Induced and spontaneous heart rate turbulence in mice: influence of coupling interval.

AIMS: Heart rate turbulence (HRT) is a prognostic parameter for risk stratification in patients suffering from coronary artery disease. The aims of this study were to demonstrate the feasibility of quantifying HRT in mice, both in long-term electrocardiograms (ECGs) as well as after extrastimulus pacing, and to analyse its characteristics. METHODS AND RESULTS: We performed long-term ECG recordings using implanted telemetric chips and electrophysiological (EP) investigations, using transvenously inserted EP catheters, in healthy mice. Heart rate turbulence was calculated using the established turbulence onset (TO) and slope (TS) algorithm. After spontaneous ventricular premature complexes (VPCs), we found a negative TO (-2.2 ± 7.5%) and positive TS (15.5 ± 18.3 ms/RR interval). Electrophysiological investigations revealed positive values for TO (0.6 ± 1.1%) and TS (6.5 ± 2.9 ms/RR interval) after extrastimulus pacing maneuvers. The shortening of the extrastimuli coupling intervals delivered during EP investigations significantly influenced TO (r = 0.57; P = 0.01): shorter coupling intervals provoked more positive TO values. CONCLUSION: Mice display both spontaneous and induced HRT. In terms of TO, VPCs generated by extrastimulus pacing are significantly dependent on the coupling interval. Determining HRT in mice is feasible and provides insight into basic mechanisms of blood pressure regulation, which is realized by the baroreflex.

Independent predictors of mortality in patients with advanced heart failure treated by cardiac resynchronization therapy.

AIMS: The current study includes all consecutive patients with advanced heart failure and cardiac resynchronization therapy (CRT) with an implantable cardioverter defibrillator (ICD) over a 10-year period in a tertiary referral centre. It aims at identifying independent risk factors for mortality during CRT-defibrillator (CRT-D) treatment. METHODS AND RESULTS: This study includes 239 consecutive patients who had undergone implantation of a CRT-D system (ejection fraction 25.9 ± 8%; 139 patients with ischaemic, 100 patients with non-ischaemic cardiomyopathy). Enrolment took place between 2001 and 2010, resulting in a median follow-up of 43 ± 30 months. During follow-up, 59 patients (25%) died. An impaired baseline kidney function [hazard ratio (HR) 1.98; 95% confidence interval (CI) 1.7-3; P< 0.0001], appropriate ICD therapy during follow-up (HR 2.1; CI 1.1-3.4; P= 0.001), lack of beta-blocker therapy (HR 2.3; CI 1.6-3.8; P= 0.004), and intake of amiodarone (HR 2; CI 1.8-4.1; P< 0.0001) were identified as predictors of overall mortality. CONCLUSION: This study demonstrates the benefit of beta-blocker therapy also in patients on long-term CRT-D treatment. It confirms the prognostic significance of impaired renal function and the occurrence of appropriate ICD therapies also in CRT-D patients. It argues for an intensified follow-up regimen and adjustment of heart failure treatment whenever these prognostic markers are identified in a patient treated with CRT-D.

The influence of the 2020 COVID-19 pandemic on the implantation rates of cardiac implantable electronic devices in Germany: changes between 2020 Q1-Q3 and 2019 Q1-Q3.

AIMS: During the early phase of the COVID-19 pandemic, hospital admissions for several medical and surgical conditions declined. Few data are available with respect to elective cardiac implantable electronic device (CIED) implantation. The aim of the present study was to determine the impact of the COVID-19 pandemic on the monthly CIED implantation rates in Germany (January-September 2020 vs. 2019). METHODS AND RESULTS: The monthly rates of CIED implantation for the 2019 pre- and 2020 pandemic periods were retrieved from the Institute für das Entgeltsystem im Krankenhaus using German Operation and Procedure Classification codes to identify pacemakers (PMs), implantable cardioverter/defibrillators (ICDs), and cardiac resynchronization therapy (CRT) systems. Compared with 2019, the COVID-19 pandemic was associated with an overall decline of CIED implantation rates of -2.6%, reaching -22.9% in April 2020. Stratified by device type, the patterns of implantation were similar between PMs and ICDs, with maximal declines of -24.3% and -23.2% in April, respectively. Thereafter, the implantation rates gradually increased before stabilizing to rates similar to those observed in 2019. CRT implantation rates also declined in the early pandemic wave, but the overall 2020 rates increased by +4.3% likely driven by an increase of +16.5% (June-September). All the observed percentage differences of monthly device type related implantation rates demonstrated a statistical significance. CONCLUSION: The COVID-19 pandemic had a significant impact on the implantation of CIEDs in Germany. A differential pattern of resource utilization was observed with a catch-up effect for PMs and ICDs. The implantation rates of CRT systems also declined, but they increased rapidly and remained higher than those of 2019.

