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We present a case of a 79-year-old man on apixaban for atrial fibrillation who suffered multiple ischaemic strokes and was found to have mobile structures attached to his pacemaker lead on transesophageal echocardiography. Based on the Modified Duke Criteria, there was no evidence of infectious endocarditis. Since there were no signs of a patent foramen ovale or arteriovenous malformations in the lungs, the mobile structures probably were not the cause of the ischaemic strokes. After the visualisation of the mobile structures, apixaban was switched to dabigatran with a clear decrease in the size of the structures. Blood cultures remained negative and there was no fever or increase in inflammatory parameters. It was therefore suspected that the structures were thrombus material rather than vegetations of infectious endocarditis.There is uncertainty surrounding the clinical relevance and indication for treatment of incidentally found mobile structures on pacemaker leads. Multiple studies with different imaging modalities show a significant difference in the prevalence of thrombi. More studies with longer follow-ups are needed to investigate the prevalence and need for treatment of these incidentally found structures on pacemaker leads.

Background: Leadless pacemakers (PMs) were recently introduced to overcome lead-related complications. They showed high safety and efficacy profiles. Prospective studies assessing long-term safety on cardiac structures are still missing., Objective: The purpose of this study was to compare the mechanical impact of Micra with conventional PM on heart function., Methods: We conducted a non-inferiority trial in patients with an indication for single chamber ventricular pacing. Patients were 1:1 randomized to undergo implantation of either Micra or conventional monochamber ventricular pacemaker (PM). Patients underwent echocardiography at baseline, 6 and 12 months after implantation. Analysis included left ventricular ejection fraction (LVEF), global longitudinal strain (GLS) and valve function. N-terminal-pro hormone B-type natriuretic peptide (NT-pro-BNP) levels were measured at baseline and 12 months., Results: Fifty-one patients (27 in Micra group and 24 in conventional group) were included. Baseline characteristics were similar for both groups. At 12 months, (1) the left ventricular function as assessed by LVEF and GLS worsened similarly in both groups (∆LVEF -10 ± 7.3% and ∆GLS +5.7 ± 6.4 in Micra group vs. -13.4 ± 9.9% and +5.2 ± 3.2 in conventional group) (p = 0.218 and 0.778, respectively), (2) the severity of tricuspid valve regurgitation was significantly lower with Micra than conventional pacing (p = 0.009) and (3) median NT-pro-BNP was lower in Micra group (970 pg/dL in Micra group versus 1394 pg/dL in conventional group, p = 0.041)., Conclusion: Micra is non inferior to conventional PMs concerning the evolution of left ventricular function at 12-month follow-up. Our data suggest that Micra has a comparable mechanical impact on the ventricular systolic function but resulted in less valvular dysfunction., (© 2023 Wiley Periodicals LLC.)

Introduction: MARVEL 2 assessed the efficacy of mechanical atrial sensing by a ventricular leadless pacemaker, enabling a VDD pacing mode. The behavior of the enhanced MARVEL 2 algorithm during variable atrio-ventricular conduction (AVC) and/or arrhythmias has not been characterized and is the focus of this study., Methods: Of the 75 patients enrolled in the MARVEL 2 study, 73 had a rhythm assessment and were included in the analysis. The enhanced MARVEL 2 algorithm included a mode-switching algorithm that automatically switches between VDD and ventricular only antibradycardia pacing (VVI)-40 depending upon AVC status., Results: Forty-two patients (58%) had persistent third degree AV block (AVB), 18 (25%) had 1:1 AVC, 5 (7%) had variable AVC status, and 8 (11%) had atrial arrhythmias. Among the 42 patients with persistent third degree AVB, the median ventricular pacing (VP) percentage was 99.9% compared to 0.2% among those with 1:1 AVC. As AVC status changed, the algorithm switched to VDD when the ventricular rate dropped less than 40 bpm. During atrial fibrillation (AF) with ventricular response greater than 40 bpm, VVI-40 mode was maintained. No pauses longer than 1500 ms were observed. Frequent ventricular premature beats reduced the percentage of AV synchrony. During AF, the atrial signal was of low amplitude and there was infrequent sensing., Conclusion: The mode switching algorithm reduced VP in patients with 1:1 AVC and appropriately switched to VDD during AV block. No pacing safety issues were observed during arrhythmias., (© 2021 The Authors. Journal of Cardiovascular Electrophysiology published by Wiley Periodicals LLC.)

