Incremental Atrial Pacing Research Articles

Pitfalls and limitations in the assessment of the HV interval in a transcatheter aortic valve replacement population. A prospective analysis

Abstract Funding Acknowledgements Type of funding sources: None. Introduction identification of patients with new-onset conduction disturbances at risk of AV-block remains a major unmet challenge in Transcatheter Aortic Valve Replacement (TAVR). His-Ventricular interval (HVI) measurement has been proposed in patients at risk. However, the HVI assessment is often overlooked, performed as a single assessment without active mapping, and even single-catheter assessment is sometimes performed. Purpose To systematically evaluate HVI measurements in a post TAVR population, in search of methodological pitfalls as related to outcomes Methods Consecutive patients who underwent HVI assessment post-TAVR between June 2014 and December 2021. HV interval was classified as normal (<55), intermediate (55-70) and abnormal (>70 ms). Incremental atrial pacing was performed whenever possible. All tracings were reviewed by two blinded operators. Pitfalls in the assessment of atrioventricular conduction were categorized into types 1 to 5, as reported in Table 1. In sinus rhythm, only proximal HVI were considered defined as the concomitant recording of a near-field atrial signal. Results 90 cases were analyzed; median age 81 years1 [76 – 86] years; 37 (41%) male. The median HV interval was 54 [50 – 65] ms. An abnormal HV interval, exceeding the 55 and 70ms cut-off values, was found in 41 (45.9%) and 13 (14.8%) patients, respectively. At least one pitfall was found in 15 patients (16%). Short-term AV block occurred in 3 patients in sinus rhythm in whom no incremental pacing was performed, and in 2 patients with AF despite normal or borderline HVI in both groups. Conclusions Pitfalls in the assessment of the HVI are often observed after TAVR. Identification of infra- and especially intra-His disorders requires careful mapping and must be an active process on behalf of the operator. Our results call into question the value of the HV assessment using a single catheter or in patients with atrial fibrillation, considering the value of incremental atrial pacing and the inherent limitations in AF to assess the most proximal His or intraHis block.

The impact of chronotropic incompetence on atrioventricular conduction times in heart failure patients.

Intrinsic atrioventricular (AV) conduction is used to optimize AV intervals with cardiac resynchronization therapy (CRT) in most device algorithms. Atrial pacing and heart rate affect conduction times, but little is known regarding differeces among chronotropic incompetent(CI) and competent(CC) patients to guide programming. RAVE was a multicenter prospective trial of CRT patients. Heart rate was increased with incremental atrial pacing and with submaximal exercise. According to the maximal heart rate achieved during exercise, patients were classified as either CI or CC. For CI patients, an additional symptom-limited exercise with rate-adaptive pacing activated was performed. Intracardiac intervals were measured from the implantable lead electrograms in multiple postures. There were 12 subjects with CI and 24 with CC. With atrial pacing, AV interval immediately increased and gradually increased with incremental atrial pacing in all patients. However, the changes in the atrial to right ventricular (ARV) and atrial to left ventricular (ALV) intervals with increasing atrial pacing rates were about threefold greater in CI patients compared to CC patients (24.3 ± 28.9 vs. 7.2 ± 5.5ms/10bpm for ARV and 22.7 ± 25.6 vs. 7.1 ± 5.7ms/10bpm for ALV in the standing position, p < 0.05). In CI pacing with rate-adaptive pacing during exercise, AV interval changes with paced heart rate were variable. The AV response to overdrive atrial pacing at rest may provide a simple means of identifying chronotropic competence in CRT patients. For patients with CI, who often require rate-adaptive atrial pacing, rate-adaptive AV algorithms should be adjusted individually.

