Activation Effects of Single-Site and Dual-Site Right Atrial Pacing in Canine

Medical therapy for managing atrial fibrillation remains less than satisfactory. Electrical therapy such as right atrial (RA) pacing was shown to reduce rate of recurrence of atrial fibrillation, while evidently dual-site pacing was more effective than single-site pacing. However, similarities and/or differences in the electrophysiological consequences of single-site and dual-site RA pacing are unclear. Our objective was to simultaneously map RA and left atrial (LA) activation patterns and compare intra-atrial and interatrial activation properties during single-site and dual-site RA pacing in the normal canine heart. Basket-shaped catheters carrying 64 electrodes were deployed under the guidance of fluoroscopy and echocardiography into both the RA and LA of 7 dogs. Basket unipolar electrograms were simultaneously recorded while pacing at high lateral RA (HRA) alone, at inferior RA septum (RAS) alone, and at both sites simultaneously. We found that pacing at HRA alone resulted in the longest interatrial conduction time (47±6[emsp4 ]ms). Pacing at RAS alone significantly shortened interatrial conduction time (29±5[emsp4 ]ms) and completely activated both the RA and LA simultaneously (70±6[emsp4 ]ms and 69±8[emsp4 ]ms, respectively). Dual-site pacing at HRA and RAS significantly abbreviated RA complete activation time (52±7[emsp4 ]ms), but did not alter interatrial conduction time or LA activation pattern compared to pacing at RAS alone. In conclusion, single-site pacing at RAS shortened interatrial conduction time compared to HRA and completely activated both atria simultaneously in canines with normal atria. In addition to shortening interatrial conduction time, dual-site pacing at HRA and RAS abbreviated RA complete activation time.     

特发性左室室性心动过速非接触球囊导管系统的标测与消融

介绍非接触球囊导管标测系统 (EnSite 30 0 0系统 )指导难治性特发性左室室性心动过速的标测与射频消融的初步经验。 5例男性病人 ,年龄 33± 17(17～ 6 2 )岁 ,常规方法标测和导管消融失败 2 .4± 1.1(1～ 4)次。常规放置高位右房和右室电生理导管 ,运用置入左室的 6 4极球囊导管和大头电极 ,系统重建三维心内膜几何模型和等电势 ,经右室导管诱发VT ,心动过速周期为 32 3.8± 48.1ms。EnSite 30 0 0系统标测到VT的最早激动点分别位于左后间隔中下部、左侧间隔后下部左束支下方、后下间隔近心尖部、左室后壁近基底部和左后间隔中部。在最早激动点和关键峡部分别行点状、环状和线性消融。 2例患者在心动过速时放电、3例患者在窦性心律时消融 ,均获成功。成功消融靶点处的单极电图均为QS型。X线曝光时间为 2 5± 12min。随访 7.8± 4.6 (1～ 11)个月所有患者均未发作心动过速。结果表明 ,与常规方法比较 ,EnSite 30 0 0系统所建立的心腔三维模拟等电势图可直观地显示心动过速的起源点、传导途径和关键峡部 ,系统模拟的单极腔内电图的形态也有助于判断病灶起源部位及提高消融成功率 ,尤其适用于常规方法消融失败的室性心律失常的标测 ,其独特的导航系统可引导消融导管到达靶点部位指导射频消融 ,并可减少X?     

T Wave Alternans During Exercise and Atrial Pacing in Humans

T Wave Alternans in Humans. Introduction: Evidence is accumulating that microvolt T wave alternans (TWA) is a marker of increased risk for ventricular tachyarrhythmias. Initially, atrial pacing was used to elevate heart rate and elicit TWA. More recently, a noninvasive approach has been developed that elevates heart rate using exercise.
Methods and Results: In 30 consecutive patients with a history of ventricular tachyarrhythmias, the spectral method was used to detect TWA during both atrial pacing and submaximal exercise testing. The concordance rate for the presence or absence of TWA using the two measurement methods was 84%. There was a patient-specific heart rate threshold for the detection of TWA that averaged 100 ± 14 beats/min during exercise compared with 97 ± 9 beats/min during right atrial pacing (P = NS). Beyond this threshold, there was a significant and comparable increase in level of TWA with decreasing pacing cycle length and increasing exercise heart rates.
Conclusions: The present study is the first to demonstrate that microvolt TWA can be assessed reliably and noninvasively during exercise stress. There is a patient-specific heart rate threshold beyond which TWA continues to increase with increasing heart rates. Heart rate thresbolds for the onset of TWA measured during atrial pacing and exercise stress were comparable, indicating that heart rate alone appears to be the main factor of determining the onset of TWA during submaximal exercise stress.     

