The acute effects of biatrial pacing on atrial depolarization and repolarization

Permanent biatrial and/or multisite atrial pacing may prevent atrial fibrillation (AF), but the effects on atrial electrophysiology remain incompletely understood. Acute biatrial pacing was studied in 20 patients with and 28 without (controls) a history of atrial fibrillation and/or flutter. Twelve-lead electrocardiograms were recorded during pacing from the high right atrium (RA), from the distal coronary sinus (LA), and biatrial pacing. P wave duration was measured in each lead and the difference between maximum and minimum P duration was termed P wave dispersion. Effective refractory periods (ERPs) were measured during each pacing mode. The dispersion of P wave duration was 35 +/- 14 ms in controls and 40 +/- 29 ms in AF patients (P = 0.17). Compared to RA pacing, LA pacing shortened P duration in controls (127 +/- 18 to 107 +/- 16 ms, P < 0.05) and biatrial pacing markedly shortened P duration in controls (127 +/- 18 to 93 +/- 14 ms, P < 0.05) and AF patients (114 +/- 43 to 97 +/- 21 ms, P < 0.05). P wave dispersion was unaffected. In controls, the LA ERP was longer than the RA ERP. This phenomenon was not present in AF patients, whose LA ERP was shorter than that of controls. Biatrial pacing had no effect on atrial ERPs or the dispersion of atrial refractoriness. In conclusion, acute biatrial pacing does not affect atrial repolarization but it does cause a marked shortening of global biatrial depolarization. Distal coronary sinus pacing produces a shorter P wave than RA pacing. There is substantial dispersion in the surface P wave of the electrocardiogram, the significance of which awaits further study.     

Assessment of regional wall motion by strain Doppler during biventricular pacing in patients with conventional indications for a pacemaker

Biventricular pacing therapy is effective in patients with severe congestive heart failure. Strain Doppler imaging (SDI) is a new tool for measuring regional myocardial deformation. We evaluated regional wall motion by strain Doppler imaging in 13 patients who had conventional indications for a pacemaker (74 +/- 6 years old) and in six with NYHA Class III or IV heart failure with a biventricular pacemaker (HF-RV: during right ventricular pacing, HF-BV: during biventricular pacing). The other seven patients had normal LV function (N-RV). Wall motion was assessed by strain of the myocardium, and the interval between the Q wave of the surface ECG and the peak strain (QPSI) was measured in three septal and three lateral segments. Interventricular contraction delay was determined as the interval between the onset of the left and right ventricular outflow waves. Intraventricular contraction delay was determined as the time difference between minimum and maximum QPSI. Strain of HF-RV was significantly greater than that of N-RV (-9.6%+/- 2.5% vs -14.4%+/- 2.3%, P < 0.0001). Intraventricular contraction delay of HF-RV was significantly greater than that of N-RV (273 +/- 12 vs 151 +/- 69 ms, P = 0.0004). Strain of HF-RV was not significantly greater than that of HF-BV (-9.6% +/- 2.5% vs -10.6% +/- 2.9%). Interventricular contraction delay of HF-RV was greater than that of HF-BV (37.2 +/- 44.7 vs 16.2 +/- 47.4 ms, P < 0.0001). Intraventricular contraction delay of HF-RV was significantly greater than that of HF-BV (322 +/- 101 vs 209 +/- 88 ms, P = 0.0006). In conclusion, biventricular pacing improves both interventricular contraction delay and intraventricular contraction delay in patients with conventional indications for a pacemaker with severe congestive heart failure, and SDI is useful to predict the efficacy of biventricular pacing.     