678 WIDE COMPLEX TACHYCARDIA IN A PATIENT TREATED WITH PERMANENT HIS BUNDLE PACING: A CASE REPORT

Abstract Introduction Differential diagnosis of wide complex tachycardias based only on ECG analysis remains a challenging exercise. But, when intracardiac tracings are available (i.e., pacemaker EGM), electrophysiologists may consider several tricks to make a correct diagnosis. Case Presentation A 73-years-old sporty male was admitted to our hospital for palpitations and dizziness. ECG monitoring revealed AF, typical atrial flutter and asystolic pauses following spontaneous cardioversion of atrial arrhythmias. We diagnosed sick sinus syndrome and implanted a dual-chamber pacemaker with an atrial lead in the right appendage and a stylet-directed active fixation lead in the His region, obtaining non-selective narrow paced QRS. The day after PM implantation, during a new episode of AF, two runs of regular wide-complex tachycardia (LBBB morphology, cycle length of 270 ms) occurred (Fig 1A, B). LBBB morphology, patient's history, and AF favored aberrancy, but couldn't exclude VT or preexcitation (by atrio-fascicular AP). Our diagnostic strategy consisted in adding atrial and His intracardiac electrograms registered by pacemaker to analysis of ECG traces. The device interrogation showed AV dissociation at the time of the wide complex tachyarrhythmia and a negative HV interval (Fig. 2A). These findings ruled out aberrant ventricular conduction and bundle branch reentrant tachycardia, because both these arrhythmias are characterized by HV ≥ HV in sinus rhythm. We performed incremental atrial pacing maneuver, during SR, obtaining decremental AH conduction with constant HV interval (60 ms), excluding atrio-fascicular, nodo-fascicular and nodo-ventricular AP. His bundle activity was identified just after the ventricular activation, producing a relatively short VH interval, suggesting the presence of a retrograde activation of the His bundle, therefore it was possible to hypothesize that the site of origin of the ventricular arrhythmia was within/or very close to RBB (Fig 2B, C). Just in few beats His bundle deflection was missing, probably because of recovery of functional LBBB (Fig 2D). Discussion Our final diagnosis was RBB VT. Patient was treated with Verapamil 80 mg t.i.d., with no further recurrence. This case highlights the diagnostic value of device interrogation in patients with permanent His bundle pacing, for the evaluation of wide complex tachycardias.

A case report of profound atrioventricular block in an endurance athlete: how far do you go?

BackgroundAthletes presenting with 1st-degree atrioventricular block (AVB) on 12-lead electrocardiogram (ECG) may present a diagnostic conundrum, especially when significantly prolonged and associated with higher degrees of block. A pragmatic stepwise approach to the evaluation of these patients is, therefore, crucial.Case summaryA 19-year-old waterpolo player was referred for assessment of a 1st-degree heart block and one isolated episode of syncope. All other cardiac investigations were within normal limits except for a 24-h ambulatory ECG which showed Mobitz 1 AVB and episodes of 2:1 block occurring in the context of Wenchebach. An electrophysiological study (EPS) was performed which effectively excluded infranodal conductive tissue disease, confirming physiological intranodal block.DiscussionThe increase in vagal tone is one of the physiological adaptations to an increased demand in cardiac output in athletes, which explains the presence of 1st-degree AVB in up to 7.5% of athletes. The presence of 2:1 AVB on 24 h ECG raises doubts whether the 1st-degree AVB on resting ECG is pathological or physiological, especially considering this particular patient had suffered an episode of syncope. When this diagnostic uncertainty persists despite non-invasive investigations, including cardiopulmonary exercise testing, invasive EPS may be required to assess the refractoriness of the AV node and at what level within the cardiac conductive system block occurs. The electrophysiological study can effectively rule out infranodal disease by confirming physiological intranodal block using incremental atrial pacing.

Non-algorithmic approach to accessory pathway localization based on a mobile app

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Polish Cardiac Society - Section of Non-invasive Electrocardiology and Telemonitoring (PTK SENIT) Background. Electrocardiographical localization of accessory pathways (AP) in WPW syndrome remains an elusive goal. Despite several, often very complex algorithms that were developed over the last three decades, none of them is very accurate - as demonstrated by several independent validation studies. Moreover, algorithms are difficult to remember, which further limits their usefulness. The accessory pathway regions are arbitrary and transitions between them are smooth, not binary. The same applies to ECG features such as QRS polarity – they are not binary. Moreover, even the most careful ECG lead placement cannot compensate for the variability in heart position within the chest. Therefore, it is unrealistic to expect that any ECG feature or feature set will precisely identify a particular location in a 0 vs. 1 fashion. Aim We intend to create a mobile app / web based localizing application, that would support a novel method for AP localization: a colour density map generator - based on actual distribution of a sizable number of accessory pathway with a particular QRS features. Methods A total of 881 consecutive AP ablation procedures were reviewed and patients with successful ablation of an overt accessory pathway were included. ECG with baseline and full preexcitation obtained during incremental atrial pacing were obtained. AP localization was based on stored fluoroscopic images in several projections and procedure description. Each AP localization, as well as QRS polarity in all 12 leads, separately for full and baseline preexcitation patterns, were coded and introduced into the application database. An application web-based, optimized for mobile devices was developed. This application enabled to graphically show changing localization of AP with regard to the introduced, at each step, QRS polarity in a particular ECG lead. User can choose his/her own steps or criteria; there is no need to adhere to the proposed steps. Results A total of 604 patients/ ECGs were available for density map generation. With each additional lead QRS information introduced into the application the user can appreciate more and more precise localization of the AP. This quickly enables to pinpoint the area of maximum probability, i.e. the most likely/frequent location, followed by the immediate adjacent locations. Representative screen shots of to typical inital steps for left- and right-sided APs are provided below (Figure 1 and Figure 2). Limited prospective assessment was very favourable. Conclusions A novel method, easy to use, not requiring to remember any algorithmic steps, and based on an analysis of by far the largest cohort of over accessory pathways (in comparison with published algorithms) was developed. Prospective validation of the localization application seems warranted. Abstract Figure.

