Left ventricular dyssynchrony using three-dimensional speckle-tracking imaging as a determinant of torsional mechanics in patients with idiopathic dilated cardiomyopathy

The aim of this study was to use 3-dimensional (3D) speckle-tracking echocardiography to test the hypothesis that left ventricular (LV) dyssynchrony may negatively affect LV torsional mechanics in patients with idiopathic dilated cardiomyopathy (IDC) and that LV torsion may improve after cardiac resynchronization therapy. This study included 65 subjects; 20 with IDC with ejection fractions ≤35% and wide QRS complexes (≥120 ms), 20 with IDC with ejection fractions ≤35% and narrow QRS complexes (<120 ms), and 25 controls. LV dyssynchrony index was determined as the SD of time to peak 3D speckle-tracking radial strain and regional heterogeneity of LV rotation (rotational dispersion index) as the SD of 3D speckle-tracking time to peak rotation. All rotational indexes were significantly impaired in patients with IDC, while LV torsion in patients with IDC with wide QRS complexes was significantly smaller than that in patients with IDC with narrow QRS complexes and controls. Conversely, LV dyssynchrony index (127.3 ± 24.0 ms [p <0.01 vs controls and vs patients with narrow QRS complexes] vs 88.8 ± 22.5 ms [p <0.01 versus controls] vs 30.9 ± 10.0 ms) and rotational dispersion index (115.1 ± 27.5 ms [p <0.01 vs controls and vs patients with narrow QRS complexes] vs 96.0 ± 23.4 ms [p <0.01 versus controls] vs 45.0 ± 13.7 ms) were significantly higher in patients with IDC with wide QRS complexes. Multivariate analysis showed that the LV ejection fraction (β = 0.688, p <0.001) and rotational dispersion index (β = -0.249, p <0.01) were independent determinants of LV torsion. Moreover, LV torsion in patients with IDC with wide QRS complexes improved after cardiac resynchronization therapy (p <0.05), along with reductions in LV dyssynchrony and rotational dispersion indexes. In conclusion, these findings obtained with a novel 3D speckle-tracking system feature a novel aspect of LV torsional mechanics and demonstrate its association with LV dyssynchrony.     

Cardiac resynchronization therapy in patients with a narrow QRS complex.

OBJECTIVES: The purpose of this study was to evaluate the effects of cardiac resynchronization therapy (CRT) in heart failure patients with narrow QRS complex (<120 ms) and evidence of left ventricular (LV) dyssynchrony on tissue Doppler imaging (TDI). BACKGROUND: Cardiac resynchronization therapy is beneficial in selected heart failure patients with wide QRS complex (> or =120 ms). Patients with narrow QRS complex are currently not eligible for CRT, and the potential effects of CRT are not well studied. METHODS: Thirty-three consecutive patients with narrow QRS complex and 33 consecutive patients with wide QRS complex (control group) were prospectively included. All patients needed to have LV dyssynchrony > or =65 ms on TDI, New York Heart Association (NYHA) functional class III/IV heart failure, and LV ejection fraction < or =35%. RESULTS: Baseline characteristics, particularly LV dyssynchrony, were comparable between patients with narrow and wide QRS complex (110 +/- 8 ms vs. 175 +/- 22 ms; p = NS). No significant relationship was observed between baseline QRS duration and LV dyssynchrony (r = 0.21; p = NS). The improvement in clinical symptoms and LV reverse remodeling was comparable between patients with narrow and wide QRS complex (mean NYHA functional class reduction 0.9 +/- 0.6 vs. 1.1 +/- 0.6 [p = NS] and mean LV end-systolic volume reduction 39 +/- 34 ml vs. 44 +/- 46 ml [p = NS]). CONCLUSIONS: Cardiac resynchronization therapy appears to be beneficial in patients with narrow QRS complex and severe LV dyssynchrony on TDI, with similar improvement in symptoms and comparable LV reverse remodeling to patients with wide QRS complex. The current results need confirmation in larger patient cohorts.     

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。     

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.     

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.     

