Retrograde P wave polarity in reciprocating tachycardia utilizing lateral bypass tracts

Highly Efficient and Rapid Detection of the Cleavage Activity of Cas9/gRNA via a Fluorescent Reporter

The RNA-guided endonuclease clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) derived from CRISPR systems is a simple and efficient genome-editing technology applied to various cell types and organisms. So far, the extensive approach to detect the cleavage activity of customized Cas9/guide RNA (gRNA) is T7 endonuclease I (T7EI) assay, which is time and labor consuming. In this study, we developed a visualized fluorescent reporter system to detect the specificity and cleavage activity of gRNA. Two gRNAs were designed to target porcine immunoglobulin M and nephrosis 1 genes. The cleavage activity was measured by using the traditional homology-directed repair (HDR)-based fluorescent reporter and the single-strand annealing (SSA)-based fluorescent reporter we established in this study. Compared with the HDR assay, the SSA-based fluorescent reporter approach was a more efficient and dependable strategy for testing the cleavage activity of Cas9/gRNA, thereby providing a universal and efficient approach for the application of CRISPR/Cas9 in generating gene-modified cells and organisms.

Role of the surface electrocardiogram in the diagnosis of patients with supraventricular tachycardia

In this era of interventional electrophysiology, the accuracy of the electrocardiogram in diagnosis of supraventricular tachycardia could be improved by detailed endocardial mapping and confirmed by results of radiofrequency catheter ablation. This article describes the electrocardiographic characteristics for different types of supraventricular tachycardia: atrial fibrillation, atrial flutter, atrial tachycardia, atrioventricular reciprocating tachycardia using an accessory pathway, and atrioventricular node reentrant tachycardia. Several limitations, including the identification of P wave morphologies and polarities and separation between the terminal part of T wave and P wave during tachycardia, should be resolved before an accurate algorithm of the 12-lead surface electrocardiogram is developed for the diagnosis of supraventricular tachycardia.

Negative lead I P waves during anteroseptal accessory pathway orthodromic reciprocating tachycardia

Although a negative retrograde P wave in lead I during orthodromic reciprocating tachycardia is thought to indicate a left free wall accessory pathway, we describe similar negative P waves in lead I during orthodromic reciprocating tachycardia through anteroseptally situated accessory pathways.

A new electrocardiographic algorithm using retrograde P waves for differentiating atrioventricular node reentrant tachycardia from atrioventricular reciprocating tachycardia mediated by concealed accessory pathway

OBJECTIVES

The purpose of this study was to use an electrocardiographic (ECG) algorithm, derived from the results of radiofrequency ablation, to discriminate atrioventricular node reentrant tachycardia (AVNRT) from atrioventricular reciprocating tachycardia (AVRT) and to localize a concealed accessory pathway, prospectively.

BACKGROUND

Information about ECG criteria for differentiating AVNRT from AVRT is limited and has not been confirmed by surgical or catheter ablation.

METHODS

Four hundred six ECGs (obtained from 406 different patients) that demonstrated narrow QRS complex (< 0.12 s) supraventricular tachycardia with an RP' interval less than the P'R interval or pseudo r' wave in lead V1 or pseudo S wave in inferior leads, or both, were examined, and the results were confirmed by radiofrequency catheter ablation. The initial 226 ECGs were analyzed to develop a stepwise algorithm, and the subsequent 180 ECGs were prospectively evaluated by the new algorithm.

RESULTS

The presence of a pseudo r' wave in lead V1 or a pseudo S wave in leads II, III, aVF indicated anterior-type AVNRT with an accuracy of 100%. With the difference of RP' intervals in leads V1 and III > 20 ms, posterior-type AVNRT could be differentiated from AVRT utilizing a posteroseptal pathway with a sensitivity of 71% (95% confidence interval [CI] 55% to 89%), a specificity of 87% (95% CI 67% to 97%) and a positive predictive value of 75% (95% CI 56% to 91%). According to the polarity of retrograde P waves in leads V1, II, III, aVF and I during AVRT, the concealed accessory pathway could be localized to one of the nine regions on the atrioventricular annuli with an accuracy of 75% (for a right midseptal pathway) to 93.8% (for a left posterior pathway). Overall, the new algorithm had an accuracy of 97.8% in discriminating AVNRT from AVRT and 88.1% in localizing a concealed accessory pathway, prospectively. Prediction was incorrect in only 15 patients (9.1%).

