Editorial: Developments in cardiac implantable electronic device therapy: how can we improve clinical implementation?

CIED, cardiac implantable electronic devices; CRT, cardiac resynchronization therapy; CRT-D, cardiac resynchronization therapy defibrillator; EA, electroanatomical; ICD, implantable cardioverter defibrillator; LBB, left bundle branch; LBBAP, left bundle branch area pacing; LV, left ventricular; LVEF, left ventricular ejection fraction; NT-proBNP, N-terminal pro-B-type natriuretic peptide; MRI, cardiac magnetic resonance imaging; S-ICD, subcutaneous defibrillator.

Association between electrical and mechanical remodeling after cardiac resynchronization therapy: systematic review and meta-analysis of observational studies.

Cardiac resynchronization therapy (CRT) may improve not only impaired left ventricular contractility but can also induce reverse remodeling of native conduction system. Measurement of intrinsic QRS complex width during follow-up is the simplest method to assess reverse electrical remodeling (RER). We aimed to provide a literature review and meta-analysis on incidence and impact of RER and its association with mechanical remodeling. A systematic review and random-effect meta-analysis of studies reporting data on RER was performed. A total of 16 studies were included in this meta-analysis with 930 patients undergoing CRT (mean age 64.0 years, 64.1% males). The weighted mean incidence of RER was 42%. Reverse mechanical remodeling assessed by echocardiography was more frequently observed in patients with RER compared to patients without RER (75.7% vs. 46.6%; odds ratio [OR] 3.7, 95% confidence interval [CI] 2.24-6.09, p < 0.01). Mechanical responders had a mean iQRS shortening of 7.7 ms, while mechanical non-responders experienced a mean widening of iQRS by 5.2 ms (p < 0.01). Clinical improvement was more frequent in patients with RER vs. patients without RER (82.9% vs. 49.0%; OR 5.26; 95% CI 2.92-9.48; p < 0.01). No significant difference in all-cause mortality between patients with and without RER was found. Mean difference between baseline intrinsic QRS and post-implantation paced QRS was significant in patients with later RER (21.2 ms, 95% CI 9.4-32.9, p < 0.01), but not in patients without RER (6.6 ms, 95% CI -2.2-15.4, p = 0.14). Gender, initial left bundle block morphology and heart failure etiology were found not to be predictive for RER. Our meta-analysis demonstrates that shortening of iQRS duration is a common finding during follow-up of patients undergoing CRT and is associated with mechanical reverse remodeling and clinical improvement. Clinical Trial Registration: Prospero Database-CRD42021253336.

Novel two-lead cardiac resynchronization therapy system provides equivalent CRT responses with less complications than a conventional three-lead system: Results from the QP ExCELs lead registry.

INTRODUCTION: The novel two-lead cardiac resynchronization therapy (CRT)-DX system utilizes a floating atrial dipole on the implantable cardioverter-defibrillator lead, and when implanted with a left ventricular (LV) lead, offers a two-lead CRT system with AV synchrony. This study compared complication rates and CRT response among subjects implanted with a two-lead CRT-DX system to those subjects implanted with a standard three-lead CRT-D system. METHODS AND RESULTS: A total of 240 subjects from the Sentus QP-Extended CRT Evaluation with Quadripolar Left Ventricular Leads postapproval study were selected to identify 120 matched pairs based on similar demographic characteristics using a Greedy algorithm. The complication-free rate was evaluated as the primary endpoint. All-cause mortality, heart failure hospitalizations, device diagnostic data, New York Heart Association (NYHA) class improvement, and defibrillator therapy were evaluated from clinical data, in-office interrogations, and remote monitoring throughout the follow-up period. Complication-free survival favored the CRT-DX group with 92.5% without a major complication compared to 85.0% in the CRT-D cohort (P = .0495; 95% confidence interval: 0.1%-14.9%) over a mean follow-up of 1.3 and 1.4 years, respectively. Incidence of all-cause mortality, heart failure hospitalizations, NYHA changes at 6 months postimplant, and percent of LV pacing during CRT therapy were similar in both device cohorts. Inappropriate shocks were more frequent in the CRT-D cohort with 5.8% of subjects receiving an inappropriate shock vs 0.8% in the CRT-DX cohort. CONCLUSION: The results of this subanalysis demonstrate that the CRT-DX system can provide similar CRT responses and significantly fewer complications when compared to a similar cohort with a conventional three-lead CRT-D system.