Triple-Site Versus Standard Cardiac Resynchronization Therapy Study (TRUST CRT): Clinical Rationale, Design, and Implementation

Background: Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with heart failure (HF), lowered LV ejection fraction, and wide QRS. However, many patients (≤40%) do not respond to this form of pacing. TRUST CRT is a prospective, single-center, randomized, single-blind, parallel, and controlled study that has been designed to treat patients with moderate to severe HF (NYHA III-IV), QRS ≥120 ms, sinus rhythm, LV dysfunction (EF ≤ 35%), and signs of mechanical dyssynchrony.
Objective: The primary objective will evaluate the 6-month's combined endpoint of alive status, freedom from hospitalization for HF or heart transplantation, relative ≥10% increase in LV ejection fraction, ≥10% in peak oxygen consumption, and ≥10% in 6-minute walking distance.
Methods: Patients with HF receiving optimal pharmacotherapy, with LV dysfunction, mechanical dyssynchrony, wide QRS and sinus rhythm will be randomized in a 1: 1 fashion to standard or triple-site CRT-D. Patients will be followed for 1 week, 1, 3, and 6 months during a blind phase, then every 6 months until study completion. One hundred patients will be enrolled by the study center.
Conclusions: TRUST CRT is a randomized, clinical trial in CRT candidates to evaluate the effectiveness of triple-site pacing versus standard resynchronization in patients with HF.     

Left ventricular electromechanical delay in patients with heart failure and normal QRS duration and in patients with right and left bundle branch block.

AIMS: We sought to define the reference values of intra-left ventricular (LV) electromechanical delay (EMD), and to assess the prevalence (and pattern) of intra-LV dyssynchrony in patients with heart failure (HF) and normal QRS and in patients with right and left bundle branch block. METHODS AND RESULTS: We used tissue Doppler imaging echocardiography and a six-LV wall model to study LV EMD in 103 patients [41 with HF and normal QRS, 22 with right bundle branch block (RBBB), and 40 with left bundle branch block (LBBB)], and in 59 controls. In controls, the median intra-LV EMD was 17 ms, (inter-quartile range 13-30); 95% of controls had a value < or =41 ms. Patients showed a longer intra-LV EMD than controls: 33 ms (20-57) in patients with normal QRS, 32 ms (23-50) in RBBB patients, and 50 ms (30-94) in LBBB patients. Intra-LV dyssynchrony (defined as intra-LV EMD >41 ms) was present in 39, 36, and 60% of the patients, respectively. On average, HF patients showed the same pattern of activation as controls, from the septum to the posterior wall, but activation times were significantly prolonged. In RBBB patients the activation sequence was directed from inferior to anterior and in LBBB from anterior to inferior wall. CONCLUSIONS: Left ventricular dyssynchrony was present in several patients with HF and normal QRS, and in patients with RBBB; conversely, 40% of LBBB patients showed values of LV EMD within the normal range. Left ventricular activation sequence was different between groups. Assessment of LV synchronicity by means of imaging techniques may be more important than QRS duration or morphology in selecting patients for cardiac resynchronization treatment.     

Benefits of cardiac resynchronization therapy for heart failure patients with narrow QRS complexes and coexisting systolic asynchrony by echocardiography.

OBJECTIVES: This study was designed to evaluate the role of cardiac resynchronization therapy (CRT) in heart failure (HF) patients with narrow QRS complexes (<120 ms) and echocardiographic evidence of mechanical asynchrony. BACKGROUND: Cardiac resynchronization therapy is currently recommended to advanced HF patients with prolonged QRS duration. Echocardiographic assessment of systolic mechanical asynchrony has been proven useful to predict a favorable response after CRT. METHODS: A total of 102 HF patients with New York Heart Association (NYHA) functional class III or IV were enrolled. Among them, 51 had wide QRS (>120 ms) and 51 had narrow QRS (<120 ms). Tissue Doppler imaging (TDI) was employed to select patients with systolic asynchrony (increased asynchrony index) in the narrow-QRS group. Clinical and echocardiographic assessments were performed at baseline and 3 months after CRT. RESULTS: There was a significant reduction of left ventricular (LV) end-systolic volume in both narrow (122 +/- 42 cc vs. 103 +/- 47 cc, p < 0.001) and wide (148 +/- 74 cc vs. 112 +/- 64 cc, p < 0.001) QRS groups. Improvement of NYHA functional class (both p < 0.001), maximal exercise capacity (both p < 0.05), 6-min hall-walk distance (both p < 0.01), ejection fraction (both p < 0.001), and mitral regurgitation (both p < 0.005) was also observed. In both groups, the degree of baseline mechanical asynchrony determined LV reverse remodeling to a similar extent, as shown by the superimposed regression lines. Withholding CRT for 4 weeks resulted in loss of echocardiographic benefits. CONCLUSIONS: Cardiac resynchronization therapy for HF patients with narrow QRS complexes and coexisting mechanical asynchrony by TDI results in LV reverse remodeling and improvement of clinical status. The amplitude of benefit is similar to the wide-QRS group provided that similar extent of systolic asynchrony is selected.     

