Para-Hisian entrainment: a novel pacing maneuver to differentiate orthodromic atrioventricular reentrant tachycardia from atrioventricular nodal reentrant tachycardia

INTRODUCTION: Para-Hisian pacing during sinus rhythm can help to identify the presence of an accessory pathway (AP). In this maneuver, the retrograde activation time and pattern are compared during capture and loss-of-capture of the His bundle while pacing from a para-Hisian position. However, identification of a retrograde AP does not necessitate that it is operative during the tachycardia of interest; conversely, slowly conducting or "distant" bypass tracts may not be identified. We evaluated the utility of entrainment or resetting of tachycardias from the para-Hisian position to help distinguish atrioventricular nodal reentrant tachycardia (AVNRT) from orthodromic atrioventricular tachycardia (AVRT). METHODS AND RESULTS: Para-Hisian entrainment/resetting was evaluated in 50 patients: 33 with AVNRT and 17 with AVRT. The maneuvers were performed using a standard quadripolar catheter placed at the His position: low output for right ventricular (RV) capture and high output for both RV and His capture. The retrograde atrial activation sequence, SA interval (interval from stimulus to earliest retrograde atrial activation), and "local" VA interval (interval between the ventricular and atrial electrograms at the site of earliest retrograde atrial activation) were compared between His and His/RV capture. The DeltaSA was > 40 ms in patients with AVNRT and was < 40 ms in all but one patient with AVRT. In concert with the DeltaSA interval, the DeltaVA interval was able to fully define the mechanism of the tachycardia in all patients studied. CONCLUSION: Para-Hisian entrainment/resetting can determine the course of retrograde conduction operative during narrow complex tachycardias. It is a useful diagnostic maneuver in differentiating AVNRT and orthodromic AVRT.     

Differentiating atrioventricular nodal reentrant tachycardia from tachycardia via concealed accessory pathway

Studies analyzing the diagnostic value of 12-lead electrocardiographic criteria differentiating slow-fast atrioventricular nodal reentrant tachycardia (AVNRT) from atrioventricular reentrant tachycardia (AVRT) due to concealed accessory pathway have shown inconsistent results. In 97 patients (50 with AVNRT, 47 with AVRT) 12-lead electrocardiograms (ECGs) were recorded during sinus rhythm and tachycardia (QRS <120 ms). The ECGs were blinded for diagnosis and patient and analyzed independently by 2 electrophysiologists. The studied criteria differentiating AVNRT from AVRT included pseudo-r'/S, the presence of a retrograde P wave, RP interval, ST-segment depression >/=2 mm with the number and location of the affected leads, QRS amplitude, and cycle length alternans.     

Electrocardiographic differentiation of typical atrioventricular node reentrant tachycardia from atrioventricular reciprocating tachycardia mediated by concealed accessory pathway in children

The value of the electrocardiogram (ECG) in children with supraventricular tachycardia (SVT) is unclear. The noninvasive differentiation of typical atrioventricular node reentrant tachycardia (AVNRT) and atrioventricular reciprocating tachycardia (AVRT) mediated by concealed accessory pathway conduction is clinically important, as it helps in counseling and potentially facilitates ablation procedures. One hundred forty-eight ECGs showing narrow QRS complex SVT were obtained from children before successful radiofrequency catheter ablation. An initial 102 ECGs were analyzed by 3 blinded observers to assess the utility of various electrocardiographic findings. No electrocardiographic criteria were found to discriminate between SVT mechanisms on 1- to 3-channel Holter/event recorder tracings (n = 32); their interpretation mainly (55%) resulted in an incorrect SVT diagnosis. On 12-lead ECGs (n = 70), the 2 arrhythmias were accurately diagnosed in 76% of patients; 5 findings were found to be discriminators of tachycardia mechanism. Predictors of AVRT were visible P waves in 74% of cases (sensitivity 92%; specificity 64%), RP intervals of > or =100 ms in 91% (sensitivity 84%; specificity 91%), and ST-segment depression of > or =2 mm in 73% of cases (sensitivity 52%; specificity 82%). Pseudo r' waves in lead V(1) and pseudo S waves in the inferior leads during tachycardia predicted AVNRT in 100% of cases (sensitivity 55% and 20%, respectively; specificity 100% for both). Based on these results, we developed a new diagnostic 12-lead electrocardiographic algorithm for pseudo r'/S waves, RP duration, and ST-segment depression during tachycardia. Two observers tested the algorithm in 46 (21 AVNRT; 25 AVRT) additional cases; they correctly diagnosed the SVT mechanism in 91% and 87%, respectively. Thus, the stepwise use of diagnostically relevant 12-lead electrocardiographic parameters helps to more accurately differentiate mechanisms of reentrant SVT.     