Interatrial septum pacing decreases atrial dyssynchrony on strain rate imaging compared with right atrial appendage pacing

Background: Interatrial septum pacing (IAS‐P) decreases atrial conduction delay compared with right atrial appendage pacing (RAA‐P). We evaluate the atrial contraction with strain rate of tissue Doppler imaging (TDI) during sinus activation or with IAS‐P or RAA‐P. Methods: Fifty‐two patients with permanent pacemaker for sinus node disease were enrolled in the study. Twenty‐three subjects were with IAS‐P and 29 with RAA‐P. The time from end‐diastole to peak end‐diastolic strain rate was measured and corrected with RR interval on electrocardiogram. It was defined as the time from end‐diastole to peak end‐diastolic strain rate (TSRc), and the balance between maximum and minimum TSRc at three sites (ΔTSRc) was compared during sinus activation and with pacing rhythm in each group. Results: There were no significant differences observed in general characteristics and standard echocardiographic parameters except the duration of pacing P wave between the two groups. The duration was significantly shorter in the IAS‐P group compared with the RAA‐P group (95 ± 34 vs 138 ± 41; P = 0.001). TSRc was significantly different between sinus activation and pacing rhythm (36.3 ± 35.7 vs 61.6 ± 36.3; P = 0.003) in the RAA‐P group, whereas no significant differences were observed in the IAS‐P group (25.4 ± 12.1 vs 27.7 ± 14.7; NS). During the follow‐up (mean 2.4 ± 0.7 years), the incidence of paroxysmal atrial fibrillation (AF) conversion to permanent AF was not significantly different between the two groups. Conclusions: IAS‐P decreased the contraction delay on atrial TDI compared to RAA‐P; however, it did not contribute to the reduction of AF incidence in the present study. (PACE 2011; 34:370–376)     

Reversion and maintenance of sinus rhythm in patients with permanent atrial fibrillation by internal cardioversion followed by biatrial pacing

Patients in atrialfibrillation (AF) who fail external cardioversion are usually regarded as in permanent AF. Internal cardioversion may revert many such patients into sinus rhythm (SR) but the majority relapse rapidly into AF. We investigated whether internal cardioversion followed by biatrial pacing is an effective to restore and subsequently maintain SR in patients with permanent AF. Patients in permanent AF underwent internal cardioversion that was followed by biatrial temporary pacing for 48 hours. Those who remained in SR received a permanent biatrial pacemaker programmed to a rate responsive mode with a lower rate 90 beats/min. Primary end point of the study included maintenance in SR 3 months after internal cardioversion. Sixteen patients (14 men, 57 +/- 11 years) were cardioverted. The median duration of AF was 24 months (quartiles, Q1 = 8.5 and Q3 = 102) and mean left atrium diameter was 48 +/- 04 mm. A permanent biatrial pacemaker was implanted in 11 patients. At a mean fallow-up of 15 months (range 4 to 24), 8 patients remained in SR for more than 3 months. AF was eliminated in 5 patients, while in two a second internal cardioversion on amiodarone was required. Antiarrhythmic therapy was used in half of our population and did not predict the long-term maintenance of SR. Following internal cardioversion with continuous biatrial pacing, 50% of patients with permanent AF were maintained for prolonged periods in SR. This is a new modality of treatment of permanent AF directed to the maintenance of SR that provides a further therapeutic option in end-stage AF.     

Left atrial vein pacing: a technique of biatrial pacing for the prevention of atrial fibrillation

Biatrial pacing is a promising new therapy for drug refractory AF. This article reports two studies. First, an initial 14-patient experience with a novel technique for biatrial pacing. The authors attempted to pace from the LA vein branches of the proximal CS for LA stimulation. LA vein pacing would potentially offer the advantages of greater interatrial synchronization and possibly greater reduction in AF burden and also of lesser far-field R wave sensing and greater lead stability. Second, a postmortem series examining the number, size, and site of LA veins draining into the proximal CS is described. LA vein pacing was successful in 9 of 14 patients. LA vein electrode parameters have been stable during a median follow-up of 580 days. There were three early lead dislodgments but no other complications. In the second study, a postmortem analysis of 43 human hearts was performed. The study found that 38 (88.4%) of 43 hearts had at least one LA vein draining into the proximal 5 cm of the CS. In addition, 81.2% (33/43) had at least one vein greater than 4 Fr caliber. Thus, pacing in a greater proportion of patients might be achieved by the development and use of smaller (3, 4, and 5 Fr) electrodes. Furthermore, these smaller leads would obviously allow deeper advancement into the LA veins with the potential advantages of greater interatrial synchronization and lead stability and lesser far-field R wave sensing.     

