1/66. Demonstration of phase-3 and phase-4 retrograde block in a second concealed accessory pathway after an initial successful radiofrequency ablation of a 'normal' concealed accessory pathway.We report a patient with concealed wolff-parkinson-white syndrome who, following catheter ablation, demonstrated phase-3 and phase-4 retrograde block in a concealed accessory pathway. After an initial 'apparently successful' ablation, retrograde conduction was through the atrioventricular node during constant ventricular pacing. Ventricular extrastimulus testing was performed at a basic drive cycle length of 600 ms. Unexpectedly, ventricular extrastimuli at coupling intervals of 440-380 ms were conducted retrogradely over an accessory pathway, consistent with a phase-3 and phase-4 retrograde block in the accessory pathway. Residual accessory pathway conduction was eliminated in a single ablation session.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
2/66. Severe bradycardia and bradypnea following vaginal oocyte retrieval: a possible toxic effect of paracervical mepivacaine.We report a case of a patient with a history of heart conduction disease, symptom-free and without treatment in the last years, who experienced a severe cardiac complication associated with in vitro fertilization (IVF) with vaginal oocyte retrieval (VOR). Eighty-five minutes after the VOR a severe bradycardia and bradypnea occurred, requiring an emergency application of a pacemaker. Presumably the condition occurred because of a toxic effect of the 400 mg of mepivacaine administered paracervically. It is concluded that in the paracervical anesthesia in the IVF cycles the therapeutic range should be scrupulously followed in patients with heart condition.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
3/66. Second degree entrance block in intermittent ventricular parasystole.In a 21-year-old healthy man, there may be a second degree entrance block occasionally of 2:1 nature resulting in intermittent ventricular parasystole. The refractory period of the ventricular-ectopic (V-E) junction in this case was markedly longer than the ventricular muscle except the V-E junction, but much shorter than the whole length of the parasystolic cycle.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
4/66. His-bundle parasystole masquerading as exercise-induced 2:1 atrioventricular block.We describe a case of symptomatic pseudo-AV block due to His-bundle parasystole masquerading as exercise-induced 2:1 AV block. Electrophysiologic study revealed the presence of His-bundle parasystole, and the fluctuation of parasystolic cycle length could be explained by the concept of modulated parasystole. Modulated parasystole is a possible explanation for maintenance of stable 2:1 AV conduction at an atrial rate of specific range during exercise.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
5/66. Advanced A-V block with apparent A-V junctional escape complexes because of dual A-V nodal pathways.We report a patient with second degree A-V block in whom several sinus impulses were conducted over the slow A-V nodal pathway, resulting in P-R intervals so prolonged to suggest a diagnosis of intermittent advanced A-V block with A-V junctional escape complexes. However, the "escape" cycles were markedly irregular, and moreover, "escape" complexes often occurred with R-R cycles shorter than those ended by conducted sinus beats. These observations suggested that no escape mechanism was present. The marked variability of P-R intervals was a manifestation of dual A-V nodal pathways: short P-R intervals expressed conduction over the fast pathway, whereas long P-R intervals corresponded to sinus impulses conducted over the slow pathway.- - - - - - - - - - ranking = 2keywords = cycle (Clic here for more details about this article) |
6/66. Bigeminal ventricular tachycardia with Wenckebach exit block.A patient is presented in whom repeated attacks of ventricular tachycardia occurred. His last and fatal attack revealed an alternation or coupling of the cycle lengths of the ventricular beats. A large left ventricular wall aneurysm was found, which probably accounted for the unusual arrhythmias.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
7/66. Radiofrequency ablation in a patient with atrioventricular reentrant tachycardia and atrioventricular nodal reentrant tachycardia with 2:1 atrioventricular block.The authors report the case of 15-year-old girl with a history of palpitations and shortness of breath during exercise. The electrocardiogram showed ventricular preexcitation suggesting a wolff-parkinson-white syndrome with a posteroseptal accessory pathway. During the electrophysiological study a left posterospetal accessory pathway was identified and an orthodromic atrioventricular reentry tachycardia was reproducibly induced (cycle length 400 ms). After disappearance of the ventricular pre-excitation with radiofrequency ablation, a dual physiology of atrioventricular node condution was documented and a slow-fast atrioventricular nodal reentrant tachycardia was repeatedly induced. Upon induction, this tachycardia presented a proximal atrioventricular block with 2:1 condution converted to 1:1 condution with overdrive pacing from the proximal coronary sinus (cycle length 270 ms). Radiofrequency ablation of the slow pathway was performed with success. We discuss the need to suspect and seek different arrhythmogenic substracts of tachycardia in a single patient, the electrophysiologic conditions that could explain the inducibility of different arrhythmias in this case, and the controversy regarding ablation of more than one reentry circuit in a single procedure.- - - - - - - - - - ranking = 2keywords = cycle (Clic here for more details about this article) |
8/66. Wenckebach phenomenon in the exit area from a transvenous pacing electrode.An unusual type of exist block from a transvenous pacing electrode was recorded in a 63-year-old man with an acute inferior infarct and cardiogenic shock. The pacemaker artefact to QRS interval increased gradually till there was loss of capture. A gradual change from I:I pacing rhythm to 4:3 and 3:2 Wenckebach cycles was recorded. This was followed by a fixed 2:I pacemaker artefact to QRS block.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
9/66. Sites of entrance block and impulse formation in intermittent atrioventricular junctional parasystole.The Wenckebach phenomenon of entrance block in intermittent atrioventricular junctional parasystole is reported for the first time in a 40-year-old woman. In this case the presence of dual pathways in the atrioventricular junction is demonstrated. One of them is a pathway without conduction disturbance. The other is a pathway containing both the ectopic focus and the site of second-degree entrance block. This site is located a considerably long distance above the focus. Entrance block occurs also at some site below the ectopic focus, which is a part of the pathway containing the focus. It is suggested that entrance block in this lower site might exist during the whole ectopic cycle.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
10/66. Apparent P wave undersensing in a DDD pacemaker post exercise.Wenckebach behavior of DDD pacemakers occurring when the P-P interval varies between the programmed upper rate interval and the total atrial refractory period is symmetrical in a sense that the pacemaker response during atrial rate acceleration is similar to the pacemaker response during atrial rate deceleration. This phenomenon can be observed in all patients with persistent AV block in whom a DDD pacemaker is implanted, during exercise testing when the spontaneous atrial rate exceeds the selected upper rate, i.e., the programmed upper rate interval. However, this phenomenon will not be observed in all patients with intermittent intact AV conduction during exercise. In this case report we describe a patient who showed an asymmetrical response during a bicycle exercise test. There was 1:1 atrial sensing ventricular pacing until the atrial rate exceeded the upper rate of 140 ppm, while atrial sensing was restored during recovery when the conducted sinus rhythm had decreased to 105 beats/min.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
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