Entrainment phenomenon of atrioventricular nodal reentrant and atrioventricular reentrant tachycardias]

Atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT) were induced by esophageal pacing and their entrainment zones were examined in 20 patients. The results showed that the entrainment phenomenon, which was a common electrophysiological phenomenon in reentrant tachycardia, occurred during overdrive pacing in 19 cases (19/20). The entrainment zone was 10-70 (30.50 +/- 20.85, mean +/- s) ms. The tachycardias could not be interrupted by pacing within the entrainment zone, but they were terminated by burst pacing, with starting pacing cycle length shorter than the shortest entrainment cycle length.     

希氏束旁起搏鉴别间隔部隐匿性AVRT与AVNRT的临床价值

目的：探讨希氏束旁起搏鉴别间隔部隐匿性房室旁道与慢一快型房室结折返性心动过速（AVNRT）的临床价值。方法：采用希氏束逆传不应期心室早搏刺激法将61例患者分别诊断为37例慢一快AVNRT和24例间隔部房室折返性心动过速（AVRT）；再对61例患者采用希氏束旁起搏方法进一步检测。结果：采用希氏束旁起搏法检测37例AVNRT患者中有6例未检测成功，其余31例均为逆传房室结图形；24例AVRT患者中4例未检测成功，15例呈逆传旁道／旁道图形，5例呈非逆传旁道／旁道图形。如以逆传旁道／旁道图形为标准，鉴别间隔快旁路引起的AVRT与慢一快型房室结折返性心动过速，敏感性75％，特异性可达1009／6。结论：希氏束旁刺激法对鉴别诊断AVRT与AVNRT有较高的特异性。     

房室折返和房室结折返性心动过速患者的个性分析

目的探讨房室折返性心动过速(AVRT)和房室结折返性心动过速(AVNRT)患者的个性特征。方法采用龚耀先修订的艾森克个性问卷量表,对83例AVRT、105例AVNRT患者射频消融前后和50例对照组正常人的精神质(P)、内外向(E)、情绪稳定性(N)和掩饰倾向(L)值进行测量。结果射频消融前后,各组之间的P、E、N和L值相比较差异无显著性(P>0.05);射频消融前后AVNRT组内女性患者的N分值较男性高(分别为12.93±2.83vs9.88±2.61;12.84±2.87vs9.87±2.64;P均<0.05)。结论AVNRT女性患者具有神经质倾向,这可能是在AVNRT中女性占多数的原因之一。     

Clinical and electrophysiological characteristics in patients with atrioventricular reentrant and atrioventricular nodal reentrant tachycardia.

AIM: To compare clinical, electrophysiological characteristics and transcatheter ablation results between two groups of patients, one with atrioventricular reentrant tachycardia (AVRT) and the other with atrioventricular nodal reentrant tachycardia (AVNRT). METHODS: The study population consisted of 94 consecutive patients who underwent endocavitary electrophysiological study and radiofrequency (RF) ablation: 46 patients had AVRT due to an accessory pathway with only retrograde conduction while 48 patients had AVNRT. RESULTS: In relation to general and clinical characteristics, differences between the two groups emerged regarding the age of symptom onset (25+/-16 vs 37+/-17 years, p=0.001), the prevalence of heart disease (8 vs 31%, p=0.001) and the correct diagnosis on surface ECG (50 vs 79%, p=0.001). Clinical presentation was quite similar apart from a higher prevalence of fatigue and sweating in the AVNRT group. Transcatheter RF ablation therapy results were similar. CONCLUSIONS: Patients with AVRT have a lower mean age at arrhythmia symptom onset compared with those with AVNRT and have fewer associated cardiac abnormalities. Clinical presentation is quite similar as well as their outcome after ablation. A correct diagnosis by standard ECG is more frequent in AVNRT.     

