Impedance cardiography: a useful and reliable tool in optimization of cardiac resynchronization devices.

AIMS: Optimizing cardiac resynchronization therapy (CRT) devices has become more complex since modification of both atrioventricular (AV) and interventricular (VV) stimulation intervals has become possible. The current paper presents data from the routine use of impedance cardiography (IC)-based cardiac output (CO) measurements to guide the optimization of AV- and VV-interval timing of CRT devices. METHODS AND RESULTS: Forty-six patients with heart failure (left ventricular ejection fraction <35%, New York Heart Association (NYHA) III-IV) and left bundle branch block (>130 ms) in sinus rhythm were evaluated 3-5 days after implantation of a CRT device by means of IC. CO was measured without pacing and with biventricular pacing using a standard protocol of VV- and AV-interval modification from -60 to +60 ms and 80 to 140 ms, respectively, in 20 ms steps. Mean CO without pacing was 3.66 +/- 0.85 L/min and significantly increased to 4.40 +/- 1.1 L/min (P<0.05) with simultaneous biventricular pacing and an AV interval of 120 ms. 'Optimizing' both VV and AV intervals further increased CO to 4.86 +/- 1.1 L/min (P<0.05). Maximum CO was measured in most patients with left ventricular pre-excitation. The proportion of 'non-responders' to CRT was reduced by 56% following AV- and VV-interval modification using IC guidance. CONCLUSION: Modification of both AV and VV intervals in patients with a CRT device significantly improves CO compared with standard simultaneous biventricular pacing and no pacing. IC is a useful non-invasive technique for guiding this modification. Marked variability of optimal AV and VV intervals between patients requires optimization of these intervals for each patient individually.     

Calculation of effective VV interval facilitates optimization of AV delay and VV interval in cardiac resynchronization therapy

BACKGROUND: In hearts with left bundle branch block (LBBB), both atrioventricular (AV) delay and interventricular (VV) interval determine left ventricular (LV) pump function in cardiac resynchronization therapy (CRT). The optimal combination of AV delay and VV interval currently is determined by extensive hemodynamic testing. OBJECTIVES: The purpose of this study was to investigate whether the effective VV interval (VV(eff)) can be used to optimize AV delay and VV interval. METHODS: In eight canine hearts with chronic LBBB, LV pacing was performed at various AV delays as well as biventricular pacing at multiple AV delays and VV intervals. LV pump function was assessed from LVdP/dt(max) and stroke volume (conductance catheter). Interventricular asynchrony was calculated from the timing difference between upslope of LV and RV pressure curves. VV(eff) was defined as the time delay between activation of the RV apex and LV lateral wall, irrespective of the source of RV activation (RV pacing or intrinsic conduction). VV(eff) was determined from pacemaker settings and surface ECGs recorded during biventricular pacing at various AV delays (positive values denote LV preexcitation). RESULTS: For all animals, the relationship between VV(eff) and LVdP/dt(max) as well as LV stroke work was parabolic. Maximal improvement in LVdP/dt(max) was similar during LV pacing, simultaneous biventricular pacing, and sequential biventricular pacing and was obtained at similar values of VV(eff). VV(eff) was strongly correlated with interventricular asynchrony (R = 0.97 +/- 0.03). Optimum LVdP/dt(max) occurred at VV(eff) ranging from -24 to 12 ms (mean -6 +/- 13 ms). For each experiment, the optimal VV(eff) was virtually equal to the value halfway between its minimum (during LV pacing at short AV delay) and maximum (during LBBB) value (R = 0.91). CONCLUSION: Use of VV(eff) facilitates determination of the best combination of AV delay and VV interval during biventricular pacing. For each individual heart, VV(eff), resulting in optimum LV pump function, can be estimated using surface ECGs recorded during biventricular pacing.     