The effect of the atrial pacing site on the total atrial activation time

The effect of dual site pacing for prevention of atrial fibrillation may be due to synchronization of right and left atrial activation. Little is known, however, about the effect of pacing from single right atrial sites on differences in interatrial conduction. Twenty-eight patients without structural heart disease were studied following radiofrequency catheter ablation of supraventricular arrhythmias. Pacing was performed using standard multipolar catheters from the presumed insertion site of Bachmann's bundle, the coronary sinus ostium, the high lateral right atrium, and the right atrial appendage (n = 8 patients). Bipolar recording was performed from the distal coronary sinus, the high and low lateral right atrium, and the posterolateral left atrium (n = 13 patients). The longest conduction time from each pacing to each recording site was considered the total atrial activation time for the respective pacing site. During high right atrial pacing, the total atrial activation time was determined by the conduction to the distal coronary sinus (118 +/- 18 ms), during coronary sinus ostium pacing by the conduction to the high right atrium (94 +/- 18 ms), and during Bachmann's bundle pacing by the conduction to the distal coronary sinus (74 +/- 18 ms). The total atrial activation time was significantly shorter during pacing from Bachmann's bundle, as compared to pacing from other right atrial sites. Thus, in normal atria, pacing from the insertion of Bachmann's bundle causes a shorter total atrial activation time and less interatrial conduction delay, as compared to pacing from other right atrial sites. These findings may have implications for alternative pacing sites for prevention of atrial fibrillation.     

Dual-site right atrial pacing increases left atrial appendage flow in patients with sick sinus syndrome and paroxysmal atrial fibrillation

BACKGROUND: Dual-site right atrial pacing has been proposed as a promising concept for prevention of paroxysmal atrial fibrillation (PAF). Effects of this pacing configuration on left atrial appendage (LAA) flow and transmitral flow may be of prognostic and hemodynamic relevance. This study aims to characterize acute changes in left atrial flow depending on dual-site right atrial pacing. METHODS: In 12 patients (66 +/- 8.8 years, 4 women) with PAF and sinus bradycardia a pacemaker with a right atrial dual-site lead configuration (right atrial lateral and coronary sinus ostium) was implanted. Flow velocities in the left pulmonary vein (LPV), LAA, and across the mitral valve were assessed by transesophageal echocardiography and compared during sinus rhythm (SR) and dual-site (DS) pacing. RESULTS: Dual-site pacing resulted in higher maximum (SR: 0.57 m/s; pacing: 0.77 m/s; P < 0.02) and mean (SR: 0.33 m/s; DS: 0.47 m/s; P < 0.01) LAA emptying flow when compared with SR. The passive transmitral flow component (maximum E-wave velocity) was lower during dual-site pacing (SR: 0.53 m/s vs DS: 0.44 m/s, P < 0.02). The E/A ratio tended to be lower during dual-site pacing (SR: 1.21 vs DS: 1.01, P = 0,10). LPV flow velocities during SR and DS pacing did not differ. CONCLUSION: DS right atrial stimulation in patients with PAF increases the LAA emptying flow velocity and shifts the transmitral flow pattern towards a lower passive component when compared with sinus rhythm. The change in LAA flow may contribute to a lower incidence of thromboembolism and merits further investigation.     

