (focal AT) is fast and usually regular, discharging from a discrete focus of origin. It may be sustained or nonsustained. The atrial rate is usually 100-250 beats per minute (bpm).

The origin of focal AT is most commonly from the right atrium. Other identified origins are the atrial free wall (right more common than left), the atrial appendages, the crista terminalis, the tricuspid annulus, the mitral annulus, the paraseptal areas, the pulmonary veins, the prenodal areas, the coronary sinus, and the coronary cusps. The underlying electrophysiological mechanism can be either automatic, triggered, or micro-reentry. Sinus node reentry tachycardia is an uncommon type of focal AT in which micro-reentry originating from the sinus node results in P waves that are indistinguishable from those of normal sinus rhythm.

Etiologies include conditions that increase atrial pressure such as hypertension, cardiomyopathy, acute myocardial infarction, and pulmonary disease, as well as infection, hypokalemia, hypoxia, theophylline, digitalis toxicity, and stimulants such as cocaine. It may also be seen after catheter ablation for atrial fibrillation. Rarely, speech-induced tachycardia occurs. Some cases are idiopathic. AT in the absence of underlying heart disease is generally benign.

Most patients present with abrupt onset of palpitations described as a rapid fluttering sensation in the chest or neck. Rarely, patients may present with syncope, particularly if the ventricular rate exceeds 200 bpm. Patients with underlying cardiac disease (eg, heart failure, coronary disease) can present with symptoms consistent with worsening of their underlying heart disease such as dyspnea or chest pain.

Focal AT accounts for approximately 3%-17% of cases referred for supraventricular tachycardia (SVT) ablation. Nonsustained focal AT is common and does not necessitate treatment.

Incessant AT, generally considered that which is present for a prolonged period of time and accounts for at least 90% of total time on ECG monitoring, is sometimes seen in children and young adults, as well as some patients with organic heart disease. It may lead to tachycardia-induced cardiomyopathy.

Multifocal Atrial Tachycardia
Multifocal atrial tachycardia (MAT) is an uncommon, fast, irregular arrhythmia arising from multiple sites of the atrium, resulting in at least 3 distinct P-wave morphologies on ECG.

The most common etiologies for MAT are associated with right atrial distension, including chronic obstructive pulmonary disease (COPD), pulmonary hypertension, coronary artery disease, decompensated heart failure, and valvular heart disease. Other causes include chronic kidney disease, sepsis, postsurgical state, hypokalemia, hypomagnesemia, and drugs such as isoproterenol, aminophylline, and theophylline therapy.

In cases with underlying comorbidities, MAT is often an incidental finding with symptoms related to worsening of underlying pulmonary or cardiac disease including shortness of breath, cough, and/or fatigue. Occasionally, patients will report associated palpitations.

Incidence of MAT ranges from 0.05%-0.32% of ECGs. The mean age of presentation is approximately 70 years of age. Patients are generally elderly and quite ill with an in-hospital mortality rate of 40%-60% due to death from pulmonary, cardiac, or other serious diseases.