Pacemaker Group Research Articles

Comparison in Clinical Outcomes Between Leadless and Conventional Transvenous Pacemaker Following Transcatheter Aortic Valve Implantation.

Atrioventricular block is a common complication of transcatheter aortic valve implantation (TAVI). Although conventional transvenous dual-chamber (DDD) pacemaker (PM) is ideal for atrioventricular block, leadless PM, which is less invasive, may be suitable for frail TAVI patients. Little is known about clinical outcomes of this newer device following TAVI. A total of 330 consecutive patients undergoing TAVI were reviewed. Of these, PM cases without atrial fibrillation were studied. Indication for leadless PM was based on heart team discussion. PM implantations were performed in 30 patients (9.1%), and 24 patients (7.3%) had no atrial fibrillation. These 24 patients had 14 DDD-PMs and 10 leadless PMs, and formed the two study groups. Baseline characteristics were similar except for ejection fraction: median ages were 83.0 years (IQR, 81.0-87.0 years) vs 86.5 years (IQR, 83.5-90.3) (P=.18); 11 (78.6%) vs 8 (80%) were women (P=.67); Society of Thoracic Surgeons scores were 5.1% (IQR, 3.8%-5.9%) vs 5.3% (IQR, 3.4%-8.5%) (P=.82); and ejection fractions were 68.0% (IQR, 66.0%-70.5%) vs 59.0% (IQR, 52.8%-69.3%) (P=.049), for the DDD-PM and leadless PM groups, respectively. There was 1 case of atrial lead dislodgment in the DDD-PM group; otherwise, no complications related to the implantation procedure were found. The leadless PM group showed numerically shorter hospital stay: 12.5 days (range, 9.0-17.8 day) in the DDD-PM group vs 10.5 days (range, 7.8-15.3 days) in the leadless PM group (P=.44). Six-month follow-up revealed no significant differences in incidence of heart failure rehospitalizations or deaths: 2 (14.3%) in the DDD-PM group vs 2 (25%) in the leadless PM group (P=.47); and 2 (14.3%) in the DDD-PM group vs 0 (0%) in the leadless PM group (P=.39), respectively. Patients with leadless PM following TAVI may have shorter hospital stays, and clinical outcomes can be comparable with DDD-PMs. Leadless PMs may therefore be a reasonable option for frail TAVI patients.

P425Single procedure pace and ablate. evaluation of efficacy and safety comparing three different vascular routes

Abstract Funding Acknowledgements No financial support for this study Introduction Permanent pacemaker implantation combined with AVN ablation is a well-established treatment for rate control in patients with atrial fibrillation refractory to medical therapy. At the same sitting, this has been achieved in a single procedure via the subclavian vein (SCV) for both pacemaker implantation and AVN ablation, by pacemaker implantation via the SCV with femoral access for AVN ablation or by using the femoral vein (FV) for leadless pacemaker implantation and AVN ablation with a coaxial single-puncture technique. We evaluated all combined procedures (pacemaker implantation and AVN ablation at the same sitting) performed in a single centre over 9 years comparing clinical outcomes, complications rates and procedure times. Statistical methods: Continuous variables are described as mean ± standard deviation (SD), and statistical differences between groups were evaluated by one-way ANOVA. A X2 test was used for categorical variables, with Fisher’s exact test for any field where the expected frequency was ≤5 with pvalue < 0.05 considered as statistically significant. The statistical analysis was performed using SPSS software package. Results 141 patients underwent AVN ablation at our institution as part of a ‘pace and ablate’ single procedure strategy between 14/2/11 and 10/6/19. 61 patients had a combined procedure via the SCV, 66 patients had pacemaker implanted via the SCV and AVN ablation via the FV in the same sitting and 14 patients had leadless pacemaker (Micra) implantation and AVN ablation via the FV. Our findings suggest that the fluoroscopy time as well as the total catheter laboratory time were much less in the Micra group compared to the other groups. In the conventional pacemaker groups (group 1 and 2), the fluoroscopy time was not statistically different between the two. There was a trend towards acute procedural failure, switching to another access as well as a higher complication rate in the SCV group, however this has not reached statistical significance. Conclusion Our early data suggests that pacemaker implantation and AVN ablation with a coaxial single femoral vein puncture technique is safe and takes less fluoroscopy time as well as total laboratory time. Procedural outcomes All (n = 141) Group 1: SCV (n = 61) Group 2: FV (n = 66) Group 3: Micra (n = 14) P-value Total cath-lab time (mins) 113.1 ± 40.4 106.2 ± 37.2 125.7 ± 42.5 86.9 ± 23.1 0.001 Total fluoroscopy time (mins) 8.8 ± 7.6 11 ± 7.8 7.7 ± 7.6 4.5 ± 3 0.0001 Acute procedural failure, n (%) 9 (6.4) 7 (11.5) 2 (3) 0 (0) **0.6 Complications, n (%) 7 (4.9) 5 (8.2) 2 (3) 0 (0) **0.62 **Fisher"s exact test applied to analysis of Micra VS Other methods