Mapping potentials adjacent to the cavo-tricuspid isthmus ablation line during incremental pacing: A feasible and highly accurate maneuver to confirm complete CTI conduction block.

The diagnostic accuracy of incremental atrial pacing (IP) to determine complete cavo-tricuspid isthmus (CTI) block during typical atrial flutter (AFL) ablation is limited by both an extensive/nonlinear ablation and/or the presence of intra-atrial conduction delay elsewhere in the right atrium. We examined the diagnostic performance of an IP variant based on the assessment of the atrial potentials adjacent to the ablation line which aims at overcoming both limitations. From a prospective population of 108 consecutive patients, 15 were excluded due to observation of inconclusive CTI ablation potentials precluding for a straight comparison between the IP maneuver and its variant. In the remaining 93, IP was performed from the low lateral right atrium and the coronary sinus ostium, with the ablation catheter positioned both at the CTI line and adjacent (<5 mm) to its septal and lateral aspect. The IP variant consisted of measuring the interval between the two atrial electrograms situated on the same side of the ablation line, opposite to the pacing site, a ≤10 ms increase indicating complete CTI block. The IP maneuver and its variant were consistent with complete CTI block in 82/93 (88%) and 87/93 (93%) patients, respectively. Four patients had AFL recurrence during follow-up: 2/4 and 4/4 had been adequately classified as incomplete block by the IP maneuver and its variant, respectively. Twenty-three patients (24%) had significant intra-atrial conduction delay elsewhere in the right atrium. The IP maneuver and its variant were suggestive of an incomplete CTI block in 11/23 and 4/23 in this setting (P = .028), with the later best predicting subsequent AFL relapses (2/12 vs 2/4, P = .01). The IP variant, which was designed to overcome the limitations of the conventional IP maneuver, accurately distinguishes complete from incomplete CTI block and helps to predict AFL recurrences after ablation.

Increased preexcitation on electrocardiography improves accuracy of algorithms for accessory pathway localization in Wolff–Parkinson–White syndrome

Several electrocardiographic (ECG) algorithms have been developed for predicting accessory pathway (AP) location in Wolff-Parkinson-White syndrome. However, their accuracy may be related to the manifested degree of preexcitation on ECG. Our goal was to assess the effect of the degree of preexcitation on the accuracy of 4 traditional AP localization algorithms and to compare them with the algorithm specifically designed for ECGs with maximal preexcitation (Pambrun) Methods: The study included 300 patients who underwent successful ablation of an overt atrioventricular AP. Resting and maximally preexcited ECGs obtained during incremental atrial pacing were assessed using 4 traditional AP localization algorithms: Xie, d'Avila, Iturralde, and Taguchi. Maximally preexcited ECGs were additionally assessed with the Pambrun algorithm. We compared the precision of the algorithms to predict accurate or anatomically adjacent AP location. Theoverall accuracy of traditional AP localization algorithms using resting ECG ranged between 26% and 53.7% and improved to a range of 47.3% to 69.7% when adjacent locations were accepted. When used with maximal preexcitation, all algorithms had significantly higher accuracy, with a mean improvement of 14.3 and 15.6 percentage points for precise and adjacent sites, respectively. The Pambrun algorithm for maximally preexcited ECGs had the highest precision for both accurate and adjacent locations of the APs (89.7% and 97%, respectively). Greater preexcitation on ECG improved the accuracy of the traditional AP localization algorithms. The algorithm designed to use maximally preexcited ECGs has the best accuracy. Maximally preexcited ECG recordings should preferably be used in clinical practice to facilitate the ablation procedure.