Implantation of the Micra transcatheter pacing system: Single Polish center experience with the real costs of hospitalization analysis.

BACKGROUND: The Micra transcatheter pacing system (TPS) is a miniaturized, single-chamber pacemaker system. Study reported herein is an initial experience with implantation of the Micra TPS. METHODS: The leadless pacemaker was implanted in 10 patients with standard indications for a permanent pacemaker implantation. All hospitalization costs were calculated for all patients. RESULTS: The mean age of the patients was 75 ± 7.1 years, 6 were men and 4 were women. Four patients had permanent atrial fibrillation as the basal rhythm and 6 patients had sinus rhythm. All patients had at least one relative contraindication that precluded the use of a traditional pacing system. Mean intraoperative ventricular sensing amplitude was 10.6 ± 5.4 mV, impedance 843 ± 185 ohms, and pacing threshold at 0.24 ms was 0.56 ± 0.23 V. At discharge, those values were 13.9 ± 5.6 mV, 667 ± 119 ohms and 0.47 ± 0.17, respectively. The mean duration of implantation procedure was 82 min, while mean fluoroscopy time was 3.5 min. Two patients developed hematoma at the groin puncture site post-implantation. In 1 case there was a need for erythrocyte mass transfusion and surgical intervention. Mean total time of hospitalization was 26 days and time from procedure to discharge 12 days. Average cost of hospitalization per 1 patient was 11,260.15 EUR minimal cost was 9,052.68 EUR, while maximal cost was 16,533.18 EUR. CONCLUSIONS: Implantation of leadless pacemakers is feasible, safe and provides advantages over the conventional system. Hospitalization costs vary for individual patients in wide range.

Patient selection, pacing indications, and subsequent outcomes with de novo leadless single-chamber VVI pacing.

AIMS: Patient selection is a key component of securing optimal patient outcomes with leadless pacing. We sought to describe and compare patient characteristics and outcomes of Micra patients with and without a primary pacing indication associated with atrial fibrillation (AF) in the Micra IDE trial. METHODS AND RESULTS: The primary outcome (risk of cardiac failure, pacemaker syndrome, or syncope related to the Micra system or procedure) was compared between successfully implanted patients from the Micra IDE trial with a primary pacing indication associated with AF or history of AF (AF group) and those without (non-AF group). Among 720 patients successfully implanted with Micra, 228 (31.7%) were in the non-AF group. Reasons for selecting VVI pacing in non-AF patients included an expectation for infrequent pacing (66.2%) and advanced age (27.2%). More patients in the non-AF group had a condition that precluded the use of a transvenous pacemaker (9.6% vs. 4.7%, P = 0.013). Atrial fibrillation patients programmed to VVI received significantly more ventricular pacing compared to non-AF patients (median 67.8% vs. 12.6%; P < 0.001). The overall occurrence of the composite outcome at 24 months was 1.8% with no difference between the AF and non-AF groups (hazard ratio 1.36, 95% confidence interval 0.45-4.2; P = 0.59). CONCLUSION: Nearly one-third of patients selected to receive Micra VVI therapy were for indications not associated with AF. Non-AF VVI patients required less frequent pacing compared to patients with AF. Risks associated with VVI therapy were low and did not differ in those with and without AF.

Effects of implantation of quadripolar left ventricular leads on CRT response.