Safety, feasibility, and diagnostic value of cardiac magnetic resonance imaging in patients with cardiac pacemakers and implantable cardioverters/defibrillators at 1.5 T.

BACKGROUND: Recent studies suggest that magnetic resonance (MR) imaging of the brain and spine may safely be performed in patients with pacemakers (PMs) and implantable cardioverter/defibrillators (ICDs), when taking adequate precautions. The aim of this study was to investigate safety, feasibility, and diagnostic value (DV) of MR imaging in cardiac applications (cardiac MR [CMR]) in patients with PMs and ICDs for the first time. METHODS: Thirty-two PM/ICD patients with a clinical need for CMR were examined. The specific absorption rate was limited to 1.5 W/kg. Devices were reprogrammed pre-CMR to minimize interference with the electromagnetic fields. Devices were interrogated pre-CMR and post-CMR and after 3 months. Troponin I levels were measured pre-CMR and post-CMR; image quality (IQ) and DV of CMR were assessed. RESULTS: All devices could be reprogrammed normally post-CMR. No significant changes of pacing capture threshold, lead impedance, and troponin I were observed. Image quality in patients with right-sided devices (RSD) was better compared with that in patients with left-sided devices (LSD) (P < .05), and less myocardial segments were affected by device-related artefacts (P < .05). Diagnostic value was rated as sufficiently high, allowing for diagnosis, or better in 12 (100%) of 12 patients with RSD, and only in 7 (35%) of 20 patients with LSD. CONCLUSIONS: Cardiac MR may be performed safely when limiting specific absorption rate, appropriately monitoring patients, and following device reprogramming. Cardiac MR delivers good IQ and DV in patients with RSD. Cardiac MR in patients with RSD may therefore be performed with an acceptable risk/benefit ratio, whereas the risk/benefit ratio is rather unfavorable in patients with LSD.

Remote monitoring of implantable-cardioverter defibrillators: results from the Reliability of IEGM Online Interpretation (RIONI) study.

AIMS: Intracardiac electrograms (IEGMs) recorded by implantable cardioverter-defibrillators (ICDs) are essential for arrhythmia diagnosis and ICD therapy assessment. Short IEGM snapshots showing 3-10 s before arrhythmia detection were added to the Biotronik Home Monitoring system in 2005 as the first-generation IEGM Online. The RIONI study tested the primary hypothesis that experts' ratings regarding the appropriateness of ICD therapy based on IEGM Online and on standard 30 s IEGM differ in <10% of arrhythmia events. METHODS AND RESULTS: A total of 619 ICD patients were enrolled and followed for 1 year. According to a predefined procedure, 210 events recorded by the ICDs were selected for evaluation. Three expert board members rated the appropriateness of ICD therapy and classified the underlying arrhythmia using coded IEGM Online and standard IEGM to avoid bias. The average duration of IEGM Online was 4.4±1.5 s. According to standard IEGM, the underlying arrhythmia was ventricular in 135 episodes (64.3%), supraventricular in 53 episodes (25.2%), oversensing in 17 episodes (8.1%), and uncertain in 5 episodes (2.4%). The expert board's rating diverged between determinable IEGM Online tracings and standard IEGM in 4.6% of episodes regarding the appropriateness of ICD therapy (95% CI up to 8.0%) and in 6.6% of episodes regarding arrhythmia classification (95% CI up to 10.5%). CONCLUSION: By enabling accurate evaluation of the appropriateness of ICD therapy and the underlying arrhythmia, the first-generation IEGM Online provided a clinically effective basis for timely interventions and for optimized patient management schemes, which was comparable with current IEGM recordings.

