Atrial Overdrive Pacing Research Articles

Biatrial Tachycardia: Distinguishing Between Active and Passive Activation.

The approach to successful ablation of arrhythmias is based on elucidating the underlying mechanism and relative dimensions of the tachycardia circuit. Activation mapping readily distinguishes macroreentry from focal arrhythmias, the latter of which have centrifugal spread. When macroreentrant atrial tachycardia is suspected, entrainment maneuvers with atrial overdrive pacing at various anatomic sites help differentiate right-sided from left-sided circuits. Based on the difference between the postpacing interval (PPI) and tachycardia cycle length (TCL), the proximity of the pacing site to the reentrant circuit can be assessed.1 However, even in a reentrant tachycardia, a short PPI–TCL interval (< 30 ms) may not always reliably identify whether the pacing site is within the tachycardia circuit, particularly when widely disparate locations seem to be “in the circuit”. In these cases, it is important to return to the fundamental principles of entrainment and to recognize the subtle changes in antidromic and orthodromic wavefronts in response to overdrive pacing that help to correctly identify the tachycardia circuit. See Editor’s Perspective by Asirvatham and Stevenson A 57-year-old man with a history of hypertension, hyperlipidemia, coronary artery disease, rheumatic heart disease, and 5 previous surgeries for mechanical aortic and mitral valve replacements and coronary artery bypass grafting presented with 6 months of worsening dyspnea on exertion that correlated with the onset of persistent atrial tachycardia (Figure 1). In the electrophysiology laboratory, the patient’s clinical atrial TCL was 360 ms. Diagnostic catheters were placed to encircle the tricuspid annulus within the coronary sinus (CS) and at the superior margin of the tricuspid annulus to record the His bundle (Figure 2A). Entrainment mapping demonstrated a short PPI–TCL from the cavotricuspid isthmus (CTI; Figure 2B), the proximal CS (Figure 2C), and the superior tricuspid annulus (Figure 2D). Entrainment from the distal CS also showed a PPI–TCL of 0 ms (Figure …

Effect of cardiac pacing on sleep-related breathing disorders: a systematic review.

Sleep-related breathing disorders are commonly encountered in the middle-aged population, negatively affecting quality of life. Central sleep apnea is associated with congestive heart failure, whereas obstructive sleep apnea is related to different pathophysiologic mechanisms, such as the total or partial occlusion of upper airway tract. Both sleep-related disorders have been associated with increased morbidity, and hence, they have been a target of several treatment strategies. The aim of this systematic review is to evaluate the effect of different types of cardiac pacing on sleep-related breathing disorders in patients with or without heart failure. The PubMed and Cochrane Central Register of Controlled Trials were examined from April 2015 to January 2016. Of the initial 360 studies, 22 eligible trials were analyzed. The included studies were classified according to the type of sleep disorder and the intervention undertaken. The evidence shows that cardiac resynchronization therapy but not atrial overdrive pacing can reduce apneic events in central sleep apnea patients. However, their effect on obstructive sleep apnea is controversial. It can be assumed that pacing cannot be used alone as treatment of sleep-related breathing disorders. Further research is needed in order to elucidate the effect of these interventions in sleep apnea patients.

Ectopies from the superior vena cava after pulmonary vein isolation in patients with atrial fibrillation.

Episodes of atrial fibrillation (AF) are mainly initiated by triggers from pulmonary veins (PVs). The superior vena cava (SVC) has been identified as a second major substrate of non-PV foci, but the electrophysiologic features of the SVC have not been fully investigated. We hypothesized that SVC ectopies are suppressed by predominant features of PV ectopies and tend to appear after PV isolation (PVI). We evaluated the electrophysiological characteristics and clinical implications of SVC ectopies in patients with AF during catheter ablation using high-dose isoproterenol and the atrial overdrive pacing maneuver. The manifestation patterns and modes of onset (coupling interval and appearance interval) of ectopies from both the PVs and SVC were investigated. 205 patients were enrolled [153 males and 52 females; mean age 64±10years; paroxysmal in 143 patients (69.8%), persistent in 40 (19.5%), and long-standing persistent in 22 patients (10.7%)]. Before PVI, PV ectopies were detected in 182/205 patients (89%). SVC ectopies were rarely observed before PVI but were significantly more frequent after the completion of PVI (3/205 vs. 14/205 patients, p=0.011). The coupling interval (CI) and % CI (CI/preceding the A-A interval×100) of PV ectopies were significantly shorter than those of SVC ectopies (211±78 vs. 282±106ms, p=0.021, and 34±9 vs. 51±17%, p<0.001, respectively). The appearance intervals of the PV ectopies were shorter than those of the SVC ectopies (6.3±4.0 vs. 10.7±6.7s, p=0.030). During repeat procedures, PVs with reconnection to the left atrium were less frequently observed in patients with SVC firing than in patients without SVC firing (1.7±1.5 vs. 2.9±1.1 PVs, p=0.029). We demonstrated that PVI tends to manifest SVC ectopies with less spontaneous activity and that an elimination of predominant ectopies from the PVs may affect appearance of SVC ectopy.

