A Leadless Intracardiac Transcatheter Pacing System.

BACKGROUND: A leadless intracardiac transcatheter pacing system has been designed to avoid the need for a pacemaker pocket and transvenous lead. METHODS: In a prospective multicenter study without controls, a transcatheter pacemaker was implanted in patients who had guideline-based indications for ventricular pacing. The analysis of the primary end points began when 300 patients reached 6 months of follow-up. The primary safety end point was freedom from system-related or procedure-related major complications. The primary efficacy end point was the percentage of patients with low and stable pacing capture thresholds at 6 months (≤2.0 V at a pulse width of 0.24 msec and an increase of ≤1.5 V from the time of implantation). The safety and efficacy end points were evaluated against performance goals (based on historical data) of 83% and 80%, respectively. We also performed a post hoc analysis in which the rates of major complications were compared with those in a control cohort of 2667 patients with transvenous pacemakers from six previously published studies. RESULTS: The device was successfully implanted in 719 of 725 patients (99.2%). The Kaplan-Meier estimate of the rate of the primary safety end point was 96.0% (95% confidence interval [CI], 93.9 to 97.3; P<0.001 for the comparison with the safety performance goal of 83%); there were 28 major complications in 25 of 725 patients, and no dislodgements. The rate of the primary efficacy end point was 98.3% (95% CI, 96.1 to 99.5; P<0.001 for the comparison with the efficacy performance goal of 80%) among 292 of 297 patients with paired 6-month data. Although there were 28 major complications in 25 patients, patients with transcatheter pacemakers had significantly fewer major complications than did the control patients (hazard ratio, 0.49; 95% CI, 0.33 to 0.75; P=0.001). CONCLUSIONS: In this historical comparison study, the transcatheter pacemaker met the prespecified safety and efficacy goals; it had a safety profile similar to that of a transvenous system while providing low and stable pacing thresholds. (Funded by Medtronic; Micra Transcatheter Pacing Study ClinicalTrials.gov number, NCT02004873.).

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.

Regional and ethnic differences among patients with heart failure in Asia: the Asian sudden cardiac death in heart failure registry.

AIMS: To characterize regional and ethnic differences in heart failure (HF) across Asia. METHODS AND RESULTS: We prospectively studied 5276 patients with stable HF and reduced ejection fraction (≤40%) from 11 Asian regions (China, Hong Kong, India, Indonesia, Japan, Korea, Malaysia, Philippines, Singapore, Taiwan, and Thailand). Mean age was 59.6 ± 13.1 years, 78.2% were men, and mean body mass index was 24.9 ± 5.1 kg/m2. Majority (64%) of patients had two or more comorbid conditions such as hypertension (51.9%), coronary artery disease (CAD, 50.2%), or diabetes (40.4%). The prevalence of CAD was highest in Southeast Asians (58.8 vs. 38.2% in Northeast Asians). Compared with Chinese ethnicity, Malays (adjusted odds ratio [OR] 1.97, 95% CI 1.63-2.38) and Indians (OR 1.44, 95% CI 1.24-1.68) had higher odds of CAD, whereas Koreans (OR 0.38, 95% CI 0.29-0.50) and Japanese (OR 0.44, 95% CI 0.36-0.55) had lower odds. The prevalence of hypertension and diabetes was highest in Southeast Asians (64.2 and 49.3%, respectively) and high-income regions (59.7 and 46.2%, respectively). There was significant interaction between ethnicity and region, where the adjusted odds were 3.95 (95% CI 2.51-6.21) for hypertension and 4.91 (95% CI 3.07-7.87) for diabetes among Indians from high- vs. low-income regions; and 2.60 (95% CI 1.66-4.06) for hypertension and 2.62 (95% CI 1.73-3.97) for diabetes among Malays from high- vs. low-income regions. CONCLUSIONS: These first prospective multi-national data from Asia highlight the significant heterogeneity among Asian patients with stable HF, and the important influence of both ethnicity and regional income level on patient characteristics. CLINICALTRIALSGOV IDENTIFIER: NCT01633398.

Early performance of a miniaturized leadless cardiac pacemaker: the Micra Transcatheter Pacing Study.

