Ventricular Stimulation Research Articles

Myocardial biomechanics, intracardiac hemodynamics and endothelial function in patients before and after various types of pacemakers implantation

This review presents 31 sources from 1995 to 2019. Atrioventricular blockades (AVB) 2-3 degrees occupy a special place among the causes of death from cardiovascular disease. The above AVB lead to a significant slowing of the heart rate and predispose to the development and progression of heart failure (HF) and the occurrence of acute hypoxia of the brain and attacks Morgagni-Adams-Stokes. The main method of treatment of hemodynamically significant AB-conduction disorders is electrocardiostimulation (ES), which is the basic method of treatment. A single chamber pacemaker is the most often implanted with using isolated ventricular stimulation in clinical practice in the Russian Federation. Implantation of a dual chamber pacemaker is less frequent. This type of stimulation allows to maintain atrioventricular synchronization constantly. Stimulation of the apex of the right ventricle leads to a decrease in left ventricle (LV) function and structural changes that are a consequence of the occurrence of electric and mechanical dyssynchrony of the myocardium. There is a large number of works devoted to the comparison of different methods of ES leading to the conclusion that a powerful alternative to the stimulation of the apex of the right ventricle can be a dual ventricular stimulation. It is noted that implantation of single-and dual-chamber pacemaker with fixation of the electrode in the region of the right ventricle apex leads to the fact that both modes of stimulation can not cancel the electrical and anatomical remodeling of the myocardium of left atrium and LV. It may be necessary to use a more physiological site of stimulation with using optimal AB-delay to minimize the frequency of ventricular stimulation. Endothelium plays an important and independent role in the development of cardiovascular diseases. The effect of AB conduction impairment on endothelial function (EF) has not been described to date. There were few studies which are discussed the influence of constant pacemaker on endothelial function in patients with AVB 2-3 degrees in recent years. It should be noted that the studies were conducted on a small sample of patients and had a different design.

Action Potential Triangulation Explains Acute Proarrhythmic Effect of Aliskiren in a Whole-Heart Model of Atrial Fibrillation.

Recent experimental studies showed a protective effect of the renin inhibitor aliskiren regarding atrial structural remodeling. Purpose of this study was to assess acute electrophysiologic effects of aliskiren in a whole-heart model of atrial fibrillation (AF) and to investigate its impact on the ventricle. Twelve rabbit hearts were excised, retrogradely perfused, and paced at different cycle lengths. To enhance atrial vulnerability, a combination of acetylcholine (ACh) and isoproterenol (Iso) was infused and significantly reduced atrial action potential duration (aAPD90) and atrial effective refractory period (aERP). Additional infusion of aliskiren prolonged aAPD90 but did not alter aERP. A triangulation of action potential with ACh/Iso and a further triangulation after treatment with aliskiren were noted. Vulnerability to AF was tested by employing trains of burst pacing. Administration of ACh/Iso provoked more episodes of AF (baseline: 26 episodes, Iso/Ach: 48 episodes). Additional treatment with aliskiren induced AF significantly more often (108 episodes). Another nine hearts were perfused with aliskiren to examine its ventricular effects. Infusion with aliskiren abbreviated ventricular APD90 and ERP. Utilizing programmed ventricular stimulation, a trend towards more ventricular arrhythmias in aliskiren-treated hearts was observed. Though aliskiren did not reduce aAPD90 or aERP, acute treatment with aliskiren promoted AF. Triangulation of atrial action potentials, which is an established risk factor for ventricular proarrhythmia, may contribute to the increased atrial vulnerability. This effect may interfere with its recently demonstrated beneficial properties in atrial remodeling. Of note, aliskiren might have a proarrhythmic effect on the ventricular level.

Brugada syndrome in a young patient with type 1 myotonic dystrophy requiring an implantable cardioverter defibrillator for primary prevention: a case report.

