Eva Hertervig

Global Repolarization Sequence of the Ventricular Endocardium: Monophasic Action Potential Mapping in Swine and Humans

YUAN, S., et al.: Global Repolarization Sequence of the Ventricular Endocardium: Monophasic Action Potential Mapping in Swine and Humans. The aim of this study was to evaluate the global sequence of repolarization over the ventricular endocardium. Disturbances in myocardial repolarization are associated with the genesis of arrhythmias. However, little is known about the global sequence of repolarization. Monophasic action potentials (MAPs) were recorded from 61 ± 18 LV and/or RV sites in ten healthy pigs and from 43 ± 15 LV or RV sites in eight patients using the CARTO system. Local activation time (AT), end‐of‐repolarization (EOR) time, and MAP duration were calculated and three‐dimensional global maps of AT, EOR, and MAP duration constructed. LV maps were obtained from all ten pigs and RV maps from three pigs. Five RV maps and five LV maps were obtained from the eight patients. (1) EOR sequence was recognizable in 12 of 13 pig maps and in all the patient maps. (2) EOR followed the sequence of activation in 12 of 13 pig maps and 8 of 10 patient maps. (3) The longest MAPs were recorded in or near the earliest activation area, and the shortest ones in or near the latest activation area in all the pig maps and in nine of ten and eight of ten patient maps, respectively. (4) In all maps, MAP duration and AT were negatively correlated, and EOR and AT positively correlated. In conclusion, repolarization gradients exist over the pig and the human ventricular endocardium. The activation sequence is a determinant for the repolarization sequence. The magnitude of the progressive MAP shortening with progressively later activation, relative to local AT, is a critical factor governing the direction and pattern of the EOR.

Evidence for electrical remodelling of the atrial myocardium in patients with atrial fibrillation. A study using the monophasic action potential recording technique.

Experimental studies have shown that remodelling of the atrial myocardium is linked to the occurrence and perpetuation of atrial fibrillation (AF). Clinical evidence, however, is insufficient. We recorded monophasic action potentials (MAP) during AF from one to three sites in the right atrium in seven patients with chronic AF (CAF) and in 11 patients with paroxysmal AF (PAF). The fibrillatory (FF) interval between two consecutive upstrokes of the MAP was measured using a computer‐assisted manual method. The mean, median, 15th, 10th, 5th percentile and shortest FF intervals were calculated in each patient and used as estimates of the local atrial effective refractory period (AERP) during AF. In three patients burst pacing at 400 and 500 beats min–1 was delivered during the MAP recording. In nine patients, the AERP was also tested using the extra stimulus technique during sinus rhythm. Results: Thirty‐eight recordings were obtained. The shortest FF interval was significantly shorter in patients with CAF as compared with that in patients with PAF (50 ± 13 vs. 72 ± 31 ms, P<0·05). Similar differences were seen in the mean, median, 15th, 10th, and 5th percentile FF interval. The AERP during sinus rhythm was significantly longer than the estimated AERPs (P<0·05 to P<0·01) in the nine patients. There was no significant difference in FF interval before and after the burst pacing in the three patients. Conclusion: The AERP was significantly shortened during AF, as compared with that during sinus rhythm, and the AERP shortening was more marked in patients with CAF than in patients with PAF. These clinical findings support the connection between the electrical remodelling and the occurrence and/or perpetuation of the AF.

Global Repolarization Sequence of the Right Atrium: Monophasic Action Potential Mapping in Healthy Pigs

The aim of the study was to explore the global sequence of atrial repolarization and its correlation to that of activation. Endocardial monophasic action potentials (MAPs) were sequentially recorded from 51 ± 14 sites in the right atrium of ten healthy pigs using the CARTO electroanatomic mapping system. Local activation time (AT), MAP duration, and 90% repolarization time (RT) were obtained, and from these data, color coded three‐dimensional maps of AT and RT sequences and spatial distribution of MAP duration were reconstructed. The results of the study were: (1) An activation sequence was recognizable in all maps, starting from the posterosuperior wall and ending in the posteroinferior wall near the tricuspid annulus. (2) The repolarization sequence was also recognizable in all maps, and mainly followed the sequence of activation. (3) A significant positive correlation between the RT and AT was observed in all maps with an average r value being 0.571 ± 0.159 (P < 0.01 – 0.0001) , suggesting that progressively later AT associates with progressively longer RT. (4) No consistent correlation between the MAP duration and AT was found. In conclusion, repolarization gradients exist over the atrial endocardium in healthy pigs. The repolarization sequence follows the same sequence as the activation, suggesting that the spatiotemporal pattern of activation is an important determinant of the characteristics of the repolarization sequence. (PACE 2003; 26:1803–1808)

Electroanatomic mapping of right atrial activation in patients with and without paroxysmal atrial fibrillation

Inter-atrial conduction delay in patients with atrial fibrillation (AF) has been reported. However, the area of this conduction delay has not been well identified. The activation time and conduction velocity over the right atrial endocardium were evaluated during sinus rhythm using the CARTO mapping technique in 6 patients with paroxysmal AF (AF group) and 11 patients without history of AF (control group). No significant differences were observed between the 2 groups in the mean activation times and conduction velocities from the earliest activation site to the superior septum, His bundle area and coronary sinus ostium, or in the total activation times of the right atrium. There was no significant difference between the two groups in the local conduction velocity between 2 adjacent sites in the free wall, septum and bottom of the right atrium. This study suggests the previously reported conduction delay in the posteroseptal region in patients with paroxysmal AF might locate within the posterior inter-atrial septum.