AV conduction with atrial rate adaptive pacing in the bradycardia tachycardia syndrome

AV conduction with atrial rate adaptive pacing (AAIR) during exercise was investigated in 43 patients (28 men, 15 female, mean age 68 +/- 7 years) who were paced and medicated with antiarrhythmic drugs for the bradycardia tachycardia syndrome (BTS). Patients were included if they had no second- or third-degree AV block, no complete bundle branch or bifascicular block, and a PQ interval < or = 240 ms during sinus rhythm at rest. The interval between the atrial spike and the following Q wave (SQ) was measured in the supine position at rest (R) with maximum AAI pacing rate (Fmax) achieved below the Wenckebach point (SQ-R-Fmax). Bicycle ergometry was performed using the Chronotropic Assessment Exercise Protocol, and AAI pacing rate was increased stepwise by programming load-adapted increments. Seven patients showed intrinsic rhythm during exercise. In those 36 patients who were atrially paced throughout ergometry (E), SQ was measured with 70 beats/min on the lowest CAEP stage (SQ-E-70) and with Fmax at maximum work load (SQ-E-Fmax). During exercise, no second-degree AV block was observed, but 28 of 36 patients (78%) showed a nonphysiological increase of the SQ interval, and the average SQ-E-Fmax was significantly longer than SQ-E-70 (250 +/- 31 versus 228 +/- 32 ms, P < 0.01). There was only a weak correlation between SQ-R-Fmax and SQ-E-Fmax (r = 0.35824, P < 0.05). When Fmax obtained during exercise was kept during recovery, 14 patients (39%) developed a second-degree AV block between 15 and 240 seconds after ergometry, 8 patients within 90 seconds. Patients who had exhibited a P on T wave in the ECG with Fmax at the end of exercise (11 of 36 patients) were reevaluated by Doppler echocardiography. Using the same exercise protocol and identical, load-adapted rate increments, only 3 of 11 patients showed premature mitral valve closure. It is concluded that patients paced and medicated for BTS are prone to a nonphysiological prolongation of AV conduction with AAIR pacing during and after exercise. As this risk can hardly be predicted by rapid atrial pacing at rest, the pacing system should be dual chamber in this subset of patients. This especially applies to the patients in whom mechanical AV timing is affected by the conduction delay.     

Evaluation of atrial conduction time at various sites of right atrial pacing and influence on atrioventricular delay optimization by surface electrocardiography

Cardiac function and electrical stability may be improved by programming of optimal AV delay in DDD pacing. This study tested the hypothesis if the global atrial conduction time at various pacing sites can be derived from the surface ECG to achieve an optimal electromechanical timing of the left heart. Data were obtained from 60 patients following dual chamber pacemaker implantation. Right atrial septal pacing was associated with significantly shorter atrial conduction time (P < 0.0005) and P wave duration (P < 0.005), compared to standard right atrial pacing sites at the right atrial appendage or at the right free wall. The last two pacing sites showed no significant difference. In a group of 31 patients with AV block, optimal AV delay was achieved by programming a delay of 100 ms from the end of the paced P wave to peak/nadir of the paced ventricular complex. Optimization of AV delay resulted in a relative increase of echocardiographic stroke volume (SV) (10.9 +/- 13.7%; 95% CI: 5.9-15.9%) when compared to nominal AV delay (170 ms). Optimized AV delay was highly variable (range 130-250 ms; mean 180 +/- 35 ms). The hemodynamic response was characterized by a weak significant relationship between SV increase and optimized AV delay (R2 = 0.196, R = 0.443, P = 0.047). The study validated that septal pacing is advantageous for atrial synchronization compared to conventional right atrial pacing. Tailoring the AV delay with respect to the surface ECG improved systolic function significantly and was superior to nominal AV delay settings in the majority of patients.     

Failure of coronary sinus pacing in reducing local atrial conduction delay in patients with atrial fibrillation after successful internal cardioversion