Background Cardiac electrical disturbances represent the most frequent cardiac manifestations of myotonic dystrophy Type 1 (MD1). Limited data suggest that the prevalence of Brugada syndrome in MD1 may be increased compared to the general population.Case summary We report a case of a 22-year-old asymptomatic man with repolarization abnormalities in leads V1–V3 suggestive of Type III Brugada pattern. The patient had a family history of MD and incidents of sudden death in relatives. Drug-induced Brugada Type 1 syndrome was revealed after procainamide challenge. A ventricular stimulation study was positive since a polymorphic ventricular tachycardia was induced after two extrastimuli. The patient underwent implantation of a single chamber cardiac defibrillator (ICD). Eight months after the procedure he suffered an appropriate ICD shock due to rapid polymorphic ventricular tachycardia.Discussion Brugada syndrome is linked with MD1. Potential life-threatening arrhythmias may develop in the adult life of MD1 patients. Electrocardiographic surveillance and tailored invasive treatment with ICDs can prevent sudden cardiac death in this setting.

Noninvasive Programmed VentricularStimulation-Guided Management Following Ventricular Tachycardia Ablation.

This study sought to determine the impact of repeat catheter ablation (CA) prior to hospital discharge based on inducibility of clinical ventricular tachycardia (VT) during noninvasive programmed ventricular stimulation (NIPS). Inducibility of clinical VT during NIPS performed several days after CA identifies patients at high risk of recurrence. The impact of NIPS-guided repeat CA has not been reported. Consecutive patients with structural heart disease undergoing CA of VT followed by NIPS were studied. Clinical VT was defined by comparison with 12-lead electrocardiograms and stored implantable cardioverter-defibrillator electrograms from spontaneous VT episodes. Among those with inducible clinical VT at NIPS, VT-free survival was compared between those in whom ablation was repeated (group 1) versus those in whom ablation was not repeated (group 2) prior to hospital discharge. Among 469 patients (64 ± 12 years of age; 85% males; 60% ischemic), 216 patients (46%) underwent NIPS 3 days (interquartile range: 2 to 4 days) after CA. Clinical VT was induced in 45 patients (21%). Among those 45, CA was repeated in 11patients (24%). There were no significant differences in baseline clinical or index CA characteristics between groups1and 2. Over a median 36-month follow-up, only 1 patient (9%) in group 1 experienced VT recurrence compared to 24patients (71%) in group 2 (p< 0.01). In univariate Cox regression, repeat CA guided by NIPS (hazard ratio: 0.07; 95%confidence interval: 0.01 to 0.58; p= 0.01) was the only predictor of VT-free survival. In patients with inducible clinical VT during post-ablation NIPS, repeat CA was associated with significantly lower risk of subsequent recurrence.

Ventricular Stimulation as Predictor of Hypovolemia After Cardiac Surgery

Ventricular Stimulation as Predictor of Hypovolemia After Cardiac Surgery

Bipolar active fixation left ventricular lead or quadripolar passive fixation lead? An Italian multicenter experience.

About one-third of patients receiving cardiac resynchronization therapy (CRT) are not responders, due to either patient selection or technical issues. Left ventricular quadripolar passive fixation leads (QPL) and bipolar active fixation (BAF) leads have been designed to ensure a targeted left ventricular stimulation area, minimizing lead dislodgments and phrenic nerve stimulation (PNS). The aim was to compare real-world safety and efficacy of BAF (Attain Stability, Medtronic Plc.) and QPL (Attain Performa, Medtronic Plc.). We performed a retrospective analysis examining procedural and follow-up data of 261 BAF and 124 QPL (programmed to single-site left ventricular pacing), included in the ClinicalService project from 16 Italian hospitals. At median follow-up of 12 months, no difference in left ventricular pacing threshold was recorded between BAF and QPL (1.3 ± 0.9 V @0.4 ms vs. 1.3 ± 1.0 V @0.4 ms; P = 0.749). Total left ventricular lead dislodgement rate was 1.43/100 patient-years in BAF vs. 2.9/100 patient-years in QPL (P = 0.583). However, no dislodgements occurred among BAF after hospital discharge. Events requiring repeated surgery or permanently turning CRT off occurred in 0.8% of BAF, as compared with 4.0% of QPL (P = 0.025). There was no difference between groups in the echo CRT responders' rate (70% of BAF and 66% of QPL; P = 0.589) or in the annual rate of heart failure hospitalization (P = 0.513). BAF resulted in noninferior clinical outcome and CRT responders' rate in comparison to QPL. Moreover, BAF ensured more precise and stable placement in cardiac veins, with comparable electrical performance and less than 1% patients with unsolved PNS.