双心室起搏心电图的额面心电轴分析

目的 分析行心脏再同步治疗（CRT）的患者在不同起搏模式下的心电图QRS波电轴的分布特点,以及与左心室导线位置、左心室逆重构的关系.比较12导联同步心电图机自动分析与手动测量的心电轴的差异.方法 入选2012年11月到2013年6月在上海复旦大学附属中山医院行CRT植入的41例患者,分别记录患者术后3个月在单纯左心室起搏,左心室提前60ms、40ms、20ms、0ms,右心室提前20ms、40ms,单纯右心室起搏的12导联同步心电图共326份,记录12导联同步心电图机自动分析得出的心电轴,同时手动测量I和aVF导联QRS波的净振幅,代入公式：心电轴=57.3＆#215;ATAN（aVF/I）,计算相应的心电轴.比较术前、术后6个月超声心动图结果[左心室收缩未期内径（LVESD）],明确有无左心室逆重构发生.左心室逆重构定义为术后6个月LVESD减小≥15％.根据手术中左前斜位、后前位X线透视片明确左心室导线位置.结果 ①随着右心室起搏成分的减少,左心室成分的增加,QRS波额面电轴逐渐由左偏转为右偏（r,=0.412,P＜0.001）,不同的VV间期之间,QRS波额面电轴的分布不全相同（Pearson x2=68.7,P＜0.001）;②左心室导线植入部位与心电轴分布之间无明显的相关性（rs=0.08,P=0.149）;③在双心室同步起搏模式下,不同QRS波电轴分布范围,左心室逆重构的发生率差异无统计学意义（P=0.115）;④12导联同步心电图机自动分析与手动测量的QRS波额面电轴一致性程度一般（ICC=0.563,95％ CI：0.483～ 0.635,F=3.58,P＜0.001）.结论 VV间期的改变可使QRS波电轴产生迁移,起搏成分从右心室主导转移为左心室主导时,QRS波额面电轴出现顺时针偏移的现象.QRS波心电轴与左心室导线位置相关性差,仅根据心电轴难以判断左心室导线的位置.单一时间点双心室同步起搏QRS波电轴对于左心室逆重构无预测价值.12导联同步心电图机自动分析出的QRS波额面电?     

Interventricular Delay Optimization: A Comparison among Three Different Echocardiographic Methods

Aim of the study: To compare three different methods for obtaining interventricular-(VV) interval optimization. Methods: A total of 30 patients undergoing cardiac resynchronization therapy (CRT) were enrolled. All the patients underwent VV-interval optimization performed with three different echocardiographic methods at seven different settings: simultaneous right (RV) and left (LV) ventricular pacing, LV stimulation only, LV preexcitation (LV+20,+40,+60 ms, respectively), RV preexcitation (RV+20 and+40 ms, respectively). Optimal VV delay was selected by: (1) measuring the aortic velocity time integral (VTI method); (2) measuring the time to maximum delay between septal and lateral longitudinal motion in the four-chamber view (velocity method); and (3) measuring the segment with maximal temporal difference of peak circumferential strain in short-axis view at papillary muscles level, (strain method). Velocity and strain methods measurements were obtained relying on two-dimensional ultrasound border tracking algorithm thus providing angle-independent measurements. Results: Immediately after CRT, VTI, maximum peak circumferential strain delay and maximum septal-to-lateral delay were significantly improved (P < 0.001). Particularly, VV-interval optimization determined a further improvement of these indices as compared to the other VV settings (P < 0.001). Furthermore, a substantial concordance was found between the optimal VV interval obtained according to the VTI method and velocity method (k = 0.68), between the optimal VV interval obtained according to the VTI method and strain method (k = 0.63); and between the optimal VV interval obtained according to the velocity method and strain method (k = 0.71). Conclusions: VV-interval optimization was shown to determine a further benefit beyond CRT. A significant concordance was present between VV programming based on different echocardiographic methods. (Echocardiography 2010;27:38-43)     

心电图在CRT治疗VV间期优化中的应用

目的比较心脏再同步治疗(CRT)VV间期的超声心动图优化方法与心电图优化方法的相关性。方法入选36例CRT植入术后大于3个月的病例,选择左室领先30ms、双室同步、右室领先30ms、60ms5种VV间期,用超声心动图VTI替代每搏输出量,并设立相应VV间期为最佳VV间期。两种心电图优化方法同时进行。第1种为QRS波时限法:描记出最窄QRS波为最佳VV间期。第2种为心室间激动延迟法:即分别在胸前导联(最好V1或V2导联)记录从起搏信号到QRS波形态最早出现变化的间期,仅左室起搏时所获得的间期记为T1,仅右室起搏时获得的间期记为T2。T2-T1代表最佳VV间期。结果超声优化的最佳VV间期左室领先为负值,左室与在后第1种心电图优化方法与VTI符合率64%(r=0.61,p<0.01);第2种心电图优化方法符合率为86%(r=0.82,p<0.001);联合上述两种心电图方法,其符合率达92%(r=0.90,p<0.0001)结论 CRT的VV间期优化中,与超声心动图优化对比,联合两种心电图方法其相关性最高。     