Syncope and bifascicular block in the absence of structural heart disease

The treatment of patients with bifascicular block (BFB) and syncope in the absence of structural heart disease (SHD) is not well defined. The objective of our study is to compare pacemaker empirical implantation with the use of electrophysiological studies (EPS). This is a prospective cohort study that included 77 patients with unexplained cardiogenic syncope and BFB without structural heart disease between 1997 and 2012. Two groups: 36 patients received empirical pacemakers (Group A) and 41 underwent EPS (Group B) to guide their treatment. The incidence of syncope recurrence and atrioventricular block was lower in group A. Mortality and complication rates were similar between both groups. Multivariate analysis demonstrated a higher number of events (combined endpoint) in group B. Our study shows that treatment according to EPS does not improve the results of a treatment strategy based on empirical pacemaker.

Involving patients as key stakeholders in the design of cardiovascular implantable electronic device data dashboards: Implications for patient care.

BackgroundData from remote monitoring (RM) of cardiovascular implantable electronic devices (CIEDs) currently are not accessible to patients despite demand. The typical RM report contains multiple pages of data for trained technicians to read and interpret and requires a patient-centered approach to be curated to meet individual user needs.ObjectiveThe purpose of this study was to understand which RM data elements are important to patients and to gain design insights for displaying meaningful data in a digital dashboard.MethodsAdults with implantable cardioverter–defibrillators (ICDs) and pacemakers (PMs) participated in this 2-phase, user-centered design study. Phase 1 included a card-sorting activity to prioritize device data elements. Phase 2 included one-on-one design sessions to gather insights and feedback about a visual display (labels and icons).ResultsTwenty-nine adults (mean age 71.8 ± 11.6 years; 51.7% female; 89.7% white) participated. Priority data elements for both ICD and PM groups in phase 1 (n = 19) were related to cardiac episodes, device activity, and impedance values. Recommended replacement time for battery was high priority for the PM group but not the ICD group. Phase 2 (n = 10) revealed that patients would like descriptive, nontechnical terms to depict the data and icons that are intuitive and informative.ConclusionThis user-centered design study demonstrated that patients with ICDs and PMs were able to prioritize specific data from a comprehensive list of data elements that they had never seen before. This work contributes to the goal of sharing RM data with patients in a way that optimizes the RM feature of CIEDs for improving patient outcomes and clinical care.

