Repeat accessory pathway ablation: Challenges, surprises, and lessons learned

Postpacing interval (PPI) after right ventricular (RV) pacing entrainment minus tachycardia cycle length (TCL) with a correction for atrioventricular (AV) node delay (corrected PPI-TCL) was useful to differentiate atrioventricular node reentrant tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT). However, the value of corrected PPI-TCL in determining the site of the accessory pathway (AP) in ORT has not been investigated. The purpose of this study was to assess whether the corrected PPI-TCL is useful in differentiating ORT using a left-sided AP from a right-sided AP. We studied 52 patients with ORT using a left-sided AP and 13 patients with a right-sided AP. The PPI was measured upon cessation of the RV pacing at a cycle length 10-40 ms shorter than the TCL. The corrected PPI-TCL was calculated from the subtraction of the increment in AV nodal conduction time of the first PPI from the PPI-TCL. The mean corrected PPI-TCL was 83 ± 20 ms in patients with ORT using a left-sided AP and 27 ± 19 ms in patients with a right-sided AP (P ≤ 0.001). All patients with ORT using a left-sided AP except three patients with left septal AP and none of the patients with ORT using a right-sided AP had a corrected PPI-TCL > 55 ms. The corrected PPI-TCL after the RV pacing entrainment is useful to guide differentiating ORT using a left-sided AP from a right-sided AP.

Comparative effects of adenosine triphosphate on accessory pathway and atrioventricular nodal conduction

Another Way to Prove the Presence and Participation of an Accessory Pathway in Supraventricular Tachycardia?

Measurement of the ventriculoatrial interval from the coronary sinus during para-Hisian pacing may fail to distinguish ventriculoatrial nodal conduction from conduction over a septal accessory pathway

Four patients with left-sided accessory pathways (APs) and unusual coronary sinus (CS) received radiofrequency ablation. Unusual CS included occlusion of CS (patient 1), acute angulation of proximal CS (patients 2 and 3), and narrowing of CS orifice and proximal segment (patient 4). CS catheterization and AP mapping along the CS could not be performed in the four patients. Radiofrequency ablation by left ventricular retrograde technique for the manifest left posteroseptal AP (patient 1), concealed left posterior AP (patient 2), and transseptal left atrial technique for the manifest left posteroseptal AP (patient 3) and manifest left posterior AP (patient 4) were performed successfully without CS catheter guidance. This study suggests that radiofrequency ablation of left-sided AP with unusual CS is feasible by some special techniques.

Para-Hisian pacing: Useful clinical technique to differentiate retrograde conduction between accessory atrioventricular pathways and atrioventricular nodal pathways

BackgroundThe differential diagnosis of supraventricular tachycardias (SVTs) is essential during radiofrequency‐(RF) ablation. The extracardiac vagal stimulation (ECVS), introduced in 2015, offers new insights for electrophysiological studies and ablation, allowing controlled cardiac vagal effect.MethodsProspective study of 625 SVT ablation patients. ECVS was performed using a regular electrophysiology catheter to study atrioventricular (AV) and ventriculo‐atrial (VA) conduction and their effects on tachycardia. Baseline ECVS was performed to determine the optimal position for right or left ECVS, near the jugular foramen. ECVS was repeated during atrial and ventricular pacing (VP) to monitor the procedure's progression and ensure successful endpoints.ResultsECVS was successful in 611/625 patients (98%), 381 (62.3%) had AV node reentry tachycardia‐(AVNRT), and 230 (37.6%) accessory pathway (AP), including 135‐(58.7%) anterograde AP (WPW) and 95 (41.3%) concealed AP. ECVS + VP in 33 patients with atypical AVNRT yielded VA block in 32‐(97%), suggesting VA conduction solely via the AV node. In contrast, 57 patients with concealed para‐septal AP maintained VA conduction during ECVS, confirming AP. ECVS proved to be a fast, reliable, and practical additional EP tool: VA block indicated AVNRT, while persistent VA conduction suggested AP. Additionally, ECVS was highly effective in revealing and confirming successful AP ablation by demonstrating the absence of AV and VA anomalous conduction.ConclusionECVS was a valuable tool in the diagnosis and ablation of SVTs. It allowed reproducible AV and VA block through normal pathways, easily identifying AVNRT and concealed, intermittent, or subtle AP. It was particularly useful in complex cases involving concealed AP and atypical AVNRT tachycardia.