Adaptation of ventricular repolarization duration and dispersion during changes in heart rate induced by atrial stimulation.

BackgroundThe duration of ventricular repolarization (VR) and its spatial and temporal heterogeneity are central elements in arrhythmogenesis. We studied the adaptation of VR duration and dispersion and their relationship in healthy human subjects during atrial pacing.MethodsPatients 20‐50 years of age who were scheduled for ablation of supraventricular tachycardia without preexcitation but otherwise healthy were eligible. Vectorcardiography recordings with Frank leads were used for data collection. Incremental atrial pacing from a coronary sinus electrode was performed by decrements of 10ms/cycle from just above sinus rate, and then kept at a fixed heart rate (HR) just below the Wenckebach rate for ≥5min and then stopped. VR duration was measured as QT and VR dispersion as T area, T amplitude and ventricular gradient. The primary measure (T90 End) was the time to reach 90% change from baseline to the steady state value during and after pacing.ResultsA complete study protocol was accomplished in 9 individuals (6 women). VR duration displayed a monophasic adaptation during HR acceleration lasting on average 20s. The median (Q1‐Q3) T90 End for QT was 85s (51‐104), a delay by a factor >4. All dispersion measures displayed a tri‐phasic response pattern during HR acceleration and T90 End was 3‐5 times shorter than for VR duration.ConclusionsEven during close to “physiological” conditions, complex and differing response patterns in VR duration and dispersion measures followed changes in HR. Extended knowledge about these responses in disease conditions might assist in risk evaluation and finding therapeutic alternatives.

Body surface distribution of T wave alternans is modulated by heart rate and ventricular activation sequence in patients with cardiomyopathy.

BackgroundT wave alternans (TWA) is an electrocardiographic marker of heightened sudden death risk from ventricular tachyarrhythmias in patients with cardiomyopathy. TWA is evaluated from the 12-lead electrocardiogram, Frank lead, or Holter lead recordings, however these clinical lead configurations will not record TWA from adjacent regions of the body torso.ObjectiveWe tested the hypothesis that changing heart rate or ventricular activation may alter the body surface distribution of TWA such that the clinical ECG leads fail to detect TWA in some patients; thereby producing a false-negative test.MethodsIn 28 cardiomyopathy patients (left ventricular ejection fraction 28±6%), 114 unipolar electrograms were recorded across the body torso during incremental atrial pacing, followed by atrioventricular pacing at 100, 110 and 120bpm. TWA was measured from each unipolar electrogram using the spectral method. A clinically positive TWA test was defined as TWA magnitude (Valt) ≥1.9 uV with k ≥3 at ≤110bpm.ResultsMaximum Valt (TWAmax) was greater from the body torso than clinical leads during atrial (p<0.005) and atrioventricular pacing (p<0.005). TWAmax was most prevalent in the right lower chest with atrial pacing 100 bpm and shifted to the left lower chest at 120 bpm. TWAmax was most prevalent in left lower chest with atrioventricular pacing at 100 bpm and shifted to the left upper chest at 120 bpm. Using the body torso as a gold standard, the false-negative rate for clinically positive TWA with clinical leads was 21% during atrial and 11% during atrioventricular pacing. Due to TWA signal migration outside the clinical leads, clinically positive TWA became false-negative when pacing mode was switched (atrial→atrioventricular pacing) in 21% of patients.ConclusionsThe body surface distribution of TWA is modulated by heart rate and the sequence of ventricular activation in patients with cardiomyopathy, which can give rise to modest false-negative TWA signal detection using standard clinical leads.

A simplified approach for evaluating sustained slow pathway conduction for diagnosis and treatment of atrioventricular nodal reentry tachycardia in children and adults

