Timing and mid-term outcomes of using leadless pacemakers as replacement for infected cardiac implantable electronic devices.

BACKGROUND: Cardiac implantable electronic device (CIED) infections have a high morbidity and mortality and are an indication of device extraction. As a replacement, leadless pacemakers (LPs) may be preferable due to a low infection risk, but mid-term data on reinfections is lacking. Moreover, early LP reimplantation in pacemaker-dependent patients would circumvent the need for temporary pacemakers. METHODS: We included all patients with LP implantation as a replacement for an infected CIED, between January 2013 and December 2021. The occurrence of reinfection was assessed during standard follow-up visits. RESULTS: Twenty-nine patients (mean age 81 ± 9 years) were included, of which 21 (73%) had a pocket infection, 7 (24%) endocarditis, and 1 (3%) a systemic infection without endocarditis. All LP implantations were successful. LPs were implanted before extraction (n = 4, 13%), simultaneously with extraction (n = 5, 17%) and after extraction (n = 20, 70%). No reinfection occurred during the follow-up of median 32 months (IQR 13-66 months). Repeat blood cultures obtained in 9 (30%) patients and transthoracic echocardiography in all 7 patients with pacemaker endocarditis were negative for reinfection. In a subset of 6 LPs extracted during follow-up due to early battery depletion, prophylactically after the battery advisory or due to non-capture (median 36 months (range 0-67 months) post-implantation), histopathologic examination of tissues around the LPs showed no signs of infection. CONCLUSIONS: After replacing infected CIEDs for an LP, no reinfections occurred in over 2.5 years follow-up. These results confirm that in case of CIED infection, the LP is an appealing replacement device. LP implantation before CIED extraction is feasible.

Tissues attached to retrieved leadless pacemakers: Histopathological evaluation of tissue composition in relation to implantation time and complications.

BACKGROUND: Leadless pacemakers (LPs) have proven safe and effective, but device revisions remain necessary. Either replacing the LP or implanting a new adjacent LP is feasible. Replacement seems more appealing, but encapsulation and tissue adhesions may hamper the safety and efficacy of LP retrieval. OBJECTIVE: We determined the incidence and cellular characteristics of tissue adherent to retrieved LPs and the potential implications for end-of-life strategy. METHODS: All 15 consecutive successful Nanostim LP retrievals in a tertiary center were included. We assessed the histopathology of adherent tissue and obtained clinical characteristics. RESULTS: Adherent tissue was present in 14 of 15 retrievals (93%; median implantation duration 36 months; range 0-96 months). The tissue consisted of fibrosis (n = 2), fibrosis and thrombus (n = 9), or thrombus only (n = 3). In short-term retrievals (<1 year), mostly fresh thrombi without fibrosis were seen. In later retrievals, the tissue consisted of fibrosis often with organizing or lytic thrombi. Fibrosis showed different stages of organization, notably early fibrocellular and later fibrosclerotic tissue. Inflammatory cells were seen (n = 4) without signs of infection. Tricuspid valve material was retrieved in 1 patient after 36 months, resulting in increased tricuspid regurgitation. CONCLUSION: Our results suggest that fibrosis and thrombus adherent to LPs are common and encapsulate the LP as seen in transvenous pacemakers. LPs may adhere to the tricuspid valve or subvalvular apparatus affecting retrieval safety. The end-of-life strategy should be optimized by incorporating risk stratification for excessive fibrotic encapsulation and adhesions.

Sex differences in patients with repaired tetralogy of Fallot support a tailored approach for males and females: a cardiac magnetic resonance study.