AIMS: Permanent cardiac pacing is the only effective treatment for symptomatic bradycardia, but complications associated with conventional transvenous pacing systems are commonly related to the pacing lead and pocket. We describe the early performance of a novel self-contained miniaturized pacemaker. METHODS AND RESULTS: Patients having Class I or II indication for VVI pacing underwent implantation of a Micra transcatheter pacing system, from the femoral vein and fixated in the right ventricle using four protractible nitinol tines. Prespecified objectives were >85% freedom from unanticipated serious adverse device events (safety) and <2 V 3-month mean pacing capture threshold at 0.24 ms pulse width (efficacy). Patients were implanted (n = 140) from 23 centres in 11 countries (61% male, age 77.0 ± 10.2 years) for atrioventricular block (66%) or sinus node dysfunction (29%) indications. During mean follow-up of 1.9 ± 1.8 months, the safety endpoint was met with no unanticipated serious adverse device events. Thirty adverse events related to the system or procedure occurred, mostly due to transient dysrhythmias or femoral access complications. One pericardial effusion without tamponade occurred after 18 device deployments. In 60 patients followed to 3 months, mean pacing threshold was 0.51 ± 0.22 V, and no threshold was ≥2 V, meeting the efficacy endpoint (P < 0.001). Average R-wave was 16.1 ± 5.2 mV and impedance was 650.7 ± 130 ohms. CONCLUSION: Early assessment shows the transcatheter pacemaker can safely and effectively be applied. Long-term safety and benefit of the pacemaker will further be evaluated in the trial. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov ID NCT02004873.

The rationale and design of the Micra Transcatheter Pacing Study: safety and efficacy of a novel miniaturized pacemaker.

AIMS: Recent advances in miniaturization technologies and battery chemistries have made it possible to develop a pacemaker small enough to implant within the heart while still aiming to provide similar battery longevity to conventional pacemakers. The Micra Transcatheter Pacing System is a miniaturized single-chamber pacemaker system that is delivered via catheter through the femoral vein. The pacemaker is implanted directly inside the right ventricle of the heart, eliminating the need for a device pocket and insertion of a pacing lead, thereby potentially avoiding some of the complications associated with traditional pacing systems. METHODS AND RESULTS: The Micra Transcatheter Pacing Study is currently undergoing evaluation in a prospective, multi-site, single-arm study. Approximately 720 patients will be implanted at up to 70 centres around the world. The study is designed to have a continuously growing body of evidence and data analyses are planned at various time points. The primary safety and efficacy objectives at 6-month post-implant are to demonstrate that (i) the percentage of Micra patients free from major complications related to the Micra system or implant procedure is significantly higher than 83% and (ii) the percentage of Micra patients with both low and stable thresholds is significantly higher than 80%. The safety performance benchmark is based on a reference dataset of 977 subjects from 6 recent pacemaker studies. CONCLUSIONS: The Micra Transcatheter Pacing Study will assess the safety and efficacy of a miniaturized, totally endocardial pacemaker in patients with an indication for implantation of a single-chamber ventricular pacemaker. CLINICALTRIALSGOV REGISTRATION ID: NCT02004873.

Prospective randomized study to assess the efficacy of site and rate of atrial pacing on long-term progression of atrial fibrillation in sick sinus syndrome: Septal Pacing for Atrial Fibrillation Suppression Evaluation (SAFE) Study.

BACKGROUND: Atrial-based pacing is associated with lower risk of atrial fibrillation (AF) in sick sinus syndrome compared with ventricular pacing; nevertheless, the impact of site and rate of atrial pacing on progression of AF remains unclear. We evaluated whether long-term atrial pacing at the right atrial (RA) appendage versus the low RA septum with (ON) or without (OFF) a continuous atrial overdrive pacing algorithm can prevent the development of persistent AF. METHODS AND RESULTS: We randomized 385 patients with paroxysmal AF and sick sinus syndrome in whom a pacemaker was indicated to pacing at RA appendage ON (n=98), RA appendage OFF (n=99), RA septum ON (n=92), or RA septum OFF (n=96). The primary outcome was the occurrence of persistent AF (AF documented at least 7 days apart or need for cardioversion). Demographic data were homogeneous across both pacing site (RA appendage/RA septum) and atrial overdrive pacing (ON/OFF). After a mean follow-up of 3.1 years, persistent AF occurred in 99 patients (25.8%; annual rate of persistent AF, 8.3%). Alternative site pacing at the RA septum versus conventional RA appendage (hazard ratio=1.18; 95% confidence interval, 0.79-1.75; P=0.65) or continuous atrial overdrive pacing ON versus OFF (hazard ratio=1.17; 95% confidence interval, 0.79-1.74; P=0.69) did not prevent the development of persistent AF. CONCLUSIONS: In patients with paroxysmal AF and sick sinus syndrome requiring pacemaker implantation, an alternative atrial pacing site at the RA septum or continuous atrial overdrive pacing did not prevent the development of persistent AF. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. UNIQUE IDENTIFIER: NCT00419640.

