Limitations of ventricular pacing maneuvers to differentiate orthodromic reciprocating tachycardia from atrioventricular nodal reentry tachycardia.

PURPOSE: Various ventricular pacing maneuvers have been developed to differentiate orthodromic reciprocating tachycardia (ORT) from atrioventricular nodal reentry tachycardia (AVNRT). We aimed to evaluate the diagnostic value of ventricular pacing maneuvers in patients undergoing catheter ablation for AVNRT/ORT. METHODS: Sixty patients with supraventricular tachycardia (SVT) undergoing invasive EP study were included (ORT: 31, typical AVNRT: 18, atypical AVNRT: 11). Ventricular overdrive pacing (VOP) and resetting by premature ventricular stimulation (PVS) during SVT were analyzed by 3 independent observers blinded to the ultimate diagnosis. We determined intraclass correlation coefficient (ICC) for interobserver agreement and the diagnostic accuracy of consensual results. RESULTS: Although specificity of all parameters was high (96-100%) for ORT, semi-quantitative parameters of VOP (requiring the recognition of specific ECG patterns) had lower interobserver reliability (ICC: 0.32-0.66) and sensitivity (16.1-77.4%). In contrast, most quantitative measurements of VOP and PVS showed good reproducibility (ICC: 0.93-0.95) and sensitivity (74.2-89.3%), but post-pacing interval after VOP needed correction with AV nodal conduction slowing. False negative results for diagnosing ORT were more common with left free wall vs. right free wall or septal, and slowly vs. fast-conducting septal APs. False positivity was only seen with a bystander, concealed nodo-fascicular/nodo-ventricular (NF/NV) AP in a case of AVNRT. CONCLUSIONS: No single maneuver is 100% sensitive for ORT. Semi-quantitative features have limited reproducibility and all parameters can be misleading in the case of rate-dependent delay during VOP/PVS, ORT circuits remote from the pacing site, or a bystander, concealed NF/NV AP.

Unchanged QRS morphology with atrial pacing in a case of WPW syndrome: What is the mechanism?

We present the case of a 55-year-old female who presented for a short episode of palpitation and an electrocardiogram consistent with Wolff-Parkinson-White syndrome. She underwent an electrophysiological study showing that during incremental atrial pacing and extrastimulation the stimulus to QRS and QRS morphology stayed constant while the His to ventricular (HV) interval shortened. What can be the explanation for the constant QRS morphology, despite shortening HV during atrial pacing?

Is adenosine useful for the identification of atrial fibrillation triggers?

INTRODUCTION: Both isoproterenol (Iso) and adenosine (Ado) are used to induce atrial fibrillation (AF) in the electrophysiology lab. However, the utility of Ado has not been systematically established. OBJECTIVE: The purpose of this study was to compare Ado to Iso for the induction of paroxysmal AF. METHODS: Forty patients (16 women; mean age, 60 ± 12 years) with paroxysmal AF, presenting for ablation were prospectively included of whom 36 (90%) received Ado (18-36 mg) and/or Iso (3-20 µg/min incremental dose) in a randomized order (26 [72%] received both drugs). RESULTS: AF was induced with Iso in 15 of 32 (47%) and with Ado in 12 of 30 (40%) patients (P = 0.9). Iso-triggered AF started from the left pulmonary veins (PVs) in 11 of 15 (73%), from the right PVs in 3 of 15 (20%), and from the coronary sinus (CS) in 1 of 15 (7%) cases. Ado-induced AF episodes originated from the left PVs in 6 of 12 (50%), from the right atrium (RA) in 4 of 12 (33%), and from the CS in 2 of 12 (17%) cases. Altogether, Iso-induced AF was more likely initiated from the PVs (93%) compared with Ado (50%) ( P = 0.02). Ado-induced non-PV triggers were not predictive of arrhythmia recurrence after PV isolation. CONCLUSION: Ado much more frequently induces non-PV triggers, especially from the RA. The clinical significance of these foci, however, is questionable.

Association between dissociated firing in isolated pulmonary veins and the initiation and maintenance of atrial fibrillation.