Left ventricular dyssynchrony predicts response and prognosis after cardiac resynchronization therapy

OBJECTIVES: This study was designed to predict the response and prognosis after cardiac resynchronization therapy (CRT) in patients with end-stage heart failure (HF). BACKGROUND: Cardiac resynchronization therapy improves HF symptoms, exercise capacity, and left ventricular (LV) function. Because not all patients respond, preimplantation identification of responders is needed. In the present study, response to CRT was predicted by the presence of LV dyssynchrony assessed by tissue Doppler imaging. Moreover, the prognostic value of LV dyssynchrony in patients undergoing CRT was assessed. METHODS: Eighty-five patients with end-stage HF, QRS duration >120 ms, and left bundle-branch block were evaluated by tissue Doppler imaging before CRT. At baseline and six months follow-up, New York Heart Association functional class, quality of life and 6-min walking distance, LV volumes, and LV ejection fraction were determined. Events (death, hospitalization for decompensated HF) were obtained during one-year follow-up. RESULTS: Responders (74%) and nonresponders (26%) had comparable baseline characteristics, except for a larger dyssynchrony in responders (87 +/- 49 ms vs. 35 +/- 20 ms, p < 0.01). Receiver-operator characteristic curve analysis demonstrated that an optimal cutoff value of 65 ms for LV dyssynchrony yielded a sensitivity and specificity of 80% to predict clinical improvement and of 92% to predict LV reverse remodeling. Patients with dyssynchrony >/=65 ms had an excellent prognosis (6% event rate) after CRT as compared with a 50% event rate in patients with dyssynchrony <65 ms (p < 0.001). CONCLUSIONS: Patients with LV dyssynchrony >/=65 ms respond to CRT and have an excellent prognosis after CRT.     

Doppler Tissue Imaging Assessment of Left Ventricular Systolic Dyssynchrony in Severe Heart Failure Patients With a Normal QRS Duration

Objectives To assess the prevalence of systolic dyssynchrony of the left ventricular （LV） walls in patients of heart failure（HF） with a normal QRS duration by Doppler tissue imaging （DTI）. Methods 20 patients of HF with a normal QRS duration and 20 healthy individuals were investigated with DTI to quantitatively analyze their pulsed-wave Doppler spectrum of basal and middle segments in six walls of left ventricle. The time between the onset of the QRS complex of the surface ECG and the onset of the systolic wave of pulsed-wave Doppler spectrum was measured （TS）. LV systolic synchronization was assessed by the maximal difference （MD） in time of TS, the standard deviation （SD） and the coefficient of variation （CV） of TS in the all 12 LV segments. Results When a TS-MD of TS〉 53.08 ms, a TS-SD of TS 〉18.08 ms and a TS-CV of TS 〉 0.91 （＋1.65 SD of normal controls） was used to define significant systolic dyssynchrony, the prevalence of systolic dyssynchrony was 55.0 %, 55.0 % and 55.0 %, respectively, in the HF patients group, significantly higher than those in the normal control and the locations of delayed contraction of these patients were different. Conclusions LV systolic dyssynchrony could be commonly demonstrated by DTI in HF patients with a normal QRS duration. This finding will support the view about the possibility that more HF patients could benefit from cardiac resynchronization therapy.     