24. Entrainment of wide complex tachycardia by atrial stimulation is highly accurate and can rapidly elucidate the tachycardia mechanism through analysis of entrainment response

Although the diagnosis of wide-complex tachycardia (WCT) in the Electrophysiology Laboratory is usually straightforward, occasionally a WCT with 1:1 AV relationship can pose a diagnostic challenge. Furthermore, different responses to entrainment have been reported in relation to the pacing site of a variety of tachycardias, however, transient atrial entrainment of WCT has not been investigated sufficiently and systematically .We studied the response to atrial overdrive pacing to clarify the tachycardia mechanism. Out of 43 consecutive patients who underwent catheter ablation for WCT, we prospectively studied 28 patients (65%, mean age 33 ± 11 years) with WCT and 1:1 AV relationship in whom response to atrial overdrive pacing could be evaluated. During the tachycardia, atrial overdrive pacing was performed. The following responses were observed: A change of the QRS morphology during atrial pacing. The first return electrogram of the tachycardia, whether occurring in the atrium (AVA response) or in the ventricle (AVVA response). Atrial post-pacing interval (PPI) measured to the return A at the pacing site. The difference between PPI and tachycardia cycle length (PPI-TCL). Atrial overdrive pacing was successfully performed in 28 patients. It was associated with either a change or narrowing of the QRS in all ventricular tachycardia (VT, n = 7) patients but not in supraventricular tachycardia (SVT, n = 21) patients. All VT patients had an AVVA response upon cessation of atrial overdrive pacing as opposed to AVA response in SVT patients, p < 0.001. PPI and PPI-TCL were significantly longer in VT patients (640;± 92 ms vs. 378;± 49 ms, p < 0.001 and 294;± 75 ms vs. 70;± 40 ms, p < 0.001 respectively). Receiver operator characteristics curve identified PPI-TCL >160 ms as 100% sensitive and specific for diagnosing VT (p < 0.001). Response to atrial entrainment can be helpful in the majority of WCT patients, particularly those with 1:1 AV relationship to diagnose or rule out VT as a mechanism of tachycardia with high accuracy.

Select Articles Published on the Topic of Arrhythmia and Electrophysiogy in 2013

Select Articles Published on the Topic of Arrhythmia and Electrophysiogy in 2013

Role of Bi-Atrial Pacing In Slowing The Progression of Paroxysmal Atrial Fibrillation To Permanent Atrial Fibrillation.

Introduction: Bi-atrial lead placement combined with atrial overdrive pacing has demonstrated a reduction in percent time mode switched and mode switches per day. This retrospective analysis compared long term outcomes of patients with right atrial overdrive pacing alone (DAO) to patients having atrial overdrive with bi-atrial leads (BIA) in slowing the progression of paroxysmal atrial fibrillation (PAF) to permanent continuous atrial fibrillation (CAF). Methods: Thirty-three patients age 76.6 (+/-1.96) from our prior investigation were selected. The DAO control group (N=16) had received a standard right atrial pacing lead. The BIA group (N=17) had pacing leads placed in the right atrium and coronary sinus. Patients were followed for a mean 1217 days (+/-838). Days of CAF was classified as the date of final mode switch until analysis. Results: A total of 40,171 follow-up days were evaluated. The mean follow-up for both cohorts was 1217 days (+/-838). The DAO group consisted of 15,318 days (mean 957 +/-761) and the BIA group 24,853 days (mean 1461 +/-854). A lower total number of days were spent in CAF in the BIA group versus the DAO group, 1380 vs 2197 respectively. Corrected for follow-up duration, 5.55% days in CAF was seen in the BIA group vs. 14.34% in the DAO group which did not reach statistical significance. Conclusions: Although BIA overdrive pacing initially demonstrated reduced time in mode switch compared to DAO alone, this analysis did not detect a reduction in progression to CAF. More subjects or a longer follow up would be needed.

