1/13. Electrocardiographic observations in bradycardia and tachycardia-dependent atrioventricular block. Relationship to supernormal phase of intraventricular conduction.This report describes the clinical course of a patient with bradycardia and tachycardia-dependent atrioventricular block. bradycardia dependent A-V block (phase 4 block) was transient and precipitated by spontaneous slowing of the sinus rate, atrial and ventricular extrasystoles; The degree of slowing (critical RP interval) required to induce A-V block increased progressively over a three-day period. bradycardia-dependent A-V block was terminated mostly by critically times spontaneous or paced ventricular escape beats, but normally conducted atrial impulses also appeared to restore A-V conduction on several occasions. The tachycardia-dependent component was manifested by an unusual fatigue phenomenon in the His-Purkinje system seen only at an atrial pacing rate of 150 per minute. These observations document the presence of both bradycardia and tachycardia-dependent A-V block in the presence of a normal H-V time and also illustrate the dynamic nature of both phase 4 block and the period of "supernormal" intraventricular conduction.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
2/13. Dissimilar atrial rhythms: coexistence of reentrant atrial tachycardia, atrioventricular nodal reentrant tachycardia and interatrial conduction block.We report a patient in whom mapping of the right atrium with multipolar catheters and electroanatomic mapping revealed the presence of three dissimilar rhythms: a reentrant atrial tachycardia in the antero-lateral wall of the right atrium and an atrioventricular nodal reentrant tachycardia (AVNRT) isolated from each other and a conduction disturbance at the interatrial septum resulting in a rate-related interatrial block and a slow left atrial rhythm. The AVNRT was stopped with intravenous adenosine (6 mg) and induced repeatedly by atrial extrastimuli associated with a critical atrioventricular delay and dual atrioventricular nodal pathways. Electroanatomic mapping disclosed extensive fibrosis isolating viable myocardium of the antero-lateral wall from the rest of the right atrium. The viable myocardium in the antero-lateral wall was activated by a reentrant rhythm circulating around an islet of fibrosis located in the middle of the viable tissue. The AVNRT was ablated by a standard approach and the reentrant atrial tachycardia by producing a linear lesion bridging the central islet of fibrosis with the anterior tricuspid annulus. This case highlights the complicated nature of some dissimilar atrial rhythms and the power of electroanatomic mapping tools to reveal the exact mechanism and guide radiofrequency ablation.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
3/13. Cardiopulmonary complications in multicentric reticulohistiocytosis. Report of a case.Multicentric reticulohistiocytosis (MR) is a rare disease. Only recently was its systemic nature appreciated. It affects the skin, mucous membranes, joints, muscles, tendon sheaths, synovial membranes, bones, liver, kidney, lymph nodes, heart, and lungs. Our patient, a 50-year-old woman, had life-threatening cardiopulmonary complications of MR. The connection between the skin lesions, the arthritis, and the pathologic changes in the heart and lungs is still obscure.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
4/13. Familial occurrence of sinus bradycardia, short PR interval, intraventricular conduction defects, recurrent supraventricular tachycardia, and cardiomegaly.Four members of a family presenting with sinus bradycardia, a short P-R interval, intraventricular conduction defects, recurrent supraventricular tachycardia (SVT), syncope, and cardiomegaly had His bundle studies and were found to have markedly shortened A-H intervals (30 to 55 msec.) with normal H-V times (35 to 50 msec.). Right atrial pacing at rates as high as 170 to 215 per minute failed to increase the A-H or H-V intervals significantly. The data are compatible with the presence of an A-V nodal bypass tract (James bundle) or even complete absence of an A-V node. Ventricular pacing and spontaneous ventricular premature beats resulted in a short ventriculoatrial conduction time (110 msec.) suggesting that if A-V nodal bypass tracts exist, they are utilized in an antegrade and retrograde fashion. None of the features of WPW syndrome was present. The mechanism of syncope in the mother and daughter was intermittent third-degree heart block. Both went on to develop permanent complete heart block despite electrophysiologic studies demonstrating 1:1 A-V conduction at extremely rapid atrial pacing rates and both required implantation of permanent pacemakers. The mechanism of syncope in the two brothers was possibly marked sinus bradycardia, but transient complete heart block has not been ruled out. Permanent pacemaker therapy was recommended for both. The nature of the cardiomegaly, which was mild in three patients, is not known. Although not well documented, several maternal relatives have had enlarged hearts, SVT, complete heart block, and syncope.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
5/13. tachycardia sensing failure of an implantable cardioverter defibrillator in a patient with hypertrophic cardiomyopathy.A 17-year-old white male was found to have nonobstructive hypertrophic cardiomyopathy after suffering three severe syncopal episodes. He experienced an episode of sustained polymorphic ventricular tachycardia during exercise tolerance testing that required cardioversion. Electrophysiological studies were able to reproduce sustained polymorphic ventricular tachycardia that was unresponsive to standard pharmacotherapy. An automatic implantable defibrillator was placed. However, during implantation with the rate sensing electrodes on the left ventricle, it was found that the extremely polymorphic nature of the tachycardia caused such rapid fluctuations in the sensed R wave signal that the device could not properly detect the tachycardia. This was felt to be due to the automatic gain control circuit of the Ventak 1550. The problem was solved by moving the rate sensing electrodes to the lateral right ventricle. This case suggests that the unique arrhythmic substrate of hypertrophic cardiomyopathy may present sensing difficulties during automatic implantable defibrillator insertion.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
