Echocardiographic evaluation of cardiac resynchronization therapy: ready for routine clinical use?

Left Ventricular "Longitudinal Rotation" and Conduction Abnormalities-A New Outlook on Dyssynchrony

BACKGROUND

The complete left bundle branch block (CLBBB) results in ventricular dyssynchrony and a reduction in systolic and diastolic efficiency. We noticed a distinct clockwise rotation of the left ventricle (LV) in patients with CLBBB ("longitudinal rotation").

AIM

The aim of this study was to quantify the "longitudinal rotation" of the LV in patients with CLBBB in comparison to patients with normal conduction or complete right bundle branch block (CRBBB).

METHODS

Sixty consecutive patients with normal QRS, CRBBB, or CLBBB were included. Stored raw data DICOM 2D apical-4 chambers view images cine clips were analyzed using EchoPac plugin version 203 (GE Vingmed Ultrasound AS, Horten, Norway). In EchoPac-Q-Analysis, 2D strain application was selected. Instead of apical view algorithms, the SAX-MV (short axis-mitral valve level) algorithm was selected for analysis. A closed loop endocardial contour was drawn to initiate the analysis. The "posterior" segment (representing the mitral valve) was excluded before finalizing the analysis. Longitudinal rotation direction, peak angle, and time-to-peak rotation were recorded.

RESULTS

All patients with CLBBB (n = 21) had clockwise longitudinal rotation with mean four chamber peak rotation angle of -3.9 ± 2.4°. This rotation is significantly larger than in patients with normal QRS (-1.4 ± 3°, p = 0.005) and CRBBB (0.1 ± 2.2°, p = 0.00001). Clockwise rotation was found to be correlated to QRS duration in patients with the non-RBBB pattern. The angle of rotation was not associated with a lower ejection fraction or the presence of regional wall abnormalities.

CONCLUSIONS

Significant clockwise longitudinal rotation was found in CLBBB patients compared to normal QRS or CRBBB patients using speckle-tracking echocardiography.

Cardiac resynchronization therapy for the failing systemic right ventricle: A systematic review

Patients with a systemic right ventricle (SRV) are at high risk for development of heart failure early in life. An SRV is encountered in patients with congenitally corrected transposition of the great arteries (CCTGA) or dextro-transposition of the great arteries (DTGA) with previous atrial switch repair (Mustard or Senning procedure). Progressive heart failure is one of the leading cause of mortality in these patients. Therefore, cardiac resynchronization therapy (CRT) has gained increasing momentum for use in this challenging congenital heart disease (CHD) population. However, current guidelines differ in recommendations for CRT in patients with an SRV as evidence supporting CRT has thus far only been described in case reports and retrospectively in relatively small study populations. In fact, the European Society of Cardiology Guideline for the management of grown-up congenital heart disease consider CRT to be 'experimental' in this population. This systematic review critically summarizes current literature on CRT in SRV patients and provides future perspectives for further research in this challenging and growing CHD population.

Benefits of Multisite/Multipoint Pacing to Improve Cardiac Resynchronization Therapy Response

This article provides a general overview of the underlying mechanisms that support pacing from more discrete points and/or a wider vector (multisite and multipoint pacing) to improve left ventricular resynchronization. We performed a critical overview of the current literature and to identify some remaining knowledge gaps to spur further research. It was not our goal to provide a systematic review with a comprehensive bibliography, but rather to focus on selected publications that, in our opinion, have either expertly reviewed a specific aspect of cardiac resynchronization therapy or have been landmark studies in the field.

Acute biventricular hemodynamic effects of cardiac resynchronization therapy in right bundle branch block

BACKGROUND

Controversy remains regarding the use of cardiac resynchronization therapy (CRT) in patients with heart failure with right bundle branch block (RBBB) and reduced left ventricular (LV) ejection fraction. Moreover, little is known about acute hemodynamic changes with CRT in this subgroup as compared with patients with left bundle branch block (LBBB).

OBJECTIVE

The purpose of this study was to evaluate the acute biventricular hemodynamic response of CRT and other pacing configurations, including the effects of atrioventricular (AV) delay and atrial pacing, to understand the effects of CRT in RBBB.

