Utility of introducing ventricular premature complexes during reciprocating tachycardia in specifying the location of left free wall accessory pathways

Use of Programmed Ventricular Extrastimulus During Supraventricular Tachycardia to Differentiate Atrioventricular Nodal Re-Entrant Tachycardia From Atrioventricular Re-Entrant Tachycardia

OBJECTIVES

This study hypothesized that early coupled ventricular extrastimuli (V₂) stimulation might yield a more robust differentiation between atrioventricular nodal re-entrant tachycardia (AVNRT) and atrioventricular re-entrant tachycardia (AVRT).

BACKGROUND

Programmed V₂ during supraventricular tachycardia are useful to differentiate AVNRT from AVRT by subtracting the ventriculoatrial (VA) interval from the stimulus to atrial depolarization (stimulus atrial [SA]) interval, but all such maneuvers have limitations.

METHODS

Patients with either AVNRT or AVRT were investigated. The entire tachycardia cycle length (TCL) was scanned with V₂ delivered from the right ventricular apex. The SA-VA difference was calculated with V₂ clearly resetting the tachycardia. The prematurity of V₂ was calculated by dividing the coupling interval (CI) by the TCL.

RESULTS

A total of 210 patients (102 with AVNRT) were included. The SA-VA difference was >70 ms in all AVNRT patients and was <70 ms in all AVRT patients with right and septal accessory pathways (APs), except for those with decremental APs, in whom there was an overlap between AVNRT and AVRT with left APs. However, a SA-VA difference >110 ms with a CI/TCL of <65% distinguished AVNRT from AVRT using the left AP, with sensitivity and specificity of 87% and 100%, respectively. Ventricular overdrive pacing resulted in tachycardia termination or AV dissociation in 28% of patients compared with 15% of patients using the V₂ technique (p = 0.008).

CONCLUSIONS

A SA-VA of >70 ms using the V₂ technique differentiated AVNRT from AVRT using septal and right APs. Use of the V₂ technique with a short CI differentiated AVNRT from AVRT using left APs. The V₂ technique less frequently resulted in tachycardia termination compared with ventricular entrainment.

Differentiation of atrioventricular nodal reentrant tachycardia from orthodromic reciprocating tachycardia by the resetting response to ventricular extrastimuli: comparison to response to continuous ventricular pacing

BACKGROUND

The usefulness of ventricular entrainment to differentiate AV nodal reentrant tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT) by substracting the corrected postpacing interval (cPPI) from the tachycardia cycle length (TCL) or the ventriculoatrial interval during stimulation (SA) from that during tachycardia (VA) have been widely validated. However, some tachycardias are interrupted by pacing trains but may not be so by ventricular extrastimuli resulting in resetting.

OBJECTIVES

To validate prospectively the diagnostic yield of cPPI-TCL and SA-VA measurements after resetting and to determine the proportion of AVNRT and ORT that can be entrained and/or reset from the right ventricular apex (RVA).

METHODS

223 consecutive patients with inducible AVNRT or ORT underwent pacing trains and single extrastimulus (also double extrastimuli if singles did not reset tachycardia) at the RVA. We calculated cPPI-TCL and SA-VA during entrainment and resetting.

RESULTS

Entrainment could not be achieved in 15.2% of tachycardias because of consistent tachycardia interruption by pacing; resetting was observed in 99.5%. Values of cPPI-TCL and SA-VA > 110 milliseconds after resetting identified AVNRT as accurately as after entrainment. Values for cPPI-TCL/ SA-VA were: sensitivity: 98/100%; specificity: 96/98%; positive predictive value: 98/99%; negative predictive value: 98/100%.

CONCLUSIONS

Determinations of cPPI-TCL and SA-VA after resetting with single or double RVA extrastimuli are useful maneuvers to differentiate AVNRT from ORT and can be used for nearly every inducible AVNRT or ORT, even if they are interrupted by ventricular trains.

Use of double ventricular extrastimulation to determine the preexcitation index in atrioventricular nodal reentrant tachycardia

The ability of single paced ventricular beats during tachycardia to penetrate the tachycardia circuit and reset the subsequent atrial depolarization (atrial preexcitation), enabling calculation of the "preexcitation index," can be helpful in analyzing supraventricular tachycardias. However, the ventricular refractory period often prevents ventricular capture of beats with the necessary prematurity to demonstrate atrial preexcitation, particularly in atrioventricular nodal reentrant tachycardia (AVNRT). We hypothesized that the use of double premature stimuli could overcome this limitation. In 25 consecutive patients with either AVNRT or atrioventricular reciprocating tachycardia (AVRT) we attempted to demonstrate atrial preexcitation with single and double ventricular extrastimuli. Whereas atrial preexcitation with a single extrastimulus could only be achieved in 3 of 11 patients with AVNRT, all but 1 patient demonstrated atrial preexcitation with the use of double ventricular extrastimuli. On the other hand, in all but 1 patient with AVRT, atrial preexcitation could be achieved with single and double extrastimuli. A formula was derived for obtaining a preexcitation index with double extrastimuli and shown to correspond closely with the preexcitation index obtained with a single extrastimulus in the 16 patients in whom atrial preexcitation could be achieved with single and double extrastimuli. Thus, this technique significantly enhances the ability to achieve atrial preexcitation and to calculate the preexcitation index in patients with AVNRT, and thus may be useful in deciphering tachycardia mechanism in some patients, as well as being a useful technique in studying the electrophysiological properties of the antegrade and retrograde limbs of AVNRT.

