Ventricular activation during ventricular endocardial pacing: I. Electrocardiographic patterns related to the site of pacing

The QRS configuration produced by pacing at multiple left ventricular endocardial sites was evaluated in eight patients with (group 1) and six patients without (group 2) left ventricular wall motion abnormalities. Pacing was performed at a total of 122 sites, 4 to 13 sites in each patient. The QRS configuration resulting from apical pacing locations was compared with that at basal, septal to lateral and inferior to superior locations. Significant differences in QRS configuration during pacing from apical and basal locations were observed in electrocardiographic leads I, V₁, V₂ and V₆ (probability [p] < 0.01). Specifically, a QS pattern in leads I, V₂ and V₆ was more characteristic of an apical pacing location (p < 0.001), and a monophasic R wave in leads V₁ and V₂ was more characteristic of a basal pacing location (p < 0.01). Significant differences in leads V₁ and V₂ were observed when septal and lateral pacing sites were compared (p < 0.001). A monophasic R wave in leads V₁ and V₂ was more characteristic of a lateral pacing location (p < 0.01); a QS complex in lead V₂ was more characteristic of a septal pacing location (p < 0.001). Pacing at superior sites usually produced an inferior axis and vice versa (p < 0.001). The electrocardiographic patterns produced by pacing at similar sites in patients in group 1 were less consistent than those in patients in group 2. The QRS complex during ventricular pacing was wider in patients in group 1 (159 ± 30 ms) than in patients in group 2 (132 ± 18 ms) (p < 0.001).It is concluded that the QRS configuration recorded with 12 lead electrocardiography during endocardial pacing can help locate the region of the pacing site in patients with and without organic heart disease, although precise localization is not possible.     

Conventional Electrocardiogram in Arrhythmogenic Right Ventricular Dysplasia-Cardiomyopathy and Idiopathic Right Ventricular Outflow Tract Tachycardia

Objective: Arrhythmogenic right ventricular dysplasia up to now is a rare cardiomyopathic entity with certain difficulties in clinical definition of diagnostic criteria. In 42 patients with major and minor criteria of arrhythmogenic right ventricular dysplasia and 25 patients with idiopathic ventricular arrhythmia, the role of conventional ECG in the diagnosis of arrhythmogenic right ventricular dysplasia was reevaluated. Methods: In standard 12-lead ECG, QRS duration was measured in limb lead D₁, and in V₁-V₆. A ratio of the sum of right (V₂+ V₃) and left (V₄+ V₅) was calculated. T wave inversions, Epsilon wave, and mechanisms of advancing right bundle branch block were analyzed. Results: In 39 out of 42 patients (93%) with the diagnosis of arrhythmogenic right ventricular dysplasia, a ratio of right and left precordial QRS duration of >1.2, a maximum right precordial QRS duration of > 100 ms in 10 cases (26%) and >110 ms in 29 cases (74%) could be found. Incomplete right bundle branch block with right precordial T inversions was found in one case. The ECG in two patients revealed a precordial R/S transition in V₁ or V₂; in all other cases, R/S transition was localized in V₃ or V₄. R peak time was normal (< 0.04 s) in all cases, a “notching” or “slurring” of the S wave was striking in 16 cases. T wave inversions were found in 27 cases and definite Epsilon wave in only one case. Although incomplete right bundle branch block and certain preforms could also be disclosed in four patients with idiopathic right ventricular outflow tract (RVOT) tachycardia, localized right precordial QRS prolongation could be excluded in all but one of these cases. Localized right precordial QRS duration prolongation in one case was probably due to a rotation of the heart with a precordial R/S transition between V₁ and V₂. Conclusion: Localized right precordial QRS prolongation in a normal precordial R/S transition: (a) seems to be the most important aspect of arrhythmogenic right ventricular dysplasia at conventional ECG, with a sensitivity of 93% and a specificity of 96% in order to distinguish idiopathic RVOT tachycardia; (b) can appear with (64%) or without (36%) secondary T wave inversions; and (c) is due to a “parietal” block sparing the specialized conducting system.     