Artifact of a Cardiac Pacemaker on Low Dose Chest CT

인공심장박동기와 제세동기를 삽입한 경우에 발생하는 인공물이 폐암의 조기 발견을 위해 시행되는 저선량 흉부CT에서 어떠한 영향을 주는지 알아보고자 한다. Lungman phantom과 인공심장 박동기를 이용하여 대조군과 실험군을 설정하여 인공심장박동기 주변 인공물의 CT value와 표준편차를 측정하였다. 인공심장박동기 주변으로 영상정보를 상실 (black-hole artifact) 하거나 선속 경화(streak artifact) 인공물을 확인하였다. 수검자들의 다양한 체형과 인공심장 박동기의 위치에 따라 폐암의 조기발견을 위한 저 선량 흉부CT 검사 시 수검자들에게 미세 병변의 발견을 저해하는 요인으로 작용할 것이라 생각되며 임상에서의 실질적인 검사에 적용할 수 있는 더 많은 연구가 필요할 것이다.We would like to find out how the artificial insemination of an artificial cardiac pacemaker and defibrillator affects the low-dose chest CT performed for early detection of lung cancer. Using Lungman phantom and artificial heart pacemaker, the control and experimental group were set up to measure the CT value and standard deviation of the man-made objects around the artificial heart pacemaker. Black-hole artifact (black-hole artifact) or pre-speed curing (streak artifact) artifacts were identified around the artificial heartbeater. Depending on the various body types of the examinees and the location of the artificial heart pacemakers, low dose chest CT examinations for early detection of lung cancer are thought to serve as inhibitors to the detection of fine lesions and will require more research to be applied to practical examinations in clinical trials.

Cognitive assessments in patients with implantable cardiac pacemaker

Bradyarrhythmias cause low cerebral blood flow and imbalance of the cerebral autore-gulation, favoring neuronal ischemia and cognitive dysfunction. The main treatment in bradyarrhythmia is pacemaker (PM) implantation, which keeps the heart rate in normal range and increase cardiac output. The present study proposed the cognitive evaluation of PM group patients and a control group (CG), but with similar cardiovascular risk factors. Cognitive assessment has been achieved by applying the Mini-Mental State Examination (MMSE), Clock-Drawing Test (CDT) and Mini Clock for both groups.

The feasibility of leadless pacemaker implantation for superelderly patients

The safety and efficacy of the leadless pacemaker (LP) have been confirmed in previous reports, yet studies on LPs in superelderly patients are limited. A total of 62 patients aged over 85 years old were implanted with single-chamber pacemakers due to symptomatic bradyarrhythmia at Sakakibara Heart Institute from May 2014 through July 2019. We divided them into two groups, a transvenous (TV) single-chamber pacemaker group (35 patients) and an LP group (27 patients), and compared the groups. Mean participant age was 90.3 ± 3.8 y.o., 41.9% were male, and mean participant body mass index (BMI) was 21.3kg/m2 . The LP group contained a significantly larger proportion of patients with dementia than the TV group did (63%vs. 37.1%, P=.04). The complication-free rate tended to be lower in the LP group in spite of the higher frequency of dementia (88.6%vs. 92.6%, P=.68). At implantation, the pacing threshold was significantly higher in the LP group than in the TV group (1.30 ± 0.91 V vs. 0.71 ± 0.23 V, P<.01), but over the first 3 months after the operation the pacing threshold in the LP group gradually improved (0.82 ± 0.2 V vs. 1.05 ± 1.02 V, P=.16). The procedure time and time from operation to discharge were also shorter in the LP group. LP implantation appears to be safe and is accordingly becoming the cornerstone for Japanese superelderly patients indicated for single-chamber pacemakers, even for those with small bodies and dementia. However, careful procedures and long follow-ups are needed until a greater volume of data is reported.

Long-term Clinical Outcomes of Radiofrequency Catheter Ablation versus Permanent Pacemaker Implantation in Patients with Tachycardia-Bradycardia Syndrome.