Effect of optimizing the VV interval on left ventricular contractility in cardiac resynchronization therapy

Simultaneous biventricular pacing improves left ventricular (LV) function in patients with heart failure and LV asynchrony. Proper timing of the interventricular pacing interval (VV interval) may further optimize LV function. We investigated the acute hemodynamic response of changing the VV interval using maximum LV dP/dt (LV dP/dt_max) as a parameter for LV function. A biventricular pacemaker was implanted in 53 patients with severely impaired LV function, New York Heart Association class III and IV heart failure, left bundle branch block, LV asynchrony, and a QRS interval >150 ms. Optimization of the atrioventricular and VV intervals was based on measurement of LV dP/dt_max by a 0.014-in sensor-tipped pressure guidewire. Measurement of LV dP/dt_max was obtained without complications in all patients. In patients in sinus rhythm with ischemic cardiomyopathy or idiopathic dilated cardiomyopathy, mean improvements by simultaneous biventricular pacing were 17% and 18%, respectively. Patients in atrial fibrillation showed an improvement of 21%. Optimizing the VV interval resulted in further absolute increases of 8%, 7%, and 3%, respectively, in dP/dt_max in the 3 groups. Maximum dP/dt was achieved with LV pacing first in 44 patients, simultaneous right and left ventricular pacing in 6 patients, and right ventricular pacing first in 3 patients. The mean optimal VV intervals were 37 ± 32 ms in the atrial fibrillation group, 28 ± 30 ms in the idiopathic dilated cardiomyopathy group, and 52 ± 31 ms in the ischemic cardiomyopathy group. Optimization of the VV interval significantly increased LV dP/dt_max compared with simultaneous biventricular pacing, and such optimization could be easily, accurately, and reliably evaluated by a 0.014-in sensor-tipped pressure guidewire.     

超声心动图引导下心脏再同步化治疗的优化调节

目的 应用超声心动图技术优化调节心脏再同步化治疗(CRT)的疗效.方法 接受CRT的慢性心力衰竭患者30例,在超声心动图引导下进行优化AV间期和VV间期.结果 30例患者CRT优化后心功能得到改善,左室充盈时间较优化前增加,二尖瓣返流减少;左室内各室壁收缩期达峰时间标准差减少,左室流出道速度时间积分上升,左室收缩末容积减少.结论 超声引导下AV间期和VV间期优化能够提高CRT临床疗效.     

Cardiac resynchronization therapy with sequential biventricular pacing: impact of echocardiography guided VV delay optimization on acute results.

BACKGROUND: Cardiac resynchronization therapy (CRT) improves left ventricular synchrony as evaluated by tissue Doppler imaging (TDI), leading to improved left ventricular performance and reverse remodeling. New CRT devices enable programming of left and right VV delay. The aim of this study was to determine whether sequential biventricular (BiV) pacing by echo-guided programming of VV delay would enhance the response to CRT. METHODS: 15 consecutive patients with severe heart failure and left bundle branch block underwent CRT by BiV device implantation. They were studied with conventional and TDI echo the day before implantation. Left ventricular ejection fraction (LVEF) was determined, and the electromechanical delay (QS), defined as the time interval from the beginning of the QRS to the S wave in pulsed TDI, was assessed in each of the four left ventricular basal segments. The dyssynchrony index was calculated as the difference between the longest and shortest electromechanical delay (QS(max-min)). The parameters were re-evaluated the day after implantation during simultaneous BiV pacing and with seven different VV delays. The optimal VV delay was determined by finding the VV interval corresponding to the maximum aortic velocity time interval (VTI). RESULTS: QS(max-min) decreased from 85.3 +/- 27.0 msec to 46.7 +/- 23.0 msec (p = 0.0002), LVEF increased from 21.7 +/- 7.3% to 30.0 +/- 7.7% (p = 0.0001) and aortic VTI increased from 12.7 +/- 3.6 cm to 15.2 +/- 4.0 cm (p < 0.0001), with simultaneous BiV pacing. The VV intervals were programmed as follows: LV pre-excitation by 10 msec in five patients, 20 msec in three, 30 msec in two, and 40 msec in three; and RV pre-excitation by 10 msec in one and by 20 msec in one. The maximal aortic VTI obtained with VV delay programming increased from 15.2 +/- 4.0 cm to 17.7 +/- 4.0 cm (p = 0.0005). During optimized sequential BiV pacing, QS(max-min) further decreased from 46.7 +/- 23.0 msec to 30.6 +/- 21.0 msec (p = 0.02) and LVEF further increased from 30.0 +/- 7.7% to 35.0 +/- 7.7% (p = 0.0003). CONCLUSIONS: Sequential BiV pacing with VV delay optimized by evaluation of aortic VTI enhanced the response to CRT with additional improvements in left ventricular synchrony and left ventricular function compared to simultaneous CRT.     

