Transesophageal echo phase imaging for localizing accessory pathways during adenosine-induced preexcitation in patients with the Wolff-Parkinson-White syndrome

Preexcitation syndrome: experimental study on the electrocardiogram of antegradely conducting accessory pathway

Background

Preexcitation syndrome is characterized by a dominant delta wave on the baseline electrocardiogram (ECG), resulting from the change in QRS initial vector by the accessory pathway (AP). This study is to explore the effect of ventricular preexcitation on the QRS initial, maximal and terminal vector in an experimental rabbit with preexcitation syndrome induced by programmed electrical stimulation.

Methods

Rabbits (n = 10) were randomized for the experimental model of ventricular preexcitation. Sensing and stimulating electrode catheters were placed in the high right atrium and along epicardial surface of atrioventricular groove of the left ventricular anterior wall, respectively. Programmed premature stimulation S₂ was synchronized with P wave and utilized to stimulate the ventricle. The ECG recorded the electrical activity of the heart. As compared with the QRS complex during sinus rhythm, paced QRS was assessed regarding the initial, maximal and terminal vector. PS₂ interval and PR interval were also measured and analyzed.

Results

Preexcitation was successfully simulated by ventricular pacing in the rabbits, including (1) Complete preexcitation: PS₂ interval was less than PR interval; the difference was more than or equal to 47.00 ± 7.53 ms. (2) Incomplete preexcitation: PS₂ interval was less than PR interval; the difference was less than 47.00 ± 7.53 ms. (3) Incomplete latent preexcitation: PS₂ interval was more than or equal to PR interval; the difference was less than or equal to 13.00 ± 3.50 ms. (4) Complete latent preexcitation: PS₂ interval was more than or equal to PR interval; the difference was more than 13.00 ± 3.50 ms.

Conclusions

The difference in the relative conduction velocity of the atrioventricular node versus the AP pathways determines the degree of preexcitation and different manifestation on ECG. The QRS terminal vector also reflects the ventricle preexcitation, indicating a valuable sign for the diagnosis of atypical or latent preexcitation.

Effects of Preexcitation Syndrome on Terminal QRS Vector Observed in Spatial Vector

BACKGROUND

Preexcitation syndrome could affect terminal QRS vector, which is not emphasized in clinic. In this study, we made a comparison between vectorcardiogram (VCG) before and after ablation to observe the change of terminal QRS vector. Furthermore, the relationship between the change of terminal QRS vector and accessory pathway (AP) as well as the change of initial QRS vector (delta vector) was analyzed.

METHODS

Thirty patients who were proved to have a single AP by ablation were included. All patients were divided into seven groups based on the AP location. Comparison between VCG before and after ablation was made to observe the change of terminal and delta vector. The relationship between the change of terminal QRS vector and AP location as well as delta vector was analyzed.

RESULTS

(1) All 30 patients had a change in terminal QRS vector (elevation and/or azimuth) in comparison to postablation VCG. (2) The change of terminal QRS vector was related to delta vector and AP location. The agreement and consistency between the change of terminal QRS vector and delta vector were 91.65% and 0.856 (P < 0.01), respectively.

CONCLUSIONS

(1) Both initial and terminal QRS vector are affected by the antegrade conduction of AP. The change of terminal QRS vector is related to the AP location and delta vector. (2) The effect of preexcitation syndrome on QRS terminal vector is shown as more intuitive and easy in spatial vector by comparison with electrocardiogram, which is helpful for the diagnosis of atypical preexcitation and localization of AP.

