Strategies to improve atrioventricular synchrony in patients with a Micra AV leadless pacemaker.

The second generation of transcatheter pacing systems, called Micra AV, can provide atrioventricular (AV) synchronous pacing via a new pacing algorithm relying on sensing mechanical atrial contraction. Several novel programming parameters were introduced to enable AV synchronous pacing, including an A3 window and A4 window as well as a conduction mode switch and an activity mode switch. In addition to several automated features, manual programming optimization of some of the novel parameters is key to improving AV synchrony. A solid knowledge of the features and their programming is essential for electrophysiologists implanting or following patients with Micra AV devices. Differences in programming optimization might partially explain the high variability of AV synchrony published in real-world data reports. This article reviews the key programming parameters of Micra AV. Subsequently, optimal programming recommendations for defined patient profiles are presented. Those were established by consensus within an expert panel comprised of 11 European electrophysiologists from high-volume Micra AV centres. The patient profiles were (1) high degree AV block and slow sinus rhythm; (2) high degree AV block and fast sinus rhythm; and (3) intermittent AV block. The panel recommended to evaluate the mechanical atrial activity on transthoracic echocardiography prior to implant. It was also agreed that Auto A3 Threshold and Tracking Check should be turned off in all patients, AV conduction mode switch should be turned off in all patients with high degree AV block, and the lower rate should be programmed to 50 bpm with exceptions based on individual clinical assessment. Future studies will be useful to evaluate the strength of those recommendations to improve the AV synchrony.

Persistent atrial fibrillation without the evidence of low-voltage areas: a prospective randomized trial.

BACKGROUND: An effective therapy of persistent atrial fibrillation beyond pulmonary vein isolation remains unsatisfactory. Targeting endocardial low-voltage areas represents an approach of substrate modification. This prospective, randomized study investigated the efficacy of ablation of low-voltage areas versus PVI and additional linear ablations in patients with persistent atrial fibrillation in terms of single-procedure arrhythmia-free outcome and safety. METHODS AND RESULTS: A total number of 100 patients undergoing de-novo catheter ablation for persistent AF were randomized in a 1:1 ratio into two different treatment arms: group A: pulmonary vein isolation (PVI) and, if low-voltage areas were present, a substrate modification. Group B: PVI and, if atrial fibrillation persisted, additional ablations, such as linear ablation and/or ablation of non-PV triggers. A total of 50 patients were randomized into each group without significant differences in baseline characteristics. During a mean follow-up of 17.64 ± 4.5 months after a single procedure, 34 (68%) patients of group A were free of arrhythmia recurrence versus 28 (56%) patients in group B (p = ns). In group A, 30 (60%) patients did not show endocardial fibrosis and received solely PVI. Both procedures were performed with a low number of complications; no pericardial effusion or stroke were seen in either group. CONCLUSIONS: A significant proportion of patients with persistent atrial fibrillation do not show low-voltage areas. A total of 70% of the patients receiving solely PVI did not show any recurrence of atrial fibrillation, and therefore, extensive additional ablation should be avoided in de-novo patients.

A leadless pacemaker in the real-world setting: Patient profile and performance over time.

Background: While prior Micra trials demonstrated a high implant success rate and favorable safety and efficacy results, changes in implant populations and safety over time is not well studied. The objective of this analysis was to report the performance of Micra in European and Middle Eastern patients and compare to the Micra Investigational Device Exemption (IDE) and Micra Post Approval Registry (PAR) studies. Methods: The prospective, single-arm Micra Acute Performance European and Middle Eastern (MAP EMEA) registry was designed to further study the performance of Micra in patients from EMEA. The primary endpoint was to characterize acute (30-day) major complications. Electrical performance was analyzed. The major complication rate through 12 months was compared with the IDE and PAR studies. Results: The MAP EMEA cohort (n = 928 patients) had an implant success rate of 99.9% and were followed for an average of 9.7 ± 6.5 months. Compared to prior studies, MAP EMEA patients were more likely to have undergone dialysis and have a condition which precluded the use of a transvenous pacemaker (p < .001). Within 30 days of implantation, the MAP EMEA cohort had a major complication rate of 2.59%. Mean pacing thresholds were low and stable through 12 months (0.61 ± 0.40 V at 0.24 ms at implant and 12 months). Through 12 months post-implantation, the major complication rate for MAP EMEA was not significantly different from IDE (p = .56) or PAR (p = .79). Conclusion: Despite patient differences over time, the Micra leadless pacemaker was implanted with a high success rate and low complication rate, in-line with prior reports.

