Shiwen Yuan

Monophasic action potentials: concepts to practical applications

Monophasic Action Potentials. Monophaisc action potential (MAP) recordings reproduce the repolarization time course of intrucellular action potentials with high accuracy and provide precise information on the local activation time. With the advantage of in vivo application and the development of the safer and simpler contact catheter technique, MAP recording has become the method of choice for evaluating myocardial repolarization changes. This review aims to provide information on practical application of MAP recording in the clinical setting. MAPs can easily be recorded from the endocardium with the contact catheter technique in the electrophysiology laboratory and from the epicardium with electrode probes during open heart surgery. The technical aspects are described in detail. The rate dependence of myocardial excitability and repolarization and the effect of antiarrhythmic drugs on MAP duration and effective refractory period are thoroughly reviewed. The use of MAPs in detecting myocardial ischemia, in studying early afterdepolarization and triggered arrhythmias, in measuring dispersion of repolarization, in identifying intracardiac conduction and the development of the T wave, and in verifying the arrhythmogenic effect of mechanoelectric feedback are presented. Computerized automatic analysis of MAPs and the limitations of the MAP technique are also discussed.

Localization of cardiac arrhythmias : conventional noninvasive methods

Noninvasive localization of the accessory pathway (AP) in patients with the Wolff-Parkinson-White syndrome and of the site of origin of ventricular tachycardia (VT) is reviewed. 12-lead electrocardiography (ECG) is the most readily available method for localization of both the AP and the site of VT origin. Many published ECG criteria are introduced. The application of body surface potential mapping, vectocardiography, nuclear phase imaging, echocardiography, computed tomography, nuclear magnetic resonance, and signal-averaged ECG in the localization of these arrhythmogenic substrates is also described. We believe that ECG is the most sensitive noninvasive method for AP localization as well as being convenient and simple; it may be used as the only noninvasive method for the initial evaluation. The left lateral AP, which occurs with an incidence of more than 40%, could be localized preoperatively by noninvasive methods only. For localization of the site of VT origin, none of the noninvasive methods is accurate enough for guiding the surgical and catheter-mediated ablative therapies so far.

Clinical application of a microcomputer system for analysis of monophasic action potentials

Computerized analysis of monophasic action potentials (MAPs) has rarely been reported in clinical setting. We developed a computer system featuring on‐line acquisition and user‐monitored automatic measurement of multichannel MAPs with the capability of manual corrections. This system has been used in 34 patients in whom two‐channel MAPs and 1‐lead ECG were digitized during sinus rhythm, pacing, and programmed stimulation (PS). In total, 41,413 MAPs in 212 data files were measured. The correct determination rate was 100% for MAP onset and plateau, 99.78% (95.76% during PS) for MAP baseline, and 99.96% (54.29% during PS) for QRS onset. The comparison between the computerized and manual measurements in 292 MAPs showed that the former highly agreed with the latter, with the limits of agreement, defined as mean difference ± 2 SD, being from ‐4.8‐4.9 ms for activation time and from – 4.1‐6.0 ms for MAP duration measurements. Using this system, two‐channel MAPs of more than 300 consecutive beats can be measured in a few minutes, which made it possible to determine the steady state of MAP duration individually, and evaluate the MAP changes during intervention in detail. The clinical routine procedure for testing the effective refractory period and several new MAP parameters were also evaluated using this system. Conclusion: The MAP measurement using this computer system is reliable, rapid and accurate; it can therefore replace the manual method and provide more useful information for clinical research.

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 111u2005±u200516 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 47u2005±u200513u2005ms. The total septal activation time (68u2005± 16u2005ms) was markedly longer but the total right atrial activation time (118u2005±u200517u2005ms) 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.

Atrial average conduction velocity in patients with and without paroxysmal atrial fibrillation

To evaluate intra‐atrial conduction delay in patients with atrial fibrillation (AF) via calculation of conduction velocities (CVs) of the right and left atria.

Coronary sinus cannulation with a steerable catheter during biventricular device implantation.

Abstract Objectives. To determine whether a steerable catheter with electrogram guidance (CS-assist group) could facilitate access to the coronary sinus (CS) during cardiac resynchronization therapy (CRT) implantation. Design. Consecutive patients who underwent CRT implantation were recruited prospectively into the CS-assist group (n = 81) and compared with those using conventional techniques without an electrogram guidance (conventional group, n = 101). Results. The CS cannulation success rate was clearly greater in the CS-assist group (100%) than that in the conventional group (95%, p < 0.05), with significantly shorter mean procedure time (52.6 ± 20.6 min vs. 73.2 ± 40.9 min, p < 0.01) and fluoroscopy time (3.6 ± 3.2 min vs. 14.2 ± 20.4 min, p < 0.01). In the five CS cannulation failure cases, mean procedure time (144.0 ± 37.0 min) and fluoroscopy time (57.8 ± 24.8 min) were significantly longer than those in the other patients (61.2 ± 32.3 and 8.2 ± 13.6 min, respectively, n = 177, both p < 0.01). Conclusions. Using the steerable catheter with real-time electrogram guidance, location of and access to the CS is more rapid and successful, which may improve the success of the CRT implantation and may give significant time savings.

