Concealed accessory pathways: Historical notes.

Concealment of an accessory pathway is caused by its ability to conduct retrogradely only. This variant of accessory pathway conduction could not be confirmed until invasive electrophysiology was introduced in the 1970s. As a rule, it is reported that concealed accessory pathways were predicted from animal experiments in 1971. However, even earlier studies suggested an accessory pathway or mechanisms comparable to those of the Wolff-Parkinson-White syndrome to be the cause of supraventricular tachycardias even though preexcitation during sinus rhythm had been lacking. Such interpretations were derived from clinical considerations, from patients having lost their ventricular preexcitation spontaneously, and from the disappearance of the delta wave after drug administration. Some authors postulated but did not provide the correct interpretation. Even a few contributions published before the paper of Wolff, Parkinson, and White in 1930 are worth considering in this context.

[CRT in atrial fibrillation--methodical and apparatus options in decision-making]. / CRT bei Vorhofflimmern. Methodische und apparative Optionen zur Entscheidungsfindung.

Heart failure and atrial fibrillation often coexist, especially with increasing degree of heart failure severity. Under this constellation, the advantage of cardiac resynchronization therapy (CRT) is still under discussion and displayed as an unresolved problem in the guidelines for cardiac stimulation and resynchronization. If ventricular desynchronization can be documented and response to CRT can be expected, the challenge is to interoperatively seek the best left ventricular electrode position and to postoperatively optimize the device in order to achieve the best therapy performance. This situation encourages the development of individualized methods and to utilize innovative apparatus features in order to consolidate individual decisions and to optimize CRT in heart failure with atrial fibrillation.

[The discovery of the sinus node 100 years ago and the part of K. F. Wenckebach]. / Die Erstbeschreibung des Sinusknotens vor 100 Jahren und die Rolle K. F. Wenckebachs.

Hundred years ago, in 1907, A. Keith and M. Flack described histologically in the right atrium of different mammalian including human hearts a structure which they called sinu-auricular node and which they interpreted as the place where the heart beat originates. One year earlier K.F. Wenckebach had reported on an arrhythmia which he explained by polygraphic technique as "vein-atrial block" (today: sinoatrial block). To such an assumption he had to suppose that the heart action begins in the vena cava superior where he described a "small but interesting musculature" above the atrium as the morphological basis of the origin. Recently, with regard to the publication dates of these findings it was claimed (W. Ehrlich) that we should owe the honour of having discovered the sinus node morphologically to Wenckebach and not to Keith and Flack. Referring to the original publications it is shown that Wenckebach as well as Keith and Flack refered to different ideas. Wenckebach supposed the location of the origin of the heart beat in a macroscopically discernible muscle placed at the vena cava superior just above but separated from the right atrium. As the only connection capable of conduction between both he described a special bundle. On the contrary, Keith and Flack depicted as the place where the heart action begins a microscopically defined structur in the atrium at the junction of the vena cava superior with the sorrounding venous and atrial musculature being not separated from each other. Scientific progress corroborated the interpretation of Keith and Flack, while Wenckebach desisted only slowly from his position which, after all, proved incorrect.

[Left ventricular electromechanical latency period is an additional indicator to upgrade from right to biventricular DDD pacing]. / Die linksventrikuläre elektromechanische Latenzzeit ist ein zusätzlicher Indikator für ein Upgrading zur biventrikulären Stimulation.

In DDD pacing, the left-ventricular electromechanical latency period defines the duration between premature ventricular stimulation and the prematurely ending left-atrial contribution to left-ventricular filling. It has to be considered in diastolic AV delay optimization. Individual duration of this parameter seemed to reflect the ventricular function. Therefore, we compared the left-ventricular electromechanical latency period due to right ventricular stimulus with the documented ejection fraction of two groups, 33 congestive heart failure patients carrying biventricular systems and 13 right ventricular paced bradycardia patients. A mean latency period of 168+/-26 ms was found in the heart failure patients (ejection fraction: 25+/-5%) which was significantly longer (p=0.0039) compared to the bradycardia patients (ejection fraction: 51+/-12%) with a mean latency of 119+/-13 ms. Thus, an increasing latency period during right ventricular DDD pacing therapy indicates decreasing ejection fraction. A cut-off interval of 135 ms allowed the discrimination of 93% of our patients as having an individual ejection fraction of either up to 35% or above. Thus, the left ventricular electromechanical latency period can be used as an additional parameter indicating the necessity to upgrade from right to biventricular DDD pacing.

[Feasibility and safety of long-term AAI(R) pacing in isolated sinus node syndrome]. / Realisierbarkeit und Sicherheit einer alleinigen AAI(R)-Schrittmacherbehandlung beim isolierten symptomatischen Sinusknotensyndrom.