BACKGROUND: The use of quadripolar (QP) left ventricular leads for cardiac resynchronization therapy (CRT) is intended to improve outcomes compared with conventional bipolar leads (BP). Hence, the number of implanted quadripolar CRT systems is increasing despite limited long-term data. PURPOSE: The aim of this study is to evaluate clinical response and long-term outcomes of CRT recipients who were implanted with quadripolar versus bipolar left ventricular leads. METHODS: Data from consecutive patients receiving a CRT defibrillator in one German and one Hungarian tertiary referral center were retrospectively collected. Long-term survival and response to CRT were analyzed. RESULTS: A total of 536 patients with structural heart disease and a mean left ventricular ejection fraction (LVEF) of 25% received a CRT defibrillator (CRT-D) system for primary (79%) or secondary (21%) prevention of sudden death. Comorbidities did not differ significantly between patients receiving a QP (n = 123) or a BP lead (n = 413). Procedure (101 vs. 120 min) and fluoroscopy times (14 vs. 20 min) were shorter in patients implanted with QP compared with BP (both p < 0.001). At 6 months follow-up, QP patients were more likely to respond to CRT measured as improvement in the New York Heart Association (NYHA) functional class (77% vs. 63%; p < 0.001). Use of QP left ventricle/left ventricular (LV) leads was associated with greater reduction in QRS duration compared with patients implanted with BP LV leads (- 21 ± 30 vs. - 8 ± 35 ms, p = 0.004). Mortality was not significantly different between patients with QP and patients with BP LV leads at a mean follow-up of 39 ± 31 months. CONCLUSION: Implantation of quadripolar left ventricular leads was associated with better CRT response compared with bipolar left ventricular leads.

Leadless Pacemaker Implantation in Hemodialysis Patients: Experience With the Micra Transcatheter Pacemaker.

OBJECTIVES: This study sought to report periprocedural outcomes and intermediate-term follow-up of hemodialysis patients undergoing Micra implantation. BACKGROUND: Leadless pacemakers may be preferred in patients with limited vascular access and high-infection risk, such as patients on hemodialysis. METHODS: Patients on hemodialysis at the time of Micra implantation attempt (n = 201 of 2,819; 7%) from the Micra Transcatheter Pacing Study investigational device exemption trial, Micra Transcatheter Pacing System Continued Access Study Protocol, and Micra Transcatheter Pacing System Post-Approval Registry were included in the analysis. Baseline characteristics, periprocedural outcomes, and intermediate-term follow-up were summarized. RESULTS: Patients on hemodialysis at the time of Micra implantation attempt were on average 70.5 ± 13.5 years of age and 59.2% were male. The dialysis patients commonly had hypertension (80%), diabetes (61%), coronary artery disease (39%), and congestive heart failure (27%), and 72% had a condition that the implanting physician felt precluded the use of a transvenous pacemaker. Micra was successfully implanted in 197 patients (98.0%). Reasons for unsuccessful implantation included inadequate thresholds (n = 2) and pericardial effusion (n = 2). The median implantation time was 27 min (interquartile range: 20 to 39 min). There were 3 procedure-related deaths: 1 due to metabolic acidosis following a prolonged procedure duration in a patient undergoing concomitant atrioventricular nodal ablation and 2 deaths occurred in patients who needed surgical repair after perforation. Average follow-up was 6.2 months (range 0 to 26.7 months). No patients had a device-related infection or required device removal because of bacteremia. CONCLUSIONS: Leadless pacemakers represent an effective pacing option in this challenging patient population on chronic hemodialysis. The risk of infection appears low with an acceptable safety profile. (Micra Transcatheter Pacing Study; NCT02004873; Micra Transcatheter Pacing System Continued Access Study Protocol; NCT02488681; Micra Transcatheter Pacing System Post-Approval Registry; NCT02536118).

Risk of cardiac arrhythmias after electrical accident: a single-center study of 480 patients.