Purpose Substantial differences between sexes exist with respect to cardiovascular diseases, including congenital heart disease. Nevertheless, clinical decisions in the long-term follow-up of patients with repaired tetralogy of Fallot (rTOF) are currently based on unisex thresholds for cardiac magnetic resonance (CMR) measurements. This study aimed to assess whether sex differences exist in cardiac adaptation to hemodynamic loading conditions in patients with rTOF. Methods and Results This cross-sectional, two-center, combined pediatric and adult cohort included 320 rTOF patients (163 males, 51%) who underwent routine CMR. Despite similar age (median and interquartile range [m + IQR] 23.4 [15.2-34.4] years), surgical history, and hemodynamic loading, males with rTOF demonstrated higher biventricular CMR-derived volumes and masses, indexed for body surface area, compared to females (e.g. m + IQR right ventricular (RV) end-diastolic volume: males 123 [100-151] mL/m2, females 114 [94-131] mL/m2, P = 0.007). Sex-specific Z-scores of biventricular volumes and masses were similar for males and females. RV volumes and masses correlated with hemodynamic loading, but these relations did not differ between sexes. Biventricular ejection fraction (EF) appeared to be lower in male patients, compared to female patients (e.g. m + IQR RVEF: males 48 [43-54]%, females 52 [46-57]%, P < 0.001). Conclusion Indexed ventricular volumes and masses are higher in males with rTOF, compared to females, similar to the healthy population. RV hypertrophy and dilatation correlated to loading conditions similarly for both sexes. However, under comparable loading conditions, males demonstrated more severe functional impairment. These results indicate that sex-differences should no longer be ignored in treatment strategies, including timing of pulmonary valve replacement.

Leadless cardiac pacing systems: current status and future prospects.

Introduction: Permanent transvenous pacemaker therapy is an essential management option in patients with symptomatic bradyarrhythmias, but harbors a concomitant risk of serious complications. As most complications are lead- or pocket-related, intracardiac leadless pacemaker therapy has the potential to positively impact patient outcome. Since the first leadless pacemaker implant in 2012, many studies have been conducted to evaluate the effectiveness, safety, and applicability of this novel pacing approach.Areas covered: This review will cover the current status of leadless pacemaker technology. Available safety and efficacy outcomes, current area of indication, and end-of-life management will be evaluated. Furthermore, future perspectives for clinical practice and new pacing modalities are discussed.Expert opinion: The first-generation leadless pacemakers are a promising innovation that provide safe and efficient single-chamber pacing therapy without the use of transvenous pacemaker leads. Yet, broad implementation of this technology is hampered by limitations of the current leadless devices, such as end-of-life management and its single-chamber pacing indication. Further innovations such as leadless dual-chamber pacing therapy, leadless cardiac synchronization therapy, energy-harvesting leadless pacemakers, communicating leadless pacemakers with subcutaneous implantable cardiac defibrillators, and minimally invasive completely extracardiac pacemakers are currently being developed that have the potential to become major game changers in pacing therapy.

CMR feature tracking left ventricular strain-rate predicts ventricular tachyarrhythmia, but not deterioration of ventricular function in patients with repaired tetralogy of Fallot.

BACKGROUND: Myocardial strain has been shown to predict outcome in various cardiovascular diseases, including congenital heart diseases. The aim of this study was to evaluate the predictive value of cardiac magnetic resonance (CMR) feature-tracking derived strain parameters in repaired tetralogy of Fallot (rTOF) patients for developing ventricular tachycardia (VT) and deterioration of ventricular function. METHODS: Patients with rTOF who underwent CMR investigation were included. Strain and strain-rate of both ventricles were assessed using CMR feature tracking. The primary outcome was a composite of the occurrence of sustained VT or non-sustained VT requiring invasive therapy. The secondary outcome was analyzed in patients that underwent a second CMR after 1.5 to 3.5 years. Deterioration was defined as reduction (≥10%) in right ventricular (RV) ejection fraction, reduction (≥10%) in left ventricular (LV) ejection fraction or increase (≥30 mL/m2) in indexed RV end-diastolic volume compared to baseline. RESULTS: 172 patients (median age 24.3 years, 54 patients <18 years) were included. Throughout a median follow-up of 7.4 years, 9 patients (4.5%) experienced the primary endpoint of VT. Multivariate Cox-regression analysis showed that LV systolic circumferential strain-rate was independently predictive of primary outcome (p = 0.023). 70 patients underwent a serial CMR, of whom 14 patients (20%) showed ventricular deterioration. Logistic regression showed no predictive value of strain and strain-rate parameters. CONCLUSIONS: In patients with rTOF, LV systolic circumferential strain-rate is an independent predictor for the development of VT. Ventricular strain parameters did not predict deterioration of ventricular function in the studied population.