Background: Permanent pacing is common after valve intervention. The presence of a conventional pacemaker in this population is recognized as a risk factor for infectious events. Therefore, a leadless pacing system could be the preferred strategy when permanent pacing is required after valve intervention., Aim: To report periprocedural outcomes and follow-up of patients undergoing implantation of a leadless pacing system after valve intervention., Methods: Patients with previous valve intervention at the time of attempted implantation of a leadless pacemaker (Micra™, Medtronic, Minneapolis, MN, USA) were included, and were compared with a control group (patients also implanted with Micra™ without valve intervention)., Results: Among a total of 170 Micra™ implantation procedures, 54 patients (31.8%) had a history of valve intervention: 28 after aortic valve replacement; 10 after mitral valve replacement; one after single tricuspid valvuloplasty; and 15 after multiple valve surgery. Median age of the patients was 82.5 (77.0-86.0) years and 53.7% were male. Patients with previous valve intervention had a higher incidence of arterial hypertension (P=0.014) and ischaemic heart disease (P=0.040). The primary indications for permanent pacing after valve intervention were high-degree atrioventricular block (59.3%) and atrial fibrillation with bradycardia (27.8%). Micra™ was successfully implanted in all patients (n=170) without any procedure-related major complications. During a median follow-up of 12 months, electrical performance was excellent and similar in both groups. Also, a similar reduction in left ventricular ejection fraction was observed at 12 months in both groups, which was correlated with the percentage of right ventricular pacing., Conclusion: A leadless pacemaker is safe and efficient after valve intervention, and therefore represents an effective pacing option in patients after valve intervention., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Background: The MARVEL (Micra Atrial TRacking Using a Ventricular AccELerometer) 2 study assessed the efficacy of atrioventricular (AV) synchronous pacing with a Micra leadless pacemaker. Average atrioventricular synchrony (AVS) was 89.2%. Previously, low amplitude of the Micra-sensed atrial signal (A4) was observed to be a factor of low AVS., Objective: The purpose of this study was to identify predictors of A4 amplitude and high AVS., Methods: We analyzed 64 patients enrolled in MARVEL 2 who had visible P waves on electrocardiogram for assessing A4 amplitude and 40 patients with third-degree AV block for assessing AVS at rest. High AVS was defined as >90% correct atrial-triggered ventricular pacing. The association between clinical factors and echocardiographic parameters with A4 amplitude was investigated using a multivariable model with lasso variable selection. Variables associated with A4 amplitude together with premature ventricular contraction burden, sinus rate, and sinus rate variability (standard deviation of successive differences of P-P intervals [SDSD]) were assessed for association with AVS., Results: In univariate analysis, low A4 amplitude was inversely related to atrial function assessed by E/A ratio and e'/a' ratio, and was directly related to atrial contraction excursion (ACE) and atrial strain (Ɛa) on echocardiography (all P ≤.05). The multivariable lasso regression model found coronary artery bypass graft history, E/A ratio, ACE, and Ɛa were associated with low A4 amplitude. E/A ratio and SDSD were multivariable predictors of high AVS, with >90% probability if E/A <0.94 and SDSD <5 bpm., Conclusion: Clinical parameters and echocardiographic markers of atrial function are associated with A4 signal amplitude. High AVS can be predicted by E/A ratio <0.94 and low sinus rate variability at rest., (Copyright © 2020 The Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Transvenous 3 permanent pacemaker-related infection is a severe condition associated with significant morbidity and mortality. Leadless pacemakers may be more resistant to bacterial seeding during bloodstream infection because of its small surface area and encapsulation in the right ventricle. This study reports the incidence and outcomes of bacteraemia in patients implanted with a Micra leadless pacemaker. We present 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) findings obtained in a subgroup of patients., Methods: We report a retrospective cohort study of 155 patients who underwent a Micra TPS implant procedure at the University Hospitals of Leuven between July 2015 and July 2019. We identified the patients who developed an episode of bacteraemia, proved by ≥2 positive blood cultures., Results: Of the 155 patients, 15 patients presented an episode of bacteraemia at a median of 226 days (range: 3-1129) days after the implant procedure. Gram-positive species accounted for 73.3% (n = 11) of the bacteraemia including Staphylococcus (n = 5), Enterococcus (n = 3), and Streptococcus (n = 3). The source of infection was identified in nine patients (60%) including endocarditis in four patients, urinary tract in three patients, and skin in two patients. 18 F-FDG PET/CT imaging performed in six patients did not show sign of infection around the leadless pacemaker. Bacteraemia was resolved in all patients after adequate antibiotherapy. Four patients died early during follow up. For all other patients, there were no recurrence of systemic infection during a median follow up of 263 days (range: 15-1134)., Conclusion: In our small cohort, no leadless pacemaker endocarditis was observed among patients with bacteraemia., (© 2020 Wiley Periodicals LLC.)

