[Echocardiographic assessment of myocardial function during His bundle and right ventricular pacing]

INTRODUCTION

In patients with pacemaker (PM) therapy, His bundle stimulation (HBS) may lead to a more synchronous activation of the left ventricle (LV) than conventional right ventricular stimulation (RVS). In this study, we investigated to which extent this effect can be objectified by means of contemporary echocardiographic functional imaging.

METHODS

In all, 15 RVS patients (6 women, mean age 76.6 ± 4.1 years) and 15 HBS patients (6 women, mean age 74.6 ± 3.7 years) underwent echocardiography with and without cardiac pacing. Besides LV end-diastolic volume (EDV), ejection fraction (EF), and global strain (GLS), we measured global and regional myocardial work and LV efficiency based on noninvasive pressure-strain loops.

RESULTS

In all HBS patients, optimization of PM settings resulted in immediate changes in myocardial function parameters. With pacing, RVS patients showed a higher decrease in EF and GLS than HBS patients. Global LV work and LV work efficiency decreased significantly only in RVS patients.

CONCLUSION

Changes in regional and global myocardial function can by proven and quantified by functional echocardiography. In patients under PM therapy, HBS shows functional advantages in comparison to conventional RVS.

[Sudden cardiac death in diabetes mellitus]

Sudden cardiac death (SCD) represents one of the most frequent causes of death in patients with diabetes. In contrast to patients without diabetes it has not been significantly reduced despite improvements in the treatment of acute myocardial infarction and long-term treatment of cardiovascular diseases as well as diabetes mellitus. Several mechanisms can be responsible for the high incidence of SCD in diabetics: 1. arrhythmogenic effects mediated via cardiac autonomic neuropathy, repolarization disturbances or sympathetic tone activation (hypoglycemia), 2. myocardial ischemia due to atherosclerosis, endothelial dysfunction, platelet aggregation or thrombophilic effects, 3. myocardial disease due to inflammation, fibrosis, associated hypertension or uremia and 4. potassium imbalance due to diabetic nephropathy or hypoglycemia. This review introduces concepts of mechanisms that are responsible for SCD in patients with diabetes. Treatment of patients with diabetes should primarily consider a systematic assessment of any deterioration of this chronic disease and of complications at an early stage. Cardiovascular drug treatment corresponds to that of non-diabetics. In antidiabetic treatment drugs with a low risk of hypoglycemia should be preferred. Treatment with implantable cardioverter defibrillators (ICD) also combined with cardiac resynchronization therapy () demonstrated a high life-saving potential particularly in patients with diabetes.

[Device therapy of chronic heart failure: Update 2015]

Cardiac pacemakers, implantable cardioverter defibrillators (ICD) and systems for cardiac resynchronization therapy (CRT) represent an important component of heart failure therapy. Pacemakers only play a role in bradycardia-associated heart failure and require optimal programming to prevent ventricular desynchronization. Primary prophylactic ICD implantation is indicated in patients with a left ventricular ejection fraction of ≤ 35 %, clinical stages NYHA II-III and a life expectancy > 1 year. The CRT is indicated in patients with a left bundle branch block but only in individual cases for other QRS morphologies of < 150 ms duration. The combination of CRT with a pacemaker or defibrillator must be decided on an individual basis. Device therapy in heart failure should always include remote monitoring to detect events early and to implement treatment accordingly. New developments include quadripolar left ventricular leads and pacing from multiple sites simultaneously thus enabling better resynchronization. Stimulation for modulation of cardiac contractility and the autonomous nervous system are currently being clinically tested. The optimal utilization of device therapy improves the course of heart failure and prevents cardiac decompensation and fatalities.

[17-year-old student with recurrent seizures]

HISTORY

A 17-year-old female student presented in our emergency room after a seizure with motoric fits and enuresis. It was the second event of this kind within 3 weeks.

INVESTIGATIONS

The resting ECG on admission showed sinus bradycardia at 45 bpm and a remarkable repolarisation with notched or bifurcated T waves in several leads. Further clinical investigations were unremarkable.