Prospective Randomized Study to Assess the Efficacy of Site and Rate of Atrial Pacing on Long-Term Progression of Atrial Fibrillation in Sick Sinus Syndrome

Background— Atrial-based pacing is associated with lower risk of atrial fibrillation (AF) in sick sinus syndrome compared with ventricular pacing; nevertheless, the impact of site and rate of atrial pacing on progression of AF remains unclear. We evaluated whether long-term atrial pacing at the right atrial (RA) appendage versus the low RA septum with (ON) or without (OFF) a continuous atrial overdrive pacing algorithm can prevent the development of persistent AF. Methods and Results— We randomized 385 patients with paroxysmal AF and sick sinus syndrome in whom a pacemaker was indicated to pacing at RA appendage ON (n=98), RA appendage OFF (n=99), RA septum ON (n=92), or RA septum OFF (n=96). The primary outcome was the occurrence of persistent AF (AF documented at least 7 days apart or need for cardioversion). Demographic data were homogeneous across both pacing site (RA appendage/RA septum) and atrial overdrive pacing (ON/OFF). After a mean follow-up of 3.1 years, persistent AF occurred in 99 patients (25.8%; annual rate of persistent AF, 8.3%). Alternative site pacing at the RA septum versus conventional RA appendage (hazard ratio=1.18; 95% confidence interval, 0.79–1.75; P =0.65) or continuous atrial overdrive pacing ON versus OFF (hazard ratio=1.17; 95% confidence interval, 0.79–1.74; P =0.69) did not prevent the development of persistent AF. Conclusions— In patients with paroxysmal AF and sick sinus syndrome requiring pacemaker implantation, an alternative atrial pacing site at the RA septum or continuous atrial overdrive pacing did not prevent the development of persistent AF. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00419640.

Circulation : Clinical Summaries

<i>Circulation</i> : Clinical Summaries

AF pacing in sick sinus syndrome

“In patients with sick sinus syndrome (SSS), the occurrence of atrial fibrillation (AF) after pacemaker implantation is very common and associated with increased risk of stroke, systemic embolism, heart failure, and mortality,” says Hung-Fat Tse from the Queen Mary Hospital in Hong Kong. A study undertaken by Tse and colleagues, and published in Circulation, has shown that neither the use of an alternative atrial pacing site in the right atrial septum, nor continuous atrial overdrive pacing, prevents the development of persistent AF in patients with SSS.

Initial shortening of the tachycardia cycle length after the induction of fast-slow atrioventricular nodal reentrant tachycardia may support slow pathway as an antegrade limb of the reentry circuit

Introduction: It remains controversial whether fast pathway (FP) is actually incorporated as an antegrade limb of the reentry circuit in fast-slow (F-S) atrioventricular nodal reentrant tachycardia (AVNRT) with the earliest atrial activation at coronary sinus ostium, presenting long RP tachycardia, because antegrade conduction over slow pathway (SP) is occasionally observed during the tachycardia. Although double ventricular responses (DVR) in which single atrium impulse conducts to the ventricle simultaneously over FP and SP are frequently observed during slow-fast (S-F) AVNRT, these phenomena have not been recognized during F-S AVNRT. The purpose was to verify our hypothesis that SP is incorporated as an antegrade limb of the reentry circuit in F-S AVNRT, by the detection of DVR during F-S AVNRT. Methods: In 6 F-S AVNRT, 8 S-F AVNRT and 8 atrioventricular reentrant tachycardia (AVRT) reproducibly inducible with atrial extrastimulation (S1-S2) or overdrive pacing (S2-S2), we examined an initial cyclic variation after the induction of the tachycardia by measuring interhisian intervals of H2-H3, H3-H4 and H4-H5. Results: As shown in table, the tachycardia cycle length immediately after the induction was paradoxically shorter than the subsequent tachycardia cycle length in F-S AVNRT only. Temporal P-QRS variation during F-S AVNRT and a complication of S-F AVNRT with the same earliest atrial site in 5 F-S AVNRT (83%) suggested the presence of low common pathway (LCP) located below the AVN reentry circuit. Values are expressed in ms. *p<0.05 vs H4-H5 interval minus H3-H4 interval. Conclusions: Paradoxical shortening of H2-H3 in F-S AVNRT may be explained by DVR in which H2 and H3 is antegradely captured over FP and SP, respectively, followed by slow-slow AVNRT with a long LCP, presenting long RP tachycardia.