Background: The Micra Transcatheter Pacing System is implanted directly in the right ventricle (RV) through the femoral vein using a steerable transcatheter delivery system. The present study was done to identify determinants of difficult leadless pacemaker implant procedures including operator, patient, and RV anatomical characteristics., Methods: All patients who underwent a Micra implant from July 2015 to December 2018 at our center were analyzed. From an RV angiogram acquired during implantation, RV geometry including systolic and diastolic volumes and ejection fraction was characterized. The presence of septomarginal trabeculation was noted., Results: One hundred twenty-six patients (mean age: 79 ± 11 years old, mostly male: 77%) were enrolled. Mean Micra RV implant procedure time was 24 ± 23 min, with 1.7 ± 1.3 deployments of the device. No significant change in implant procedure time was observed after the first 30 implants. Eleven patients had a prominent septal component of the septomarginal trabeculation in the RV. Univariate analysis showed that the procedure time was positively correlated with the presence of a prominent septal component of the septomarginal trabeculation (P < .001) or an episode of heart failure (P = .02) and negatively correlated with the number of procedures performed by the operator (P < .001). After multivariable analysis, only the presence of a prominent septal component of the septomarginal trabeculation (P < .001) and the number of procedures performed by the operator (P < .001) were associated with the implant procedure time., Conclusions: In our experience, implant procedure time of a Micra leadless pacemaker depended on the presence of a prominent septal component of the septomarginal trabeculation and operator experience., (© 2020 Wiley Periodicals LLC.)

Background: With its steerable transcatheter delivery system, the Micra can be deployed in nonapical positions within the right ventricle, potentially allowing reduction of the paced QRS width. We sought to evaluate the safety and long-term performance of the right ventricular outflow tract (RVOT) pacing using the Micra transcatheter pacing system (TPS). We also compared the paced QRS between RVOT, mid-septal, and apical implant positions., Methods: All patients who underwent a Micra TPS implantation at the University Hospitals of Leuven were enrolled in this observational study. Right ventricular (RV) position of the device was assessed on per-procedural ventriculography. Paced QRS was analyzed and follow-up completed at 1 month and then every 6 months., Results: Among the 133 patients included (mean follow-up: 13 ± 11 months), 45 were implanted in the RVOT, 58 midseptally, and 30 at the apex. All implant procedures were successful and no pericardial effusion was encountered within the 30 days post-implant. Two major complications were reported with devices implanted at the apex. Pacing impedance was significantly higher in the RVOT compared to the mid-septal and apical position (P < .001). Pacing threshold and R-wave amplitude did not differ over time in either position. The median narrowest paced QRS duration was observed in the RVOT (142 ms) compared to mid-septal (159 ms; P < .001), and apical position (181 ms; P < .001)., Conclusion: Implantation of the Micra TPS in the RVOT is safe and feasible. Electrical performance over time was comparable to mid-septal and apical positions. The narrowest paced QRS complexes is achieved with RVOT pacing., (© 2019 Wiley Periodicals, Inc.)

Introduction: The MARVEL study demonstrated at a single time point that accelerometer (ACC)-based atrial sensing improves atrioventricular (AV) synchrony (AVS) in patients with AV block and a Micra pacemaker (Medtronic, Minneapolis, MN, USA). The purpose of the MARVEL Evolve substudy was to assess the performance over time., Methods: This prospective single-center study compared AVS and ACC signals at two visits ≥6 months apart. Custom software was temporarily downloaded into the Micra at each visit and AVS was measured during 30 min at rest., Results: Nine patients from the MARVEL study were enrolled. The mean (±standard deviation) age was 82.3 ± 6.0 years old, 67% were male, and a Micra was implanted for 6.0 ± 6.4 months. High-degree AV block was present in four patients, whereas five with predominantly intrinsic conduction required intermittent pacing for bradycardia. The mean interval between visits was 7.1 ± 0.6 months. Seven patients had normal sinus node function at both visits and were included in a paired analysis. Both ACC signal amplitude (visit 2-visit 1 = 1.4 mG; 95% confidence interval [CI] [-25.8 to 28.4 mG]; P = 0.933) and AVS (visit 1: 90.8%, 95% CI [72.4, 97.4] and visit 2: 91.4%, 95% CI [63.8, 98.5]; P = 0.740) remained stable. Three patients had spontaneous atrial tachycardia. During atrial fibrillation, no atrial contraction was detected or tracked. During atrial flutter, intermittent tracking resulted in a ventricular rate of 60 ± 8 beats per minute (bpm); there was no ventricular pacing >100 bpm., Conclusion: ACC signals amplitude and performance of AVS pacing were stable over time. During atrial arrhythmias, the AV synchronous pacing mode behaved safely., (© 2019 Wiley Periodicals, Inc.)