OBJECTIVE: Patients with electrical injury are considered to be at high risk of cardiac arrhythmias. Due to the small number of studies, there is no widely accepted guideline regarding the risk assessment and management of arrhythmic complications after electrical accident (EA). Our retrospective observational study was designed to determine the prevalence of ECG abnormalities and cardiac arrhythmias after EA, to evaluate the predictive value of cardiac biomarkers for this condition and to assess in-hospital and 30-day mortality. METHODS: Consecutive patients presenting after EA at the emergency department of our institution between 2011 and 2016 were involved in the current analysis. ECG abnormalities and arrhythmias were analyzed at admission and during ECG monitoring. Levels of cardiac troponin I, CK and CK-MB were also collected. In-hospital and 30-day mortality data were obtained from hospital records and from the national insurance database. RESULTS: Of the 480 patients included, 184 (38.3%) had suffered a workplace accident. The majority of patients (96.2%) had incurred a low-voltage injury (< 1000 V). One hundred and four (21.7%) patients had a transthoracic electrical injury while 13 (2.7%) patients reported loss of consciousness. The most frequent ECG disorders at admission were sinus bradycardia (< 60 bpm, n = 50, 10.4%) and sinus tachycardia (> 100 bpm, n = 21, 4.4%). Other detected arrhythmias were as follows: newly diagnosed atrial fibrillation (n = 1); frequent multifocal atrial premature complexes (n = 1); sinus arrest with atrial escape rhythm (n = 2); ventricular fibrillation terminated out of hospital (n = 1); ventricular bigeminy (n = 1); and repetitive nonsustained ventricular tachycardia (n = 1). ECG monitoring was performed in 182 (37.9%) patients for 12.7 ± 7.1 h at the ED. Except for one case with regular supraventricular tachycardia terminated via vagal maneuver and one other case with paroxysmal atrial fibrillation, no clinically relevant arrhythmias were detected during the ECG monitoring. Cardiac troponin I was measured in 354 (73.8%) cases at 4.6 ± 4.3 h after the EA and was significantly elevated only in one resuscitated patient. CK elevation was frequent, but CK-MB was under 5% in all patients. Both in-hospital and 30-day mortality were 0%. CONCLUSIONS: Most of cardiac arrhythmias in patients presenting after EA can be diagnosed by an ECG on admission, thus routine ECG monitoring appears to be unnecessary. In our patient cohort cardiac troponin I and CK-MB were not useful in risk assessment after EA. Late-onset malignant arrhythmias were not observed.

Accelerometer-based atrioventricular synchronous pacing with a ventricular leadless pacemaker: Results from the Micra atrioventricular feasibility studies.

BACKGROUND: Micra is a leadless pacemaker that is implanted in the right ventricle and provides rate response via a 3-axis accelerometer (ACC). Custom software was developed to detect atrial contraction using the ACC enabling atrioventricular (AV) synchronous pacing. OBJECTIVE: The purpose of this study was to sense atrial contractions from the Micra ACC signal and provide AV synchronous pacing. METHODS: The Micra Accelerometer Sensor Sub-Study (MASS) and MASS2 early feasibility studies showed intracardiac accelerations related to atrial contraction can be measured via ACC in the Micra leadless pacemaker. The Micra Atrial TRacking Using A Ventricular AccELerometer (MARVEL) study was a prospective multicenter study designed to characterize the closed-loop performance of an AV synchronous algorithm downloaded into previously implanted Micra devices. Atrioventricular synchrony (AVS) was measured during 30 minutes of rest and during VVI pacing. AVS was defined as a P wave visible on surface ECG followed by a ventricular event <300 ms. RESULTS: A total of 64 patients completed the MARVEL study procedure at 12 centers in 9 countries. Patients were implanted with a Micra for a median of 6.0 months (range 0-41.4). High-degree AV block was present in 33 patients, whereas 31 had predominantly intrinsic conduction during the study. Average AVS during AV algorithm pacing was 87.0% (95% confidence interval 81.8%-90.9%), 80.0% in high-degree block patients and 94.4% in patients with intrinsic conduction. AVS was significantly greater (P <.001) during AV algorithm pacing compared to VVI in high-degree block patients, whereas AVS was maintained in patients with intrinsic conduction. CONCLUSION: Accelerometer-based atrial sensing is feasible and significantly improves AVS in patients with AV block and a single-chamber leadless pacemaker implanted in the right ventricle.

ICD lead type and RV lead position in CRT-D recipients.