TREATMENT AND COURSE

As an arrhythmogenic syncope (bradycardia or tachycardia related) was presumed, beta-blocker therapy was initiated and an implantable loop recorder (ILR) was inserted. Approximately one year after the index event, the student was brought to the emergency room by ambulance after another seizure. Interrogation of the ILR revealed torsade de pointes tachycardia with spontaneous termination after 1 min and 24 s. A dual-chamber ICD for secondary prophylaxis of sudden cardiac death was therefore implanted and the dose of beta-blocker was increased. Genetic analysis for long-QT-syndrome (LQTS) was negative with regards to the most frequent known gene loci. For 6 months the patient has been free of symptoms.

CONCLUSION

Arrhythmogenic syncopes can clinically resemble epileptic seizures ("convulsive syncope"). During basic work-up of syncope, the 12 lead ECG may provide valuable clues indicating an arrhythmogenic cause of syncope, showing excitation as well as repolarisation abnormalities. If an arrhythmogenic cause of syncope is suspected but ECG documentation as a proof of diagnosis is missing, implantation of an ILR can be useful. In LQTS, multiple gene mutations are known but cover only a fraction of clinical LQTS.

[ESC Guidelines on Pacemaker Therapy 2013: what is new and relevant for daily practice?]

The European Society of Cardiology (ESC) and the European Heart Rhythm Association (EHRA) published new guidelines for pacemaker and cardiac resynchronisation therapy in June 2013. The most important recommendations for daily clinical practice of pacemaker therapy firstly refer to the diagnosis of bradycardia and bradycardia-symptom-correlation. Bradycardia is classified into persistent and intermittent, the latter with and without documentation of spontaneous bradycardia. Evidence for pacemaker therapy depends on the quality of bradycardia-symptom-correlation. The indication for pacing in sick-sinus-syndrome and AV block is significantly simplified and the use of implantable loop-recording in syncope of unknown origin encouraged. If loop recorders document long asymptomatic pauses, the authors felt that an indication for pacing exists if pauses exceed 6 sec. Other newly defined pacing indications are syncope in bundle branch block and very long PR (> 300 ms), particularly in older patients and those with structural heart disease. New insights and recommendations are further provided for complications of pacemaker therapy, right ventricular pacing sites, perioperative anticoagulation, pacing and magnetic resonance imaging and remote monitoring. In conclusion, the new ESC guidelines elegantly summarize results of new trials and studies in bradycardia and pacemaker therapy and provide valuable recommendations for daily practice.

[Patient selection for the implantation of a left atrial appendage occluder in primary and secondary prevention of cardioembolic stroke in atrial fibrillation]

The implantation of a left atrial appendage (LAA) occluder has evolved into an established non-pharmacological alternative to oral anticoagulation (OAC) in the prevention of cardioembolic stroke in patients with atrial fibrillation. While 2 randomized trials investigated the LAA occluder as an alternative treatment in patients who can also undergo OAC, current guidelines recommend the LAA occluder rather as a second line therapy if permanent OAC is not possible due to contraindications. This is in line with current practice where an LAA occluder is usually only implanted if OAC is contraindicated or stopped due to bleeding. The LAA occluder seems most promising for patients with a high risk for both, stroke without OAC and severe bleeding with OAC. After patient informed consent, the LAA occluder may also represent an option for patients who are unwilling to undergo OAC. Since a large proportion of patients do not receive OAC despite an indication (because of contraindications or mere fear of bleeding) and since the majority of patients have to stop OAC during the course of 2 years, mostly due to bleeding, the LAA occluder may play an important role in the long-term prophylaxis of cardioembolic stroke due to atrial fibrillation.