Usefulness of wearable electrocardiography devices in patients experiencing paroxysmal cardiac-related symptoms: A case series of the "CardioSecur" system.

Background: Electrocardiograms (ECGs) recorded with wearable devices and additional smartphone apps play an increasing role in cardiology. Case summaries: We present two cases in which it was possible to record an ECG during cardiac-related symptoms using the patients' smartphones. Previous standard resting and 24-hour ECGs had revealed no pathologies. In one case, AV nodal reentry tachycardia was detected and treated accordingly. In the second case, ischemic ECG changes were recorded in a young woman without cardiovascular risk factors during a chest pain episode. Suspecting a coronary vasomotion disorder, an invasive diagnostic procedure was performed. The acetylcholine spasm provocation test revealed coronary microvascular spasm and appropriate therapy was initiated. Discussion: Smartphone-based ECG systems which can be used by the patient independently while experiencing cardiac-related symptoms are a modern diagnostic tool. Considering the use of these systems is beneficial for early diagnosis and appropriate treatment for paroxysmal arrhythmias and coronary vasomotion disorders.

Pulmonary vein isolation using cryoballoon ablation versus RF ablation using ablation index following the CLOSE protocol: A prospective randomized trial.

BACKGROUND: The single procedure success rates of durable pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (AF) vary between 80% and 90%. This prospective, randomized study investigated the efficacy of cryoballoon PVI (CBA) versus PVI with radio-frequency (RF)-energy following the CLOSE protocol (ablation index [AI], interlesion distance ≤6 mm, surround flow catheter) in terms of single-procedure arrhythmia-free outcome and safety. METHODS AND RESULTS: A total number of 150 patients undergoing de novo catheter ablation for paroxysmal AF were randomized to two different treatment arms. In group A patients, PVI was performed with the 23 or 28 mm cryoballoon (Artic Front™ Balloon in conjunction with an Achieve Mapping Catheter, Medtronic Inc.). The ablation procedure in group B was performed with RF-energy, using AI and following the CLOSE protocol. PVI using AI incorporates stability, contact force (CF), time, and power. The CLOSE protocol combines AI and ≤6 mm interlesion distance using a surround flow catheter (Biosense Webster Thermocool STSF). A total of 75 patients were randomized into each group without significant differences in baseline characteristics. During a mean follow-up of 12 ± 4.5 months after a single procedure, 64 (85.33%) patients of group A were free of arrhythmia recurrence versus 65 (86.67%) patients in group B (p = ns). A total of 14 patients (group A: 7 [9.33%]; group B: 7 [9.33%]; p = ns) underwent a redo-procedure. No significant difference between both groups was observed in terms of PV recovery (group A: 4 [5.33%] vs. group B: 3 [4%]; p = ns). In two patients of group A and four patients of group B, the PVs were durably isolated, whereas the patients had AF recurrence caused by extra-PV AF sources. Two patients of each group had continued paroxysmal AF but did not undergo redo-procedure. Patients of group A showed significantly more AF recurrence during the blanking period of 3 months (group A: 14 [18.67%] vs. group B: 6 [8%]; p < .05). With regard to the procedural data, the procedure time was significantly shorter in group A (70.53 ± 16.13 vs. 115.35 ± 15.38; p < .01); the flouroscopy time and dose area product showed no significant differences (Table 2). Both procedures were performed with a low number of complications; no pericardial effusion was seen in either group; in group A two patients had a significant hematoma of the groin with the need for surgical repair. CONCLUSIONS: Cryoballoon PVI and PVI using ablation index following the CLOSE protocol are equally efficient in achieving durable PV isolation. In this study, cryoballoon ablation led to significantly more AF recurrence during the blanking period.

Improved durable pulmonary vein isolation with shorter procedure times and lower energy levels using RF ablation with ablation index and a stringent lesion contiguity.