Feasibility of An Entirely Extracardiac, Minimally Invasive,Temporary Pacing System.

BACKGROUND: A completely extracardiac pacing system provides the potential for clinical advantages over existing device alternatives that require intravascular, endocardial, or epicardial contact. Preliminary studies evaluating the feasibility of cardiac pacing with a lead in the anterior mediastinum, outside the pericardium and circulatory system have been completed. These studies examined (1) the anatomic access route, (2) the usability of a delivery tool to facilitate lead placement, and (3) the pacing performance of the extracardiac lead. METHODS: Feasibility evaluations included (1) a retrospective computed tomography analysis to characterize anatomic variations related to lead access, (2) accessing the anterior mediastinum in cadavers and human subjects using a custom delivery tool, and (3) acute clinical pacing performance. RESULTS: Major findings: (1) A total of 166 (95%) out of 174 patients had a viable lead access path through the fourth, fifth, or sixth intercostal space. (2) Access to the targeted implant location using a delivery tool was successful in all 5 cadavers and 3 humans without use of fluoroscopy and with an average lead delivery time of 121±52 s. No damage to the lung, pericardium, heart, or internal thoracic vessels occurred. (3) Pacing performance was tested in 6 human subjects showing a threshold voltage of 4.7 V (2.7-6.7), threshold pulse width of 1.8 ms (1.0-2.5), and an impedance of 1205 Ω (894-1786). R-wave amplitudes measured 9.6 mV (5.6-12.0). CONCLUSIONS: Results support the feasibility for this completely extracardiac pacing method in a heterogeneous patient population, using a minimally invasive, parasternal, delivery approach and with adequate sensing and thresholds suited for temporary pacing.

Impact of Leadless Pacemaker Therapy on Cardiac and Atrioventricular Valve Function Through 12 Months of Follow-Up.

BACKGROUND: Endocardial pacemaker leads and right ventricular (RV) pacing are well-known causes of tricuspid valve, mitral valve, and cardiac dysfunction. Lead-related adverse consequences can potentially be mitigated by leadless pacemaker (LP) therapy by eliminating the presence of a transvalvular lead. This study assessed the impact of LP placement on cardiac and valvular structure and function. METHODS: Echocardiographic studies before and 12±1 months after LP implantation were performed between January 2013 and May 2018 at our center and compared with age- and sex-matched controls of dual-chamber transvenous pacemaker recipients. RESULTS: A total of 53 patients receiving an LP were included, of whom 28 were implanted with a Nanostim and 25 with a Micra LP device. Tricuspid valve regurgitation was graded as being more severe in 23 (43%) patients at 12±1 months compared with baseline ( P<0.001). Compared with an apical position, an RV septal position of the LP was associated with increased tricuspid valve incompetence (odds ratio, 5.20; P=0.03). An increase in mitral valve regurgitation was observed in 38% of patients ( P=0.006). LP implantation resulted in a reduction of RV function, according to a lower tricuspid annular plane systolic excursion ( P=0.003) and RV tricuspid lateral annular systolic velocity ( P=0.02), and a higher RV Tei index ( P=0.04). LP implantation was further associated with a reduction of left ventricular ejection fraction ( P=0.03) and elevated left ventricular Tei index ( P=0.003). The changes in tricuspid valve regurgitation in the LP group were similar to the changes in the dual-chamber transvenous pacemaker control group (43% versus 38%, respectively; P=0.39). CONCLUSIONS: LP therapy is associated with an increase in tricuspid valve dysfunction through 12 months of follow-up; yet it was comparable to dual-chamber transvenous pacemaker systems. Furthermore, LP therapy seems to adversely impact mitral valve and biventricular function.

Risk of cardiac tachyarrhythmia in patients with repaired tetralogy of Fallot: a multicenter cardiac MRI based study.