Effect of primary mitral regurgitation on left ventricular synchrony

Mitral regurgitation (MR) promotes left ventricular (LV) dilatation and eccentric remodeling. In the presence of LV dyssynchrony and heart failure, cardiac resynchronization therapy decreases the severity of MR. Whether primary MR can cause LV dyssynchrony is unknown. We investigated whether moderate to severe primary MR causes LV dyssynchrony in the presence of LV dilation and an ejection fraction (EF) >55%. We studied 37 normal subjects and 22 patients with moderate to severe MR and no coronary artery disease. Electrocardiographically gated cine and tagged cardiac magnetic resonance imaging was performed. Two-dimensional, maximum-circumferential shortening strain and time-to-peak strain (TTPS) were computed using harmonic-phase analysis of tagged magnetic resonance imaging. LV dyssynchrony was assessed by comparing TTPS delay of various LV quadrants and TTPS dispersion among the contralateral quadrants in patients with MR and normal subjects. Statistical comparison was done using a generalized linear model for repeated measurements. LV end-diastolic and LV end-systolic volumes were significantly larger in patients with MR versus normal subjects (207 +/- 11 vs 130 +/- 4 and 73 +/- 5 vs 47 +/- 2 ml, p <0.001). LVEF did not differ in patients with MR and normal subjects. The difference in the TTPS among various quadrants and the dispersion among the contralateral quadrants of the LV myocardium was similar between patients with MR and normal subjects. In conclusion, moderate to severe MR does not cause LV dyssynchrony in patients with LV dilatation and normal LVEF. Thus, cardiac resynchronization therapy in the absence of LV dyssynchrony may not decrease the severity of MR.     

心脏再同步化对窄QRS波群慢性心力衰竭患者的疗效观察

目的 观察心脏再同步化治疗对窄QRS波群慢性心力衰竭患者的临床疗效. 方法 对5例QRS时间<120ms的慢性心力衰竭患者行双心室再同步起搏治疗.术后随访(15.6±12.1)个月,观察心功能、活动耐量、夜间心率、心率变异性(SDNN)和左心室射血分数;组织多普勒检测左心室内各心室壁收缩期达峰时间标准差(Ts-SD);三维超声心动描记术检测左心室16、12、6节段达最小容积点时间的标准差(Tmsv-Dis)和最大时间差(Tmsv-Dif). 结果 治疗后心功能NYHA分级从Ⅲ、Ⅳ级改善为Ⅱ、Ⅲ级,活动度从(0.03±0.05)h/d增加至(2.93±1.10)h/d,夜间心率由(85.0±3.6)次/min降低至(62.3±2.5)次/min,SDNN从(48.3±7.6)ms升至(116.7±5.8)ms,左心室射血分数从(21.2±4.5)%提高至(34.7±5.1)%(P<0.05). Ts-SD,Tmsv-Dis及Tmsv-Dif均有明显减低(P<0.05). 结论 窄QRS波群慢性心力衰竭患者可接受心脏再同步化治疗,术前应用超声心动描记术及组织多普勒等评价患者心室运动的失同步是很必要的.     

Frequency of left ventricular dyssynchrony in patients with heart failure and a narrow QRS complex

Cardiac resynchronization therapy (CRT) is considered a major advance in the treatment of patients with heart failure. The presence of left ventricular (LV) dyssynchrony seems mandatory for a positive response to CRT. Currently, only patients with wide QRS complexes are considered for CRT, although patients with narrow QRS complexes may also have LV dyssynchrony. In the present study, the incidence of LV dyssynchrony was prospectively evaluated in 64 patients with heart failure and narrow QRS complexes using tissue Doppler imaging.     

Regional Heterogeneity of Systolic Dysfunction Is Associated with Ventricular Dyssynchrony in Patients with Idiopathic Dilated Cardiomyopathy and Narrow QRS Complex

Background: Regional heterogeneity of left ventricular (LV) contraction, known as dyssynergy, in idiopathic dilated cardiomyopathy (IDC) patients has been previously reported, but no comprehensive analysis of this abnormality has been made. The purpose of this study was to test the hypothesis that regional heterogeneity of systolic dysfunction is associated with LV dyssynchrony in IDC patients with a narrow QRS complex using novel three‐dimensional (3D) speckle‐tracking strain. Methods: We studied 54 consecutive IDC patients with ejection fraction (EF) of 34 ± 12% and QRS duration of 102 ± 13 msec (all <120 msec), and 30 age‐matched normal controls. The 3D speckle‐tracking LV dyssynchrony (LV dyssynchrony index) was quantified from all 16 LV sites to determine the standard deviation (SD) of time‐to‐peak strain. Similarly, regional heterogeneity of LV systolic function (LV dyssynergy index) was quantified from all 16 LV sites to establish the SD of peak 3D speckle‐tracking strain. Results: The LV dyssynergy and dyssynchrony indices of IDC patients were significantly larger than those of normal controls. Furthermore, IDC patients showed significantly higher Z‐scores for septum and inferior regions than for the free wall (3.34 ± 1.21 vs. 1.69 ± 1.06 and 2.79 ± 1.30 vs. 1.69 ± 1.06, respectively, P < 0.001). An important findings of multivariable analysis was that the LV dyssynergy index (β = 0.69, P < 0.001) and LVEF (β = ?0.34, P = 0.001) were independent determinants of the LV dyssynchrony index. Conclusion: 3D speckle‐tracking strain revealed that the myocardial systolic dysfunction of IDC patients with a narrow QRS complex has a marked heterogeneous regional distribution. This regional heterogeneity as well as systolic dysfunction is thought to lead to LV dyssynchrony.     