PurposeDuring incremental atrial pacing in patients with atrioventricular nodal reentrant tachycardia, the PR interval often exceeds the RR interval (PR > RR) during stable 1:1 AV conduction. However, the PR/RR ratio has never been evaluated in a large group of patients with pacing from the proximal coronary sinus and after isoproterenol challenge. Our study validates new site of pacing and easier method of identification of PR > RR. Material and methodsA prospective protocol of incremental atrial pacing from the proximal coronary sinus was carried out in 398 patients (AVNRT-228 and control-170). The maximum stimulus to the Q wave interval (S-Q = PR), SS interval (S-S), and Q-Q (RR) interval were measured at baseline and 10 min after successful slow pathway ablation and after isoproterenol challenge (obligatory). ResultsThe mean maximum PR/RR ratios at baseline were 1.17 ± 0.24 and 0.82 ± 0.13 (p < 0.00001) in the AVNRT and controls respectively. There were no PR/RR ratios ≥1 at baseline and after isoproterenol challenge in 12.3% of the AVNRT group and in 95.9% of the control group (p < 0.0001). PR/RR ratios ≥1 were absent in 98% of AVNRT cases after slow pathway ablation/modification in children and 99% of such cases in adults (P = NS). The diagnostic performance of PR/RR ratio evaluation before and after isoproterenol challenge had the highest diagnostic performance for AVNRT with PR/RR > = 1 (sensitivity: 88%, specificity: 96%, PPV-97%, NPV-85%). ConclusionsThe PR/RR ratio is a simple tool for slow pathway substrate and AVNRT evaluation. Eliminating PR/RR ratios ≥1 may serve as a surrogate endpoint for slow pathway ablation in children and adults with AVNRT.

Intra-Atrial Conduction Delay Revealed by Multisite Incremental Atrial Pacing is an Independent Marker of Remodeling in Human Atrial Fibrillation.

ObjectivesThis study sought to characterize direction-dependent and coupling interval–dependent changes in left atrial conduction and electrogram morphology in uniformly classified patients with paroxysmal atrial fibrillation (AF) and normal bipolar voltage mapping.BackgroundAlthough AF classifications are based on arrhythmia duration, the clinical course, and treatment response vary between patients within these groups. Electrophysiological mechanisms responsible for this variability are incompletely described.MethodsIntracardiac contact mapping during incremental atrial pacing was used to characterize atrial conduction, activation dispersion, and electrogram morphology in 15 consecutive paroxysmal AF patients undergoing first-time pulmonary vein isolation. Outcome measures were vulnerability to AF induction at electrophysiology study and 2-year follow-up for arrhythmia recurrence.ResultsConduction delay showed a bimodal distribution, occurring at either long (high right atrium pacing: 326 ± 13 ms; coronary sinus pacing: 319 ± 16 ms) or short (high right atrium pacing: 275 ± 11 ms; coronary sinus pacing: 271 ± 11 ms) extrastimulus coupling intervals. Arrhythmia recurrence was found only in patients with conduction delay at long extrastimulus coupling intervals, and patients with inducible AF were characterized by increased activation dispersion (activation dispersion time: 168 ± 29 ms vs. 136 ± 11 ms). Electrogram voltage and duration varied throughout the left atrium, between patients, and with pacing site but were not correlated with AF vulnerability or arrhythmia recurrence.ConclusionsWithin the single clinical entity of paroxysmal AF, incremental atrial pacing identified a spectrum of activation patterns correlating with AF vulnerability and arrhythmia recurrence. In contrast, electrogram morphology (characterized by electrogram voltage and duration) was highly variable and not associated with AF vulnerability or recurrence. An improved understanding of the electrical phenotype in AF could lead to improved mechanistic classifications.

Heart Rate Dependence of the Pulmonary Resistance x Compliance (RC) Time and Impact on Right Ventricular Load.

BackgroundThe effect of heart rate (HR) and body surface area (BSA) on pulmonary RC time and right ventricular (RV) load is unknown.MethodsTo determine the association of HR and BSA with the pulmonary RC time and measures of RV load, we studied three large patient cohorts including subjects with 1) known or suspected pulmonary arterial hypertension (PAH) (n = 1008), 2) pulmonary hypertension due to left heart disease (n = 468), and 3) end-stage heart failure with reduced ejection fraction (n = 150). To corroborate these associations on an individual patient level, we performed an additional analysis using high-fidelity catheters in 22 patients with PAH undergoing right atrial pacing.ResultsA faster HR inversely correlated with RC time (p<0.01 for all), suggesting augmented RV pulsatile loading. Lower BSA directly correlated with RC time (p<0.05) although the magnitude of this effect was smaller than for HR. With incremental atrial pacing, cardiac output increased and total pulmonary resistance (TPR) fell. However, effective arterial elastance, its mean resistive component (TPR/heart period; 0.60±0.27 vs. 0.79±0.45;p = 0.048), and its pulsatile component (0.27±0.18 vs 0.39±0.28;p = 0.03) all increased at faster HR.ConclusionHeart rate and BSA are associated with pulmonary RC time. As heart rate increases, the pulsatile and total load on the RV also increase. This relationship supports a hemodynamic mechanism for adverse effects of tachycardia on the RV.