Cardiac tachyarrhythmias are the leading cause of morbidity and mortality in patients with repaired tetralogy of Fallot (TOF). We evaluated risk factors for sustained ventricular tachyarrhythmia (VT) and atrial tachyarrhythmia (ATA) in these patients. Patients (n = 319) who underwent cardiac magnetic resonance (CMR) imaging at two tertiary centers between 2007 and 2016 were assessed. Potential risk markers, based on history, cardiac magnetic resonance imaging (CMR), electrocardiography (ECG) and echocardiography, were analyzed for prediction of the primary endpoint of VT, and the secondary endpoint of ATA. During a follow-up of 3.5 (0.9-6.1) years, 20 (6.3%) patients reached the primary endpoint, and 30 (9.4%) the secondary endpoint. Multivariable cox hazards regression identified right ventricular (RV) end-diastolic volume (Hazard ratio [HR] 2.03, per 10 ml/m2 increase; p = 0.02), RV end-systolic volume (HR 3.04, per 10 ml/m2 increase; p = 0.04), RV mass (HR 1.88, per 10 g/m2 increase; p = 0.02), and RV ejection fraction (HR 6.06, per 10% decrease; p = 0.02) derived from CMR to be independent risk factors of VT. In addition, QRS-duration (HR 1.70, per 10 ms increase; p = 0.001) and body mass index (BMI: HR 1.8, per 5 kg/m2 increase; p = 0.02) were independent markers of VT. Older age at TOF repair (HR 1.33, per 2 months increase; p = 0.03) and BMI (HR 1.76, per 5 kg/m2 increase; p < 0.001) independently predicted ATA. RV systolic dysfunction, hypertrophy and dilatation on CMR, together with QRS prolongation, and obesity are predictive of VT in TOF patients. Older age at TOF repair and obesity were associated with the occurrence of ATA.

Leadless pacemaker implantation after explantation of infected conventional pacemaker systems: A viable solution?

BACKGROUND: Conventional cardiac device infections are increasing in incidence, causing significant morbidity and mortality. Leadless pacemaker (LP) therapy may provide new opportunities for the management of pacemaker (PM) infections as it does not require implantation of transvenous leads and a pectoral pocket. OBJECTIVE: We sought to evaluate the effect of early and late LP implantation in patients diagnosed with device infection. METHODS: Patients receiving an LP at our center after conventional PM lead extraction due to infection between December 1, 2013 and November 30, 2017 were included. RESULTS: A total of 17 patients (mean age 77.4 ± 7.77 years) underwent LP implantation (ie, 11 with Nanostim leadless cardiac pacemaker [Abbott, Chicago, IL] and 6 with Micra transcatheter pacing system [Medtronic, Minneapolis, MN]) after successful PM system explantation. In 9 PM-dependent patients, a temporary transvenous pacing system was placed as a bridge to permanent LP implantation. Early LP implantation was performed in 6 patients (<1 week), and in the remaining patients, the LP was placed at a later stage (>1 week). All patients experienced no LP infection during a mean follow-up of 16 ± 12 months, including 7 patients with a history of recurrent device infections with a mean follow-up of 20 ± 14 months. CONCLUSION: Early and late LP placement after infected conventional pacing system explantation was a viable option in our case series. This therapy may provide an alternative strategy in the management of device infection, if confirmed by subsequent prospective randomized trials, particularly for patients who are PM dependent or have a history of recurrent device infections.

Health-related quality of life impact of a transcatheter pacing system.

BACKGROUND: Transcatheter pacing systems (TPS) provide a novel, minimally invasive approach in which a miniaturized, leadless pacemaker (PM) is transfemorally implanted in the right ventricle. We evaluated the health-related quality of life (HRQoL) impact, patient satisfaction, and activity restrictions following TPS in a large prospective multicenter clinical trial. METHODS AND RESULTS: Patients who underwent a Micra TPS implantation between December 2013 and May 2015 were included. HRQoL impact was evaluated using the Short-Form-36 (SF-36) questionnaire at baseline, 3, and 12 months. Patient satisfaction was assessed using a three-item questionnaire determining recovery, activity level, and esthetic appearance at 3 months. Implanting physicians compared the patient activity restrictions for TPS to traditional PM therapy. A total of 720 patients were implanted with a TPS (76 ± 11 years; 59% male). Of these patients, 702 (98%), 681 (95%), and 635 (88%) completed the SF-36 at baseline, 3 and 12 months, respectively. Improvements were observed at 3 and 12 months in all SF-36 domains and all attained statistical significance. Of 693 patients who completed the patient satisfaction questionnaire, 96%, 91%, 74% were (very) satisfied with their esthetic appearance, recovery, and level of activity, respectively. TPS discharge instructions were rated less restrictive in 49%, equally restrictive in 47%, and more restrictive in 4% of cases compared with traditional PM systems. CONCLUSIONS: TPS resulted in postimplant HRQoL improvements at 3 and 12 months, and high levels of patient satisfaction at 3 months. Further, TPS was associated with less activity restrictions compared with traditional PM systems.

