Die Rate an Zusatzeingriffen beim Defibrillatoraustausch liegt bei 21,5% (20 von 93 Patienten). Der implantierende Arzt muß also in mehr als einem Fünftel aller Patienten, die zum Austausch anstehen mit einem Zusatzeingriff rechnen und die Patienten entsprechend aufklären. Es ist zu erwarten, daß Sondenprobleme zunehmen, je länger die Sonden implantiert sind.

Metallic vascular endoprotheses (stents) have been introduced clinically to help to retain or to restore a patent vascular lumen after balloon angioplasty and to improve long-term patency of vessels. Despite the widespread use of intracoronary stents, instent restenosis remains a major clinical problem. During the last years considerable research effort had been spent on the understanding of the pathophysiology of restenosis and developing strategies to prevent this major shortcoming of PTCA and stent implantation. The current review focuses in its first part on basic pathophysiological mechanisms, which are involved in the formation of restenosis after ballon angioplasty and stent implantation. In the second part different animal models are presented, which serve as experimental models for examining these processes and testing strategies for the prevention of restenosis. Advantages and disadvantages of each model will be discussed, which are important when transferring results from animal models to clinical practice. Bewertung koronarer Stents im Tiermodell: Ein Überblick Stents sind Metallgefäßstützen, die bei koronarer Herzerkrankung in verengte Gefäßabschnitte implanitiert werden. Dadurch soll einem Gefäßverschluß vorgebeugt und ein ausreichender Blutfluß in den Koronargefäßen sichergestellt werden. Obwohl durch die Einführung der Stents ein großer Fortschritt in der interventionallen Kardiologie erreicht werden konnte, kommt es in bis zu 30 % der Patienten zu einer Wiederverengung im behandelten Gefäßsegment, welche Restenose genannt wird. Die vorliegende Übersichtsarbeit befaßt sich in ihrem ersten Teil mit pathophysiologischen Mechanismen, die ursächlich für die Wiederverengung des Gefäßes verantwortlich gemacht werden. Im zweiten Teil werden verschiedene Tiermodelle vorgestellt, die in der experimentellen Forschung als Restenose-Modelle dienen. Es werden Vor- und Nachteile der einzelnen Tiermodelle dargestellt, die bei der Interpretation der Ergebnisse im Hinblick auf eine Übertragbarkeit auf den Menschen von Relevanz sind. Es wird die Frage diskutiert, welche Ursachen dafür verantwortlich gemacht werden können, daß sich Behandlungskonzepte der Restenose, die sich im Tiermodell als wirksam erwiesen haben, beim Menschen wirkungslos zeigten.

BACKGROUND The effects of fibrillation/defibrillation episodes (FDEs) during defibrillator implantation on myocardial metabolism were investigated at various defibrillation energies in patients with different cardiac pathologies. METHODS Myocardial lactate extraction (MLE) was examined during defibrillation threshold (DFT) testing in patients with either coronary artery disease (CAD, n = 20) or non-ischemic cardiomyopathy (CM, n = 10). Defibrillation pulses were released 15 seconds after induced fibrillation. A test cycle of four FDEs separated by 2-minute intervals was applied in each case. RESULTS Mean MLE decreased significantly from 28 +/- 4% before FDEs to 8 +/- 5% immediately after all episodes in CAD patients, but recovered to 27 +/- 7% within 2 minutes even in patients with reduced left-ventricular function. In patients with CM mean MLE decreased markedly from 29 +/- 3% to -11 +/- 3% immediately after each FDE but increased to baseline (33 +/- 8%) within the recovery period. MLE changes were independent of defibrillation energy in all cases. CONCLUSIONS Myocardial lactate production, suggesting cardiac ischemia, was observed in patients with CM, but not in patients with CAD. But recovery of myocardial lactate extraction was not faster in CAD patients, indicating that the fixed FDE cycle used was well tolerated by all patients.