His Bundle Refractoriness.

Multiple points of instruction discussed practically in the context of a challenging case make for a memorable learning experience. In this installment of Teaching Rounds in Cardiac Electrophysiology, Nayyar et al1 elucidate the unique findings and analysis in such a manner and take us through to diagnosis and a treatment plan that eliminated arrhythmia without having to ablate all of the abnormal structures identified in their patient. Their case in which 2 unusual arrhythmogenic substrates coexist and interact to result in what appears to be a random and inexplicable series of electrophysiological findings is broken down in logical steps defining each aspect of the arrhythmia.1 These steps include defining the antegrade and retrograde limbs of the putative tachycardia circuit, defining the mechanism of tachycardia, and coming to a conclusion keeping in mind certain difficult differential diagnostic situations and the importance of interpreting His bundle refractory extrastimuli maneuvers. See Article by Nayyar et al When anterograde conduction over the AV node and an accessory pathway is present, the primary maneuver to determine the mechanism of AV conduction is incremental atrial pacing or delivery of coupled atrial extrastimuli. With usual accessory pathway activation, the ventricular beats represent fusion between AV node and accessory pathway conduction, and premature atrial beats progressively delay AV nodal conduction with no significant effect on the pathway. As a result, the stimulus to earliest ventricular activation remains fixed, but the H–V interval becomes progressively negative and the QRS progressively more preexcited. Nayyar et al1 noted that while subtle but significant increase in preexcitation and a more negative H–V interval did occur with atrial extrastimuli, there was a clearly discernible increment in overall conduction time to the ventricle. This finding may be seen with atriofascicular or AV pathways with AV node-like characteristics (incorrectly referred to as …

96-17: Atrial tachycardias in patients with long-standing persistent atrial fibrillation undergoing thoracoscopic epicardial RF ablation

Introduction: Surgical epicardial thoracoscopic RF ablation (SETA) was shown to be more effective in terms of clinical results than catheter based procedures in patients with atrial fibrillation (AF). However, neither surgery nor catheter ablation alone can achieve 100% complete and durable transmural lesions. The aim of this study was to determine mechanisms and localization of atrial tachycardias found after epicardial ablation. Methods: Patients with long-standing persistent AF underwent SETA with aim to create circumferential lesions around the ipsilateral pulmonary veins (PVs) using bipolar RF clamps, to complete linear connecting lesions and to ablate ganglionated plexi using linear pen. As a second step, a detailed 3D electroanatomical mapping (EAM) of both atria using CARTO3 system was performed within 6-8 weeks following surgical procedure. All spontaneous or induced atrial tachycardias (ATs) were mapped and ablated. Results: Sixty patients (mean age 62 years, LA diameter 49 ± 6 mm) were studied. Forty-five patients (75%) had sinus rhythm in the beginning of EAM. Six patients (10%) had typical CTI-dependent right atrial flutter; two patients (5.1%) had right atrial (RA) tachycardia, one patient (2.6%) had focal tachycardia arising from the middle CS, three patients (5%) had perimitral left atrial (LA) flutter, and finally, four patients (6.7%) had AF. All spontaneous ATs were successfully mapped and ablated. As a part of protocol, incremental atrial pacing was performed after finalization of all lines and PV isolations at the end of procedure. In 46 patients (76.7%), no sustained AF and/or AT was induced, in three patients (5%), AF lasting > 30 s was induced, but spontaneously terminated. Non self-terminating AF was induced in two patients (3.3%). In the remaining 9 patients (15%), 13 ATs were induced: 6 arising from the RA and 7 arising from the LA. All but 2 ATs were successfully abolished by RF ablation. Mean procedure and fluoroscopic times of the whole procedure reached 132 ± 37 min and 8 ± 2 min, respectively. 84% of patients maintained stable SR off antiarrhythmic therapy at 12-month follow-up. Reasonable arrhythmia control was achieved in 94% of patients. Conclusion: At least one quarter of patients are suffering from spontaneous ATs and/or AF after SETA. Catheter ablation of ATs following surgery is safe and highly effective. Sequential hybrid approach seems to achieve normal SR in vast majority of patients with previously long-standing persistent AF.