CONCLUSIONS

The new ECG algorithm derived from the analysis of retrograde P waves during tachycardia could provide a criterion for differential diagnosis between AVNRT and AVRT and for predicting the location of concealed accessory pathways.

P wave morphology during atrial pacing along the atrioventricular ring. ECG localization of the site of origin of retrograde atrial activation

P wave morphology during atrial pacing along the atrioventricular (AV) ring was evaluated to develop electrocardiographic (ECG) criteria for identifying the site of origin of the atrial activation wave during reentrant supraventricular tachycardia. Because P wave morphology changes as the pattern of atrial activation changes, the P wave should show characteristic morphologies during reentrant supraventricular tachycardia with use of either accessory AV pathways or the AV node for retrograde atrial activation. In 14 patients, 12-lead ECGs were recorded during bipolar atrial pacing at sites in the coronary sinus vein (along the mitral annulus) and along the atrial endocardium of the tricuspid annulus. P wave morphology was graded for each lead at each site. Sensitivity, specificity, and predictive value of ECG criteria for left versus right and anterior versus posterior atrial pacing sites were evaluated. Data were obtained from 14 sites along the AV ring, including 71 recordings at 6 sites in the coronary sinus vein and 94 recordings at 8 sites along the tricuspid annulus. These recordings were further divided into 54 anterior sites and 80 posterior sites, as well as 62 recordings along the right free wall and 32 recordings along the right atrial septum. The predictive value of a positive P wave in lead I indicating right atrial site of origin was 98.9%, and that for a negative or isoelectric P wave in lead I indicating a left atrial site of origin was 94.6%. Negative P wave in leads II, III, and aVF indicated a posterior site of origin, with a predictive value of 91.2%. The predictive value of a negative or isoelectric P wave in lead V1 indicating a right atrial free wall site was 87.5%. Thus, P wave morphology can be used to localize the site of origin of the atrial depolarization wave to a region along the AV ring.

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

Paroxysmal supraventricular tachycardia (SVT) is a benign form of tachycardia that generally does not require costly evaluation. The purpose of this study was to describe a new sign permitting delineation of the mechanism of SVT by analysis of the P wave in lead V1 and the left atrial electrogram, which may be registered by the esophageal electrode. Among 146 patients with SVT, 72 had a ventriculoatrial interval greater than 70 msec. The P wave in lead V1 during SVT was discernible in 69 of them. The precession of the left atrial electrogram on the P wave in lead V1 was always associated with reentry through a left lateral (n = 37) or posteroseptal (n = 4) accessory atrioventricular (AV) connection. When the P wave in lead V1 preceded or occurred simultaneously with the left atrial electrogram, reentry was through either the AV node or a right-sided accessory AV connection. On the other hand, although the P wave in lead V1 was more frequently negative in reentry through a right-sided connection and positive in reentry through a left-sided connection, the polarity was not specific enough to identify the reentry. The precession of the left atrial electrogram recorded by the esophageal electrode on the P wave in lead V1 during SVT was a specific criterion of reentry through a left accessory AV connection, and this technique could be useful for preliminary localization of the accessory connection before electrophysiologic study.

Value of esophageal pacing in evaluation of supraventricular tachycardia

Esophageal stimulation was performed in 40 patients who had spontaneous paroxysmal supraventricular tachycardias (SVTs). The purpose of this study was to look for the most sensitive stimulation protocol and criteria that would help to define the mechanism of reentry. In 20 patients (group I) atrial pacing up to second-degree atrioventricular block was performed under control conditions and isoproterenol, and SVT was induced in 14 patients (70%), 11 in the control state and 3 while receiving isoproterenol. In 20 patients (group II) atrial pacing and programmed atrial stimulation using 1 and 2 extrastimuli delivered at 2 cycle lengths (600 and 500 ms) was performed in the control state and while receiving isoproterenol. SVT was induced in all patients, in 13 patients in the control state and in 7 while receiving isoproterenol. Programmed stimulation always induced SVT and was the only method capable of tachycardia induction in 14 patients. The mechanism of SVT could be established in 91%. The measurement of the ventriculoatrial interval was the most useful sign to define the site of reentry. Occurrence of a bundle branch block helped to delineate the mechanism in 4 patients. When a positive P wave in V1 preceded the esophageal atrial electrocardiogram, it suggested that there was reentry through a left-sided accessory atrioventricular connection in 6 patients. SVT could always be induced by programmed atrial stimulation in the control state and under isoproterenol. The location of the P wave in V1 compared to the ventriculogram and the esophageal electrocardiogram helped to define the mechanism of tachycardia.

