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Background and Aims: Left bundle branch block (LBBB) is common after transcatheter aortic valve replacement (TAVR) and associated with a left or normal QRS axis. We aim to assess the QRS frontal plane axis shift changes during LBBB after TAVR and determine if the risk of procedure-related high degree atrioventricular block (AVB) is affected by QRS axis shift changes., Methods and Results: In a retrospective single-center study of 720 consecutive patients who underwent TAVR, 141 (19.6%) with normal baseline QRS duration developed a new LBBB after TAVR and constituted the study group. Most patients (59.6%) were females and the mean age of the cohort was 81.2 ± 6 years., Results: As compared with the baseline QRS axis before TAVR, the occurrence of LBBB was associated with a leftward QRS axis shift (by 40 ± 28.3°) in 73% of the study patients and a rightward (by 18.6 ± 19.4°) or no change in QRS axis in 25.6% and 1.4% of the study patients, respectively. A left QRS axis (-30°) was observed in 14.9% and 38.3% of the study patients before and after TAVR, respectively. The group of patients exhibiting a rightward or no QRS axis shift had a greater incidence of high degree AVB than the group of patients exhibiting a leftward QRS axis shift (18.4% vs. 6.8%, p = .056)., Conclusion: Although post TAVR-LBBB is associated with a leftward QRS axis shift in most patients, a non-negligible proportion of patients (27%) exhibited a rightward or no QRS axis shift. The latter group tend to have a higher risk of developing high degree AVB., (© 2023 Wiley Periodicals LLC.)

Background: A few series of focal atrial tachycardia (AT) originating from the noncoronary sinus of Valsalva (NCSV) have been reported in the literature during the last decade., Methods and Results: Of 147 patients with AT referred for radiofrequency ablation (RFA), we identified nine (6%) originating in the vicinity of the NCSV. Clinical AT was induced during electrophysiological study in all patients without (n = 6) and with (n = 3) isoproterenol infusion. Mean cycle length of the induced tachycardia was 399 ± 85 ms. Mapping of the right atrium and of the left atrium (LA) was initially performed in all nine patients and in four patients, respectively. Earliest tachycardia activation occurred at the His bundle area in all cases. Earliest activations in the LA were at the low paraseptal regions. In two patients with antegrade dual atrioventricular (AV) node physiology that rendered difficult accurate distinction between atrial and ventricular activation, slow pathway ablation was necessary. A retrograde aortic approach was used for mapping the aortic cusps. The earliest local atrial activation in the NCSV preceded the atrial activation in the His area in all patients by 27 ± 8 ms. RFA was performed in all nine patients and was acutely successful in eight. Two patients required radiofrequency (RF) energy outputs of 50 W in order to terminate the arrhythmia. In one patient, successful AT ablation was associated with complete AV block requiring implantation of permanent pacemaker., Conclusions: Focal AT can be successfully mapped and ablated in the NCSV. Higher than usual RF energy levels are sometimes required. Complete AV block is a possible complication., (© 2016 Wiley Periodicals, Inc.)

Radiofrequency ablation of right atriofascicular pathways (RAFPs) is frequently complicated by the occurrence of mechanically induced trauma to the pathway by the ablation catheter. Since recording of accessory pathway (AP) potential is critical for achieving successful ablation of RAFP, one may fear that long-lasting mechanically induced trauma to the AP will affect recording of AP potential and thereby adversely affect the procedure outcome. We report a patient with antidromic tachycardia involving an antegrade RAFP. Despite long-lasting catheter trauma to the RAFP, mapping of the tricuspid annulus showed persistent recording of an AP potential that enabled us to continue the procedure and successfully abolish the AP., (©2010, The Authors. Journal compilation ©2010 Wiley Periodicals, Inc.)

