Optimal target temperature for slow pathway ablation in patients with atrioventricular nodal reentrant tachycardia

Objective To define optimal target temperature for the slow pathway ablation.Materials and methods In this study, 268 patients with atrioventricular nodal reentrant tachycardia (190 females; mean age, 49 ± 14 years) who underwent slow pathway ablation using a combined electroanatomic approach were enrolled. The patients were categorized into Group 1 if target temperature was <55°C or into Group 2 if target temperature was ≥55°C. Group 2 was divided into three subgroups of 55°C (Sgp-1), 60°C (Sgp-2), and 65°C (Sgp-3).Results Acute success rate was similar in both groups (P = 0.83). The ablation time (26.2 ± 20 vs. 36.5 ± 28 min; P = 0.014), fluoroscopy time (11.6 ± 9.7 vs. 17.8 ± 16.6 min; P = 0.035), and number of applications (4.1 ± 3.2 vs. 9.1 ± 6.5; P = 0.02) were lower for Group 2 than Group 1 patients. The frequency of AV or VA block, impedance rise, and coagulum formation were comparable in two groups (all P > 0.05). During mean follow-up of 14 ± 3 months, recurrence of the arrhythmia was seen in higher proportion of Group 1 than Group 2 patients (P = 0.036). Among the Group 2 patients, there were no significant differences between the three subgroups in terms of acute success rate, fluoroscopy time, risks of AV and VA block, pericardial effusion, and recurrence (All P > 0.05). Number of applications and RF pulse duration were lower in Sgp-2 and 3 compared to Sgp-1 (All P > 0.05). Impedance rise and coagulum formation were slightly higher in Sgp-3 compared to Sgp-1 and 2 but this difference did not reach statistical significance (All P > 0.05).Conclusions Compared to less than 55°C, target temperatures ≥55°C during slow pathway ablation significantly reduces fluoroscopy time, RF pulse duration, number of RF applications, and recurrence of AVNRT without increase in risk of AV or VA block or coagulum formation.     

Transverse versus longitudinal electrical propagation within the atrioventricular node during dual pathway conduction: Basis of dual pathway electrophysiology and His electrogram alternans (Zhang's phenomenon)

Background

We have discovered and validated that AV node dual pathway conduction results in a new phenomenon termed His electrogram alternans (HEA), which indicates dual inputs rather than a final common pathway from the AV node into the His bundle. However, the electrophysiological basis for AV node dual pathway conduction and HEA has not been clarified. This study was designed to elucidate the electrophysiological basis for dual pathway conduction and HEA.

Methods

By using HEA as an index of dual pathway electrophysiology, action potentials from multiple locations in the superior and inferior AV nodal domains were obtained to monitor electrical propagation during dual pathway conduction in 8 isolated rabbit hearts.

Results

Fibers inside the AV node were generally aligned along the AV conduction axis. During fast pathway (FP) conduction, electrical excitation in the AV node was propagated in a superior to inferior direction across the major fiber orientation. In contrast, slow pathway (SP) conduction occurred when the superior–inferior propagation failed within the superior nodal domain, permitting electrical propagation to proceed in the inferior nodal domain along the fiber orientation in a posterior to anterior direction. In effect, FP activated first the superior distal node, while SP activated first the inferior distal node. This functional dissociation of superior-fast and inferior-slow domains in distal node produced dual inputs into the His bundle.

Conclusions

Transverse versus longitudinal electrical propagation within the AV node produces functional dissociation in the distal node, resulting in superior-fast and inferior-slow inputs into the His bundle and HEA during dual pathway conduction.     

干预犬下腔静脉脂肪垫对窦房结及房室结功能的影响

目的通过不同干预方法,观察犬下腔静脉脂肪垫对窦房结及房室结功能的影响。方法选择16只犬开胸暴露下腔静脉脂肪垫,首先以固定的输出频率(20Hz)连续电刺激下腔静脉脂肪垫30 s,测量刺激前和刺激时窦房结恢复时间(SNRT)、校正SNRT(cSNRT)及AH、HV、RR间期变化;然后在直视下心外膜射频消融脂肪垫,再测定迷走神经刺激前后上述指标的变化。结果:14只完成试验。当电刺激下腔静脉脂肪垫时,AH间期与刺激前比较明显延长(122.2±12.4 m s vs 82.5±10.3 m s,P<0.05),其余指标未发生明显变化。电刺激通常在2 s内起效,AH间期随刺激电压增加而延长,在刺激停止3 s内恢复。射频消融下腔静脉脂肪垫后,刺激左右颈部迷走神经,SNRT、cSNRT及RR间期与刺激前比较有明显变化(分别为696.4±54.9 m s vs 467.5±45.4 m s;296.3±20.5 m svs 164.5±20.1 m s,400.3±39.1 m s vs 210.1±14.5 m s,P均<0.05),但AH间期及HV间期未发生明显变化。结论:刺激下腔静脉脂肪垫可使房室传导延迟,而不影响窦房结功能。消融下腔静脉脂肪垫可以消除迷走神经对房室结的支配。     

射频导管消融慢径路治疗程控刺激不能诱发且无明显跳跃的房室结折返性心动过速疗效分析

目的观察无A—H间期跳跃和不能诱发的房室结折返性心动过速（AVNRT）慢径路消融特点和远期疗效。方法经电生理检查证实无旁道参与的阵发性室上性心动过速患者100例,分成三组：能诱发AVNRT,有明显跳跃（A组,n=40）;不能诱发AVNRT,但有A—H间期〉50ms的明显跳跃（B组,1=40）;不能诱发AVNRT且没有A—H间期〉50ms的明显跳跃（C组．n=20）。比较术后各组电生理数值及消融远期疗效。结果与消融术前相比．术后各组患者的房室结顺传文氏周期均延长（P〈0．05）;消融术后房室结顺传有效不应期较术前缩短,差异有统计学意义（P〈0．05）;三组均出现缓慢交接区心律。术后随访12个月．各组复发率差异无统计学意义（P〉0．05）。结论无A—H间期跳跃且程控刺激不能诱发的AVNRT的慢径路消融是安全有效的。缓慢交接区心律是消融有效的标志。     