[Recommendations of the Working Group of Arrhythmias of the German Society of Cardiology on the approach to patients with Riata® and Riata ST® leads (St. Jude Medical). Nucleus of the Working Group of Arrhythmias of the German Society of Cardiology]

Riata® and Riata ST® implantable cardioverter defibrillator (ICD) leads (St. Jude Medical, Sylmar, CA) show an increased incidence of insulation defects, particularly "inside-out" lead fracture where inner, separately insulated cables penetrate through the surrounding silicone of the lead body. The exact incidence of Riata® lead problems is not clear and seems to range between 2-4% per year in the first 5 years after implantation according to new registry data. We recommend beyond a detailed information the following care of patients with Riata® and Riata ST® leads: 1) Activation of automatic ICD alerts, 2) remote monitoring with automatic daily alerts whenever possible, 3) monthly ICD controls in patients at high risk (pacemaker dependency, history of ventricular tachyarrhythmias) and high or moderate lead-related risk (8F, 7F single coil), 3-monthly controls in moderate patient and lead-related risk, 3 to 6-monthly controls in low patient and lead-related risk (no bradycardia, no history of ventricular tachyarrhythmia). Every ICD control should include meticulous analysis of oversensing artifacts in stored electrograms (EGMs) of sustained and non-sustained ventricular tachyarrhythmias and registration of EGMs during provocation testing (pectoral muscle activity, arm movements). If electrical abnormalities are observed, reoperation with addition of a new ICD lead is recommended; lead extraction only if indicated according to current guidelines. Fluoroscopy should only be performed if electrical abnormalities are found by an experienced electrophysiologist and a high frame rate and resolution. Management of fluoroscopic abnormalities in the absence of electrical abnormalities is not clear. Therefore, routine fluoroscopy of patients with Riata® leads without electrical abnormalities is not recommended.

[Commentary on the 2010 ESC guidelines on device therapy in heart failure ]

As part of the 2010 focused update of ESC guidelines on device therapy in heart failure, the guidelines on pacemakers in the treatment of heart failure were renewed. A new feature is that cardiac resynchronization therapy (CRT) is indicated for New York Heart Association (NYHA) class III and IV irrespective of the presence of left ventricular dilatation and specified for NYHA class IV (patient ambulatory, stable, life expectancy >6 months). Furthermore, NYHA class II (but not class I) has been added when there is left bundle branch block and QRS duration ≥150 ms. CRT is also indicated for patients in NYHA class III-IV with permanent atrial fibrillation and heart failure [left ventricular ejection fraction (LVEF) ≤ 35%] when QRS is ≥ 130 ms and ventricular rate has slowed either spontaneously or by AV node ablation. In patients with heart failure (NYHA class II-IV, LVEF ≤ 35%) who need a pacemaker for AV block, CRT is generally indicated to avoid progression of heart failure caused by right ventricular stimulation, also in cases of intrinsic QRS <120 ms. For patients with terminal heart failure who are not eligible for heart transplantation, treatment with a left ventricular assist device can be performed as destination therapy. The new guidelines expand the indication for device therapy in heart failure based on the newest study findings, particularly for patients in NYHA class II, and specify the old guidelines. There are still uncertainties that must be investigated in randomized trials regarding patients with permanent atrial fibrillation, the indication for CRT in heart block, and the question of CRT with pacemaker or defibrillator.

[Electrical therapy for heart failure. Perspectives for 2011]

Implantable defibrillators (ICDs) and cardiac resynchronization therapy (CRT) represent established treatments for heart failure with positive results from clinical trials. However, for daily practice, several questions on the optimal use remain (e.g., patient selection, imaging, pacing sites). In addition, new treatment options which attempt to improve heart failure by modulating cellular calcium handling and autonomic dysbalance have recently been developed. For cardiac contractility modulation, initial results from randomized trials have been published. At present, the use of vagal stimulation is also being studied in clinical trials in Germany. New approaches refer to stimulation of sympathetic ganglia in the coronary sinus and left ventricular multisite pacing by ultrasound, but are still in the stage of acute testing.

[Pacemaker ECG Quiz No. 23: Pacemaker malfunction or arrhythmia?]