Recent investigations prove that AAI(R) pacing is the "ideal" stimulation mode in isolated sick sinus syndrome. Nevertheless, in Germany this bradycardia is treated by AAI(R) pacemakers in less than 4% of cases compared to 25% in other countries. In our institution treatment of patients with isolated sick sinus syndrome is uniform and corresponds to the actual guidelines since the early 1990s; therefore the aim of our study was to analyze feasibility and safety of AAI(R) pacing in a retrospective study. Between 1998 and 2000, 52 of 165 patients (31.5%) with isolated sick sinus syndrome were treated by an AAI(R) pacemaker. The median follow-up duration was 51.5 months (minimal: 36 months). 6 patients died, in all cases unrelated to the stimulation mode. Three patients required reoperations, however, in only one case due to second degree AV block with the need for upgrading to DDD stimulation. Thus, the yearly incidence of this specific complication in the AAI(R) cohort is 0.64%.In conclusion, permanent atrial stimulation in isolated sick sinus syndrome is feasible in a quarter of all cases. It is safe if performed corresponding to actual guidelines. Additionally, single lead AAI(R) pacing is a cost-effective therapy and the only stimulation mode which, today, reliably prevents unnecessary right ventricular stimulation. If, on the other hand, algorithms providing automatic mode switching from AAI to DDD and vice versa are implemented reliably into all dual chamber pacemakers, single chamber atrial pacing will no longer be a subject for discussion.

[WPW cases in the literature prior to the publication of Wolff, Parkinson and White in 1930]. / Die WPW-Kasuistiken in der Literatur vor der Publikation von Wolff, Parkinson und White im Jahr 1930.

In 1930, Wolff, Parkinson and White described the clinical entity of what is today known as the preexcitation or WPW syndrome. In the preceding literature, the authors found four comparable cases. Later on, seven further cases published prior to 1930 were discovered. An analysis of the altogether eleven cases displays that, in addition to the anomalous ECG in sinus rhythm, nearly all typical electrocardiographic findings during the tachyarrhythmias are found in this early literature. As tachycardia ECGs especially help to understand the mechanism of the WPW syndrome, the question is discussed whether already Wolff, Parkinson and White would have been able to give the correct interpretation of the mechanism if they had taken into consideration their own tachycardia ECGs as well as those known to them from the literature.

Randomized comparison of direct and provisional stenting in de novo coronary artery lesions: the RADICAL study.

BACKGROUND: Although preliminary reports have demonstrated excellent primary success and improved economics with direct stenting, a clinically relevant reduction of restenosis rate has not been documented yet. AIMS: Aims of the study were the comparison of restenosis rate (primary endpoint), procedural success, fluoroscopy time, amount of contrast dye and clinical outcome (secondary endpoints). METHODS AND RESULTS: Between January and December 1999, 250 patients were randomly assigned either to direct stent implantation without predilatation (DS; 125 patients) or provisional stenting (PB; 125 patients) and followed for 7.9+/-2.7 (6-9) months. Angiographic follow-up was available in 92.0% of patients. Procedural success rate was 92.8% in DS and 100% in PB (n.s.), while radiation exposure was lower (4.7+/-4.3 versus 5.1+/-1.8 min; p<0.0001) with DS. Conversely, the amount of contrast dye (131+/-62 versus 139+/-36 ml; n.s.) was not different between DS and PB. Direct stenting leads to a 25.0% reduction in binary restenosis rate (15.7% in DS versus 20.9% in PB), indicating an advantageous trend, missing however the level of statistical significance. Similarly, there was a trend to fewer major cardiac events with DS (DS 16.8%, PB 21.6%). CONCLUSIONS: We conclude that direct stenting is at least as safe and efficacious as balloon dilatation followed by provisional stent implantation, but failed to reduce restenosis rate or improve outcome within 6 months. Larger prospective randomized trials are required to assess the potential of direct stenting to reduce restenosis rate and improve clinical outcome in subgroups of patients.

What range of programmable AV delays is necessary in antibradycardia DDD stimulation?

DDD pacemakers differ considerably in device specific extents of AV delay (AVD) programmability. To demonstrate the requirements of a mean DDD pacemaker patient population optimal AVDs in 200 DDD pacemaker patients (age 8 to 91 years) were estimated by left atrial electrography. The results should help to define an AVD programmability standard. Left atrial electrograms were recorded via a bipolar filtered esophageal lead. The method aims on adjusting the left atrial electrogram to 70 ms prior to the ventricular spike, both during VDD and DDD operation of the pacemaker. In atrial sensed stimulation the optimal AVD varied from 40 to 205 ms (100.5 +/- 24.5 ms) and in atrial paced stimulation from 85 to 245 ms (169.1 +/- 24.5 ms). The difference of the mean values is statistically significant (p < 0.001). The difference between both values in the individual patient, the individual AVD correction time, varied from 0 to 170 ms (68.7 +/- 26.6 ms). Thus, from our findings requirements on AV delay programmability standard can be derived: AVDs (1) should have a range from 40 to 250 ms, (2) should be independently programmable during atrial sensed and atrial paced operation, and (3) should provide as nominal settings 100 ms for atrial sensed and 170 ms for atrial paced stimulation.