[Structural requirements and prerequisites for outpatient implantation of defibrillators, devices for cardiac resynchronization and event recorders]. / Strukturmerkmale und Voraussetzungen zur ambulanten Implantation von implantierbaren Defibrillatoren, Geräten zur kardialen Resynchronisation und Ereignisrekordern.

The possibility of outpatient implantation of defibrillators, devices for cardiac resynchronization, and event recorders (collectively called cardiac implantable electronic devices, CIEDs) is becoming increasingly important. In Germany, only a few options for outpatient implantation are currently realized. Furthermore, there is a lack of uniform, recognized, and binding quality criteria. This article provides insight into the current contract constellations for outpatient surgery and defines a first, holistic quality concept for outpatient implantations of CIEDs. The present works aims to initiate a discourse in the specialist society in order to define a coordinated, binding quality concept. Then, this should serve as the basis for future outpatient implantation services, enabling comparability and to contribute long-term evidence.

Incidence and predictors of silent cerebral embolism during pulmonary vein catheter ablation for atrial fibrillation.

AIMS: Left atrial catheter ablation of the pulmonary veins (PV) has evolved as an important therapeutic option for the treatment of atrial fibrillation (AF). We aimed to investigate the incidence and predictors of silent cerebral embolism associated with PV catheter ablation, detected by diffusion-weighted magnetic resonance imaging (DW-MRI). METHODS AND RESULTS: We performed a prospective analysis of 53 consecutive patients with persistent or paroxysmal AF that underwent PV ablation and post-procedural cerebral MRI 1 day after lasso catheter-guided ostial PV ablation. Patients were analysed for possible demographical, medical, echocardiographical, and procedural predictors of embolic events. A mean of 3.5 +/- 0.5 PVs were ablated per patient. In six patients, DW-MRI depicted new clinically silent microembolism after PV ablation (11%). The number of ineffective medical antiarrhythmic agents prior to ablation procedure was significantly higher in the embolism group (3.3 +/- 0.5 vs. 2.2 +/- 1.4, P = 0.014). Coronary heart disease (CAD) was more frequent in patients with cerebral embolisms (33 vs. 2%, P = 0.031); left ventricular volume (130 +/- 12 vs. 103 +/- 26 mL, P = 0.002), and septal wall thickness (13.0 +/- 1.4 vs. 7.9 +/- 4.8 mm, P = 0.025) were significantly increased. CONCLUSION: This study shows a high incidence of silent micro-embolic events after PV ablation. CAD, left ventricular dilatation, and hypertrophy were potential predictors of this complication.

Relation between detection rate and inappropriate shocks in single versus dual chamber cardioverter-defibrillator--an analysis from the OPTION trial.

The programming of implantable cardioverter-defibrillators (ICDs) influences inappropriate shock rates. The aim of the study is to analyse rates of patients with appropriate and inappropriate shocks according to detection zones in the OPTION trial. All patients received dual chamber (DC) ICDs randomly assigned to be programmed either to single chamber (SC) or to DC settings including PARAD+ algorithm. In a post-hoc analysis, rates of patients with inappropriate and appropriate shocks were calculated for shocks triggered at heart rates ≥ 170 bpm (ventricular tachycardia zone) and at rates ≥ 200 bpm (ventricular fibrillation zone). In the SC group, higher rates of patients with total and inappropriate shocks were delivered at heart rates ≥ 170 bpm than at rates ≥ 200 bpm (total shocks: 21.1% vs. 16.6%; p = 0.002; inappropriate shocks: 7.6% vs. 4.5%, p = 0.016; appropriate shocks: 15.2% vs. 13.5%; p = n.s.). No such differences were observed in the DC group (total shocks: 14.3% vs. 12.6%; p = n.s.; inappropriate shocks: 3.9% vs. 3.6%; p = n.s.; appropriate shocks: 12.2% vs. 10.4%; p = n.s.). The higher frequency of patients with total shocks with SC settings than with DC settings that benefit from PARAD+ was driven by a higher percentage of patients with inappropriate shocks in the VT zone (170-200 bpm) in the SC population.

