Infraatrial Supraventricular Tachycardias: Mechanisms, Diagnosis, and Management

Abstract

Tachycardias are traditionally classified as either ventricular tachycardia (VT) or supraventricular tachycardia (SVT). VT can be defined as a tachycardia which requires only ventricular structures for perpetuation. SVT is defined in terms of exclusion of VT and hence is any tachycardia which requires participation of at least one supraventricular structure for perpetuation. Certain SVTs require only participation of the atrioventricular node (AVN) and the His bundle (HB) but not the atrial myocardium or any of the great thoracic veins for perpetuation and hence can be described as "infraatrial." The three main mechanisms of infraatrial SVTs are: (1) intranodal atrioventricular reentrant tachycardia; (2) junctional ectopic tachycardia; and (3) nodoventricular reentrant tachycardia. The clinical significance of infraatrial SVTs is that they are compatible with any A:V ratio and even atrioventricular (AV) dissociation. Infraatrial SVTs are often suspected when a narrow complex tachycardia presents with apparent AV dissociation and a counterintuitive A:V ratio of < 1:1. However, if the same tachycardia is conducted with aberrant conduction or preexcitation, a broad complex tachycardia with an A:V ratio of < 1:1 will arise and that can be easily mistaken for VT. The possible patterns of electrical association and dissociation between different cardiac structures are examined, and how individual types of infraatrial SVT can be diagnosed and managed are reviewed.

Narrow QRS tachycardia in a patient with old infarction. What Is the mechanism?

“…Postablation, tachycardia was rendered noninducible, even with isoproterenol infusion and triple extra‐stimuli. An HV interval that is shorter during tachycardia compared to sinus rhythm implies retrograde activation of His with the rare exception of intra‐Hisian reentry due to longitudinal dissociation within the His bundle . However, PPs along the inferior septum preceded His activation by 25 milliseconds, which substantiates retrograde capture of His bundle.…”

Magnesium Lowers the Incidence of Postoperative Junctional Ectopic Tachycardia in Congenital Heart Surgical Patients: Is There a Relationship to Surgical Procedure Complexity?

“…Intracellular disruption of mitochondria and sarcoplasmic reticulum function increases intracellular calcium levels, impairing diastolic relaxation, and results in dysfunction of the conduction system [12]. These physiologic disturbances in turn can enhance automaticity or result in triggered activity from an ectopic focus within the atrioventricular node or His bundle [10, 21], particularly in high catecholamine states (which occurs following milrinone and dopamine administration).…”

Repetitive Irregular Narrow and Wide‐Complex Tachycardia: What Is the Mechanism?

“…The differential diagnosis of this tachycardia includes other causes of infraatrial supraventricular tachycardia (SVT) as described by Lau. 1 These include junctional ectopic tachycardia, intraHisian reentry, and AVNRT with apparent VA block. Infraatrial SVTs should be suspected when a narrow complex tachycardia occurs with an A:V ratio of <1:1.…”