[The standard ECG: did its significance change?]. / Standard-EKG: heutiger stellenwert?

Since introduction of electrocardiography as a clinical method its significance varied. In investigating atrial changes, ventricular hypertrophies and pericardial diseases imaging methods became superior to the ECG. In the diagnosis of coronary artery disease the significance of the standard ECG is different according to clinical picture and stage. Nevertheless it is indispensable in situations with acute ischemia. Knowledge from interventional electrophysiology made interpretations of the standard ECG in conduction disorders and arrhythmias more reliable. Up to now informations gathered from the repolarisation phase in the standard ECG are growing.Thus, despite a change of its significance within partial aspects of cardiology the nearly 100 year old clinical method of electrocardiography as standard ECG of to day is still of high practical value.

[Selection of the optimal pacemaker - Are age and secondary disease related health conditions significant?]. / Indikationsgerechte Wahl des Schrittmachers - Welche Bedeutung haben durch Alter und Zweitleiden bedingte Zustände?

UNLABELLED: In pacemaker statistics a dichotomy exists between the theoretically possible and the actually implanted number of physiological pacemakers. Hence, the aim of the study was to investigate the influences of age and non rhythm related health conditions on the selection of the pacemaker system.In 468 pacemaker patients the arguments for mode selection at first implantation were listed prospectively during a period of 3 years and 9 months. Mode selection followed electrocardiographic (recommendations of the German working Group on Cardiac Pacing), clinical (incidence of only intermittent bradycardias, stage of the underlying cardiac or of a second noncardiac disease) and sociomedical (non rhythm related general heath condition) aspects. Regarding the ECG findings physiological pacing was possible in 329 cases. Nevertheless, 57 of them (17.3%) received a VVI(R) system. Analysis of the reasoning leading to this dicision demonstrated that age-related problems and non-rhythm-caused health conditions became superior instead of rhythmologic aspects in 1.0% of all patients (pts) under 70, in 2.7% of all pts between 70 and 79, and in 10.8% of all pts 80 or more years of age. CONCLUSIONS: Beyond the age of 80 years, in about 11% of the pts who need a pacemaker, non-rhythm-related clinical and sociomedical aspects gain priority over the electrophysiologic defect. Thus, complete coincidence of the theoretically possible and the actually implanted number of physiological pacemakers in this age group cannot be attained. Regarding all factors influencing the selection of the pacemaker system 45 to 55% are more realistic.

Exercise induced sympathetic influences do not change interatrial conduction times in VDD and DDD pacing.

Using telemetry, right atrial electrogram (RA), and marker channel of atrial sense events (MA) in combination with the left atrial electrogram (LA), recorded by a filtered bipolar esophageal lead, interatrial conduction during submaximal exercise and at rest was examined in 46 DDD pacemaker patients. The RA-LA and MA-LA conduction times measured in the presence of atrial sensing (VDD) as well as the conduction time SA-LA from atrial stimulus (SA) to LA, determined during atrial pacing (DDD) were found to be individual constants independent of exercise induced sympathetic influences. Thus, having determined an optimal mechanical interval (LA-LV)mech/opt from left atrium to ventricle by other methods, the optimal AV delay for DDD as well as for VDD operation can be calculated by the sum of the appropriate interatrial conduction time (SA-LA, respectively MA-LA) and the (LA-LV)mech/opt interval. Due to the constant SA-LA and MA-LA, the difference between these two values (AV delay correction interval) is a constant as well, which remains unchanged during exercise. Therefore, in selecting the rate responsive AV delay, only hemodynamic and not electrophysiological measurements need to be considered.

[Anticoagulation: assessment of benefits and risks]. / Antikoagulation: Abwägung von Nutzen und Risiko.

Thromboembolism is a frequent complication of atrial fibrillation. As could be demonstrated by several placebo-controlled prospective studies in the recent years the rate of thromboembolism was reduced significantly by anticoagulation of nearly all kinds of atrial fibrillation. These results are challenging to weigh risks and benefits in every patient. The principles which have to consider in this calculation are discussed with regard to the knowledge derived from the controlled studies.

Right ventricular conductance to establish closed-loop pacing.

