1/15. Radiofrequency catheter ablation of common atrial flutter: role of the eustachian valve.INTRODUCTION: During radiofrequency catheter ablation of a common atrial flutter between the tricuspid annulus and the Eustachian valve "septal isthmus", double potentials were recorded along the Eustachian valve, previously described as an anatomical line of conduction block between the coronary sinus ostium and the inferior vena cava. RESULTS: Just before flutter termination, lengthening and beat to beat delay variations between the 2 components of the double potentials were correlated with simultaneous modifications of the flutter cycle length. CONCLUSION: The "septal isthmus" is a common pathway for the flutter wavefront and the impulse generating the second component of the double potential. It is also a good target for flutter ablation.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
2/15. Bystander cavo-tricuspid isthmus activation during post-incisional intra-atrial reentrant tachycardia.We describe a case of post-incisional atrial tachycardia resembling typical atrial flutter on the surface ECG. Typical atrial flutter reentry was ruled out by the results of activation and entrainment mapping. Nevertheless, overdrive pacing from the lateral edge of the cavo-tricuspid isthmus produced tachycardia entrainment with concealed fusion associated with post-pacing and stimulus-to-P wave onset intervals exactly matching the tachycardia cycle length duration and the electrogram-to-P wave onset interval, respectively. Therefore, that site was firstly severed by sequential radiofrequency pulses. However, a transformation of the tachycardia P wave morphology and endocardial activation sequence, not associated with tachycardia termination or cycle length modification occurred. After additional mapping manoeuvres, a relatively small reentrant circuit was identified in the low and mid aspect of the lateral right atrium with the critical isthmus located between the lower border of a cannulation atriotomy and the crista terminalis, close to the inferior vena cava orifice. A single radiofrequency pulse at that site terminated the tachycardia. Both the electrocardiographic pattern and the endocardial mapping data obtained in our case might be explained by a split of the reentrant wavefront into a secondary wavelet which freely propagated through the cavo-tricuspid isthmus without completing the peritricuspid loop. In conclusion, bystander cavo-tricuspid isthmus activation during atrial tachycardia may simulate a typical atrial flutter pattern on the surface ECG. Further studies should evaluate the prevalence of this propagation pattern in post-incisional atrial reentry and atypical atrial flutters, and identify its implications for ablation strategy.- - - - - - - - - - ranking = 2keywords = cycle (Clic here for more details about this article) |
3/15. High-resolution mapping of tachycardia originating from the superior vena cava: evidence of electrical heterogeneity, slow conduction, and possible circus movement reentry.Superior Vena Cava Reentry. High-resolution mapping of a tachycardia originating from the superior vena cava (SVC) in a patient with atrial fibrillation is described. Unidirectional circuitous repetitive activation encompassing the full tachycardia cycle length was documented around a line of block within the myocardial sleeve of the SVC. Intermittent conduction to the right atrium resulted in an irregular atrial tachycardia. Evidence of electrical heterogeneity and slow conduction persisted in sinus rhythm and was exaggerated by premature stimulation but did not reproduce the activation pattern during tachycardia. All the available evidence is best compatible with circus movement reentry within the SVC, with marked slow and anisotropic conduction responsible for the restricted dimensions of the reentrant circuit. These findings may suggest a similar substrate and arrhythmia mechanism in the myocardium of the pulmonary veins.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
4/15. Dual-loop intra-atrial re-entry tachycardia in a patient with ischaemic cardiomyopathy.A 65-year-old man with ischaemic cardiomyopathy (three prior coronary artery bypass surgery procedures), underwent catheter ablation for recurrent atrial flutter. Electrophysiological study initially revealed clockwise, tricuspid annulus/inferior vena cava isthmus dependent, atrial flutter. During radiofrequency energy ablation atrial flutter changed into a different atrial tachycardia without change in cycle length or interruption of the tachycardia. The new tachycardia was a right atrial free wall re-entry tachycardia. Thus the two atrial tachycardias formed a dual-loop ('figure-of-eight') re-entry circuit, possibly due to atrial scar tissue from multiple cardiac surgery procedures.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
5/15. Alternating duration of ventricular paced cycles during automatic mode switching of a DDDR pacemaker.This report describes the response of a Vitatron diamond II DDDR pacemaker to atrial flutter in a patient who developed alternating duration of the ventricular paced cycles during automatic mode switching to the DDIR mode. This device activates mode switching on a beat-to-beat basis and exhibits "ventricular hysteresis" in the DDIR mode when an atrial sensed event is detected during the period corresponding with the AV delay prior to emission of the ventricular stimulus. Such unusual behavior must not be interpreted as pacemaker malfunction.- - - - - - - - - - ranking = 5keywords = cycle (Clic here for more details about this article) |
