A quantitative and qualitative analysis of the virtual unipolar electrograms from non-contact mapping of right or left-sided outflow tract premature ventricular contractions/ventricular tachycardia origins

OBJECTIVE

This study was conducted to examine the virtual unipolar electrogram configuration of right/left outflow tract (OT) premature ventricular contraction (PVC)/ventricular tachycardia (VT) origins obtained from a non-contact mapping system (NCMS).

METHODS

The subjects consisted of 30 patients with OT-PVCs/VT who underwent NCMS-guided ablation. We evaluated the virtual unipolar electrograms of the origin on 3D right ventricular (RV)-OT isochronal maps.

RESULTS

Successful ablation was achieved from the RV in 20 patients (RVOT group), and it failed in 10 (non-RVOT group: including left-sided/pulmonary artery/deep RVOT foci). On the virtual unipolar electrograms, the earliest activation (EA) preceded the QRS onset by 11.2 ± 2.6 ms in the RVOT group and by 7.4 ± 10.5 ms in the non-RVOT group (P = 0.138). The negative slope of the electrogram at the EA site (EA slope(5)), quantified by the virtual unipolar voltage amplitude 5 ms after the EA onset, was significantly steeper in the RVOT group than in the non-RVOT group (0.66 ± 0.52 mV vs. 0.14 ± 0.17 mV, P = 0.005). Cutoff values for the EA-to-QRS onset time and EA slope(5) of ≥ 8 ms and >0.3 mV, respectively, completely differentiated the RVOT group from the non-RVOT group. A lesser EA slope(5) was associated with a greater radiofrequency energy delivery required to terminate RVOT-PVCs/VT.

CONCLUSIONS

These demonstrate the importance of the virtual unipolar electrograms from OT-PVC/VT origins obtained with the NCMS. The virtual EA predicts both successful and potentially difficult ablation sites from the RV side.

Temperature-controlled cooled-tip radiofrequency ablation in left ventricular myocardium

Steam pop and intramural charring have been reported during cooled-tip radiofrequency catheter ablation (RFCA). We studied the feasibility of temperature-controlled cooled-tip RFCA in the canine heart.An internally cooled ablation catheter was inserted into the left ventricle. A custom-made radiofrequency (RF) generator capable of controlling the tip-temperature at the preset level by slow increases in the power was used. Temperature-controlled cooled-tip RF applications were performed at a target temperature of 40 degrees C for 90 seconds. Acute study: Intramyocardial temperature was measured at the ablation site in 10 dogs by inserting a fluoroptic probe. Chronic study: Lesion depth and volume were measured in 5 dogs after 3 weeks of survival. In the acute study, no pop or abrupt impedance rise was observed. Maximum intramyocardial temperature was 72.4 + or - 14.4 degrees C at 2-4 mm above the endocardium. No coagulum formation, craters, or intramural charring were observed. Maximum lesion depth was 6.7 + or - 1.5 mm, and lesion volume was 404 + or - 219 mm3. In the chronic study, maximum lesion depth was 5.9 + or - 1.1 mm, and lesion volume was 281 + or - 210 mm(3).Temperature controlled RFCA is feasible with a cooled-tip catheter and an RF generator that slowly increases the RF power until the preset catheter-tip temperature is reached.

Left bundle branch block-type ventricular tachycardia originating from the left ventricular septum in a patient with cardiac sarcoidosis

This case report describes a left bundle branch block (LBBB)-type ventricular tachycardia (VT) with a unique reentrant circuit in a patient with cardiac sarcoidosis. The VT morphology and pace mapping supported an exit site of the VT from the basal posterior right ventricle (RV) septum. Nonetheless, concealed entrainment was established by pacing from a septal left ventricular (LV) site recording a diastolic potential, opposite site to the RV site. A point ablation at that LV site could successfully terminate the VT, suggesting that a critical isthmus was located on the LV side of the interventricular septum despite the demonstration of an LBBB-type VT.