Architecture of the Atrial Musculature In and Around the Triangle of Koch:

Atrial Fibers. Introduction : Recent studies suggest that atrial fibers in the approaches to the AV node form part of the dual pathways recognized electrophysiologically in patients with AV nodal reentrant tachycardia (AVNRT). Our aim was to determine, by gross dissection, the arrangement of the superficial musculature in the area of the triangle of Koch In normal hearts and in hearts with documented AVNRT. hoping to ascertain anatomic features that might contribute to the debate.
Methods and Results : We used blunt dissection to study the architecture of the superficial atrial musculature in 16 autopsied hearts from adults who died of noncardiac disease. A well-defined pattern of architecture of muscle fibers was found in the region of the triangle of Koch, showing marked variations in 7 of the 16 specimens. The relationship of these fibers to the histologically specialized AV node was confirmed by histology in three cases. Two hearts from patients with known AVNRT, treated by ablation in one, were examined further histologically. These sections showed that the site of ablation was well distant from the histologically discrete AV node.
Conclusion : The variability in the arrangement of the superficial atrial muscle fibers in the area of the triangle of Koch may be one of the factors influencing the route for impulses entering the AV node. Lesions that ablate nodal reentry are within these atrial fibers rather than the histologically specialized AV node.     

Verification of Linear Lesions Using a Noncontact Multielectrode Array Catheter versus Conventional Contact Mapping Techniques

INTRODUCTION: Creation of linear lesions is an established ablation goal. Verification of complete conduction block at the ablation line is required to determine ablation success. Conventional mapping techniques are sequential endocardial activation mapping and documentation of double potentials. Recently, a noncontact multielectrode array catheter was developed that allows instantaneous three-dimensional mapping by simultaneous reconstruction of > 3,000 electrograms. In this study, we prospectively compared the accuracy of noncontact mapping to identify discontinuities in linear lesions and to verify a conduction block with that of conventional mapping techniques. METHODS AND RESULTS: In 12 patients with atrial flutter, radiofrequency pulses were applied between the tricuspid annulus and either the inferior vena cava or the eustachian ridge. Following each application, pulse propagation at the ablation line was determined during pacing by conventional mapping techniques. The findings were compared to high-density isopotential mapping using the noncontact multielectrode array catheter. It was found that noncontact mapping reliably distinguished conduction delays from a conduction block as defined by contact mapping. In addition, noncontact mapping instantaneously identified the area where a discontinuity in the line of block was present. In these patients, complete conduction block was achieved by radiofrequency pulses guided by the noncontact mapping system. CONCLUSION: Noncontact mapping is highly accurate in distinguishing conduction delays from a complete conduction block. By providing an instantaneous high-density propagation vector at all sites along the ablation line, three-dimensional isopotential mapping is helpful in localizing discontinuities of linear lesions and, thus, may facilitate the creation of a complete conduction block.     

Age-related changes in human left and right atrial conduction

INTRODUCTION: Advancing age is an independent risk factor for atrial fibrillation (AF), which is considered to be initiated by ectopic triggers and maintained by an arrhythmogenic substrate. It is not known whether substrate changes produce this age-related increase in propensity toward AF. We addressed the hypothesis that advancing age is associated with changes in biatrial electrophysiology even in patients with no history of atrial arrhythmias. METHODS AND RESULTS: Patients with left-sided accessory pathways and requiring routine electrophysiological studies were recruited. Electroanatomic mapping was performed in the left and right atria of 23 patients (age ranging from 17 to 75 years) with structurally normal hearts and no history of AF during sinus rhythm and pacing. Unlike previous studies, a trigonometric method was used to quantify wavefront propagation velocities (WPV) precisely in the direction of propagation. Refractoriness was measured at 2 cycle lengths, at three different atrial sites. Both right (r =-0.77, P < 0.0001) and left (r =-0.79, P < 0.001) atrial WPV demonstrated strongly inverse correlation with age. Furthermore, left and right WPVs were highly correlated (r = 0.66, P < 0.01), with velocities being 6.4 +/- 2.2 cm/sec higher in the right atria (P < 0.01). Refractoriness was significantly correlated with increasing age only at the septum (r = 0.53, P < 0.01). Left atrial wavelength was inversely correlated with increasing age (r =-0.56, P = 0.03). P wave duration was associated with age (r = 0.42, P = 0.04) and left atrial size (r = 0.44, P = 0.04) but not atrial WPV. CONCLUSION: Aging human atria demonstrate progressive decline in WPV and increase in septal refractoriness. These age-related changes in biatrial electrophysiology are likely to be important factors in the age-related increase in AF prevalence.     