Reduction of inappropriate ICD therapies in patients with primary prevention of sudden cardiac death: DECREASE study.

BACKGROUND: A significant number of patients with an implantable cardioverter/defibrillator (ICD) for primary prevention receive inappropriate shocks. Previous studies have reported a reduction of inappropriate therapies with simple modifications of ICD detection settings, however, inclusion criteria and settings varied markedly between studies. Our aim was to investigate the effect of raising the ICD detection zone in the entire primary prevention ICD population. METHODS AND RESULTS: 543 patients receiving an ICD for primary prevention were randomized to either conventional or progressive ICD programming. The detection rate was programmed at 171 bpm for ventricular tachycardia (VT) and 214 bpm for ventricular fibrillation (VF) in the Conventional group and 187 bpm for VT and 240 bpm for VF in the Progressive group. 43 % of patients received single-chamber and 57 % dual-chamber detection devices (DDD-ICD 19 %; CRT-D 38 %). The primary endpoint consisted of inappropriate therapies and untreated VT/VF. The primary endpoint was reached in 35 patients (13 %) in the Conventional group and 17 patients (6 %) in the Progressive group (p = 0.004). Progressive ICD programming led to significantly fewer amount of patients with ICD therapies (26 vs. 14 %; p < 0.001) and shocks (11 vs. 5 %; p = 0.023) compared to conventional ICD programming. Sub-analyses showed the greatest reduction of inappropriate therapies and shocks in dual-chamber detection devices with progressive compared to single-chamber detection devices with conventional ICD programming (p < 0.001). CONCLUSIONS: Progressive ICD programming reduces the number of inappropriate therapies and shocks in a broad primary prevention ICD population particularly in combination with dual-chamber detection algorithms. CLINICAL TRIAL REGISTRATION: http://clinicaltrials.gov ; ClinicalTrials.gov identifier NCT01217528.

Reduced risk for inappropriate implantable cardioverter-defibrillator shocks with dual-chamber therapy compared with single-chamber therapy: results of the randomized OPTION study.

OBJECTIVES: The OPTION (Optimal Anti-Tachycardia Therapy in Implantable Cardioverter-Defibrillator Patients Without Pacing Indications) trial sought to compare long-term rates of inappropriate shocks, mortality, and morbidity between dual-chamber and single-chamber settings in implantable cardioverter-defibrillators (ICDs) patients. BACKGROUND: The use of dual-chamber ICDs potentially allows better discrimination of supraventricular arrhythmias and thereby reduces inappropriate shocks. However, it may lead to detrimental ventricular pacing. METHODS: This prospective multicenter, single-blinded trial enrolled 462 patients with de novo primary or secondary prevention indications for ICD placement and with left ventricular ejection fractions ≤40% despite optimal tolerated pharmacotherapy. All patients received atrial leads and dual-chamber defibrillators that were randomized to be programmed either with dual-chamber or single-chamber settings. In the dual-chamber setting arm, the PARAD+ algorithm, which differentiates supraventricular from ventricular arrhythmias, and SafeR mode, to minimize ventricular pacing, were activated. In the single-chamber setting arm, the acceleration, stability, and long cycle search discrimination criteria were activated, and pacing was set to VVI 40 beats/min. Ventricular tachycardia detection was required at rates between 170 and 200 beats/min, and ventricular fibrillation detection was activated above 200 beats/min. RESULTS: During a follow-up period of 27 months, the time to the first inappropriate shock was significantly longer in the dual-chamber setting arm (p = 0.012, log-rank test), and 4.3% of patients in the dual-chamber setting group compared with 10.3% in the single-chamber setting group experienced inappropriate shocks (p = 0.015). Rates of all-cause death or cardiovascular hospitalization were 20% for the dual-chamber setting group and 22.4% for the single-chamber setting group and satisfied the pre-defined margin for equivalence (p < 0.001). CONCLUSIONS: Therapy with dual-chamber settings for ICD discrimination combined with algorithms for minimizing ventricular pacing was associated with reduced risk for inappropriate shock compared with single-chamber settings, without increases in mortality and morbidity. (Optimal Anti-Tachycardia Therapy in Implantable Cardioverter-Defibrillator [ICD] Patients Without Pacing Indications [OPTION]; NCT00729703).