Preferred left ventricular lead position for upgrade from right ventricular pacing to cardiac resynchronization therapy

Introduction

Cardiac resynchronization therapy (CRT) is well-established for treating symptomatic heart failure with electrical dyssynchrony. The left ventricular (LV) lead position is recommended at LV posterolateral to lateral sites in patients with left bundle branch block; however, its preferred region remains unclear in patients being upgraded from right ventricular (RV) apical pacing to CRT. This study aimed to identify the preferred LV lead position for upgrading conventional RV apical pacing to CRT.

Methods

We used electrode catheters positioned at the RV apex and LV anterolateral and posterolateral sites via the coronary sinus (CS) branches to measure the ratio of activation time to QRS duration from the RV apex to the LV anterolateral and posterolateral sites during RV apical pacing. Simultaneous biventricular pacing was performed at the RV apex and each LV site, and the differences in QRS duration and LV dP/dt_max from those of RV apical pacing were measured.

Results

Thirty-seven patients with anterolateral and posterolateral LV CS branches were included. During RV apical pacing, the average ratio of activation time to QRS duration was higher at the LV anterolateral site than at the LV posterolateral site (0.90 ± 0.06 vs. 0.71 ± 0.11, p < .001). The decreasing ratio of QRS duration and the increasing ratio of LV dP/dt_max were higher at the LV anterolateral site than at the posterolateral site (45.7 ± 18.0% vs. 32.0 ± 17.6%, p < .001; 12.7 ± 2.9% vs. 3.7 ± 8.2%, p < .001, respectively) during biventricular pacing compared with RV apical pacing.

Conclusion

The LV anterolateral site is the preferred LV lead position in patients being upgraded from conventional RV apical pacing to CRT.     

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?     

Short-Term Hemodynamic and Electrophysiological Effects of Cardiac Resynchronization by Left Ventricular Septal Pacing

BackgroundCardiac resynchronization therapy (CRT) is usually performed by biventricular (BiV) pacing. Previously, feasibility of transvenous implantation of a lead at the left ventricular (LV) endocardial side of the interventricular septum, referred to as LV septal (LVs) pacing, was demonstrated.ObjectivesThe authors sought to compare the acute electrophysiological and hemodynamic effects of LVs with BiV and His bundle (HB) pacing in CRT patients.MethodsTemporary LVs pacing (transaortic approach) alone or in combination with right ventricular (RV) (LVs+RV), BiV, and HB pacing was performed in 27 patients undergoing CRT implantation. Electrophysiological changes were assessed using electrocardiography (QRS duration), vectorcardiography (QRS area), and multielectrode body surface mapping (standard deviation of activation times [SDAT]). Hemodynamic changes were assessed as the first derivative of LV pressure (LVdP/dtmax).ResultsAs compared with baseline, LVs pacing resulted in a larger reduction in QRS area (to 73 ± 22 μVs) and SDAT (to 26 ± 7 ms) than BiV (to 93 ± 26 μVs and 31 ± 7 ms; both p < 0.05) and LVs+RV pacing (to 108 ± 37 μVs; p < 0.05; and 29 ± 8 ms; p = 0.05). The increase in LVdP/dtmax was similar during LVs and BiV pacing (17 ± 10% vs. 17 ± 9%, respectively) and larger than during LVs+RV pacing (11 ± 9%; p < 0.05). There were no significant differences between basal, mid-, or apical LVs levels in LVdP/dtmax and SDAT. In a subgroup of 16 patients, changes in QRS area, SDAT, and LVdP/dtmax were comparable between LVs and HB pacing.ConclusionsLVs pacing provides short-term hemodynamic improvement and electrical resynchronization that is at least as good as during BiV and possibly HB pacing. These results indicate that LVs pacing may serve as a valuable alternative for CRT.     