SAFE Combinations Fail to Open the Door to Atrial Fibrillation Prevention

The prevalence of atrial fibrillation (AF) in the entire US population is ≈1%.1 The prevalence of AF increases substantially with age, with ≤9% of patients over the age of 80 years developing AF. The population presenting with permanent pacing requirements also increases with age, and the cumulative lifetime risk of developing paroxysmal AF in pacemaker patients may be as high as 40%.2 Article see p 687 Mechanisms for AF initiation and maintenance are multiple but are widely accepted to be a result of triggered initiation by atrial premature beats, and maintenance within the atrial substrate on the basis of multiple wavelets of reentry and rotors that depend on inhomogeneous atrial refractory periods and atrial conduction velocities. Atrial pacing may prevent both AF triggers and atrial substrate changes by suppressing atrial premature beats and inducing a more homogenous atrial landscape of refractory periods and conduction velocities. Atrial-based pacing is clearly superior to ventricular pacing alone in preventing atrial fibrillation with an 18% relative risk reduction with atrial-based pacing over a 3-year follow-up.3 This treatment effect has been postulated to be the result of atrial premature beat suppression and changes in atrial refractory periods and atrial conduction velocities as a result of atrial stretch attributed to higher atrial pressure from AV dyssynchronous pacing. The atrial changes associated with atrial-based pacing could possibly be enhanced by atrial overdrive pacing algorithms or by alternative site atrial pacing, such as the atrial septum. The role of alternative-site atrial pacing …

Transesophageal Overdrive Pacing: A Simple and Versatile Tool

In the present case, a patient with atrial flutter failed drug conversion with use of intravenous amiodarone and before resorting to electrical cardioversion, transesophageal atrial overdrive pacing was proposed and performed as a bedside procedure with successful conversion of atrial flutter into sinus rhythm

Radiofrequency Catheter Ablation of Intractable Ventricular Tachycardia in an Infant Following Arterial Switch Operation

A full-term male neonate presented with cyanosis upon delivery and was subsequently diagnosed with d-transposition of the great arteries, ventricular septal defect, and restrictive atrial septal defect. Following initiation of intravenous prostaglandins and balloon atrial septostomy, an arterial switch operation was performed on day 3 of life. The postoperative course was complicated by intractable ventricular tachycardia that was refractory to lidocaine, amiodarone, esmolol, fosphenytoin, and mexiletine drug therapy. Ventricular tachycardia was suppressed with overdrive atrial pacing but recurred upon discontinuation. Seven weeks postoperatively, radiofrequency catheter ablation was performed due to hemodynamically compromising persistent ventricular tachycardia refractory to medical therapy. The ventricular tachycardia was localized to the inferior-lateral right ventricular outlet septum. The procedure was successful without complications or recurrence. Antiarrhythmics were discontinued after the ablation procedure. Seven days after the ablation, a different, slower fascicular rhythm was noted to compete with the infant's sinus rhythm. This was consistent with the preablation amiodarone having reached subtherapeutic levels given its very long half-life. The patient was restarted on oral beta blockers and amiodarone. The patient was subsequently discharged home in predominantly sinus rhythm with intermittent fascicular rhythm.

EP News: Basic and Translational

Faggioni et al (Circ Res 2013;112:689, PMID 23295832) tested the hypothesis that catecholaminergic polymorphic ventricular tachycardia (CPVT) is suppressed by supraventricular overdrive stimulation. Using CPVT mouse models (Casq2−/−and RyR2(R4496C)+/−mice), the effect of increasing sinus heart rate was tested by pretreatment with atropine and by atrial overdrive pacing. Increasing intrinsic sinus rate with atropine and atrial overdrive pacing suppressed ventricular arrhythmias (VAs) in both CPVT models. In 6 of 18 patients with CPVT, VAs were paradoxically suppressed as sinus heart rates increased further with continued exercise. The authors conclude that accelerated supraventricular rates suppress VAs in 2 CPVT mouse models and in a subset of patients with CPVT. Hypothetically, atrial overdrive pacing may be a therapy for preventing exercise-induced VT in treatment-refractory patients with CPVT.