The Pacemaker and Implantable Cardioverter-Defibrillator Registry of the Italian Association of Arrhythmology and Cardiac Pacing - Annual report 2017

The pacemaker (PM) and implantable cardioverter-defibrillator (ICD) Registry of the Italian Association of Arrhythmology and Cardiac Pacing (AIAC) monitors the main epidemiological data in real-world practice. The survey for the 2017 activity collects information about demographics, clinical characteristics, main indications for PM/ICD therapy and device types from the Italian collaborating centers. The Registry collects prospectively national PM and ICD implantation activity on the basis of European cards. PM Registry: data about 23 457 PM implantations were collected (19 378 first implant and 4079 replacements). The number of collaborating centers was 185. Median age of treated patients was 81 years (75 quartile I; 86 quartile III). ECG indications included atrioventricular conduction disorders in 37.1% of first PM implants, sick sinus syndrome in 19.5%, atrial fibrillation plus bradycardia in 13.2%, other in 30.2%. Among atrioventricular conduction defects, third-degree atrioventricular block was the most common type (21.0% of first implants). Use of single-chamber PMs was reported in 25.6% of first implants, of dual-chamber PMs in 66.7%, of PMs with cardiac resynchronization therapy (CRT) in 1.4%, and of single lead atrial-synchronized ventricular stimulation (VDD/R PMs) in 6.3%. ICD Registry: data about 19 023 ICD implantations were collected (13 898 first implants and 5125 replacements). The number of collaborating centers was 437. Median age of treated patients was 71 years (63 quartile I; 78 quartile III). Primary prevention indication was reported in 81.8% of first implants, secondary prevention in 18.2% (cardiac arrest in 6.4%). A single-chamber ICD was used in 27.0% of first implants, dual-chamber in 33.6% and biventricular in 39.3%. The PM and ICD Registry appears fundamental for monitoring PM and ICD utilization on a large national scale with rigorous examination of demographics and clinical indications. The PM Registry showed stable electrocardiographic and symptom indications, with an important prevalence of dual-chamber pacing. The use of CRT-PM regards a very limited number of patients. The ICD Registry documented a large use of prophylactic and biventricular ICD, reflecting a favorable adherence to trials and guidelines in clinical practice. In order to increase and optimize the cooperation of Italian implanting centers, online data entry (http://www.aiac.it/riprid) should be adopted at large scale.

The Left and Right Ventricles Respond Differently to Variation of Pacing Delays in Cardiac Resynchronization Therapy: A Combined Experimental- Computational Approach.

Introduction: Timing of atrial, right (RV), and left ventricular (LV) stimulation in cardiac resynchronization therapy (CRT) is known to affect electrical activation and pump function of the LV. In this study, we used computer simulations, with input from animal experiments, to investigate the effect of varying pacing delays on both LV and RV electrical dyssynchrony and contractile function.Methods: A pacing protocol was performed in dogs with atrioventricular block (N = 6), using 100 different combinations of atrial (A)-LV and A-RV pacing delays. Regional LV and RV electrical activation times were measured using 112 electrodes and LV and RV pressures were measured with catheter-tip micromanometers. Contractile response to a pacing delay was defined as relative change of the maximum rate of LV and RV pressure rise (dP/dtmax) compared to RV pacing with an A-RV delay of 125 ms. The pacing protocol was simulated in the CircAdapt model of cardiovascular system dynamics, using the experimentally acquired electrical mapping data as input.Results: Ventricular electrical activation changed with changes in the amount of LV or RV pre-excitation. The resulting changes in dP/dtmax differed markedly between the LV and RV. Pacing the LV 10–50 ms before the RV led to the largest increases in LV dP/dtmax. In contrast, RV dP/dtmax was highest with RV pre-excitation and decreased up to 33% with LV pre-excitation. These opposite patterns of changes in RV and LV dP/dtmax were reproduced by the simulations. The simulations extended these observations by showing that changes in steady-state biventricular cardiac output differed from changes in both LV and RV dP/dtmax. The model allowed to explain the discrepant changes in dP/dtmax and cardiac output by coupling between atria and ventricles as well as between the ventricles.Conclusion: The LV and the RV respond in a opposite manner to variation in the amount of LV or RV pre-excitation. Computer simulations capture LV and RV behavior during pacing delay variation and may be used in the design of new CRT optimization studies.