The Long-Term Multicenter Observational Study of Dabigatran Treatment in Patients With Atrial Fibrillation (RELY-ABLE) Study.

BACKGROUND: During follow-up of between 1 and 3 years in the Randomized Evaluation of Long-term Anticoagulation Therapy (RE-LY) trial, 2 doses of dabigatran etexilate were shown to be effective and safe for the prevention of stroke or systemic embolism in patients with atrial fibrillation. There is a need for longer-term follow-up of patients on dabigatran and for further data comparing the 2 dabigatran doses. METHODS AND RESULTS: Patients randomly assigned to dabigatran in RE-LY were eligible for the Long-term Multicenter Extension of Dabigatran Treatment in Patients with Atrial Fibrillation (RELY-ABLE) trial if they had not permanently discontinued study medication at the time of their final RE-LY study visit. Enrolled patients continued to receive the double-blind dabigatran dose received in RE-LY, for up to 28 months of follow up after RE-LY (median follow-up, 2.3 years). There were 5851 patients enrolled, representing 48% of patients originally randomly assigned to receive dabigatran in RE-LY and 86% of RELY-ABLE-eligible patients. Rates of stroke or systemic embolism were 1.46% and 1.60%/y on dabigatran 150 and 110 mg twice daily, respectively (hazard ratio, 0.91; 95% confidence interval, 0.69-1.20). Rates of major hemorrhage were 3.74% and 2.99%/y on dabigatran 150 and 110 mg (hazard ratio, 1.26; 95% confidence interval, 1.04-1.53). Rates of death were 3.02% and 3.10%/y (hazard ratio, 0.97; 95% confidence interval, 0.80-1.19). Rates of hemorrhagic stroke were 0.13% and 0.14%/y. CONCLUSIONS: During 2.3 years of continued treatment with dabigatran after RE-LY, there was a higher rate of major bleeding with dabigatran 150 mg twice daily in comparison with 110 mg, and similar rates of stroke and death.

A single centre experience of the efficacy and safety of dabigatran etexilate used for stroke prevention in atrial fibrillation.

The use of novel anticoagulants such as dabigatran are increasing. Despite increased risks of intracerebral haemorrhage with warfarin among Asians, there is little published data on dabigatran to assess 'real world' efficacy and safety of dabigatran therapy in Asia. This was a retrospective observational study of patients prescribed dabigatran between 2010 and 2013. Data was available for 510 patients: median age 68 years (range 20-91), median CHA2DS2-VASc score was 2 and median HAS-BLED score was 2. The average follow-up duration of 315 days (range: 1-1,096). The overall discontinuation rate was 16% after a median 252 days of treatment with dabigatran. There were 17 (3.3%) patients with minor bleeding, 2 (0.4%) had major bleeding episodes. 20 patients (3.9%) developed dyspepsia which was the most common side effect. The rate of occurrences of adverse effects and bleeding were lower than those seen in the RE-LY trial. None of the patients had an ischaemic stroke, 1 (0.2%) patient had a haemorrhagic stroke. Out of 510 patients, 158 patients (31%) were switched to dabigatran from warfarin. This showed that patients frequently preferred the dabigatran due to convenience when given a choice to switch from warfarin. We report one of the largest registry of Asian patients. Reassuringly, we found that our cohort had a low rate of rate of ischaemic stroke, low rates of side effects and bleeding with the drug.

Dabigatran versus warfarin: effects on ischemic and hemorrhagic strokes and bleeding in Asians and non-Asians with atrial fibrillation.