6/13. Bidirectional tachycardia induced by herbal aconite poisoning.This report details the clinical, electrocardiographic, and electropharmacological characteristics of an unusual case of bidirectional tachycardia induced by aconites present in a Chinese herbal decoction consumed by a previously healthy subject. The tachycardia showed marked susceptibility to vagotonic maneuvers, cholinesterase inhibition, and adenosine triphosphate. The incessant nature of the tachycardia, rapid recurrence after transient suppression, and failure to respond to direct current cardioversion suggested an automatic tachycardia mechanism consistent with known data on the cellular electrophysiological mechanism of aconitine-mediated arrhythmogenesis. A fascicular or ventricular myocardial origin of the tachycardia with alternating activation patterns, or dual foci with alternate discharge, appeared most plausible. The rootstocks of aconitum plants have been commonly employed in traditional Chinese herbal recipes for "cardiotonic" actions and for relieving "rheumatism." Multiple pitfalls could occur during the processing of these herbs that might have predisposed to aconite poisoning. The need for strict control and surveillance of herbal substances with low margins of safety is highlighted.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
7/13. Unintentional toxicity due to endosulfan: a case report of two patients and characteristics of endosulfan toxicity.Unrestricted use of endosulfan, a cyclic chlorinated hydrocarbon insecticide, results in many intentional and unintentional toxicities in turkey. Due to its chemical stability in the environment, toxicity may be seen even if exposure happens 6-mo after the endosulfan has been sprayed. We discuss a case of 2 patients with unintentional exposure to endosulfan after eating contaminated foods, one of which presented with neurological manifestations and required mechanical ventilation, the other having only mild symptoms. Because of the toxicity to humans and threats for nature, use of endosulfan should be restricted or banned.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
8/13. Pacemaker-driven tachycardia induced by electrocardiograph monitoring in the recovery room.Monitoring devices are known to induce tachycardia in minute-ventilation rate-responsive pacemakers. This is because some monitoring devices measure the same parameter as do the pacemakers (change in thoracic impedance). Hence, the biological signal to the pacemaker is increased and is misconstrued as increased minute ventilation causing tachycardia which resolves when the monitoring device is removed. Whilst this could occur for all minute-volume rate responsive pacemakers, most reported interactions have been with the Telectronics META series. We present a case of an interaction between a Telectronics Tempo DR pacemaker (St. Jude Medical) and an Agilent patient care System (Philips). Failure to recognise the true nature and cause of such tachycardias may lead to mismanagement of the patient, including the inappropriate use of cardio-active medications.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
9/13. arrhythmogenic right ventricular dysplasia. Clinical, electrophysiological, and pathological features.arrhythmogenic right ventricular dysplasia (ARVD) describes the syndrome of recurrent ventricular tachycardia of right ventricular origin and cardiomyopathic changes of the right ventricle. We report the clinical, electrophysiologic, and angiographic characteristics of four patients who presented with ventricular tachycardia of left bundle branch block configuration, and in whom the right ventricular origin of tachycardia was confirmed by endocardial mapping, and a diagnosis of ARVD was substantiated by histological examination. ARVD should be suspected in all patients with ventricular tachycardia of left bundle branch block configuration, especially in young adults with an otherwise normal heart. Once suspected, diagnosis can often be established by non-invasive investigation. Surgical treatment may be difficult because of the diffuse nature of right ventricular involvement.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
10/13. Incessant reciprocating atrioventricular tachycardia. Factors playing a role in the mechanism of the arrhythmia.The case of a patient suffering from incessant supraventricular tachycardia is presented. The electrophysiological study showed the presence of an accessory atrioventricular (A-V) bundle with nodal-like properties and long conduction times. This structure was used as the retrograde arm of the tachycardia circuit. tachycardia was intermittent at rest, but had a sustained character during slight exercise. Administration of atropine and isoproterenol failed to sustain the arrhythmia and spontaneous initiation during sinus rhythm was no longer observed. During handgrip exercise a sustained tachycardia developed immediately. During ventricular stimulation a dual atrial response to a single paced ventricular premature beat was repeatedly observed, proving the availability of two separate A-V pathways for retrograde conduction. The case illustrates the labile nature of this type of accessory pathway, and suggests that autonomic changes can play an important role in the initiation, maintenance, termination, or even spontaneous cure of tachycardia in patients with this anomaly.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
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