Glioneuronal tumor with ATRX alteration, kinase fusion and anaplastic features (GTAKA): a molecularly distinct brain tumor type with recurrent NTRK gene fusions

Glioneuronal tumors are a heterogenous group of CNS neoplasms that can be challenging to accurately diagnose. Molecular methods are highly useful in classifying these tumors-distinguishing precise classes from their histological mimics and identifying previously unrecognized types of tumors. Using an unsupervised visualization approach of DNA methylation data, we identified a novel group of tumors (n = 20) that formed a cluster separate from all established CNS tumor types. Molecular analyses revealed ATRX alterations (in 16/16 cases by DNA sequencing and/or immunohistochemistry) as well as potentially targetable gene fusions involving receptor tyrosine-kinases (RTK; mostly NTRK1-3) in all of these tumors (16/16; 100%). In addition, copy number profiling showed homozygous deletions of CDKN2A/B in 55% of cases. Histological and immunohistochemical investigations revealed glioneuronal tumors with isomorphic, round and often condensed nuclei, perinuclear clearing, high mitotic activity and microvascular proliferation. Tumors were mainly located supratentorially (84%) and occurred in patients with a median age of 19 years. Survival data were limited (n = 18) but point towards a more aggressive biology as compared to other glioneuronal tumors (median progression-free survival 12.5 months). Given their molecular characteristics in addition to anaplastic features, we suggest the term glioneuronal tumor with ATRX alteration, kinase fusion and anaplastic features (GTAKA) to describe these tumors. In summary, our findings highlight a novel type of glioneuronal tumor driven by different RTK fusions accompanied by recurrent alterations in ATRX and homozygous deletions of CDKN2A/B. Targeted approaches such as NTRK inhibition might represent a therapeutic option for patients suffering from these tumors.

Feasibility of preprocedural LAA occluder sizing

Background

Implantation of occluders in the left atrial appendage (LAA) has been established to prevent patients with atrial fibrillation (AF) from stroke and embolisation. Currently, the individual occluder sizing will be done intraprocedurally using fluoroscopy and/or transesophageal echo (TEE) imaging.

Purpose

Development of a new approach allowing preprocedural occluder sizing and its validation by conventional intraprocedural methods.

Methods

The CARTO electro-anatomical mapping system was used in 62 consecutive patients (40 m, 22 f, age: 69.8±8.4 years) to preprocedurally predict the size of Watchman (n=34) or Amplatzer Amulet (n=28) devices. During device implantation, 23 of the patients (37.1%) were in AF. LAA morphologies were Chicken Wing (40.0%), Cauliflower (31.7%), Windsock (20.0%) and Cactus (8.3%). CHA2DS2-VASc Score was 3.7±1.9 and HAS-BLED-Score was 3.6±1.3. Preprocedurally, routine cardiac CT scans were imported into the CARTO segmentation tool for segmentation of the left atrium. The resulting volume images (VI) and slice images (SI) were adjusted in their 3-dimensional orientation to fit the manufacturer's sizing recommendations. Subsequently, the match between pre- and intraprocedural sizing was compared with the actually implanted device size.

Results

In the Watchman group, preprocedural VI corresponded with 38.1% (8/21) and SI with 42.3% (11/26), while intraprocedural fluoroscopy corresponded with 29.6% (8/27) and TEE with 40.0% (12/30) of all actually implanted devices. According to clinical routine an aberration of one size is common practice. After including one additional size to the estimation, VI corresponded with 81.0% (17/21), SI with 84.6% (22/26), while fluoroscopy corresponded with 85.2% (23/27) and TEE with 80.0% (24/30) of all actually implanted occluders.

In the Amplatzer Amulet group, VI corresponded with 37.0% (10/27), SI with 57.1% (16/28) and fluoroscopy with 71.4% (20/28) of all actually implanted devices. After including one additional size to the estimation, VI corresponded with 66.7% (18/27), SI with 85.7% (24/28) and fluoroscopy with 100% (28/28) of all actually implanted occluders. The remaining were selected empirically.

Conclusion

In this study cohort of 62 patients, feasibility of a preprocedural sizing using the CARTO segmentation tool was demonstrated for Watchman occluders providing results comparable with conventional intraprocedural fluoroscopy and/or TEE based intraprocedural sizing. Possibly due to the different manufacturer measuring recommendation, 10 to 12 mm away from the LAA ostium, results for the Amplatzer Amulet system were found to be less accurate. Nevertheless, the proposed approach offers the advantage of preoperative visualisation of the individual LAA anatomy and morphology.