Relation of left ventricular systolic dyssynchrony in patients with heart failure to left ventricular ejection fraction and to QRS duration

Left ventricular (LV) systolic dyssynchrony is an important pathologic mechanism in patients with heart failure (HF). However, the prevalence of intraventricular dyssynchrony in patients with different LV ejection fractions (EFs) is unknown. This study evaluated 402 consecutive patients with HF (mean age 64.99 +/- 13.15 years, 72.4% men) and 120 healthy controls. Dyssynchrony indexes included the SD of the time to peak systolic velocity (Ts) in ejection phase in the 12-segmental model (Ts-SD) and the difference in Ts between basal septal and basal lateral segments (Ts-Septal-Lateral) using tissue Doppler imaging. Patients were divided into 3 groups according to LVEF (LVEF <20%, >20% to 35%, and >35% to 50%) and compared with healthy controls. Both indexes were significantly higher in all 3 LVEF groups compared with controls (p <0.0001). Based on the established cut-off values, systolic dyssynchrony was equally prevalent in all 3 LVEF groups and was 67%, 62%, and 55% using Ts-SD and 38%, 36%, and 35% using Ts-Septal-Lateral, respectively. However, the prevalence of systolic dyssynchrony was higher using Ts-SD than Ts-Septal-Lateral (chi-square = 94.43, p <0.001). Conversely, the prevalence of electrical dyssynchrony, defined as a >120-ms QRS duration, decreased significantly with increasing LVEF (44%, 35%, and 16%; chi-square 5.60, p <0.001). In conclusion, the prevalence of mechanical systolic dyssynchrony was independent of severity of LV systolic dysfunction. This may implicate the potential role of cardiac resynchronization therapy for those with LVEF of 35% to 50%, in particular when systolic dyssynchrony is present.     

Fragmented narrow QRS complex: Predictor of left ventricular dyssynchrony in non-ischemic dilated cardiomyopathy

BackgroundCardiac resynchronization therapy is an important therapeutic modality in drug refractory symptomatic patients of heart failure with wide QRS (≥120 ms) on electrocardiogram. However, wide QRS (considered as a marker of electrical dyssynchrony) occurs in only 30% of heart failure patients, making majority of drug refractory heart failure patients ineligible for resynchronization therapy. Significant numbers of patients with narrow QRS have echocardiographic evidence of left ventricular dyssynchrony. However, there is sparse data about additional features on the surface ECG which can predict intraventricular dyssynchrony. This study was undertaken to assess the utility of fragmented narrow QRS complex to predict significant intraventricular dyssynchrony in symptomatic patients of non-ischemic dilated cardiomyopathy.Method100 symptomatic patients of non-ischemic dilated cardiomyopathy with narrow QRS complexes (50 each with fragmented and normal QRS) were recruited. Tissue Doppler imaging was used to assess intraventricular dyssynchrony as per ‘Yu index’.Results78% patients (n = 39) in fQRS complex group and 14% (n = 7) in normal QRS complex group had significant intraventricular dyssynchrony (χ² = 20.61; p < 0.000005). fQRS complexes had 84.78% sensitivity, 79.62% specificity, a positive predictive value of 78% and negative predictive value of 86% to detect intraventricular dyssynchrony. fQRS also had sensitivity and specificity of 93% and 90% respectively to localize the dyssynchronous segment.ConclusionfQRS is a marker of electrical dyssynchrony, which results in significant intraventricular dyssynchrony in patients of non-ischemic dilated cardiomyopathy and a narrow QRS interval. fQRS localizes the dyssynchronous segment and might be useful in identifying patients who can benefit from cardiac resynchronization therapy.     