Monophasic action potential mapping in swine and humans using modified-tip ablation catheter and electroanatomic mapping system

Objective : To evaluate the feasibility of monophasic action potential (MAP) mapping using a modified-tip NaviStar catheter in swine and humans. Methods : MAP mapping was performed using the modified-tip catheter at 71 - 21 atrial and 60 - 16 ventricular sites in 10 healthy pigs and at 56 ventricular sites in one patient, and using an ordinary Navi-Star catheter at 30 atrial sites in one patient and 50 - 14 ventricular sites in four patients. In an additional 20 patients, MAPs were also recorded at 9 - 2 atrial sites using the modified-tip catheter or at 12 - 9 atrial sites using the ordinary catheter. Results : In pigs, the plateau amplitudes of the MAPs recorded using the modified-tip catheter were 4.1 - 3.2 mV for the atrial and 9.5 - 4.3 mV for the ventricular MAPs. In patients, both the ventricular and atrial MAPs recorded using the modified-tip catheter were significantly higher than using the ordinary catheters, 15.7 - 8 and 3.0 - 0.9 mV vs 9.5 - 3.9 and 2.0 - 0.6 mV for the ventricular and atrial MAPs, respectively ( p < 0.0001). The baseline disturbances were <10% of the MAP amplitude in 95% of the pig and 96% of the patient MAPs. Conclusion : A modified-tip Navi-Star catheter could be used in swine and in humans for prompt recording of MAPs with acceptable amplitudes and baselines. MAP mapping using the modified-tip catheter is safe and feasible for clinical use.

Electroanatomic mapping of transseptal conduction during coronary sinus pacing in patients with paroxysmal atrial fibrillation

Objective—To delineate the electrophysiological properties of transseptal conduction from the left to the right atrium in patients with paroxysmal atrial fibrillation (AF). Design and results—Right atrial mapping using the electroanatomic mapping technique was performed at 111 ± 16 sites in 16 patients with paroxysmal AF during pacing from distal coronary sinus (CS). A single transseptal breakthrough near the CS ostium was observed in all patients. The activation time from the pacing site to the earliest septal activation site was 47 ± 13 ms. The total septal activation time (68 ± 16 ms) was markedly longer but the total right atrial activation time (118 ± 17 ms) was similar to that in patients without AF in a previous observation. Conclusion—During distal CS pacing, a preferential site of transseptal conduction near the CS ostium was demonstrated in patients with paroxysmal AF. This has clinical implications when surgical dissection or catheter ablation is considered to eliminate interatrial connection in patients with AF.

Epicardial and endocardial dispersion of ventricular repolarization. A study of monophasic action potential mapping in healthy pigs.

Objectives. To investigate the total dispersion of ventricular repolarization of the epi- and endocardium. Design. Monophasic action potentials (MAP) were recorded from 211±54 (151–353) left and right ventricular epi- and endocardial sites during atrial pacing in 10 pigs using the CARTO system. The activation time (AT), MAP duration (MAPd) and end of repolarization time (EOR) were measured. Results. The total dispersion of AT, EOR and MAPd, defined as the maximal differences of these parameters over both the epi- and endocardium, were 57±10, 84±20, and 75±21 ms respectively and were significantly larger than the respective epi- and endocardial dispersions (p<0.05). The epicardial dispersion of AT, EOR and MAPd of both the right and left ventricles were significantly larger than that of each ventricle alone (p<0.02). Sternotomy did not affect these dispersion parameters. Conclusion. Detailed mapping of epicardial repolarization in vivo using the MAP mapping technique is feasible. Both the epi- and endocardium of the two ventricles contribute significantly to the total dispersion of repolarization.

Localization of the initial fibrillatory cycle in patients with paroxysmal atrial fibrillation.

