Evidence of left ventricular dyssynchrony resulting from right ventricular pacing in patients with severely depressed left ventricular ejection fraction.

AIMS: Cardiac resynchronization therapy (CRT) has recently emerged as an effective treatment for patients with moderate-to-severe systolic heart failure and left bundle branch block (LBBB). Right ventricular pacing (RVP) leads to an LBBB-like pattern in the electrocardiogram. The aim of this study was to evaluate the frequency of ventricular mechanical dyssynchrony in patients induced by RVP. METHODS AND RESULTS: The study included 33 patients with a conventional single or dual chamber pacemaker, 18 with ejection fraction (EF) > 35% and 15 with EF < or = 35%. In all patients, an intrinsic rhythm without intraventricular conduction delay (QRS < or = 120 ms) was present without RVP. Two-dimensional and Doppler echocardiographic criteria for mechanical dyssynchrony [aortic pre-ejection delay (APE), interventricular mechanical delay (IVMD), delayed activation of the posterior left ventricular wall (PD), septal-to-posterior wall motion delay (SPWMD)] were evaluated in all patients with and without RVP. QRS duration showed no difference between the two EF-groups without RVP (93 +/- 10 vs. 96 +/- 9 ms), but was significantly longer in patients with low EF with RVP (152 +/- 18 vs. 181 +/- 18 ms; P < 0.001). In patients with EF > 35%, only APE was slightly prolonged by RVP (111 +/- 20 vs. 129 +/- 17 ms; P = 0.03), whereas in patients with EF < or = 35% marked pathological differences in APE (118 +/- 29 vs. 169 +/- 24 ms; P < 0.001), IVMD (22 +/- 17 vs. 58 +/- 14 ms; P < 0.001), SPWMD (103 +/- 28 vs. 125 +/- 29 ms; P = 0.004), and PD (-21 +/- 25 vs. - 39 +/- 25 ms; P = 0.005) were found. A significant correlation between QRS duration and mechanical ventricular dyssynchrony was only found for two echocardiographic parameters (IVMD, APE) with RVP. CONCLUSION: In patients with a conventional pacemaker, mechanical dyssynchrony with RVP was shown exceptionally in patients with preserved or moderately depressed systolic left ventricular (LV) function, but in nearly all patients with severely depressed systolic LV function. These patients might benefit from CRT when frequent RVP is required.     

Echocardiographic evaluation of patients with severe heart failure and impairment of intraventricular conduction following cardiac resynchronisation therapy

BACKGROUND: Echocardiographic examination is essential for clinical assessment of patients after cardiac resynchronisation therapy (CRT). AIM: To assess the benefit of CRT in patients with end-stage heart failure at long-term follow-up. METHODS: 28 patients with end-stage heart failure, NYHA class >or= III (>or= II in patients with indications for implantable cardioverter defibrillator and echocardiographic signs of ventricular mechanical systolic dyssynchrony), left ventricular ejection fraction (LVEF) <35%, QRS duration >120 ms and left bundle branch block morphology received a biventricular device. Standard colour Doppler echocardiography examination was performed at baseline, and then every 6 months, up to 2 years. Parameters of systolic and diastolic LV function, mitral insufficiency and right ventricular (RV) pressure were evaluated. RESULTS: Following CRT, a statistically significant improvement of LV dimensions (p<0.05), and LVEF (p<0.001) was recorded. CRT also resulted in a mitral regurgitation decrement (p<0.01). Interventricular mechanical delay was shortened (p=0.0005). After 2 years, non-significant worsening of LV dimensions was observed. At long-term follow-up CRT did not result in LV volume, left atrium, RV dimension or RV pressure reduction. CONCLUSIONS:CRT is associated with reverse remodelling of the LV at mid-term follow-up.     