Tailored echocardiographic interventricular delay programming further optimizes left ventricular performance after cardiac resynchronization therapy.

BACKGROUND: The aim of cardiac resynchronization therapy is correction of left ventricular (LV) dyssynchrony. However, little is known about the optimal timing of LV and right ventricular (RV) stimulation. OBJECTIVES: The purpose of this study was to evaluate the acute hemodynamic effects of biventricular pacing, using a range of interventricular delays in patients with advanced heart failure. METHODS: Twenty patients with dilated ischemic (n = 12) and idiopathic (n = 8) cardiomyopathy (age 66 +/- 6 years, New York Heart Association class III-IV, LV end-diastolic diameter >55 mm, ejection fraction 22% +/- 18%, and QRS 200 +/- 32 ms) were implanted with a biventricular resynchronization device with sequential RV and LV timing (VV) capabilities. Tissue Doppler echocardiographic parameters were measured during sinus rhythm before implantation and following an optimal AV interval with both simultaneous and sequential biventricular pacing. The interventricular interval was modified by advancing the LV stimulus (LV first) or RV stimulus (RV first) up to 60 ms. For each stimulation protocol, standard echocardiographic Doppler and tissue Doppler imaging (TDI) echo were used to measure the LV outflow tract velocity-time integral, LV filling time, intraventricular delay, and interventricular delay. RESULTS: The highest velocity-time integral was found in 12 patients with LV first stimulation, 5 patients with RV first stimulation, and 3 patients with simultaneous biventricular activation. Compared with simultaneous biventricular pacing, the optimized sequential biventricular pacing significantly increased the velocity-time integral (P <.001) and LV filling time (P = .001) and decreased interventricular delay (P = .013) and intraventricular delay (P = .010). The optimal VV interval could not be predicted by any clinical nor echocardiographic parameter. At 6-month follow-up, the incidence of nonresponders was 10%. CONCLUSION: Optimal timing of the interventricular interval results in prolongation of the LV filling time, reduction of interventricular asynchrony, and an increase in stroke volume. In patients with advanced heart failure undergoing cardiac resynchronization therapy, LV hemodynamics may be further improved by optimizing LV-RV delay.     

Optimizing sequential biventricular pacing using radionuclide ventriculography

BACKGROUND: Biventricular pacemakers are usually programmed with the default setting of synchronous biventricular pacing, although the ventricles may be paced sequentially. Whether this parameter is important for optimizing resynchronization therapy is not clear. OBJECTIVES: The purpose of this study was to investigate whether sequential pacing acutely improves left ventricular ejection fraction (LVEF) and dyssynchrony and to assess the feasibility of nuclear ventriculography for device optimization. METHODS: Twenty-seven patients implanted with a biventricular pacemaker or implantable cardioverter-defibrillator for heart failure were studied. LVEF was measured using planar radionuclide ventriculography during simultaneous biventricular pacing and during sequential pacing at four different interventricular intervals ranging from LV-40 (preexciting the left ventricle by 40 ms) to LV+40 (preexciting the right ventricle). Interventricular and intraventricular dyssynchrony were analyzed by phase analysis at each setting. RESULTS: There was great heterogeneity in individual response to VV interval programming. Twenty-four of 27 patients (89%) had significant changes (both favorable and unfavorable) in LVEF at different interventricular delays, with variations of up to 10% in absolute terms. Simultaneous biventricular pacing yielded maximal LVEF in 9 of 27 patients (33%), with a relative increase in LVEF of 18 +/- 14% by optimized sequential pacing in the remaining patients. Interventricular dyssynchrony varied significantly, with least dyssynchrony at the LV-20 setting (P = .024). There were no significant differences in intraventricular dyssynchrony at the different settings. CONCLUSION: Programming VV intervals has considerable impact on LVEF. However, there is a great degree of variation between patients in response to these settings, requiring individual assessment for device optimization.     