Three-dimensional cardiac fibre disorganization as a novel parameter for ventricular arrhythmia stratification after myocardial infarction.

AimsMyocardial infarction (MI) alters cardiac fibre organization with unknown consequences on ventricular arrhythmia. We used diffusion tensor imaging (DTI) of three-dimensional (3D) cardiac fibres and scar reconstructions to identify the main parameters associated with ventricular arrhythmia inducibility and ventricular tachycardia (VT) features after MI.Methods and resultsTwelve pigs with established MI and three controls underwent invasive electrophysiological characterization of ventricular arrhythmia inducibility and VT features. Animal-specific 3D scar and myocardial fibre distribution were obtained from ex vivo high-resolution contrast-enhanced T1 mapping and DTI sequences. Diffusion tensor imaging-derived parameters significantly different between healthy and scarring myocardium, scar volumes, and left ventricular ejection fraction (LVEF) were included for arrhythmia risk stratification and correlation analyses with VT features. Ventricular fibrillation (VF) was the only inducible arrhythmia in 4 out of 12 infarcted pigs and all controls. Ventricular tachycardia was also inducible in the remaining eight pigs during programmed ventricular stimulation. A DTI-based 3D fibre disorganization index (FDI) showed higher disorganization within dense scar regions of VF-only inducible pigs compared with VT inducible animals (FDI: 0.36; 0.36–0.37 vs. 0.32; 0.26–0.33, respectively, P = 0.0485). Ventricular fibrillation induction required lower programmed stimulation aggressiveness in VF-only inducible pigs than VT inducible and control animals. Neither LVEF nor scar volumes differentiated between VF and VT inducible animals. Re-entrant VT circuits were localized within areas of highly disorganized fibres. Moreover, the FDI within heterogeneous scar regions was associated with the median VT cycle length per animal (R2 = 0.5320).ConclusionThe amount of scar-related cardiac fibre disorganization in DTI sequences is a promising approach for ventricular arrhythmia stratification after MI.

Electroanatomic and Pathologic Right Ventricular Outflow Tract Abnormalities in Patients With Brugada Syndrome

BackgroundThe prevalence and significance of structural abnormalities in Brugada syndrome (BrS) are still largely debated. ObjectivesThe authors investigated the relationship between genetic background, electroanatomic abnormalities, and pathologic substrate in BrS. MethodsThey performed 3-dimensional electroanatomic unipolar and bipolar mapping in 30 patients with BrS. Twenty patients underwent 3-dimensional electroanatomic unipolar and bipolar mapping–guided right ventricular outflow tract (RVOT) endomyocardial biopsy. Programmed ventricular stimulation and genetic analysis were performed in all patients. ResultsLow-voltage areas (LVAs) were observed at unipolar map in 93% of patients and at bipolar map in 50% of cases. Unipolar LVAs were always larger than bipolar LVAs, were always colocalized, and in all cases included RVOT. Disease-causing mutations were detected in 10 (33%) patients. Programmed ventricular stimulation was positive in 16 cases (53%). In 75% of patients, RVOT histology showed pathologic findings with myocardial inflammation in 80% of them. Among patients with abnormal bipolar map submitted to endomyocardial biopsy, 9 (81%) showed evidence of myocardial inflammation. Conversely, bipolar map was abnormal in 83% of patients with myocardial inflammation. Myocardial inflammation was also more prevalent among inducible patients (83% vs. 25% in noninducible; p = 0.032). ConclusionsBrS is characterized by electroanatomical and structural abnormalities localized to RVOT with a gradient of the pathologic substrate from epicardium to endocardium possibly driven by myocardial inflammation. These findings reclassify BrS as a combination of structural and electrical defects opening the way to new risk stratification and therapeutic strategies.