心室起搏拖带对房室结折返性和间隔旁路参与的房室折返性心动过速的鉴别作用

目的　研究心动过速时心室起搏拖带对房室结折返性心动过速 (AVNRT )和间隔旁路参与的顺向型房室折返性心动过速 (间隔旁路ORT)的鉴别意义。方法　 30例AVNRT和 2 5例间隔旁路ORT病人在心动过速发生后 ,采用较心动过速的周长 (TCL)短 10～ 4 0ms的周长行右心室起搏拖带心动过速。测量右心室起搏之前的心室 心房 (VA)间期和TCL。停止起搏后 ,测量最后一次刺激信号至最后起搏拖带的心房激动 (SA)间期 ,以及起搏后间期 (PPI)。结果　所有 30例AVNRT病人的SA -VA间期 >85ms、PPI-TCL >115ms,而 2 5例ORT病人的SA -VA间期 <85ms、PPI-TCL <115ms。结论　PPI TCL和SA VA间期是鉴别AVNRT和间隔旁路ORT的非常可靠的指标 ,具有较高的特异性。     

A new criterion to differentiate atrioventricular nodal reentrant tachycardia from atrioventricular reciprocating tachycardia: Combined AVR criterion

Aim

A combined aVR criterion is described as the presence of a pseudo r′ wave in aVR during tachycardia in patients without r′ wave in aVR in sinus rhythm and/or a ≥50% increase in r′ wave amplitude compared to sinus rhythm in patients with r′ wave in the basal aVR lead. We aimed to investigate the use of combined aVR criterion in differential diagnosis of atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reciprocating tachycardia (AVRT).

心房不同部位拖带法鉴别不典型房室结折返性心动过速和房性心动过速

目的报道一种鉴别不典型房室结折返性心动过速(AVNRT)和起源点邻近Kock三角的房性心动过速(AT)的新方法。方法 22例室上性心动过速患者,在心房不同部位(右房心耳部、冠状静脉窦近端、远端)起搏拖带心动过速,测定起搏后VA间期(最后一个起搏脉冲前传夺获的心室电图到起搏终止后第一心搏的最早心房电图的距离)。计算各部位起搏后VA间期的差别并取差别绝对数的最大值定义为ΔVA间期。结果 13例AVNRT起搏后ΔVA间期5.8±3.6(0～14)ms,9例AT起搏后ΔVA间期62.8±24.2(21～98)ms。ΔVA间期在所有AVNRT均<15 ms,在所有AT均>15 ms,因此起搏后ΔVA间期>15 ms用于诊断AT的灵敏度和特异度均为100%。结论心房不同部位起搏拖带法可用于准确鉴别不典型AVNRT和起源点邻近Kock三角的AT。     

Paradoxical responses to pacing maneuvers differentiating atrioventricular node reentrant tachycardia and junctional tachycardia

A 40-year-old female presented at our hospital because of heart palpitations. During an electrophysiological study, atrioventricular (AV) conduction showed dual AV nodal physiology. Three types of supraventricular tachycardia (SVT) were induced. The initiation of SVT was reproducibility dependent on a critical A–H interval prolongation. An early premature atrial contraction during SVT repeatedly advanced the immediate His potential with termination of the tachycardia, indicating AV node reentrant tachycardia (AVNRT). However, after atrial overdrive pacing during SVT without termination of the tachycardia, the first return electrogram resulted in an AHHA response, consistent with junctional tachycardia. The mechanism of paradoxical responses to pacing maneuvers differentiating AVNRT and junctional tachycardia was discussed.     