Accelerated Sinus Rhythm Prevents Catecholaminergic Polymorphic Ventricular Tachycardia in Mice and in Patients

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is caused by mutations in cardiac ryanodine receptor (RyR2) or calsequestrin (Casq2) genes. Sinoatrial node dysfunction associated with CPVT may increase the risk for ventricular arrhythmia (VA). To test the hypothesis that CPVT is suppressed by supraventricular overdrive stimulation. Using CPVT mouse models (Casq2(-/-) and RyR2(R4496C/+) mice), the effect of increasing sinus heart rate was tested by pretreatment with atropine and by atrial overdrive pacing. Increasing intrinsic sinus rate with atropine before catecholamine challenge suppressed ventricular tachycardia in 86% of Casq2(-/-) mice (6/7) and significantly reduced the VA score (atropine: 0.6±0.2 versus vehicle: 1.7±0.3; P<0.05). Atrial overdrive pacing completely prevented VA in 16 of 19 (84%) Casq2(-/-) and in 7 of 8 (88%) RyR2(R4496C/+) mice and significantly reduced ventricular premature beats in both CPVT models (P<0.05). Rapid pacing also prevented spontaneous calcium waves and triggered beats in isolated CPVT myocytes. In humans, heart rate dependence of CPVT was evaluated by screening a CPVT patient registry for antiarrhythmic drug-naïve individuals that reached >85% of their maximum-predicted heart rate during exercise testing. All 18 CPVT patients who fulfilled the inclusion criteria exhibited VA before reaching 87% of maximum heart rate. In 6 CPVT patients (33%), VA were paradoxically suppressed as sinus heart rates increased further with continued exercise. Accelerated supraventricular rates suppress VAs in 2 CPVT mouse models and in a subset of CPVT patients. Hypothetically, atrial overdrive pacing may be a therapy for preventing exercise-induced ventricular tachycardia in treatment-refractory CPVT patients.

A less aggressive therapeutic option for electrical storm.

Electrical storm (ES) describes the rapidly clustering ventricular fibrillation (VF) that requires multiple cardioversions. Emerging evidence suggests that Purkinje arborization and sympathetic nerve regeneration play a major role in initiating malignant arrhythmias. We report the case of two patients who, after having survived an acute myocardial infarction (MI), developed repetitive episodes of polymorphic ventricular tachycardia and VF one week after percutaneous revascularization, triggered by monomorphic premature ventricular contractions (PVCs). Owing to repetitive and drug-refractory VF episodes, temporary atrial overdrive pacing was attempted with complete suppression of VF. In the following month, recurrence of ventricular arrhythmia was inversely related to the atrial pacing rate. Although antiarrhythmic drugs other than beta-blockers had been discontinued, neither PVCs nor ventricular arrhythmias recurred at one-month follow-up when the lower pacing rate was set at 60 bpm. In conclusion in these patients, ES was likely related to nerve sprouting after ischemic injury. This chaotic phenomenon occurs early after tissue damage and shows a peak seven days after acute MI with degeneration of superfluous axon branches. High pacing rates can reduce early after depolarizations and suppress PVCs, thus preventing ES. On these grounds, ES patients may be treated with temporary overdrive pacing rather than early radiofrequency ablation.