BACKGROUND AND PURPOSE: Intracranial hemorrhage rates are higher in Asians than non-Asians, especially in patients receiving warfarin. This randomized evaluation of long-term anticoagulation therapy subgroup analysis assessed dabigatran etexilate (DE) and warfarin effects on stroke and bleeding rates in patients from Asian and non-Asian countries. METHODS: There were 2782 patients (15%) from 10 Asian countries and 15 331 patients from 34 non-Asian countries. A Cox regression model, with terms for treatment, region, and their interaction was used. RESULTS: Rates of stroke or systemic embolism in Asians were 3.06% per year on warfarin, 2.50% per year on DE 110 mg BID (DE 110), and 1.39% per year on DE 150 mg BID (DE 150); in non-Asians, the rates were 1.48%, 1.37%, and 1.06% per year with no significant treatment-by-region interactions. Hemorrhagic stroke on warfarin occurred more often in Asians than non-Asians (hazard ratio [HR], 2.4; 95% confidence interval [CI], 1.3-4.7; P=0.007), with significant reductions for DE compared with warfarin in both Asian (DE 110 versus warfarin HR, 0.15; 95% CI, 0.03-0.66 and DE 150 versus warfarin HR, 0.22; 95% CI, 0.06-0.77) and non-Asian (DE 110 versus warfarin HR, 0.37; 95% CI, 0.19-0.72 and DE 150 versus warfarin HR, 0.28; 95% CI, 0.13-0.58) patients. Major bleeding rates in Asians were significantly lower on DE (both doses) than warfarin (warfarin 3.82% per year, DE 110 2.22% per year, and DE 150 2.17% per year). CONCLUSIONS: Hemorrhagic stroke rates were higher on warfarin in Asians versus non-Asians, despite similar blood pressure, younger age, and lower international normalized ratio values. Hemorrhagic strokes were significantly reduced by DE in both Asians and non-Asians. DE benefits were consistent across Asian and non-Asian subgroups. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT00262600.

Biventricular pacing in patients with bradycardia and normal ejection fraction.

BACKGROUND: Observational studies suggest that conventional right ventricular apical pacing may have a deleterious effect on left ventricular function. In this study, we examined whether biventricular pacing is superior to right ventricular apical pacing in preventing deterioration of left ventricular systolic function and cardiac remodeling in patients with bradycardia and a normal ejection fraction. METHODS: In this prospective, double-blind, multicenter study, we randomly assigned 177 patients in whom a biventricular pacemaker had been successfully implanted to receive biventricular pacing (89 patients) or right ventricular apical pacing (88 patients). The primary end points were the left ventricular ejection fraction and left ventricular end-systolic volume at 12 months. RESULTS: At 12 months, the mean left ventricular ejection fraction was significantly lower in the right-ventricular-pacing group than in the biventricular-pacing group (54.8+/-9.1% vs. 62.2+/-7.0%, P<0.001), with an absolute difference of 7.4 percentage points, whereas the left ventricular end-systolic volume was significantly higher in the right-ventricular-pacing group than in the biventricular-pacing group (35.7+/-16.3 ml vs. 27.6+/-10.4 ml, P<0.001), with a relative difference between the groups in the change from baseline of 25% (P<0.001). The deleterious effect of right ventricular apical pacing occurred in prespecified subgroups, including patients with and patients without preexisting left ventricular diastolic dysfunction. Eight patients in the right-ventricular-pacing group (9%) and one in the biventricular-pacing group (1%) had ejection fractions of less than 45% (P=0.02). There was one death in the right-ventricular-pacing group, and six patients in the right-ventricular-pacing group and five in the biventricular-pacing group were hospitalized for heart failure (P=0.74). CONCLUSIONS: In patients with normal systolic function, conventional right ventricular apical pacing resulted in adverse left ventricular remodeling and in a reduction in the left ventricular ejection fraction; these effects were prevented by biventricular pacing. (Centre for Clinical Trials number, CUHK_CCT00037.)

A prospective randomized study to assess the efficacy of rate and site of atrial pacing on long-term development of atrial fibrillation.