Underestimation of duration of ventricular activation by 12-lead ECG compared with direct measurement of activation duration derived from implanted pacemaker leads

Aim

To determine extent to which 12-lead ECG QRS duration (QRSd) reflects ventricular activation duration compared with time relations from unpaced ventricular myograms in cardiac resynchronisation therapy (CRT) patients.

Methods

Left (LV) and right ventricular (RV) myograms were recorded during spontaneous rhythm from in-situ pacemaker leads in 77 patients receiving CRT; 14 ‘normal activation’ (unpaced QRSd < 120 ms), 10 ‘simple left bundle branch block’ (LBBB, QRSd 120-149 ms), 40 ‘advanced LBBB’ (QRS ≥ 150 ms) and 13 right bundle branch block. Delay in onset (Q-LV, Q-RV) and duration (dur-LV, dur-RV) of activation were measured. Interventricular delay (ΔT: Q-LV minus Q-RV) and ‘LV-overrun’ (time between end 12-lead QRS and Q-end LV myogram) were calculated.

Results

‘Normal activation’: Neither Q-LV, Q-RV (38 ± 6 ms, 39 ± 11 ms), nor dur-LV, dur-RV (66 ± 9 ms, 81 ± 25 ms) differed. ΔT (− 1 ± 11 ms) was not different from zero, nor was Q-end LV (104 ± 10 ms) different from QRSd (p = 0.09).‘Simple LBBB’: Q-LV (102 ± 28 ms) was longer than ‘normal activation’ (p < 0.001), but Q-RV, dur-LV, and dur-RV were no different. ΔT (54 ± 23 ms) was increased (p < 0.001) and Q-end LV (187 ± 48 ms) was longer than QRSd (p = 0.005).‘Advanced LBBB’: Q-LV (115 ± 52 ms) was longer than ‘normal activation’ (p < 0.001) but Q-RV was no different, so ΔT (72 ± 47 ms) was increased (p < 0.001 compared to normal, p = 0.04 compared to simple LBBB). Dur-LV (102 ± 27 ms) was also prolonged, so Q-end LV (218 ± 48 ms) was longer than QRSd (p < 0.001). Longer LV-overrun was associated with longer ΔT (p < 0.001).

Conclusions

Prolonged LV myopotential duration, associated with interventricular delay, is electrically silent on 12-lead QRSd. Unpaced surface QRSd underestimates true duration of native LV activation in CRT patients.     

Transvenous versus open chest lead placement for resynchronization therapy in patients with heart failure: comparison of ventricular electromechanical synchronicity

Background Transvenous lead placement is the standard approach for left ventricular (LV) pacing in cardiac resynchronization therapy (CRT), while the open chest access epicardial lead placement is currently the most frequently used second choice. Our study aimed to compare the ventricular electromechanical synchronicity in patients with heart failure after CRT with these two different LV pacing techniques. Methods We enrolled 33 consecutive patients with refractory heart failure secondly to dilated cardiomyopathy who were eligible for CRT in this study. Nineteen patients received transvenous (TV group) while 14 received open chest (OP group) LV lead pacing. Intra- and inter-ventricular electromechanical synchronicity was assessed by tissue Doppler imaging (TDI) before and one year after CRT procedure. Results Before CRT procedure, the mean QRS-duration, maximum time difference to systolic peak velocity among 12 left ventricle segments (LV Ts-12), standard deviation of time difference to systolic peak velocity of 12 left ventricle segments (LV Ts-SD), and inter-ventricular mechanical delay (IVMD) in OP and TV group were 166 ± 17 ms and 170 ± 21 ms, 391 ± 42 ms and 397 ± 36 ms, 144 ± 30 ms and 148 ± 22 ms, 58 ± 25 ms and 60 ± 36 ms, respectively (all P > 0.05). At one year after the CRT, the mean QRS-duration, LV Ts-12, LV Ts-SD, and IVMD in TV and OP group were 128 ± 14 ms and 141 ± 22 ms (P = 0.031), 136 ± 37 ms and 294 ± 119 ms (P = 0.023), 50 ± 22 ms and 96 ± 34 ms (P = 0.015), 27 ± 11 ms and 27 ± 26 ms (P = 0.86), respectively. The LV lead implantation procedure time was 53.4 ± 16.3 min for OP group and 136 ± 35.1 min for TV group (P = 0.016). The mean LV pacing threshold increased significantly from 1.7 ± 0.6 V/0.5 ms to 2.3 ± 1.6 V/0.5 ms (P < 0.05) in TV group while it remained stable in the OP group. Conclusions Compared to conventional endovascular approach, open chest access of LV pacing for CRT leads to better improvement of the intraventricular synchronization.     