Optimization of cardiac resynchronization guided by Doppler echocardiography: haemodynamic improvement and intraindividual variability with different pacing configurations and atrioventricular delays.

AIMS: Cardiac resynchronization therapy (CRT) improves symptoms in heart failure patients with intraventricular conduction delay (IVCD). Different pacing modalities produce variable activation patterns and are likely to result in different haemodynamic changes. The objective of this study was to demonstrate acute haemodynamic changes with different CRT configurations. METHODS AND RESULTS: In 26 patients (left ventricular ejection fraction 22.7+/-6.1%, QRS 176+/-29 ms, New York Heart Association III/IV 18/8), a CRT device was implanted. An optimization procedure was performed including left (LVPEI) and right ventricular pre-ejection intervals, interventricular mechanical delay (IVD), left ventricular filling fraction (FTc), and myocardial performance index (MPI) during left and biventricular pacing with three different atrioventricular (AV) delays. An optimal mode and AV delay were defined. LVPEI changed from 166+/-27 to 139+/-25 ms, IVD from 49+/-19 to 6+/-18 ms, MPI from 0.98+/-0.25 to 0.62+/-0.22, and FTc from 0.42+/-0.08 to 0.51+/-0.08 (P<0.001 for all comparisons). The variability was 39+/-20 ms for LVPEI, 55+/-24 ms for IVD, 0.11+/-0.07 for FTc, and 0.35+/-0.18 for MPI. CONCLUSION: Optimized resynchronization in heart failure patients with IVCD produces marked acute improvement of the altered cardiac cycle timing. The variability of Doppler parameters with different CRT modalities underlines the necessity of individualized settings and suggests that the patients' benefit may be jeopardized without optimization.     

Cardiac resynchronization therapy: variations in echo-guided optimized atrioventricular and interventricular delays during follow-up

BACKGROUND: Relatively few data are available on long-term echocardiographic optimization of atrioventricular (AV) and interventricular (VV) delay programming in cardiac resynchronization therapy (CRT). We assessed variations in optimized AV and VV delays during long-term follow-up. METHODS: Thirty-seven consecutive heart failure patients received Doppler echocardiographic optimization of AV and VV delay within 48 hours from CRT device implantation, at 6 months and at 12 months (the last for the first enrolled 14 patients). RESULTS: After implantation, median optimized AV delay was 100 ms (range, 45 ms); VV optimization led to simultaneous biventricular activation in 4 patients, left ventricular preactivation in 17 patients and right ventricular preactivation in 16 patients. At 12 months median AV delay decreased to 85 ms (23 ms) (P < 0.05 vs. baseline). With respect to previous assessment, VV delay variations > or =40 ms were observed in 41% of the patients at 6 months and in 57% of the tested patients at 12 months. A nonconcordance (by Kappa test) of optimized VV delays was found between each new assessment and the previous one. VV delay optimization was associated with significant (P < 0.001) increases in aortic velocity time integral both at baseline and during follow-up. CONCLUSIONS: Echocardiographic optimization of AV and VV delay is associated with broad intraindividual variability during follow-up. A new assessment of optimized VV delays during long-term follow-up reveals a nonconcordance with previous values and provides increases in forward stroke volume.     

Discordant Left and Right Ventricular Optimal Atrioventricular and Interventricular Delays during Biventricular Pacemaker Optimization

Echocardiography‐guided optimization of atrioventricular (AV) delay (AVD) improves left ventricular (LV) filling, and optimized interventricular delay (VVD) leads to further improvement in cardiac output in patients with biventricular (Biv) pacing. Investigators use LV filling and ejection to optimize AV and VV delay in patients with Biv pacing. Effect of such optimization on right‐sided hemodynamics remains unknown. In our experience, few patients experience worsening of right ventricle (RV) hemodynamics when LV parameters are optimized. We present a series of cases where we observed suboptimal RV filling or ejection at optimal AVD and VVD for LV. This RV‐LV discordance may contribute to nonresponder rate to cardiac resynchronization therapy (CRT) and should be evaluated in a consecutive series of CRT nonresponder patients to help improve CRT response.     