心力衰竭患者QRS波间期与心脏机械收缩功能失同步化的相关性研究

目的评价充血性心力衰竭(CHF)患者QRS间期与左右心室间、左心室内不同步运动参数的相关关系。方法 81例CHF患者及26名健康体检者作为对照组纳入本研究。行常规及彩色组织多普勒显像(TDI)检查。以左、右心室问收缩延迟(IVMD)>33ms定义室间不同步运动,以二尖瓣环6位点中任意2点QRS波起始至心室收缩顶峰的间期(TsP)最长延迟>121ms,或6位点TsP的标准差(TsP-SD)>47ms定义左心室内收缩不同步。比较QRS≥120 ms与QRS<120ms的CHF患者室间、室内不同步发生率,分析QRS间期与室间、室内不同步参数的相关关系。结果 CHF患者IVMD较对照组明显延长[(25.7±16.3)ms比(12.8±8.8)ms,P<0.0001],IVMD与QRS间期呈明显正相关(r=0.44,P<0.0001)。CHF伴QRS≥120ms(n=31)者室间不同步发生率明显高于CHF伴QRS<120ms者(n=50)(66.7%比20.9%,P<0.05)。CHF患者TsP最长延迟及TsP-SD较对照组明显延长,TsP最长延迟及TsP-SD与QRS间期呈弱相关。结论 CHF患者室间不同步运动发生率明显高于对照组,ORS间期增宽与室间不同步的关系可能更密切。     

Frequency of inter- and intraventricular dyssynchrony in patients with heart failure according to QRS width.

AIMS: Cardiac resynchronization therapy (CRT) is an effective treatment for heart failure patients with prolongation of QRS duration. Despite careful patient selection, some do not respond to CRT based on QRS complex duration. We sought to evaluate the presence of left ventricular dyssynchrony using tissue Doppler imaging (TDI) according to QRS duration in heart failure patients. METHODS AND RESULTS: Ninety-nine patients (mean age 52.6 +/- 15.3 years) with severe heart failure [left ventricular (LV) ejection fraction, <35%] were prospectively evaluated. On the basis of QRS width, the patients were divided into two groups. Forty-eight patients (48.5%) had a normal QRS duration (<120 ms), Group I, and 51 (51.5%) had a prolonged QRS duration, Group II. All patients underwent echocardiography coupled with TDI. Spectral displays of six basal and six middle LV segments with pulsed-wave TDI were obtained to assess the time to peak systolic point from R-wave on electrocardiogram (Ts). The standard deviation of Ts (Ts-SD) and the maximal temporal difference of Ts (Ts-diff) were measured. Interventricular dyssynchrony [defined as the presence of an interventricular mechanical delay (IVMD) >40 ms] and intra-LV mechanical delays (defined as Ts-SD >33.4 ms and Ts-diff >100 ms) were correlated with the QRS width and morphology. We found a greater IVMD in Group II patients, compared with patients in Group I (42.5 +/- 22.3 vs. 26.8 +/- 21, respectively, P < 0.001). Intraventricular dyssynchrony defined as Ts-SD > or =33.4 ms was found in 45.1% of patients in Group II compared with 23% of patients in Group I (P = 0.03). Similarly, the Ts-diff was prolonged in Group II patients compared with Group I (P = 0.02). By linear regression analysis, a weak relation was found between Ts-SD and QRS duration (P = 0.055). A substantial portion of patients with prolonged QRS did not exhibit ventricular dyssynchrony defined either as total asynchrony index > or =33.4 ms or as IVMD >40 ms. CONCLUSION: A substantial proportion of patients with prolonged QRS (32.1%) did not exhibit inter- or intraventricular dyssynchrony, which may represent a limitation in identifying the ideal QRS interval for the selection of patients for 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.     