Effects of resynchronization therapy on cardiac function in pacemaker patients "upgraded" to biventricular devices

INTRODUCTION: Cardiac resynchronization therapy (CRT) improves echocardiographic measures of cardiac function and has a variable effect on QRS duration in patients with left bundle branch block (LBBB). How CRT affects these indices in patients with right ventricular (RV) pacing-induced LBBB who are "upgraded" with left ventricular (LV) leads for CRT is unknown. We studied the echocardiographic effects of RV pacing and CRT in patients with prior continuous RV pacing after LV lead placement. METHODS AND RESULTS: Fifteen consecutive patients (age 73 +/- 11 years, LV ejection fraction 24 +/- 6%, QRS duration 190 +/- 27 msec) with New York Heart Association class IIIB-IV symptoms and continuous RV pacing underwent LV lead placement for CRT. Echocardiography and ECG were performed sequentially during RV pacing and CRT. CRT was associated with significantly reduced QRS duration (190 +/- 27 msec vs 165 +/- 18 msec, P = 0.005) and reduced LV electromechanical delay (180 +/- 33 msec vs 161+/- 43 msec). Baseline QRS duration correlated with CRT response. After CRT, patients had significant improvements in indices of systolic function, including LV ejection fraction, myocardial performance index (MPI), and LV ejection time. Abnormal baseline MPI was associated with greater improvement after CRT. LV end-diastolic and systolic volumes were similarly decreased with CRT. Mitral valve deceleration time, an index of diastolic function, was not affected by CRT. CONCLUSION: "Upgrading" RV paced patients with advanced heart failure to CRT improves measures of electrical and LV mechanical synchrony and improves systolic function.     

Cardiac resynchronization performed by LBBaP‐CRT in patients with cardiac insufficiency and left bundle branch block

ObjectiveTo evaluate the efficacy and safety of left bundle branch area pacing (LBBaP) in patients with heart failure and left bundle branch block (LBBB), and to compare the clinical effects with traditional cardiac resynchronization therapy (CRT).MethodsThirty‐two patients with dilated cardiomyopathy complicated by cardiac insufficiency and left bundle branch block were divided into CRT group and LBBaP group. Parameters including pacing threshold, R‐wave amplitude, pacing impedance and operation time, and X‐ray exposure time were recorded. The left ventricular ejection fraction (LVEF), left ventricular end‐diastolic diameter (LVEDD), and left ventricular end‐systolic diameter (LVESD) were examined by echocardiography. The changes of QRS complex before and after operation were compared.ResultsCompared with CRT group, the LBBaP group spent less time on total operation time and X‐ray exposure time and had stable electrode parameters including pacing threshold, R‐wave amplitude, and lead impedance after 12‐month follow‐up. In addition, LBBaP can achieve narrow QRS complex (117.15 ± 9.91) ms immediately than that in CRT group (130.32 ± 12.41) ms. The change of QRS between LBBaP is (50.30 ± 23.79) ms and CRT group is (33.15 ± 20.22) ms. After 6 months'' follow‐up in LBBaP group, EF was higher than that before operation. Followed up for 12 months after operation, EF and LVEDD in LBBaP group were significantly improved compared with those before operation.ConclusionLeft bundle branch area pacing is a safe and effective resynchronization method for patients with cardiac insufficiency and asynchronization, which can achieve same clinical effects to CRT.     