This report presents and discusses, on behalf of the Belgian College of Cardiology, the evolution of the peer review process in arrhythmology, focussing on pacemaker implantation. Data from the last 22 years are compared. The national annual increase in implants is around 1%, clinical patient characteristics remained stable over the years while dual chamber pacing was proportionally increasing. Analyses of the normalised sick sinus and complete atrioventricular block ratios revealed a quite homogenous practice between centres and patient district with the only exception of the two more crowded districts. Battery longevity and infection rate were also assessed. With an incidence of 1/1000 device-years follow-up, Belgium remains below accepted European levels.

Aim: Leadless cardiac pacemaker has been developed to reduce complications related to cardiac pacing and is considered as an alternative to conventional pacemaker although safety and efficacy data in clinical practice are limited. The purpose of this study was to investigate the safety and efficacy profile of Micra Transcatheter Pacing System (TPS) used in daily clinical activity with a focus on challenging cases for conventional pacing., Methods: A total of 66 patients (46 men, 79.1 ± 9.7 years) having a Class I or II indication for ventricular pacing underwent a Micra TPS implant procedure. All patients were enrolled in a prospective registry. Follow-up visits were scheduled at discharge and after 1, 3, 6 and 12 months., Results: Primary indication for pacing was third degree atrioventricular block (30.3%), sinus node dysfunction (21.2%) or permanent atrial fibrillation with bradycardia (45.5%). The device was successfully implanted in 65 patients (98.5%). During follow-up of 10.4 ± 6.1 months (range 1-23 months), electrical measurements remained stable. Mean pacing capture threshold, pacing impedance and R-wave sensing were respectively 0.57 ± 0.32 V, 580 ± 103 Ohms, 10.62 ± 4.36 mV at the last follow-up. One major (loss of function) and three minor adverse events occurred. Pericardial effusion, dislodgement, device related infection or pacemaker syndrome were not observed. Micra TPS implantation was straightforward for patients with congenital or acquired cardiac and/or vascular abnormalities, previous tricuspid surgery and after heart transplantation., Conclusion: Our experience confirms that implantation of Micra is safe and efficient in a real world population including patients who present a challenging condition for conventional pacing.

Background: Children from mothers with systemic lupus erythematosus are frequently born with congenital heart block. This study aimed at evaluating long-term outcome because long-term data are scarce., Methods: In the database of pediatric and congenital heart disease (University Hospitals Leuven), 19 children from systemic lupus erythematosus mothers and who were born with or developed atrioventricular block were identified. All records were reviewed for disease course and outcome., Results: Median follow-up time was 7 years (interquartile ranges [IQR] 4.5-13 years). One child had no heart block at birth and developed only a first-degree block during follow-up. One had a second-degree heart block and developed a complete heart block. Seventeen patients (89%) were born with a complete heart block. Seventeen patients (89%) needed a definitive pacemaker. In all, epicardial leads were used at first implantation. Eighty-two percent received their pacemaker in the first year of life. The first battery had a median lifetime of 5 years (IQR 3.5-5 years), the second 6 years (IQR 4.5-6.3 years), and the third 5 years (IQR 5-6 years). Note that 47% of patients needed a lead replacement due to lead problems. Only one pericardial tamponade after pacemaker implantation. No device or lead infections occurred. The left ventricular systolic function at latest follow-up was normal for all. No patients died., Conclusion: In children with heart block born from systemic lupus erythematosus mothers, an early need for pacemaker implantation was documented. The overall battery life was acceptable, but there was a high need for lead replacement. Complication rate was low. Late outcome was good., (© 2016 Wiley Periodicals, Inc.)