Background and ObjectivesPacemaker (PM) implantation is a well-accepted treatment option for patients with paroxysmal atrial fibrillation (AF) and related tachycardia-bradycardia syndrome (TBS). Data on the long-term clinical outcomes after radiofrequency catheter ablation (RFCA) or PM implantation are sparse.MethodsThe medical records of 217 patients with TBS were retrospectively assessed. Outcomes in patients who underwent RFCA (n=108, 49.8%) were compared to those with PM implantation (n=109, 50.2%). The clinical outcomes were sinus rhythm maintenance, conversion to persistent AF, additional procedure or crossover, and the composite of cardiovascular hospitalization and death.ResultsDuring the follow-up period (mean 3.5±2.0 years), the RFCA group, compared to the PM group, showed better sinus rhythm maintenance (adjusted hazard ratio [aHR], 0.27; 95% confidence interval [CI], 0.15–0.46; p=0.002) and less progression to persistent AF (aHR, 0.20; 95% CI, 0.06–0.63; p=0.006). Additional procedure or crossover did not differ significantly between the groups (aHR, 2.07; 95% CI, 0.71–6.06; p=0.185 and aHR, 0.69; 95% CI, 10.8–2.67; p=0.590, respectively). Most RFCA patients (92.6%) did not require pacemaker implantation during long term follow-up period (>3.5 years). The composite endpoint of cardiovascular rehospitalization and death was not significantly different between the groups (aHR, 0.92; 95% CI, 0.50–1.66; p=0.769).ConclusionsRFCA is an effective alternative to PM implantation in patients with TBS. In these patients, successful RF ablation of AF is related to a higher rate of sinus rhythm maintenance compared to PM implantation, and the composite outcome of cardiovascular rehospitalization and death is similar.

Evaluating the left ventricular hemodynamic phenomena of DDD septum pacemaker implants using vector flow mapping.

We set out to undertake a preliminary assessment of the left ventricular hemodynamic status with right ventricular double-chamber pacing by energy loss (EL), wall shear stress (WSS), and circulation intensity (CIR) of vector flow mapping (VFM). We also planned to evaluate the value of VFM technology by measuring cardiac function after pacemaker implantation. Data from 58 patients living with right ventricular double-chamber (right ventricular septal) pacemakers as well as 58 healthy volunteers matched in age and gender were collected. The EL, numbers of vortex cycles (n), area (A), CIR, and WSS of the left ventricle with different phases of the same cardiac cycle were obtained. The EL of the left ventricle was significantly higher in the pacemaker group than the control group at partial section of atrial contraction (AC), isovolumetric contraction (IVC), and rapid ejection (RE) (P<0.05). The WSS of the left ventricle was significantly lower in the pacemaker group than the control group at part of the section in the rapid filling (RF), the AC, IVC, and RE phase (P<0.05). EL in the left ventricular was significantly increased, while related WSS was significantly decreased in patients with right ventricular double-chamber pacing. Our exploration of the state of the flow field in the left ventricular cavity revealed that the implantation of the right ventricular double-chamber pacemaker led to an abnormal left ventricular hemodynamic state, reducing the left ventricular systolic efficiency.

Permanent pacing post-Fontan is not associated with reduced long-term survival.

The Fontan procedure is the final stage of surgical palliation for a single-ventricle circulation. Significant complications are common including rhythm disturbance necessitating implantation of a permanent pacemaker. This has been widely considered a negative prognostic indicator. This single-centre, retrospective case control study involved all patients who underwent the Fontan procedure at the Leeds Congenital Heart Unit between 1990 and 2015 and have had regular follow-up in Yorkshire and Humber, United Kingdom. 167 Fontan patients were identified of which 2 were excluded for having a pre-procedure pacemaker. Of the remainder, 23 patients required a pacemaker. Outcomes were survival, early and late complications, need for further intervention and oxygen saturation in long-term follow-up. There was no difference in survival (30-day survival pacemaker 92.6%, sinus rhythm 90.5%, p = 0.66, 1-year pacemaker 11.1%, sinus rhythm 10.1%, p = 1). The pacemaker group was more likely to have cerebral or renal complications in the first-year post-procedure (acute kidney injury: sinus rhythm 0.8%, pacemaker 19.1%, p = 0.002). No difference was observed in longer term complications including protein losing enteropathy (sinus rhythm 3.5%, pacemaker 0% p = 1). There was no difference in saturations between the two groups at follow-up. Paced patients were more likely to have required further intervention, with a higher incidence of cardiopulmonary bypass procedures (sinus rhythm 6.3%, pacemaker 35%, p < 0.001). Despite an increase in early complications and the need for further interventions, pacemaker requirement does not appear to affect long-term survival following the Fontan procedure.

The differential contribution of pacemaker neurons to synaptic transmission in the pyloric network of the Jonah crab, Cancer borealis.