Abstract 16677: Protein Kinase G I Alpha Attenuates Inducible Ventricular Tachycardia and QRS/T Wave Alternans in the Type II Diabetic Heart

Introduction: Diabetes increases ventricular tachycardia (VT) and sudden cardiac death risk in humans. We previously found the type I diabetic (DMI) heart displays: reduced responsiveness to parasympathetic stimulation; increased QRS/T Wave alternans (marker of proarrhythmic calcium dyshomeostasis); and hyperactive GSK3beta. Cardiac parasympathetic stimulation promotes production of intracellular cyclic GMP (cGMP). The effects of cGMP and its downstream effector PKG, on these indices of VT in type II diabetes (DMII) remain poorly understood. Hypothesis: PKGIa modulates inducibility of VT and QRS/TWA in the DMII heart and mediates the cGMP effect on VT through inhibition of myocardial GSK3beta. Methods: Using an established protocol of programmed ventricular stimulation we measured: VT incidence, duration, and QRS/T Wave alternans. We studied the following mice: wild type; Db/Db model of DMII; high fat high sucrose (HFHS) model of insulin resistance; and the PKGIa leucine zipper mutant (LZM) mouse, which has no DM but has PKGIa disrupting mutations. Mice were treated with or without the cGMP-augmenting phosphodiesterase inhibitor sildenafil 10 mg/kg, or the GSK3b inhibitor TWS119 20 mg/kg. Results: LVs of HFHS mice displayed 30 ± 8% reduction of cGMP compared with control (p&lt;0.05, n=3 per group), while myocardial cGMP in LZM mice did not differ from control. In failing LVs from humans, there was also a 46% reduction in myocardial cGMP in DM compared with nondiabetic (p= .058, n=3 per group). Db/Db and HFHS mice had increased inducible VT (0.25 +/- 0.1 s in Db/Db, 2.2 +/- 1 s HFHS, vs 0 s in WT control, p &lt;0.05), as well as TWA. Treatment with sildenafil reduced VT incidence, duration, and TWA in Db/Db and HFHS mice. LZM mice also had increased VT duration and TWA incidence (0 of 4 in WT vs 5 of 6 in LZM, p&lt;0.05). Inhibition of GSK3β rescued inducibility of VT in Db/Db, HFHS, and in LZM mice. Conclusions: These findings support that in the DMII heart reduced cGMP promotes VT, whereas pharmacological augmentation of cGMP inhibits VT. Inducible VT and TWA in the PKG LZM mouse provides direct support that PKGIa opposes VT in the DMII heart. These support that cGMP activation of PKG inhibits GSK3beta, leading to reduced incidence of inducible VT.

Abstract 16707: Human Embryonic Stem Cell-Derived Cardiomyocytes Are Safe and Improve Infarct Size and Cardiac Function in a Porcine Model of Myocardial Infarction

Introduction: Stem cell therapy is an emerging means of stimulating cardiac repair after myocardial infarction (MI). Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) are a novel therapeutic option, with the potential for cell derived remuscularization. This study assessed the safety and efficacy of these cells, is the first to test these cells in a porcine model of MI, and used electrophysiologic (EPS) testing to evaluate potential arrhythmogenicity. Methods: Yucatan swine underwent a left anterior descending coronary artery ischemia/reperfusion protocol to form an MI. Four weeks later, either placebo (n=3) or 3 x 10 8 hESC-CMs were delivered via transendocardial stem cell injection (TESI) (n=4). All animals received immunosuppression for 2 weeks following TESI. Three uninfarcted animals received cells. Cardiac function and LV chamber volumes were measured using pressure volume catheterization and cardiac MRI at 4, 8 and 12 weeks post-TESI. Inducibility of ventricular tachycardia (VT) was tested at 4 and 12 weeks post-TESI by programmed ventricular stimulation via a catheter in the RV apex. Histology of heart tissue and organs was evaluated. Results: Twelve weeks post-TESI, scar size (scar mass as a % of total LV mass) was reduced in the cell treated group by -2.33±0.03% (p=0.034), a 12.69±1.87% reduction from pre-TESI. Scar size remained constant in the placebo group. The rise in end diastolic volume at 12 weeks in the placebo group (15.6±7.35 mL; p=0.032) was attenuated in the cell treated group (10.39±6.36mL; p=0.17). By 12 weeks post-TESI, Ees (slope of ESPVR) increased by 0.51±0.15 mmHg/mL (p=0.045) and in the cell treated group but was unchanged in placebo (-0.09±0.85 mmHg/mL; p= 0.92). Following TESI, only 1 animal from each group had inducible VT. No animals had spontaneous VT as measured by an implantable loop recorder. Cardiac function and structure of uninfarcted animals did not change over the study, and none of these animals had inducible VT. Histology did not reveal ectopic tissue formation or signs of rejection. Conclusion: TESI of hESC in a porcine MI model is safe, does not increase the risk of either spontaneous or inducible arrhythmias compared to placebo, reduces scar size and remodeling and improves cardiac contractility as measured by Ees. Translation to clinical studies is warranted.