Innovations in pacing technology, which include the addition of rate-responsive features to programmable pacemakers, can improve the quality of life of patients suffering from sick sinus syndrome. Among the strategies providing rate-adaptive cardiac pacing, the most attractive is the physiological restoration of closed-loop chronotropic control. This paper describes how autonomic nervous system (ANS) control information is extracted from dynamic measures of myocardial contractile performance obtained from unipolar conductance measurements using the stimulation electrode in the right ventricular cavity. The pacemaker uses the ANS information to modulate pacing rate and restore normal physiological control of heart rate. A new algorithm, regional effective slope quantity (RQ), for isolating the ANS signal was developed. The resulting signal, ventricular inotropic parameter (VIP), is a normalized parameter proportional to the strength of the ANS inotropic signals to the myocardium. The efficacy of the ANS control concept was evaluated in multi-centre studies. Patients with AV block and VIP-controlled pulse generators performed defined exercise protocols. The ANS-controlled pacing rate and the spontaneous sinus rate were closely correlated. Blood pressure and subjective patient reports further indicated that good control of the cardiovascular circulation was achieved.

Autonomic nervous system controlled closed loop cardiac pacing.

A multicenter clinical study is presented, which focuses on the reestablishment of closed loop cardiac control in patients with chronotropic insufficiency. Using the information about sympathetic tone contained in the myocardial contractility, it is possible to reconnect the heart rate to the physiological control mechanisms. Intracardiac impedance is measured with the ventricular electrode and the ventricular inotropic parameter (VIP) is derived from that. The VIP serves directly as input to the control of heart rate by the pacemaker. Over 200 patients have received autonomic nervous system (ANS) controlled pacemakers. The patient-pacemaker system was investigated in different ways. This included standard exercise tests, long-term studies of every day activities over 24 hours, psychological, and pharmacological challenges. To prove the validity of the approach we specifically looked at (1) the appropriateness of changes in paced heart rate with sympathetic tone during exercise, (2) the correlation between heart rate and sinus rate, if detectable, and (3) the correlation between the echocardiographically determined preejection period (PEP) and the VIP controlled heart rate.

[Measuring intracardiac impedance for the determination of sympathetic nerve activity in frequency-adapted electrostimulation--Part 2: Clinical results]. / Intrakardiale Impedanzmessung zur Bestimmung der Sympathikusaktivität bei frequenzadaptiver Elektrostimulation--Teil 2: Klinische Ergebnisse.

The results of a multicenter clinical study involving patients receiving the first ANS controlled rate adaptive pacemaker are presented. In the patients with primary or secondary chronotropic insufficiency, it is possible to reestablish the closed loop control system that includes the baroreceptors, the medulla oblongata, the cardiac output and the mean arterial blood pressure. This system serves to keep the blood pressure constant in the face of changing demands on the circulation. Utilizing intracardiac impedance measurements, the myocardial contractility can be determined, which contains information about the current sympathetic tone, and thus represents an excellent physiological input for a rate adaptive mechanism. The results presented are taken from a study population of over 200 patients. The objective evaluation of this new approach was performed echocardiographically, by ergometry and 24-hour Holter monitoring.

Orthodromic and antidromic pacemaker circus movement tachycardia.

Pacemaker circus movement tachycardia (PCMT) during DDD pacing is usually sustained by retrograde natural and antegrade electronic atrioventricular (AV) conduction. As PCMT is often initiated by a ventricular premature beat (VPB) one method of its prevention is the programming of an atrial stimulus synchronously following a ventricular extrasystole. A patient is described with preserved antegrade, but without retrograde, i.e., VA, conduction. The optional pacemaker mode of synchronous atrial stimulation following a VPB caused an unusual PCMT sustained by retrograde electronic and antegrade natural AV conduction. This PCMT is similar to a natural reentry tachycardia, the most common variety of which (based on retrograde conduction) is termed antidromic and that which we describe is orthodromic.

[Significance of modern therapeutic procedures in long-term treatment of supraventricular tachyarrhythmias]. / Zur Bedeutung der modernen Therapieverfahren bei der Langzeitbehandlung supraventrikulärer Tacharrhythmien.

To get a quantitative statement concerning the significance of modern therapy in supraventricular tachyarrhythmias 200 consecutive patients who were admitted to a coronary unit were analysed retrospectively. Finally accepted treatment were empirical drug therapy in 85 per cent, electrophysiologically controlled medical treatment in 12.5 per cent, pacemaker therapy in 1 per cent, and ablative procedures (catheter ablation and surgical Kent bundle dissection) in 2.5 per cent. As strictly atrial tachyarrhythmias are prevailing and advantages of electrophysiologically controlled drug therapy are not proven, in the majority of cases of supraventricular tachyarrhythmias empirical medical treatment is sufficient. Only in very few cases it is surpassed by the modern procedures. But, nevertheless these modern methods should be known to find the best treatment in problematical cases.