BACKGROUND: The single procedure success rates of durable pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (PAF) varies between 80 and 90%. Ablation index, incorporating contact force, stability, time and power is a more profound parameter of significant lesion size and has been established. Equally important is a stringent contiguity of the lesion set. METHODS AND RESULTS: A total number of 100 consecutive patients undergoing de-novo catheter ablation for paroxysmal atrial fibrillation (PAF) were analyzed between 2016 and 2019. In the first 50 patients (group A) PVI was performed using a surround flow, contact force catheter (Biosense Webster Thermocool STSF, Biosense Webster, USA) with a drag-and-ablate technique to encircle the PVs. In the following 50 patients (group B), PVI was performed using ablation index and a stringent lesion contiguity with an interlesion distance (ILD) of <5 mm. The baseline characteristics showed no significant differences between both groups. During a mean follow-up of 18 ± 3 months after a single procedure, 36 (72%) patients of group A were free of arrhythmia recurrence versus 43 (86%) patients in group B (p = 0.047). A total of 14 patients (group A: 10 (20%), group B: 4 (8%); underwent a redo-procedure. 7 patients of group A (14%) and 2 patients of group B (4%) showed recovered veins. In 3 patients of group A and 2 patients of group B the PVs were durably isolated. In these patients persistent AF recurrence was caused by extra-PV AF sources. Four patients of group A and three patients of group B had continued paroxysmal or persistent AF but did not undergo redo-procedure. With regard to the procedural data, the procedure time, the total energy and the fluoroscopy time were significantly lower in group B (AI and ILD <5 mm) (128.86 ± 18.19 versus 115.35 ± 15.38; p < 0.05; 1619.16 ± 988.56 versus 1186.26 ± 756.34; p < 0.05; 11.49 ± 3.20 versus 9.66 ± 3.86; p = 0.04). Both procedures were performed with a low number of complications, no pericardial effusion was seen in either group. CONCLUSIONS: PVI using ablation index in combination with a stringent lesion contiguity improves clinical outcome after first-time PVI with lower PVI recovery, shorter procedure times, lower total energy and shorter fluoroscopy times and therefore, is more efficient.

Implantation of leadless pacing systems in patients early after tricuspid valve surgery: A feasible option.

BACKGROUND: After tricuspid valve (TV) surgery due to tricuspid regurgitation (TR), patients needing a permanent pacemaker often receive an epicardial lead implantation. This may result in delayed recovery from open-chest surgery and increased postoperative risk. Leadless pacemaker (LPM) implantation may represent a valuable option. METHODS AND RESULTS: A total of 14 consecutive patients underwent LPM implantation (Micra Transcatheter Pacing System, Medtronic, Minneapolis, MN) early after TV surgery. The pacing indication in those patients was atrial fibrillation with a slow atrio-ventricular (AV) conduction or atrial fibrillation and a concomitant AV block III. Three patients already had a pacemaker prior to surgery, which was explanted during TV repair. Three patients received a valve replacement with a bioprosthesis, while the remaining eight patients received a TV repair. All procedural data and device measurements during and after LPM implantation were recorded. Transthoracic echocardiography was performed prior and post LPM implantation, showing no changes in TV or bioprosthesis performance. The device measurements were within an adequate range: threshold: 0.83 ± 0.34 V @ 0.24 ± 0 ms, impedance: 480 ± 58.88 ohm, and R-wave: 10.10 ± 3.60 mV. LPM implantation was successful in all patients with a mean procedural time of 32 ± 11.8 minutes, fluoroscopy time of 3.71 ± 3.15 minutes, and dose-area product of 536.67 ± 811.26 cGy/m2 . CONCLUSIONS: Implantation of an LPM early after TV surgery is a feasible option. LPM implantation does not affect TV or bioprosthesis performance in transthoracic echocardiography.

Complications and associated healthcare costs of transvenous cardiac pacemakers in Germany.

Aim: This study evaluated the occurrence and associated costs of pacemaker complications in Germany from 2010 to 2013. Patients & methods: Patients with a de novo or replacement implantation of a single or dual chamber pacemaker between 2010 and 2013 were followed for 12 months post-implant using German health insurance claims data. A case-control analysis was performed using propensity score matching to estimate the costs of complications. Results: Out of 12,922 implanted patients, 12.0% had a complication in the year following the implant. Complications related to lead and pocket were found in 10.2% of all implanted patients; infections occurred in 1.7% patients. Healthcare costs up to 36 months post complication were on average €4627 higher than for pacemaker patients without a complication. Conclusion: Pacemaker complications are common and represent a burden for patients and healthcare systems generating substantial costs. Most of the pacemaker complications involved the pacing lead or pacemaker pocket.