Prognostic value of noninvasive programmed stimulation in patients with implantable cardioverter defibrillator.

Implantable cardioverter defibrillator (ICD) offers an opportunity to examine vulnerability to ventricular tachycardia (VT) or ventricular fibrillation (VF) by performing noninvasive programmed ventricular stimulation (NIPS). Whether NIPS can predict VT/VF recurrences has not yet been established. To examine the predictive value of NIPS for identification of patients with VT/VF recurrences. The study group consisted of consecutive 105 ICD recipients included in the prospective NIPS-ICD study (ClinicalTrials ID: NCT02373306) (88 males, age 65±11years). The patientsunderwent NIPS using the protocol up to three premature extrastimuli at 600-500- and 400-ms drive cycle lengths. The endpoint of NIPS was induction of sustained VT or VF or completion of the protocol. VT/VF was induced in 29 (27.6%) patients. During a 12-month follow-up NIPS-inducible patients had significantly more frequently appropriate ICD therapy than noninducible patients (17%vs 4%, P=0.023). NIPS-induced VT/VF had a sensitivity of 63%, specificity of 75%, positive predictive value of 17%, and negative predictive value of 96% for identification of patients with future VT/VF. Apart from NIPS, age ≥65years, QRS duration, treatment with angiotensin-converting enzyme, history of coronary artery bypass grafting, history of VT/VF prior to NIPS, and prior appropriate ICD therapy were also associated with VT/VF recurrences. Multivariate analysis showed that, together with QRS duration, NIPS result was an independent predictor of future VT/VF. Predictive value of NIPS was significantly higher in ischemic than nonischemic patients. NIPS result is associated with future VT/VF. Noninducibility at NIPS identifies those patients with high accuracy who will have uneventful follow-up.

Direct His bundle pacing in routine clinical practice

Direct His bundle pacing has recently attracted interest as a more physiological alternative to right ventricular or biventricular stimulation. The advent of new tools has facilitated the implantation procedure. This report relates our initial experience with this technique in our first 50 patients.

Subcutaneous implantable cardioverter-defibrillator : Current status and perspectives

The use of transvenous implantable cardioverter-defibrillators (ICD) for the prevention of sudden cardiac death has been proven in numerous randomized trials. By using atotally subcutaneous ICD (S-ICD) system, it is expected to ensure appropriate protection while avoiding long-term complications associated with transvenous leads, such as systemic infection and electrode dysfunction. Meanwhile, the safety and effectiveness of the S‑ICD has been substantiated by results of large registry studies. Based on the missing option for ventricular stimulation, corresponding recommendations have been integrated into current guidelines for certain patient populations. In the future, the issue of inadequate shocks caused by oversensing may be solved using advanced screening tools and new detection algorithms. Furthermore, acombination of subcutaneous ICD and LCP (leadless cardiac pacer) seems realistic to enable antibradycardia and antitachycardia ventricular pacing.

Cardiac pacing in cardioinhibitory syncope in children.

Reflex vasovagal-or cardioinhibitory syncope is known to be a major cause of recurrent syncope in children. The mechanism of vasovagal syncope (VVS) is an interaction between a vagally mediated bradycardia or asystole and a more or less manifest vasodilatory component. Although pacing is not advisable as a standard approach in patients with VVS, it remains a treatment option of last resort in exceptionally severe cases, or patients with contraindication or refractoriness to drug therapy and life style changes. To effectively avoid VVS in these patients, the pacemaker has to both prevent bradycardia and to compensate for the vasodilatory component. Therefore, this study aimed to evaluate a simple pacemaker setting (VVI pacing with hysteresis) with the potential to prevent VVS in affected children. Clinical data of patients, who were presented to the Department for Pediatric Cardiology, Heart Center Leipzig, in the period of 2001-2017 for cardiac pacemaker implantation for cardioinhibitory syncope or pallid breath-holding spells, were collected retrospectively. Eleven pediatric patients, median age 2.7 (0.8-17) years, were included. Pacemaker settings are depicted. In 10 out of 11 patients, an entire abolishment of syncope could be achieved (P=.002). The presented VVI pacing with hysteresis seems to be a promising pacemaker setting in pediatric patients with cardioinhibitory syncope who need a pacemaker. Unnecessary ventricular stimulation is effectively avoided, while cardiac output is preserved during cardioinhibition, by providing a sufficient paced heart rate, compensating for the often present vasodilatory component.