Combined effect of pulmonary vein isolation and ablation of cardiac autonomic nerves for atrial fibrillation

This study was designed to determine whether endocardial high-frequency stimulation at the pulmonary vein (PV) antrums can localize cardiac autonomic ganglionated plexi (GP) and whether ablation at these sites can evoke a vagal response and provide a long-term benefit after PV isolation (PVI) for atrial fibrillation (AF). Radiofrequency ablation of each PV antrum was performed in 21 patients with paroxysmal AF (n = 17) or persistent (n = 4) AF. In 8 patients with paroxysmal AF, a ring electrode catheter was placed at each PV antrum. High-frequency stimulation prolonged the R-R interval in 6 of 8 patients at the left superior (LS) PV, in 3 of 8 patients at the left inferior (LI) PV, in 3 of 8 patients at the right superior (RS) PV, and in 3 of 8 patients at the right inferior (RI) PV. A decrease in sinus rate > 20% was observed in 4 of 21 patients during LS PVI, in 2 of 21 patients during RS PVI, and in 1 of 2 patients during RI PVI. Atrioventricular block or a > 5 second pause was observed in 5 of 21 patients during LS PVI. AF recurred during the follow-up period in 5 of the 16 patients (31%) who had no atrioventricular block or > 5 second pause during PVI but did not recur in 5 patients in whom atrioventricular block or a > 5 second pause developed during PVI. GP can be identified by endocardial stimulation. The AF recurrence rate is decreased when a vagal response is achieved by radiofrequency ablation.

Action potential alternans in the right ventricular outflow tract in a patient with asymptomatic Brugada syndrome

A 71-year-old man with frequent ventricular premature contractions after right hip joint surgery was referred to the Cardiology Division. Twelve-lead ECG showed type II Brugada-type ECG and signal-averaged ECG showed positive ventricular late potentials. The 12-lead ECG changed to type I Brugada-type after administration of the class Ic antiarrhythmic drug, pilsicainide. Ventricular fibrillation (VF) was reproducibly induced with double premature stimuli from the right ventricular outflow tract (RVOT) at a basic cycle length (BCL) of 400 ms. Monophasic action potentials (MAPs) recorded from the RVOT at a BCL of 400 ms showed MAP alternans and VF was only induced when extrastimuli were applied after a shorter MAP of the alternans.

Anatomic and electrophysiologic differences between chronic and paroxysmal atrial flutter: intracardiac echocardiographic analysis

BACKGROUND

It remains unknown why atrial flutter (AFL) occurs as either a chronic or paroxysmal arrhythmia.

PURPOSE

The aim of the study was to compare intracardiac echocardiographic (ICE) images of the crista terminalis (CT) and transverse conduction properties of the CT between chronic and paroxysmal forms of common AFL.

METHODS

Chronic AFL (n = 7) was defined as non-self-terminating AFL lasting >1 month, and paroxysmal AFL (n = 8) was defined as an intermittent arrhythmia with symptomatic episodes of 24 hours maximum duration. ICE images of the right atrium were recorded with a 9 F 9-MHz intracardiac ultrasound catheter during pullback at 0.5-mm intervals from the superior vena cava to the inferior vena cava triggered by electrocardiogram and respiration. The two-dimensional image of the right atrium was reconstructed into a three-dimensional (3-D) image.

RESULTS

Three-dimensional images from patients with chronic AFL showed the CT to be thick and continuous, and conduction across the CT was blocked at a pacing rate just above sinus rhythm in all seven patients. In contrast, 3D images from paroxysmal AFL showed the CT to be thin and discontinuous, and conduction across the CT during midseptal pacing was observed in five of the eight patients.

CONCLUSION

The nature of AFL is determined, at least in part, by anatomic and electrophysiologic characteristics of the CT.

Full-motion two- and three-dimensional pulmonary vein imaging by intracardiac echocardiography after pulmonary vein isolation

BACKGROUND

The pulmonary veins (PVs) are topographically complex and motile, so angiographic visualization of the PVs anatomy is limited. An imaging technique that accurately portrays the pulmonary vein (PV) anatomy would be valuable during and after catheter ablation procedures.

PURPOSE

We investigated whether three-dimensional (3D) intracardiac echocardiography (ICE) can visualize radiofrequency (RF)-induced tissue changes after PV isolation.

METHODS

We performed 3D ICE studies with a 9F, 9-MHz ICE catheter after segmental or extended PV isolation. The ICE catheter was placed 3-4 cm inside the PV ostium and mounted onto a pullback device. Sequential two-dimensional (2D) images of the full length of the vein were obtained in 0.3 mm steps with cardiac and respiratory cycle gating. Each image was fed into a computer, and the aggregate data set was reconstructed into a 3D, full-motion image. RF lesion location and lesion size were studied on 67 pullback images from 29 patients.

RESULTS

The 2D and 3D reconstruction was possible for 27 left superior PVs, 13 left inferior PVs, 26 right superior PVs, and one right inferior PV. The ablation site was identified 3-7 mm inside the PV ostium, and a 1/2 - 4/5 circumferential area was ablated with no clinically relevant stenosis. No significant differences were found on the ablated area or ablation site between segmental and extensive PV isolation.