METHODS

Forty patients (9 with RBBB and 31 with LBBB) undergoing CRT implantation underwent temporary pacing with varying configurations and AV delay. The acute hemodynamic response was assessed via invasive measurements of dP/dt_max (maximal rate of change in pressure) in the left ventricle (LV) as well as the right ventricle (RV) in patients with RBBB.

RESULTS

Patients with LBBB had a greater LV dP/dt_max response to CRT than did patients with RBBB. In patients with RBBB, single- or dual-site RV pacing configurations resulted in greater increases in RV dP/dt_max than did biventricular pacing. Optimal AV delays that maximized RV dP/dt_max were shorter than optimal AV delays for LV dP/dt_max. Furthermore, AV delays chosen to maximize improvement in RV dP/dt_max frequently resulted in negative effects on LV dP/dt_max.

CONCLUSION

These findings demonstrate a complex relationship between pacing configuration, AV delay, and hemodynamic responses. The biventricular hemodynamic response in patients with heart failure with RBBB might be improved by optimizing pacing modalities and AV delays. This may be particularly important in patients with diseases in whom RV failure predominates, such as patients with pulmonary hypertension and LV assist device.

A new use for maximum deflection index: Detection of intraventricular dyssynchrony

AIM

CRT has been shown to be very beneficial for patients with reduced LVEF, symptomatic HF and increased QRS width. But many patients do not benefit from CRT. Maximum deflection index (MDI) is a quantitive measure of the rapidity of depolarization of the myocardium. In previous studies, high MDI was found to indicate epicardial origin of ventricular tachycardia. We aimed to detect the relationship between echocardiographic intraventricular dyssynchrony and MDI.

METHODS

We included 144 patients with HF, QRS≥120ms, LBBB, NYHA II-IV, LVEF<35% and scheduled for CRT (90 male, 54 female; mean age 65.3±9.9years). Septal-lateral >60ms delay for the beginning of systolic velocity in TDI and septum-posterior >130ms delay in M-mode were accepted as intraventricular dyssynchrony. The MDI was calculated by dividing the time from onset of the QRS complex to the earliest point of maximum deflection in V5-V6 by the QRS duration.

RESULTS

Septal-lateral delay was associated with MDI and QRS width in bivariate analysis. In logistic regression analysis, MDI (beta=0,264, p=0.001) and QRS width (beta=0,177, p=0.028) were found to be independent parameters for predicting significant septal-lateral delay. MDI was also associated with significant septum-posterior delay in bivariate correlations and ROC curve (p<0.05 for all). In bivariate analysis MDI was associated with intraventricular dyssynchrony in both non-strict LBBB (r=0.261, p=0.010) and strict LBBB (r=0.305, p=0.035) groups.

CONCLUSION

MDI is closely associated with all echocardiographic intraventricular dyssynchrony parameters. We suggest that MDI may be used as a marker to detect patients with increased intraventricular dyssynchrony. It may be useful to integrate MDI to CRT patient selection procedure in order to minimize nonresponders.

Surgical Aspects of Cardiac Resynchronisation Therapy

Despite significant advances in the pharmacological treatment of heart failure, rates of mortality and morbidity from the condition remain a concern. The introduction of cardiac resynchronisation therapy (CRT) has been a welcome addition to the treatment strategy of patients who display ventricular dyssynchrony. Several control studies have shown significant benefits from this intervention in particular improved mortality and reduction in symptom burden. In this short review, we focus on several concepts of CRT and discuss the implications of surgical implantation of the left ventricular (LV) lead as compared to the standard transvenous approach.

Pulmonary transit time measurement by contrast-enhanced ultrasound in left ventricular dyssynchrony

Background

Pulmonary transit time (PTT) is an indirect measure of preload and left ventricular function, which can be estimated using the indicator dilution theory by contrast-enhanced ultrasound (CEUS). In this study, we first assessed the accuracy of PTT-CEUS by comparing it with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Secondly, we tested the hypothesis that PTT-CEUS correlates with the severity of heart failure, assessed by MRI and N-terminal pro-B-type natriuretic peptide (NT-proBNP).