Predictors of successful complex catheter ablation for persistent atrial fibrillation despite failure of targeted procedural arrhythmia termination.

INTRODUCTION: Procedural atrial fibrillation (AF) termination is considered as a predictor of long-term success after catheter ablation for persistent AF (persAF). However, some patients remain free of arrhythmia recurrences despite failure to achieve AF termination. The objective of this study was to assess long-term outcome and prognostic factors in patients undergoing complex ablation without procedural AF termination. METHODS AND RESULTS: This study comprised 419 patients (63.8 ± 10.2 years, 63.4% male) undergoing complex ablation for persAF. Patients without procedural AF termination (n = 137, 64.2 ± 9.7 years, 63.5% male) were categorized into patients who remained in sinus rhythm (SR) in long-term outcome (SR-group) and patients with recurrence of AF or atrial tachycardia (AT) (AR-group). During a follow-up (FU) of 19.6 ± 14.6 months, the SR-group consisted of 65 (47.5%) and the AR-group of 69 (50.4%) patients. Three patients (2.2%) were lost to FU. Left atrial appendage (LAA) flow velocity and left atrium volume index (LAVI) could be identified as predictors for long-term success. LAA flow velocity and baseline AF cycle length (AFCL) were significantly associated with the type of arrhythmia recurrence (AF vs AT), ie, higher values of both are predictive for AT rather than AF recurrences. Patients with a LAVI < 34.4 mL/m² and significant AFCL increase during the ablation procedure had rather AT than AF recurrences. CONCLUSION: Patients with an arrhythmia-free outcome despite failure of procedural AF termination during complex ablation for persAF are characterized by specific morphological and functional properties that are easy to obtain.

Incidence and costs of cardiac device infections: retrospective analysis using German health claims data.

AIM: Estimate incidence and costs of cardiac device infections (CDIs) in Germany. MATERIALS & METHODS: Patients had an implantable cardioverter defibrillator implanted over 2010-2013 and were followed to December 2014 using German health insurance claims data. A case-controlled analysis was performed using propensity score matching methods. RESULTS: Risk of CDI 12 months post-implant was 3.4% overall, either 2.9% for de novo procedures versus 4.4% for replacement procedures. Mean 3-year incremental expenditure per patient for patients with CDI compared with controls was €31,493 for de novo implant patients and €33,777 for replacement patients. Mean incremental expenditure was €59,419 per patient with a major infection. CONCLUSION: CDIs are highly expensive to manage, reinforcing the need for strategies to reduce their occurrence.

Cardiac arrhythmias in patients with Danon disease.

AIMS: Different cardiac arrhythmias have been suggested to be associated with Danon disease, e.g. Wolff-Parkinson-White syndrome. However, a systematic electrophysiological investigation of patients with Danon disease is lacking thus far. METHODS AND RESULTS: Seven patients with Danon disease (4 males, 35.8 ± 10.8 years; 3 females, 51.3 ± 19.9 years) from 3 different families were studied. In all patients, the presence of Danon disease was confirmed by western blot of biopsy material or genetic testing. The patients were characterized by 12-lead electrocardiogram (ECG), Holter ECG, echocardiography, and serial implantable cardioverter defibrillator (ICD) interrogations (in ICD recipients). All male patients underwent electrophysiological investigation (EP study). Asymptomatic ventricular tachyarrhythmias were documented in six of the seven patients. Moreover, 5 of the 7 patients suffered from atrial fibrillation (AF), with 1 of them experiencing thromboembolic stroke at the age of 30 years. In male patients, the initial QRS complex was characterized by a slurring upstroke and shortened PQ interval mimicking ventricular pre-excitation. One male patient showed initial QRS complex slurring with prolonged PR interval. However, the presence of an accessory pathway was excluded by an EP study in all patients. In female patients, initial QRS complex slurring was significantly less distinct. In four patients, ICD implantation was performed for primary prevention of sudden cardiac death. However, sustained ventricular arrhythmias were not documented in any of the patients. CONCLUSIONS: The present study indicates that the distinct surface ECG pattern in Danon disease is not associated with ventricular pre-excitation. Atrial fibrillation is frequently observed in these patients and may be associated with thromboembolic events in the young, while sustained ventricular arrhythmias occur less frequently than previously reported.