Significance of bundle branch block during atrioventricular nodal reentrant tachycardia

There are very limited data on the effects of bundle branch block (BBB) in patients with atrioventricular nodal reentrant tachycardia (AVNRT). Studies in a total of 155 patients with 162 episodes of AVNRT were retrospectively analyzed. A total of 38 patients (25%) developed spontaneous right BBB, whereas 5 (3%) developed left BBB during tachycardia. Five of the 38 (13%) with right BBB showed near identical prolongation of both the ventriculoatrial (VA) (15 +/- 5 ms; 10 to 23) and His to atrial intervals (HA) (14 +/- 4 ms; 10 to 20) with an identical atrial activation sequence for both right BBB or normal QRS tachycardia complexes. In contrast, all 5 patients with left BBB showed a decrease in the VA (-18 +/- 11 ms; 10 to 36) with unchanged HA comparing left BBB to normal QRS patterns during AVNRT. The magnitude of prolongation of the His to ventricular interval (HV) during left BBB (19 +/- 12 ms; 10 to 40) was nearly identical to the decrease in the VA. In conclusion, prolongation of VA and HA with unchanged HV in patients with AVNRT and right BBB suggests that right BBB is due to a block in the fibers in close proximity to the His recording site. The data suggest that fibers in the His bundle are predestined to activate the right bundle branch, and in AVNRT the lower turnaround point may be within the His bundle.     

Differentiating atrioventricular nodal reentrant tachycardia from junctional tachycardia: novel application of the delta H-A interval

Introduction: Junctional tachycardia (JT) and atrioventricular nodal reentrant tachycardia (AVNRT) can be difficult to differentiate. Yet, the two arrhythmias require distinct diagnostic and therapeutic approaches. We explored the utility of the delta H-A interval as a novel technique to differentiate these two tachycardias.
Methods: We included 35 patients undergoing electrophysiology study who had typical AVNRT, 31 of whom also had JT during slow pathway ablation, and four of whom had spontaneous JT during isoproterenol administration. We measured the H-A interval during tachycardia (H-A_T) and during ventricular pacing (H-A_P) from the basal right ventricle. Interobserver and intraobserver reliability of measurements was assessed. Ventricular pacing was performed at approximately the same rate as tachycardia. The delta H-A interval was calculated as the H-A_P minus the H-A_T.
Results: There was excellent interobserver and intraobserver agreement for measurement of the H-A interval. The average delta H-A interval was −10 ms during AVNRT and 9 ms during JT (P < 0.00001). For the diagnosis of JT, a delta H-A interval ≥ 0 ms had the sensitivity of 89%, specificity of 83%, positive predictive value of 84%, and negative predictive value of 88%. The delta H-A interval was longer in men than in women with JT, but no gender-based differences were seen with AVNRT. There was no difference in the H-A interval based on age ≤ 60 years.
Conclusion: The delta H-A interval is a novel and reproducibly measurable interval that aids the differentiation of JT and AVNRT during electrophysiology studies.     

Anteroseptal basal right ventricular entrainment is simple and superior to apical entrainment in identifying mechanism of supraventricular tachycardia

Background

Differentiation between atrioventricular nodal reentry tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT) can be sometimes challenging. Apical right ventricular (RV) entrainment can help in differentiation; however, it has some fallacies. We thought to compare the accuracy of anteroseptal basal RV entrainment to RV apical entrainment in identifying the mechanism of supraventricular tachycardia (SVT).

Methods

Forty-two consecutive patients with SVT who underwent catheter ablation were prospectively studied. Apical RV entrainment was performed initially followed by basal entrainment from the anteroseptal basal RV avoiding His or atrial capture. Postpacing interval (PPI), PPI–tachycardia cycle length (TCL), corrected PPI-TCL, and stimulus–atrial minus ventricular–atrial (VA) intervals were measured.