Methods and results

Twenty patients referred to our hospital for cardiac resynchronization therapy (CRT) were enrolled. DCE-MRI, CEUS, and NT-proBNP measurements were performed within an hour. Mean transit time (MTT) was obtained by estimating the time evolution of indicator concentration within regions of interest drawn in the right and left ventricles in video loops of DCE-MRI and CEUS. PTT was estimated as the difference of the left and right ventricular MTT. Normalized PTT (nPTT) was obtained by multiplication of PTT with the heart rate. Mean PTT-CEUS was 10.5±2.4s and PTT-DCE-MRI was 10.4±2.0s (P=0.88). The correlations of PTT and nPTT by CEUS and DCE-MRI were strong; r=0.75 (P=0.0001) and r=0.76 (P=0.0001), respectively. Bland–Altman analysis revealed a bias of 0.1s for PTT. nPTT-CEUS correlated moderately with left ventricle volumes. The correlations for PTT-CEUS and nPTT-CEUS were moderate to strong with NT-proBNP; r=0.54 (P=0.022) and r=0.68 (P=0.002), respectively.

Conclusions

(n)PTT-CEUS showed strong agreement with that by DCE-MRI. Given the good correlation with NT-proBNP level, (n)PTT-CEUS may provide a novel, clinically feasible measure to quantify the severity of heart failure.

Clinical Trial Registry: NCT01735838

Clinical utility of speckle-tracking echocardiography in cardiac resynchronisation therapy

Cardiac resynchronisation therapy (CRT) can profoundly improve outcome in selected patients with heart failure; however, response is difficult to predict and can be absent in up to one in three patients. There has been a substantial amount of interest in the echocardiographic assessment of left ventricular dyssynchrony, with the ultimate aim of reliably identifying patients who will respond to CRT. The measurement of myocardial deformation (strain) has conventionally been assessed using tissue Doppler imaging (TDI), which is limited by its angle dependence and ability to measure in a single plane. Two-dimensional speckle-tracking echocardiography is a technique that provides measurements of strain in three planes, by tracking patterns of ultrasound interference ('speckles') in the myocardial wall throughout the cardiac cycle. Since its initial use over 15 years ago, it has emerged as a tool that provides more robust, reproducible and sensitive markers of dyssynchrony than TDI. This article reviews the use of two-dimensional and three-dimensional speckle-tracking echocardiography in the assessment of dyssynchrony, including the identification of echocardiographic parameters that may hold predictive potential for the response to CRT. It also reviews the application of these techniques in guiding optimal LV lead placement pre-implant, with promising results in clinical improvement post-CRT.

Assessment of cardiac dyssynchrony by cardiac MR: A comparison of velocity encoding and feature tracking analysis

PURPOSE

To investigate whether cardiac magnetic resonance (cardiac MR)-based feature tracking (FT) may be used for robust and rapid quantification of dyssynchrony by measurement of the septal to lateral delay (SLD).

MATERIALS AND METHODS

Healthy volunteers (n = 18) and patients with mechanical dyssynchrony (n = 17) were investigated. Velocity encoding cardiac MR (VENC) and steady-state free precession (SSFP)-cine sequences were acquired in identical horizontal long axis (HLA) positions using a 1.5T MR scanner. Using FT and VENC cardiac MR software, myocardial velocity curves were calculated for the basal segment of the septal and lateral wall. Based on the quantity of dyssynchrony, the patients were classified into three subgroups (minimal, intermediate, extensive). SLD and patient classification were compared and intra- as well as interobserver variability assessed.

RESULTS

VENC and FT SLD measurements showed strong correlation (r = 0.94) and good agreement (mean 1.33 msec; limits of agreement [LoA] -2.96 to 5.63). Dyssynchrony subclassification based on FT was identical to VENC in 83% of the cases. While FT correctly classified all healthy subjects, three patients with mechanical dyssynchrony were misclassified. Compared to VENC, FT showed higher intra- and interobserver variability. VENC: intraobserver: mean 2.5 msec, LoA -17.5 to 22.5; interobserver: mean 1.5 msec, LoA -17.2 to 21.9. FT: intraobserver: mean 2.1 msec, LoA 27.6 to 31.8; interobserver: mean 2.4 msec LoA -31.4 to 34.5.