The Relationship of Bipolar Left Ventricular Pacing Stimulus Intensity to Cardiac Depolarization and Repolarization in Humans with Cardiac Resynchronization Devices

Background: Myocardial depolarization can be altered by varying pacing stimulus output. This may have implications on response rates for cardiac resynchronization therapy (CRT). The purpose of our study was to determine the relationship of left ventricular (LV) pacing stimulus intensity to measures of depolarization and repolarization in humans with CRT devices.
Methods: In 37 patients with a CRT device and bipolar LV leads, bipolar LV-only pacing from maximum output to threshold was performed. The presence of changes in depolarization was defined by predetermined changes in ECG morphology that accompanied a change in bipolar stimulus amplitude. ECG parameters and the EGMs were analyzed at various LV pacing stimulus intensities.
Results: Changes in ECG morphology were apparent in 70% of patients. These occurred at a mean LV stimulus amplitude of greater than 2.7 ± 0.8 V at 1 ms. Of the patients with changes in surface ECG, the transventricular conduction time decreased from 155 ± 41 ms at low output to 141 ± 39 ms at high output (P < 0.01). Despite a significant reduction in QRS duration with high output, mean QTc and JTc interval increased with increasing LV stimulus strength (539 ± 45 vs 559 ± 46 ms (P < 0.01) and 353 ± 31 ms vs 377 ± 32 (P < 0.01)).
Conclusion: Increased LV stimulus intensity, independent of RV anodal capture, is associated with faster transventricular conduction time, changes in myocardial depolarization, and longer QT intervals. These findings have important implications on the relationship of programmed LV pacing output to pacing-induced proarrhythmia and clinical CRT response rates.     

Effects of QRS duration and pacing location on pressure-volume loop evaluation of cardiac resynchronization therapy in end-stage heart failure

Cardiac resynchronization therapy (CRT) decreases the morbidity and mortality in patients with end-stage heart failure. However, patient selection remains challenging, because a considerable 30% to 50% do not respond. Controversy exists on the cutoff values for the QRS duration and the optimal lead location. The present study relates these parameters on an individual basis to acute pump function improvement using invasively obtained pressure-volume loops. Fifty-seven patients with symptomatic end-stage heart failure were included in our temporary biventricular stimulation study and were grouped according to the QRS duration (QRS <20 ms, QRS ≥120 ms but <150 ms, and QRS ≥150 ms). All patients underwent pressure-volume loop assessment of the response to biventricular pacing, comparing the baseline measurements to both right ventricular apex pacing combined with a left ventricular lead in the posterolateral and anterolateral region of the LV. Group analysis during conventional (posterolateral and right ventricular apex) CRT did not show improvement in stroke work and dP/dt(max) (-2%, p = NS; and -7%; p <0.001) in the narrow QRS group but a significant increase in the intermediate (+27%, p = 0.020, and +5%, p = 0.044) and wide (+48%, p = 0.002, and +18%, p <0.001) QRS groups. CRT using the anterolateral and right ventricular apex configuration evoked a consistently lower response compared to posterolateral and right ventricular apex, resulting in a significant hemodynamic deterioration in the narrow QRS group. However, analysis on an individual basis identified 25% of patients with narrow QRS duration showing possible hemodynamic benefit from CRT compared to 83% of patients with intermediate and wide QRS combined. In contrast, 15% of patients had deterioration by conventional (posterolateral right ventricular apex) CRT in the intermediate and wide QRS groups compared to 31% in the narrow QRS group; 19% of patients could be improved by lead placement in the anterolateral rather than the posterolateral region. In conclusion, the acute hemodynamic response to CRT is generally in line with the long-term results from large randomized trials; however, the individual variation is large. The temporary biventricular stimulation protocol might aid in individual patient selection and in research aiming at a reduction of nonresponders and improvement in lead positioning.     