Funding Acknowledgement

Type of funding sources: None.

MODL-11. COMPARISON OF HUMAN & MURINE PA/PXA CHARACTERISTICS

Pediatric low-grade gliomas (pLGGs) are the most common brain tumors in children. Despite recent advances in the molecular characterization of this heterogeneous set of tumors, the separation of specific tumor types is still not fully established. Pilocytic astrocytoma (PA; WHO grade I) and pleomorphic xanthoastrocytoma (PXA; WHO grade II) are two pLGG types that can be difficult to distinguish based on histology alone. Even though their clinical course is different, they are often grouped as ‘pLGG’ in clinical trials (and therefore treated similarly). Based on a cohort of 89 human pediatric tumor samples, we show that PAs and PXAs have clearly distinct methylation and transcriptome profiles. The difference in gene expression is mainly caused by cell cycle- and development-associated genes, suggesting a key difference in the regulatory circuits involved in tumor growth. In addition to BRAF V600E, we found NTRK fusions and a previously unknown EGFR:BRAF fusion as mutually exclusive driving events in PXAs. Both tumor types show marked signs of immune cell infiltration, but with significant qualitative differences, which might represent therapeutic vulnerabilities. To pave the way for further research on PA and PXA, we developed corresponding mouse models using the virus-based RCAS system, which allows introduction of an oncogenic driver into immunocompetent mice for molecular and preclinical research. The murine tumors do not only histologically resemble their human counterparts but also show a similar growth behavior. Expression analysis revealed that the murine PXAs have a stronger gene signature of proliferation and immune cell infiltration compared to PAs.

Infant High-Grade Gliomas Comprise Multiple Subgroups Characterized by Novel Targetable Gene Fusions and Favorable Outcomes

Infant high-grade gliomas appear clinically distinct from their counterparts in older children, indicating that histopathologic grading may not accurately reflect the biology of these tumors. We have collected 241 cases under 4 years of age, and carried out histologic review, methylation profiling, and custom panel, genome, or exome sequencing. After excluding tumors representing other established entities or subgroups, we identified 130 cases to be part of an "intrinsic" spectrum of disease specific to the infant population. These included those with targetable MAPK alterations, and a large proportion of remaining cases harboring gene fusions targeting ALK (n = 31), NTRK1/2/3 (n = 21), ROS1 (n = 9), and MET (n = 4) as their driving alterations, with evidence of efficacy of targeted agents in the clinic. These data strongly support the concept that infant gliomas require a change in diagnostic practice and management. SIGNIFICANCE: Infant high-grade gliomas in the cerebral hemispheres comprise novel subgroups, with a prevalence of ALK, NTRK1/2/3, ROS1, or MET gene fusions. Kinase fusion-positive tumors have better outcome and respond to targeted therapy clinically. Other subgroups have poor outcome, with fusion-negative cases possibly representing an epigenetically driven pluripotent stem cell phenotype.See related commentary by Szulzewsky and Cimino, p. 904.This article is highlighted in the In This Issue feature, p. 890.

The Senescence-associated Secretory Phenotype Mediates Oncogene-induced Senescence in Pediatric Pilocytic Astrocytoma

PURPOSE

Pilocytic astrocytoma is the most common childhood brain tumor, characterized by constitutive MAPK activation. MAPK signaling induces oncogene-induced senescence (OIS), which may cause unpredictable growth behavior of pilocytic astrocytomas. The senescence-associated secretory phenotype (SASP) has been shown to regulate OIS, but its role in pilocytic astrocytoma remains unknown.Experimental Design: The patient-derived pilocytic astrocytoma cell culture model, DKFZ-BT66, was used to demonstrate presence of the SASP and analyze its impact on OIS in pilocytic astrocytoma. The model allows for doxycycline-inducible switching between proliferation and OIS. Both states were studied using gene expression profiling (GEP), Western blot, ELISA, and cell viability testing. Primary pilocytic astrocytoma tumors were analyzed by GEP and multiplex assay.