The Septal Pacing for Atrial Fibrillation Suppression Evaluation (SAFE) study is a single-blinded, parallel randomized designed multicenter study in pacemaker indicated patients with paroxysmal atrial fibrillation (AF). The objective is to evaluate whether the site of atrial pacing--conventional right atrial appendage versus low atrial septal--with or without atrial overdrive pacing will influence the development of persistent AF. The study will provide a definitive answer to whether a different atrial pacing site or the use of AF suppression pacing or both can give incremental antiarrhythmic benefit when one is implanting a device for a patient with a history of paroxysmal AF.

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).

Techniques for successful early retrieval of the Micra transcatheter pacing system: A worldwide experience.

BACKGROUND: Experience with retrieval of the Micra transcatheter pacing system (TPS) is limited because of its relatively newer technology. Although abandonment of the TPS at end of life is recommended, certain situations such as endovascular infection or device embolization warrant retrieval. OBJECTIVE: The purpose of this study was to report the worldwide experience with successful retrieval of the Micra TPS. METHODS: A list of all successful retrievals of the currently available leadless pacemakers (LPs) was obtained from the manufacturer of Micra TPS. Pertinent details of retrieval, such as indication, days postimplantation, equipment used, complications, and postretrieval management, were obtained from the database collected by the manufacturer. Other procedural details were obtained directly from the operators at each participating site. RESULTS: Data from the manufacturer consisted of 40 successful retrievals of the Micra TPS. Operators for 29 retrievals (73%) provided the consent and procedural details. Of the 29 retrievals, 11 patients underwent retrieval during the initial procedure (immediate retrieval); the other 18 patients underwent retrieval during a separate procedure (delayed retrieval). Median duration before delayed retrieval was 46 days (range 1-95 days). The most common reason for immediate retrieval was elevated pacing threshold after tether removal. The most common reasons for delayed retrieval included elevated pacing threshold at follow-up, endovascular infection, and need for transvenous device. Mean procedure duration was 63.11 ± 56 minutes. All retrievals involved snaring via a Micra TPS delivery catheter or steerable sheath. No serious complications occurred during the reported retrievals. CONCLUSION: Early retrieval of the Micra TPS is feasible and safe.

The Pacing to Avoid Cardiac Enlargement (PACE) trial: clinical background, rationale, design, and implementation.

BACKGROUND: Deleterious effect on left ventricular (LV) function was observed with conventional right ventricular apical (RVA) pacing. Preliminary data suggested that biventricular pacing (BiV) may be superior to RVA pacing in patients with LV systolic dysfunction. However, the optimal pacing mode and site(s) for patients with normal LV systolic function remain controversial. METHODS: The Pacing to Avoid Cardiac Enlargement (PACE) trial is a prospective, multicenter, randomized, double blinded, parallel, controlled study aiming to determine if BiV pacing is better than conventional RVA pacing in preserving LV systolic function and preventing remodeling in patients with LV ejection fraction (EF) > or = 45% indicated for pacing. This study targets to recruit 200 patients from various centers in Asia, all of whom will receive BiV pacemaker implantation before being randomized to either atrial-based RVA or BiV pacing for 1 year. Their echocardiographic parameters including LV volumes, left ventricular ejection fraction (LVEF), and dyssynchrony index by tissue Doppler imaging, exercise capacity, quality of life assessment, neurohormone levels, and clinical events will be assessed before and after pacing. The primary endpoints are changes in LV end-systolic volume and LVEF 1 year after pacing. It is designed with 90% power to detect a 5% difference in the LVEF after 1 year of pacing. The enrollment began in 2006. It is expected to conclude at the end of 2008. CONCLUSION: The PACE trial will determine whether atrial-based BiV pacing can preserve LV systolic function and prevent LV adverse remodeling induced by conventional RVA pacing in patients with normal LV systolic function and standard pacing indication.

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.

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.

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.

Disparity Between Indications for and Utilization of Implantable Cardioverter Defibrillators in Asian Patients With Heart Failure.