Recent studies suggested that distal coronary sinus (CS) pacing may prevent atrial fibrillation (AF) by reducing site dependent intraatrial conduction delay. The aim of this study was to investigate the effect of high right atrial (HRA) and distal CS pacing on local conduction delay in patients with AF. The study population consisted of 10 patients with persistent AF after transvenous atrial defibrillation and 10 control subjects. The local conduction delays along the anterolateral right atrium (RA), in the CS, and at the right atrial septum (RAS), and the incidence of AF in response to an atrial extrastimulus during HRA and distal CS pacing at a drive cycle length of 400, 500, and 600 ms were evaluated. In patients with AF, distal CS and HRA pacing are associated with more prominent and similar extent of conduction delay within the atria, without any significant difference in the dispersion of conduction delay and susceptibility to AF induction (70% vs 60%, P = 0.9). In normal controls, distal CS pacing reduces the conduction delay at the RAS and CS ostium and decreases the dispersion of conduction delay and the propensity for AF induction (0% vs 50%, P = 0.03) compared to HRA pacing. The pacing drive cycle length has no significant effect on conduction delay in patients with AF and normal controls (P > 0.05). Compared to normal controls, patients with AF have significantly longer conduction delay at the RAS and along the anterolateral RA during HRA and distal CS pacing. The result of this study demonstrates that the effect of HRA and distal CS pacing on the local atrial conduction delay in patients with and without AF differ significantly. These patients with AF may have more diffuse atrial anisotropy causing the changes in conduction, and pacing from distal CS in these patients dose not reduce the propensity for AF.     

组织多普勒成像技术评估慢性房颤患者左室壁运动

目的 应用组织多普勒成像技术（DTI）探讨慢性房颤患者的室壁运动特点,为临床诊治提供重要的信息,方法,将研究分为三组,A组为18例正常对照,B组为15例心房大小正常的房颤患者,C组为16例心房扩大的房颤患者,所有患者均无严重瓣膜病或节段性室壁运动异常,采用HP SONOS 5500超声显像仪和脉冲DTI,分别在心尖四腔心切面和胸骨旁长轴切面测定左室侧壁和后壁收缩期峰值速度（VS）,舒张期峰值速度（VE）,心电图QRS波起始至收缩期峰值速度的平均时间T1,心电图QRS波起始至舒张期峰值速度的平均时间T2,平均心率为R－R,结果 （1）A组正常人均有舒张早期和晚期两个波峰（E峰和A峰）,B组和C组房颤患者均只有一个舒张期波峰（E峰）,（2）A组与B组这间的DTI测值差异均无显著性意义（均为P＞0．05）,（3）C组左室侧的VS显著小于A组（P＜0．05）,C组左室后壁的VS,VE均显著大于A组（P均＜0．05）,C组侧壁的T1／（R－R）^1/2,Ts/(R-R)1/2显著高于A组（P均＜0．05）,C组后壁的T1／（R－R）^1/2,T2/(R-R)^1/2与A组比较差异无显著性意义（P均＞0．05）,结论 左房增大的房颤患者左室壁在长轴方向收缩活动减弱,舒张期峰值速度延迟,在短轴方向舒缝活动增强,DTI技术能精确地定量分析房颤患者的室壁活动,可成为评价房颤患者心肌舒缩功能的无创伤性新方法。     

Left atrial wall motion velocity measured by the velocity profile method with tissue Doppler echocardiography in normal subjects: its relation to aging

Purpose The aim of this study was to find a method for measuring left atrial wall velocity (LAWV) during atrial contraction using tissue Doppler echocardiography.Methods The velocity profile method was used to measure left atrial wall velocity at several sites in 64 healthy individuals aged 25–84 years. We attempted to find maximum left atrial wall velocity (LAWVmax) by mapping on four-chamber, two-chamber, short-axis, and long-axis views and studied the relations between maximum left atrial wall velocity, age, and peak velocity during atrial contraction in mitral or pulmonary venous flow.Results Left atrial wall velocity was varied by changing the position of the sampling volume. The velocity profile pattern was similar to the left ventricular wall velocity pattern near the mitral valve annulus in the left atrium. Left atrial wall velocity had a positive peak during atrial contraction when the sample volume was located in the cranial and dorsal area. Maximum left atrial wall velocity was obtained in 74% of cases with the two-chamber view. Maximum left atrial wall velocity in healthy subjects was 3.1 ± 0.7cm/s, and the duration of the atrial contraction was 112 ± 12ms. Maximum left atrial wall velocity increased slightly with age but was not significantly correlated with peak velocity during atrial contraction in mitral or pulmonary venous flow.Conclusions Left atrial wall velocity was measured by the velocity profile method in 64 healthy subjects aged 25–84 years. Maximum left atrial wall velocity increased slightly with age but was not significantly correlated with the peak velocity during atrial contraction in mitral or pulmonary venous flow.     