Systematic characterization of the reentrant circuit during atrioventricular nodal reentrant tachycardia

This study was conducted to systematically characterize the excitable gap and conduction properties of the reentrant circuit during atrioventricular nodal reentrant tachycardia (AVNRT). Previous studies have attempted to analyze these properties by introducing single ventricular extrastimuli during tachycardia. These studies have been limited, however, by the inability of single extrastimuli to engage the circuit in the majority of patients studied. Thus, in most cases, the nature of the excitable gap and the conduction properties of the anterograde and retrograde limbs of the circuit during tachycardia remain undefined. In this series, 11 patients with typical AVNRT were studied. During tachycardia, both single and double ventricular extrastimuli (the first extrastimulus acting as a conditioning stimulus) were used to scan diastole. The resetting response of the reentrant circuit, as well as the conduction properties of the retrograde fast and anterograde slow pathways, was recorded and analyzed. Whereas atrial preexcitation and resetting of the reentrant circuit could be demonstrated in only 1 patient with single ventricular extrastimuli, resetting was achieved in all 11 patients with closely coupled double ventricular extrastimuli. Over the full range of coupling intervals used, no retrograde delay in fast pathway conduction could be demonstrated before tachycardia termination or ventricular refractoriness. Penetration of the reentrant circuit resulted in a progressive increasing delay in the anterograde portion of the subsequent return cycle and an increasing resetting response pattern in all cases. Thus, the reentrant circuit during AVNRT demonstrates heterogeneous excitability. While the fast pathway remains fully excitable during tachycardia, the slow pathway uniformly demonstrates decremental conduction, resulting in an increasing resetting response pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of the summit of the right ventricular aspect of the ventricular septum during orthodromic atrioventricular reentrant tachycardia

Application of ventricular premature complexes (VPCs) from the right ventricular (RV) apex during orthodromic atrioventricular (AV) reentrant tachycardia has limitations both in the ability to shorten the succeeding atrial cycle length and in helping to identify accessory pathway location. Stimulation from the summit of the RV aspect of the septum during AV reentrant tachycardia was investigated as a new technique to improve the diagnostic utility of applying VPCs during AV reentrant tachycardia. VPCs were induced during AV reentrant tachycardia at 10 ms decrements in patients with left free wall (n = 15), posteroseptal (n = 5), and right free wall (n = 3) accessory pathways from the RV apex and then from the summit of the RV septum. When the His was refractory, shortening of the atrial cycle length was noted in 13% of patients with left free wall pathways, in 60% of patients with posteroseptal pathways, and in 100% of patients with right free wall pathways with VPCs from the RV apex, and in 47, 100 and 100%, respectively, with VPCs from the summit of the septum. When all VPCs were considered, there was a significant shortening of the atrial cycle length in 67% of patients with left free wall pathways when stimulated from the RV apex, which increased to 93% with summit stimulation. An extrastimulus applied on or after the His effected a significant shortening of the atrial cycle length in no patients with left free wall pathways.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiological substrate for antidromic reciprocating tachycardia. Prerequisite characteristics of the accessory pathway and atrioventricular conduction system

BACKGROUND

Although the anatomic "substrate" for the occurrence of antidromic reciprocating tachycardia (ART) has been previously examined, the underlying physiological substrate for this unusual arrhythmia in patients with the Wolff-Parkinson-White syndrome has not been thoroughly characterized.

METHODS AND RESULTS

The electrophysiological properties of the accessory pathway and normal ventriculoatrial conduction system in 30 patients with ART and a single accessory pathway were compared with those observed in a control group of 36 patients without this arrhythmia to elucidate the critical physiological substrate essential for the development and maintenance of ART. Inducible ART had a mean cycle length of 286 +/- 31 msec. The average retrograde ventriculoatrial conduction system effective refractory period in ART patients was significantly less than that in the control group (244 +/- 32 versus 291 +/- 46 msec, p = 0.0002). All of the ART patients showed retrograde conduction over the normal conduction system at cycle lengths of less than or equal to 360 msec; 23 had 1:1 conduction to less than or equal to 300 msec, and 16 showed 1:1 propagation at cycle lengths of less than or equal to 260 msec. The shortest cycle length accompanied by 1:1 retrograde propagation over the normal conduction system in patients with ART was also significantly less than that observed in the control group (274 +/- 39 versus 347 +/- 73 msec, p less than 0.001). The accessory pathway anterograde ERP in ART patients with 1:1 retrograde conduction over the normal ventriculoatrial conduction system at cycle lengths of less than or equal to 360 was significantly less than that seen in comparable control patients (247 +/- 23 versus 284 +/- 56 msec, p = 0.001), and the accessory pathway location was significantly further from the atrioventricular node in 21 patients with ART undergoing surgery than that in 22 operated control patients (3.8 +/- 0.8 versus 2.9 +/- 0.8 mapping units, p = 0.0025) who also had retrograde ventriculoatrial conduction to cycle lengths of less than or equal to 360 msec. No significant differences in anterograde atrioventricular conduction system properties, retrograde accessory pathway refractoriness, or shortest ventricular pacing cycle lengths maintaining 1:1 conduction via the accessory pathway were observed between groups.

