Shortening of intraventricular conduction time with rapid ventricular pacing

Background: Supernormal conduction (SNC) of the human ventricular myocardium has been reported, but its mechanism remains controversial. Methods: We recorded monophasic action potentials during rapid ventricular pacing from the right ventricular endocardium in 24 patients with supraventricular tachyarrhythmias who underwent catheter ablation. Results: In 7 of 24 patients, shortening of the QRS duration was observed at a pacing cycle length ≤400 ms and lengthening of the QRS duration was observed in 3. Conclusions: Shortening of the QRS duration during rapid ventricular pacing was observed in the patients

Left Atrial Tachycardia After Pulmonary Vein Isolation for Atrial Fibrillation

Left atrial tachycardia (AT) has been reported to occur after pulmonary vein isolation (PVI) for the treatment of atrial fibrillation (AF). We treated 3 patients who developed AT of different mechanisms following PVI. In case 1, focal AT originating at the ostium of the left superior PV was demonstrated and focal radiofrequency ablation was performed at the breakthrough point at the ostium of the left superior PV terminated the AT. In case 2, AT was shown to be counterclockwise macroreentrant AT around the left inferior PV through the conduction gap of the left sided posterior wall for which linear ablation was performed between left superior and inferior PVs. Focal ablation at the conduction gap terminated the AT. In case 3, a macroreentrant AT propagating around the mitral annulus was demonstrated and linear ablation between left inferior pulmonary vein and mitral annulus (mitral isthmus) terminated the AT

Identifying the Origin of Right and Left Ectopic Atrial Beats Triggering Atrial Fibrillation before Atrial Transseptal Procedure

Atrial premature depolarizations (APDs) triggering atrial fibrillation (AF) originate from mainly the pulmonary veins (PVs), but, in some cases, atrial ectopic beats (AEBs) triggering AF originate from the right atrium (RA) or the superior vena cava. Accurate identification of the origin of APDs in the PVs by means of RA and coronary sinus mapping is difficult. Purpose: The aim of this study was to identify the origin of AEBs triggering AF before transseptal catheterization. Electrode catheters were placed in the posteroseptal RA (PSRA), right pulmonary artery (RPA), left pulmonary artery (LPA), and esophagus in 10 patients with paroxysmal AF. We analyzed endocardial electrograms from the PSRA, RPA and LPA, and epicardial electrograms from the esophagus. The origin of the AEBs in the PVs was determined before PV ablation by mapping 4 PVs simultaneously. Four AEBs originated from the left superior PV (LSPV), 2 from the left inferior PV (LIPV), 4 from the right superior PV (RSPV), 2 from the RA or superior vena cava. In AEBs originating from the RA, the PSRA activation was the earliest and it proceeded in a cranial to caudal direction. In AEBs originating from the RUPV, RPA was the earliest. The esophageal activation sequence was in a cranial to caudal direction. In AEBs from the LSPV, LPA was the earliest and the esophageal activation sequence proceeded in a cranial to caudal direction. In AEDs from LIPV, LPA was the earliest, and the esophageal activation sequence was nearly simultaneous. Atrial activation sequences from the PSRA, RPA, LPA, and esophageal catheters can accurately identify the location of the initiating foci of AF before a transseptal procedure

Spatial and temporal variability of the complex fractionated atrial electrogram activity and dominant frequency in human atrial fibrillation

Background: The presence of complex fractionated atrial electrograms (CFAEs) and high dominant frequencies (DFs) during atrial fibrillation (AF) have been demonstrated to be related to AF maintenance. Therefore, sequential mapping of CFAEs and DFs have been used for target sites of AF ablation. However, such mapping strategies are valid only if the CFAEs and DFs are spatiotemporally stable during the mapping procedure. We obtained spatially stable multi-electrode recordings to assess the spatiotemporal stability of CFAEs and DFs. Methods: We recorded electrical activity during AF for 10 min with a 64-electrode basket catheter (48 bipole electrode pairs) placed in the left atrium in 36 patients with AF (paroxysmal AF [PAF], n=16; persistent AF [PerAF], n=20). The spatial and temporal distribution of the CFAEs (fractionation interval 8 Hz) at 1-min intervals for 10 min were compared for each of the 48 bipoles. Results: The baseline CFAEs were located at 68.5±14.0% (32.9±6.7) of the 48 bipoles; however, the high DF sites were fewer (9.6±8.6% [4.6±4.1 bipoles]). The CFAEs sites did not change significantly during the 10-min recording period (kappa statistic: 0.71±0.24); however, the high DF sites changed significantly (kappa statistic: 0.07±0.19). These spatiotemporal changes in the CFAEs and high DFs did not differ between patients with PAF and PerAF. Conclusions: Regardless of the AF type, CFAEs sites, but not high DF sites, showed a high degree of spatial and temporal stability

Analysis of the spatial and transmural dispersion of repolarization and late potentials derived using signal-averaged vector-projected 187-channel high-resolution electrocardiogram in patients with early repolarization pattern