Effect of Radiofrequency Catheter Ablation on Doppler Echocardiographic Parameters in Patients With Wolff-Parkinson-White Syndrome

The aim of this study was to compare the conventional Doppler echocardiographic parameters before and after accessory pathway ablation in patients with Wolff-Parkinson-White (WPW) syndrome. Thirty patients (19 males, 11 females) aged 35.5 +/- 14.4 years were enrolled in the study. All patients underwent successful radiofrequency catheter ablation (RFCA). Echocardiograhic examination was performed before and after RFCA. Aortic and pulmonary flows, diastolic early (E) and late (A) transmitral filling velocities, their velocity time integrals (VTI), mitral diastolic filling time (DFT), deceleration time (DT), isovolumic relaxation time (IVRT), aortic ejection time, and aortic VTI were assessed before and after RFCA. We found that the pulmonary valve opened earlier than the aortic valve when the accessory pathway was located on the right ventricular side (P = 0.02). Otherwise, if the accessory pathway was located on the left ventricular side, the aortic valve opened earlier (P < 0.01). Intervals between the onsets of aortic and pulmonary flows were shortened after RFCA (P = 0.01). We also observed prolongation of DFT (P < 0.001), increases in A velocity (P < 0.05) and its VTI (P < 0.01), as well as a decrease in the E/A ratio (P < 0.01) and shortening of aortic ejection time (P = 0.01) with restoration of AV conduction. We conclude that Doppler echocardiographic examination can provide clues about accessory pathway location and RFCA causes some significant changes in Doppler echocardiographic time intervals. These changes confirm that cardiac synchrony is restored after RFCA.

Echocardiographic quantification of left ventricular asynergy in coronary artery disease with Fourier phase imaging

BACKGROUND

Visual evaluation of wall motion is subjective and may be difficult in patients with impaired left ventricular function. Current algorithms used to analyze wall motion usually neglect motion asynchrony that may be profoundly altered in coronary artery disease. This study was to investigate whether the extent of left ventricular asynergy can be used to quantify the severity of regional myocardial dysfunction by the use of Fourier phase imaging.

METHODS

Echocardiographic cine loops of 21 patients with ischemic cardiomyopathy (EF < or = 40%) were mathematically transformed using a first-harmonic Fourier algorithm displaying the sequence of wall motion as phase angles in parametric images and regional phase histograms. Segmental fractional area shortening (FAC) and qualitative assessment of regional wall motion based on visual inspection served as reference method.

RESULTS

There was an inverse linear relationship between FAC and phase angles (r = -0.75, p < 0.01). Normal endocardial motion yielded low phase angles (mean 16 +/- 15 degrees SD). With an increase in wall motion abnormalities, phase angles were progressively delayed by 56 +/- 38 degrees in hypokinetic, by 88 +/- 38 degrees in akinetic, and by 143 +/- 33 degrees (p < 0.001) in dyskinetic segments.

CONCLUSIONS

These results demonstrate that left ventricular asynchrony is an indicator of regional myocardial dysfunction in coronary artery disease. Echocardiographic Fourier phase imaging can be used to quantify wall motion displaying contraction sequence in a simple and objective format.

Decreased amplitude of left ventricular posterior wall motion with notch movement to determine the left posterior septal accessory pathway in Wolff-Parkinson-White syndrome

OBJECTIVE

To determine preoperatively, by analysing asynchronous left ventricular wall motion, whether to approach through the right ventricle or the left ventricle when carrying out catheter ablation of the accessory pathway in Wolff-Parkinson-White syndrome, especially in patients with the pathway located on the septum.

METHODS

73 patients with manifest Wolff-Parkinson-White syndrome who underwent successful catheter ablation were studied. Location of accessory pathway was classified as right ventricular side: right anterior paraseptum, right anterior, right lateral, right posterior, anterior septum, midseptum, right posterior septum; left ventricular side: left posterior septum, left posterior, left lateral, left anterior. Asynchronous systolic wall motion was analysed by cross sectional echocardiography.