BACKGROUND: Data on preferred ICD lead type and optimal RV lead position in patients undergoing CRT-D implantation are limited. OBJECTIVES: To compare dual- versus single-coil ICD leads and non-apical versus apical RV lead position and their impact on clinical parameters and survival in CRT-D recipients. METHODS: A total of 563 consecutive patients with advanced heart failure and indication for CRT-D implantation were enrolled in two European tertiary centers. Endpoints were improvement in NYHA functional class, changes in echo- and electrocardiographic parameters, and all-cause and cardiovascular mortality. RESULTS: In this retrospective analysis, a total of 313 (56%) dual- and 250 (44%) single-coil ICD leads were used. RV leads were placed non-apically in 262 (47%) and apically in 296 (53%) patients, respectively. Over a mean follow-up of 41 ± 34 months, all-cause mortality and cardiovascular mortality were similar for patients with dual- versus single-coil ICD lead (adjusted HR 0.81, 95% CI 0.58-1.12 and aHR 1.22, 95% CI 0.73-2.04) and non-apical versus apical RV lead position (aHR 0.98, 95% CI 0.71-1.36 and aHR 0.76, 95% CI 0.44-1.31). Non-apical RV lead position was associated with greater reduction in QRS duration after CRT implantation (- 14.4 ± 32.1 vs. - 4.3 ± 34.3 ms, p < 0.001). CONCLUSIONS: We found no association between ICD lead type or RV lead position and outcomes in CRT-D recipients. Non-apical RV lead position was associated with larger reduction in QRS duration.

Refined heart failure detection algorithm for improved clinical reliability of OptiVol alerts in CRT-D recipients.

BACKGROUND: The reliability of intrathoracic impedance monitoring for prediction of heart failure (HF) by implantable cardiac devices is controversial. Despite using additional device-based parameters described in the PARTNERS HF study, such as new onset of arrhythmias, abnormal autonomics, low biventricular pacing rate or patient activity level, the predictive power of device diagnostic algorithm is still in doubt. The objective of this study was to compare the device diagnostic algorithm described in the PARTNERS HF study to a newly developed algorithm applying refined diagnostic criteria. METHODS: Fourty two patients were prospectively enrolled who had been implanted with an intrathoracic impedance and remote monitoring capable implantable cardiac defibrillator with a cardiac resychroniza-tion therapy (CRT-D) device in this observational study. If a remote OptiVolTM alert occurred, patients were checked for presence of HF symptoms. A new algorithm was derived from the original PARTNERS HF criteria, considering more sensitive cut-offs and changes of patterns of the device-based parameters. RESULTS: During an average follow-up of 38 months, 722 remote transmissions were received. From the total of 128 transmissions with OptiVol alerts, 32 (25%) corresponded to true HF events. Upon multivariate discriminant analysis, low patient activity, high nocturnal heart rate, and low CRT pacing (< 90%) proved to be independent predictors of true HF events (all p < 0.01). Incorporating these three refined criteria in a new algorithm, the diagnostic yield of OptiVol was improved by increasing specific-ity from 37.5% to 86.5%, positive predictive value from 34.1% to 69.8% and area under the curve from 0.787 to 0.922 (p < 0.01), without a relevant loss in sensitivity (96.9% vs. 93.8%). CONCLUSIONS: A refined device diagnostic algorithm based on the parameters of low activity level, high nocturnal heart rate, and suboptimal biventricular pacing might improve the clinical reliability of OptiVol alerts.

Ventricular rate stabilization for treatment of recurrent VT.

A patient with ischaemic cardiomyopathy received a secondary prevention VVI implantable cardioverter-defibrillator (ICD) after an episode of sustained ventricular tachycardia (VT). Because of recurrent VTs transmitted via CareLink, medical therapy was optimized and VT ablation was performed. Subsequently, a fast VT with a typical short-long-short initiation developed. In addition, there was an increasing need for ventricular pacing due to sinus bradycardia. This new type of VT could be successfully dealt with by upgrading to DDD ICD and activating the Ventricular Rate Stabilization algorithm.

Impact of operator experience and training strategy on procedural outcomes with leadless pacing: Insights from the Micra Transcatheter Pacing Study.