In a 69-year-old patient, a DDDR pacemaker was implanted for sinus node disease with syncope due to sinus arrest with pauses > 4 s. Programming was performed carefully including measures to prevent unnecessary ventricular pacing. Approximately 6 months after implantation, the patient who was asymptomatic in the meantime presented for pacemaker control because the ECG had raised the question of pacemaker malfunction.

[Stored electrograms in pacemakers and ICDs]

Stored electrograms (EGMs) represent an important development in pacemaker and ICD therapy. The most important issue in pacemaker EGMs is the confirmation of the detection of atrial tachyarrhythmias, especially atrial fibrillation. In ICD therapy, the discrimination between ventricular and supraventricular tachycardia (i.e., detection of inadequate therapy) is of central interest. Unfortunately, systematic"instructions" for interpreting stored EGMs in systems by different manufacturers are not available and the knowledge on this topic is limited to (too) few experts. The contributions in this issue aim at explaining the interpretation of stored EGMs in systems by different manufacturers, providing an understanding of marker annotations and EGM registrations in clinical examples. With the aim of improving pacemaker and ICD therapy, a broad distribution of knowledge on the usefulness and the practical use of stored EGMs is highly desirable.

[Pacemaker ECG quiz no. 22. A CRT non-responder with atrial fibrillation]

A patient with heart failure functional class NYHA III and permanent atrial fibrillation received a system for cardiac resynchronization therapy. Unfortunately, he reports at a follow-up visit about a completely unchanged poor exercise capacity with dyspnea during exercise at a very low level. The ECG reveals an unusual mode of stimulation.

[ICD therapy for the primary prevention of sudden cardiac arrest. The patient after a myocardial infarction]

ICD therapy represents a major advance in the treatment of patients with severely impaired left ventricular function after myocardial infarction. While an ICD implantation also remains a valuable option late (>5 years) after myocardial infarction, patients early after this event are at a competitive risk of arrhythmogenic and nonarrhythmogenic cardiac death. Prevention of sudden cardiac death in patients early after myocardial infarction, therefore, just converts the mode of death in a significant number of patients from sudden to nonsudden cardiac death (conversion theory). In patients with a left ventricular ejection fraction (LVEF) of < or =30% after myocardial infarction, implantation of the ICD should, therefore, be postponed to at least 30-40 days after the event. It is, however, not clear how the risk of sudden cardiac death should be approached during this post infarction phase. Similarly, it is not clear if patients with a reduced LVEF post infarction and additional specific risks (nonsustained ventricular tachycardia, atrial fibrillation, bundle branch block, etc.) beyond this single criterion may also benefit from ICD implantation and which risk factors may be relevant. In any case, ICD therapy should avoid right ventricular pacing and shock discharges whenever possible.

[Pacemaker ECG quiz no. 21: Strange ECG after DDDR pacemaker implantation]

In a patient with sinus node disease (intermittent sinus arrest with symptomatic pauses >4 s), a DDDR pacemaker with a dedicated algorithm to avoid unnecessary ventricular pacing (mode switch between AAIR and DDDR) was implanted. The pacemaker ECG after implantation shows an unexpected tachycardia.

[Stored electrograms in pacemakers and ICDs from St. Jude Medical]

Stored electrograms (EGMs) significantly improve pacemaker and ICD therapy. In pacemaker systems, the main focus of stored EGMs concerns the manual control of device detection of atrial tachyarrhythmias, especially atrial fibrillation. In ICD therapy, stored EGMs allow the discrimination of adequate and inadequate detection of ventricular tachycardia. This review presents the implementation of stored EGMs in systems from St. Jude Medical and explains the mode of EGM storage and marker annotations, which are useful for interpretation of stored EGMs and to understand the way the device interprets the EGM. Clinical examples illustrate appropriate and inappropriate device classifications.