CONCLUSION

Cardiac MR-based FT analysis may be used for rapid appraisal of left ventricle cardiac dyssynchrony from SSFP images. However, FT results are less accurate and reproducible compared to VENC-based assessment of SLD.

Current Technology to Maximize Cardiac Resynchronization Therapy Benefit for Patients With Symptomatic Heart Failure

The incidence of heart failure (HF) continues to increase, affecting millions of people in the United States each year. Cardiac resynchronization therapy (CRT) has been used and studied for patients with symptomatic HF for more than 20 years. The purpose of this article is to review technologies and developments to help maximize CRT for patients with symptomatic HF. Although most interventions to optimize CRT are physician directed, nurses also have an important role in the care and education of patients with symptomatic HF and can affect clinical outcomes. Therefore, nurses’ understanding of CRT and measures to maximize this lifesaving therapy is critical in HF management.

Echocardiographic assessment of left ventricular dyssynchrony in Egyptian children with congestive heart failure due to dilated cardiomyopathy

OBJECTIVE

To evaluate the presence of cardiac dyssynchrony in Egyptian children with congestive heart failure due to dilated cardiomyopathy.

MATERIALS AND METHODS

A total of 30 children with congestive cardiac failure due to dilated cardiomyopathy and 30 healthy age-matched controls were examined with conventional echocardiography, tissue Doppler, and speckle tracking imaging.

RESULTS

Conventional Doppler echocardiography demonstrated significant left ventricular systolic and diastolic dysfunction in the patient group. Tissue Doppler showed significant decrease in S-wave velocity and E'/A' ratio, and prolonged isovolumic contraction and relaxation times of mitral annulus as well as significant prolongation in mean difference between time-to-peak systolic strain of the basal septal and basal lateral segments in the patient group compared with the control group (p<0.005). Speckle tracking imaging demonstrated significant prolongation in mean difference between time-to-peak systolic strain of anteroseptal and posterior segments in both circumferential and radial strain analysis in the patient group than in the control group (p<0.005). It also demonstrated significant prolongation in the mean difference between time-to-peak systolic strain of the basal septal and basal lateral segments in longitudinal strain analysis in the patient group than in the control group (p<0.005). A significant increase in the standard deviation of time-to-peak strain, as a marker of increased intra-ventricular dyssynchrony, was present in the patient group compared with the control group (p=0.008).

CONCLUSION

Children with congestive heart failure due to dilated cardiomyopathy usually suffer from significant intra-ventricular dyssynchrony. Tissue Doppler imaging and speckle tracking imaging strain analysis are helpful tools to detect the presence of cardiac dyssynchrony.

Computerized interpretation of the prehospital electrocardiogram: predictive value for ST segment elevation myocardial infarction and impact on on-scene time

Introduction:

Computerized interpretation of the prehospital electrocardiogram (ECG) is increasingly being used in the basic life support (BLS) ambulance setting to reduce delays to treatment for patients suspected of ST segment elevation myocardial infarction (STEMI).

Objectives:

To estimate 1) predictive values of computerized prehospital 12-lead ECG interpretation for STEMI and 2) additional on-scene time for 12-lead ECG acquisition.

Methods:

Over a 2-year period, 1,247 ECGs acquired by primary care paramedics for suspected STEMI were collected. ECGs were interpreted in real time by the GEMarquette 12SL ECG analysis program. Predictive values were estimated with a bayesian latent class model incorporating the computerized ECG interpretations, consensus ECG interpretations by study cardiologists, and hospital diagnosis. On-scene time was compared for ambulance-transported patients with (n 5 985) and without (n 5 5,056) prehospital ECGs who received prehospital aspirin and/or nitroglycerin.