The benefit of DDD(R) pacing is proven even in patients with intermittent atrial fibrillation. Atrial fibrillation developing during dual chamber pacemaker implantation creates a difficult problem. Maneuvers to reestablish a stable atrial rhythm often are required if atrial fibrillation sets in. This study was performed to determine if atrial lead placement can be performed with acceptable long‐term results in the presence of atrial fibrillation. Twenty‐one patients in whom atrial fibrillation developed during permanent pacemaker implantation were included in this study. In 12 patients, episodes of intermittent atrial fibrillation had been documented before the procedure. Screw‐in leads were used in 15 patients and J‐shaped passive fixation leads in 6 patients. AH leads were bipolar. The intraoperative atrial fibrillation electrogram amplitudes ranged from 0.9 to 3.2 mV (mean 1.8 ± 0.6 mV). One patient required lead revision due to a high atrial pacing threshold after conversion to SR. One patient remained in atrial fibrillation at 3‐month follow‐up. The other 20 patients converted to SR, 11 of whom had intermittent atrial fibrillation with successful mode switch activation. P wave amplitudes were 2.8 ± 6 mV (range 1.4 to 4.0 mV) after conversion to SR. The mean atrial pacing threshold was 1.1 ± 0.5 V (range 0.5 to 3.5 V). Placement of atrial leads in patients who develop atrial fibrillation during pacemaker implantation is feasible; fibrillatory electrogram amplitudes showed a good correlation with the atrial signal after conversion to an organized atrial rhythm (r = 0.698). Acceptable atrial pacing thresholds can be expected as well.

Intraoperative testing with several fibrillation/defibrillation episodes (FDEs) is routiinely performed during defibrillator implantation. Testing is considered safe even in patients with severe cardiac impairment, provided the recovery timespans and number of FDEs are adapted to the individual patient. Myocardial lactate extraction (MLE) was examined in two testing protocols. In 30 patients with coronary artery disease defibrillator implantations were performed under intravenous anesthesia. A percutaneous catheter was positioned into the coronary sinus(CS) under fluoroscopy. Two groups were randomly formed: group A (n = 20, mean number of FDEs: 4.2/patient) with 2 minutes waiting time between FDEs, and group B(n = 10. mean number of EDEs 4.1/ patients) with 10 minutes between FDEs. Defibrillation pulses were released 15 seconds after T wave shock induced fibrillation. To estimate MLE. arterial and CS blood samples were collected before and after each FDE. After the last FDE, samples were obtained after 5, 10, and up to 20 minutes. In group A, MLE fell from a baseline value of 29.6%± 3.6% before the FDEs to 7.8%± 5.4% immediately after the episodes. MLE recovered to 27.2%± 6.5% within 1 minute and overshot to 35.6%± 5.8% within 5 minutes. In group B, MLE decreased from 37.6%± 7.5% to 15.1%± 8.1% immediately after each EDE and rose to its original value (33.6 ± 7.8) within the 5‐minute recovery period. MLE decreased immediately after each FDE, and recovered within 1 minute even in poor left ventricular function. For full MLE recovery a 2‐minute wait between episodes is sufficient, if the total number of FDEs does not exceed four.

We have compared the expression of protein kinase C (PKC) activity and immuno‐detectable isoenzymes in cytosolic and membrane extracts of rat and human cardiovascular tissues (heart, kidney, aorta, saphenous vein). Experiments were performed in raw extracts and upon combined diethylaminoethylcellulose (DEAE) and phenylsepharose column chromatography. PKC activity that bound to DEAE mostly eluted with 200 mm NaCl. DEAE‐purified PKC from all tissues except rat kidney bound almost quantitatively to phenylsepharose and eluted with 0.5–0 m NaCl. Immunoblots with an antibody against classical PKCs and the activator profile for phosphatidylserine, diolein and Ca2+ revealed that the PKC from rat kidney, which did not bind to phenylsepharose, was most probably due to a proteolytically‐generated, constitutively active PKC which is not under the control of a regulatory subunit. Studies in the reference tissue, rat brain, demonstrated that all PKC isoenzymes investigated (classical PKCs α, β, γ, new PKCs δ, ε, ζ, θ, and atypial PKCs ζ, λ, ι) have similar DEAE and phenylsepharose chromatography elution profiles. In the functional assay an inhibitor of all known PKC isoenzymes, bisindolylmaleimide, and a specific inhibitor of classical PKCs, Gö 6976, both inhibited PKC from rat brain completely and with high potency indicating that the functional assay preferentially detects classical PKC isoenzymes. Each PKC isoenzyme had a tissue‐specific expression profile which was similar in rat and man. The classical PKCα, the new PKCs δ and ε and all atypical PKCs were detectable in most tissues, whereas the PKCβ and PKCγ were not detected in any pheripheral tissue; PKCζ and PKCθ were found in some tissues. We conclude that combined DEAE and phenylsepharose chromatography is useful to enrich and detect PKC isoenzymes; no major species differences in tissues‐specific expression patterns appear to exist between rat and man. British Journal of Pharmacology (1997) 120, 177–186; doi:10.1038/sj.bjp.0700877

Subpectoral (SP) implantation of ICD shells is now feasible in nearly all patients because of reduced case dimensions. The course of 101 patients who received a pectoral ICD system was compared with the course of patients who had the system implanted abdominally. Hematomas were rather frequent (6%) in the SP group, despite careful muscle dissection and use of a closed suction device. Early pocket revision may actually avoid infections.