96-15: Atrial tachyarrhythmias in patients after surgical CryoMaze ablation procedure

Purpose of the study: The CryoMaze ablation procedure was developed as a surgical alternative to incisional treatment for atrial fibrillation. Incomplete lines can decrease the efficacy of the ablation procedure and can be proarrhythmic. The aim of this study is to determine incidence and mechanisms of atrial tachyarrhythmias occurring after surgical CryoMaze. We also studied the efficacy of completing surgical lines by RF catheter ablation to maintain sinus rhythm. Methods: Fourty-eight consecutive patients who required surgical CryoMaze ablation for persistent atrial fibrillation as an adjunct to a cardiac surgery were enrolled in the study. All patients had a 7-day ECG Holter 3 months after the surgical CryoMaze. Patients with documented paroxysmal or persistent atrial arrhythmias on the ECG Holter underwent an electrophysiological study with the right and left atria electroanatomical mapping using a CARTO3 navigation system. According to the protocol, patients in sinus rhythm were tested with incremental atrial pacing to induce atrial tachyarrhythmias after all gaps in surgical lines had been re-ablated using RF catheter ablation. If persistent atrial tachycardia was recorded at the beginning of the study, the tachycardia was mapped and ablated as the first step, which was followed by finalization of the surgical lines. All patients were followed-up for 24 months with repeated 7-day ECG Holters Summary of results: Thirteen (27%) patients had persistent and 12 (25%) patients had paroxysmal atrial tachyarrhythmia on the 7-day ECG Holter. Persistent arrhythmias were later confirmed during the electrophysiological study as atrial fibrillation in 5 patients, typical isthmus-dependent atrial flutter in 4 patients, 2 peri-mitral flutters, 1 roof dependent flutter and 1 focal atrial tachycardia from the inter-atrial septum. In patients with sinus rhythm in the beginning of the study, surgical lines were re-ablated in all patients. In 3 cases, incremental atrial pacing induced different focal atrial tachycardias after all surgical ablation lines had been finalized. All spontaneous and inducible arrhythmias were successfully mapped and ablated. Twenty-three out of 25 patients who underwent catheter ablation after surgical CryoMaze remained in sinus rhythm without antiarrhythmic medication during the 24-month follow-up. Conclusion: One quarter of patients after surgical CryoMaze suffer from persistent atrial tachyarrhythmias and another quarter have paroxysmal atrial arrhythmias. Catheter ablation of these tachyarrhythmias and finalization of surgical lines is effective approach to treat patients with documented atrial arrhythmias after surgical CryoMaze.

Right Ventricular Functional Reserve in Pulmonary Arterial Hypertension.

Right ventricular (RV) functional reserve affects functional capacity and prognosis in patients with pulmonary arterial hypertension (PAH). PAH associated with systemic sclerosis (SSc-PAH) has a substantially worse prognosis than idiopathic PAH (IPAH), even though many measures of resting RV function and pulmonary vascular load are similar. We therefore tested the hypothesis that RV functional reserve is depressed in SSc-PAH patients. RV pressure-volume relations were prospectively measured in IPAH (n=9) and SSc-PAH (n=15) patients at rest and during incremental atrial pacing or supine bicycle ergometry. Systolic and lusitropic function increased at faster heart rates in IPAH patients, but were markedly blunted in SSc-PAH. The recirculation fraction, which indexes intracellular calcium recycling, was also depressed in SSc-PAH (0.32±0.05 versus 0.50±0.05; P=0.039). At matched exercise (25 W), SSc-PAH patients did not augment contractility (end-systolic elastance) whereas IPAH did (P<0.001). RV afterload assessed by effective arterial elastance rose similarly in both groups; thus, ventricular-vascular coupling declined in SSc-PAH. Both end-systolic and end-diastolic RV volumes increased in SSc-PAH patients to offset contractile deficits, whereas chamber dilation was absent in IPAH (+37±10% versus +1±8%, P=0.004, and +19±4% versus -1±6%, P<0.001, respectively). Exercise-associated RV dilation also strongly correlated with resting ventricular-vascular coupling in a larger cohort. RV contractile reserve is depressed in SSc-PAH versus IPAH subjects, associated with reduced calcium recycling. During exercise, this results in ventricular-pulmonary vascular uncoupling and acute RV dilation. RV dilation during exercise can predict adverse ventricular-vascular coupling in PAH patients.

Pushing the limits: exercise stress in the healthy human heart.

Pushing the limits: exercise stress in the healthy human heart.