The localization of bypass tracts in the Wolff-Parkinson-White syndrome from the surface electrocardiogram

The bypass tracts of the WFW syndrome may be situated anywhere along the AV ring. Accurate localization of such tracts has in the past been largely effected by electrophysiologic studies, particularly epicardial mapping. During recent years, however, criteria for localization of the bypass tracts from the conventional 12-lead ECG have become increasingly apparent. The preceding presentation constitutes a review and state of the art governing these rapidly developing diagnostic principles.

Differential diagnosis of tachycardia with narrow QRS complex (shorter than 0.12 second)

One hundred eighty-seven patients with clinically documented supraventricular tachycardia with a narrow QRS complex were admitted for electrophysiologic study. The diagnoses after this study were circus movement tachycardia using an accessory pathway in 50 patients, atrioventricular nodal tachycardia in 50 patients, atrial flutter in 50 patients, atrial tachycardia in 27 patients and an incessant tachycardia retrogradely using a slowly conducting accessory pathway in 10 patients. On retrospective analysis, 5 criteria on the 12-lead electrocardiogram during tachycardia were analyzed for their value in making the diagnosis of site of origin. These criteria were P-wave location, axis of the P wave, atrial rate, alternation of the QRS complex and atrioventricular relation. Fifty-seven patients with a narrow QRS tachycardia were prospectively studied using the 5 criteria. A correct diagnosis was made in 48 of the 57 patients (84%). Thus, in most patients with a narrow QRS tachycardia, information from the 12-lead electrocardiogram is adequate for diagnosis.

Value of the 12 lead electrocardiogram in diagnosing type and mechanism of a tachycardia: a survey among 22 cardiologists

Information from programmed electrical stimulation of the heart has improved our ability to diagnose the site of origin and mechanism of a tachycardia from the 12 lead electrocardiogram. To test this hypothesis, the 12 lead electrocardiograms of a 12 year old girl with the Wolff-Parkinson-White syndrome showing four different types of tachycardia were sent for interpretation to 30 leading electrocardiologists , 22 of whom responded. A correct diagnosis of all four tachycardias was made by 13. Three or two of the tachycardias were correctly diagnosed by four and five cardiologists, respectively. The outcome of our study indicates that the pathway and mechanism of tachycardia can frequently be predicted from the 12 lead electrocardiogram alone.

Value of QRS alteration in determining the site of origin of narrow QRS supraventricular tachycardia

To determine the value of alternation of QRS morphology in determining the site of origin of sustained narrow QRS supraventricular tachycardia (SVT), we retrospectively studied 163 distinct tachycardias in 161 patients (ages 4 to 91 years) in whom the site of origin of SVT was proven by intracardiac electrophysiologic study. Sustained SVT was defined as lasting longer than 30 sec. Narrow QRS was defined as QRS width less than 0.12 sec. Atrial fibrillation and flutter were excluded. The presence or absence of QRS alternation was judged at least 10 sec after initiation of SVT. Circus movement tachycardia with anterograde AV node conduction and a retrograde accessory AV pathway was seen in 89 patients (58 with Wolff-Parkinson-White syndrome, 31 with concealed accessory pathway); intra-AV nodal reentrant tachycardia (AVNT) was present in 57 cases, and 17 tachycardias were atrial in origin. QRS alternation was present in 36 of 163 cases (22%). In only eight of these 36 did RR interval length alternation accompany alternation in QRS morphology. Thirty-three of 36 (92%) tachycardias with QRS alternation were circus movement tachycardias. Two were atrial in origin and one was AVNT. We conclude that the presence of QRS alternation during sustained narrow QRS SVT is highly indicative of a retrograde accessory AV pathway in the tachycardia circuit.