Objective: The choice between a resynchronization pacemaker (CRT-P) or defibrillator (CRT-D) is still a matter of debate. We hypothesised that when selecting patients based on co-morbidities and age as proposed by the ESC-guidelines, there would be no long-term survival benefit of CRT-D compared to CRT-P., Methods: We performed a retrospective analysis of patients who received a CRT device at the University Hospitals Leuven between 2001 and 2007. For the analysis of the association between predictors and outcome, uni- and multivariate Cox regression analyses were performed. We present data from three multivariate models., Results: A total of 144 CRT devices were implanted (CRT-D n=98, CRT-P n=46). Patients who received a CRT-P were older and had a higher prevalence of co-morbidities. Patients who received a CRT-D had a significant lower mortality. When applying incremental multivariate analysis using 1st variables with a P < 0.05 in univariate analysis, 2nd variables with a P < 0.10 and 3rd adding on top all the baseline variables that were significantly different between the two groups, the significance of a possible survival benefit for CRT-D over CRT-P disappeared: risk model 1, hazard ratio 2.21 (P = 0.008), risk model 2, HR 1.81 (P = 0.069), and risk model 3, HR 1.85 (P = 0.091). The use of amiodarone and the presence of COPD or renal insufficiency remained associated with a significant, higher mortality risk, while the use of beta blockers was protective in all three models., Conclusion: The choice of a CRT-D seemed a predictor of improved survival in simple but not in more complex multivariable analyses. The fact that the survival benefit strongly depended on the number of co-variables suggests that it is at most marginal.

Aims: Owing to the increasing use of cardiac implantable electronic devices, there is a growing need for safe and effective techniques to manage device-related complications and lead dysfunction. Lead extraction remains a challenging procedure with inherent risks. We present the 30-day and long-term outcomes of lead extractions in the University Hospitals Leuven., Methods and Results: We report a retrospective cohort study of 176 patients admitted to the University Hospitals Leuven between January 2005 and December 2011, for the transvenous extraction of 295 leads. Indications for extraction were lead dysfunction and device upgrade in 84 (47.7%), pocket infection in 61 (34.7%), and systemic infection in 31 patients (17.6%). Extraction was successful in 95.5% of patients with complete removal of the leads or only a minor fragment remaining. One fatal peri-procedural complication occurred. Thirty-day mortality was 3.4% (n = 6). Systemic infection was the only significant predictor of 30-day mortality [odds ratio (OR) 29.706; P = 0.029]. A lower level of haemoglobin prior to extraction also tended to be related with a higher mortality, but this was not significant (OR 2.024; P = 0.082). One-year mortality was 8.5% (n = 15). Systemic infection (OR 9.727; P = 0.009), a lower level of haemoglobin (OR 1.597; P = 0.05), and a higher level of ureum (OR 1.021; P = 0.017) prior to extraction were significant predictors of 1-year mortality. Systemic infection was associated with significantly higher 30-day (19%), 1-year (32%), and long-term (39%) mortality rates., Conclusion: Lead extraction can be safely and successfully performed in the majority of patients, with limited life-threatening complications. However, lead extraction because of systemic infection is associated with a significantly higher risk of short- and long-term mortality., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.)

Purpose: Worldwide, the number of transvenous extractions of chronically implanted endocardial leads rapidly increases. Despite great technical progress, lead extraction remains a challenging procedure with possible life-threatening complications. We present the success and complication rate of lead extractions in the University Hospitals Leuven, and investigated a possible relationship between the use of powered sheaths and lead type, fixation, location and implantation time., Methods: We present an observational retrospective cohort study of 157 patients admitted to the University Hospitals Leuven between January 2005 and December 2010, for the transvenous removal of a total of 259 endocardial leads., Results: Complete procedural success was achieved in 92% of patients (n = 144). Of all leads, 94% (n = 243) were completely extracted. Only in 5 patients (3%), lead extraction failed. Leads that could not be removed were significantly older (134.1 +/- 90.7 months vs. 73.1 +/- 61.9 months; P = 0.02). In the other 8 patients the leads were partially removed with a remaining major retained lead fragment in 2 and a minor fragment in 6 patients. Major procedural complication rate was 2.5% (n = 4). There were no procedure-related deaths. Powered sheaths were used significantly more for the extraction of defibrillator leads (51%) (vs. pacing leads (33%; P = 0.015)) and right ventricular located leads (43%) (vs. other location (28%; P = 0.011)). However, when comparing the need of powered sheaths for the extraction of right ventricular defibrillator leads vs. right ventricular pacing leads, only a trend to higher use was noticed (51 vs. 39%; P = 0.146). Powered sheath use was not related to fixation type. Leads that required the use of a powered sheath were implanted significantly longer (112 +/- 69.5 months vs. 41.7 +/- 33.7 months; P = 0.001)., Conclusions: Chronically implanted endocardial leads can be transvenously extracted in a high number of cases and with a low risk of procedural complications. Powered sheaths proved to be a helpful tool to extract leads that could not be removed by manual traction. Powered sheaths are necessary for leads with longer implantation duration and are more often used for the extraction of defibrillator leads.

As new algorithms are being developed to promote intrinsic atrioventricular conduction in preventing the deleterious effects of right ventricular pacing, more complex rhythm strips can be encountered. In our patient with a dual-chamber implantable cardioverter-defibrillator, such an algorithm resulted in a pacemaker-mediated tachycardia with several changes in cycle length.