RESULTS

SASP factors were upregulated in primary human and murine pilocytic astrocytoma and during OIS in DKFZ-BT66 cells. Conditioned medium induced growth arrest of proliferating pilocytic astrocytoma cells. The SASP factors IL1B and IL6 were upregulated in primary pilocytic astrocytoma, and both pathways were regulated during OIS in DKFZ-BT66. Stimulation with rIL1B but not rIL6 reduced growth of DKFZ-BT66 cells and induced the SASP. Anti-inflammatory treatment with dexamethasone induced regrowth of senescent cells and inhibited the SASP. Senescent DKFZ-BT66 cells responded to senolytic BCL2 inhibitors. High IL1B and SASP expression in pilocytic astrocytoma tumors was associated with favorable progression-free survival.

CONCLUSIONS

We provide evidence for the SASP regulating OIS in pediatric pilocytic astrocytoma, with IL1B as a relevant mediator. SASP expression could enable prediction of progression in patients with pilocytic astrocytoma. Further investigation of the SASP driving the unpredictable growth of pilocytic astrocytomas, and its possible therapeutic application, is warranted.

Abstract 5109: Somatic CRISPR/Cas9-mediated gene editing enables versatile brain tumor modeling

Despite substantial advances in the molecular classification of pediatric brain tumors over the last decade, many tumors are still incurable, have a poor prognosis or therapy-related detrimental long term effects. To develop innovative and modern therapy approaches, sophisticated mouse models, faithfully reflecting the human disease are urgently needed.

However, the development of transgenic mouse lines is a time consuming process that is confronted with an increasing number of candidate genes resulting from next generation sequencing of tumor specimens. To cope with this discrepancy, more adaptable animal models are needed. Using somatic gene transfer to manipulate cells in situ holds great advantages in terms of speed and flexibility.

We therefore established a system in which we are using the CRISPR/Cas9 system for somatic disruption of candidate tumor suppressor genes (TSGs) in combination with transposon-mediated overexpression of candidate oncogenes to induce murine brain tumors. By deleting Ptch1 in murine cerebella, we induced Sonic Hedgehog (SHH) subgroup medulloblastoma with high penetrance and short latency. We characterized the induced mutations in depth and did not detect recurrent off-targets using unsupervised whole genome sequencing. We further demonstrated that this method is suited to induce other brain tumor entities by targeting multiple TSGs at the same time or by combining TSG targeting with overexpression of certain oncogenes. To date we established five novel mouse models using this system. Two of these resulted from simultaneous deletion of Nf1, Pten and Trp53 or from combining overexpression of a MET fusion with a loss of Trp53, respectively. Both of these combinations led to efficient glioblastoma induction in the murine forebrain. Our results demonstrate a fast and flexible system for validating novel candidate genes and for generating faithful animal models of human cancer.

Citation Format: Marc Zuckermann, Britta Ismer, Volker Hovestadt, Christiane B. Knobbe-Thomsen, Marc Zapatka, Paul A. Northcott, Martine F. Roussel, Guido Reifenberger, Peter Lichter, Stefan M. Pfister, Daisuke Kawauchi, Jan Gronych, David T. Jones. Somatic CRISPR/Cas9-mediated gene editing enables versatile brain tumor modeling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5109.

Interactive In-Vitro Training In Physics Of Radiofrequency Ablation For Physicians And Medical Engineering Students

Radiofrequency (RF) ablation requires a complex set of devices as well as profound electrophysiological experience and substantial knowledge of physical science basics. To establish RF ablation in-vitro teaching-system, six workstations were equipped with computer-controlled RF ablation generators. Universal connection boxes allow ablation-essays with catheters of different make and model. Special wetlabs were developed combining a basin containing isotonic saline solution with a thermostat and a pump to simulate blood flow. This hands-on teaching system can be used to demonstrate differences in lesion-forming dependent on tip-electrodes, sensor technology and ablation techniques, influence of blood flow and electrode-angle to the myocardium. It was also utilized to reproduce industrial in-vitro tests.

Local Application of Isogenic Adipose-Derived Stem Cells Restores Bone Healing Capacity in a Type 2 Diabetes Model