Systematic Review for the 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society.

Although large randomized clinical trials have found that primary prevention use of an implantable cardioverter-defibrillator (ICD) improves survival in patients with cardiomyopathy and heart failure symptoms, patients who receive ICDs in practice are often older and have more comorbidities than patients who were enrolled in the clinical trials. In addition, there is a debate among clinicians on the usefulness of electrophysiological study for risk stratification of asymptomatic patients with Brugada syndrome. Our analysis has 2 objectives. First, to evaluate whether ventricular arrhythmias (VAs) induced with programmed electrostimulation in asymptomatic patients with Brugada syndrome identify a higher risk group that may require additional testing or therapies. Second, to evaluate whether implantation of an ICD is associated with a clinical benefit in older patients and patients with comorbidities who would otherwise benefit on the basis of left ventricular ejection fraction and heart failure symptoms. Traditional statistical approaches were used to address 1) whether programmed ventricular stimulation identifies a higher-risk group in asymptomatic patients with Brugada syndrome and 2) whether ICD implantation for primary prevention is associated with improved outcomes in older patients (>75 years of age) and patients with significant comorbidities who would otherwise meet criteria for ICD implantation on the basis of symptoms or left ventricular function. Evidence from 6 studies of 1138 asymptomatic patients were identified. Brugada syndrome with inducible VA on electrophysiological study was identified in 390 (34.3%) patients. To minimize patient overlap, the primary analysis used 5 of the 6 studies and found an odds ratio of 2.3 (95% CI: 0.63-8.66; P=0.2) for major arrhythmic events (sustained VAs, sudden cardiac death, or appropriate ICD therapy) in asymptomatic patients with Brugada syndrome and inducible VA on electrophysiological study versus those without inducible VA. Ten studies were reviewed that evaluated ICD use in older patients and 4 studies that evaluated unique patient populations were identified. In our analysis, ICD implantation was associated with improved survival (overall hazard ratio: 0.75; 95% confidence interval: 0.67-0.83; P<0.001). Ten studies were identified that evaluated ICD use in patients with various comorbidities including renal disease, chronic obstructive pulmonary disease, atrial fibrillation, heart disease, and others. A random effects model demonstrated that ICD use was associated with reduced all-cause mortality (overall hazard ratio: 0.72; 95% confidence interval: 0.65-0.79; P<0.0001), and a second "minimal overlap" analysis also found that ICD use was associated with reduced all-cause mortality (overall hazard ratio: 0.71; 95% confidence interval: 0.61-0.82; P<0.0001). In 5 studies that included data on renal dysfunction, ICD implantation was associated with reduced all-cause mortality (overall hazard ratio: 0.71; 95% confidence interval: 0.60-0.85; P<0.001).

EFFICACY OF CATHETER ABLATION FOR PERSISTENT ATRIAL FIBRILLATION IN PATIENTS WITH DIABETES MELLITUS PRESENT WITH TACHY-BRADY SYNDROME