Kidney dysfunction and deterioration of ejection fraction pose independent risk factors for mortality in implantable cardioverter-defibrillator recipients for primary prevention.

BACKGROUND: A growing number of patients with advanced heart failure fulfill a primary-prevention indication for an implantable cardioverter-defibrillator (ICD). This study seeks to identify new predictors of overall mortality in a Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT)-like collective to enhance risk stratification. HYPOTHESIS: An impaired renal function and severely depressed left ventricular ejection fraction pose relevant risk factors for mortality in primary prevention ICD recipients. METHODS: Ninety-four consecutive ICD patients with New York Heart Association class II-III heart failure and depressed left ventricular function (left ventricular ejection fraction [LVEF] ≤ 35%) with no history of malignant ventricular arrhythmias were followed for 34 ± 20 months. RESULTS: During this period, 30 patients died (32%). Deceased patients revealed a significantly worse renal function before ICD implantation (1.55 ± 0.7 mg/dL vs 1.1 ± 0.4 mg/dL; P = 0.007), suffered more often from coronary artery disease (53 vs 29; P = 0.006), and were older (69.5 ± 8 y vs 67 ± 12 y; P = 0.0002) than surviving patients. Furthermore, increased serum creatinine at baseline (2 mg/dL vs 1 mg/dL; odds ratio [OR]: 3.96, 95% confidence interval [CI]: 1.2-13.04, P = 0.02), presence of coronary artery disease (OR: 8.6, 95% CI: 1.1-65, P = 0.036), and low LVEF (OR per 5% baseline LVEF deterioration: 1.4, 95% CI: 1-1.8, P = 0.034) represented strong and independent predictors for overall mortality. CONCLUSIONS: Impaired renal function, the presence of coronary artery disease, and reduced LVEF before implantation represent independent predictors for mortality in a cohort of patients with advanced systolic heart failure. These conditions still bear a high mortality risk, even if ICD implantation effectively prevents sudden arrhythmic death. Indeed, in patients suffering from several of the identified "high-risk" comorbidities, primary-prevention ICD implantation might have a limited survival benefit. The possible adverse effects of these comorbidities should be openly discussed with the potential ICD recipient and his or her close relatives.

Adverse effects of permanent atrial fibrillation on heart failure in patients with preserved left ventricular function and chronic right apical pacing for complete heart block.

BACKGROUND: The impact of atrial fibrillation (AF) on heart failure (HF) was evaluated in patients with preserved left ventricular (LV) function and long-term right ventricular (RV) pacing for complete heart block. METHODS: Clinical, echocardiographic, and laboratory parameters of HF were assessed in 35 patients with established AF who had undergone ablation of the atrioventricular node and pacemaker implantation (Group A) and 31 patients who received dual-chamber pacing for spontaneous complete heart block (Group B). RESULTS: During a follow-up period of 12.7 ± 7.5 years, New York Heart Association (NYHA) functional class increased from 1.3 ± 0.5 to 2.1 ± 0.6 (p < 0.0001) in Group A, and from 1.3 ± 0.4 to 1.6 ± 0.7 (p < 0.01) in Group B. Left ventricular ejection fraction (LVEF) decreased from 59.7 ± 5.1 to 53.0 ± 8.2 (p < 0.0001) in Group A, but remained stable (58.6 ± 4.2 vs. 56.9 ± 7.0 %, p = 0,21) in Group B. At the end of follow-up, markers of LV function were moderately depressed in Group A compared with those in Group B: NYHA class 2.1 ± 0.6 versus 1.6 ± 0.7, p = 0.001; LVEF 53.0 ± 8.2 versus 56.9 ± 7.0 %, p < 0.05; LV diastolic diameter 53.6 ± 5.8 mm versus 50.7 ± 4.9 mm, p < 0.05; N-terminal pro-brain natriuretic peptide (NT-proBNP) 1116.8 ± 883.9 versus 622.9 ± 1059.4 pg/ml, p < 0.05. Progression of paroxysmal AF to permanent AF during follow-up was common, while new onset of AF was rare. Permanent AF was an independent predictor of declining LVEF >10 %, increasing NYHA class ≥1, and NT-proBNP levels >1,000 pg/ml. CONCLUSIONS: Permanent AF was associated with adverse effects on LV function and symptoms of HF in patients with long-term RV pacing for complete heart block, and appears to play an important role in the development of HF in this specific patient cohort.