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.     

When should we diagnose incomplete right bundle branch block?

An rSr' pattern with QRS duration of less than 0.12 s in theright precordial leads can be due to incomplete right bundlebranch block (which may progress to complete right bundle branchblock) or can be a normal electrophysiological variant. To identifyother ECG features that may help to distinguish between thesetwo possibilities, ECGs of 15 patients who progressed from normalto complete right bundle branch block through an intermediaterSr' pattern of incomplete right bundle branch block were analysed.The following features in the right precordial leads (V₁, V₂)that preceded or accompanied the appearance of the rSr' wereidentified: diminution of the S wave depth (100%), inversionof ratio of the S wave depth to SV₁,/SV₂ (93%), slurring ofthe downstroke or upstroke of the S wave (27%) and prolongationof the QRS duration to 0.10 s (73%). When a further 79 subjectswith rSr' pattern in the right precordial leads and QRS durationof <0.12 s were divided into those with SV₁/SV₂ ratio >1.0 and those with SV₁/SV₂ < 1.0, compared with the latterthe subjects with SV₁/SV₂ ratio > 1.0 were found to be significantlyolder (59.8±18.4 years vs 32.8±18.1 years, P<0.001),to exclusively show S wave slurring (37% vs 0%), and to morelikely have a QRS duration 0.10s (74% vs 7%). The findings indicatethat when faced with a single ECG showing an rSr' pattern inthe right precordial leads and QRS duration 0.12 s, severalother features, and in particular the relative sizes of theS waves in V₁ and V₂, may be useful in distinguishing rSr' dueto incomplete right bundle branch block from ‘normal’rSr'.     

Electrocardiographic characteristics of premature ventricular contractions in subjects with type 1 pattern of Brugada syndrome

Background

The ECG characteristics of premature ventricular contractions (PVCs) in subjects with Brugada syndrome (BrS) phenotype were investigated.

Methods and results

A total of 96 patients with type 1 ECG pattern of BrS were screened for PVCs. The study population consisted of 10 male individuals (mean age 41.9 ± 5.6 years) with spontaneous (n = 2) or drug-induced (n = 8) type 1 ECG phenotype of BrS and PVCs. Twenty patients (11 males, age 44.6 ± 15.1 years) with idiopathic right ventricular outflow tract (RVOT) PVCs (LBBB/inferior axis morphology with a negative QRS complex in lead aVL) successfully ablated from an endocardial site were also included in the study, and served as comparative controls. Six subjects with BrS phenotype (five during drug challenge) displayed PVCs with LBBB/inferior axis morphology and negative QRS complex in aVL lead which indicates an RVOT origin. The ECG characteristics of PVCs with LBBB/inferior axis in subjects with BrS and idiopathic RVOT arrhythmia were subsequently compared. QRS duration in inferior (p = 0.001) and right precordial leads (p < 0.001) was significantly longer in subjects with BrS phenotype. The RS interval in lead V2 was also significantly prolonged in individuals with BrS phenotype (p = 0.016). Subjects with BrS phenotype exhibited an increased intrinsicoid deflection time measured in right precordial leads compared to those with idiopathic RVOT PVCs (46.0 ± 7.6 vs. 27.2 ± 9.5 ms, p < 0.001). Finally, a pseudo-delta wave in precordial leads was more commonly observed in subjects with BrS ECG pattern (p = 0.029).

Conclusions

PVCs in BrS usually originate from the RVOT and display specific ECG characteristics that might be indicative of an epicardial origin. The prolonged interval criteria may be related to a localized epicardial conduction delay.     