The use of impedance cardiography for optimizing the interventricular stimulation interval in cardiac resynchronization therapy—a comparison with left ventricular contractility

The present study aimed to assess whether impedance cardiography (IC) can correctly identify the optimal interventricular (VV) pacing interval in cardiac resynchronization therapy (CRT). Twenty four patients received a biventricular pacemaker and underwent IC for cardiac output (CO) measurements to identify the optimal VV interval. Invasive measurements of left ventricular (LV) dP/dt_max were used as a reference. During optimization the VV interval was changed with 20 ms steps from +80 (LV pre-excitation) to−80 ms (RV pre-excitation). The optimal VV interval was defined as the one that resulted in the highest LV dP/dt_max value and the highest CO obtained by IC, respectively. During simultaneous biventricular pacing both LV dP/dt_max and CO increased (mean 16.6% and 16.2%, respectively) as compared to baseline. Biventricular pacing with optimized VV intervals resulted in a further absolute increase of LV dP/dt _max and CO (5.6% and 41.3%, respectively). The average decrease in LV dP/dt_max was 79.6 ± 51.6 mmHg/s when the optimal VV interval was programmed according to the IC measurements. Cross spectral analysis showed no correlation between the optimal VV intervals identified by the two methods (p > 0.05) and identical optimal VV intervals were identified in only six of the 24 patients. When broader VV time intervals were compared the correlation between the two methods was statistically significant (p = 0,0166). In conclusion, the use of IC for VV interval optimization is questionable since these optimized time intervals do not seem to correlate well with those obtained by measuring LV dP/dt.     

Cardiac resynchronization therapy is certainly cardiac therapy, but how much resynchronization and how much atrioventricular delay optimization?

Cardiac resynchronization therapy has become a standard therapy for patients who are refractory to optimal medical therapy and fulfill the criteria of QRS >120?ms, ejection fraction <35% and NYHA class II, III or IV. Unless there is some other heretofore unrecognized effect of pacing, the benefits of atrio-biventricular pacing on hard outcomes observed in randomized trials can only be attributed to the physiological changes it induces such as increases in cardiac output and/or reduction in myocardial oxygen consumption leading to an improvement in cardiac function efficiency. The term "Cardiac Resynchronization Therapy" for biventricular pacing presupposes that restoration of synchrony (simultaneity of timing) between left and right ventricles and/or between walls of the left ventricle is the mechanism of benefit. But could a substantial proportion of these benefits arise not from ventricular resynchronization but from favorable shortening of AV delay ("AV optimization") which cannot be termed "resynchronization" unless the meaning of the word is stretched to cover any change in timing, thus, rendering the word almost meaningless. Here, we examine the evidence on the relative balance of resynchronization and AV delay shortening as contributors to the undoubted clinical efficacy of CRT.     

Optimierte CRT-Programmierung

Cardiac resynchronization therapy (CRT) can result in significant clinical improvement in patients with congestive heart failure. Non-response to CRT might be attributable to suboptimal programming. Follow-up has to ensure effective left ventricular (LV) stimulation at rest and also sufficient exercise-dependent atrial rates. Rate adaptive pacing is required in case of chronotropic incompetence. Specific algorithms may help to restore biventricular pacing or the enhance biventricular pacing rate when intrinsic AV conduction occurs, e.g., during intermittent atrial fibrillation. An individual adaptation of the AV interval is essential to achieve maximal benefit from resynchronization. Optimized AV interval programming synchronizes atrial and ventricular contraction, maximizing the atrial contribution to LV diastolic filling and preventing presystolic mitral regurgitation. Interventricular synchrony and LV contraction might be further harmonized by VV interval adaptation, although the impact of VV optimization on CRT outcome is still under debate. Non-invasive methods of AV and VV interval optimization by electro- and echocardiography are discussed.     

Manejo de la insuficiencia cardiaca con estimulación hisiana en bloqueo de rama derecha: reporte de caso

Cardiac resynchronization therapy has proven to be an effective therapy in patients with left bundle branch block and heart failure. Male, 47 years old, heart failure with a left ventricle ejection fraction of 17%, idiopathic heart failure. ECG with sinus rhythm, 1^st degree AV block, PR 400 ms, complete right bundle branch block, anterior hemi-fascicle of the left bundle of His, and QRS duration 200 ms. We decided to perform a selective His bundle pacing. In patients with right bundle branch block the biventricular cardiac resynchronization is not indicated due to low treatment response. His bundle pacing allows recruiting the blocked branch and restoring conduction throughout it, therefore, in the absence of necrosis the biventricular synchrony is achieved. We presented a case of His bundle pacing with recruitment of the right bundle branch, which reestablish biventricular synchrony measured by speckle tracking, and with a significant increase of the left ventricle ejection fraction from 17 to 36.6%, with an absolute increase of 19.6%.Key words: Cardiac resynchronization, Right bundle branch block, His bundle pacing, Heart failure, México     