Results

Entrainment was achieved from both sites of RV in 34 patients (ten men; mean age 42?±?15 years), 20 with typical AVNRT, 1 with atypical AVNRT, and 13 with AVRT (eight left sided, four right sided, and one septal accessory pathways). PPI-TCL, corrected PPI (cPPI)-TCL, and stimulus–atrial–VA intervals were significantly longer with basal entrainment in AVNRT (171?±?30 vs. 153?±?22 ms (p?=?0.003), 148?±?21 vs. 131?±?20 ms (p?=?0.002), and 145?±?17 vs. 136?±?15 ms (p?=?0.005), respectively). Receiver-operating characteristic curves showed higher AUC for the above parameters with basal entrainment compared to apical entrainment. Cutoff values of basal PPI-TCL of >110 ms and cPPI-TCL of >95 ms had better sensitivities (100 % for both vs. 95 and 90 %, respectively, for apical values) and specificities (85 and 92 % vs. 77 and 92 %, respectively) for diagnosis of AVNRT.

Conclusion

Basal RV entrainment from the anteroseptal basal RV is a simple maneuver that is superior to apical ventricular entrainment in identifying the mechanism of SVT.     

Differences in ventriculoatrial intervals during entrainment and tachycardia: a simpler method for distinguishing paroxysmal supraventricular tachycardia with long ventriculoatrial intervals

VA Intervals to Distinguish PSVT. Introduction: Usefulness of the interval between the last pacing stimulus and the last entrained atrial electrogram (SA) minus the tachycardia ventriculoatrial (VA) interval in the differential diagnosis of supraventricular tachycardias with long (>100 ms) VA intervals has not been prospectively studied in a large series of patients. Our objective was to assess the usefulness of the difference SA–VA in diagnosing the mechanism of those tachycardias in patients without preexcitation. The results were compared with those obtained using the corrected return cycle (postpacing interval—tachycardia cycle length—atrioventricular [AV] nodal delay). Methods and Results: We included 314 consecutive patients with inducible sustained supraventricular tachycardias with VA intervals >100 ms undergoing an electrophysiologic study. Atrial tachycardias were excluded. Tachycardia entrainment was attempted through pacing trains from right ventricular apex. The SA–VA difference and the corrected return cycle were calculated for every patient. Electrophysiologic study revealed 82 atypical AV nodal reentrant tachycardias (AVNRT) and 237 AV reentrant tachycardias (AVRT) using septal (n = 91) or free‐wall (n = 146) accessory pathways (APs). A SA–VA difference >110 ms identified an atypical AVNRT with sensitivity, specificity, positive and negative predictive values of 99%, 98%, 95%, and 99.5%, respectively. Similarly, these values were 88%, 83%, 77%, and 92% for SA–VA difference <50 ms in identifying AVRT through a septal versus free‐wall AP. The SA–VA difference showed higher accuracy in septal AP identification than that obtained using the corrected return cycle. Conclusion: The difference SA–VA provides a simpler electrophysiologic maneuver that reliably differentiates atypical AVNRT from AVRT regardless of concealed AP location . (J Cardiovasc Electrophysiol, Vol. 22, pp. 915‐921, August 2011)     

Participation of a concealed atriohisian tract in the reentrant circuit of the slow-fast type of atrioventricular nodal reentrant tachycardia.