[Stored electrograms in pacemakers and ICDs from Boston Scientific]

The storage of electrograms in pacemakers and ICDs represents an important step forward in the detection of asymptomatic arrhythmias (e.g., paroxysmal atrial fibrillation) and the distinction between appropriate and inappropriate therapies. This review presents via clinical examples the information provided in stored electrograms in systems from Boston Scientific and tips how to interpret them.

Do gender differences exist in pacemaker implantation?--results of an obligatory external quality control program

AIMS

The aim of the study was to evaluate the effects of patient gender onto primary pacemaker implantation, evaluating the database of the Institute of Quality Assurance Hessen in the federal state of Hessen, Germany.

METHODS AND RESULTS

The database of the obligatory external quality control program for the years 2003-2006 was evaluated retrospectively. In 72 centres, 17 826 patients undergoing stationary primary pacemaker implantation have been registered. Male patients had more AV blocks when compared with women and less sick sinus syndrome and atrial fibrillation with bradycardia. In patients being 80 years and older, men received significantly more dual-chamber devices than women for the indications: AV block and sick sinus syndrome. In women, atrial pacing thresholds were significantly higher and P-wave amplitudes were significantly lower. Women had, independent from age or pacing system implanted, significantly more acute complications than men, with significant differences for pneumothorax and pocket haematoma.

CONCLUSION

This large-scale real-life patient cohort of primary stationary pacemaker implantation showed that gender has an impact onto pacemaker implantation, with less favourable outcomes for women.

[Pacemaker ECG Quiz No. 20. Multiple ventricular extrasystoles with a little extra]

A patient with ischemic heart disease and dual-chamber pacing for binodal disease, exhibiting a complex pacemaker ECG, is presented.

[Pacemaker ECG quiz: AV sequential pacing--what is happening?]

The present case of a 55-year-old patient with heart failure displays a complex pacemaker ECG.

[Fast heart rate after a ventricular premature beat--what is the mechanism?]

A 61-year-old patient with sinus node disease and intermittent AV block presented with palpitations and the feeling of an intermittent fast heart beat. A 24 h Holter recording documented repetitive fast heart rates starting after a premature ventricular beat. This case underlines that sometimes profound knowledge of the implanted pacemaker system is necessary to optimize device therapy.

[Sandwiched between the single- and triple-chamber ICD: do we still need the dual-chamber ICD?]

Since it has been shown that adverse events are more frequent with dual-compared to single-chamber ICDs in patients with heart failure, and since the importance of prevention of unnecessary right ventricular pacing and the success of biventricular pacing have been demonstrated in numerous studies, the need for dual-chamber ICD systems has to be reassessed. The development of these systems was accompanied by expectations of improved hemodynamics in patients with bradycardia, a reduced incidence of atrial fibrillation, inappropriate therapies, and bradycardia-associated ventricular tachyarrhythmias. Single-chamber ICDs should be used restrictively and with great caution in patients with (sinus-) bradycardia and heart failure, since a relevant proportion of these patients is at risk of hemodynamic deterioration. Even if the proportion of patients with proven pacemaker syndrome is so small that it does not reach the level of statistical significance in large studies, a small percentage of patients with hemodynamic deterioration due to VVI pacing is still clinically (and economically) intolerable. Since the development of bradycardia or symptomatic chronotropic incompetence (e.g., due to amiodarone) is difficult to predict, it seems reasonable to use the indication for dualchamber systems liberally. However, the systematic prevention of unnecessary right ventricular pacing is crucial if dual-chamber ICDs are used. If advanced tachycardia discrimination algorithms and careful, individual programming are used, dual-chamber ICDs are superior in the prevention of inappropriate therapies. Additionally, dualchannel electrograms allow a more reliable interpretation of stored tachycardia episodes. In summary, dual-chamber systems represent a valuable improvement of ICD therapy but require thorough programming to convey their advantage.

[17th part: Transvenous pacemaker implantation in corrected Fallot tetralogy with heart failure]

Implantation of transvenous pacemaker leads can be particularly--and unexpectedly--difficult in patients with corrected congenital heart disease. If the operation has been performed a long time ago, there are frequently no more reports about the exact intervention available. The present case illustrates the importance of the ECG and fluoroscopy during implantation in complex congenital heart disease.