Sensing in pacemakers (PMs) and implantable cardioverter defibrillators (ICDs) is crucial to normal device behaviour. Since both devices treat different arrhythmias, the technical approach to signal detection is also completely different. A PM has a fixed threshold of sensing, above which events are sensed and therapy of the device withheld. On the other hand, the defibrillator has a variable threshold of sensing to detect tachyarrhythmias, with sometimes very small and changing electrogram amplitudes. In this case report, we describe interference between a PM and an ICD caused by these differences in the detection of cardiac events, leading to undersensing of ventricular fibrillation at defibrillation threshold testing.

We describe the occurrence of a right-sided pneumothorax following a left-sided dual chamber pacemaker implantation, due to a perforation of the screw of the J-shaped active-fixation lead through the right atrial wall. A review of the literature regarding complications of different atrial lead types (passive vs. active and J-shape vs. straight) is provided. Current data suggest that passive-fixation leads could have an advantage, provided they can be positioned satisfactorily because of the lower risk of pericardial complications. If active-fixation leads are used, straight leads might be preferable above J-shaped leads because of the lower rate of perforation.

Objectives: This study tested the feasibility of automatically detecting advanced sleep disordered breathing (SDB) from a pacemaker trans-thoracic impedance sensor., Background: SDB is prevalent yet under-diagnosed in patients with cardiovascular disease. The potential for automated detection of SDB in patients receiving pacemakers with respiration sensors has not been fully explored. We hypothesized that the trans-thoracic impedance sensor could be utilized for automatic detection of advanced SDB., Methods: Patients underwent overnight polysomnography (PSG). The pacemaker trans-thoracic impedance signal was simultaneously recorded and time synchronized with the polysomnograph. Cardiovascular health variables were abstracted from medical records. Apnea was defined as cessation of inspiratory airflow lasting 10 seconds or longer. Hypopnea was defined as a reduction of tidal volume of at least 30% from baseline tidal volume, lasting 10 seconds or more. A computer algorithm (PM-A) was developed to automatically detect SDB from the pacemaker impedance sensor data. The performance of automated SDB detection was compared against PSG., Results: Sixty patients (aged 69 +/- 12 years, 45 males) were studied. Advanced SDB (moderate or severe) was diagnosed in 40 patients. Severe SDB (apnea-hypopnea index [AHI]> or = 30) was diagnosed in 32 patients (53%), but only 5 patients had prior diagnosis of the disease. Moderate SDB (30 > AHI > 15) was diagnosed in 8 patients of whom only two were previously diagnosed. Cardiovascular health variables did not predict the presence of advanced SDB. PM-A derived AHI correlated with that of the PSG (r = 0.80, P < 0.01). The algorithm identified patients with advanced SDB with 82% sensitivity and 88% specificity., Conclusions: It is feasible to automatically measure SDB severity using a pacemaker trans-thoracic impedance sensor. Advanced SDB was frequently undiagnosed in this cohort of pacemaker patients.

Objective: This study presents the long-term outcome of 321 epicardial leads in 138 patients., Methods and Results: All leads were Medtronic CapsureEpi model 4965 steroid eluting leads. The 1-, 3-, and 5-year patient survival was 91%, 83% and 77%, respectively.Twenty-seven patients died. In 25/27 deaths a pacing-related death could be excluded. Strangulation of the heart by an abandoned epicardial lead was the cause of death in one child. One other patient died suddenly at the age of 3 years. Failures occurred in 57 of 321 epicardial leads (18%). For all 321 leads, the 1-, 3- and 5-year freedom from failure was 91%, 85% and 71%, respectively. The cumulative proportion of patients without any lead defect was 85% after I year, 76% after 3 years and 62% after 5 years. The percentage of patients without serious adverse events at 1, 3, and 5 years was 97%, 91%, 85%, respectively. Lead fracture was the cause of failure in 15 leads of 9 patients. An important increase in pacing threshold occurred in 35 leads of 30 patients. Other failures were: diaphragmatic stimulation, infection, excessive traction and strangulation. Eighteen failures were repaired by 11 surgical interventions in 9 patients.Thirty-nine defects were corrected non-invasively in 31 patients., Conclusions: The use of steroid-eluting epicardial leads has proven to be an adequate option. In paediatric cardiology, the epicardial approach remains an indispensable tool for achieving a life-long pacing.