BACKGROUND: The retrograde fast pathway in typical atrioventricular nodal reentrant tachycardia (AVNRT) exhibits marked variation in its electrophysiologic properties. OBJECTIVE: The purpose of this study was to characterize the retrograde fast pathway and localize the lower turnaround site of the reentrant circuit in typical AVNRT. METHODS: Seventy-four patients with typical AVNRT were divided into two groups according to the response of the retrograde fast pathway to intravenous administration of adenosine triphosphate (ATP) during ventricular pacing: ATP-S [n = 47 (63.5%)] with and ATP-R without [n = 27 (36.5%)] His-atrial (H-A) block. H-A intervals were measured from the most proximal His-bundle electrogram to the earliest atrial activation during the tachycardia (HAt) and entrainment pacing from the parahisian right ventricular region (HAe). It was postulated that the HAt was the difference in conduction time between the lower common pathway (x) and retrograde fast pathway (y) (HAt = y - x), whereas HAe was the sum of the two (HAe = y + x). Hence, x = (HAe-HAt)/2. x >0 suggested the presence of a lower common pathway, whereas x <0 suggested the absence of a lower common pathway and lower turnaround site within the His bundle. RESULTS: x was significantly smaller in ATP-R than ATP-S (-6 +/- 5 vs 4 +/- 4 ms, P <.05) and was <0 in 23 (85%) of 27 ATP-R patients. The maximal increment in H-A interval during ventricular pacing was significantly longer in ATP-S than ATP-R (35 +/- 33 vs 2 +/- 2 ms, P <.05). CONCLUSION: A concealed atriohisian tract totally bypassing the atrioventricular node constituted the retrograde fast pathway in one third of all typical AVNRT cases.     

Subthreshold stimulation in three types of reentrant supraventricular tachycardia: correlation with the results of catheter ablation.

The effects of subthreshold stimulation (STS) by direct current were investigated in 20 patients with atrioventricular nodal reentrant tachycardia (AVNRT), 27 with atrioventricular reentrant tachycardia (AVRT) and 3 with idiopathic atrial reentrant tachycardia (IART) STS was delivered to each eligible site for ablation prior to radiofrequency application. STS was defined as 'positive' if it could terminate the tachycardia or disrupt the conduction of accessory pathways without myocardial capture and defined as 'negative' if it could not. Radiofrequency ablation was performed irrespective of a positive or negative result from STS and was successful in all 50 patients. Among the 50 successful ablation sites, STS was positive at 26 sites (11 sites in AVNRT, 12 in AVRT and 3 in IART). STS was positive at 4 sites where ablation failed in 3 patients with AVRT and was negative at 8 sites where ablation was successful in 4 patients with AVNRT and 4 with AVRT. The positive and negative predictive value of STS for the detection of the optimal ablation site were, respectively, 100% and 74% in AVNRT, 73% and 72% in AVRT, and both 100% in IART STS-guided mapping is a specific method to predict the successful catheter ablation of reentrant supraventricular tachycardia.     

Unique electrophysiologic characteristics of atrioventricular nodal reentrant tachycardia with different ventriculoatrial block patterns: Effects of slow pathway ablation and insights into the location of the reentrant circuit

BACKGROUND: The electrophysiologic mechanisms of different ventriculoatrial (VA) block patterns during atrioventricular nodal reentrant tachycardia (AVNRT) are poorly understood. OBJECTIVES: The purpose of this study was to characterize AVNRTs with different VA block patterns and to assess the effects of slow pathway ablation. METHODS: Electrophysiologic data from six AVNRT patients with different VA block patterns were reviewed. RESULTS: All AVNRTs were induced after a sudden AH "jump-up" with the earliest retrograde atrial activation at the right superoparaseptum. Different VA block patterns comprised Wenckebach His-atrial (HA) block (n = 4), 2:1 HA block (n = 1), and variable HA conduction times during fixed AVNRT cycle length (CL) (n = 1). Wenckebach HA block during AVNRT was preceded by gradual HA interval prolongation with fixed His-His (HH) interval and unchanged atrial activation sequence. AVNRT with 2:1 HA block was induced after slow pathway ablation for slow-slow AVNRT with 1:1 HA conduction, and earliest atrial activation shifted from right inferoparaseptum to superoparaseptum without change in AVNRT CL. The presence of a lower common pathway was suggested by a longer HA interval during ventricular pacing at AVNRT CL than during AVNRT (n = 5) or Wenckebach HA block during ventricular pacing at AVNRT CL (n = 1). In four patients, HA interval during ventricular pacing at AVNRT CL was unusually long (188 +/- 30 ms). Ablations at the right inferoparaseptum rendered AVNRT noninducible in 5 (83%) of 6 patients. CONCLUSION: Most AVNRTs with different VA block patterns were amenable to classic slow pathway ablation. The reentrant circuit could be contained within a functionally protected region around the AV node and posterior nodal extensions, and different VA block patterns resulted from variable conduction at tissues extrinsic to the reentrant circuit.     