Many neurons receive synchronous input from heterogeneous presynaptic neurons with distinct properties. An instructive example is the crustacean stomatogastric pyloric circuit pacemaker group, consisting of the anterior burster (AB) and pyloric dilator (PD) neurons, which are active synchronously and exert a combined synaptic action on most pyloric follower neurons. Previous studies in lobster have indicated that AB is glutamatergic, whereas PD is cholinergic. However, although the stomatogastric system of the crab Cancer borealis has become a preferred system for exploration of cellular and synaptic basis of circuit dynamics, the pacemaker synaptic output has not been carefully analyzed in this species. We examined the synaptic properties of these neurons using a combination of single-cell mRNA analysis, electrophysiology, and pharmacology. The crab PD neuron expresses high levels of choline acetyltransferase and the vesicular acetylcholine transporter mRNAs, hallmarks of cholinergic neurons. In contrast, the AB neuron expresses neither cholinergic marker but expresses high levels of vesicular glutamate transporter mRNA, consistent with a glutamatergic phenotype. Notably, in the combined synapses to follower neurons, 70-75% of the total current was blocked by putative glutamatergic blockers, but short-term synaptic plasticity remained unchanged, and although the total pacemaker current in two follower neuron types was different, this difference did not contribute to the phasing of the follower neurons. These findings provide a guide for similar explorations of heterogeneous synaptic connections in other systems and a baseline in this system for the exploration of the differential influence of neuromodulators.NEW & NOTEWORTHY The pacemaker-driven pyloric circuit of the Jonah crab stomatogastric nervous system is a well-studied model system for exploring circuit dynamics and neuromodulation, yet the understanding of the synaptic properties of the two pacemaker neuron types is based on older analyses in other species. We use single-cell PCR and electrophysiology to explore the neurotransmitters used by the pacemaker neurons and their distinct contribution to the combined synaptic potentials.

Electrocardiographic and clinical predictors of permanent pacemaker insertion following Perceval sutureless aortic valve implantation

Sutureless aortic valve replacement surgery (AVR) is a reasonable alternative surgical approach in those patients with aortic stenosis who would benefit from reduced cross clamp time, such as elderly and high-risk patients. We sought to evaluate the incidence of pacemaker (PM) implantation following sutureless AVR and to analyse possible pre-operative electrocardiographic and clinical predictors of PM implantation. Between November 2013 and March 2015, 58 patients (male 43%, age 77.9 ± 4.9 years) having undergone sutureless AVR with a Perceval prosthesis (Sorin Biomedica Cardio Srl, Saluggia, Italy) were taken into consideration for our analysis. During a mean follow up of 13.8 ± 5.0 months (median 13 months), 14 patients (24.1%) underwent pacemaker (PM) implantation following sutureless AVR procedure. Among these patients, 12 (86%) presented III degree atrioventricular (AV) block, 1 (7%) presented II degree AV block, and remaining one (7%) severe symptomatic bradycardia. The comparison of pre-operative characteristics between PM group and no PM group highlighted that QRS duration, EuroSCORE II index and chronic renal dysfunction were significantly associated with the development of AV conduction abnormalities/symptomatic bradycardia requiring PM implantation (respectively, p = 0.01, p = 0.02 and p = 0.03). The incidence of PM implantation after sutureless AVR was 24.1% in the present study. The EuroSCORE II, QRS duration and renal dysfunction were significantly associated with higher risk of AV conduction abnormalities/symptomatic bradycardia requiring PM placement.

Etiology of tricuspid valve disease is a predictor of bradyarrhythmia after tricuspid valve surgery.