BACKGROUND: Whether dissociated firing (DiFi) in isolated pulmonary veins (PVs) implies arrhythmogenicity of the particular PVand, therefore, a better outcome of PV isolation (PVI) for paroxysmal atrial fibrillation (PAF) is debated. METHODS: Thirty-one patients undergoing their first PVI for PAF were studied. Isoproterenol was infused for induction, and the triggering PV was identified. During sustained PAF, sequential recordings were made with a decapolar circular mapping catheter from each PV. The dominant frequency (DF) was determined using fast Fourier transformation. Spontaneous DiFi was monitored for 30 min after PVI. RESULTS: PAF was triggered by the PVs in all patients. Fourteen (45 %) patients had DiFi after PVI in at least one PV. It was recorded most commonly from the left upper (84 %) and lower (67 %), less commonly from the right upper (31 %) PV. Out of the 23 PVs with DiFi, 13 (57 %) showed sporadic ectopic beats while 10 (44 %) had sustained ectopic rhythm or isolated tachycardia. There was no difference in size between PVs with or without DiFi (5.9±1.2 vs. 5.6±1.0 cm ostial perimeter, p=0.40). Triggering PVs more commonly showed any DiFi, compared to nontriggering PVs (68 vs. 27 %, p=0.003) and more commonly had sustained DiFi (53 vs. 0 %, p<0.001). During PAF PVs with any DiFi showed faster maximal DF compared to PVs without DiFi (7.1±1.3 vs. 5.9±1.1 Hz, p=0.001). Higher maximal DF was recorded in PVs with sustained versus sporadic DiFi versus PVs without DiFi (7.5 ±0.9 vs. 6.8±1.6 vs. 5.9±1.1 Hz, respectively, p=0.002). Patients with DiFi after PVI had a longer mean time to recurrent PAF compared to those without DiFi (52 vs. 32 months, p=0.048). CONCLUSIONS: Dissociated firing in isolated PVs is associated with their role in the initiation and maintenance of PAF.

Impaired adaptation to left atrial pressure increase in patients with atrial fibrillation.

BACKGROUND OR PURPOSE: Episodes of left atrial (LA) pressure increase predispose to atrial fibrillation (AF). The adaptation of LA mechanical function and electrophysiology to pressure elevation in healthy adults, and in patients with AF, is largely unknown. METHODS: Eleven patients with left-sided accessory pathway (controls) and 16 patients with paroxysmal AF undergoing catheter ablation were studied. LA pressure (LAP) was recorded through transseptal catheterization, while speckle tracking-derived peak LA longitudinal strain (PALS) was measured using transthoracic echocardiography. Stiffness index (SI) was calculated as mean LAP/PALS. Effective refractory period (ERP) of the LA was determined during simultaneous atrioventricular (AV) pacing and during atrial pacing. RESULTS: At baseline, AF patients had higher LA pressure (mean LAP 8.3 ± 4.7 vs. 5.1 ± 3.1 mmHg, p = 0.048), reduced LA mechanical function (PALS 15.1 ± 5.1 vs. 21.6 ± 6.2 %, p = 0.006, SI 0.69 ± 0.75 vs. 0.28 ± 0.22, p = 0.015), and longer LA ERP (242.3 ± 33.4 vs. 211.7 ± 15.6 ms, p = 0.017). Mean LAP was increased to the same extent by AV pacing in controls and AF patients (mean change 12.6 ± 7.4 vs. 12.6 ± 7.5 mmHg, p = 0.980). At the same time PALS decreased (from 15.1 ± 5.1 to 11.6 ± 3.3 %, p = 0.008), SI increased (from 0.69 ± 0.75 to 1.29 ± 1.17, p < 0.001) and ERP shortened (from 242.3 ± 33.4 to 215.9 ± 26.3 ms, p = 0.003) in AF patients, while they remained unchanged in controls. CONCLUSIONS: The stiffened LA in patients with AF responds to acute pressure elevation with an exaggerated increase in wall tension and decrease in ERP, which is not seen in the normal LA. This may underlie the propensity for AF during episodes of atrial stretch in these patients.

Very Long-Term Results Of Atrial Fibrillation Ablation Confirm That This Therapy Is Really Effective.

Catheter ablation -in general- is a highly effective and "curative" intervention for a broad spectrum of supraventricular and ventricular arrhythmias. After a successful procedure eliminating a simple arrhythmia substrate, the recurrence rate is low and the short term success correlates well with the long term freedom from the arrhythmia.

Atrial tachycardias following atrial fibrillation ablation.

One of the most important proarrhythmic complications after left atrial (LA) ablation is regular atrial tachycardia (AT) or flutter. Those tachycardias that occur after atrial fibrillation (AF) ablation can cause even more severe symptoms than those from the original arrhythmia prior to the index ablation procedure since they are often incessant and associated with rapid ventricular response. Depending on the method and extent of LA ablation and on the electrophysiological properties of underlying LA substrate, the reported incidence of late ATs is variable. To establish the exact mechanism of these tachycardias can be difficult and controversial but correlates with the ablation technique and in the vast majority of cases the mechanism is reentry related to gaps in prior ablation lines. When tachycardias occur, conservative therapy usually is not effective, radiofrequency ablation procedure is mostly successful, but can be challenging, and requires a complex approach.