BACKGROUND: Implantable cardioverter defibrillators (ICDs) are lifesaving devices for patients with heart failure (HF) and reduced ejection fraction. However, utilization and determinants of ICD insertion in Asia are poorly defined. We determined the utilization, associations of ICD uptake, patient-perceived barriers to device therapy and, impact of ICDs on mortality in Asian patients with HF. METHODS AND RESULTS: Using the prospective ASIAN-HF (Asian Sudden Cardiac Death in Heart Failure) registry, 5276 patients with symptomatic HF and reduced ejection fraction (HFrEF) from 11 Asian regions and across 3 income regions (high: Hong Kong, Japan, Korea, Singapore, and Taiwan; middle: China, Malaysia, and Thailand; and low: India, Indonesia, and Philippines) were studied. ICD utilization, clinical characteristics, as well as device perception and knowledge, were assessed at baseline among ICD-eligible patients (EF ≤35% and New York Heart Association Class II-III). Patients were followed for the primary outcome of all-cause mortality. Among 3240 ICD-eligible patients (mean age 58.9±12.9 years, 79.1% men), 389 (12%) were ICD recipients. Utilization varied across Asia (from 1.5% in Indonesia to 52.5% in Japan) with a trend toward greater uptake in regions with government reimbursement for ICDs and lower out-of-pocket healthcare expenditure. ICD (versus non-ICD) recipients were more likely to be older (63±11 versus 58±13 year; P<0.001), have tertiary (versus ≤primary) education (34.9% versus 18.1%; P<0.001) and be residing in a high (versus low) income region (64.5% versus 36.5%; P<0.001). Among 2000 ICD nonrecipients surveyed, 55% were either unaware of the benefits of, or needed more information on, device therapy. ICD implantation reduced risks of all-cause mortality (hazard ratio, 0.71; 95% confidence interval, 0.52-0.97) and sudden cardiac deaths (hazard ratio, 0.33; 95% confidence interval, 0.14-0.79) over a median follow-up of 417 days. CONCLUSIONS: ICDs reduce mortality risk, yet utilization in Asia is low; with disparity across geographic regions and socioeconomic status. Better patient education and targeted healthcare reforms in extending ICD reimbursement may improve access. CLINICAL TRIAL REGISTRATION: URL: https://clinicaltrials.gov/ct2/show/NCT01633398. Unique identifier: NCT01633398.

Intelligent classification of electrocardiogram (ECG) signal using extended Kalman Filter (EKF) based neuro fuzzy system.

This study presents the development of a hybrid system consisting of an ensemble of Extended Kalman Filter (EKF) based Multi Layer Perceptron Network (MLPN) and a one-pass learning Fuzzy Inference System using Look-up Table Scheme for the recognition of electrocardiogram (ECG) signals. This system can distinguish various types of abnormal ECG signals such as Ventricular Premature Cycle (VPC), T wave inversion (TINV), ST segment depression (STDP), and Supraventricular Tachycardia (SVT) from normal sinus rhythm (NSR) ECG signal.

A Comparison of Dabigatran With Warfarin for Stroke Prevention in Atrial Fibrillation in an Asian Population.

BACKGROUND: The Asian population with atrial fibrillation (AF) have a higher risk of stroke than the caucasian population and a higher risk of intracranial bleeding when anticoagulated with warfarin. There are few real-world studies comparing the efficacy of non-vitamin K antagonist oral anticoagulants (NOACs) and warfarin among Asian patients to assess its outcomes of ischemic stroke and hemorrhagic stroke. METHODS: A retrospective cohort study of 1000 patients on dabigatran and warfarin from 2009 to 2013. RESULTS: Data were available for 500 patients on dabigatran and 500 patients on warfarin. The average follow-up duration was 315 ± 280 days in the dabigatran group and 355 ± 232 in the warfarin group. The time in therapeutic range (TTR) was 53.2% in the warfarin-treated group, with 32.8% of patients in the subtherapeutic international normalized ratio range of <2. None of the patients in the dabigatran group had ischemic cerebrovascular accident (CVA) compared to 4 (0.8%) patients in the warfarin group, hazard ratio (HR) 0.13, P = .3. There was 1 (0.2%) patient in both dabigatran and warfarin groups with hemorrhagic CVA (HR 1.16, P = .92). There were 3 (0.6%) patients with major bleeding in the dabigatran group compared to 2 (0.4%) patients in the warfarin group (HR 1.57, P = .59). CONCLUSION: There were similar rates of efficacy for outcomes of ischemic CVA, hemorrhagic CVA, and bleeding when comparing dabigatran with warfarin. Our study shows that despite similar efficacy, suboptimal TTR rates and inconveniences with warfarin demonstrate that NOACs are preferred for stroke prevention in AF.