Zeitschrift für Kardiologie
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The first report about successful radio frequency ablation of a right-posterior-septal accessory pathway appeared in 1986. Since then, the technology of both guidable ablation catheters and radio frequency generators has been considerably improved in an initially clinical-experimental phase. At the same time, electrophysiologists were equally able to enlarge their knowledge in the field of signal characteristics of arrhythmogenic substrates. ⋯ The only exception relates to the ablation of the AV node at accurate diagnosis for pacemaker implantation (VVIR; DDDR switch mode) which has become part of routine therapy, although, of course, atrial fibrillation itself or necessary anticoagulation cannot be abolished. Thus, our center shows a success rate of 98% in treating 117 patients by this method. First promising reports are available describing the attempt of AV node modification in the posterior nodal part with the goal of reducing the ventricular rate in atrial fibrillation.
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Adenosine has potent cardiac electrophysiologic effects including a negative chronotropic action on the sinus node and a predominant negative dromotropic action on the AV node. The latter property has mainly led to the use of adenosine as antiarrhythmic agent for the acute management of paroxysmal supraventricular tachycardia (PSVT) mediated by a reentrant mechanism involving the AV node. The effects of adenosine are dose-dependent and of very short duration since the half-life is less than 10s. ⋯ Adenosine is helpful to detect or to increase preexcitation which is important for planning a catheter ablation procedure since the preexcitation pattern allows to localize the accessory pathway. Since the action of adenosine usually does not alter the accessory pathway conduction it is also useful for control ablation efficacy noninvasively in terms of antegrade conduction and during ventricular pacing for the retrograde conduction. Further evaluation and research is necessary for better understanding of adenosine action on the human atrial electrophysiology since it provokes atrial fibrillation in some patients, and of adenosine action on the different pathways in AV nodal reentrant tachycardias and some accessory pathways with decremental (AV nodal-like) conduction properties.
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Comparative Study
[Low pacing thresholds of ventricular pacemaker leads: not a marker for large R-wave amplitudes and high impedance values].
An optimal position of a ventricular pacing lead in the bottom or apex of the right ventricle is defined by low pacing thresholds and high R wave amplitudes. At similar pacing thresholds high pacing impedance additionally reduces the pacing current delivered by the pacemaker. Finding an optimal position for the pacing lead would be facilitated if locations with low pacing thresholds are usually associated with great R wave amplitudes and high pacing impedance. ⋯ In respect to impedance, neither the correlation with pacing threshold (r = 0.07) nor that with R wave amplitude (r = 0.18) was statistically significant. In conclusion, most patients had pacing thresholds < 0.5 V at 0.5 ms pulse duration and R wave amplitudes > 10 mV; fewer than 5% of the patients had pacing thresholds > 0.6 V or R wave amplitudes < 5 mV. Lead locations with low pacing thresholds are usually not associated with great R wave amplitudes or high impedance.
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Obstructive sleep apnea syndrome (OSAS) is the most important form of sleep-related breathing disorders due to its high prevalence and its potential for developing cardiovascular diseases. The increased morbidity of these patients is explained by the coincidence with cardiovascular diseases, and the increased mortality of untreated patients is due to cardiovascular complications, which depend on the degree of the breathing disorder. Heavy snoring, as a partial obstruction of the upper airways, and OSAS are independent risk factors for the development of cardiovascular diseases and stroke. ⋯ OSAS is frequent in patients with coronary heart disease and these patients must be classified as a particular risk group because of apnea-associated silent myocardial ischemia and electric instability of the myocardium. The occurrence of arrhythmia in patients with OSAS is closely related to the apnea and hyperventilation events and depends on the sympathovagal balance. Early diagnosis and suitable therapy of patients at risk not only abolishes the sleep-related breathing disorder but also improves long-term outcome.
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Aortic dissection without entry and blood-flow in a false lumen was recently identified at necropsy and in vivo as intramural hemorrhage in the aortic wall (IMH). It was the purpose of the study to elucidate clinical signs and prognosis in this rare and poorly understood condition. Among 360 prospectively evaluated patients with clinical suspicion of aortic dissection, 195 patients presented with evidence of aortic disease. ⋯ IMH progression to overt dissection, rupture and/or acute tamponade occurred in 8/25 cases (32%) within 24 to 72 h, indicating the need for urgent surgical repair. The 30-day mortality of IMH inflicting the ascending aorta was 80% (4 of 5) with medical treatment in contrast to none (of 7) with early surgical treatment (p < 0.01). One-year survival was 71% in surgically treated patients and 20% with medical treatment (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)