The tricuspid valve is situated in close proximity to cardiac conduction tissue and damage to this tissue can affect postoperative rhythm. The aim of this study was to quantify the incidence of pacemaker requirement after tricuspid valve surgery and investigate predictors. Data were collected via our operative data collection system and patient files. All patients who underwent surgical procedures of the tricuspid valve from 2004 until 2017 and lacked a pacemaker preoperatively were included in the study. In our cohort of 505 patients 54 required a pacemaker in the first 50 days after surgery. We calculated a 17.5% (95% confidence interval [CI], 13.5-21.3) risk of pacemaker implantation at 4 years postoperatively. Multivariate analysis identified preoperative active endocarditis (odds ratio 3.17; CI, 1.32-7.65; P = 0.010) and "inadequate pacemaker dependent rhythm" (defined as any intrinsic heart rate below 45 per minute requiring pacing) upon admission to the intensive care unit after surgery (odds ratio 5.924; CI, 2.82-12.44; P = 0.001) as predictors for pacemaker requirement in the first 50 days after surgery. Twenty-six pacemakers (48%) were implanted for atrioventricular block, 16 (30%) for sinus node dysfunction and 12 (22%) for atrial fibrillation. Kaplan-Meier analysis showed no difference in survival between the pacemaker and no pacemaker group. Surgery of the tricuspid valve has a high burden of postoperative pacemaker requirement. Preoperative active endocarditis and the initial postoperative rhythm are predictors. Understanding this allows for better decision-making regarding further medical/device therapy.

Prevalence of major complications and procedural mortality in 336 dogs undergoing interventional cardiology procedures in a single academic center

Overall complication rates associated with a wide range of diagnostic and therapeutic interventional cardiac procedures in a contemporary academic setting have not been reported. Consecutive interventional procedures performed for client-owned dogs were retrospectively analyzed to characterize procedural complications and mortality. Three hundred sixty-four procedures were performed on 336 dogs. Interventions included attempted or completed transvenous pacemaker (PM) implantation (n=134) with subsequent pacing system revision (n=8), pulmonic balloon valvuloplasty (BVP) (n=117) with a subset of patients undergoing an additional BVP (n=14), transarterial closure of left-to-right shunting patent ductus arteriosus (PDA) (n=66), diagnostic angiography and/or cardiovascular pressure measurement (n=9), transvenous temporary pacing (n=7), septal defect occlusion (n=5), heartworm extraction (n=3), and BVP catheter fragment retrieval (n=1). The prevalence of major perioperative and postoperative complications for all procedures was 5% and 6%, respectively, and the procedural mortality rate was 2%. The overall rate of major complications was 12% for the PM group, 11% for the BVP group, and 2% for the PDA occlusion group. Both PM implantation and BVP have higher rates of major complications overall compared with PDA occlusion (p=0.0151). The results of this study indicate that the prevalence of major complications and mortality associated with interventional cardiac procedures is low; however, significant differences exist in complication rates between procedures.

Abstract 17303: Permanent Cardiac Pacemaker Implant Improves Sleep Habit

Background: Permanent cardiac pacemaker is indicated in patients with symptomatic bradycardia. Its role in sleep disorder is unknown, however some patient report improvement in their sleep habit after permanent cardiac pacemaker implant. We examined the role of permanent cardiac pacemaker in relation to patients’ sleeping habits. Methods: Total of 174 patients who agreed to participate in the study were included (21 Implantable Cardioverter Defibrillator (ICD) and 153 pacemaker implants). The ICD group was used as the control group. Patients with bi-ventricular pacemaker implants for cardiac re-synchronization therapy were excluded from the study. Questionnaires about the sleep habit were evaluated before and after the device implant and analyzed using paired T test and Chi square test. Results: The indications for permanent pacemaker therapy were high grade AV block (33%), sick sinus syndrome (64%) and syncope (1%). Indications of ICD were primary or secondary sudden cardiac death prevention without history of known symptomatic bradycardia (100%). Mean Ventricular pacing was 40.39% (interquartile range: 97%) of the time in the pacemaker group. There were no baseline differences in sleep duration and quality of sleep in both the ICD and pacemaker group prior to device implant. Improved sleep habit (46% in pacemaker vs 23% in the ICD group, P=0.04) and better quality of sleep (44% in pacemaker vs 19% in ICD, P=0.01) were reported after device implant. The patients in pacemaker group reported much improvement in sleep duration (average by 30 minutes in Pacemaker vs 15 minutes in ICD, P=0.002). Conclusions: Patients who had permanent pacemaker implant for symptomatic bradycardia showed improved sleep quality and duration than the patients with ICD implant for primary or secondary sudden cardiac death prevention. Mechanisms of improved sleep habit in pacemaker group are unclear, but possibly associated with improved cardiac output with consistent heat rate during sleep from the pacemaker. Further large-scale studies are needed to validate this concept.