During retrograde conduction through an accessory pathway (AP) or the atrioventricular (AV) node, earlier activation of the distal recording site than a more proximal site of the coronary sinus (CS) generally indicates retrograde conduction via a distally located AP. Thus, after successful ablation of a left-sided AP, if the distal CS recording site is activated earlier than a more proximal site retrogradely, it is considered to suggest-in the absence of His-bundle recording or more frequently in the setting of poor recording of the low septal right atrial electrogram-a conduction via a second AP (located more distally), and not conduction via the AV node. Yet, we hypothesized that retrograde conduction through the AV node may activate the far distal site of the CS (CSD) earlier than a more proximal site, as the anterior atrial wavefront, coming retrogradely from the AV node and traveling along the anterior mitral annulus, could reach the CSD earlier than a more proximal site. To test this we studied 18 patients with intact retrograde conduction via the AV node, but without evidence of an AP. The CSD was recorded by means of a quadripolar catheter (interelectrode distance of 2-5 mm); retrograde activation sequence at the distal (CSD1-2) versus proximal (CSD3-4) bipolar recording site was determined during ventricular stimulation. In 12 of 18 patients the CSD1-2 recording site was activated 5-10 ms earlier than the CSD3-4 recording site, in 3 of 18 patients the CSD1-2 site was activated 5 ms later than the CSD3-4 site; in the remaining 3 patients both recording sites were depolarized simultaneously. The results indicate that the CSD was often depolarized earlier than a more proximal site by impulses that conducted to the atria retrogradely via the AV node while the quadripolar recording catheter was placed at the CSD. This observation, although not well documented previously, suggests that the sequence of retrograde atrial activation in the CS should be studied carefully in consideration of the actual location of the mapping catheter in order to correctly diagnose the presence or absence of conduction via an AP.

Percutaneous solution for a frequent complication after transcatheter aortic valve replacement: A case of atrioventricular leadless pacemaker implantation after transcatheter aortic valve replacement

Managing atrial fibrillation in the CRT patient: Controversy or consensus?

A surface electrocardiogram of a sixty-year old woman showed typical delta waves of type-A at a sinus rhythm, and a narrow QRS duration during tachycardia at a rate of 150. Electrophysiologic studies were performed. Right ventricular apical pacing showed a ventriculoatrial (VA) conduction with the shortest interval of 37 msec recorded at coronary sinus of lateral side of mitral annulus. This VA conduction had no decremental property, and the retrograde atrial activation sequence was the same as that during atrioventricular tachycardia. Via a transaortic approach, an anterograde accessory pathway located at the left lateral side of mitral annulus was ablated at a sinus rhythm, when delta waves on electrocardiogram disappeared. However, a narrow QRS tachycardia with longer VA conduction interval but with the same atrial activation sequence as clinical tachycardia was induced. Right ventricular pacing at a sinus rhythm showed the same atrial activation sequence as seen in the tachycardia. This VA conduction interval was elongated by 50 msec compared with that recorded before anterograde accessory pathway ablation. The VA conduction was blocked with a 10-mg infusion of adenosine and furthermore, showed decremental property by ventricular extra stimuli. Finally, this retrograde conduction pathway was ablated at a similar lateral side of the mitral annulus.

During ventricular pacing, a fusion of atrial activation may occur owing to the simultaneous retrograde conduction of the atrioventricular (AV) node and accessory pathway (AP), potentially leading to an inaccurate mapping of the atrial AP insertion site. We tested the hypothesis that landiolol, an ultra-short-acting intravenous β1-blocker, could dissociate a fusion of atrial activation. We conducted a prospective before-and-after study to investigate the effect of landiolol on retrograde conduction via the AV node and AP. We enrolled 21 consecutive patients with orthodromic AV reciprocating tachycardia who underwent electrophysiological studies at our hospital between January 1, 2018, and August 31, 2020. Six patients exhibited a fusion of atrial activation. After landiolol administration (10 μg/kg/min), the effective refractory period was unchanged in AP (280 [240-290] ms vs. 280 [245-295] ms, p = .91), whereas that of the AV node was prolonged (275 [215-380] ms vs. 332 [278-445] ms, p = .03). The Wenckebach pacing rate via retrograde AV node decreased after landiolol administration (180 [140-200] beats per minute [bpm] vs. 140 [120-180] bpm, p = .02). Thus, landiolol decreased the minimum ventricular pacing rate required to dissociate a fusion of atrial activation (180 [160-200] bpm vs. 140 [128-155] bpm, p = .007). Radiofrequency catheter ablation under landiolol administration successfully eliminated AP in all patients during ventricular pacing without complications or recurrence. Landiolol inhibited the AV node without affecting the AP and helped dissociate a fusion of atrial activation at a lower ventricular pacing rate.