Provocation of masked left ventricular mechanical dyssynchrony by treadmill exercise in patients with systolic heart failure and narrow QRS complex

Tissue Doppler imaging-derived intra-left ventricular (LV) contractile dyssynchrony is an evolving prognostic parameter for patients with systolic heart failure (HF). However, whether and how exercise could abolish the synchronicity in HF patients with narrow QRS remains less studied. We evaluated a total of 33 HF patients with impaired LV ejection fraction (<50%), QRS duration < or =120 ms, and baseline dyssynchrony index (DI; standard deviation of electromechanical delay of 12 LV segments by tissue Doppler imaging) <33 ms. After a 6-minute treadmill exercise by modified Bruce protocol, the absolute time difference from QRS onset to peak systolic myocardial velocity of each segment was recorded immediately. With similar DI at rest and peak heart rates during exercise, 11 patients (33%) developed dyssynchrony (DI > or =33 ms) after exercise, and the others did not (44.7 +/- 8.0 vs 16.2 +/- 8.3 ms, p <0.001). Patients with dyssynchrony after exercise had greater baseline mitral early diastolic velocity/annular early diastolic velocity (E/Ea) (19 +/- 17 vs 10 +/- 5, p <0.026). Multivariate analysis revealed mitral E/Ea >10 at rest, indicating higher LV filling pressure, independently predicted the exercise-evoked dyssynchrony (odds ratio 18, 95% confidence interval 2 to 163, p <0.012). In conclusion, exercise uncovered masked LV dyssynchrony in 1/3 of systolic HF patients with narrow QRS, and exercise-provoked dyssynchrony could be predicted by mitral E/Ea >10 at rest.     

Usefulness of echo-guided cardiac resynchronization pacing in patients undergoing "ablate and pace" therapy for permanent atrial fibrillation and effects of heart rate regularization and left ventricular resynchronization

An acute comparative study of right ventricular (RV) pacing and echocardiographically guided cardiac resynchronization pacing (CRP) was performed in patients who underwent "ablate and pace" therapy for permanent atrial fibrillation. It was hypothesized that optimized CRP guided by tissue Doppler echocardiography would exert an additive beneficial hemodynamic effect to that of rate regularization achieved through atrioventricular junction ablation. An acute intrapatient comparison of echocardiographic parameters was performed between baseline preablation values and RV pacing and CRP (performed <24 hours after ablation) in 50 patients. Optimized CRP configuration was defined as the modality of pacing corresponding to that of the shortest intra-left ventricular (LV) delay among simultaneous biventricular pacing, sequential biventricular pacing, and single-chamber pacing. The intra-LV delay was defined as the difference between the longest and the shortest activation time in the six basal segments of the left ventricle. Compared with preablation measures, the ejection fraction increased by 10.8% during RV pacing (19% in patients with intra-LV delays <47.5 ms and 3% in those with intra-LV delays >47.5 ms). Compared with RV pacing, CRP caused a 9.2% increase in the ejection fraction, a 6.8% decrease in LV systolic diameter, and a 17.3% decrease in mitral regurgitation area; LV dyssynchrony was reduced from 52 +/- 27 to 21 +/- 12 ms. Similar results were observed in patients with and without depressed systolic function and in patients with and without left bundle branch block. In conclusion, rate regularization achieved through atrioventricular junction ablation and RV pacing provides a favorable hemodynamic effect that is inversely related to the level of LV dyssynchrony. Minimizing LV dyssynchrony by means of optimized CRP yields an additional important benefit.     

Predictors and treatment response with cardiac resynchronization therapy in patients with heart failure characterized by dyssynchrony: a pre-defined analysis from the CARE-HF trial.

AIMS: The cardiac resynchronization therapy in heart failure trial (CARE-HF) demonstrated that cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with heart failure and cardiac dyssynchrony. The aim of this study was to develop a prognostic model to evaluate the relationship between prospectively defined patient characteristics and treatment on the trial primary outcome of death from any cause or unplanned hospitalization for a major cardiovascular event. METHODS AND RESULTS: A total of 813 patients were enrolled in the CARE-HF study and were followed for a mean of 29.4 months. A Cox Proportional Hazards Model was fitted to identify predictors of the primary outcome and any predictors that modified the effect of CRT. Ischaemic aetiology, more severe mitral regurgitation and increased N-terminal pro-brain natriuretic peptide, were associated with an increased risk of death or unplanned cardiovascular hospitalization irrespective of cardiac resynchronization [Hazard ratio (HR) 1.89, 95% CI 1.45-2.46, HR 1.71, 95% CI 1.38-2.12 and HR 1.31, 95% CI 1.17-1.47, respectively] and increasing systolic blood pressure with a decreasing risk of an event (HR 0.99, 95% CI 0.98-1.00). The benefits of cardiac resynchronization were modified by systolic blood pressure and interventricular mechanical delay (IVMD). Patients with increasing systolic blood pressure appear to receive reduced benefit from CRT (HR 1.02, 95% CI 1.00-1.03), whereas those patients with more severe IVMD appear to benefit more from treatment (HR 0.99, 95% CI 0.98-1.00). CONCLUSION: Patients with echocardiographic evidence of more severe cardiac dyssynchrony and low systolic blood pressure obtain greater benefit from CRT, although benefits were substantial across the range of subjects included in the trial.     