Aim. To estimate the efficacy of catheter ablation in patients with type 2 diabetes mellitus (T2D) present with atrial fibrillation and sick sinus syndrome (SSS) undergoing permanent pacemaker implantation.Methods. 56 patients (34 females) with persistent AF and SSS were enrolled in the study. The mean age of patients was 67.7±10.7 years. Dual chamber cardiac pacemaker with remote monitoring function were implanted in all patients. All the patients were assigned to two groups: Group 1 comprised 31 patients aged 67.3±9.6 years, and Group 2 comprised 25 patients aged 72.6±9.9 years, including 22 (39.2%) diabetic patients. 2-3 days after pacemaker implantation, group 1 patients underwent intracardiac electrophysiology study and RFA of the pulmonary vein ostia, mitral isthmus and the left atrial posterior wall. Group 2 patients received antiarrhythmic drug therapy. Results. 3 patients (9%) in Group 1 had recurrent AF within the 6-month follow-up. The efficacy of the RFA for AF was 55% (n = 17) 1 year after the indexed hospitalization. 8 patients had short paroxysmal attacks which gradually lessened and stopped after. 5 patients (21%) in Group 2 did not have any AF paroxysms within the 1-year follow-up (Х2 = 5.52, р = 0.02). All these patients received amiodarone as antiarrhythmic drug therapy, whereas the others had paroxysmal attacks. Frequent attacks in 10 patients (40%) led to a change in antiarrhythmic drug use. Hospital readmission rates for AF were 16% and 52%, respectively (Х2 = 4.15, р = 0.04). The impact of atrial and ventricular stimulation on the development of recurrent AF was statistically insignificant (atrial stimulation – X2 = 0.01, cc = 1, p = 0.90; ventricular stimulation – X2 = 0.15, cc = 1, p = 0.69). None paroxysmal attacks were recorded in 10 diabetic patients (45%) after the RFA within the 1-year follow-up.Conclusion. Catheter ablation for persistent AF and SSS treated with permanent pacemakers is highly effective and safe method. In addition, it is superior to pharmacological approach. The presence of T2D likely did not significantly affect the efficacy of RFA for persistent form of AF.

Novel approach to discriminate left bundle branch block from nonspecific intraventricular conduction delay using pacing-induced functional left bundle branch block

Left bundle branch block (LBBB) has a predictive value for response to cardiac resynchronization therapy as reported by Zareba et al. (Circulation 123(10):1061-1072, 2011). However, based on ECG criteria, the discrimination between complete LBBB and nonspecific intraventricular conduction delay is challenging. We tested the hypothesis that discrimination can be performed using standard electrophysiological catheters and a simple stimulation protocol. Fifty-nine patients were analyzed retrospectively. Patients were divided into groups of narrow QRS (n = 20), wide QRS of right bundle branch block (RBBB) morphology (n = 14), and wide QRS of LBBB morphology (n = 25). Using a diagnostic catheter placed in the coronary sinus, left ventricular activation was assessed during intrinsic conduction as well as during right ventricular (RV) stimulation. In patients with narrow QRS and RBBB, the Q-LV/QRS ratio was 0.43 ± 0.013 (n = 20) and 0.41 ± 0.026 (n = 14), respectively. In patients with LBBB morphology, the Q-LV/QRS split up into a group of patients with normal (0.43 ± 0.022, n = 7) and a group with delayed left ventricular activation (0.75 ± 0.016, n = 18). By direct comparison of the Q-LV/QRS ratio during intrinsic conduction with the Q-LV/QRS ratio during RV pacing leading to a functional LBBB, a clear distinction between a group of "true LBBB" and another group of "apparent LBBB"/nonspecific intraventricular conduction delay (NICD) could be generated. We present a novel and practical method that might facilitate discrimination between patients with apparent LBBB and true LBBB by comparing Q-LV/QRS ratios during intrinsic activation and during RV stimulation. Although this method can already be directly applied, validation by 3D electrical mapping and prospective correlation to cardiac resynchronization therapy (CRT) response will be required for further translation into clinical practice.

Multipoint pacing-more CRT or awaste of battery power?

Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with broad QRS complex ≥130 ms and heart failure with reduced ejection fraction despite optimal guideline-directed medical therapy. However, approximately 30% of the patients implanted with aCRT system do not show clinical benefit. Reasons for nonresponse are complex and some aspects can be addressed during follow-up. Based on quadripolar lead technology, multipoint pacing (MPP) allows left ventricular stimulation at two different sites along the lead. In particular, in scarred and fibrotic ventricular myocardium stimulation at two different sites may overcome conduction barriers and lead to homogeneous ventricular depolarization. Especially for patients that do not respond to conventional CRT, activation of MPP may present an option to increase clinical response. On the other hand, MPP may significantly decrease battery longevity.This review offers an overview of the current knowledge and data on MPP balancing the potential clinical benefit and the possible disadvantages of this therapy.