CONCLUSION

The 2D and 3D ICE of the PVs provides detailed anatomical information of the proximal PVs, and RF-induced tissue changes in the PV wall can be visualized by ICE.

Electrophysiological Properties of the Atrium After Cardioversion of Chronic Atrial Fibrillation Relation to the Plasma Brain Natriuretic Peptide Level

BACKGROUND

Brain natriuretic peptide (BNP) level has been shown to increase in patients with chronic atrial fibrillation (CAF) without overt heart failure (HF). Although atrial electrical remodeling associated with CAF has been described, little is known about the effects of the BNP level on the electrophysiological properties in CAF patients.

METHODS AND RESULTS

In 42 CAF patients without overt HF, the atrial monophasic action potential duration (MAPD) at pacing cycle lengths (CLs) of 300-800 msec and P-wave signal-averaged electrograms were recorded after cardioversion. The MAPDs for all CLs were significantly longer in patients with a BNP concentration greater than the 50th percentile (group 1, BNP = 215 +/- 118.2 pg/mL) than in patients with a concentration less than the 50th percentile (group 2, BNP = 68.3 +/- 20.9 pg/mL), resulting in a similar value in the MAPDs at CLs of 350 and 600 msec for group 1 and the control patients (n = 8). The slope value of the MAPDs between CLs of 350 and 600 msec was normal in group 1, but slightly lower in group 2 than in group 1 and control patients. The filtered P-wave duration did not differ between the two groups.

CONCLUSIONS

These electrophysiological characteristics related to the BNP level suggest that the atrial repolarization may be affected by a latent ventricular dysfunction.

Electrocardiographic and Electrophysiologic Characteristics in Patients With Brugada Type Electrocardiogram and Inducible Ventricular Fibrillation Single Center Experience

BACKGROUND

The study examined the electrocardiographic and electrophysiologic characteristics in relation to programmed ventricular stimulation (PVS)-induced ventricular fibrillation (VF) in patients with Brugada syndrome.

METHODS AND RESULTS

Thirty-four patients with a Brugada-type electrocardiogram (ECG) were enrolled. Twelve patients had a type 1 ECG, 12 had a type 2 ECG, and 10 had a type 3 ECG. PVS was performed with up to 2 ventricular premature beats from the right ventricular apex and outflow tract at 2 basic cycle lengths (600 and 400 ms). VF was induced in 17 of 23 (74%) asymptomatic patients and 10 of 11 (91%) symptomatic patients (p<0.05). The 27 patients in whom VF was induced by PVS and 7 patients without inducible VF were followed up for 47.1+/-33.7 months. One sudden death occurred during the follow-up period among asymptomatic patients with inducible VF, and no sudden death occurred among patients without inducible VF.

CONCLUSIONS

In conclusion, inducibility of ventricular arrhythmia is high in patients with Brugada syndrome, but it does not correlate with clinical presentation. Few arrhythmic events occur during follow up. However, the present study data suggest that electrophysiologic study-induced VF does not predict arrhythmic events during follow up.

Endocardial Electrograms From the Right Ventricular Outflow Tract After Induced Ventricular Fibrillation in Patients With Brugada Syndrome

BACKGROUND

The pathogenesis of Brugada syndrome (BS) is reported to be phase 2 reentry resulting from shortening of the action potential duration at the epicardial site of the right ventricular outflow tract (RVOT). However, several reports have shown a high incidence of ventricular late potentials (LPs) and a high rate of induction of ventricular fibrillation (VF) by programmed ventricular stimulation (PVS) among patients with BS. The aim of this study was to investigate the role of slow conduction for the initiation of VF by PVS in these patients.

METHODS AND RESULTS

Endocardial mapping of the RVOT was conducted in 17 patients in whom VF was induced by PVS from the RV apex or RVOT; 11 patients had a positive LP. In 10 patients, RV mapping showed that low-amplitude fragmented and delayed potentials (DPs) were recorded at the RVOT below the pulmonary valve (PV) or between the PV and His bundle electrogram recording site. Electrograms recorded after PVS showed a high incidence of fractionated and disorganized DPs that lead to VF.

CONCLUSIONS

Slow conduction at the RVOT may contribute to the induction of VF by PVS. However, the role of slow conduction in spontaneous VF remains controversial.

Complete AV block developing in a patient with manifest ventricular preexcitation

This case report describes a 37-year-old man with manifest atriofascicular and fasciculoventricular connections who developed complete atrioventricular block. After resumption of 1:1 atrioventricular conduction, an electrophysiological study was conducted. During sinus rhythm, manifest ventricular preexcitation was observed and the AH and HV intervals were 80 msec and 50 msec, respectively. No change in AH interval during constant atrial pacing was observed by bolus injection of 20 mg of adenosine triphosphate. No changes in the morphology of the delta wave or HV interval were observed by changing the atrial pacing site. This patient developed HV block by atrial extrastimulus (S1S1: 600 msec, S1S2 <or= 350 msec). Thus, the patient was diagnosed as having combined atriofascicular and fasciculoventricular connections.