[Surface ECG characteristics of right and left atrial flutter]. / Oberflächen-EKG-Charakteristika von rechts- und linksatrialem Vorhofflattern.

INTRODUCTION: Atrial tachycardia in virtually all areas of both atria has become more important in the clinical management of patients with previous complex atrial fibrillation ablation. Accurate interpretation of surface electrocardiogram (ECG) characteristics is of paramount importance to localize the origin of atrial tachycardia, particularly for planning interventional treatment. This article highlights the ECG features of different types of right and left atrial tachycardia. DEFINITION: Typical right atrial flutter through the cavotricuspid isthmus conducts septally in a cranial direction and demonstrates sawtooth-like flutter waves which start negative in II, III and aVF and then show a steep slope upwards to the isoelectric line. The flutter rate typically ranges between 240-250 beats/min. In contrast, right atrial flutter in a clockwise rotation, flutter around the vena cava inferior or superior and around a scar (e.g. after cardiac surgery) show positive or biphasic flutter waves (lower or upper loop reentry). Left atrial flutter waves (e.g. around the mitral valve or around the pulmonary veins) are very heterogeneous and are typically positive in V1 as the left atrium is located in the posterior mediastinum. CONCLUSION: Specific knowledge of flutter wave morphology in surface ECG facilitates planning and performance of the ablation strategy.

Primary Persistent Atrial Fibrillation: A Distinct Arrhythmia Subentity of an Ablation Population.

INTRODUCTION: Persistent atrial fibrillation (persAF) can occur either as a sustained arrhythmia that has progressed from initially paroxysmal AF or as primary persAF without a history of any spontaneously terminated episode. There is a paucity of data differentiating between the 2 different persAF entities. Thus, we prospectively evaluated baseline characteristics, electrophysiological features, and ablation outcome in these 2 patient cohorts. METHODS AND RESULTS: A total number of 154 consecutive persAF patients (63 ± 10 years, f = 42, longstanding persAF = 60) were characterized in terms of having primary persAF (P-persAF group) or persAF that secondarily progressed from paroxysmal AF (S-persAF group). All patients underwent de novo catheter ablation using the stepwise approach. PersAF entities were characterized by detailed patient history, sequential Holter monitoring, and reports of documented modes of AF conversion, respectively. The P-persAF group had a higher number of young patients (<50 years), a shorter AF history, and a higher number of congestive heart failure. The HATCH score did not differ between the groups. Procedural AF termination rate was significantly higher in S-persAF than in P-persAF patients (n = 55 [81%] vs. n = 58 [68%], P = 0.043). At 1-year follow-up, the arrhythmia-free survival after a single procedure was significantly lower in patients with P-persAF (26% vs. 43%, P = 0.016). Categorization to P-persAF was the strongest independent predictor of arrhythmia recurrence. CONCLUSIONS: P-persAF seems to be a specific arrhythmia entity that is associated with a lower AF-termination rate and a worse outcome after catheter ablation as compared to S-persAF.

Arrhythmia Termination Versus Elimination of Dormant Pulmonary Vein Conduction as a Procedural End Point of Catheter Ablation for Paroxysmal Atrial Fibrillation: A Prospective Randomized Trial.