心电图与超声心动图优化VV间期的对比研究

目的 评价心电图在心脏再同步治疗（CRT）患者VV间期优化中的作用.方法 入选30例心功能Ⅲ～Ⅳ级（NYHA分级）CRT患者（男27例,女3例）,年龄42 ～79（63.3±10.6）岁.植入1个月后,分别程控为单独右心室起搏和单独左心室起搏,记录体表心电图.左心室起搏时,记录胸前导联从起搏信号到QRS波起始部假δ波结束之间的间期（T1）;右心室起搏时,记录胸前导联从起搏信号到QRS波开始改变之间的间期（T2）.T1 -T2的值为从心室侧壁与间隔部同步除极左心室所需的时间延迟,为最佳左-右心室激动的间期（Optimal VV间期）.同时采用超声扫描测定不同VV间期时的主动脉速度时间积分（VTI）,产生最大VTI间期为最佳VV间期,对比两种方法结果.结果 超声优化最佳VV间期在左心室领先起搏-30 ms、-70 ms时分别有20例、5例;左、右心室同步起搏（0 ～5 ms）时有3例;右心室领先起搏＋30 ms时有2例.心电图优化最佳VV间期在左心室领先起搏-30 ms、-70 ms时分别有19例和5例;左、右心室同步起搏时有4例;右心室领先起搏＋30 ms时有2例.两种方法相关性良好.结论 采用心电图可计算出CRT患者最佳VV间期,与超声心动图相关性良好.     

Electrocardiographic Follow‐Up of Biventricular Pacemakers

Multisite pacing for the treatment of heart failure has added a new dimension to the electrocardiographic evaluation of device function. During left ventricular (LV) pacing from the appropriate site in the coronary venous system, a correctly positioned lead V1 registers a right bundle branch block pattern with few exceptions. During biventricular stimulation associated with right ventricular (RV) apical pacing, the QRS is often positive in lead V1. The frontal plane QRS axis is usually in the right superior quadrant and occasionally in the left superior quadrant. Barring incorrect placement of lead V1 (too high on the chest), lack of LV capture, LV lead displacement or marked latency (exit block or delay from the stimulation site), ventricular fusion with the spontaneous QRS complex, a negative QRS complex in lead V1 during biventricular pacing involving the RV apex probably reflects different activation of an heterogeneous biventricular substrate (ischemia, scar, His‐Purkinje participation in view of the varying patterns of LV activation in spontaneous left bundle branch block) and does not necessarily indicate a poor (electrical or mechanical) contribution from LV stimulation. In this situation, it is imperative to rule out the presence of coronary venous pacing via the middle cardiac vein or even unintended placement of two leads in the RV. During biventricular pacing with the RV lead in the outflow tract, the paced QRS in lead V1 is often negative and the frontal plane paced QRS axis is often directed to the right inferior quadrant (right axis deviation). In patients with sinus rhythm and a relatively short PR interval, ventricular fusion with competing native conduction during biventricular pacing may cause misinterpretation of the ECG because narrowing of the paced QRS complex simulates appropriate biventricular capture. This represents a common pitfall in device follow‐up. Elimination of ventricular fusion by shortening the AV delay, is often associated with clinical improvement. Anodal stimulation may complicate threshold testing and should not be misinterpreted as pacemaker malfunction. One must be cognizant of the various disturbances that can disrupt 1:1 atrial tracking and cause loss of ventricular resynchronization. (1) Upper rate response. The upper rate response of biventricular pacemakers differs from the traditional Wenckebach upper rate response of conventional antibradycardia pacemakers because heart failure patients generally do not have sinus bradycardia or AV junctional conduction delay. The programmed upper rate should be sufficiently fast to avoid loss of resynchronization in situations associated with sinus tachycardia. (2) Below the programmed upper rate. This may be caused by a variety of events (especially ventricular premature complexes and favored by the presence of first‐degree AV block) that alter the timing of sensed and paced events. In such cases, atrial events become trapped into the postventricular atrial refractory period at atrial rates below the programmed upper rate in the presence of spontaneous AV conduction. Algorithms are available to restore resynchronization by automatic temporary abbreviation of the postventricular atrial refractory period.