Magnetic resonance imaging at 1.5-T in patients with implantable cardioverter-defibrillators.

OBJECTIVES: Our aim was to establish and evaluate a strategy for safe performance of magnetic resonance imaging (MRI) at 1.5-T in patients with implantable cardioverter-defibrillators (ICDs). BACKGROUND: Expanding indications for ICD placement and MRI becoming the imaging modality of choice for many indications has created a growing demand for MRI in ICD patients, which is still considered an absolute contraindication. METHODS: Non-pacemaker-dependent ICD patients with a clinical need for MRI were included in the study. To minimize radiofrequency-related lead heating, the specific absorption rate was limited to 2 W/kg. ICDs were reprogrammed pre-MRI to avoid competitive pacing and potential pro-arrhythmia: 1) the lower rate limit was programmed as low as reasonably achievable; and 2) arrhythmia detection was programmed on, but therapy delivery was programmed off. Patients were monitored using electrocardiography and pulse oximetry. All ICDs were interrogated before and after the MRI examination and after 3 months, including measurement of pacing capture threshold, lead impedance, battery voltage, and serum troponin I. RESULTS: Eighteen ICD patients underwent a total of 18 MRI examinations at 1.5-T; all examinations were completed safely. All ICDs could be interrogated and reprogrammed normally post-MRI. No significant changes of pacing capture threshold, lead impedance, and serum troponin I were observed. Battery voltage decreased significantly from pre- to post-MRI. In 2 MRI examinations, oversensing of radiofrequency noise as ventricular fibrillation occurred. However, no attempt at therapy delivery was made. CONCLUSIONS: MRI of non-pacemaker-dependent ICD patients can be performed with an acceptable risk/benefit ratio under controlled conditions by taking both MRI- and pacemaker-related precautions. (Implantable Cardioverter Defibrillators and Magnetic Resonance Imaging of the Heart at 1.5-Tesla; NCT00356239).

Incidence and characteristics of appropriate and inappropriate therapies in recipients of ICD implanted for primary prevention of sudden cardiac death.

BACKGROUND: We evaluated the number of appropriate and inappropriate therapies for ventricular tachyarrhythmias and trigger mechanisms in 55 MADIT II (MII)-like (group 1) and 86 SCD-HeFT-like (group 2) patients. METHODS AND RESULTS: We analyzed 399 appropriate episodes in 31 patients with implantable cardioverter defibrillators (ICD) implanted according to the MII trial indications, and 502 appropriate episodes in 47 patients matching the SCD-HeFT trial criteria (mean follow-up in both groups = 33 +/- 19 months). In group 1, 39 treated episodes were inappropriate (9% of all episodes), while in group 2, 76 episodes were treated inappropriately (15% of all episodes). At least one episode of inappropriate ICD therapy was recorded in 18% of patients in group 1 (n = 10) and in 22% of patients in group 2 (n = 19). CONCLUSIONS: Our study supports the implantation of ICD as primary prevention in patients who are at risk of sudden cardiac death, although the proportion of inappropriate ICD interventions remains high.

A new method to investigate the response to the morphology discrimination algorithm in patients with ICD.