BACKGROUND: Pulmonary vein isolation (PVI) is still associated with a substantial number of arrhythmia recurrences in paroxysmal atrial fibrillation (AF). This prospective, randomized study aimed to compare 2 different procedural strategies. METHODS AND RESULTS: A total of 152 patients undergoing de novo ablation for paroxysmal AF were randomized to 2 different treatment arms. The procedure in group A consisted of PVI exclusively. In this group, all isolated PVs were challenged with adenosine to reveal and ablate dormant conduction. In group B, PVI was performed with the patient either in spontaneous or in induced AF. If AF did not terminate with PVI, ablation was continued by targeting extra-PV AF sources with the desired procedural end point of termination to sinus rhythm. Primary study end point was freedom from arrhythmia during 1-year follow-up. In group A, adenosine provoked dormant conduction in 31 (41%) patients with a mean of 1.6±0.8 transiently recovered PVs per patient. Termination of AF during PVI was observed in 31 (65%) patients, whereas AF persisted afterward in 17 (35%) patients. AF termination occurred in 13 (76%) patients by AF source ablation. After 1-year follow-up, significantly more group B patients were free of arrhythmia recurrences (87 versus 68%; P=0.006). During redo ablation, the rate of PV reconduction did not differ between both groups (group A: 55% versus group B: 61%; P=0.25). CONCLUSIONS: Elimination of extra-PV AF sources after PVI is superior to sole PV isolation with the adjunct of abolishing potential dormant conduction. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02238392.

The Incidence of Audible Steam Pops Is Increased and Unpredictable With the ThermoCool® Surround Flow Catheter During Left Atrial Catheter Ablation: A Prospective Observational Study.

INTRODUCTION: Open irrigated radiofrequency (RF) ablation catheters with a porous tip (56 holes, TC-SF) permit delivering RF energy in a temperature-controlled mode without temperature rise. This prospective observational study investigated the association of different catheter parameters on the occurrence of audible steam pops during left atrial (LA) ablation. METHODS AND RESULTS: A total of 226 patients underwent TC-SF catheter ablation for atrial fibrillation. RF power delivery, impedance and catheter tip temperature were continually recorded throughout the ablation. Pulmonary vein isolation was performed with a maximum of 27 W and LA electrogram-guided or linear ablation with a maximum of 30 W. A total of 59 audible steam pops occurred, 2 of them resulting in pericardial tamponade. In the initial 89 patients, with an irrigation flow rate of 10 mL/min, 18 steam pops with one tamponade occurred in 12 (14%) patients. Subsequently, the irrigation flow rate was increased to 20 mL/min in the following 137 patients, resulting in the occurrence of 41 steam pops including one case of tamponade in a total of 30 (22%) patients. The maximal power was significantly higher in RF applications associated with a pop than those that did not. In only 12 (20%) steam pops, a significant impedance change occurred immediately before pop occurrence (4 [7%] impedance rise >10 ohm, 8 [13%] impedance drop >15 ohm). CONCLUSIONS: The TC-SF catheter does not provide sufficient feedback from the ablated tissue to prevent steam popping.

Body surface potential mapping for mapping and treatment of persistent atrial fibrillation.

Techniques facilitating individual mapping and ablation of arrhythmogenic substrates are desired to enhance our understanding of persistent atrial fibrillation (persAF) mechanisms as a prerequisite to increasing the success rates of single procedure persAF catheter ablation. The technique of body surface potential mapping (BSM) involves the use of multiple electrodes to collect the potentials over a large body surface area and, with the use of a computed tomography scan, it facilitates their correlation to a 3D model of the atrial structures. During AF,the visualization and localization of AF driver activity, both reentrant and focal wavefronts, is possible with this technique. The ECVUE system from CardioInsight was examined for this indication in clinical studies and showed a termination rate of persAF of 63 % in a large multicenter trial (AFACART) with a promising low recurrence rate during follow-up. From our initial experience, the system appears to be effective in persAF patients who have continuous AF for less than 1 year. However, the utility of the system for highly challenging cases like long-standing persistent AF and patients with very short AF cycle length remains to be explored. Further studies are needed to confirm these data and answer the multitude of open questions in this field.

Reduction of ICD shock burden by eliminating back-up pacing induced ventricular tachyarrhythmias.