Echocardiographic assessment during exercise of heart failure patients with cardiac resynchronization therapy

This prospective echocardiographic study investigated the respective impacts of left ventricular (LV) pacing and simultaneous and sequential biventricular pacing (BVP) on ventricular dyssynchrony during exercise in 23 patients with compensated heart failure and ventricular conduction delays. During exercise, LV pacing and BVP significantly (p <0.05) improved mitral regurgitation and LV dyssynchrony compared with spontaneous activation. LV segmental electromechanical delays were significantly prolonged during LV pacing, leading to increased systolic time (p <0.05), decreased LV filling time (p <0.05), and decreased stroke volume (p <0.05) compared with BVP. After optimization of the interventricular delay with sequential BVP, additional benefit was obtained during exercise in terms of stroke volume and mitral regurgitation (p <0.05). The optimal interventricular delay was different at rest and during exercise in 57% of the patients. Changes from at rest to exercise in LV dyssynchrony were correlated with changes in stroke volume (r = -0.61, p <0.01) and changes in mitral regurgitation (r = 0.60, p <0.01).     

Significance of electrocardiographic right bundle branch block in trained athletes

We sought to determine the clinical and physiologic significance of electrocardiographic complete right bundle branch block (CRBBB) and incomplete right bundle branch block (IRBBB) in trained athletes. The 12-lead electrocardiographic and echocardiographic data from 510 competitive athletes were analyzed. Compared to the 51 age-, sport type-, and gender-matched athletes with normal 12-lead electrocardiographic QRS complex duration, the 44 athletes with IRBBB (9%) and 13 with CRBBB (3%) had larger right ventricular (RV) dimensions, as measured by the basal RV end-diastolic diameter (CRBBB 43 ± 3 mm, IRBBB 38 ± 6 mm, normal QRS complex 35 ± 4 mm, p <0.001) and RV end-diastolic area (CRBBB 33 ± 5, IRBBB 27 ± 7, and normal QRS complex 23 ± 3 cm(2); p <0.001). Athletes with CRBBB also had a relative reduction in the RV systolic function at rest as assessed by the RV fractional area change and peak systolic tissue velocity. Finally, QRS prolongation was associated with parallel increases in interventricular dyssynchrony (basal RV to basal lateral left ventricular peak systolic tissue velocity time difference: CRBBB 112 ± 15, IRBBB 73 ± 33, normal QRS complex 43 ± 39 ms, p <0.001). Despite these findings, no athlete with CRBBB or IRBBB was found to have pathologic structural cardiac disease. In conclusion, among trained athletes, CRBBB and IRBBB appear to be markers of a structural and physiological cardiac remodeling triad characterized by RV dilation, a relative reduction in the RV systolic function at rest, and interventricular dyssynchrony.     

Myocardial asynchronism is a determinant of changes in functional mitral regurgitation severity during dynamic exercise in patients with chronic heart failure due to severe left ventricular systolic dysfunction.