The learning curve associated with the implantation of the Nanostim leadless pacemaker.

PURPOSE: Use of novel medical technologies, such as leadless pacemaker (LP) therapy, may be subjected to a learning curve effect. The objective of the current study was to assess the impact of operators' experience on the occurrence of serious adverse device effects (SADE) and procedural efficiency. METHODS: Patients implanted with a Nanostim LP (Abbott, USA) within two prospective studies (i.e., LEADLESS ll IDE and Leadless Observational Study) were assessed. Patients were categorized into quartiles based on operator experience. Learning curve analysis included the comparison of SADE rates at 30 days post-implant per quartile and between patients in quartile 4 (> 10 implants) and patients in quartiles 1 through 3 (1-10 implants). Procedural efficiency was assessed based on procedure duration and repositioning attempts. RESULTS: Nanostim LP implant was performed in 1439 patients by 171 implanters at 60 centers in 10 countries. A total of 91 (6.4%) patients experienced a SADE in the first 30 days. SADE rates dropped from 7.4 to 4.5% (p = 0.038) after more than 10 implants per operator. Total procedure duration decreased from 30.9 ± 19.1 min in quartile 1 to 21.6 ± 13.2 min (p < 0.001) in quartile 4. The need for multiple repositionings during the LP procedure reduced in quartile 4 (14.8%), compared to quartiles 1 (26.8%; p < 0.001), 2 (26.6%; p < 0.001), and 3 (20.4%; p = 0.03). CONCLUSIONS: Learning curves exist for Nanostim LP implantation. Procedure efficiency improved with increased operator experience, according to a decrease in the incidence of SADE, procedure duration, and repositioning attempts.

Diagnostic value of Doppler echocardiography for identifying hemodynamic significant pulmonary valve regurgitation in tetralogy of Fallot: comparison with cardiac MRI.

Quantification of pulmonary regurgitation (PR) is essential in the management of patients with repaired tetralogy of Fallot (TOF). We sought to evaluate the accuracy of first-line Doppler echocardiography in comparison with cardiac magnetic resonance imaging (MRI) to identify hemodynamic significant PR. Paired cardiac MRI and echocardiographic studies (n = 97) in patients with repaired TOF were retrospectively analyzed. Pressure half time (PHT) and pulmonary regurgitation index (PRi) were measured using continuous wave Doppler. The ratio of the color flow Doppler regurgitation jet width to pulmonary valve (PV) annulus (jet/annulus ratio) and diastolic to systolic time velocity integral (DSTVI; pulsed wave Doppler) were assessed. Accuracy of echocardiographic measurements was tested to identify significant PR as determined by phase-contrast MRI (PR fraction [PRF] ≥ 20%). Mean PRF was 29.4 ± 15.7%. PHT < 100 ms had a sensitivity of 93%, specificity 75%, positive predictive value (PPV) 92% and negative predictive value (NPV) 78% for identifying significant PR (C-statistic 0.82). PRi < 0.77 had sensitivity and specificity of 66% and 54%, respectively (C-statistic 0.63). Jet/annulus ratio ≥1/3 had sensitivity 96%, specificity 75%, PPV 92% and NPV 82% (C-statistic 0.87). DSTVI had sensitivity 84%, specificity 33%, PPV 84% and NPV 40%, (C-statistic 0.56). Combined jet/annulus ratio ≥1/3 and PHT < 100 ms was highly accurate in identifying PRF ≥ 20%, with sensitivity 97% and specificity 100%. PHT and jet/annulus ratio on Doppler echocardiography, especially when combined, are highly accurate in identifying significant PR and therefore seem useful in the follow-up of patients with repaired TOF.