Effects of permanent cardiac pacemaker implantation on vascular endothelial function, blood coagulation and cardiac function in patients with bradycardia.

Changes in vascular endothelial function, blood coagulation and cardiac function indexes after the implantation of a permanent cardiac pacemaker in patients with bradycardia were investigated. A total of 53 healthy people and 117 patients with bradycardia in Jining First People's Hospital from January 2015 to August 2017 were selected. Factor VIII: coagulation (FVIII:C), von Willebr and factor (vWF), antithrombin activity (AT:A), D-dimmer (D-D), thrombomodulin (TM), tissue factor (TF), left ventricular ejection fraction (LVEF) and left ventricular end-systolic volume (LVESV) in the non-pacemaker group and the pacemaker group were significantly different from those in the control group (P<0.05), in which FVIII:C, vWF, D-D, TM, TF and LVESV were significantly higher than those in the control group, while LVEFs were significantly lower than that in the control group. After the implantation of a pacemaker, the FVIII:C, vWF, fibrinogen (FIB), D-D, TF and LVESV in patients were significantly higher than those before implantation (P<0.05), while the LVEF was significantly lower than that before implantation (P<0.05). In addition, in different pacemaker groups, there were no significant differences in blood coagulation and vascular endothelial indexes, but differences in cardiac function levels were obvious, in which LVEF in dual-chamber (DDD) pacemaker group was significantly higher than that in ventricular inhibited (VVI) pacemaker group, and LVESV in the former was significantly lower than that in the latter (P<0.05). Finally, here was no significant difference in the quality of life of patients implanted with different pacemakers (P>0.05), but the quality of life of patients in the DDD pacemaker group was better than that of patients in the VVI group. Therefore, implanting pacemakers in patients with bradycardia affects vascular endothelial function, blood coagulation, and cardiac function indexes in patients, and complications become less after the implantation of DDD pacemakers.

The Influence of Cardiac Pacemaker Programming Modes on Exercise Capacity.

The cardiac pacing mode influences the atrioventricular synchronicity and the response of the heart rate to physical exercise. The aim of this study was to compare the influence of the most common pacemaker programming modes on exercise capacity. Fifty-two pacemaker-wearing patients were clinically evaluated and submitted to an exercise stress test. Symptoms of heart failure were more frequently met in the single-chamber pacemaker group compared to the dual-chamber group. The parameters recorded during the exercise stress test were significantly better with the rate responsive function (RRF) activated. The effort time was higher by an average of 2.1 minutes and the exercise capacity was higher by 0.92 metabolic equivalents. Dual-chamber pacing is superior to single-chamber (ventricular) pacing and the activation of the RRF in single-chamber pacemakers has similar impact on exercise capacity as the preservation of atrioventricular synchronicity by dual-chamber pacemakers.

Access to magnetic resonance imaging of patients with magnetic resonance-conditional pacemaker and implantable cardioverter-defibrillator systems: results from the Really ProMRI study.

The Really ProMRI study evaluates magnetic resonance imaging (MRI) access for patients with cardiac implantable electronic devices (CIEDs) as well as the performance of magnetic resonance (MR)-conditional leads when undergoing MRI. Patients either with an MR-conditional pacemaker or implantable defibrillator (ICD) system or with at least a component (device or one or more leads) from an MR-conditional system, were asked to fill in a questionnaire when they were referred to a MR scan. The rate of prescription, denial, or execution of MR examinations was evaluated in a 1-year follow-up visit. In total, 555 patients [median age (interquartile range) 72.2 (62.2-78.6); 72% male] were enrolled, 49% (270) with a pacemaker, 51% (285) with an ICD system. Five-hundred and ten patients completed the follow-up period. A total of 37 MRI referrals were reported in 35 patients, with a consequent event rate of 7.0/100 patient-years (CI, 4.9-9.7). Fourteen were denied, while 23 [66%; (CI, 48-81%)] were performed. The number of patients with MR referrals was not statistically different between pacemaker and ICD groups (21 vs. 14; P = 0.178). The rate of scans performed was higher in the pacemaker subjects (19/23 vs. 4/14, P = 0.003), while it was similar between patients with or without a complete MR-conditional system (19/30 vs. 4/7, P = 0.606). In this study, we reported a 7.0/100 patient-year's event rate of MR prescriptions in CIED patients. Many examinations were denied, despite MR-conditional systems, especially in ICD patients. Regulatory and cultural changes are needed to allow wider access to MR imaging in CIED patients with MR-conditional systems.