AIMS: Functional mitral regurgitation (MR) and myocardial asynchronism occur commonly in patients with dilated cardiomyopathy and affect adversely their prognosis and symptoms. The aim of this study was to evaluate the mechanisms of changes in MR severity during dynamic exercise in patients with chronic heart failure (CHF). METHODS AND RESULTS: Seventy patients with CHF due to left ventricular (LV) systolic dysfunction [LV ejection fraction (EF) <40%] and functional MR were studied. All were in sinus rhythm. Medications were left unchanged for the study. Each patient performed a maximal symptom-limited exercise test with continuous 2D-Doppler echocardiography. Mitral regurgitant volume (RV) and effective regurgitant orifice (ERO) were determined at rest and during exercise. LV asynchrony using Doppler tissue imaging and interventricular asynchrony using conventional pulsed-Doppler were evaluated at rest. Resting LV EF averaged 25+/-8%. Mean resting LV and interventricular mechanical delays were 56+/-50 and 43+/-37 ms, respectively. The overall median values for mitral ERO and RV did not significantly change during dynamic exercise (11 [7-16] vs. 11 [6-21] mm2 and 14 [10-22] vs. 12 [9-23] mL, respectively). However, changes in mitral ERO and RV were individually variable and significantly correlated with the degree of LV asynchronism (r=0.66, P<0.0001 and r=0.66, P<0.0001, respectively). CONCLUSION: Changes in MR are variable during dynamic exercise. LV asynchronism at rest substantially contributes to worsening of functional MR during dynamic exercise in patients with CHF due to LV systolic dysfunction.     

Tricuspid Annular Plane Systolic Excursion Evaluation Improves Selection of Cardiac Resynchronization Therapy Patients

Background

The beneficial effects of cardiac resynchronization therapy (CRT) on left ventricular (LV) remodeling have been extensively described. Few data are available about the effects of CRT on right ventricular (RV) function and remodeling.

Hypothesis

We hypothesized that CRT could also induce reverse remodeling in the right ventricle and that RV baseline functional status expressed as tricuspidal annular plane systolic excursion (TAPSE) could affect CRT response.

Methods

Echocardiographic investigation was performed before and 6 months after CRT. In 192 patients, TAPSE, LV, and RV dimensions with functional parameters and LV dyssynchrony index were evaluated.

Results

At 6 months' follow‐up, 86 patients (45%) were responders to CRT according to at least 15% LV end‐systolic volume reduction. Among baseline echocardiographic parameters, responders had significantly lower TAPSE, larger LV volumes, and higher LV dyssynchrony index. In responders, LV volume reduction, ejection fraction increase, and mitral regurgitation improvement were associated with RV dimensions reduction, increased TAPSE, and improved LV dyssynchrony. Receiver operating characteristic curve analysis showed that TAPSE, at 17 mm optimal cutoff, yielded 64% sensitivity and 60% specificity in predicting CRT response; similarly, LV dyssynchrony index, at 41.25 ms optimal cutoff, predicted CRT response with 60% sensitivity and 62% specificity. A subgroup analysis demonstrated that the coexistence of high TAPSE and high dyssynchrony index values increased probability of CRT response.

Conclusions

Our results show that CRT induces RV and LV reverse remodeling and that CRT patient selection can be improved by simply measuring TAPSE value. Copyright © 2010 Wiley Periodicals, Inc. The authors have no funding, financial relationships, or conflicts of interest to disclose.     

Left ventricular versus biventricular pacing: a randomized comparative study evaluating mid-term electromechanical and clinical effects

BACKGROUND: Although left ventricular (LV) pacing has been proposed as an alternative to biventricular (BIV) pacing for heart failure (HF) patients, few comparative data are available on the electromechanical effects of these pacing modalities at mid-term follow-up. AIM: To investigate the clinical and echocardiographic effects of LV versus BIV pacing in a mid-term randomized study. METHODS: After implantation of a device with LV/BIV pacing capabilities, 22 patients with chronic HF and left bundle branch block were randomized to LV or BIV pacing. Patients were assessed both preimplantation and after 3 months by clinical examination, ECG and echocardiography with pulsed tissue Doppler imaging. RESULTS: At 3 months LV pacing improved clinical parameters, LV ejection fraction (+5%, range 5-8%, P = 0.007) and intraventricular dyssynchrony (-40 ms, range -50 to -15 ms, in septal to lateral delay, P = 0.008) to a similar extent to BIV pacing. A decrease in interventricular mechanical delay (-25 ms, range -40 to -5 ms, P = 0.008) and QRS duration (-28 ms, range -40 to -5 ms, P = 0.008) was observed in BIV, but not in LV patients. CONCLUSION: In this pilot evaluation, LV pacing appeared to be associated with clinical benefits similar to BIV pacing at mid-term follow-up, and this was combined with an improvement in intraventricular dyssynchrony, regardless of variations in interventricular dyssynchrony and QRS duration. Echocardiographic evaluation of intraventricular dyssynchrony seems to be an appropriate method for assessing the chronic response to LV pacing.     