[16th part: ventricular lead position]

This case illustrates how the ventricular lead position can be defined exactly if different fluoroscopic views and a 12 lead ECG are available.

Stroke complicating congenital sick sinus syndrome

We report the case of a patient with congenital sick sinus syndrome complicated by atrial fibrillation and embolic stroke 23 years after the initial diagnosis, at the age of 34 years. Treatment with a dual-chamber pacemaker and oral anticoagulation were initiated; further follow-up was uneventful but pacemaker diagnostics constantly documented asymptomatic recurrences of paroxysmal atrial fibrillation.

Non-invasive risk stratification: prognostic implications of exercise testing

The interpretation of exercise ECGs is frequently limited to an assessment of the ST segment for evaluation of ischemia. However, exercise testing represents a simple test of the complex interactions of the autonomous nervous system and provides a multitude of information with independent prognostic information. This overview summarizes available studies on the significance of chronotropic incompetence, exercise capacity, heart rate recovery after exercise, and the incidence of ventricular premature activity during or after exercise. These parameters express subclinical pathophysiological changes which cannot be identified by other means, e. g., coronary angiography or echocardiography. A reduced maximal heart rate under exercise may indicate a "blunted" sympathetic reaction as a protective myocardial reaction to an increase in left ventricular wall stretch in preclinical forms of heart failure. A reduced exercise capacity, measured in metabolic equivalents, METs, is one of the strongest predictors of cardiac and all cause mortality. A reduced heart rate recovery after exercise indicates an increased sympathetic tone or lack physiological increase in vagal tone; increased ventricular ectopy potentially identifies preclinical cardiomyopathy. This summary of study results aims at providing a new view on exercise testing that should lead to an improved understanding of relevant information included in the exercise ECG.

Use of telemedicine in the diagnosis of paroxysmal atrial fibrillation and to monitor the effect of antiarrhythmic drug therapy

We present the case of a patient with highly symptomatic tachyarrhythmias for 2 years without any arrhythmia documentation despite numerous ECG and Holter registrations. By means of telemedicine, it was possible to document the arrhythmia--in this case atrial fibrillation--within 10 days and to start antiarrhythmic drug treatment with flecainide and metoprolol. This case demonstrates the diagnostic potential of telemedicine in patients with recurrent episodes of tachyarrhythmias in whom episodes are not sufficiently frequent to allow diagnosis by Holter monitoring. Telemedicine may also be advantageous for ECG monitoring during the early phase after cardioversion or initiation of specific antiarrhythmic pharmacotherapy in order to detect potential drug-induced proarrhythmic changes.

[Progression of heart failure during cardiac resynchronization therapy: what is the cause?]

A 74 year old patient with cardiac resynchronization therapy (CRT) since 12 months presents with cardiac decompensation and dyspnea NYHA III-IV after improvement of cardiac symptoms for 9 months. Her history is remarkable for left ventricular hypertrophy, aortic valve replacement 14 years earlier, a left ventricular ejection fraction of 35-40%, and permanent third degree AV block. The 12 lead standard ECG reveals the cause of cardiac deterioration which is confirmed by telemetry. This case demonstrates the importance of optimized programming of CRT systems which differs from conventional programming of dual-chamber devices in some aspects.

[Cardiac resynchronization therapy in patients with permanent atrial fibrillation--with or without atrial lead?]

A 59-year-old patient received a biventricular defibrillator for cardiac resynchronization therapy (CRT) due to severe heart failure and a left bundle branch block. He had suffered from mitral stenosis and had received valve replacement 16 years earlier. Because he had permanent atrial fibrillation since that time, no atrial lead was implanted. His symptoms improved with CRT until he received adequate shock therapy for a rapid ventricular tachyarrhythmia. After that his symptoms deteriorated again severely. The ECG recorded during an unscheduled follow-up visit 1 week after the shock explains the reason.