Bone regeneration is typically a reliable process without scar formation. The endocrine disease type 2 diabetes prolongs and impairs this healing process. In a previous work, we showed that angiogenesis and osteogenesis-essential steps of bone regeneration-are deteriorated, accompanied by reduced proliferation in type 2 diabetic bone regeneration. The aim of the study was to improve these mechanisms by local application of adipose-derived stem cells (ASCs) and facilitate bone regeneration in impaired diabetic bone regeneration. The availability of ASCs in great numbers and the relative ease of harvest offers unique advantages over other mesenchymal stem cell entities. A previously described unicortical tibial defect model was utilized in diabetic mice (Lepr(db-/-)). Isogenic mouse adipose-derived stem cells (mASCs)(db-/db-) were harvested, transfected with a green fluorescent protein vector, and isografted into tibial defects (150,000 living cells per defect). Alternatively, control groups were treated with Dulbecco's modified Eagle's medium or mASCs(WT). In addition, wild-type mice were identically treated. By means of immunohistochemistry, proteins specific for angiogenesis, cell proliferation, cell differentiation, and bone formation were analyzed at early (3 days) and late (7 days) stages of bone regeneration. Additionally, histomorphometry was performed to examine bone formation rate and remodeling. Histomorphometry revealed significantly increased bone formation in mASC(db-/db-)-treated diabetic mice as compared with the respective control groups. Furthermore, locally applied mASCs(db-/db-) significantly enhanced neovascularization and osteogenic differentiation. Moreover, bone remodeling was upregulated in stem cell treatment groups. Local application of mACSs can restore impaired diabetic bone regeneration and may represent a therapeutic option for the future.

SIGNIFICANCE

This study showed that stem cells obtained from fat pads of type 2 diabetic mice are capable of reconstituting impaired bone regeneration in type 2 diabetes. These multipotent stem cells promote both angiogenesis and osteogenesis in type 2 diabetic bony defects. These data might prove to have great clinical implications for bony defects in the ever-increasing type 2 diabetic patient population.

Surgical Debridement Is Superior to Sole Antibiotic Therapy in a Novel Murine Posttraumatic Osteomyelitis Model

Introduction

Bone infections after trauma, i.e. posttraumatic osteomyelitis, pose one of the biggest problems of orthopedic surgery. Even after sufficient clinical therapy including vast debridement of infected bone and antibiotic treatment, regeneration of postinfectious bone seems to be restricted. One explanation includes the large sized defects resulting from sufficient debridement. Furthermore, it remains unclear if inflammatory processes after bone infection do affect bone regeneration. For continuing studies in this field, an animal model is needed where bone regeneration after sufficient treatment can be studied in detail.

Methods

For this purpose we created a stable infection in murine tibiae by Staphylococcus aureus inoculation. Thereafter, osteomyelitic bones were debrided thoroughly and animals were subsequently treated with antibiotics. Controls included debrided, non-infected, as well as infected animals exclusively treated with antibiotics. To verify sufficient treatment of infected bone, different assessments detecting S. aureus were utilized: agar plates, histology and RT-qPCR.

Results

All three detection methods revealed massive reduction or eradication of S. aureus within debrided bones 1 and 2 weeks postoperatively, whereas sole antibiotic therapy could not provide sufficient treatment of osteomyelitic bones. Debrided, previously infected bones showed significantly decreased bone formation, compared to debrided, non-infected controls.

Discussion

Thus, the animal model presented herein provides a reliable and fascinating tool to study posttraumatic osteomyelitis for clinical therapies.

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]

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.

[Feasibility and safety of long-term AAI(R) pacing in isolated sinus node syndrome]

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.

[Left ventricular electromechanical latency period is an additional indicator to upgrade from right to biventricular DDD pacing]

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.

Bendamustine, vincristine and prednisone (BOP) versus cyclophosphamide, vincristine and prednisone (COP) in advanced indolent non-Hodgkin's lymphoma and mantle cell lymphoma: results of a randomised phase III trial (OSHO# 19)

PURPOSE

The purpose of this study was to compare the efficacy and toxicity of bendamustine, vincristine + prednisone (BOP) with a standard regimen of cyclophosphamide, vincristine + prednisone (COP) in patients with previously untreated advanced indolent non-Hodgkin's lymphoma (NHL) and mantle cell lymphoma.

METHODS

A total of 164 patients with follicular lymphoma (grade 1/2), mantle cell lymphoma or lymphoplasmacytic lymphoma (immunocytoma) was randomised to treatment with vincristine 2 mg (day 1) and prednisone 100 mg/m2 (days 1-5) + bendamustine 60 mg/m2 (days 1-5) or + cyclophosphamide 400 mg/m2 (days 1-5) for a total of eight 21-day cycles.

RESULTS

The rate of complete remission was 22% with BOP and 20% with COP. The projected 5-year survival rate was 61% with BOP and 46% with COP. The BOP-associated 5-year survival advantage almost reached significance in the subgroup of patients who responded to therapy (74% vs. 56%; P = 0.05), and did reach significance in responders who did not receive interferon maintenance therapy (70% vs. 47%; P = 0.03). Toxicity was acceptable in both treatment groups, although alopecia and leucopenia were more severe with COP.