An Unusual Termination of a Wide Complex Tachycardia

A 40-year-old woman without structural heart disease was referred for nondocumented palpitations associated with ventricular preexcitation. The baseline electrocardiogram showed preexcitation suggestive of a posteroseptal accessory pathway (AP). With incremental right atrial pacing, atrioventricular (AV) conduction time over the AP was cycle length dependent (decremental) and maximal preexcitation was observed at pacing cycle length 320 milliseconds (Fig. 1). Retrograde conduction revealed earliest atrial activation at the orifice of the coronary sinus (CS 9–10) with decremental conduction and effective refractory period at the CS orifice of 430 milliseconds at a drive cycle length of 600 milliseconds. Wide complex tachycardia (cycle length 356 milliseconds) was observed during ventricular extrastimulus testing from the right ventricle (RV) apex (Fig. 2). A single premature ventricular contraction (PVC) delivered during tachycardia is shown in Figure 3. What is the mechanism of the tachycardia?

Relative Refractoriness of Left Ventricular Contraction Underlies Human Tachycardia‐Induced Mechanical and Electrical Alternans

Mechanical alternans (MA) and electrical alternans (EA) are predictors of cardiac events. Experimental studies have suggested that refractoriness of calcium cycling underlies these cardiac alternans. However, refractoriness of left ventricular contraction has not been examined in patients with cardiac alternans. In 51 patients with miscellaneous heart diseases, incremental right atrial pacing was performed to induce MA and EA. MA was quantified by alternans amplitude (AA: the difference between left ventricular dP/dt of a strong beat and that of a weak beat), and AA at 100/min (AA100) and maximal AA (AAmax) were measured. EA was defined as alternation of T wave morphology in 12-lead electrocardiogram. Relative refractoriness of left ventricular contraction was examined by drawing the mechanical restitution curve under a basal coupling interval (BCL) of 600 ms (100/min) and was assessed by the slope at BCL (Δmechanical restitution). Postextrasystolic potentiation (PESP) was also examined and the slope of PESP curve (ΔPESP) was assessed as a property to alternate strong and weak beats. MA and EA were induced in 19 patients and in none at 100/min or less, and at any heart rate in 32 and in 10, respectively. AA100 and AAmax correlated positively with Δmechanical restitution and negatively with ΔPESP. Patients with EA had a significantly larger Δmechanical restitution and a significantly larger absolute value of ΔPESP than those without. In patients with MA and EA, the left ventricular contractile force during tachycardia is under relative refractoriness and prone to cause large fluctuation of contractile force.

Two Cases of Supraventricular Tachycardia After Accessory Pathway Ablation

A 52-year-old man was referred for recurrent palpitations after 2 prior electrophysiology studies and ablations at an outside institution targeting right anteroseptal and left posterolateral accessory pathways (AP) for orthodromic reentrant tachycardia (ORT). Baseline ECG revealed sinus rhythm without preexcitation and an incomplete right bundle branch block. An ECG from his most recent tachycardia episode demonstrated a long RP tachycardia, with an incomplete right bundle branch block pattern at a rate of 135 beats per minute. Prior echocardiogram showed no evidence of structural heart disease. At electrophysiology study, the baseline atrial-His (AH) and His-ventricular (HV) intervals were both 58 ms. There was no preexcitation with incremental atrial pacing. There were spontaneous echo beats, which had a ventriculoatrial (VA) interval of 230 ms with concentric-appearing retrograde activation. Tachycardia with a cycle length (CL) of 460 ms was reproducibly initiated with programmed ventricular stimulation after a retrograde VA jump. Entrainment from the right ventricle (RV; mid-septum) showed a V-A-V response and a postpacing interval (PPI) of 583 ms without significant AH prolongation (Figure 1). Stim-A minus V-A time was 97 ms. Premature ventricular complexes (PVCs) from the septum during tachycardia advanced the atrium only if they were delivered ≥45 ms before the His deflection. Differential pacing was performed with entrainment from the RV apex yielding a PPI of 605 ms, whereas RV basal pacing resulted in a PPI of 601 ms. PPI from the proximalcoronary sinus (CS) was markedly prolonged (>50 ms over tachycardia CL) and was even longer from the mid CS (Figure 2). Mapping of the annular septum showed earliest retrograde activation at the mid right atrial (RA) septum. PPI with entrainment from here was 20 ms >tachycardia CL. What is the mechanism of the tachycardia, and what is the appropriate next step? Figure 1. Response to entrainment from the mid-right ventricular …