[Difficult AV optimization in a patient with a biventricular implantable cardioverter defibrillator]

This quiz presents the case of a patient who deteriorated clinically after AV delay optimization of a biventricular implantable cardioverter defibrillator. It illustrates that these complex devices require profound knowledge of their function.

[Indication for cardiac resynchronization therapy: Consensus 2005]

The indication for cardiac resynchronization therapy (CRT) using biventricular pacing or ICD systems has to be highly differentiated to optimize the proportion of patients who derive significant symptomatic benefit from this therapy, on the one hand, and to avoid this invasive treatment in patients with a low probability of clinical success of CRT, on the other hand. As a consensus in 2005, it can be put forward that there is sufficient evidence for an indication for CRT from clinical studies for the following characteristics: 1) Heart failure in NYHA functional class III or IV (if cardiac recompensation to class III is at least temporarily successful), 2) left ventricular ejection fraction < or =35%, 3) QRS duration >130 ms, particularly if left bundle branch block is present, 4) sinus rhythm. In addition, available data also suggest an indication for CRT in patients with atrial fibrillation if the other criteria listed above are met. The indication for CRT is unclear in patients with other intraventricular conduction delay (particularly right bundle branch block) while patients with left bundle branch block and a QRS duration of 120-130 ms seem to benefit if echocardiographic criteria demonstrate ventricular dyssynchrony. Since a multiplicity of echocardiographic criteria of ventricular dyssynchrony exists which is neither standardized nor evaluated in large-scale randomized trials, ventricular dyssynchrony on echocardiography alone cannot be regarded as an established indication for CRT without a QRS complex > or =120 ms. Similarly, whether heart failure in functional state NYHA II should be regarded as a CRT indication is currently being investigated in the randomized RAFT and MADIT-CRT trials.

[Technical requirements for early defibrillation: what are the capabilities of automated external defibrillators]

Modern automated external defibrillators (AEDs) offer a variety of technical improvements which increase the efficacy of early defibrillation, facilitate the application by not or minimally trained persons and improve safety. The development of biphasic shocks allows better myocardial protection, the use of lithium batteries, and a marked decrease of AEDs, in size. Microprocessors realize complex acoustic and visual prompts which lead the user through all steps of cardiopulmonary resuscitation (CPR) according to current guidelines. The design of AEDs has been simplified; many devices provide only a single button which can be used for all active processes. Memory functions record the whole CPR with all details which can be transferred to other computers and analyzed off-line. The introduction of AEDs has reduced the delay between collapse and defibrillation to less than 4 min in several studies thus increasing the success of CPR and the proportion of patients dismissed from hospital alive and without neurological deficit. Up to 93% of untrained volunteers were able to successfully complete defibrillation with the use of an AED, sixth-form pupils without experience in CPR were only few sec slower with an AED than staff of emergency medical services. The ability to perform CPR after defibrillation guided by the AED depends primarily on the clarity of acoustic prompts which have to consider the terms and abbreviations of the respective language. Currently available AEDs surpass performance goals of the AHA. However, all devices exhibit advantages and disadvantages which will be discussed in this review.

Incremental programming of atrial anti-tachycardia pacing therapies in bradycardia-indicated patients: effects on therapy efficacy and atrial tachyarrhythmia burden

AIMS

Efficacy of pace-termination of atrial arrhythmias (ATP) may depend on atrial cycle length and regularity. Whether device programming of ATP therapies can improve ATP efficacy and alter atrial tachyarrhythmia burden is unknown.