6/15. Mode switching failure during atrial flutter: the '2:1 lock-in' phenomenon.AIMS: To evaluate incidence and mechanism of a special form of automatic mode switching (MS) failure in patients with atrial flutter. methods AND RESULTS: Retrospectively the charts of 134 patients implanted with dual chamber pacemakers with MS algorithms were reviewed. Seven patients (5.2%) were identified that presented with sustained rapid ventricular pacing resulting from atrial flutter with failure of automatic MS. Since this form of MS failure implies 2:1 tracking of atrial flutter, it was coined '2:1 lock-in'. A theoretical timing model was developed to clarify the mechanism of this special form of MS failure. Prerequisites for the '2:1 lock-in' phenomenon are: (1). the sum of the AV delay and the post ventricular blanking (PVAB) must be longer than the cycle length of the atrial flutter, (2). the tachycardia detection rate must be higher than half the atrial flutter rate and (3). the maximum tracking rate (MTR) must be higher than half the atrial flutter rate. Recommendations for programming in order to avoid this specific form of MS failure are made accordingly and parallel algorithms for flutter detection are discussed. CONCLUSION: '2:1 lock-in' is a typical form of MS failure in patients with atrial flutter and the mechanism is closely linked to the typical atrial sensing windows.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
7/15. Electrical disconnection of an arrhythmogenic superior vena cava with discrete radiofrequency current lesions guided by noncontact mapping.This case describes a 54-year-old patient with paroxysmal atrial fibrillation and atrial flutter. Conventionally recorded local electrogram demonstrated a cycle length of 245 ms in the SVC which was conducted to the right atrium in a 2:1 fashion. The analysis of the virtual unipolar local electrogram from the noncontact mapping system demonstrated slow conduction between SVC and right atrium orthogonal to the atrial breakthrough in the upper part of the crista terminalis. RF ablation at the atrial breakthrough induced the electrical disconnection between the CVC and the right atrium.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
8/15. Superior vena cava flutter: electrophysiology and ablation.INTRODUCTION: Reentry within a major thoracic vein has been suggested as a cause of atrial arrhythmias. However, little is known about these potential reentrant circuits. methods AND RESULTS: Atypical atrial flutter was induced and mapped in 67 out of 225 atrial flutter ablation procedures. Reentry around the superior vena cava (SVC) was suspected in three patients. The suspected SVC flutter was induced and terminated by pacing in all patients. Fusion was demonstrated during flutter entrainment by subeustachian isthmus pacing in all of them. The postpacing interval following entrainment by pacing from different sites of the right atrium (RA) or coronary sinus was longer than the flutter cycle length. Macroreentry within the SVC was demonstrated both by sequential activation and a postpacing interval matching the flutter cycle length when pacing from different sites around the SVC in all patients. Atrial-venous-atrial electrogram sequence was demonstrated following flutter entrainment by atrial pacing. Flutter was terminated by an electrical stimulus delivered to the SVC, which was not propagated to the trabeculated RA, in one patient, and linear radiofrequency application from the distal SVC to the posterior wall of the RA, or to the superoseptal portion of the crista terminalis, in the other two. CONCLUSION: Macroreentry within the SVC is a distinctive mechanism responsible for rapid atrial activation, which is different from other reported flutter mechanisms, such as upper loop reentry. SVC longitudinal radiofrequency application can eliminate the arrhythmia without the need for complete electrical disconnection of the vein.- - - - - - - - - - ranking = 2keywords = cycle (Clic here for more details about this article) |
9/15. The mechanism of flutter interval alternans.The mechanism of atrial flutter alternans was investigated by observing the effects of ventricular systole on flutter intervals in a patient with atrioventricular dissociation. Interval measurements were made both from atrial electrograms recorded from an esophageal electrode, and from surface ECG recordings. Flutter cycle intervals that occurred during a well-defined period subsequent to ventricular systole were consistently prolonged by up to 30 msec relative to the baseline flutter cycle interval. This prolongation was observed in two vastly different electrode configurations, implying that motion artifact was not predominantly responsible. We concluded that, by altering the characteristics of the flutter reentry circuit, transient increases in atrial volume and/or pressure arising during ventricular systole were responsible for the lengthening of the flutter cycle intervals.- - - - - - - - - - ranking = 3keywords = cycle (Clic here for more details about this article) |
10/15. Noninvasive diagnosis and treatment of atrial flutter utilizing previously implanted dual chamber pacemaker.patients with previously implanted dual chamber pacemakers (PM) may develop atrial flutter (AFL). The Siemens-Pacesetter AFP and Genesis PM have the capability of noninvasively synchronizing to a standard external electrophysiology (EP) stimulator. Any arrhythmia termination or induction protocol may be used with a refractory period limitation of approximately 127 msec (472 ppm). The PM stimulation sequence is directly controlled by the APS Model 370EP Programmer which acts as an interface between the PM and EP stimulator. All testing is conducted with the PM functioning in a single chamber mode. The external EP stimulation is detected by the programmer and a 37 KHz coded radio frequency transmission is used to control the PM stimulation in a 1:1 fashion. Real-time intracardiac electrograms (IEG) can be recorded from either the atrial (A) or ventricular lead. The IEG can be used for: (1) hard-copy for diagnosis and cycle length determination; (2) monitoring during and after the procedure; and (3) a synchronization signal to the EP stimulator. Two patients presented with three episodes of AFL with A rates ranging from 220-290 bpm. An A-IEG was obtained in each case to document the exact rhythm and rate. Rapid A pacing from 300-340 ppm was accomplished using a standard external rapid A pacemaker in concert with the 370EP programmer and PM. In two episodes, the AFL accelerated to transient A fibrillation followed by spontaneous conversion to sinus rhythm (SR). In the other episode, the AFL converted directly to SR.(ABSTRACT TRUNCATED AT 250 WORDS)- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
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