BACKGROUND: Inappropriate therapy for supraventricular tachyarrhythmia is still a major problem in implantable cardioverter defibrillators (ICD). The morphology discrimination algorithm compares the morphology of a tachycardia electrogram with a stored template on a beat-to-beat basis. However, algorithm responders could not yet be identified prior to the occurrence of first tachycardia episodes. We analyzed whether rapid atrial pacing and/or exercise testing can be used for identification of responders and compared the results with ICD detected tachycardia. METHODS: 22 patients (16 male, 61+/-14 years) with dual-chamber ICDs have been enrolled. Patients underwent a standardized bicycle exercise testing and an atrial pacing protocol. For both tests, morphology match scores of 8 consecutive beats were analyzed for each 10-bpm-step increment above sinus rhythm. Patients were categorized as responders, if morphology match was > or = 90% of tested heart rates. During follow-up, ICD stored episodes with morphology discrimination activated were evaluated. RESULTS: There were no significant differences between morphology match (85+/-29% vs. 84+/-27%) and linear regression slope B (-0.19+/-0.87 vs. -0.20+/-0.48) during exercise testing and atrial pacing. 16 patients (73%) were classified as responders. During follow-up (739+/-338 days) 121 sustained supraventricular (n=88) and ventricular tachycardia (n=33) were detected in 10 patients (45%). Specificity for tachycardia discrimination was 78% overall, 100% in responders and 22% in non-responders. CONCLUSION: Exercise testing and atrial pacing were equally suitable for identification of patients who seem to respond to the morphology discrimination algorithm with a high specificity for ventricular tachycardia discrimination. Thus, morphology match tests are suggested to optimize tachycardia discrimination and to reduce inadequate therapies.

Automatic p wave analysis over 24 hours in patients with paroxysmal or persistent atrial fibrillation.

BACKGROUND: Patients with atrial fibrillation (AF) often exhibit abnormalities of P wave morphology during sinus rhythm. We examined a novel method for automatic P wave analysis in the 24-hour-Holter-ECG of 60 patients with paroxysmal or persistent AF and 12 healthy subjects. METHODS: Recorded ECG signals were transferred to the analysis program where 5-10 P and R waves were manually marked. A wavelet transform performed a time-frequency decomposition to train neural networks. Afterwards, the detected P waves were described using a Gauss function optimized to fit the individual morphology and providing amplitude and duration at half P wave height. RESULTS: >96% of P waves were detected, 47.4 +/- 20.7% successfully analyzed afterwards. In the patient population, the mean amplitude was 0.073 +/- 0.028 mV (mean variance 0.020 +/- 0.008 mV(2)), the mean duration at half height 23.5 +/- 2.7 ms (mean variance 4.2 +/- 1.6 ms(2)). In the control group, the mean amplitude (0.105 +/- 0.020 ms) was significantly higher (P < 0.0005), the mean variance of duration at half height (2.9 +/- 0.6 ms(2)) significantly lower (P < 0.0085). CONCLUSIONS: This method shows promise for identification of triggering factors of AF.

Determinants of heart rate turbulence after ventricular premature beats in healthy volunteers.

INTRODUCTION: A decline in the acceleration of the heart rate (HR, heart rate turbulence, HRT) after a ventricular premature capture is associated with increased mortality in patients suffering from coronary artery disease. The physiological properties of HRT have not been evaluated in a large human cohort. METHODS: In 95 healthy individuals, HRT parameters onset (TO) and slope (TS) as well as the turbulence timing (TT) were calculated from 24-hour Holter ECGs. With the help of a simple, linear, weighted regression model, gender specific differences of TO and TS were compared. A multiple linear regression model served to evaluate the influence of age and the basic HR preceding the ventricular premature contraction (VPC) on HRT. RESULTS: The median of TT is present in regression line #5. We discovered that, in men and women, TO is reduced as basic HR rises (p<0.01). In contrast, analysis of TS showed a divergence: in men, TS declines as basic HR increases. However, basic HR modifies TS in women to some extent (p<0.01). A multiple, linear regression model revealed a decrease of HRT with increasing age in men. CONCLUSIONS: The acceleration of HR after a ventricular premature beat occurred within the first 11 beats in more than 75% of our healthy individuals. An increased HR prior to VPC affects HRT in men. Increasing age leads to an attenuation of HRT in men and to a reduction of TO in women. These results emphasise the significance of the physiological properties of HRT when using HRT for risk stratification, especially in elderly patients.