超声应变成像获得的左房机械离散度可作为新发房颤的预测指标

目的 应用超声应变成像定量评估左房机械离散度与新发房颤的关系,探讨其预测房颤在左房扩大及左房功能障碍之外的增量价值。 方法 选取2018~2021年有房颤风险的376例一般人群作为受试者行心电图检查,随访3年后选取有新发房颤的35例受试者作为研究组,在同一队列中选取与研究组相等例数且年龄性别相匹配的未出现房颤受试者作为对照组。应用超声应变成像测量两组的12节段左房应变值,获取并分析两组的左房容积指数(LAVI)、左房泵应变(LAPS)、左房储器应变(LARS)及左房机械离散度(SD-TPS)的差异性。SD-TPS定义为经R-R间期标化的左房各节段储器应变达峰时间标准差。校正患者基线资料、LAVI、LAPS、LARS,分析SD-TPS与新发房颤的独立相关性及其增量预测价值。 结果 两组LAVI的差异无统计学意义(32.5±9.2 mL/m² vs 29.5±8.3 mL/m²,P=0.16);研究组的LAPS[(16.6±4.3)% vs (20.6±4.3)%,P < 0.01]和LARS[(31.4±7.7)% vs(38.0±7.3)%,P < 0.01]低于对照组;研究组的SD-TPS高于对照组([6.3±2.3)% vs (3.9±1.6)%,P < 0.01]。调整了CHARGE-AF评分、LAVI和LARS后,SD-TPS仍与新发房颤独立相关(危险比1.26,95%CI=1.10-1.45,P < 0.01)。Cox比例风险回归模型中,SDTPS预测新发房颤可提供左房容积及左房应变之外的增量价值(P < 0.01)。 结论 从超声应变成像中获得的左房机械离散度可作为新发房颤风险分层的有效预测指标,在预测新发房颤方面可提供左房容积及左房功能障碍之外的增量价值。     

多普勒组织成像技术对原发性高血压

目的：应用多普靳组织成像技术的速度模式评价原发性高血压不同左室构型改变的局部室壁运动特点。方法：依据Ｇａｎａｕ分类法将原发性高血压患者的左室构型分为四种类型,并与正常对照组比较分析室壁基底段、中间段、心尖段运动速度（Ｖ）及左室后壁速度阶差（ＶＧ）、跨壁速度阶差（ＭＶＧ）,且与常规超声心功能指标左室短轴缩短率（ＦＳ）、左室射血分数（ＥＦ）进行比较。结果：原发性高血压各组ｓ波、ｅ波运动速度（Ｖｓ、Ｖｅ     

多普勒组织成像技术对缺血心肌再灌注前后室壁运动的定量研究

目的　利用多普勒组织成像技术 (DTI)观察正常人及冠心病患者心肌运动的特点 ,并了解缺血心肌再灌注前后心肌运动改变情况。方法　 16例健康人及 18例冠心病患者均行DTI检测 ,冠心病患者再灌注后再行DTI ,比较手术前后DTI变化情况。结果　冠心病患者和健康人相比 ,收缩期峰值速度 (VS)明显降低 (室间隔心尖段除外 ) ,舒张早期峰值速度 (VE)也明显减低 (间壁心尖段及下壁心尖段除外 )。再灌注前后比较 ,运动恢复节段VS、VE 均明显提高。结论　DTI能定量分析缺血心肌再灌注前后室壁运动变化情况。     

Alternate site atrial pacing in the young: conventional echocardiography and tissue Doppler analysis of the effects on atrial function and ventricular filling