RESULTS

Echocardiography showed that the amplitude of left ventricular posterior systolic wall motion was reduced when the pathway was located on the left ventricular side as opposed to the right ventricular side (mean (SD), 11.1 (1.7) v 12.9 (1.1) mm, p < 0.001), especially in patients with left posterior septal accessory pathway (9.7 (0.8) mm). There were no overlapping values between the left posterior septal accessory pathway and the right ventricular side accessory pathway. Posterior wall notch motion was observed in all patients with a left posterior septal accessory pathway (9/9), but not at all in patients with pathways located on the right ventricular side of the septum. In patients with a septal accessory pathway, an ECG algorithm provided poor information (relatively low sensitivity, specificity, and predictive value) for determining whether the subsite faced either the left (left posterior septum) or the right ventricle (anterior septum, midseptum, right posterior septum).

CONCLUSIONS

Decreased amplitude of left ventricular posterior wall motion with notch movement is an important finding for accessory pathways located on the left posterior septum. These findings provided clinically useful information for determining whether to approach catheter ablation from the right or the left ventricle.

Two-dimensional guided M-mode color tissue Doppler echocardiography in artificial preexcitation models

The purpose of this study was to analyze the left ventricular contraction patterns in artificial preexcitation models by using 2-dimensional guided M-mode color tissue Doppler echocardiography. Three types of preexcitation models were produced in 12 patients by right atrio-mitral annular sequential pacing, carried out at the left ventricular lateral, posterior, and posteroseptal walls. Tissue Doppler M-mode was recorded at anteroseptal, posterior, lateral, and posteroseptal sites in the parasternal short-axis view. The time interval from the onset of the QRS complex during sinus rhythm or from the annular pacing spike during fusion beats to the beginning of systolic motion was measured. During sinus rhythm, the time interval at the anteroseptal wall was shortest. During fusion beats, the time intervals at the mitral annular pacing sites were shortest. In preexcitation models, tissue Doppler M-mode could clearly distinguish the difference of left ventricular contraction patterns and detect the earliest contraction site of the left ventricle.

Ventricular excitation maps using tissue Doppler acceleration imaging: potential clinical application

OBJECTIVES

The purpose of this study is to validate the use of tissue Doppler acceleration imaging (TDAI) for evaluation of the onset of ventricular contraction in humans.

BACKGROUND

Tissue Doppler acceleration imaging can display the distribution, direction and value of ventricular acceleration responses to myocardial contraction and electrical excitation.

METHODS

Twenty normal volunteers underwent TDAI testing to determine the normal onset of ventricular acceleration. Two patients with paroxysmal supraventricular tachycardia and 30 patients with permanent pacemakers underwent introduction of esophageal and right ventricular pacing electrodes, respectively, and were studied to visualize the onset of pacer-induced ventricular acceleration. Eight patients with dual atrioventricular (AV) node and 20 patients with Wolff-Parkinson-White (WPW) syndrome underwent TDAI testing to localize the abnormal onset of ventricular acceleration, and the results were compared with those of intracardiac electrophysiology (ICEP) tests.

RESULTS

The normal onset and the onset of dual AV node were localized at the upper interventricular septum (IVS) under the right coronary cusp within 25 ms before the beginning of the R wave in the electrocardiogram (ECG). In all patients in the pacing group, the location and timing of the onset conformed to the positions and timing of electrodes (100%). In patients with WPW syndrome, abnormal onset was localized to portions of the ventricular wall other than the upper IVS at the delta wave or within 25 ms after the delta wave in the ECG. The agreement was 90% (18 of 20) between the abnormal onset and the position of the accessory pathways determined by ICEP testing.

CONCLUSIONS

These results suggest that TDAI is a useful noninvasive method that frequently is successful in visualizing the intramural site of origin of ventricular mechanical contraction.