[Cardiac pacing for the prevention of atrial fibrillation. A current review]. / Prävention von Vorhofflimmern durch Schrittmacherstimulation. Ein Uberblick über den aktuellen Studienstand.

Several prospective randomized clinical trials have reported that atrial-based "physiological" pacing is associated with a lower incidence of paroxysmal and permanent atrial fibrillation than single-chamber ventricular pacing in patients with conventional pacemaker indication. Whether atrial pacing itself is antiarrhythmic remains still uncertain. By contrast, right ventricular pacing is considered to beget atrial fibrillation, even in preserved AV synchrony during dual-chamber pacing. A number of clinical trials investigated the impact of sitespecific atrial pacing and advanced atrial pacing algorithms on the secondary prevention of atrial fibrillation. Multisite pacing (dual-site right atrial or biatrial pacing) was demonstrated to add only minimal benefit for the prevention of atrial fibrillation. By contrast, in some studies septal pacing and specific atrial pacing algorithms were reported to reduce the recurrence of atrial fibrillation in selected patients. At present, however, it remains unclear how to identify these patients. In clinical practice, the effectiveness of specific atrial pacing algorithms and/or septal pacing has to be tested out in the individual case. These therapeutic options should be considered in patients with a conventional indication for antibradycardia pacing and, additionally, symptomatic atrial fibrillation.

Impact of age and basic heart rate on heart rate turbulence in healthy persons.

Postextrasystolic acceleration of heart rate (HR), known as HR turbulence (HRT) is attenuated in patients with coronary artery disease at increased risk of adverse events. The influence of age and basic HR on HRT have not been evaluated in a large cohort of persons. In 95 healthy individuals, HRT onset (TO) and slope (TS) were calculated from 24-hour ambulatory electrocardiograms, as well as the turbulence timing (TT). Gender specific differences in TO and TS were compared in simple, linear, weighted regression model. The influence of age and the basic HR preceding ventricular premature contractions on HRT were examined. We found that, in men and women, TO decreases as basic HR increases (P < 0.01). In contrast, in men, TS decreased as basic HR increases, whereas in women, basic HR influenced TS only slightly (P < 0.01). A multiple, linear regression model revealed a decrease in HRT with increasing age in men. In conclusion, physiological acceleration of the HR within the first 11 beats after premature ventricular complex (VPC) was observed in >75% of healthy individuals. An accelerating HR preceding the VPC influenced HRT in men. An increasing age was associated with a decrease in HRT in men and a decrease in TO in women. These results illustrate the importance of physiological modulations of HRT when used for risk stratification, especially in older populations.

Advanced pacemaker diagnostic features in the characterization of atrial fibrillation: impact on preventive pacing algorithms.

Pacing algorithms to prevent PAF are mainly based on the suppression of premature atrial complexes (PACs), which play an important role in its initiation. In contrast to 24-hour ambulatory electrocardiograms, advanced pacemaker (PM) diagnostic features are capable of recording AF episodes during long follow-up periods and of characterizing AF in a detailed fashion. For the specific use of these algorithms, a detailed characterization of AF was performed in 91 dual chamber PM recipients with histories of AF. Fifteen patients with episodes of oversensing due to far-field signals or frequent episodes of "2:1-undersensing" of atrial flutter were excluded. The remaining 76 patients had high recurrence rates of AF (median 0.8 episodes/day), however, the majority of episodes lasted < 7 minutes. Despite frequent PACs (median 10.8/hour) during sinus rhythm, a median of 66.4% of the AF episodes were preceded by < 2 PACs/min before onset. In conclusion, frequent, short-lived AF episodes seem best suited for AF preventive pacing therapies. However, the small number of PACs preceding many AF episodes may limit the efficacy of PAC suppressing algorithms.