Background: Quinidine is very effective in preventing the reinduction of sustained ventricular fibrillation (VF) during electrophysiologic study (EPS) in patients with idiopathic VF and Brugada syndrome. However, there are no data on the long-term reproducibility of this EP efficacy., Methods and Results: Nine patients (seven males and two females, aged 21-72 years), who suffered from aborted cardiac arrest (n = 8) or recurrent syncope (n = 1) due to Brugada syndrome (n = 5) or idiopathic VF (n = 4), comprised the study. All patients had inducible sustained VF at baseline that was prevented by quinidine therapy and underwent another EPS on medication after 1.7-23.6 (9.8 +/- 6.8) years (>5 years in eight patients). Two patients underwent two late EPS on quinidine. The goal of repeat EPS on quinidine was to ensure persistent long-term drug efficacy (n = 6) or to elucidate the reason of syncopal episodes during therapy (n = 3). The EPS protocol significantly evolved over the years as it became more aggressive (more pacing sites and/or more ventricular extrastimuli). All nine patients tolerated the medication well and had no recurrent documented arrhythmic events during long-term follow-up (mean 15 +/- 7 years). No sustained ventricular tachyarrhythmias could be induced in any patient during repeat late EPS. In six patients, a more aggressive stimulation protocol could be tested at repeat EPS., Conclusion: The long-term reproducibility of the EP efficacy of quinidine in patients with idiopathic VF and Brugada syndrome is excellent. EP-guided quinidine therapy represents a valuable long-term alternative to ICD therapy in these patients.

Background: Data on the incidence and significance of catheter-induced trauma to fast and slow pathways are scarce., Objectives: To evaluate the incidence, predictors, and clinical implications of inadvertent catheter-induced mechanical trauma to fast and slow pathways during radiofrequency ablation (RFA) of atrioventricular nodal reentry tachycardia (AVNRT)., Methods: A total of 901 consecutive patients (aged 9-92 years old) with inducible sustained AVNRT underwent RFA of the slow pathway. All procedures were closely monitored for appearance of catheter-induced mechanical block of fast or slow pathways., Results: Catheter-induced mechanical trauma to fast and/or slow pathways was observed in 121 (13.4%) patients: 86 (71%) patients had trauma of the fast pathway, three (2.4%) had trauma of the slow pathway, and 32 (26.4%) had trauma of both pathways. Mechanical trauma lasted <1 minute in 87 (72%) patients, 1-30 minutes in 23 (19%) and >30 minutes in 11 (9%). A significantly increased procedure discontinuation rate was observed in patients with mechanical trauma as compared to those with no trauma (P < 0.0001). Young patient age (<35) was a strong predictor for the occurrence of mechanical trauma to AV nodal pathways. No significant difference between the trauma and non-trauma groups was found in respect to the number of catheters used during the procedure, the incidence of AV block, and the need for permanent pacemaker implantation., Conclusions: Mechanical trauma to fast and slow pathways during ablation of AVNRT is more common than previously recognized, occurring especially in patients aged <35 years.

Objectives: We sought to assess the frequency of spontaneous or inducible atrioventricular nodal reentry tachycardia (AVNRT) in patients referred for radiofrequency ablation (RFA) of idiopathic outflow tract ventricular arrhythmias., Background: In patients with no obvious heart disease, AVNRT and outflow tract ventricular tachycardia (VT) are the most frequently encountered supraventricular and ventricular tachycardias, respectively. An increased coexistence of the two arrhythmias has been recently suggested., Methods: In 68 consecutive patients referred for RFA of an idiopathic ventricular outflow tract arrhythmia, a stimulation protocol including repeated bursts of rapid atrial pacing, up to triple atrial extrastimuli during sinus rhythm and rapid ventricular pacing was performed before and after isoproterenol infusion following RFA of the ventricular arrhythmia. In patients with inducible AVNRT, RFA of the slow pathway was performed., Results: Of the 68 study patients, 17 (25%) had either spontaneous AVNRT documented prior to RFA of the ventricular arrhythmia (n = 4) or inducible AVNRT at the time of RFA of the ventricular arrhythmia (n = 13). AVNRT was induced by atrial pacing in 15 (88%) of 17 patients: in 3 patients without isoproterenol and in 12 patients during isoproterenol infusion. Uncomplicated RFA of the slow pathway was successfully achieved in all patients with inducible AVNRT., Conclusion: Spontaneous or inducible AVNRT is relatively common in patients with idiopathic outflow tract ventricular arrhythmias. Atrial stimulation, especially when performed after isoproterenol infusion plays a major role in AVNRT inducibility. Although we performed RFA of the slow pathway in patients with inducible AVNRT and no prior tachycardia documentation, the question whether this is mandatory remains unsettled.

