In typical atrial flutter, the depolarizing wavefront courses in either a clockwise or counterclockwise direction around the tricuspid annulus and involves the cavotricuspid isthmus as a critical part of the reentrant circuit. Typical atrial flutter is a form of macroreentrant atrial tachycardia that deserves special mention because it is common, may result in stroke and cardiomyopathy, and is highly amenable to catheter ablation. 12, 13 Left atrial tachycardias often arise from the pulmonary veins, as well as the mitral annulus and left atrial appendage. Right atrial tachycardia often arises from the crista terminalis but can also arise from the tricuspid annulus, compact atrioventricular node, and coronary sinus ostium. Both focal and macroreentrant atrial tachycardia may result from prior structural heart disease or surgery for congenital heart disease, may follow surgical or catheter ablation of atrial fibrillation, or may be due to idiopathic phenomena. Note that the term macroreentrant atrial tachycardia is synonymous with the term atrial flutter. Macroreentrant atrial tachycardia results from a large intraatrial reentrant loop >2 cm in length. Focal atrial tachycardia results in a centrifugal wavefront spread throughout the atria from a focus of (1) enhanced automaticity, (2) triggered activity, or (3) a small area of reentry (microreentry). The term atrial tachycardia describes a group of atrial arrhythmias whose mechanisms may be focal or macroreentrant. Triggered activity is also implicated in the initiation of atrial fibrillation. Triggered activity can occur in response to augmentation of intracellular calcium (eg, with cardiac glycosides) and is the mechanism of approximately 30% of focal atrial tachycardias. 4Īutomatic arrhythmias and arrhythmias caused by triggered activity are relevant because in addition to being the mechanisms of sustained arrhythmias, short bursts of these arrhythmias are triggers for reentrant SVTs.Īrrhythmias due to triggered activity are caused by extra depolarizations immediately following cellular repolarization (called delayed afterdepolarizations) that may result in extrasystoles and sustained tachyarrhythmias. Automatic foci are the mechanisms of more than 70% of cases of focal atrial tachycardia. Automaticity can occur in the setting of electrolyte abnormalities, changes in autonomic tone, and other local factors, many of which are not understood.

These foci of myocardial tissue exhibit pathologic changes in resting membrane potential and can develop the capacity to depolarize rapidly and become the dominant rhythm. The term automaticity refers to the phenomenon of spontaneous tachycardia arising from a group, or focus, of cells and can result in atrial and ventricular arrhythmias. Enhanced automaticity and triggered activity may cause the initiation of reentry. Atrial arrhythmias include atrial tachycardia, atrial flutter, and fibrillation and may be because of reentry, automaticity (star), or triggered activity (T) (far right). Atrioventricular nodal reentrant tachycardia (far left) and atrioventricular reciprocating tachycardia (middle) are exclusively reentrant in mechanism. The figures demonstrate the mechanisms of arrhythmia. Subtypes of supraventricular tachycardia. The incidence of atrial tachycardia increases with age and is more common in patients with structural heart disease. AVRT is more common in men and has a mean onset age of 23 years. AVNRT is more common in women and has a bimodal age distribution with one peak in the third decade and another that begins in the sixth decade and extends to very old age.

The subtypes atrioventricular reentrant tachycardia (AVRT) and atrial tachycardia account for approximately 30% and 10% of SVT cases, respectively.

Of the remaining subtypes of SVT, atrioventricular nodal reentrant tachycardia (AVNRT) is the most common, accounting for approximately 60% of cases. 1 Atrial fibrillation and atrial flutter are the most common subtypes of SVT, affecting approximately 2 million patients in the United States. The incidence of SVT is approximately 35 cases per 100,000 patients with a prevalence of 2.25 cases per 1,000 in the general population. SVT is a common entity in clinical practice and a relatively common occurrence in the emergency department.

Atrial flutter vs svt