Aims: This study evaluated the acute clinical performance of a new ventricular automatic capture algorithm developed to work with all lead types and pacing vectors., Methods and Results: During regular pacemaker implant or replacement, AutoThreshold and manual threshold tests were performed in ventricular unipolar (UP) and bipolar (BP, if applicable) pacing using a customized external prototype INSIGNIA pacemaker. The success rate and accuracy of two different modes (commanded and ambulatory) of the automatic capture algorithm were used to evaluate the performance. Loss-of-capture events (two consecutive non-captured beats without backup pacing) were used to assess safety. Data of 53 patients (33 DDD/20 VVI) from four medical centres were analysed. Tested leads included 43 BP and 10 UP from nine manufacturers, and seven had electrodes with low polarization. The rate of successful commanded and ambulatory AutoThreshold tests was 96 and 94%, respectively, with an average absolute threshold difference compared with manual threshold of < 0.1 V at 0.4 ms (commanded 0.07 +/- 0.07 V and ambulatory 0.08 +/- 0.07 V). There was no significant difference in performance between UP/BP pacing, polarization, and lead type. No loss-of-capture event was observed., Conclusion: When successful, the ventricular automatic capture algorithm accurately determined pacing thresholds in either a UP or BP pacing configuration among all leads tested.

Respiration rate (RR) and minute ventilation (MV) provide important clinical information on the state of the patient. This study evaluated the accuracy of determining these using a pacemaker impedance sensor. In 20 patients who were previously implanted with a Guidant PULSAR MAX group of pacemakers, the telemetered impedance sensor waveform was recorded simultaneously with direct volume respiration waveforms as measured by a pneumatometer. Patients underwent 30 minutes of breathing tests while supine and standing, and a 10-minute ergonometer bicycle exercise test at a workload of 50 W. Breathing tests included regular and rapid-shallow breathing sequences. RR was determined by a computerized algorithm, from impedance and respiration signals. The mean RR by impedance was 21.3 +/- 7.7 breaths/min, by direct volume was 21.1 +/- 7.6 breaths/min, range 7-66, the mean difference of RR measured by the impedance sensor, as compared with the true measurement, being 0.2 +/- 2.1 breaths/min. During the entire exercise, the mean correlation coefficient between impedance (iMV) and direct measured MV was 0.96 +/- 0.03, slope 0.13 +/- 0.05 L/Omega and range 0.07-0.26 L/Omega. Bland-Altman limits of agreement were +/- 4.6 L/min for MV versus iMV with each patient calibrated separately. The correlation coefficient for iMV versus MV over the entire 10 minutes of exercise, including the initial 4 minutes of exercise, was 0.99. The transthoracic impedance sensor of an implanted pacemaker can accurately detect respiration parameters. There was a large variation between subjects in the iMV versus MV slope during a bicycle exercise test, whereas for each subject, the slope was stable during submaximal bicycle exercise.

We report on a patient in whom an active-fixation pre-shaped atrial lead caused perforation of the right atrial wall, pericardium and pleura, resulting in pericardial effusion and right-sided pneumothorax. Chest X-ray did not demonstrate protrusion of the atrial lead outside the cardiac silhouette but computed tomography visualized the tip of the helix of the atrial screw-in electrode outside the contours of the right atrial appendage touching the right upper lobe of the lung. The lead was repositioned with resolution of pericardial effusion and pneumothorax. Due to their proximity to the right lung, high anterolaterally positioned atrial screw-in leads carry a small but definite risk for right-sided pneumothorax.

Automatic mode switching algorithms of dual chamber pacemakers require fundamental changes in the operation of pacemaker timing cycles to optimize detection of supraventricular tachyarrhythmias. The timing cycles related to mode switching are basically independent of the algorithm design. Blanking periods (when the sensing amplifier is temporarily disabled) should be optimized to a relatively small fraction of the pacing cycle to enhance atrial sensing and prevent far-field sensing. This review explains the function of the timing cycles pertaining to mode switching and proposes simpler terminology to facilitate the understanding of pacemaker function and electrographic interpretation of complex recordings.

