Study of P wave morphology in lead V1 during supraventricular tachycardia for localizing the reentrant circuit

Impact of transesophageal electrophysiologic study to elucidate the mechanism of arrhythmia on children with supraventricular tachycardia and no preexcitation

An electrophysiologic study (EPS) of children and teenagers with paroxysmal supraventricular tachycardia (SVT) and normal electrocardiography (ECG) in sinus rhythm was evaluated. Generally, EPS is performed only before paroxysmal SVT ablation in these patients. In this study, 140 patients (mean age, 15 ± 3 years) with normal ECG in sinus rhythm were studied for SVT by a transesophageal route in baseline state and after isoproterenol. Idiopathic left or right ventricular tachycardia was diagnosed in four patients (3 %). Anterograde conduction over an atrioventricular (AV) left lateral (n = 10) or septal (n = 9) accessory pathway (AP) was noted in 19 patients (13.5 %) at atrial pacing. Orthodromic AV reentrant tachycardia (AVRT) was induced in these children. Five of the patients had a high rate conducted over AP (>240 bpm in baseline state or >290 bpm after isoproterenol). Two of the patients (a 10-year-old girl with well-tolerated SVT and a 17-year-old with syncope-related SVT) had the criteria for a malignant form with the induction of atrial fibrillation conducted over AP at a rate exceeding 290 bpm in baseline state. Of the 140 patients, 74 (53 %) had typical AV node reentrant tachycardia (AVNRT), nine had atypical AVNRT (6 %), 1 had atrial tachycardia (0.7 %), and 33 (23.5 %) had AVRT related to a concealed AP with only retrograde conduction. Electrophysiologic study is recommended for children with paroxysmal SVT and normal ECG in sinus rhythm. The data are helpful for guiding the treatment. Ventricular tachycardia or atrial tachycardia can be misdiagnosed. Masked preexcitation syndrome with anterograde conduction through AP was present in 13.5 % of the patients, and 1.4 % had a malignant preexcitation syndrome.

Optimum lead positioning for recording bipolar atrial electrocardiograms during sinus rhythm and atrial fibrillation

BACKGROUND

To date, Holter monitoring has been predominantly utilized in the investigation and monitoring of ventricular arrhythmias and myocardial ischemia. Whether currently employed lead configurations are optimal for recording atrial electrocardiograms (ECGs) is unknown.

HYPOTHESIS

This study was undertaken to determine which conventional and novel lead configurations are optimal for recording atrial electrical activity during sinus rhythm and atrial fibrillation.

METHODS

Recordings were performed on eight healthy volunteers in sinus rhythm and four patients in atrial fibrillation. Each subject had 10 ECGs of three bipolar and three augmented unipolar leads recorded during supine rest, while rising to upright, and during standing rest, yielding a total of 60 leads (30 bipolar leads). Each tracing was inspected by two observers, and parameters such as P-wave amplitude and duration, whether the P-wave onset was clearly seen, atrial fibrillatory-wave amplitude, and amplitude of noise during standing were scored.

RESULTS

Leads recording inferiorly and leftward orientated bipoles provided the best registration of sinus P waves. The P-wave amplitude in the standard bipolar C5 lead (0.12 +/- 0.02 mV) was, however, inferior to others such as recordings between C1 and C6 positions (P-wave amplitude 0.16 +/- 0.02 mV) or from below the right clavicle to the left upper quadrant of the abdomen (0.16 +/- 0.01 mV). Optimal recording of fibrillatory waves was from different leads, such as a bipole from below the left clavicle to a low C1 position (fibrillatory wave amplitude 0.27 +/- 0.03 mV).

CONCLUSION

When Holter recordings are performed for the investigation of atrial arrhythmias, nonstandard lead configurations provide superior recording of atrial electrical activity. We advocate the use of electrodes positioned from C1 to C6, from below the left clavicle to a low C1 position, and a vertically orientated lead from the manubium to the twelfth vertebra or the xiphisternum.

Transitory or permanent regular wide QRS complex tachycardia induced by atrial stimulation in patients without apparent heart disease. Significance

OBJECTIVES

The purpose of the study was to evaluate the frequency of transitory or permanent bundle branch block (BBB) associated with a paroxysmal tachycardia induced by atrial stimulation in patients without heart disease and its significance.