CONCLUSIONS

Bendamustine can efficaciously and safely replace cyclophosphamide, as used in standard COP therapy, for the treatment of patients with indolent NHL and mantle cell lymphoma. Long-term survival data suggest a clinically significant benefit for patients treated with BOP.

[Perforated mitral valve aneurysm as a rare course of bacterial endocarditis]

A 65 year old man with a history of mechanical aortic valve replacement acquired Enterococcus faecalis mediated infective endocarditis about 3 years later. Transesophageal echocardiography revealed formation of an aneurysm confined to the anterior mitral valve leaflet. The aortic valve revealed no signs of endocarditis by transesophageal ultrasound. With sudden perforation of the mitral valve aneurysm, subsequent hemodynamic deterioration and pulmonary oedema, the patient underwent emergency mitral and aortic valve replacement. The postoperative course was uneventful.

[Acute thrombosis of pelvic and leg veins in agenesis of the renal segment of the inferior vena cava]

A 19-year-old, otherwise asymptomatic man presented to the hospital of orthopaedic surgery with acute severe pain like lumbago. Symptomatic treatment was performed after extensive orthopaedic diagnostic procedures. On the third day after admission he showed clinical signs of deep vein thrombosis with painful swelling and livid discoloration of both legs. Colour duplex ultrasound revealed complete thrombosis of the leg and pelvic veins bilaterally, but the cranial extent was not clear. Contrast-enhanced helical computer tomography of the abdomen and the pelvis confirmed deep pelvic vein thrombosis and showed extension into the inferior vena cava. Moreover, the study revealed the agenesis of the renal segment of the inferior vena cava with collateral flow through dilated lumbar veins to enlarged azygous and hemiazygous, through vertebral and paravertebral venous plexus. The renals were drained via dilated capsular veins. The agenesis of renal vena cava is a very rare anomaly causing acute thrombosis of the deep leg and pelvic veins. Other risk factors of thromboembolic disease were not found. The patient was treated successfully with systemic thrombolysis. Therefore we used ultra-high streptokinase infusion (9 million units over 6 hours). Colour duplex ultrasound revealed good flow into deep leg and pelvic veins after three cycle of lysis. Magnetic resonance angiography of the abdomen and pelvis was performed to evaluate the successful fibrinolysis with complete recanalisation of the pelvic veins and to demonstrate the venous anatomy. Permanent oral anticoagulation with phenprocoumon is indicated to decrease the high rate of recurrent thrombosis. Compression stockings were prescribed. To prevent thrombosis, additional risk factors like smoking, immobilization and unusual physical activity should be strictly avoided.

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.

[Selection of the optimal pacemaker - Are age and secondary disease related health conditions significant?]

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.

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]

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.

[Paroxysmal AV tachycardia in triplets]

It is reported on triplet sisters with paroxysmal tachycardias. Two of them were enzygotic. For the two an AV-node longitudinal dissociation could be proved as cause of the tachycardia. This observation is regarded as proof for the existence of congenital anomalies of the AV-node as a possible cause of its longitudinal dissociation.

[Diagnosis and therapy of bradycardial arrhythmias]

Diagnostic and therapeutic procedures in bradyarrhythmias are discussed. Special attention is paid to cases with suspected but still undocumented bradycardias and to some aspects of differential therapy.

[Identification of the site of block in high degree AV conduction disorders on the surface ECG]

The possibility of identifying the site of block by analysing the surface ECG was studied in 124 patients with 2nd or 3rd degree AV-block. In all cases His-bundle-electrography was performed. With regard to the QRS-duration (both in conducted and in escape beats) and to functional peculiarities of the AV-conduction or of the automatic centres in patients with narrow QRS complexes nearly all cases with the prognostically less favourable His-Purkinje-block are discernible.

[Supplemental device for the electrocardiograph 6 NEK 4 for the recording of esophageal electrocardiograms]

For the analysis of the cardiac rhythm an additional device for recording electrocardiograms of the oesophagus which can be connected with the 6-canal-electrocardiograph 6 NEK 4 was developed. The device works as an ECG-preamplifier with a high reverse of amplification. Using a special filter it is possible to get well evaluable records excluding each zero line drift, even on most difficult conditions. The possibility of connection with any experimental entry of the 6 NEK 4 renders possible the combination of the electrocardiogram of the oesophagus with any ECG standard deviation program.