Effect of IKr blocker nifekalant on atrial action potential duration after successful internal cardioversion of chronic atrial fibrillation

BACKGROUND

Chronic atrial fibrillation (AF) is characterized by a marked decrease in the atrial effective refractory period (ERP) and in the ERP adaptation to rate as well as a decrease in the atrial conduction velocity. Little information is available about the ionic mechanisms underlying AF in humans.

MATERIALS AND METHODS

We studied the effect of IKr blocker nifekalant on the rate-dependent changes in atrial action potential duration in 11 patients after successful internal cardioversion of chronic AF of >2 months duration and in 7 patients without AF. In AF patients, right atrial (RA) monophasic action potential (MAP) was recorded at pacing cycle lengths (CLs) of 800-250 ms before and after administration of nifekalant. In control patients, RAMAP was recorded at CLs of 600 and 350 ms before and after administration of nifekalant.

RESULTS

Nifekalant significantly increased RAMAPD at 90% repolarization (RAMAPD90) at CLs of 800-300 ms in the AF patients. The increase in RAMAPD90 by nifekalant became significantly smaller at shorter CLs (42.5 +/- 12.4 ms at a CL of 600 ms vs 32.8 +/- 14.5 ms at a CL of 350 ms, P < 0.05). Effect of nifekalant on RAPMAPD was attenuated at CL of 600 ms in AF patients in comparison to control patients (increase in RAMAPD in control; 73.0 +/- 36.6 ms vs increase in RAMAPD in AF; 42.5 +/- 12.4 ms, P < 0.05); however, it was similar at a CL of 350 ms between control and AF patients.

CONCLUSIONS

Electrophysiological effects of nifekalant are significantly attenuated in the chronically remodeled human atrium at slower heart rates, but the beneficial effect of RAMAPD prolongation by IKr blocker was well-preserved even at shorter CLs after chronic AF.

Relationship Between Anatomic Location of the Crista Terminalis and Double Potentials Recorded During Atrial Flutter:

INTRODUCTION

The activation sequence in typical atrial flutter (AFL) around the tricuspid annulus is well described. However, activation of the remainder of the right atrium (RA) is not well defined. Previous studies have shown a linear block at the crista terminalis (CT) during AFL. The aim of this study was to evaluate the relationship between the location of the CT and the line of block by intracardiac echocardiography (ICE).

METHODS AND RESULTS

Twenty-one patients with typical AFL were included in the study. The ICE imaging catheter (9-French with 9-MHz ultrasound transducer) was advanced to the RA. Under ICE guidance, a 20-pole roving catheter was used to map double potentials (DPs) during AFL, and three-dimensional images of the RA were reconstructed. During counterclockwise (CCW), clockwise (CW) AFL, or both, a line of conduction block manifested by DPs was identified at a septal site adjacent to the CT in 12 patients and in the posteroseptal RA in 9 patients.

CONCLUSION

The functional line of block in CCW and CW AFL is localized not at the CT but at the septal edge of the CT or in the posteroseptal RA.

Reproducible induction of atrioventricular nodal reentrant tachycardia with adenosine triphosphate

A 29-year-old woman was referred for electrophysiological testing and radiofrequency ablation because of repeated episodes of palpitation of a 8-year duration. The 12-lead ECG during palpitations showed narrow QRS tachycardia at a rate of 160 beats/min. Dual AVN physiology according to electrophysiological criteria was not shown by single atrial extrastimulation and the tachycardia could not be induced. Slow/fast atrioventricular nodal reentrant tachycardia (AVNRT) was induced once by double atrial extrastimuli, but it was not reproducible. However, intravenous bolus injection of adenosine triphosphate (12.5 mg) during sinus rhythm led to reproducible initiation of slow/fast AVNRT.

Wolff-Parkinson-White syndrome concomitant with asymptomatic Brugada syndrome

A 29-year-old man was referred for electrophysiological testing and radiofrequency ablation because of repeated episodes of palpitation over 2 years. A 12-lead electrocardiogram during sinus rhythm showed manifest Wolff-Parkinson-White syndrome and during palpitation showed narrow QRS tachycardia at a rate of 213 beats/min. Following successful radiofrequency ablation of the left anterolateral accessory pathway, sustained atrial fibrillation was induced by atrial extrastimulation. Cibenzoline (2 mg/kg body weight) was injected to terminate atrial fibrillation. ST-T segment elevation in the right precordial leads was observed following cibenzoline administration. Ventricular fibrillation was reproducibly induced by ventricular extrastimuli (S1: 600 ms, S2: 220 ms, S3: 210 ms).