METHODS

Esophageal atrial stimulation was performed in 447 patients suspected to have supraventricular tachycardias (SVT). Sustained regular tachycardia was induced in all of them but three, either in control state (75%) or after administering isoproterenol. In 346 patients, only narrow complex SVTs were induced (77%); in 259 of them, the reentry occurred in the AV node and in remaining patients within a concealed accessory pathway. In 62 patients, a transitory functional BBB was recorded at the onset of the tachycardia (14%). In 33 of them, the reentry occurred in the AV node and in the remaining 29 patients within a concealed accessory pathway. In 36 patients (8%), a permanently wide QRS complex tachycardia was induced. Three patients had also inducible narrow complex SVT. Atrial pacing induced a BBB similar to the aberrancy in tachycardia in 22 patients: the reentry occurred in the AV node in 17 patients, within a concealed accessory pathway in three patients and in a Mahaim bundle in two patients. In other patients, QRS complex remained normal during atrial pacing: all 14 patients had a ventricular tachycardia (VT), either a verapamil-sensitive VT (n = 7) or catecholamine-sensitive VT (n = 4) or bundle branch reentry (n = 3). Followed from 2 to 12 years, the prognosis of these patients was excellent.

CONCLUSION

Transitory BBB at the onset of an SVT is noted in 14% of the population, is more frequent in patients with accessory pathway reentrant tachycardia, but is helpful for this diagnosis in only 12% of cases. A regular tachycardia with permanent left or right bundle branch morphology induced by atrial stimulation in a patient without heart disease and without BBB during atrial pacing is due to a VT even if this patient has also narrow complex tachycardias. This mechanism does not affect the excellent prognosis of this population.

Testing of a new T-wave subtraction algorithm as an aid to localizing ectopic atrial beats

BACKGROUND

Identifying the timing and morphology of an ectopic P wave from the surface electrogram can aid in the diagnosis and localization of atrial arrhythmias. Given the relatively short coupling interval of atrial ectopic beats, the P wave is often obscured by the larger amplitude QRS-T wave complex. A method to uncover such "buried" P waves using a standard 12-lead surface ECG would be clinically useful and could potentially be a noninvasive guide to catheter ablation of focal atrial tachycardia.

METHODS

We developed an automated computerized program (BARD DUO LAB SYSTEM trade mark ) designed to subtract the QRS-T wave complex from the surface electrogram and uncover a previously obscured P wave. The purpose of the present study was to validate this program. The surface ECG from 21 patients undergoing atrial pacing during electrophysiologic study (group I) and 10 patients with atrial tachycardia (group II) were analyzed and the derived P-wave morphology assessed using correlation waveform analysis (CWA) and visual grading by three reviewers.

RESULTS

The algorithm successfully uncovered the P wave in each surface ECG. For the 21 patients in group I, average CWA comparing the derived P wave with the previous paced P wave was 83%. Average CWA for group II was 82%. Visual grading of the match between derived P waves and paced P waves revealed a 21/21 match in group I patients and a 12/12 match in 9/10 of group II patients.

CONCLUSIONS

An ectopic atrial P wave obscured by a coincident QRS-T wave complex can be accurately uncovered using this new algorithm. Addition of this technique to existing methods may improve the diagnosis of atrial arrhythmias and aid in the localization and ablation of ectopic atrial foci.

Influence of age on the electrophysiological mechanism of paroxysmal supraventricular tachycardias

The purpose of this study was to evaluate the influence of age on the mechanism of paroxysmal supraventricular tachycardia (PSVT). Previous studies have shown age and sex differences between certain arrhythmias and especially changes in electrophysiological characteristics of Wolff-Parkinson-White syndrome. Four hundred and eighty five patients aged 9-86 years, with PSVT and without Wolff-Parkinson-White syndrome in sinus rhythm, were studied. The esophageal or intracardiac electrophysiological study used a standardized atrial pacing protocol. Paroxysmal junctional tachycardia was induced in 475 patients. The mechanism of tachycardia was not influenced by age and atrioventricular nodal reentrant tachycardia (AVNRT) was found as the main cause of PSVT in all ranges of age. Atrioventricular reentrant tachycardia (AVRT) using a concealed accessory pathway (AP) had a similar incidence from youth to elderly. The ratio male/female (M/F) and the inducibility of other arrhythmias (atrial flutter/fibrillation) (AF/AFl) were also found to be similar in all ranges of age. The age of the patients did not influence the mechanism of the tachycardia. Most of PVST were related to a AV nodal reentrant tachycardia. Concealed accessory pathway was identified with a similar incidence in young and old patients.

Correlation of P-wave polarity with underlying electrophysiologic mechanisms of long RP' tachycardia

Analysis of surface electrocardiograms from patients with long RP' tachycardia due to either atypical atrioventricular node reentrant tachycardia, permanent junctional reciprocating tachycardia, or low atrial tachycardia was performed. Although a negative P wave in the inferior leads is common to all 3 mechanisms, the results suggest that a positive or isoelectric P wave in electrocardiographic lead I strongly supports a diagnosis of atypical atrioventricular node reentrant tachycardia, whereas a negative or biphasic P wave in lead I argues against this mechanism.