Cryoablation for Presumed Atrioventricular Nodal Reentrant Tachycardia in Pediatric Patients

Little data exist on the outcomes of cryoablation for the treatment of presumptive atrioventricular nodal reentrant tachycardia (AVNRT) in a pediatric population. We performed a retrospective chart review of patients undergoing cryoablation from January 2006 to October 2010 for presumed AVNRT at the Children's Hospital Colorado. Inclusion criteria were age ≤ 18, normal heart structure, no prior ablation procedures, documented narrow complex tachycardia, and no inducible tachycardia or other tachycardia mechanisms during electrophysiology study. Thirteen patients underwent cryoablation for presumed AVNRT. Cryoablation catheter tip size varied from 4 to 8 mm with a median of eight cryoablation lesions. Isoproterenol was utilized preablation in 54% and none postablation. Procedural endpoints, per written report, were loss of sustained slow pathway, change in Wenckebach cycle length, and no specific endpoint. Procedural endpoints, per measured data, were a decrease in patients exhibiting sustained slow pathway conduction. Maximum atrial-His (AH) interval with atrial overdrive pacing was reduced from 266 ms preablation to 167 ms postablation, p = 0.006. The number of patients with an AH jump was reduced from 6 to 2. After follow-up of 13.8 ± 14.3 months, 23% (3/13) had documented tachycardia recurrence. No statistical significance was determined when comparing electrophysiology testing parameters pre- and postablation among the group with recurrence versus the group without recurrence. Cryoablation can be considered as a safe alternative to radiofrequency ablation for the treatment of presumed AVNRT among pediatric patients, albeit with a recurrence rate of 23%.

Hazards of Atrial Overdrive Pacing Delivered to Prevent Atrial Fibrillation

Hazards of Atrial Overdrive Pacing Delivered to Prevent Atrial Fibrillation

Atrial overdrive pacing to prevent atrial fibrillation: Insights from ASSERT

Pacing algorithms to prevent atrial fibrillation (AF) have been tested in studies of modest size and duration with inconclusive results. To prospectively evaluate the relationship between subclinical AF and stroke in patients 65 years of age or older with no previous AF receiving a first pacemaker or an implantable cardioverter-defibrillator for standard indications. Three months following device implantation, pacemaker patients were randomized to have continuous atrial overdrive pacing (CAOP) algorithm turned "ON" or "OFF." The primary study outcome was development of electrocardiogram-documented AF >6 minutes. A total of 2343 patients were randomized and followed for a mean of 2.5 years. The primary outcome occurred in 60 patients in the CAOP ON group (1.96% per year) and in 45 in the CAOP OFF group (1.44% per year; relative risk 1.38; 95% confidence interval 0.94-2.03; P = .10). Major clinical events (stroke, myocardial infarct, cardiovascular death, systemic embolism, heart failure hospitalization) occurred at similar frequencies in the 2 groups. In the CAOP ON group, 133 of the 1164 patients (11.4%) crossed over to CAOP OFF compared with 12 of the 1179 (1.0%) who crossed over from OFF to ON (P <.0001). False-positive device detections of AF were more common among patients assigned to CAOP ON (23%) than among patients assigned to CAOP OFF (7.7%; relative risk 2.99; 95% confidence interval 2.40-3.74; P <.001). Pacemaker generator replacement for battery depletion occurred in 4.4% of the subjects randomized to CAOP ON and in 2.5% of the patients assigned to CAOP OFF (relative risk 1.70; 95% confidence interval 1.08-2.67; P = .02). CAOP does not prevent new-onset AF, is poorly tolerated, and accelerates pulse generator battery depletion.

Diagnostic Pacing Maneuvers for Supraventricular Tachycardias: Part 2

The approach to supraventricular tachycardia (SVT) diagnosis can be complex because it involves synthesizing baseline electrophysiologic features, features of the SVT, and the response(s) to pacing maneuvers. In this two-part review, we will mainly explore the latter while recognizing that neither of the former can be ignored, for they provide the context in which diagnostic pacing maneuvers must be correctly chosen and interpreted. Part 1 involved a detailed consideration of ventricular overdrive pacing, since this pacing maneuver provides the diagnosis in the majority of cases. In Part 2, other diagnostic pacing maneuvers that might be helpful when ventricular overdrive pacing is not diagnostic or appropriate, including attempts to reset SVT with single atrial or ventricular beats, para-Hisian pacing, apex versus base pacing, and atrial overdrive pacing, are discussed, as are some specific diagnostic SVT challenges encountered in the electrophysiology lab. There is considerable literature on this topic, and this review is by no means meant to be all-encompassing. Rather, we hope to clearly explain and illustrate the physiology, strengths, and weaknesses of what we consider to be the most important and commonly employed diagnostic pacing maneuvers, that is, those that trainees in cardiac electrophysiology should be well familiar with at a minimum.