BACKGROUND: Although the right atrial appendage (RAA) is typically used for atrial pacing lead implant, recent studies have shown benefits of alternate site atrial pacing (ASAP) in the elderly. However, comparable studies in the young are lacking. METHODS: To investigate effects of ASAP on cardiac function and atrioventricular mechanical interactions in the young, 26 subjects (ages 10 to 23 years) with normal cardiac anatomy, function, and atrioventricular node conduction underwent echocardiography during electrophysiology studies while in sinus rhythm (NSR), and with temporary pacing from high right atrium (HRA), RAA, mid septal right atrium approximating Bachmann's bundle (BB), and left atrium (LA) via the distal coronary sinus (CS). After a paced steady state of 10 minutes, left atrial total and systolic ejection fractions, color-guided mitral inflow, and annular tissue Doppler indices were obtained. Left ventricular ejection fraction and myocardial performance indexes (MPI) were calculated. RESULTS: The total and systolic LA ejection fractions were higher during the NSR compared to all ASAP. Mitral inflow velocities changed significantly with ASAP. The passive/active ventricular filling ratio (E/A) deteriorated from NSR to HRA to BB to CS. There were significant changes in late diastolic tissue Doppler velocities during ASAP compared to NSR. The MPI during ASAP differed from those during the NSR. HRA and Bachmann bundle pacing provided better MPIs than RAA or CS pacing. CONCLUSION: The location of atrial pacing leads has an acute impact on cardiac function and atrioventricular mechanical interaction. Pacing close to sinus node location may be beneficial in the young.     

组织速度成像结合应变率成像技术对房颤状态下左心耳功能的评价

目的应用应变率成像（SRI）结合组织速度（TVI）显像技术评价持续性房颤患者左心耳机械运动特点以及变化特点。方法对29例患者和31例对照者行经食管超声检查,比较各节段运动速度（PSV和PDVE）以及局部心肌沿长轴的应变率（Ssr和Dsr）变化特点。结果对照组左心耳壁顶部Ssr、Dsr、PSV和PDVE均高于其余节段（P〈0.01,0.05）。房颤组左心耳顶部Ssr、PSV仅高于间隔壁及侧壁中段（P〈0.05）,心耳顶部Dsr仅高于间隔壁中段（P〈0.05）。对照组心耳顶部Ssr、PSV与左心耳面积变化率（LAA-EF）和左心耳充盈速度（LAA-EV）呈正相关（r=0.724、0.637、0.656、0.712,P〈0.001）,房颤组心耳顶部PSV与LADd呈线性负相关（r=-0.66,P〈0.001）。房颤组各节段Ssr、Dsr、PSV以及PDVE较对照组均降低（P〈0.01）。结论左心耳顶部Ssr以及PSV决定了心耳整体的排空能力,房颤患者由于心耳壁舒缩功能明显降低导致的心耳壁运动不协调。TVI和SRI技术相结合,能更为全面地反映左心耳功能变化特点。     

Effect of right atrial overdrive pacing in the prevention of symptomatic paroxysmal atrial fibrillation: a multicenter randomized study,the PAF-PACE study

The aim of this study was to assess if right atrial overdrive pacing can suppress symptomatic episodes of paroxysmal atrial fibrillation (PAF) in patients without bradyarrhythmias. Forty-two patients with frequent and symptomatic PAF without other pacing indication had a pacemaker implanted after a 4-week run-in period, during which the frequency of symptomatic PAF episodes and the mean heart rate were objectively documented. Depending on the mean heart rate recorded during run-in, the pacemaker was programmed in random order to right atrial AAI pacing at 10-19 beats/min > mean heart rate (medium overdrive [MO]), at 20-29 beats/min > mean heart rate (high overdrive [HO]) and to no pacing (OAO mode) for 4-12 weeks each using a crossover design. In the 35 patients who completed the protocol, the number of symptomatic episodes of PAF (>30-second duration) per week was significantly lower during MO pacing (median 0.88, P = 0.001, n = 35) and during HO pacing (median 0.75, P = 0.002, n = 20) than during OAO (median 2.02 and 2.04, respectively). There was no difference between MO and HO pacing in the 20 patients paced at both rates (0.97 vs 0.75, P = 0.33). Seven patients did not complete the protocol due to persistent atrial fibrillation (n = 4), angina pectoris requiring surgery (n = 1), and unwillingness to continue the study due to improvement (n = 1) or worsening (n = 1) of symptoms during the study periods. Right atrial overdrive pacing can reduce the number of symptomatic PAF episodes in patients with frequent and drug refractory PAF but without bradyarrhythmias.     