A balance of outward and linear inward ionic currents is required for generation of slow-wave oscillations.

Regenerative inward currents help produce slow oscillations through a negative-slope conductance region of their current-voltage relationship that is well approximated by a linear negative conductance. We used dynamic-clamp injections of a linear current with such conductance, INL, to explore why some neurons can generate intrinsic slow oscillations whereas others cannot. We addressed this question in synaptically isolated neurons of the crab Cancer borealis after blocking action potentials. The pyloric network consists of a distinct pacemaker and follower neurons, all of which express the same complement of ionic currents. When the pyloric dilator (PD) neuron, a member of the pacemaker group, was injected with INL with dynamic clamp, it consistently produced slow oscillations. In contrast, all follower neurons failed to oscillate with INL To understand these distinct behaviors, we compared outward current levels of PD with those of follower lateral pyloric (LP) and ventral pyloric (VD) neurons. We found that LP and VD neurons had significantly larger high-threshold potassium currents (IHTK) than PD and LP had lower-transient potassium current (IA). Reducing IHTK pharmacologically enabled both LP and VD neurons to produce INL-induced oscillations, whereas modifying IA levels did not affect INL-induced oscillations. Using phase-plane and bifurcation analysis of a simplified model cell, we demonstrate that large levels of IHTK can block INL-induced oscillatory activity whereas generation of oscillations is almost independent of IA levels. These results demonstrate the general importance of a balance between inward pacemaking currents and high-threshold K+ current levels in determining slow oscillatory activity.NEW & NOTEWORTHY Pacemaker neuron-generated rhythmic activity requires the activation of at least one inward and one outward current. We have previously shown that the inward current can be a linear current (with negative conductance). Using this simple mechanism, here we demonstrate that the inward current conductance must be in relative balance with the outward current conductances to generate oscillatory activity. Surprisingly, an excess of outward conductances completely precludes the possibility of achieving such a balance.

Follow-up of troponin I concentration in dogs with atrioventricular block and dual-chamber pacing in a case-matched study

Increased cardiac troponin I (cTnI) concentration has been reported in dogs with atrioventricular (AV) block before and shortly following pacemaker implantation. The role of AV dyssynchrony, age, or concurrent cardiac disease on cTnI concentration remains unknown. To investigate change in cTnI concentration following dual-chamber pacemaker implantation on short- and long-term follow-up and to compare cTnI values to a case-matched control group. Thirty-eight client-owned dogs with permanent AV block and 38 matched control dogs. Retrospective review of medical records. Pacemaker group consisted of dogs with AV block and dual-chamber pacing. Control group matched the study population in age and cardiac disease. cTnI was compared between pacemaker and control group on short- and long-term follow-up. Different lead types and influence of arrhythmia on cTnI were tested. cTnI was high at presentation (median 0.66ng/ml; range 0.03-18.6) and showed a significant reduction over time after pacemaker implantation (p<0.0001). Median cTnI values were significantly different between pacemaker and control group on short-term (p=0.0004; 0.11ng/ml, range 0.03-1.36 versus 0.06ng/ml, range 0.03-0.46), but not on long-term follow-up (p=0.0547; 0.14ng/ml, range 0.03-0.73 versus 0.07ng/ml, range 0.03-0.46). Lead type and severity of arrhythmia did not show a significant correlation to cTnI concentration. On long-term follow-up, cTnI remained mildly elevated in some of the pacemaker dogsbut was not significantly different to the matched control group.