Background - Recent reports suggest the presence of conduction delay in the posterior septal region during sinus rhythm in patients with lone paroxysmal atrial fibrillation (AF). Objective - To explore the location of intra-atrial conduction delay associated with initiation of AF. Design - In 8 lone AF patients (51 - 10 years), 20 AF paroxysms were induced during electrophysiological examination. Bipolar electrograms were acquired from a 10-polar catheter in the coronary sinus (CS), a 4-polar His bundle catheter, and a 20-polar Halo catheter in the right atrium. Results - Induced AF paroxysms showed earliest registered atrial activity in interatrial septum (IAS) or proximal CS in 17 cases (85%). Conduction delay at the posterior IAS or proximal CS accompanied induction of 18 AF paroxysms (6 patients). Atrial activation sequence at the beginning of the AF paroxysms was stable and reproducible in six repeatedly induced AF episodes (3 patients). Conclusion - In lone AF patients, induction of AF is associated with conduction disturbances in the IAS and proximal CS regions.BACKGROUND Recent reports suggest the presence of conduction delay in the posterior septal region during sinus rhythm in patients with lone paroxysmal atrial fibrillation (AF). OBJECTIVE To explore the location of intra-atrial conduction delay associated with initiation of AF. DESIGN In 8 lone AF patients (51 +/- 10 years), 20 AF paroxysms were induced during electrophysiological examination. Bipolar electrograms were acquired from a 10-polar catheter in the coronary sinus (CS), a 4-polar His bundle catheter, and a 20-polar Halo catheter in the right atrium. RESULTS Induced AF paroxysms showed earliest registered atrial activity in interatrial septum (IAS) or proximal CS in 17 cases (85%). Conduction delay at the posterior IAS or proximal CS accompanied induction of 18 AF paroxysms (6 patients). Atrial activation sequence at the beginning of the AF paroxysms was stable and reproducible in six repeatedly induced AF episodes (3 patients). CONCLUSION In lone AF patients, induction of AF is associated with conduction disturbances in the IAS and proximal CS regions.

Pulmonary vein potentials in patients with and without atrial fibrillation

BACKGROUND Pulmonary vein (PV) potentials are invariably recordable at the PV ostia in patients with atrial fibrillation (AF) and delayed conduction around the PV ostia may play a role in the initiation and maintenance of AF. AIMS To investigate the presence and extent of PV potentials in patients with and without AF. METHODS AND RESULTS Circumferential catheter recordings at the PV ostia were obtained from 10 patients with paroxysmal AF and 9 with concealed Wolff-Parkinson-White (WPW) syndrome without history of AF. Typical PV potential was defined as either rapid deflections that separated from atrial deflection with a time delay in-between, or multiphasic, continuous or fractionated potentials. The presence of PV potentials was verified during sinus rhythm and during atrial pacing at the distal coronary sinus for the left PVs or at the right atrial appendage for the right PVs. To quantify the extent in which the PV potentials were recordable, the number of PVs with typical PV potentials recordable was counted. The time interval from the onset to the end of the electrograms recordable at the PV ostium (A-PV interval) was measured, and the maximal and mean of this interval were obtained. Typical PV potentials were recorded in 31 of 34 PVs (91%) in patients with AF, but in 4 of 36 PVs (11%) in patients with concealed WPW. A narrow, biphasic or triphasic, potential was recorded in 3 of 34 PVs (9%) in patients with AF, but in 29 of 36 (81%) PVs in patients with concealed WPW. The maximal and mean A-PV intervals were significantly longer in patients with AF (71 +/- 24 and 49 +/- 13 ms) than in patients with concealed WPW syndrome (33 +/- 14 and 25 +/- 6 ms). CONCLUSION In patients with AF, typical PV potentials with marked conduction time delay were almost invariably recordable at the PV ostium, but in patients without a history of AF, merely simple, narrow potentials were found. These findings support the involvement of conduction delay and re-entrant activities around the PV ostia in the genesis and/or perpetuation of AF.

Global dispersion of right atrial repolarization in healthy pigs and patients.

Objective—To investigate the feasibility of monophasic action potential (MAP) mapping using an electroanatomical mapping system (CARTO) in obtaining information on global dispersion of atrial repolarization and to evaluate the role of dispersion of repolarization in the genesis of paroxysmal atrial fibrillation (PAF). Methods and results—Right atrial MAPs were recorded from 53 ± 18 sites in 10 healthy pigs and 33 ± 21 sites in 6 patients with and 4 patients without history of PAF. In pigs, the global dispersions of activation time (AT), MAP duration and end of repolarization time (EOR), 70 ± 8, 95 ± 18 and 121 ± 28 ms, respectively, were significantly greater than those among 10, 20 and 30 sites. In patients with PAF, the global dispersions of MAP duration and EOR (128 ± 10 and 149 ± 31 ms) were significantly greater than those in patients without PAF (84 ± 10 and 91 ± 17 ms). Conclusion—MAP mapping using the CARTO system was feasible in experimental and clinical settings in obtaining information on global dispersion of atrial repolarization. The number of recording sites could significantly affect repolarization parameters. The dispersions of atrial repolarization were significantly greater in patients with PAF than those without, suggesting the involvement of an increased dispersion of repolarization in the genesis of PAF.