Introduction: This study evaluated an atrial automatic capture verification scheme based on atrial evoked response (AER). Atrial pacing was between Atip and Can (Atip-Can) using different coupling capacitances (CCs). Independent pairs of sensing electrodes between Aring and Vtip (Aring-Vtip) or between Aring and a separate indifferent electrode (Aring-Indiff) were used to reduce pacing-induced afterpotentials., Methods and Results: A custom-made external pacing system was used to perform automatic step-up and step-down pacing (0.1 to 7.1 V at 0.5 msec, step size of 0.1 V) using different CCs (2 or 15 microF). Intracardiac signals from Aring-Indiff and Aring-Vtip were independently recorded and analyzed both in real time and off-line to detect AER. Every paced beat also was visually inspected and compared with surface ECG to verify the captures. With the intracardiac signals properly filtered, AER detection was based on the signal within a window of 12 to 65 msec after the stimulus. Data from 27 patients (4 chronic and 23 acute implantations; age 65.6+/-13.9 years) were analyzed. Bipolar atrial lead measurements using a standard pacing system analyzer were as follows (mean +/- SD): impedance 695+/-227 ohms, P wave amplitude 4.2+/-2.3 mV, slew rate 1.1+/-0.9 V/sec, and pacing threshold at 0.5 msec 1.0+/-0.5 V. The results with CC = 2 microF showed that of 9,500 atrial paced beats, correct capture verification rates were 99.8% (Aring-Indiff) and 99.4% (Aring-Vtip). Similar results were achieved with CC = 15 microF (99.7% and 99.5%, respectively)., Conclusion: AER can be reliably detected using independent pacing (Atip-Can) and sensing (Aring-Vtip or Aring-Indiff) electrodes. Therefore, atrial automatic capture verification by AER detection is feasible.

In view of the evolving indications for device therapy in atrial arrhythmia the accurate detection of high rate atrial events is a necessity. In a sheep model of atrial fibrillation (AF) we observed a contradictory behavior of the Thera DR pacemaker. The pacemakers were programmed to deliver burst pacing on detection of sinus rhythm (SR). Paradoxically, progressively more inappropriate bursts were delivered during AF, at a higher sensitivity. This implied that the pacemaker interpreted AF as SR. We assessed the atrial detection of the Thera DR, Diamond, Saphir, and Marathon pacemakers during AF, in a sheep model and in vitro using a waveform generator. By counting the annotated atrial-sensed events reported by the pacemaker we charted the behavior of the pacemakers at different sensitivities. At a higher sensitivity both the Thera DR and the Diamond paradoxically reported fewer atrial events during AF. This behavior led to inappropriate mode switching and incorrect diagnostic data collection. It could be reproduced in vitro. The Marathon did not show this paradoxical undersensing in vivo or in vitro. This paradoxical undersensing at a high sensitivity is dependent on the amplitude of the input signal and could not be explained by an overlap of programmable timing parameters. It is caused by ringing of the atrial sensing amplifier. At high atrial rates and a high sensitivity the ringing of the repetitive atrial signal input results in blanking of the atrial amplifier. This observation may be relevant in the device management of patients with paroxysmal AF.

Pacemakers are becoming increasingly sophisticated, offering a host of new diagnostic functions. This case illustrates how some of these functions can be used to help with the diagnosis and management of patients with pacemakers who suffer from cardiac arrhythmias.

At higher atrial rates, the behavior of a DDD pulse generator will depend on the atrial rate or spontaneous atrial interval (SAI) and the settings of the pacemaker: upper rate interval (URI), atrioventricular interval (AVI), and atrial refractory interval (ARI). An algorithm was developed enabling the prediction of the degree of Wenckebach block using the parameters mentioned above. In the absence of the programmed settings of the pacemaker, these parameters can be determined by noninvasive methods. AVI can be measured by application of a magnet over the pulse generator, while URI and ARI can be estimated during chest wall stimulation by progressively increasing the frequency of the external extrastimuli. The use of the formula in combination with chest wall stimulation allows the evaluation of the proper functioning of any DDD pacemaker during exercise and in patients with atrial rhythm disturbances, even when no information about the pacemaker settings is available.

Pacing and sensing are two different functions which can be accomplished by one and the same electrode. Optimal pacing requires a high tissue resistance in order to minimize the stimulation energy, making a small surface electrode highly desirable. For adequate sensing, however, the tissue resistance should be as low as possible which requires a larger electrode surface area. Decreasing the electrode surface area results in an increased polarization impedance. As this latter should be low for both pacing and sensing, an electrode with a large surface area should be used. How can these opposing needs be met by one electrode? The combination of a small geometrical surface and a large porous microstructure along with the choice of low polarizable materials meets both the requirements of pacing and sensing.

Pectoral muscle stimulation may cause serious discomfort to patients equipped with a pulse generator. Insulation defects of the lead, connector problems and defective coating of the pacemaker can are common causes of local muscle contractions. This report describes pectoral muscle stimulation caused by the atrial superfast recharge pulse incorporated into the atrial channel of a commercially available unipolar DDD pacemaker. As pectoral muscle stimulation could not be eliminated by reprogramming the pacemaker to a lower atrial output in some patients a redesign of the pacemaker is highly required.