Results:

The computer's positive and negative predictive values for STEMI were 74.0% (95% credible interval [CrI] 69.6–75.6) and 98.1% (95% CrI 97.8–98.4), respectively. The sensitivity and specificity were 69.2% (95% CrI 59.0–78.5) and 98.9% (95% CrI 98.1–99.4), respectively. Prehospital ECGs were associated with a mean increase in on-scene time of 5.9 minutes (95% confidence interval 5.5–6.3).

Conclusions:

The predictive values of the computerized prehospital ECG interpretation appear to be adequate for diversion programs that direct patients with a positive result to hospitals with angioplasty facilities. The estimated 26.0% chance that a positive interpretation is false is likely too high for activation of a catheterization laboratory from the field. Acquiring prehospital ECGs does not substantially increase on-scene time in the BLS setting.

Efficacy of cardiac resynchronization with defibrillator insertion in patients undergone coronary artery bypass graft: a cohort study of cardiac function

INTRODUCTION

Cardiac resynchronization therapy (CRT) is a proven therapeutic method in selected patients with heart failure and systolic dysfunction which increases left ventricular function and patient survival. We designed a study that included patients undergoing coronary artery bypass graft (CABG), with and without CRT-defibrillator (CRT-D) inserting and then measured its effects on these two groups.

PATIENTS AND METHODS

Between 2010 and 2013, we conducted a prospective cohort study on 100 coronary artery disease patients where candidate for CABG. Then based on the receiving CRT-D, the patients were categorized in two groups; Group 1 ( n = 48, with CRT-D insertion before CABG) and Group 2 ( n = 52 without receiving CRT-D). Thereafter both of these groups were followed-up at 1-3 months after CABG for mortality, hospitalization, atrial fibrillation (AF), echocardiographic assessment, and New York Heart Association (NYHA) class level.

RESULTS

The mean age of participants in Group 1 (48 male) and in Group 2 (52 male) was 58 ± 13 and 57 ± 12 respectively. Difference between Groups 1 and 2 in cases of mean left ventricular ejection fraction (LVEF) changes and NYHA class level was significant ( P > 0.05). Hospitalization ( P = 0.008), mortality rate ( P = 0.007), and AF were significantly different between these two groups.

CONCLUSIONS

The results showed that the increase in LVEF and patient's improvement according to NYHA-class was significant in the first group, and readmission, mortality rate and AF was increased significantly in the second group.

Effects of atrioventricular and interventricular delays on gas exchange during exercise in patients with heart failure

BACKGROUND

Cardiac resynchronization therapy (CRT) has been an important treatment for heart failure. However, it is controversial as to whether an individualized approach to altering AV and VV timing intervals would improve outcomes. Changes in respiratory patterns and gas exchange are dynamic and may be influenced by timing delays. Light exercise enhances the heart and lung interactions. Thus, in this study we investigated changes in non-invasive gas exchange by altering AV and VV timing intervals during light exercise.

METHODS

Patients (n = 20, age 66 ± 9 years) performed two walking tests post-implantation. The protocol evaluated AV delays (100, 120, 140, 160 and 180 milliseconds), followed by VV delays (0, -20 and -40 milliseconds) while gas exchange was assessed.

RESULTS

There was no consistent group pattern of change in gas exchange variables across AV and VV delays (p > 0.05). However, there were modest changes in these variables on an individual basis with variations in VE/VCO2 averaging 10%; O2 pulse 11% and PETCO2 5% across AV delays, and 4%, 8% and 2%, respectively, across VV delays. Delays that resulted in the most improved gas exchange differed from nominal in 17 of 20 subjects.

CONCLUSION

Gas exchange measures can be improved by optimization of AV and VV delays and thus could be used to individualize the approach to CRT optimization.

Biventricular pacing in heart failure: a review

Biventricular pacing has been an exciting recent advance in the management of drug-refractory heart failure. This new therapy has evolved as much from necessity as scientific observation, since benefits derived from pharmacotherapy currently appear to have reached their peak. Clinical trials of biventricular pacing are establishing morbidity and mortality benefits in heart failure. New challenges in the use of these pacemakers are now arising. These include the accurate diagnosis of ventricular dyssynchrony and, hence, potential responders to the refinement of implantation of the left ventricular lead to the appropriate dyssynchronous ventricular area and optimization of pacemaker programming. This review gives a general overview of the principles and the current evidence for the use of biventricular pacemakers in the treatment of heart failure. In addition, a discussion of current research and future projects is included.