BACKGROUND: Leadless pacemaker systems have been designed to avoid the need for a pocket and transvenous lead. However, delivery of this therapy requires a new catheter-based procedure. This study evaluates the role of operator experience and different training strategies on procedural outcomes. METHODS: A total of 726 patients underwent implant attempt with the Micra transcatheter pacing system (TPS; Medtronic, Minneapolis, MN, USA) by 94 operators trained in a teaching laboratory using a simulator, cadaver, and large animal models (lab training) or locally at the hospital with simulator/demo model and proctorship (hospital training). Procedure success, procedure duration, fluoroscopy time, and safety outcomes were compared between training methods and experience (implant case number). RESULTS: The Micra TPS procedure was successful in 99.2% of attempts and did not differ between the 55 operators trained in the lab setting and the 39 operators trained locally at the hospital (P = 0.189). Implant case number was also not a determinant of procedural success (P = 0.456). Each operator performed between one and 55 procedures. Procedure time and fluoroscopy duration decreased by 2.0% (P = 0.002) and 3.2% (P < 0.001) compared to the previous case. Major complication rate and pericardial effusion rate were not associated with case number (P = 0.755 and P = 0.620, respectively). There were no differences in the safety outcomes by training method. CONCLUSIONS: Among a large group of operators, implantation success was high regardless of experience. While procedure duration and fluoroscopy times decreased with implant number, complications were low and not associated with case number. Procedure and safety outcomes were similar between distinct training methodologies.

Rationale and design of the BUDAPEST-CRT Upgrade Study: a prospective, randomized, multicentre clinical trial.

AIMS: There is lack of conclusive evidence from randomized clinical trials on the efficacy and safety of upgrade to cardiac resynchronization therapy (CRT) in patients with implanted pacemakers (PM) or defibrillators (ICD) with reduced left ventricular ejection fraction (LVEF) and chronic heart failure (HF). The BUDAPEST-CRT Upgrade Study was designed to compare the efficacy and safety of CRT upgrade from conventional PM or ICD therapy in patients with intermittent or permanent right ventricular (RV) septal/apical pacing, reduced LVEF, and symptomatic HF. METHODS AND RESULTS: The BUDAPEST-CRT study is a prospective, randomized, multicentre, investigator-sponsored clinical trial. A total of 360 subjects will be enrolled with LVEF ≤ 35%, NYHA functional classes II-IVa, paced QRS ≥ 150 ms, and a RV pacing ≥ 20%. Patients will be followed for 12 months. Randomization is performed in a 3:2 ratio (CRT-D vs. ICD). The primary composite endpoint is all-cause mortality, a first HF event, or less than 15% reduction in left ventricular (LV) end-systolic volume at 12 months. Secondary endpoints are all-cause mortality, all-cause mortality or HF event, and LV volume reduction at 12 months. Tertiary endpoints include changes in quality of life, NYHA functional class, 6 min walk test, natriuretic peptides, and safety outcomes. CONCLUSION: The results of our prospective, randomized, multicentre clinical trial will provide important information on the role of cardiac resynchronization therapy with defibrillator (CRT-D) upgrade in patients with symptomatic HF, reduced LVEF, and wide-paced QRS with intermittent or permanent RV pacing. CLINICAL TRIALS.GOV IDENTIFIER: NCT02270840.

Long-term performance of a transcatheter pacing system: 12-Month results from the Micra Transcatheter Pacing Study.

BACKGROUND: Early performance of the Micra transcatheter pacemaker from the global clinical trial reported a 99.2% implant success rate, low and stable pacing capture thresholds, and a low (4.0%) rate of major complications up to 6 months. OBJECTIVE: The purpose of this report was to describe the prespecified long-term safety objective of Micra at 12 months and electrical performance through 24 months. METHODS: The Micra Transcatheter Pacing Study was a prospective single-arm study designed to assess the safety and efficacy of the Micra VVIR leadless/intracardiac pacemaker. Enrolled patients met class I or II guideline recommendations for de novo ventricular pacing. The long-term safety objective was freedom from a system- or procedure-related major complication at 12 months. A predefined historical control group of 2667 patients with transvenous pacemakers was used to compare major complication rates. RESULTS: The long-term safety objective was achieved with a freedom from major complication rate of 96.0% at 12 months (95% confidence interval 94.2%-97.2%; P < .0001 vs performance goal). The risk of major complications for patients with Micra (N = 726) was 48% lower than that for patients with transvenous systems through 12 months postimplant (hazard ratio 0.52; 95% confidence interval 0.35-0.77; P = .001). Across subgroups of age, sex, and comorbidities, Micra reduced the risk of major complications compared to transvenous systems. Electrical performance was excellent through 24 months, with a projected battery longevity of 12.1 years. CONCLUSION: Long-term performance of the Micra transcatheter pacemaker remains consistent with previously reported data. Few patients experienced major complications through 12 months of follow-up, and all patient subgroups benefited as compared to transvenous pacemaker historical control group.