Cardiac resynchronization therapy and AV optimization increase myocardial oxygen consumption,but increase cardiac function more than proportionally

Background

The mechanoenergetic effects of atrioventricular delay optimization during biventricular pacing (“cardiac resynchronization therapy”, CRT) are unknown.

Methods

Eleven patients with heart failure and left bundle branch block (LBBB) underwent invasive measurements of left ventricular (LV) developed pressure, aortic flow velocity-time-integral (VTI) and myocardial oxygen consumption (MVO₂) at 4 pacing states: biventricular pacing (with VV 0 ms) at AVD 40 ms (AV-40), AVD 120 ms (AV-120, a common nominal AV delay), at their pre-identified individualised haemodynamic optimum (AV-Opt); and intrinsic conduction (LBBB).

Results

AV-120, relative to LBBB, increased LV developed pressure by a mean of 11(SEM 2)%, p = 0.001, and aortic VTI by 11(SEM 3)%, p = 0.002, but also increased MVO2 by 11(SEM 5)%, p = 0.04.AV-Opt further increased LV developed pressure by a mean of 2(SEM 1)%, p = 0.035 and aortic VTI by 4(SEM 1)%, p = 0.017. MVO2 trended further up by 7(SEM 5)%, p = 0.22.Mechanoenergetics at AV-40 were no different from LBBB.The 4 states lay on a straight line for Δexternal work (ΔLV developed pressure × Δaortic VTI) against ΔMVO2, with slope 1.80, significantly > 1 (p = 0.02).

Conclusions

Biventricular pacing and atrioventricular delay optimization increased external cardiac work done but also myocardial oxygen consumption. Nevertheless, the increase in cardiac work was ~ 80% greater than the increase in oxygen consumption, signifying an improvement in cardiac mechanoenergetics. Finally, the incremental effect of optimization on external work was approximately one-third beyond that of nominal AV pacing, along the same favourable efficiency trajectory, suggesting that AV delay dominates the biventricular pacing effect — which may therefore not be mainly “resynchronization”.     

MitraClip in CRT non-responders with severe mitral regurgitation

Background

Severe mitral regurgitation (MR) ≥ 3 + and left ventricular dyssynchrony in heart failure patients are markers of CRT non response. The MitraClip (MC) implantation is a therapy for MR ≥ 3 + in patients with high surgical risk of mitral valve reconstruction.

Methods and results

We investigated 42 patients with CRT and MR ≥ 3 + who received an MC device at our center. One and two year mortality rates were compared with the predicted mortality by Seattle Heart Failure Model (SHFM) and meta-analysis global group in chronic heart failure (MAGGIC), using the baseline characteristics of patients at the time of MC implantation.The median time interval between CRT and MC implantation was 20.1 (4.5–43.3) months. In 19 patients we observed a functional regurgitation with normal leaflets and in 23 patients a degenerative mechanism for mitral regurgitation. There was no change in mean QRS duration by biventricular pacing or MC implantation. The use of MC led to significant reductions in: median N-terminal pro-brain natriuretic peptide (NT-proBNP) level (pg/ml) from 3923 to 2636 (p = 0.02), tricuspid regurgitation pressure gradient (TRPG) from 43 to 35 mm Hg (p = 0.019) and in left ventricular end-diastolic volume (LVEDV) by MC (p = 0.008). At the 2 year follow-up interval the all-cause mortality was 25%.

Conclusion

MC implantation leads to an improvement of NT-proBNP level, TRPG and LVEDV in both functional and degenerative MR but does not influence QRS duration. Two year all-cause mortality was 25% and did not differ significantly from that predicted by SHFM and MAGGIC.     