METHODS AND RESULTS

ATP efficacy was evaluated in 61 patients (39 males; 66 +/- 10 years) with a standard indication for pacing, 95% with a history of AT/AF. Each patient was implanted with a novel DDDRP pacemaker capable of delivering ATP therapy. ATP efficacy and AT/AF frequency and burden were compared within each patient during a period of nominal ATP programming (NP) followed by a period of aggressive incremental programming (IP). Adjusted ATP-termination efficacy was higher during IP than during NP (54.8% vs 37.9%, P < 0.05). No differences in AT/AF frequency (3.3 +/- 5.9 vs 3.2 +/- 6.9 day(-1)) or burden (18 +/- 28% vs 18 +/- 29%) were observed comparing NP with IP. The majority of episodes during both the NP (81%) and IP (77%) periods terminated within 10 min. Episodes lasting 24 h or more accounted for only 0.4% of the episodes in both groups. but accounted for 38% of the average burden during NP and 51% during IP.

CONCLUSIONS

Device programming of ATP therapies can influence the number of treated episodes and the efficacy of ATP therapies although arrhythmic frequency and burden may not change. Total atrial arrhythmia burden is disproportionately influenced by long (>24 h) episodes.

Prediction of early recurrence of atrial fibrillation after external cardioversion by means of P wave signal-averaged electrocardiogram

BACKGROUND

Therapy of atrial fibrillation by electrical cardioversion (CV) is limited by the high rate of recurrences. Early recurrence of atrial fibrillation (ERAF) occurs in a subgroup of patients whose characteristics are poorly defined. This prospective study was performed to evaluate if the P wave signal-averaged ECG (PSAECG) is able to identify patients with an increased risk of ERAF after CV.

METHODS

Patients with an indication for elective external CV were enrolled. After successful CV, PSAECGs were recorded at 0.5, 1, 24 h and 1 week. The ability of PSAECG parameters (signal-averaged P wave duration, PWD; root-mean-square of the voltage of the terminal 20, 30, and 40 ms of the signal-averaged P wave; RMS20, RMS30, RMS40) to predict ERAF (prospectively defined as AF recurrence within 4 h after CV) was assessed.

RESULTS

Of 111 consecutive patients, 7 experienced ERAF, 30 patients had AF recurrence later during the 1-week follow-up. Patients with ERAF had a significantly prolonged signal-averaged PWD compared to patients who remained in SR (194+/-16 ms vs 139+/-3 ms at 0.5 h, p<0.001). As ROC analysis revealed, a PWD >/=154 ms at 30 min after CV had the highest predictive accuracy for ERAF (sensitivity 100%, specificity 82%, positive predictive value 33%, negative predictive value 100%). Other parameters of the PSAECG did not reveal significant differences between patients with and without ERAF.

CONCLUSIONS

The PSAECG provides a sensitive noninvasive tool for detection of patients at risk of ERAF. Thus identified, tailored pharmacological therapy is conceivable to prevent ERAF.

Single-lead VDD-pacing system incorporating high impedance stimulation: a multicentre study

AIM

The purpose of this study was to evaluate the performance of a new VDD pacing system incorporating a high impedance, single-pass VDD lead. The new lead is a bipolar, steroid-eluting, high impedance lead with a full-ring atrial dipole.

METHODS AND RESULTS

The system was implanted in 46 patients with high degree atrioventricular (AV) block. Patients were followed at pre-discharge, 6 weeks, and 3 months. The mean measured P-wave amplitude was stable, with values between 1.18 and 1.43 mV. Atrial sensing was reliable during short-term evaluation at rest and in the sitting position, with AV-synchronous stimulation between 98.79 +/- 6.90% and 99.73 +/- 1.47%. Holter recordings after 6 weeks demonstrated AV-synchronous stimulation in 99.57 1.03% of all P-waves. Lead impedance was stable during follow-up, with mean values between 1000 and 1167 Q. Mean ventricular pacing thresholds (at 0.5 ms) were 0.47 V at implant, 0.49 V at pre-discharge, 0.74 V at 6 weeks, and 0.72 V at 3 months. R-wave amplitude remained stable between 14.9 and 16.7 mV during follow-up.

CONCLUSION

This new single-pass VDD lead system provided reliable atrial sensing and stable high impedance stimulation during a 3-month follow-up period.