INTRODUCTION: Implantable cardioverter defibrillators (ICD) may have the capacity to provoke or worsen ventricular tachyarrhythmias (VT). It has been reported that ICD shocks by itself can increase mortality. This study aimed to determine the role of back-up pacing-induced VT (PIT) in the overall ICD shock burden by avoiding pause-related ventricular back-up pacing. METHODS AND RESULTS: A population of 550 single-chamber ICD patients was studied. Of them, 17 (3%, 69 ± 16 years, 14 male) patients had documented episodes of PIT. A total of 431 VT episodes were documented including 89 (21%) due to PIT. In 3 patients, VT events were exclusively PITs. After ≥2 documented PITs, the pacing output for VVI pacing was set to a subthreshold level resulting in noncapturable ventricular back-up pacing. All other device parameters remained unchanged to prove a potential proarrhythmic effect of pause related back-up pacing. During a follow-up of 99 ± 39 months after reducing the pacing output to a subthreshold level, no further episodes of PIT were observed (P < 0.001). Moreover, with the prevention of PITs, the ICD shock burden decreased significantly (pre: 150 vs. post: 18, P < 0.001). However, a single event of pause-induced VT occurred due to missing back-up pacing. CONCLUSIONS: PIT is a frequent mechanism of VTs in ICD patients resulting in a substantially increased shock burden. Elimination of pause-related back-up pacing by subthreshold pacing output effectively abolishes PIT and thus significantly reduces ICD shock burden.

Prognostic role of subsequent atrial tachycardias occurring during ablation of persistent atrial fibrillation: a prospective randomized trial.

BACKGROUND: The role of subsequent atrial tachycardias (AT) in the context of persistent atrial fibrillation (AF) remains undetermined. This study evaluated the prognostic role of subsequent ATs for arrhythmia recurrences after catheter ablation of persistent AF. METHODS AND RESULTS: A total of 110 patients with persistent AF (63±9 years; 22 women; 61 long-lasting persistent AF) underwent pulmonary vein isolation followed by electrogram-guided ablation. After AF terminated to AT, patients were separated by the randomization protocol to receive either direct cardioversion (group A) or further ablation of subsequent ATs to sinus rhythm (group B). After a mean follow-up of 20.1±13.3 months after the first procedure, significantly more group B patients were in sinus rhythm as compared with patients in group A (30 [57%] versus 18 [34%]; P=0.02). Moreover, recurrences of AF were significantly less frequent of group B than in group A patients (10 [19%] versus 26 [49%]; P=0.001). After the last procedure (follow-up, 34.0±6.4 months), significantly more group B patients were free of AF as compared with patients of group A (49 [92%] versus 39 [74%]; P=0.01). The proportion of AT recurrences did not differ between the 2 groups after the first and final procedures. The strongest predictor for an arrhythmia-free survival after a single procedure was randomization to the procedural end point of termination to sinus rhythm by elimination of subsequent ATs (P=0.004). CONCLUSIONS: Catheter ablation of subsequent ATs increases freedom from AF but not AT, suggesting a contributing role of subsequent ATs in the mechanisms of persistent AF. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01896570.

The relationship of bipolar left ventricular pacing stimulus intensity to cardiac depolarization and repolarization in humans with cardiac resynchronization devices.

BACKGROUND: Myocardial depolarization can be altered by varying pacing stimulus output. This may have implications on response rates for cardiac resynchronization therapy (CRT). The purpose of our study was to determine the relationship of left ventricular (LV) pacing stimulus intensity to measures of depolarization and repolarization in humans with CRT devices. METHODS: In 37 patients with a CRT device and bipolar LV leads, bipolar LV-only pacing from maximum output to threshold was performed. The presence of changes in depolarization was defined by predetermined changes in ECG morphology that accompanied a change in bipolar stimulus amplitude. ECG parameters and the EGMs were analyzed at various LV pacing stimulus intensities. RESULTS: Changes in ECG morphology were apparent in 70% of patients. These occurred at a mean LV stimulus amplitude of greater than 2.7 +/- 0.8 V at 1 ms. Of the patients with changes in surface ECG, the transventricular conduction time decreased from 155 +/- 41 ms at low output to 141 +/- 39 ms at high output (P < 0.01). Despite a significant reduction in QRS duration with high output, mean QTc and JTc interval increased with increasing LV stimulus strength (539 +/- 45 vs 559 +/- 46 ms (P < 0.01) and 353 +/- 31 ms vs 377 +/- 32 (P < 0.01)). CONCLUSION: Increased LV stimulus intensity, independent of RV anodal capture, is associated with faster transventricular conduction time, changes in myocardial depolarization, and longer QT intervals. These findings have important implications on the relationship of programmed LV pacing output to pacing-induced proarrhythmia and clinical CRT response rates.