Usefulness of right ventricular tissue Doppler imaging to predict outcome in left ventricular heart failure independent of left ventricular diastolic function

It is unknown whether right ventricular (RV) tissue Doppler (TD) predicts outcome in patients with left ventricular (LV) heart failure (HF) independently of contemporary echocardiographic Doppler variables of LV diastolic function. Comprehensive echocardiographic Doppler examination was performed before discharge in 107 patients hospitalized with LV HF. The primary end point was cardiac death or rehospitalization for HF. Follow-up was complete for 100 of 107 patients a mean of 527 days after hospital discharge. There were no significant differences in baseline clinical variables (mean age 58+/-12 years, 46% women, 77% hypertensive, 48% diabetic, 41% current smokers, and 23% known coronary artery disease) in prediction of the primary end point. Compared with patients without an event, patients with an event had a larger left atrial volume index (42+/-16 vs 33+/-13 ml/m2, p=0.001), lower LV ejection fraction (35+/-19% vs 46+/-22%, p=0.01), higher mitral peak early diastolic flow velocity/TD early diastolic velocity (19+/-7 vs 14+/-7, p=0.001), lower RV fractional area change (39+/-11% vs 43+/-10%, p=0.04), and lower RV TD systolic velocity (8+/-2 vs 10+/-3 cm/s, p=0.005). On Cox proportional hazards multivariate analysis, left atrial volume index (p=0.01), mitral peak early diastolic flow velocity/TD early diastolic velocity (p=0.03), and RV TD systolic velocity (p=0.04) were independent predictors of outcome. Even when contemporary echocardiographic Doppler measures of LV diastolic function are considered, RV TD systolic velocity is an independent predictor of cardiac death or rehospitalization for HF in patients hospitalized with HF and appears to be superior to conventional 2-dimensional parameters of RV function.     

心电图QRS间期与慢性心力衰竭左心室同步性关系的超声评价

目的评价心电图QRS间期与慢性心力衰竭（心衰）左心室同步性的关系。方法对54例慢性心衰患者（宽QRS组28例，正常QRS组26例）和15例健康人（对照组）进行心肌组织多普勒成像研究，测量收缩期和舒张早期12节段达峰时间（Ts和Te），评价不同QRS间期的慢性心衰左心室各节段不同步状况以及左心室不同步的主要影响因素。结果慢性心衰舒张末期和收缩末期容积增大，宽QRS组较正常QRS组更加显著，12节段平均Ts显著增大。以Ts≥182ms作为分界值，正常QRS组46％、宽QRS组71％存在收缩期不同步。宽QRS组Te最大差值（Te-diff）最大，以Te-diff≥79ms作为分界值，正常QRS组58％、宽QRS组89％存在舒张期不同步。同时存在收缩期和舒张期不同步者，正常QRS组为31％，宽QRS组为64％。收缩末期容积与左心室收缩期不同步相关，舒张末期容积与舒张期不同步相关。结论心电图QRS间期不能完全反映慢性心衰左心室同步性状况，左心室收缩末期容积和舒张末期容积直接影响左心室的收缩期和舒张期同步性。     

Significance of QRS complex duration in patients with heart failure.