斑点追踪成像技术对心房颤动患者左心耳功能及应变的评估

目的应用斑点追踪成像自动分析技术评估心房颤动患者左心耳功能和应变。 方法回顾性纳入2019年12月至2021年2月空军军医大学唐都医院进行经食管超声心动图检查的心房颤动患者50例,以及性别、年龄匹配的窦性心律患者34例。应用斑点追踪成像技术对左心房、左心耳进行自动容积和应变分析,获取经胸超声心动图以及经食管超声心动图45°、135°图像的相应参数。2组患者间左心房、左心耳自动容积及应变相关参数比较采用独立样本t检验,对左心房应变与左心耳应变进行Pearson线性相关分析,并对不同角度的左心耳容积及应变进行配对t检验。 结果同窦性心律组相比,心房颤动组各角度及平均左心耳容积增大,而各角度及平均左心耳排空分数减小（P均＜0.05）。应变分析显示,心房颤动组各角度及平均左心耳应变低于窦性心律组（P均＜0.05）。平均左心耳应变同左心房应变各指标均呈正相关（P均＜0.05）,其中同左心房应变储备功能、通道功能、收缩功能的相关系数分别为0.790、0.667、0.780。经食管超声心动图不同角度（45°与135°）测得的左心耳容积及排空分数差异存在统计学意义（P均＜0.05）,其中45°测得的左心耳容积较小［窦性心律组：（3.2±1.4）ml vs（5.1±2.8）ml;心房颤动组：（6.4±3.1）ml vs（12.0±6.3）ml］,而排空分数较大［（窦性心律组：（65.8±10.7）% vs（61.2±9.8）%;心房颤动组：（38.3±12.0）% vs（35.2±11.4）%］。心房颤动组两角度（45°与135°）测得的左心耳应变差异存在统计学意义［（7.9±4.1）% vs（9.2±4.5）%,P=0.045］。 结论心房颤动患者左心耳功能及应变明显降低,建议采用斑点追踪成像双平面法对心房颤动患者左心耳功能及应变进行综合评估。     

超声背向散射测定技术评价快速起搏兔右心房致心肌纤维化实验研究

目的建立快速心房起搏致兔心房颤动（房颤）模型,探讨超声背向散射测定技术评价心肌纤维化程度的价值。方法 16只新西兰大白兔随机分为假手术组和起搏组各8只。假手术组仅植入电极不行快速起搏,起搏组行短期快速起搏兔右心房12h致房颤模型。建立房颤兔模型后,2组行兔右心耳Masson染色和免疫组织化学法检测Ⅰ型和Ⅲ型胶原蛋白的表达情况;心脏超声检测2组房间隔和右心房后壁背向散射积分值和背向散射积分周期变化值。结果成功建立快速起搏右心房诱导房颤兔模型;Masson染色显示起搏组心肌纤维化明显增加;起搏组Ⅰ型及Ⅲ型胶原蛋白蛋白表达呈强阳性,假手术组呈弱阳性;起搏组房间隔和右心房后壁背向散射积分平均值（（15.56±1.30）、（16.60±2.45）dB）较假手术组（（8.24±0.85）、（7.58±0.56）dB）明显增高,背向散射积分周期变化值（（1.08±0.13）、（1.56±0.15）dB）较假手术组（（2.78±0.86）、（3.12±0.65）dB）明显降低（P〈0.05）。结论超声背向散射测定技术评价快速起搏兔右心房致房性心律失常模型心肌纤维化程度有重要价值。