CONCLUSIONS

This quantitative characterization of the properties of conduction and refractoriness of both the accessory pathway and ventriculoatrial conduction system and the relation between these characteristics and the accessory pathway location in ART patients provides additional insight into the prerequisites for the initiation and maintenance of this rhythm disturbance.

Phase image triangulation of accessory pathways in patients undergoing catheter ablation of posteroseptal pathways

The outcome of posteroseptal accessory pathway ablation by direct current (DC) shocks delivered just outside the os of the coronary sinus was studied in 21 patients. Electrocardiographic and electrophysiological parameters as well as phase image patterns of equilibrium multiple-gated blood-pool scintigrams were studied to determine their usefulness in predicting the success of ablation. A second free-wall pathway was documented by electrophysiological or surgical findings in six patients, and the value of phase images in detecting this second pathway was studied as well. Ablation was successful in 57%. The cumulative mean energy of DC shocks amounted to 524 +/- 170 joules and was not predictive of ablation outcome, neither was the mean ventriculoatrial (VA) conduction time. The predictive value of the 12-lead maximally preexcited electrocardiogram was poor in the 15 patients with a single posteroseptal bypass tract. A new method to triangulate the site of the earliest phase angle on the atrioventricular (AV) valve plane successfully localized the bypass pathway in 14 of those patients. No specific phase pattern predicted successful ablation except for a symmetrical, concentric peripheral phase progression found to be predictive of ablation success in the four patients who showed this pattern. Phase analysis was able to localize the second, nonposteroseptal pathway in four of six patients. This study showed that a concentric peripheral phase progression in the gated blood-pool scintigrams is predictive for ablation success in patients with posteroseptal pathways. A free-wall localization of the earliest phase angle is suggestive of a second bypass tract in this area.

A new method for estimating preexcitation index without extrastimulus technique and its usefulness in determining the mechanism of supraventricular tachycardia

The preexcitation index has been shown to be useful in determining the mechanism of paroxysmal supraventricular tachycardia (SVT) and the site of the accessory pathway in atrioventricular (AV) reentrant tachycardia. To test whether a preexcitation index could be computed analytically instead of by scanning the whole SVT cycle with extrastimuli, 19 patients with SVT were studied. The new index was computed using the following formula: (AV conduction time during SVT) + (ventriculoatrial conduction time during ventricular pacing at the SVT cycle length) - (SVT cycle length). There was a strong correlation between the preexcitation index determined by the extrastimulus technique and the new index in 15 patients in whom the preexcitation index could be determined (r = 0.99, p less than 0.01). The value on the new index was greater than 90 ms only in patients with dual AV nodal pathways. In the 4 patients in whom the preexcitation index could not be determined by the extrastimulus technique, the new index could differentiate AV reentrant tachycardia (index for 2 patients, 60 and 60 ms, respectively) from AV nodal reentrant tachycardia (index for 2 patients, 100 and 105 ms, respectively). In conclusion, the new index provided help in determining the mechanism of SVT, even when retrograde atrial preexcitation by a ventricular extrastimulus did not occur.

Entrainment onset in atrioventricular reciprocating tachycardia: value in bypass tract localization and relationship to the preexcitation index

The timing of entrainment onset has been shown to correlate with the conduction time to critical elements of a tachycardia circuit in a pacemaker model of reentrant ventricular tachycardia (VT). The utility of this method in evaluating clinical reentrant tachycardias was therefore evaluated in 24 patients with symptomatic Wolff-Parkinson-White syndrome and single bypass tracts (left free wall in 17, posteroseptal in 5, anteroseptal in 1, and right free wall in 1). Right ventricular apex (RVA) pacing during orthodromic atrioventricular reentrant tachycardia (oAVRT) at 10-70 msec less than tachycardia cycle length demonstrated concealed entrainment of the tachycardia in all patients studied. An entrainment index (EI), defined as the minimal prematurity of the ventricular stimulus that first resulted in atrial reset, was calculated from multiple entrainments in each patient. The EI was 121 +/- 25, 83 +/- 19, and 55 msec for left free wall, septal, and right free-wall bypass tracts, respectively (P = 0.004 for difference between left free wall and septal). A corrected EI, derived by subtracting the amount of atrial reset from the EI, gave values of 108 +/- 22 and 71 +/- 17 msec for left free wall and septal bypass tracts (P = 0.001). These values were compared to the preexcitation index (PI) by linear regression analysis in these patients. The PI correlated closely with both the EI and the corrected EI (r = 0.90 and 0.93, respectively), but the PI could only be derived in 12/17 (71%) left free-wall tachycardias versus the EI in 17/17 (100%) (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)