Prolongation of QRS (> or =120 ms) occurs in 14% to 47% of heart failure (HF) patients. Left bundle branch block is far more common than right bundle branch block. Left-sided intraventricular conduction delay is associated with more advanced myocardial disease, worse left ventricular (LV) function, poorer prognosis, and a higher all-cause mortality rate compared with narrow QRS complex. It also predisposes heart failure patients to an increased risk of ventricular tachyarrhythmias, but the incidence of cardiac or sudden death remains unclear because of limited observations. A progressive increase in QRS duration worsens the prognosis. No electrocardiographic measure is specific enough to provide subgroup risk categorization for excluding or selecting HF patients for prophylactic implantable cardioverter-defibrillator (ICD) therapy. In ICD patients with HF, a wide underlying QRS complex more than doubles the cardiac mortality compared with a narrow QRS complex. There is a high incidence of an elevated defibrillation threshold at the time of ICD implantation in patients with QRS > or =200 ms. Mechanical LV dyssynchrony potentially treatable by ventricular resynchronization occurs in about 70% of HF patients with left-sided intraventricular conduction delay, a fact that would explain the lack of therapeutic response in about 30% of patients subjected to ventricular resynchronization according to standard criteria relying on QRS duration. The duration of the basal QRS complex does not reliably predict the clinical response to ventricular resynchronization, and QRS narrowing after cardiac resynchronization therapy does not correlate with hemodynamic and clinical improvement. Mechanical LV dyssynchrony is best shown by evolving echocardiographic techniques (predominantly tissue Doppler imaging) currently in the process of standardization.     

Significance of QRS complex duration in patients with heart failure

Prolongation of QRS (> or =120 ms) occurs in 14% to 47% of heart failure (HF) patients. Left bundle branch block is far more common than right bundle branch block. Left-sided intraventricular conduction delay is associated with more advanced myocardial disease, worse left ventricular (LV) function, poorer prognosis, and a higher all-cause mortality rate compared with narrow QRS complex. It also predisposes heart failure patients to an increased risk of ventricular tachyarrhythmias, but the incidence of cardiac or sudden death remains unclear because of limited observations. A progressive increase in QRS duration worsens the prognosis. No electrocardiographic measure is specific enough to provide subgroup risk categorization for excluding or selecting HF patients for prophylactic implantable cardioverter-defibrillator (ICD) therapy. In ICD patients with HF, a wide underlying QRS complex more than doubles the cardiac mortality compared with a narrow QRS complex. There is a high incidence of an elevated defibrillation threshold at the time of ICD implantation in patients with QRS > or =200 ms. Mechanical LV dyssynchrony potentially treatable by ventricular resynchronization occurs in about 70% of HF patients with left-sided intraventricular conduction delay, a fact that would explain the lack of therapeutic response in about 30% of patients subjected to ventricular resynchronization according to standard criteria relying on QRS duration. The duration of the basal QRS complex does not reliably predict the clinical response to ventricular resynchronization, and QRS narrowing after cardiac resynchronization therapy does not correlate with hemodynamic and clinical improvement. Mechanical LV dyssynchrony is best shown by evolving echocardiographic techniques (predominantly tissue Doppler imaging) currently in the process of standardization.     

Mechanical Dyssynchrony is Similar in Different Patterns of Left Bundle-Branch Block

Background

Left bundle-branch block (LBBB) and the presence of systolic dysfunction are the major indications for cardiac resynchronization therapy (CRT). Mechanical ventricular dyssynchrony on echocardiography can help identify patients responsive to CRT. Left bundle-branch block can have different morphologic patterns.

Objective

To compare the prevalence of mechanical dyssynchrony in different patterns of LBBB in patients with left systolic dysfunction.

Methods

This study assessed 48 patients with ejection fraction (EF) < 40% and LBBB consecutively referred for dyssynchrony analysis. Conventional echocardiography and mechanical dyssynchrony analysis were performed, interventricular and intraventricular, with ten known methods, using M mode, Doppler and tissue Doppler imaging, isolated or combined. The LBBB morphology was categorized according to left electrical axis deviation in the frontal plane and QRS duration > 150 ms.