We present four patients with the Wolff-Parkinson-White syndrome who exhibited retrograde supernormal conduction or gap phenomenon in concealed accessory pathways. In the first patient, ventricular extrastimulus testing revealed retrograde block at the coupling interval of 520 msec and reappearance of conduction at the coupling interval of 370 msec. In a second patient, 1:1 retrograde conduction was not present but supernormal conduction was demonstrated at coupling intervals of 360 msec to 310 msec during the ventricular extrastimulus testing when the basic drive consisted of atrioventricular (AV) simultaneous pacing. In a third patient, ventricular extrastimulus testing demonstrated retrograde conduction through the accessory pathway only at coupling intervals of 400 msec to 360 msec. In a fourth patient, retrograde block occurred at the coupling interval of 340 msec and retrograde "slow" conduction reappeared at coupling intervals of 300 msec to 250 msec (gap phenomenon) only when the basic drive consisted of AV simultaneous pacing. Thus, concealed accessory pathways may exhibit retrograde supernormal conduction or gap phenomenon. Ventricular extrastimulus testing consisting of AV simultaneous pacing during the basic drive may facilitate demonstration of these unusual properties.

Clinical Case: A 51 year old male with a history of hypertension, G6PD deficiency, thrombotic thrombocytopenic purpura, prior stroke, and morbid obesity presented with resuscitated out of hospital VF arrest. Electrolytes and ECG were normal. During his admission, the patient had two VF events that were induced by what appeared to be a short coupled right bundle branch block (RBBB) morphology PVC. He was brought to the electrophysiology lab for PVC ablation and ICD implantation. Baseline rhythm was sinus with what appeared to be both RBBB morphology PVCs and junctional extrasystoles. With both extrasystoles, the His potential preceded the QRS by 50 ms, and atrial activation in the His catheter and coronary sinus catheter was also earlier than the QRS. Activation mapping of the right bundle showed later activation than the His potential. This was all consistent with junctional premature complexes (JPC) with frequent RBBB aberrancy rather than fascicular PVCs. Slow pathway modification was performed to attempt to ablate the JPCs. After multiple ablations along the tricuspid annulus and back to the coronary sinus os that triggered slow junctional beats, the patient’s JPC burden was significantly reduced. An ICD was also implanted. The patient was discharged on flecainide. At 4 month follow up he had not had recurrence. Discussion: Early coupled PVCs are a well-known cause of ventricular fibrillation, but JPCs inducing VF have not been described previously. Placement of a coronary sinus and His catheter helped identify early that this was not simply a fascicular PVC. This case demonstrates the importance of keeping a broad differential diagnosis when starting any EP study. Ablating the slow pathway area can be effective to treat JPCs while preserving native AV conduction as demonstrated in this case.

A 23-year-old asymptomatic male patient was admitted for invasive evaluation of pre-excitation on the surface ECG persisting during exercise testing. The electrophysiological study, performed under sedation with midazolam, revealed a midseptal accessory pathway (AP) with retrograde conduction and a 1:1 conduction during atrial pacing up to a cycle length of 240 ms. No tachycardia could be induced during pacing of the atrium and ventricle. We opted for ablation of the AP due to the malignant anterograde characteristics. Two seconds after the delivery of the first application of radiofrequency energy, the delta wave disappeared and normal atrioventricular conduction was restored. Energy application was continued for an additional 58 seconds. One day after the procedure, a control ECG revealed recurrence of the pre-excitation pattern. A second invasive evaluation was, therefore, scheduled 1 week after the initial electrophysiological study. Surprisingly, the surface ECG was normalized at that time, with AH and HV intervals within normal …