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Cardiovascular Disease
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Two atrial tachycardias are caused by automaticity: atrial tachycardia and junctional tachycardia. The other narrow QRS tachycardias are caused by re-entry circuits and are known as reciprocating tachycardias.
Ablation of SVT (AVNRT and AVRT)
Published in Andrea Natale, Oussama M. Wazni, Kalyanam Shivkumar, Francis E. Marchlinski, Handbook of Cardiac Electrophysiology, 2020
Kushwin Rajamani, Patrick Tchou
Damage to the compact AV node or His bundle can occur if RF energy was delivered in anatomic sites near them. In such cases, positioning of the catheter at the slow pathway region is usually not very stable. Changes of position can occur readily with heart beat movement or with breathing. Thus, close monitoring of the catheter position during RF application is important in minimizing this complication. The presence of a faster accelerated junctional tachycardia, PR prolongation, and/or retrograde block of junctional ectopy during RF application are markers predictive of complete permanent AV block.7 Abrupt PR or AH interval lengthening during RF ablation should be a warning that the RF lesions are being applied closer to the fast pathway than the slow pathway. RF application should be stopped immediately. Transient AV block that occurs during RF ablation usually indicates that the targeted site may be dangerously close to the compact AV node, especially if the block persists for a short period of time after termination of RF application. Prolongation of the PR Interval may persist for a variable amount of time. However, even if antegrade conduction reverts to baseline after an observation period, the patient should be observed post procedure for 24–48 h to assure that later development of AV block does not occur, possibly related to edema from the heated tissues. In these circumstances, a short course of corticosteroids may be helpful in minimizing inflammation and edema at the ablated tissue.
Bioelectric and Biomagnetic Signal Analysis
Published in Arvind Kumar Bansal, Javed Iqbal Khan, S. Kaisar Alam, Introduction to Computational Health Informatics, 2019
Arvind Kumar Bansal, Javed Iqbal Khan, S. Kaisar Alam
In Junctional tachycardia, electrical activities arise around the AV-node and above the bundle of His. Atria and ventricles get depolarized concurrently, making P-wave in inferior leads (leads II, III and AVF) negative. PR-interval is negligible, and many times P-waves are embedded in or trail QRS-complex. The QRS-complex is usually narrow. Markov model-based analysis shows that negative P-wave with short PR-interval occurs 86% of the times, and 14% of the times P-wave is embedded in the QRS-complex or occurs after QRS-complex. The waveform for junctional tachycardia is shown in Figure 7.12d.
Interesting case of 2:1 tachycardia to 1:1 tachycardia
Published in Acta Cardiologica, 2020
Krishna Kumar Mohanan Nair, Narayanan Namboodiri, Debasish Das, Ajitkumar Valaparambil
A 19-year-old female underwent an electrophysiology study for paroxysmal palpitation. Figure 1(A) represents selected surface electrocardiogram and intracardiac electrograms showing narrow QRS tachycardia with 2:1 AV relation transforming to 1:1 AV conduction following a ventricular premature beat (VPB) delivered from RV apex. The A-A interval, H-H interval and retrograde atrial activation sequence during 2:1 AV conduction and 1:1 AV conduction remained the same. Figure 1(B) represents atrial premature beat (APB) delivered during the narrow QRS tachycardia. The APB has delayed the next H-H interval without affecting the immediate H-H interval. The differentials of a regular narrow QRS A on V tachycardia include typical AV nodal re-entrant tachycardia (AVNRT) and junctional tachycardia (JT). In response to the APB, the next tachycardia beat has delayed without affecting the immediate H-H interval. This confirms the mechanism as AVNRT. During AVNRT, a late coupled APB can conduct antegradely over the slow AV nodal pathway and can affect the next beat of tachycardia resulting in either advancement or delay of the next His or termination of tachycardia [1]. A late coupled APB finds the AV node refractory during JT and hence will not be able to conduct through it. Hence a late coupled AES has no effect on timing of next His in JT. The 2:1 AV conduction might be due to functional block at any level with in the His bundle or infrahisian conduction system as suggested by the ventricular ectopic improving the conduction to 1:1 [2]. Patient underwent successful slow pathway ablation.