Brugada-like electrocardiographic pattern unmasked by fever

Brugada syndrome is characterized by right bundle branch block morphology and ST-segment elevation in the right precordial leads and a propensity to develop ventricular arrhythmias. Mutations in a cardiac sodium channel gene have been linked to this syndrome, and the ionic mechanisms responsible for the electrocardiographic phenotype are temperature-dependent. This case report describes a patient in whom a typical Brugada ECG pattern developed during fever and could be reproduced at normal body temperature by administration of pilsicainide.

Comparison of Coronary Sinus Morphology in Patients With and Without Atrioventricular Nodal Reentrant Tachycardia by Intracardiac Echocardiography

INTRODUCTION

Dual AV nodal physiology is the electrophysiologic substrate for AV nodal reentrant tachycardia (AVNRT), but the anatomic basis for this arrhythmia remains to be elucidated. Atrial flutter (AFL) has been shown to be more frequently inducible in patients with AVNRT.

METHODS AND RESULTS

A 3.2-French, 20-MHz intracardiac ultrasound (ICUS) catheter was introduced into the coronary sinus (CS), and two-dimensional ICUS images were recorded during transducer pullback in 21 patients with AVNRT and 18 control patients. Three-dimensional reconstruction of the CS was created using the TomTec Imaging system. The area of the CS lumen at 15 mm within the CS ostium (os) was not significantly different in patients with and without AVNRT (54.4 +/- 34.7 mm2 vs 39.1 +/- 28.5 mm2). However, the area of the CS os was significantly larger in patients with AVNRT than in those without (112.1 +/- 60.9 mm2 vs 71.7 +/- 44.4 mm2, P < 0.05). Three-dimensional morphology of the CS os revealed flaring in patients with AVNRT, giving it a "windsock" appearance. Sustained AFL was induced in 10 of 21 patients with AVNRT, but in none of 18 control patients (P < 0.005).

CONCLUSION

The CS os was significantly wider in patients with AVNRT than in those without. These findings may have important implications for arrhythmia pathogenesis in AVNRT as well as AFL.

Noninvasive diagnosis of dual AV nodal physiology in patients with AV nodal reentrant tachycardia by adenosine triphosphate test

Atrioventricular nodal reentrant tachycardia (AVNRT) is a relatively common paroxysmal supraventricular tachycardia. This study investigated whether adenosine-5'-triphosphate (ATP) injection during sinus rhythm might be useful in the noninvasive diagnosis of dual AV nodal pathways. The study group consisted of 9 patients with slow/fast AVNRT and 11 control patients without antegrade dual AV nodal physiology (DAVNP). ATP (2.5 to 30 mg, in 2.5-mg increments was injected during sinus rhythm until signs of DAVNP (> or = 50 msec increase or decrease in AH or PR interval in two consecutive beats) or > or = second-degree AV block was observed. DAVNP was diagnosed by ATP test in all 9 patients with slow/fast AVNRT. DAVNP was observed by ATP test in 3 of the 11 control patients. Thus, the test had a sensitivity of 100% and specificity of 73%. ATP test given during sinus rhythm is useful for identifying patients with dual AV nodal pathways who are prone to AVNRT.

Intravenous administration of class I antiarrhythmic drug induced T wave alternans in an asymptomatic Brugada syndrome patient

A 53-year-old man with an abnormal ECG was referred to the Nihon University School of Medicine. The 12-lead ECG showed right bundle branch block and saddleback-type ST elevation in leads V1-V3 (Brugada-type ECG). Signal-averaged ECG showed positive late potentials. Double ventricular extrastimuli (S1: 500 ms, S2: 250 ms, S3: 210 ms) induced VF. Amiodarone (200 mg/day) was administered for 6 months and programmed ventricular stimulation was repeated. VF was induced again by double ventricular stimuli (S1: 600 ms, S2: 240 ms, S3: 170 ms). Intravenous administration of class Ic antiarrhythmic drug, pilsicainide (1 mg/kg), augmented ST-T elevation in leads V1-V3, and visible ST-T alternans that was enhanced by atrial pacing was observed in leads V2 and V3. Visible ST-T wave alternans disappeared in 15 minutes. However, microvolt T wave alternans was present during atrial pacing at a rate of 70/min without visible ST-T alternans.