Contractile Reserve Assessed Using Dobutamine Echocardiography Predicts Left Ventricular Reverse Remodeling after Cardiac Resynchronization Therapy: Prospective Validation in Patients with Left Ventricular Dyssynchrony

Background: The presence of viable myocardium may predict response to cardiac resynchronization therapy (CRT). The aim of this study is to evaluate in patients with left ventricular (LV) dyssynchrony whether response to CRT is related to myocardial viability in the region of the pacing lead. Methods: Forty‐nine consecutive patients with advanced heart failure, LV ejection fraction < 35%, QRS duration > 120 ms and intraventricular asynchronism ≥ 50 ms were included. Dobutamine stress echocardiography was performed within the week before CRT implantation. Resting echocardiography was performed 6 months after CRT implantation. Viability in the region of LV pacing lead was defined as the presence of viability in two contiguous segments. Response to CRT was defined by evidence of reverse LV remodeling (≥15% reduction in LV end‐systolic volume). Results: Thirty‐one patients (63%) were identified as responders at follow‐up. The average of viable segments was 5.9 ± 2 in responders and 3.2 ± 3 in nonresponders (P = 0.0003). Viability in the region of the pacing lead had a sensitivity of 94%, a specificity of 67%, a positive predictive value of 83%, and a negative predictive value of 86% for the prediction of response to CRT. Conclusions: In patients with LV dyssynchrony, reverse remodeling after CRT requires viability in the region of the pacing lead. This simple method using echocardiography dobutamine for the evaluation of local viability (i.e., viability in two contiguous segments) may be useful to the clinician in choosing the best LV lead positioning. (Echocardiography 2010;27:668‐676)     

Electrocardiographic features of ventricular pacing lead in the middle cardiac vein vs. right ventricular apex in a patient with persistent left superior vena cava

A 53-year-old woman with sinus node dysfunction underwent dual-chamber pacemaker implantation through a persistent left superior vena cava draining into the coronary sinus, which was detected at the time of implantation. We managed to fix the ventricular lead in the right ventricular (RV) apex by forming a clockwise loop in the right atrium. Inadvertently, the lead was placed in the middle cardiac vein resembling RV apical position under fluoroscopic guidance. The paced QRS complex showed a pattern of tall R in V₁ through V₃, RS in V₄ through V₅, and QS in V₆.The pacing lead was carefully manipulated back into the RV apex, with the paced QRS complex showing a pattern of right bundle branch block, rR' in V₁ through V₂, and QS in V₃ through V₆. Careful attention to the surface electrocardiogram helps in distinguishing the pacing site even in those patients showing a pseudo–right bundle branch block pattern with RV apical pacing.     

Cardiac Resynchronization Therapy—Emerging Therapeutic Approaches

Cardiac resynchronization therapy (CRT) is an important therapeutic tool in the management of patients with heart failure and electrical dyssynchrony. In appropriately selected patients, landmark randomized controlled trials have demonstrated morbidity and mortality benefit beyond standard goal-directed medical therapy. Current guidelines emphasize the greatest clinical efficacy of CRT in patients with symptomatic heart failure, left bundle branch block, and wide QRS duration (>?150 ms). Other relevant considerations include the presence of atrial fibrillation, the presence of AV block, the etiology of cardiomyopathy, the presence of masked left-sided conduction delay, and the impact of comorbidities that might predict poor clinical response. At the time of CRT implantation, key considerations include targeting of the left ventricular (LV) lead to sites of greatest electrical and/or mechanical delay, the use of quadripolar versus bipolar LV pacing leads, evaluation of multiple pacing vectors to maximize electrical resynchronization, and in select instances pre-procedure imaging of the coronary venous anatomy to help guide decision-making at the time implant. Post-implant care includes the selective use of atrio-ventricular and inter-ventricular optimization algorithms, mitigation of right ventricular pacing, recognition, and treatment of suboptimal biventricular pacing, as well as management by a multi-disciplinary team of cardiovascular specialists. Emerging therapeutic strategies for patients eligible for CRT include the use of endocardial LV pacing, novel LV pacing options including multi-point pacing, His bundle pacing, and the integration of remote monitoring platforms that may identify patients at risk for clinical worsening.