Effects of Upgrade Versus De Novo Cardiac Resynchronization Therapy on Clinical Response and Long-Term Survival: Results from a Multicenter Study.

BACKGROUND: Benefits of cardiac resynchronization therapy (CRT) on morbidity and mortality in selected patients are well known. Although the number of upgrade procedures from single- or dual-chamber devices to CRT is increasing, there are only sparse data on the outcomes of upgrade procedures compared with de novo CRT. This study aimed to evaluate clinical response and survival in patients receiving de novo versus upgrade CRT defibrillator therapy. METHODS AND RESULTS: Prospectively collected outcome data were compared in patients undergoing de novo or upgrade CRT defibrillator implantation at 3 implant centers in Germany and Hungary. Clinical response was defined as an improvement by at least one New York Heart Association (NYHA) functional class. CRT implantation was performed in 552 consecutive patients of whom 375 underwent a de novo and 177 an upgrade procedure. Upgrade patients were more often implanted for secondary prevention, suffered more often from atrial fibrillation, chronic kidney disease, diabetes mellitus, and dyslipidemia, and had more often a non-LBBB (left bundle branch block) wide QRS complex, and lower left ventricular ejection fraction. Upgrade procedures were associated with a lower response rate compared to the de novo group (57% versus 69%, P univariate=0.008, P multivariate=0.021). During the follow-up of 37±28 months, survival was worse after upgrade compared with de novo CRT defibrillator implantations (hazard ratio, 1.65; 95% confidence interval, 1.22-2.24; P=0.001) even after careful adjustment for important baseline variables (adjusted hazard ratio, 1.68; 95% confidence interval, 1.20-2.34; P=0.002) and after propensity-score matching (propensity-adjusted hazard ratio, 1.79; 95% confidence interval, 1.08-2.95; P=0.023). CONCLUSIONS: Both clinical response and long-term survival were less favorable in patients undergoing CRT upgrade compared to de novo implantations.

Long-term outcomes in leadless Micra transcatheter pacemakers with elevated thresholds at implantation: Results from the Micra Transcatheter Pacing System Global Clinical Trial.

BACKGROUND: Device repositioning during Micra leadless pacemaker implantation may be required to achieve optimal pacing thresholds. OBJECTIVE: The purpose of this study was to describe the natural history of acute elevated Micra vs traditional transvenous lead thresholds. METHODS: Micra study VVI patients with threshold data (at 0.24 ms) at implant (n = 711) were compared with Capture study patients with de novo transvenous leads at 0.4 ms (n = 538). In both cohorts, high thresholds were defined as >1.0 V and very high as >1.5 V. Change in pacing threshold (0-6 months) with high (1.0 to ≤1.5 V) or very high (>1.5 V) thresholds were compared using the Wilcoxon signed-rank test. RESULTS: Of the 711 Micra patients, 83 (11.7%) had an implant threshold of >1.0 V at 0.24 ms. Of the 538 Capture patients, 50 (9.3%) had an implant threshold of >1.0 V at 0.40 ms. There were no significant differences in patient characteristics between those with and without an implant threshold of >1.0 V, with the exception of left ventricular ejection fraction in the Capture cohort (high vs low thresholds, 53% vs 58%; P = .011). Patients with an implant threshold of >1.0 V decreased significantly (P < .001) in both cohorts. Micra patients with high and very high thresholds decreased significantly (P < .01) by 1 month, with 87% and 85% having 6-month thresholds lower than the implant value. However, when the capture threshold at implant was >2 V, only 18.2% had a threshold of ≤1 V at 6 months and 45.5% had a capture threshold of >2 V. CONCLUSIONS: Pacing thresholds in most Micra patients with elevated thresholds decrease after implant. Micra device repositioning may not be necessary if the pacing threshold is ≤2 V.