We present an unusual mechanism of preexcited tachycardia--atypical AV nodal reentry with bystander AP. It can be differentiated from other preexcited tachycardias by its variable degree of preexcitation (either spontaneous or in response to atrial pacing), higher degree of preexcitation with pacing near the origin of the AP than during tachycardia, inability to preexcite the tachycardia by either late atrial or ventricular premature beats, the presence of nonpreexcited atypical AV nodal reentry tachycardia following successful AP ablation, and by exclusion of atrial tachycardia.

We analyze the arguments commonly afforded by advocates of electrophysiological evaluation for patients with recent myocardial infarction. These arguments are: (1) electrophysiological evaluation is useful for risk stratification of infarct survivors; and (2) it may be used for guiding drug therapy or to identify a group of asymptomatic patients who will benefit from implantation of an automatic cardioverter defibrillator. A positive electrophysiological study is apparently the single best predictor of future arrhythmic events in infarct survivors. However, several noninvasive tests combined may provide just as valuable information. Therefore, electrophysiological evaluation should not be advised, to the majority of infarct survivors, for the mere purpose of risk stratification. Nevertheless, electrophysiological evaluation may be proposed to patients with impaired left ventricular function or high grade ventricular arrhythmias. Patients without inducible arrhythmias have a good prognosis and may be spared the risk of long-term treatment with antiarrhythmic drugs. However, before proceeding with invasive electrophysiological evaluation, both physician and patient should ask themselves if they are willing to go ahead with defibrillator implantation in case sustained monomorphic ventricular tachycardia is induced.

Electrophysiological studies were carried out in two patients with an idiopathic left bundle branch block. Consistent distal His bundle pacing resulted in the normalization of the QRS complex in both patients. Extrastimulation during basic distal His pacing at several cycle lengths was carried out successfully. Using this technique, the refractory periods of the left bundle branches were measured and found to be within the normal range. In addition, they decreased with the shortening of the basic cycle length. These results demonstrated the possibility of determining the refractoriness of the left bundle branch by His bundle pacing in patients with left bundle branch block. Hypotheses are postulated about the presumed location of the lesion responsible for the left bundle branch block.

A 28-year-old male with recurrent episodes of ventricular fibrillation, which were initiated by very early ventricular premature depolarizations with a normal QT interval, was subjected to three consecutive electrophysiological studies. During the first study, which was carried out to test the efficacy of amiodarone treatment, no ventricular arrhythmias could be induced. While on amiodarone therapy, the patient experienced another syncopal episode and therefore a second electrophysiological study was done. In that study, ventricular fibrillation was induced by ventricular stimulation. During the third study, which was carried out in order to evaluate the effect of the addition of quinidine to the on-going amiodarone therapy, no more than three repetitive ventricular responses could be induced. The patient has been asymptomatic since the third study (fifteen months) with combined therapy of amiodarone and quinidine. The significance of the ability to induce ventricular fibrillation during an electrophysiological study is discussed as well as the value of such studies in determining the long-term efficacy of antiarrhythmic drug therapy.

Ten patients with Wolff-Parkinson-White syndrome underwent external His bundle recording using an advanced signal-averaging technique. Surface ECG waveforms were recorded and digitized at 1.28 kHz (10 bit resolution) and then averaged with a CDC-6600 computer. A cross-correlation function, operating in the frequency domain (using the Fast Fourier Transform algorithm) was employed to extract fiducial synchronizing marks for the waveform alignment. Using this technique, reliable His bundle activity could be recorded in nine of ten patients. There was a good correlation between the HQ and HV intervals obtained during external and internal His bundle recordings, respectively, in seven patients who underwent both recordings. Administration of ajmaline enabled to obtain the His bundle activity using a digital filter with low frequency cut-off of 30 Hz as compared to the cut-off of 150 Hz which was necessary during control to reduce the electrical activity of the delta wave. We conclude that using a computerized cross-correlation signal-averaging technique enables the external His bundle recording in patients with WPW syndrome.

Simultaneous AV nodal reentrant and ventricular tachycardias were observed during the course of an electrophysiological study in a 51-year-old patient who suffered from recurrent attacks of sustained ventricular tachycardia. Occurrence of simultaneous tachycardias was facilitated by the fact that both tachycardias had a similar cycle length. Ventricular tachycardia was most probably initiated by AV nodal tachycardia previously induced by atrial extrastimulation following the administration of atropine.