Noninvasive localization of accessory pathways in patients with Wolff-Parkinson-White syndrome with the use of myocardial Doppler imaging

This study sought to examine the diagnostic accuracy of noninvasive prediction of accessory pathway localization in patients with manifest Wolff-Parkinson-White syndrome with the use of myocardial Doppler imaging as a new noninvasive mapping procedure. Myocardial Doppler imaging measures myocardial velocities and therefore can determine the site of earliest ventricular activation in patients with accessory bypass tracts. Twenty-five patients with manifest preexcitation were studied with the use of pulsed wave and M-mode myocardial Doppler imaging for the evaluation of the shortest electromechanical time interval in 9 basal myocardial segments. The new diagnostic test was compared with 3 electrocardiographic algorithms. An invasive mapping procedure served as reference standard. Abnormally short electromechanical time intervals were found in preexcited segments (27 +/- 12 ms vs 64 +/- 27 ms). Myocardial Doppler imaging correctly localized 84% of the accessory pathways and electrocardiographic algorithms only 48% to 60% of cases. Noninvasive prediction of accessory pathway localization by myocardial Doppler imaging is accurate and proved to be superior to prediction based on electrocardiographic algorithms.

Improvement of Echocardiographic M-Mode Detection of Ventricular Precontraction in the Wolff-Parkinson-White Syndrome by Transesophageal Atrial Pacing

BACKGROUND: The purpose of this study was to evaluate the accuracy of conventional M-mode echocardiography in localizing the site of the accessory pathway in 21 patients with overt Wolff-Parkinson-White (W-P-W) syndrome during sinus rhythm (SR) and during transesophageal atrial stimulation (TAS). METHODS: The invasive electrophysiological study was used as a reference, and the results were compared with the pathway localization obtained through algorithmic interpretation of the 12-lead electrocardiogram during SR. Echocardiographic left parasternal short-axis recordings were performed during SR and TAS (100-120 beats/min). The shortest electromechanical interval measured at six different sites of the atrioventricular valve plane from the onset of the delta wave to the peak of the precontraction defined the pathway localization. RESULTS: Correct localization of the accessory pathway with echocardiography could be attained in 14 patients during SR (14 of 21, or 66%). With the aid of TAS, correct pathway localization was achieved for an additional 2 patients, making a total of 16 patients (76%). During TAS, precontraction was enhanced in 63% of the patients. With the algorithmic electrocardiographic interpretation, the localization of the accessory pathway was correct in 13 of the 21 patients (62%). The differences were not significant. CONCLUSION: M-mode echocardiography is a simple and readily available method for the identification of precontraction. The method is comparable to pathway localization through algorithmic ECG interpretation during SR. Transesophageal left atrial pacing during echocardiography can amplify the precontraction and thereby facilitate the interpretation of the wall motions.

Application of tissue Doppler imaging technique in evaluating early ventricular contraction associated with accessory atrioventricular pathways in Wolff-Parkinson-White syndrome

To examine the feasibility of a tissue Doppler imaging (TDI) technique for evaluating the early contraction sites in Wolff-Parkinson-White (WPW) syndrome, we analyzed the time-sequential changes in ventricular wall motion in WPW syndrome by TDI. Fifty patients with WPW syndrome were examined by the TDI system in which the high-speed scanning technique allowed for a frame rate up to 38 frames/sec. Among 42 patients in whom the acceptable images were obtained by TDI, the early contraction, which was represented by a red or blue spot appearing on the subendocardial side at the time of the delta wave in the electrocardiogram, was demonstrated in 25 of 29 patients with left-sided accessory pathways. However, in 13 patients with right-sided pathways, the early contraction sites could be identified in only five patients. The TDI-determined early contraction sites were well coincided with the sites of the accessory pathways determined by the electrophysiologic examination (p < 0.01). After the successful radiofrequency catheter ablation, early contraction sites were found to disappear by TDI in all patients. These results demonstrate the feasibility of the TDI technique to evaluate the early ventricular contraction associated with the atrioventricular accessory pathways. We suggest that the TDI system is helpful to localize the accessory pathways and to evaluate the results after radiofrequency ablation, although further studies are necessary to demonstrate the advantage of TDI over conventional echocardiography and electrophysiologic study in the evaluation of the accessory pathways in WPW syndrome.