射频消融治疗房室结或房室折返性心动过速的多中心随机临床试验

目的 通过与国外进口温控射频消融导管的比较,评价国产温控射频消融导管在房室结折返性心动过速(AVNRT)和房室折返性心动过速(AVRT)的临床疗效和安全性.方法 自2008年6月至11月共入选AVNRT或AVRT患者1342例.采用多中心随机平行对照开放试验设计,应用解放军第四军医大学设计的最小化随机统计方法进行动态随机分为二组,国产导管组应用国产温控射频消融导管,进口导管组应用强生或圣犹达等公司的进口温控射频消融导管.采用常规方法在X线透视下进行心内电生理检查和射频消融.结果 国产导管组672例,即时消融成功率97.9%,进口导管组670例,即时消融成功率99.1%,两组成功率均达到96.0%以上,差异无统计学意义.国产导管组与进口导管组的手术时间[(68±36)min与(67±34)min]、曝光时间[(14±14)min与(10±11)min]、放电次数[(4.5±4.5)次与(4.6±3.9)次]、放电时间[(260±218)s与(257±207)8]、导管性能总体评分[(4.4±0.5)分与(4.5±0.4)分],两组间差异均无统计学意义.发生并发症3例,均为心包积液(国产导管组1例,进口导管组2例),经心包穿刺引流后转为正常出院,差异无统计学意义.随访3个月,复发30例,分别为国产导管组14例、进口导管组16例(2.1%与2.4%),差异无统计学意义.结论 国产温控射频消融导管可安全有效治疗AVNRT或AVRT.     

Unusual induction of slow-fast atrioventricular nodal reentrant tachycardia. Report of two cases

INTRODUCTION: Generally, the induction of typical atrioventricular nodal reentrant tachycardia (AVNRT) occurs with a premature atrial stimulus that blocks in the fast pathway and proceeds down the slow pathway slowly enough to allow the refractory fast pathway time to recover. We describe two cases in which a typical AVNRT was induced in an unusual fashion. RESULTS: The first case is a 41-year-old man with paroxysmal supraventricular tachycardia. During the electrophysiology study, the atrial extrastimulus inducing the typical AVNRT was conducted simultaneously over the fast (AH) and the slow pathway (AH'). A successful ablation of the slow pathway was performed. During the follow-up no recurrence was noted. The second case is a 52-year-old woman with a Wolff-Parkinson-White syndrome due to a left posterior accessory pathway. After 5 minutes of atrioventricular reentrant tachycardia (AVRT) induced by a ventricular extrastimulus, a variability of the antegrade conduction was noted in presence of the same VA conduction. In fact, a short AH interval (fast pathway) alternated with a more prolonged AH intervals (slow pathway) that progressively lengthened until a typical AVNRT was induced. The ablation of the accessory pathway eliminated both tachycardias. DISCUSSION: A rare manifestation of dual atrioventricular nodal pathways is a double ventricular response to an atrial impulse that may cause a tachycardia with an atrioventricular conduction of 1:2. In our first case, an atrial extrastimulus was simultaneously conducted over the fast and the slow pathway inducing an AVNRT. This nodal reentry implies two different mechanisms: 1) a retrograde block on the slow pathway impeding the activation of the slow pathway from the impulse coming down the fast pathway, and 2) a critical slowing of conduction in the slow pathway to allow the recovery of excitability of the fast pathway. Interestingly, in the second case, during an AVRT the atrial impulse suddenly proceeded alternately over the fast and the slow pathway. The progressive slowing of conduction over the slow pathway until a certain point which allows the recovery of excitability of the fast pathway determines the AVNRT. This is a case of "tachycardia-induced tachycardia" as confirmed by the fact that the ablation of the accessory pathway eliminated both tachycardias.