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.BACKGROUNDnRecent reports suggest the presence of conduction delay in the posterior septal region during sinus rhythm in patients with lone paroxysmal atrial fibrillation (AF).nnnOBJECTIVEnTo explore the location of intra-atrial conduction delay associated with initiation of AF.nnnDESIGNnIn 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.nnnRESULTSnInduced 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).nnnCONCLUSIONnIn lone AF patients, induction of AF is associated with conduction disturbances in the IAS and proximal CS regions.

Effect of pentisomide (CM 7857) on myocardial excitation, conduction, repolarization, and refractoriness. An electrophysiological study in humans

The electrophysiological effects of pentisomide upon the intact human heart were evaluated using programmed stimulationand recording of intracardiac monophasic action potentials (MAP) in 17 patients with various ventricular arrhythmias. After i.v. administration of pentisomide, 85–135 mg, the atrial-His interval increased by 8 ± 12 ms (p < 0.05) during sinus rhythm and by 13 ± 21 ms (p < 0.05) at atrial pacing of 600 ms cycle length (600 ms pacing). The His-ventricular interval also increased by 6 ± 10 ms during sinus rhythm (p < 0.05) and by 5 ± 9 ms at 600 ms pacing (NS). The QRS duration prolonged by 9 ± 10ms(p < 0.01)and 6 ± 8 ms (p < 0.01) during 600 and 500 ms ventricular pacing, respectively. The right ventricular MAP duration to 90% repolarization was significantly shortened, by 20 ± 21 ms (p < 0.01) during sinus rhythm, by 16 ± 17 ms (p < 0.01) at 600 ms ventricular pacing, and by 11 ± 16 ms (p < 0.01) at 500 ms ventricular pacing. The corrected QT interval was shortened by 21 ± 28 ms (p < 0.01). The present study supports that pentisomide is a class-I antiarrhythmic agent with a marked effect on depolarization (action of class la and lc) and on repolarization (action of class Ib). This unique combination of cellular electrophysiological properties indicates that the clinical antiarrhythmic efficacy of pentisomide may differ from that of hitherto available antiarrhythmic drugs.

Pulmonary vein potentials in patients with and without atrial fibrillation

BACKGROUNDnPulmonary 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.nnnAIMSnTo investigate the presence and extent of PV potentials in patients with and without AF.nnnMETHODS AND RESULTSnCircumferential 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).nnnCONCLUSIONnIn 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.

Conduction properties of accessory atrioventricular pathways: importance of the accessory pathway location and normal atrioventricular conduction.

Abstract Objective—The objective of this study was to determine the conduction properties of the nOlmal atrioventricular (AV) conduction system in relation to accessory pathway (AP) location in patients with symptomatic Wolff–Parkinson–White syndrome. Design—The conduction properties of the AP and the AV node were studied in 356 patients with single manifest AP who underwent successful ablation. Results—Sixty-three percent of the APs were located on the left free wall (226) and the remaining 37% were posteroseptal, anteroseptal and right free wall. AV block (PR ≥ 220 ms) was observed in 15 patients, 8 cases being associated with the right free wall (15%) compared with 7 on the left free wall (3%, p = 0.002) and none on the anteroseptal (p = 0.02) or posteroseptal (P = 0.007). The PR (182 ± 30ms) and AH (102 ± 25 ms) intervals associated with right free wall AP Were longer than left free wall (166 ± 23, 88 ± 21 ms, p < 0.000 I, respectively), anteroseptal (155 ± 11 , 79 ± 12 ms, p < 0.0001) and posteroseptal AP (ISS ± 16,79 ± 13 ms, p < 0.0001), whereas the PR and AH intervals associated with posteroseptal and anteroseptal AP were shorter than left free wall AP (p < 0.05). When patients with A V block were excluded from the analysis, the PR intervals in patients with right free wall AP were still longer than in those with left free Wall (p < 0.005), anteroseptal (p < 0.001) and posteroseptal AP (p < 0.0001), as were the PR intervals associated with left free wall AP compared with data of posteroseptal (p < 0.01) and anteroseptal AP (p < 0.05). Significant differences in AV nodal effective refractory period, anterograde and retrograde AV block cycle length were also observed in relation to AP location. Conclution—The conduction properties of the normal AV conduction system are associated with specific AP location in patients with Wolff–Parkinson–White syndrome.