Rationale and design of the AdaptResponse trial: a prospective randomized study of cardiac resynchronization therapy with preferential adaptive left ventricular‐only pacing

The AdaptResponse trial is designed to test the hypothesis that preferential adaptive left ventricular‐only pacing with the AdaptivCRT^® algorithm reduces the incidence of the combined endpoint of all‐cause mortality and intervention for heart failure (HF) decompensation, compared with conventional cardiac resynchronization therapy (CRT), among patients with a CRT indication, left bundle branch block (LBBB) and normal atrioventricular (AV) conduction. The AdaptResponse study is a prospective, randomized, controlled, single‐blinded, multicentre, clinical trial ( ClinicalTrials.gov Identifier: NCT02205359), conducted at up to 200 centres worldwide. Following enrolment and baseline assessment, eligible subjects will be implanted with a CRT system containing the AdaptivCRT algorithm, and randomized in a 1:1 fashion to either a treatment (‘AdaptivCRT’) or control (‘Conventional CRT’) group. The study is designed to observe a primary endpoint in 1100 patients (‘event‐driven’) and approximately 3000 patients will be randomized. The primary endpoint is the composite of all‐cause mortality and intervention for HF decompensation; secondary endpoints include all‐cause mortality, intervention for HF decompensation, clinical composite score (CCS) at 6 months, atrial fibrillation, quality of life measured by the Kansas City Cardiomyopathy Questionnaire (KCCQ), health outcome measured by the EQ‐5D instrument, all‐cause readmission after a HF admission, and cost‐effectiveness. The AdaptResponse clinical trial is powered to assess clinical endpoints and is expected to provide definitive evidence on the incremental utility of AdaptivCRT‐enhanced CRT systems.     

腺苷对家兔心脏房室结区不同细胞的动作电位的影响

为探讨房室交界区各部位的电生理特性以及腺苷对各部位的动作电位特性的影响，本文对20只家兔制作了房室结立体标本，用标准微电极技术法记录了不同部位房结区（AN）、结区（N）、结希区（NH）以及冠状窦口周围和三尖瓣，二尖瓣房室环上的动作电位形态及腺苷对其的影响。结果表明似房结区，似结区及似结希区的动作电位图形分布广泛，除在传统的房室结可记录到此组动作电位图形外，在冠状窦及房室环周围也可记录到类似图形。腺苷对各区细胞的作用也明显不同，其共同的作用为缩短动作电位时程，减慢心率。结果提示房室交界区或称为广义的房室结是一结构和功能复杂的结合体，对其结构和功能结合起来研究才能真正了解其电生理特性。     

家兔房室交界区的形态学观察及其意义

目的:观察家兔心房室结周围的纤维联系,探讨结间传导及折返机制。方法:选20只家兔心脏做房室交界区水平面及矢状面连续切片,HE染色光学显微镜下观察并拍照。结果:房间隔主要观察到3种形态的细胞,P细胞、T细胞和普通心房肌细胞。房室结由致密结和后延伸两部分组成。致密结分浅、深两层。房室结周围有3条纤维与之相连。后方为两束过渡纤维,分别源于冠状窦口及其下方,上方通过普通房肌与下房间隔相连。各肌纤维之间形成回路。结论:结间传导存在着形态学证据,肌纤维形成的回路很可能成为兴奋发生转折的部位。     

心腔内超声引导下希氏束起搏和房室结消融

目的　建立心腔内超声和组织多普勒显像技术引导监控下的希氏束起搏和房室结消融方法。方法　 6只犬急性闭胸模型。经颈静脉插入超声导管确定希氏束和房室结准确空间位置、超声解剖结构标志及其内心肌激动顺序。引导心脏起搏或消融导管到达靶组织 ,监控刺激电极植入过程和确认消融电极与心内膜面接触。分别释放电脉冲进行靶点起搏和射频消融 ,同步体表心电图QRS波形态确认实现希氏束起搏和Ⅲ度房室传导阻滞。结果　实现了直接希氏束起搏 (1例 )和希氏束加室间隔起搏 (5例 )。希氏束起搏阈值为 :电压 (3 .0± 1 .0 )V ,脉宽 0 .5ms。希氏束起搏时导致了较早的室间隔电兴奋。窦性心律和希氏束起搏时QRS波宽度分别为 (59.7± 5 .3)ms和 (82 .8± 1 6 .6)ms (P =0 .0 2 )。完成希氏束起搏和房室结消融的平均操作时间分别为 40min(3～ 81min)和 3min(2～ 5min) ;平均X线曝光时间为 1 3min(1～ 55min)。病理解剖和组织切片表明希氏束起搏和房室结消融定位准确、效果肯定。结论　心腔内超声技术能够准确引导心脏介入导管实现希氏束起搏和房室结消融 ,减少导管操作和X线曝光时间     

经食管超声心动图技术和临床应用——附36例临床分析

本文总结了用TEE检查36例患者的临床应用价值。最小年龄12岁,清醒患者17例,手术患者19例。结果显示,TEE检查是相当安全和可行的,与检查者操作技术密切有关;TEE清晰显示深层解剖结构如房间隔、房室瓣和肺静脉的病变优于胸前超声;TEE用于手术中监测瓣膜成形、替换及先心病矫正有重要意义