Results

The patients'' mean age was 60 ± 11 years, 24 were males, and mean EF was 29% ± 7%. Thirty-two had QRS > 150 ms, and 22, an electrical axis between −30° and +90°. Interventricular dyssynchrony was identified in 73% of the patients, while intraventricular dyssynchrony, in 37%-98%. Patients with QRS > 150 ms had larger left atrium and ventricle, and lower EF (p < 0.05). Left electrical axis deviation associated with worse diastolic function and greater atrial diameter. Interventricular and intraventricular mechanical dyssynchrony (ten methods) was similar in the different LBBB patterns (p = ns).

Conclusion

In the two different electrocardiographic patterns of LBBB analyzed, no difference regarding the presence of mechanical dyssynchrony was observed.     

Physiology of cardiac resynchronization

Dyssynchronous ventricular contraction, often associated with delayed electrical activation, contributes to worsened clinical status in patients with chronic dilated heart failure. There are three levels of impaired electromechanical synchrony that can be recognized and potentially improved with pacing methods. Prolonged atrioventricular (AV) delay can promote presystolic mitral regurgitation and impaired left ventricular (LV) filling. Interventricular conduction delay with right ventricular (RV) activation preceding LV activation often occurs in the setting of left bundle branch block or RV apical pacing, and can result in impeded LV filling and ejection. Activation delays within the LV itself (intraventricular dyssynchrony) can cause decreased efficiency of contraction, increased mitral regurgitation, and abnormal ventricular remodeling. Cardiac resynchronization therapy (CRT) can improve ventricular performance in two thirds of patients selected based on QRS duration alone. Improved understanding of the pathophysiology of cardiac dyssynchrony will aid in patient selection and in assessment and optimization of response to CRT.     

Acute Effects of Single‐site Pacing from the Left and Right Ventricle on Ventricular Function and Ventricular–Ventricular Interactions in Children with Normal Hearts

Objective. We studied, as a physiological benchmark, acute effects of right ventricular (RV) apical, RV outflow, and left ventricular (LV) pacing in children with normal cardiac function on LV and RV function and ventricular–ventricular interactions. Design. The design of the study was a prospective, acute intervention. Setting. The study was conducted in a tertiary care electrophysiology laboratory. Population and Methods. Seven children (mean ± SD, 12 ± 4 years) were paced after accessory pathway ablation, at baseline (AOO), and with atrioventricular pacing (DOO) from the RV apex, RV outflow, and left ventricle. Outcome Measures. Right ventricular dP/dT_max and RV dP/dT_neg (high‐fidelity transducer‐tipped catheters, Millar Instruments, Houston, TX, USA), cardiac index (Fick), blood pressure, and QRS duration were measured at each pacing condition. Intra‐ and interventricular mechanical dyssynchrony, systolic‐ and diastolic peak tissue velocities, and isovolumic acceleration were recorded by tissue Doppler imaging at the lateral mitral, septal, and tricuspid annuli at each condition. Results at each pacing condition were compared by repeated‐measures analysis of variance. Results. Pacing prolonged QRS duration, causing electrical dyssynchrony (86 ± 19 ms [baseline], 141 ± 44 ms [RV apex], 121 ± 18 ms [RV outflow], and 136 ± 34 ms [LV], P < .01). Right ventricular outflow pacing caused LV intraventricular delay (63 ± 52 vs. 12 ± 7 ms, P < .05). Right ventricular apical pacing caused interventricular delay (61 ± 29 vs. 25 ± 18 ms, P < .05). There were no significant changes in blood pressure, cardiac index, RV dp/dT_max, RV dP/dT_neg, regional tissue velocities, or isovolumic acceleration during any of the pacing conditions, indicating preserved ventricular function and hemodynamics. No important ventricular–ventricular interactions were seen. Conclusions. In children with normal cardiac anatomy and function, single‐site RV apical, RV outflow, and LV pacing induce electromechanical dyssynchrony without significantly changing ventricular function or hemodynamics, or adversely affecting ventricular–ventricular interactions.