Evaluation of cardiac dyssynchrony with longitudinal strain analysis in 4-chamber cine MR imaging

PURPOSE

We investigated the clinical performance of evaluation of cardiac mechanical dyssynchrony with longitudinal strain analysis using four-chamber (4CH) cine magnetic resonance imaging (MRI).

MATERIALS AND METHODS

We retrospectively enrolled 73 chronic heart failure patients (41 men, 32 women; mean age, 57 years, NYHA 2, 3, and 4) who underwent a cardiac MRI in the present study. The left ventricular dyssynchrony (LVD) and interventricular dyssynchrony (IVD) indices were calculated by longitudinal strain analysis using 4 CH cine MRI. The LVD and IVD indices were compared by the Wilcoxon rank-sum test between the patients with indication for cardiac resynchronization therapy (CRT) (n = 13) and without indication for CRT (n = 60), with LGE (n = 40) and without LGE (n = 27), the CRT responders (n = 8) and non-responders (n = 6), respectively.

RESULTS

LVD in the patients with indication for CRT were significantly longer than those without indication for CRT (LVD: 92 ± 65 vs. 28 ± 40 ms, P<.01). LVD and IVD were significantly longer in the patients with LGE than those without LGE (LVD: 54 ± 58 vs. 21 ± 30 ms, P<.01 and IVD: 51 ± 39 vs. 23 ± 34 ms, P<.01). LVD and IVD in the CRT responders were significantly longer than the CRT non-responders (LVD: 126 ± 55 vs. 62 ± 55 ms, P<.01 and IVD: 96 ± 39 vs. 52 ± 40 ms, P<.05).

CONCLUSION

Longitudinal strain analysis with 4CH cine MRI could be useful for clinical examination in the evaluation of cardiac mechanical dyssynchrony.

Improved relationship between left and right ventricular electrical activation after cardiac resynchronization therapy in heart failure patients can be quantified by body surface potential mapping

OBJECTIVES

Few studies have evaluated cardiac electrical activation dynamics after cardiac resynchronization therapy. Although this procedure reduces morbidity and mortality in heart failure patients, many approaches attempting to identify the responders have shown that 30% of patients do not attain clinical or functional improvement. This study sought to quantify and characterize the effect of resynchronization therapy on the ventricular electrical activation of patients using body surface potential mapping, a noninvasive tool.

METHODS

This retrospective study included 91 resynchronization patients with a mean age of 61 years, left ventricle ejection fraction of 28%, mean QRS duration of 182 ms, and functional class III/IV (78%/22%); the patients underwent 87-lead body surface mapping with the resynchronization device on and off. Thirty-six patients were excluded. Body surface isochronal maps produced 87 maximal/mean global ventricular activation times with three regions identified. The regional activation times for right and left ventricles and their inter-regional right-to-left ventricle gradients were calculated from these results and analyzed. The Mann-Whitney U-test and Kruskall-Wallis test were used for comparisons, with the level of significance set at p≤0.05.

RESULTS

During intrinsic rhythms, regional ventricular activation times were significantly different (54.5 ms vs. 95.9 ms in the right and left ventricle regions, respectively). Regarding cardiac resynchronization, the maximal global value was significantly reduced (138 ms to 131 ms), and a downward variation of 19.4% in regional-left and an upward variation of 44.8% in regional-right ventricular activation times resulted in a significantly reduced inter-regional gradient (43.8 ms to 17 ms).

CONCLUSIONS

Body surface potential mapping in resynchronization patients yielded electrical ventricular activation times for two cardiac regions with significantly decreased global and regional-left values but significantly increased regional-right values, thus showing an attenuated inter-regional gradient after the cardiac resynchronization therapy.

