QT dispersion failed to estimate the global dispersion of ventricular repolarization measured using monophasic action potential mapping technique in swine and patients.

The aim of this study was to evaluate whether the QT dispersion measured from 12-lead electrocardiogram (ECG) can estimate the global dispersion of ventricular repolarization (DVR) measured using a monophasic action potential (MAP) mapping technique. Monophasic action potentials were recorded from 75 +/- 12 left ventricular sites in 10 pigs and from 48 +/- 16 left or right ventricular sites in 15 patients using the CARTO mapping system. The maximum DVRs in both end-of-repolarization and MAP duration among all the mapped sites were calculated and termed as global DVR for each measurement. QT intervals, QT peak and QT end , were measured from the 12-lead ECG, and QT dispersions; namely the differences between the maximum and the minimum of the QT peak and QT end were calculated. We found that QT dispersions were significantly smaller than (P < .05) and poorly correlated with the global DVRs both in pigs and patients. Bland-Altman agreement analysis demonstrated a marked variation of the differences and an obvious lack of agreement between the results obtained using the ECG and the MAP methods. In our patients, the global DVR increased markedly during ventricular tachycardia as compared with that during sinus rhythm (P < .05), whereas there was no significant difference in QT dispersion between these 2 subgroups. In conclusion, QT dispersion on the surface ECG could not estimate the global DVR measured using the MAP mapping technique. These findings are not consistent with some previously reported observations, suggesting the need for reappraisal of the electrophysiological implications of QT dispersion.

Non-invasive evaluation of ventricular refractoriness and its dispersion during ventricular fibrillation in patients with implantable cardioverter defibrillator.

BACKGROUND: Local ventricular refractoriness and its dispersion during ventricular fibrillation (VF) have not been well evaluated, due to methodological difficulties. METHODS: In this study, a non-invasive method was used in evaluation of local ventricular refractoriness and its dispersion during induced VF in 11 patients with VF and/or polymorphic ventricular tachycardia (VT) who have implanted an implantable cardioverter defibrillator (ICD). Bipolar electrograms were simultaneously recorded from the lower oesophagus behind the posterior left ventricle (LV) via an oesophageal electrode and from the right ventricular (RV) apex via telemetry from the implanted ICD. VF intervals were used as an estimate of the ventricular effective refractory period (VERP). In 6 patients, VERP was also measured during sinus rhythm at the RV apex and outflow tract (RVOT) using conventional extra stimulus technique. RESULTS: Electrograms recorded from the RV apex and the lower esophagus behind the posterior LV manifested distinct differences of the local ventricular activities. The estimated VERPs during induced VF in the RV apex were significantly shorter than that measured during sinus rhythm using extra stimulus technique. The maximal dispersion of the estimated VERPs during induced VF between the RV apex and posterior LV was that of 10 percentile VF interval (40 +/- 27 ms), that is markedly greater than the previously reported dispersion of ventricular repolarization without malignant ventricular arrhythmias (30-36 ms). CONCLUSIONS: This study verified the feasibility of recording local ventricular activities via oesophageal electrode and via telemetry from an implanted ICD and the usefulness of VF intervals obtained using this non-invasive technique in evaluation of the dispersion of refractoriness in patients with ICD implantation.

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.

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.