Cardiac resynchronization therapy in patients with narrow QRS

Conduction delay affecting 30-50% of patients with NYHA class III-IV heart failure (HF) mainly results from left bundle branch block and leads to deterioration of cardiac contractility through intra- and interventricular dyssynchrony. Cardiac resynchronization therapy (CRT) has class I recommendation for the treatment of patients with severe systolic HF who have left ventricular ejection fraction less or equal to 35%, QRS duration greater than or equal to 120 ms. Nevertheless some studies have shown that systolic asynchrony is present in 27-43% of HF patients with narrow QRS complexes (defined as <120 ms). We present here results of CRT in 20 patients (13 male, 7 female). Main indication for CRT was ventricular dyssynchrony during basic cardiac rhythm or cardiac pacing independently of QRS width. In 4 patients width of QRS complex was less than 120 ms, in 3 QRS varied from 120 to 149 ms pts and in 13 it was equal to or exceeded 150 ms. CRT in patients with narrow QRS resulted in clinical improvement associated with increase of cardiac contractility and decrease of left ventricular end systolic volume. This allows to conclude that CRT can be beneficial for HF patients with narrow QRS and ventricular dyssynchrony.     

Relation between heart rate and left ventricular mechanical dyssynchrony in patients with end-stage renal disease

The effect of heart rate (HR) on left ventricular (LV) mechanical dyssynchrony has not been studied by phase analysis of myocardial perfusion imaging and has yielded conflicting results by echocardiography. We measured indexes of LV dyssynchrony by automated analysis of gated single-photon emission computed tomography in 140 patients with end-stage renal disease (ESRD) and 133 subjects with normal renal function (control group). Patients with abnormal perfusion pattern or QRS duration >120 ms were excluded. HR at time of acquisition of gated images was recorded. LV ejection fraction (EF), volumes, mass, and 2 indexes of dyssynchrony, phase SD and bandwidth, were derived. Almost 50% of patients in each group had an abnormal LVEF (<50%). HR at rest ranged from 48 to 113 beats/min (75 ± 13). Patients with abnormal LVEF had a higher phase SD (30 ± 13° vs 22 ± 11° and 28 ± 16° vs 15 ± 6° for the ESRD and control groups, respectively, p <0.001 each) and higher histographic bandwidth (88 ± 44° vs 62 ± 33° and 80 ± 49° vs 43 ± 14° for the ESRD and control groups, p <0.001 each). Patients with ESRD and normal LVEF had higher SD and bandwidth than the control group (22 ± 11° vs 15 ± 6° and 62 ± 33° vs 43 ± 14°, respectively, p <0.001 each). The control and ESRD groups were divided into tertiles based on HR. The phase SD and bandwidth were similar in the first (slowest HR) and third (highest HR) tertiles in every group (p = NS). There were no significant correlations between phase SD or bandwidth and HR in either group. In conclusion, within the HR range examined in this cross-sectional study, there was no relation between HR at rest and LV dyssynchrony.     

Optimal role of rest and stress echocardiography in cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is an effective treatment for patients with advanced heart failure (HF), depressed left ventricular (LV) function and wide QRS complex. CRT improves symptoms, exercise capacity, LV function and reduces HF hospitalization and mortality rates. However, in parallel with the impressive results for CRT in several large trials, a consistent percentage of patients do not respond to CRT when the traditional patient selection criteria are applied. The prevalence of non-responders is about 30% when clinical end-points are considered but it is much higher (≥ 45%) if echocardiographic end-points are used. Reduction of the number of non-responders is currently one of the main challenges in the field of CRT. Response to CRT has been related to the presence of cardiac dyssynchrony prior to implantation. LV dyssynchrony can be evaluated using different echocardiographic methods. When LV dyssynchrony is added to traditional patient selection criteria, the prevalence of non-responders decreases considerably. However, the value of LV dyssynchrony to predict response to CRT has shown some limitations and is possibly not sufficient. CRT response is clearly modulated by several factors. Regional and global myocardial viability are key pieces of the puzzle as well as the presence and severity of mitral regurgitation (MR). Echocardiography thus plays an important role in the care of HF patients treated with cardiac resynchronization therapy and is useful to assess acute and long-term beneficial effects of CRT. Numerous recent published reports have used echocardiographic techniques to potentially help patient selection for CRT prior to implantation and to optimize device settings afterwards. These topics are discussed in this review.