[Avoidance of intermittent T-wave oversensing with device programming]. / Vermeidung von intermittierendem T-Wellen-Oversensing durch Programmierung.

We report the case of a 35-year-old man who was suffering from severe heart failure due to cardiomyopathy. He underwent heart transplantation years ago and developed complex ventricular arrhythmias in the following months in combination with recurrent episodes of syncope due to hypertrophic non-obstructive cardiomyopathy in the transplanted heart, so a dual chamber ICD was implanted. Months later repetitive episodes of intermittent T-wave oversensing with consecutive activation of the ICD could be observed. Surgical revision of the electrode was performed and the patient was closely followed up. One year later, further episodes of T-wave oversensing led to multiple inappropriate IDC-shocks. A very short AV-conduction time was programmed to allow ventricular capture whenever possible, because T-wave oversense after ventricular capture would be annotated as single ventricular ectopy not resulting in antitachycardia pacing. As a consequence, the patient was free from inappropriate ICD-shocks, but showed several shorter episodes of T-wave oversensing. They were all initiated by atrial activity that was seen in the refractory period, thus leading to a loss of AV synchrony. Programming a very short post ventricular atrial refractory period (PVARP) in addition to a short AV-delay led to the complete disappearance of T-wave oversensing in this patient. During a 9-month follow-up, no further tachycardia episodes were detected by the device.

Transversal crista terminalis conduction suggests ineffective bidirectional isthmus block.

Catheter ablation of the posterior isthmus is an effective tool to cure typical atrial flutter. In some cases, however, bidirectional block cannot be obtained despite extensive RF applications. Anatomic obstacles or abnormalities are thought to be the most common reasons for failed or prolonged procedures. We present a case of recurrent typical atrial flutter that seemed to be refractory to all ablation attempts in the region of the posterior isthmus although no anatomic abnormalities could be detected. Despite extensive RF application, bidirectional conduction was unchanged. Using a novel noncontact mapping system (En-Site 3000) the existence of a fast conducting gap in the region of the inferior terminal crest was revealed. Rapid conduction over this gap to the opposite side of the isthmus led to the impression that bidirectional isthmus block was not established. As a result no further RF applications were necessary because isthmus block was complete at that time. This is the first time that transverse conduction across the terminal crest could be detected by this novel noncontact mapping system masquerading as unchanged bidirectional isthmus conduction.

Catheter inversion to achieve complete isthmus block in patients with typical atrial flutter.

Endocardial catheter ablation is now considered as the therapy of first choice in highly symptomatic patients with recurrent atrial flutter. Despite of primary success rates between 90 and 100% complete isthmus block is sometimes hard to achieve. We present ablation results of 100 consecutive patients suffering from typical right atrial flutter. After a mean of 18 energy applications persistent bidirectional isthmus block could not be achieved in 16 patients and right atrial angiography was performed in all of them. In 9 patients a large Eustachian valve was detected and considered responsible for failure of endocardial catheter ablation of atrial flutter. Catheter manipulation targeting the anterior region of the Eustachian ridge was successful in all patients after looping the ablation catheter within the right atrium. With a mean of 3 additional RF applications, 6 of the 9 affected patients could be successfully ablated. Large Eustachian ridges are not a rare finding in patients undergoing ablation of typical right atrial flutter. Inversion of the ablation catheter within the right atrium is a simple technique providing excellent tissue contact of the ablation electrode with the anterior region of the Eustachian Ridge. Using this approach, the creation of bidirectional isthmus block is possible in the majority of the respective patients.

Successful catheter ablation of a slow AV-nodal pathway from the left posteroseptal region.

We present the case of a 44 year old woman with recurrent episodes of supraventricular tachycardia due to AV-nodal reentry (AVNRT). She was refractory to conventional medical treatment and referred to our hospital with the view to catheter ablation of the slow AV-nodal pathway. AVNRT of the common type was easily induced performing stimulation from the high right atrium and proximal coronary sinus. Other forms of supraventricular tachycardia were definitely ruled out during further electrophysiologic study. Repetitive RF applications around the right posteroseptal region failed to cure the tachycardia which remained inducible with a typical jump in the AH interval. Extensive RF applications from posteroinferior to the midseptum including the area of the proximal coronary sinus and its os were ineffective as well.AVNRT was transiently but reproducibly eliminated while burns were applied to the high midseptum but AVNRT reoccured within 20 minutes. Finally after retrograde passage of the aortic valve with a 4 mm tip ablation catheter, RF was applied to the left postero to midseptal region. An accelerated junctional rhythm was immediately observed and AVNRT remained non-inducible from that time onwards. It is concluded that an atypical posterior extension of the AV node with predominant leftatrial course might be responsible for this unusual success of slow pathway elimination from left posteroseptal.