非接触心内膜激动标测系统指导房间隔缺损修补术后Ⅱ型心房扑动的射频消融(附一例报道)

评价非接触球囊导管标测系统 (EnSite 30 0 0 )在指导房间隔缺损 (ASD)修补术后心房扑动 (简称房扑 )的射频消融中的临床应用。 1例女性患者 ,41岁 ,ASD修补术后 2 2年开始频繁发作心动过速 ,体表心电图示Ⅱ型房扑。应用EnSite 30 0 0构建右房三维几何模型 ,标测心动过速的折返激动顺序 ,发现手术疤痕与三尖瓣环之间、下腔静脉与三尖瓣环之间为折返环路的关键峡部 ,应用导航系统指导峡部消融 ,成功阻断心动过速 ;消融后通过起搏标测判定峡部已达完全双向阻滞。随访 2 0个月 ,无心动过速复发。结论 :在ASD修补术后房扑的标测和消融中应用EnSite30 0 0系统是安全有效的 ,不仅能确定折返环路的关键峡部 ,而且能准确判断线性损伤的连续性。     

Use of Only a Regular Diagnostic His-Bundle Catheter for Both Fast and Reproducible "Para-Hisian Pacing" and Stable Right Ventricular Pacing

Pacing from the Diagnostic His-Bundle Catheter. Introduction : Para-Hisian pacing, i.e., pacing the anteroseptal right ventricle (RV) with or without direct capture of the His bundle (HB), allows the differentiation of VA conduction over the AV node from conduction over an accessory pathway. Classically, it is performed by maneuvering a separate pacing catheter around the HB catheter, which may be difficult and time-consuming.
Methods and Results : This study prospectively evaluated the use of a single standard octapolar HB catheter with 2-mm interelectrode spacing for simultaneous (para-Hisian) pacing from the distal bipole and recording from the three proximal bipoles in 148 consecutive patients. Para-Hisian pacing was successful in 146 of 148 patients, performed within a median of only 10 seconds, and easily repeated several times during the course of an electrophysiologic study. Retrograde HB activation could he recorded in 132 of 146 patients; a clearly different surface ECG configuration confirmed the presence or absence of HB capture in all other patients. Interestingly, stable RV pacing could he performed from the HB catheter for the rest of the electrophysiologic study in 138 of 142 patients in whom this was tried. RV pacing from this site also led to better interpretation of retrograde conduction, due to clear visualization of retrograde HB activation.
Conclusion : Pacing from the distal dipole of a regular diagnostic HB catheter provides a fast and reliable way to perform para-Hisian pacing. Therefore, it may be advocated as a routine diagnostic protocol during electrophysiologic procedures. Moreover, pacing from this site obviates the need for a separate RV pacing catheter in most patients.     

Periprocedural Intracardiac Echocardiography for Left Atrial Appendage Closure: A Dual-Center Experience

ObjectivesThis dual-center study sought to demonstrate the utility and safety of intracardiac echocardiography (ICE) in providing adequate imaging guidance as an alternative to transesophageal echocardiography (TEE) during Amplatzer Cardiac Plug device implantation.BackgroundOver 90% of intracardiac thrombi in atrial fibrillation originate from the left atrial appendage (LAA). Patients with contraindications to anticoagulation are potential candidates for LAA percutaneous occlusion. TEE is typically used to guide implantation.MethodsICE-guided percutaneous LAA closure was performed in 121 patients to evaluate the following tasks typically achieved by TEE: assessment of the LAA dimension for device sizing; guidance of transseptal puncture; verification of the delivery sheath position; confirmation of location and stability of the device before and after release and continuous monitoring to detect procedural complications. In 51 consecutive patients, we compared the measurements obtained by ICE and fluoroscopy to choose the size of the device.ResultsThe device was successfully implanted in 117 patients, yielding a technical success rate of 96.7%. Procedural success was achieved in 113 cases (93.4%). Four major adverse events (3 cardiac tamponades and 1 in-hospital transient ischemic attack) occurred. There was significant correlation in the measurements for device sizing assessed by angiography and ICE (r = 0.94, p < 0.0001).ConclusionsICE imaging was able to perform the tasks typically provided by TEE during implantation of the Amplatzer Cardiac Plug device for LAA occlusion. Therefore, we provide evidence that the use of ICE offered accurate measurements of LAA dimension in order to select the correct device sizes.     

Carto系统指导下左房电解剖隔离治疗心房颤动

对 3例阵发性和 2例持续性心房颤动 (简称房颤 )进行左房线性消融。采用Carto标测构建左房三维电解剖图 ,并标识出肺静脉和二尖瓣环 ,在距肺静脉口外 1～ 2cm处进行绕左右肺静脉和左房峡部的环状线性隔离消融 ,后 2例增加一条左房后壁的消融线 ,消融的终点为 :①环状隔离区内的双极电压≤ 0 .1mV ,②跨消融线相邻两点的传导时间延迟 30ms以上。结果 :整个手术时间为 2 2 9± 18min ,X线曝光时间为 2 5± 3min。消融线环绕的左房面积占整个被标测左房面积的 36 %± 3.2 % ,消融线环绕的左房区域内的电压较消融前明显降低 ,绕消融线以外的部分心房组织的电压亦降低。 3例阵发性房颤有 2例在术后 1～ 2天有房颤发作 ,1例持续性房颤于术后 1周转为持续性心房扑动 ,3周时电复律为窦性心律 ,术中和术后随访期内无并发症发生 ,5例在 5 .3± 1.85个月的随访中无有症状的房颤发作。结论 :左房线性电隔离治疗房颤是安全有效的方法。