The clinical efficacy and safety of two different implantable cardioverter/defibrillator system with [VENTAK PRx III 1721, Hot Can (HC)] and without [VENTAK PRx III 1720, Cold Can (CC)] electrically active housing were prospectively evaluated in 13 European centers. Devices were subpectorally implanted using single lead systems. 93 patients were included and randomized to either HC (n=48) or CC (n=45) configurations. Underlying heart disease and arrhythmias were similar in both groups. At time of implantation, defibrillation threshold (DFT), defined as the lowest energy to convert induced ventricular arrhythmia, was low (< 10 J), but not significant different between the groups. In a subgroup of 29 patients, DFT at predischarge was significantly lower with HC than with CC.

The aim of this study was to examine the influence of different incubation media on the morphology of the endothelium of great saphenous vein grafts and establish a suitable scoring system for the evaluation of damage caused by these media. Fifty specimens of saphenous veins from ten patients during elective aorto-coronary bypass surgery were used. Ten specimens served as controls; the others were assigned to test groups and exposed to heparinized whole blood, Bretschneider's HTK, human albumin or Ringer's solution. Specimens exposed to heparinized blood showed only slight morphological alterations, whereas the other three mediums caused severe damage. Thus, heparinized blood seems to be most suitable as a rinsing and incubation medium. A widely accepted scoring system for the quantification of endothelial damage caused by the incubation media did not adequately reflect the morphology alterations in the cytoskeleton and membrane topology. The proposed scoring system, which is based on endothelial cell separation, endothelial cell loss, amount of deposits, endothelial cell surface homogeneity, in addition to the frequency of spikes and blebs, seems to be suitable for characterizing differences in endothelial morphology.

Pacing and sensing failure in apical right ventricular coil electrode PCD implantation due to ventricular scars or aneurysma may force the implanting surgeon to switch to more invasive procedures such as subxyphoidal pericardiotomy or thoracotomy for epimyocardial corkscrew electrode and for epicardial patch application. In order to avoid this more invasive operation in the most severely impaired patients, right ventricular outflow tract positioning of the RV electrode is suggested as an alternative RV electrode site for implantation. A study of four cases shows that this occasional procedure is a practicable method to avoid more invasive techniques. Excellent pacing, sensing, and defibrillation characteristics were obtained and application is relatively simple.

A significant proportion of early graft occlusions after aortocoronary revascularization using autologous saphenous vein grafts (SVG) are due to mechanical and/or metabolic or biochemical endothelial lesions. The morphological examination of the endothelium, usually carried out using light microscopy or by various types of scanning electron microscopy (SEM), does not give any indication of the functioning of the endothelium (E). Functionally intact E is capable of producing endothelium-derived relaxing factor (EDRF); a practicable in vitro test is the relaxation of pre-contracted vein segments (VS) in response to acetylcholine (ACh) application. To study the effect of the solution used to rinse and store the SVG between removal and implantation on the functional characteristics of the E, we performed in vitro tests on macroscopically intact VS removed from the saphenous vein of 30 male patients who underwent elective CABG surgery. Isolated VS rings were incubated for 60 min in heparinized whole blood (HWB), Bretschneider's cardioplegic solution (HTK), human albumin solution (HAS), or Ringer's solution (RS) and compared with the results obtained immediately after the removal of untreated control samples (C) taken from the same patients. After equilibration in carbogen aerated Krebs-Henseleit solution and precontraction by 3 x 10(-7) M noradrenaline (NE), relaxation induced by 10(-6) M ACh was measured. Only the samples stored in HWB (13.4 +/- 0.4 mN) showed similar maximal contractions with NE to those in the control group (14.4 +/- 0.5 mN), i.e. all those segments which showed both contractions with NE and relaxation with ACh.(ABSTRACT TRUNCATED AT 250 WORDS)

Krebsleiden bedingen in ihrem Verlaufe eine Vielzahl von Sekundärproblemen, wovon einige deshalb besondere thoraxchirurgische Bedeutung erlangt haben, da sie entweder im therapeutischen Gesamtkonzept kurativ beseitigt oder unter palliative Gesichtspunkten zur Verbesserung der Lebensqualität des Kranken gelindert werden können.