Incidence of Cardiac Perforation With Conventional and With Leadless Pacemaker Systems: A Systematic Review and Meta-Analysis.

INTRODUCTION: Two leadless pacemaker (PM) systems were recently developed to avoid pocket- and lead-related complications. As leadless PMs are implanted with a large delivery catheter, cardiac perforation remains a major safety concern. We aimed to provide a literature review on incidence of cardiac perforation with conventional and with leadless PM systems. METHODS AND RESULTS: A systematic review over the last 25 years for studies reporting data on PM lead perforation was performed. Findings were synthesized descriptively. Where control groups were available, data were meta-analyzed to identify important clinical risk factors. A total of 28 studies comprising 60,744 patients undergoing conventional PM implantation were analyzed. The incidence of lead perforation ranged from 0% to 6.37% (mean 0.82%, weighted mean 0.31%, median of 0.40%). There was no significant difference in perforation risk between atrial and ventricular electrodes (POR 0.72, 95% confidence interval [CI], 0.28-1.87, P = 0.50) and between MRI conditional and conventional leads (POR 5.93, 95% CI, 0.72-48.76, P = 0.10). The use of active fixation leads (POR 4.25, 95% CI, 1.00-17.95, P = 0.05) and utilization of DDD versus VVI PM systems (POR 3.50, 95% CI, 1.48-8.28, P < 0.01) were associated with higher rates of perforation. In the 2 leadless PM studies, the incidence of cardiac perforation was 1.52% for each. CONCLUSION: PM lead perforation rates vary in individual studies with an overall low incidence. Leadless PMs seem to be associated with a slightly higher perforation risk, most likely reflecting a learning curve effect of this novel technology.

Rate adaptive pacing in an intracardiac pacemaker.

BACKGROUND: The Micra transcatheter pacemaker was designed to have similar functionality to conventional transvenous VVIR pacing systems. It provides rate adaptive pacing using a programmable 3-axis accelerometer designed to detect patient activity in the presence of cardiac motion. OBJECTIVE: The purpose of this study was to evaluate the system's performance during treadmill tests to maximum exertion in a subset of patients within the Micra Transcatheter Pacing Study. METHODS: Patients underwent treadmill testing at 3 or 6 months postimplant with algorithm programming at physician discretion. Normalized sensor rate (SenR) relative to the programmed upper sensor rate was modeled as a function of normalized workload in metabolic equivalents (METS) relative to maximum METS achieved during the test. A normalized METS and SenR were determined at the end of each 1-minute treadmill stage. The proportionality of SenR to workload was evaluated by comparing the slope from this relationship to the prospectively defined tolerance margin (0.65-1.35). RESULTS: A total of 69 treadmill tests were attempted by 42 patients at 3 and 6 months postimplant. Thirty tests from 20 patients who completed ≥4 stages with an average slope of 0.86 (90% confidence interval 0.77-0.96) confirmed proportionality to workload. On an individual test basis, 25 of 30 point estimates (83.3%) had a normalized slope within the defined tolerance range (range 0.46-1.08). CONCLUSION: Accelerometer-based rate adaptive pacing was proportional to workload, thus confirming rate adaptive pacing commensurate to workload is achievable with an entirely intracardiac pacing system.

How to Implant a Leadless Pacemaker With a Tine-Based Fixation.

Two major studies have shown that leadless pacemakers are safe and effective for patients requiring right ventricular rate responsive pacing therapy. This positive result recently led to FDA approval of one of the available leadless pacing devices. While this new technology is promising, it requires a different skill set for safe implantation. In this article, we review in detail the different steps required for implantation of tine-based leadless pacemakers while providing tips and tricks to minimize complications.