Background: Electrophysiological characteristics of early repolarization syndrome (ERS), i.e., the spatial and transmural dispersion of ventricular repolarization and ventricular late potentials can be evaluated using a signal-averaged vector-projected 187-channel high-resolution electrocardiogram (187-ch SAVP-ECG). We investigated these characteristics as markers of ventricular fibrillation and sudden cardiac arrest in patients presenting with an ER pattern. Methods: The 187-ch SAVP-ECGs were recorded for 8 patients with idiopathic ventricular fibrillation associated with ERS (ERS patients), and 5 patients with an ER pattern without arrhythmic events (ER pattern patients). Results: The ER pattern was located in the inferior leads (n=7), lateral leads (n=1), or both inferior and lateral leads (n=5). The corrected RT(RTc) (peak point of the R wave − positive maximum peak of the first derivative of the T wave interval corrected using the Bazett formula) interval and T(peak-end)-c interval from the 187 channels were calculated. Late potentials were positive in 7 of 8 ERS patients and in 3 of 5ER pattern patients (P=0.25). The average RTc was shorter in patients with ERS (192.6±29.8 ms vs. 234.0±25.5 ms, P=0.04). However, average T(peak-end)-c interval did not differ between the 2 groups. Conclusion: Late ventricular potentials were common in ERS and ER pattern patients. Lethal arrhythmia in ERS patients appeared to be related to the relatively short average repolarization time rather than the spatial and transmural dispersion of repolarization

Wavefront direction and cycle length affect left atrial electrogram amplitude

Background: The relationship between atrial electrogram (EGM) characteristics in atrial fibrillation (AF) and those in sinus rhythm (SR) are generally unknown. The activation rate and direction may affect EGM characteristics. We examined characteristics of left atrial (LA) EGMs obtained during pacing from different sites. Methods: The study included 10 patients undergoing pulmonary vein isolation for AF. Atrial EGMs were recorded from a 64-pole basket catheter placed in the LA, and bipolar EGM amplitudes from the distal electrode pair (1–2) and proximal electrode pair (6–7) from 8 splines were averaged. The high right atrium (HRA), proximal coronary sinus (CSp), and distal coronary sinus (CSd) were paced at 600 ms and 300 ms. Results: When the LA voltage at SR was ≥1.5 mV, bipolar voltages of the HRA were greater than those of the CSp, which were greater than those of the CSd, regardless of the pacing cycle length. The shorter pacing cycle length resulted in a reduction of the LA EGM voltage at sites of SR voltage ≥1.5 mV, but no significant difference was seen at sites where the SR EGM amplitude was between >0.5 and <1.5 mV. No significant differences were seen in intra-basket conduction times between pacing cycle lengths of 600 ms and 300 ms at any pacing site. Conclusion: The rate and direction-dependent reduction of the amplitude of atrial EGMs may explain, in part, the voltage discordance during SR and AF

Monophasic action potential duration alternans after abrupt shortening of the cardiac cycle in humans

Background: Action potential alternans may be important in causing ventricular arrhythmias. Methods and results: We recorded monophasic action potentials from the right ventricular endocardium in patients with persistent atrial fibrillation who underwent internal atrial defibrillation during rapid ventricular pacing. In 3 of 45 patients, monophasic action potential duration alternans was observed at a pacing cycle length ≤350 ms. Conclusion: Action potential alternans is not a rare phenomenon (6.6%) in humans

Spatial and transmural repolarization, and dispersion of repolarization and late potentials evaluated using signal-averaged vector-projected 187-channel high-resolution electrocardiogram in Brugada syndrome

Background: Vector-projected 187-channel electrocardiograms (ECGs) were recorded in 45 patients with a Brugada-type ECG to evaluate spatial and transmural repolarization and dispersion of action potential duration in Brugada syndrome (BS). Methods: Corrected recovery time (RT-c, R wave peak to the first positive maximum derivative of the T wave with Bazett correction) and RT-c dispersion were calculated. The corrected T peak-end interval (T(p-e)-c, T wave peak to the end of the T wave with Bazett correction) and T(p-e)-c dispersion were calculated. Results: RT-c dispersion and T(p-e)-c interval were longer in patients with a type 1 ECG, but there was no significant difference in Tp-e dispersion between patients with a type 1 and those with a type 2/3 ECG. No significant correlation was noted between RT-c dispersion, T(p-e)-c dispersion, and symptoms. Late potentials (P=0.023) and a family history of sudden cardiac death (P=0.0017) were correlated with symptoms. Conclusions: Spatial dispersion of repolarization may constitute the electrocardiographic pattern of the Brugada type ECG and conduction disturbance in addition to repolarization abnormality may contribute to the development of malignant ventricular tachyarrhythmias

Brugada syndrome in the presence of coronary artery disease

Background: Brugada-type ECG changes have been described in association with various cardiac disease states including electrolyte abnormalities, myocardial pathologies, and mechanical cardiac abnormalities as well as drug therapies with particular medications. Such potential confounding factors make it difficult to diagnose Brugada syndrome on the basis of standard guidelines. Methods: To investigate the incidence of significant coronary artery disease in patients with Brugada-type ECG, coronary angiography was performed in 55 patients with Brugada-type ECGs. Results: Five of the 55 patients (9%) had significant coronary artery stenosis, and 3 out of these 5 were asymptomatic. Patients with coronary artery disease were older than in those without coronary artery disease (59.4±7.2 years vs. 49.0±13.8 years, P=0.03). An electrophysiological study was performed in 4 of the 5 patients, and ventricular fibrillation was induced in all 4. Conclusions: We conclude that patients with Brugada-type ECGs should be evaluated for coronary artery disease, and this is especially important for patients in whom age could be a risk factor for the disease

Brain magnetic resonance imaging examination in a patient with non-magnetic resonance conditional pacemaker

Clinical dilemmas arise when patients with a non-magnetic resonance (MR) conditional pacemaker are required to undergo magnetic resonance imaging (MRI). We encountered a pacemaker patient with debilitating non-motor symptoms of Parkinson׳s disease, who required an MRI prior to deep brain stimulation (DBS) surgery. MRI was performed safely without adverse events despite the presence of a conventional pacemaker