Optimizing cardiac resynchronization therapy for congestive heart failure

In patients with advanced systolic heart failure and mechanical dyssynchrony, cardiac resynchronization therapy (CRT) is an effective means of improving symptoms and reducing mortality. There are now several recognized approaches to optimize CRT. Imaging modalities can assist with identifying the myocardium with the latest mechanical activation for targeted left ventricular lead implantation. Device programming can be tailored to maximize biventricular pacing, and thereby is its benefit. Cardiac imaging has shown that atrioventricular and interventricular intervals can be adjusted to further reduce dyssynchrony. We review these various approaches that maximize the benefit derived from CRT.

Measures of dyssynchrony in the left ventricle of healthy children and young patients with dilated cardiomyopathy

BACKGROUND

Doppler tissue imaging may help identify children with dyssynchrony who could benefit from resynchronization therapy. However, few studies have quantified dyssynchrony measures in children; no study has investigated the relationship among age, heart rate, and dyssynchrony measures in children; and no study has quantified cross-correlation delay in children. The aim of this study was to test the hypotheses that measures of left ventricular dyssynchrony would correlate with age, primarily because of the correlation between heart rate and age, and that children with cardiomyopathy would have left ventricular dyssynchrony.

METHODS

Sixty healthy children and 11 children with dilated cardiomyopathy were prospectively enrolled. Seven dyssynchrony measures were quantified: septal-to-lateral delay, peak velocity difference, the standard deviations of times to peak in 12 segments in systole and diastole, and cross-correlation delay in systole, diastole, and the whole cycle.

RESULTS

The seven dyssynchrony measures were either not correlated with age or only weakly correlated with age after correcting for heart rate using Bazett's formula. Septal-to-lateral delay, peak velocity difference, and the standard deviation of times to peak in 12 segments in systole showed dyssynchrony in 57% to 85% of normal controls, compared with 20% for cross-correlation delay in the whole cycle and 3% for the standard deviation of times to peak in 12 segments in diastole. Cross-correlation delay in systole, cross-correlation delay in diastole, cross-correlation delay in the whole cycle, and the standard deviation of times to peak in 12 segments in diastole were elevated in children with dilated cardiomyopathy compared with controls.

CONCLUSIONS

Echocardiographic dyssynchrony measures should be corrected for heart rate using Bazett's formula in children. Time-to-peak Doppler tissue imaging dyssynchrony measures classify many healthy children as having abnormalities with the timing of left ventricular contraction, which suggests that the methodology is not accurate in children. In preliminary studies, cross-correlation dyssynchrony measures show elevated systolic and diastolic measures of dyssynchrony in children with dilated cardiomyopathy compared with controls, which deserves further investigation to help identify children who may benefit from resynchronization therapy.

Use of real-time three-dimensional echocardiography to assess left ventricular systolic synchronization after dual-chamber pacing therapy

This study was designed to evaluate the left ventricular systolic synchronization in patients implanted with dual-chamber DDD mode cardiac pacemakers by real-time three-dimensional echocardiography (RT3DE). Twenty patients implanted with DDD mode cardiac pacemakers for 12 months and 20 healthy subjects underwent RT3DE. This method provided left ventricular end-diastolic volume (LEDV), left ventricular end-systolic volume (LESV), stroke volume (SV), left ventricular ejection fraction (LVEF), the mean value of the time to minimal systolic volume of the 16 left ventricular segments (Tmean), the standard deviation of Tmean (T-SD), the maximal difference of the time to minimal systolic volume of the 16 left ventricular segments (Tmax) and time-volume curves of the 16 left ventricular segments. Results showed that compared with the healthy group, LESV was significantly increased (P<0.05), SV and LVEF were significantly decreased (P<0.05) and T-SD and Tmax were significantly prolonged (P<0.05) in patients implanted with DDD mode cardiac pacemakers. The time to minimal systolic volume of the 16 left ventricular segments time-volume curves differed in patients implanted with DDD mode cardiac pacemakers. Asynchronization of the left ventricular systolic performance in patients implanted with DDD mode cardiac pacemakers was observed. The results showed that RT3DE is a quantitative method used to evaluate left ventricular systolic synchronization.

Real-time three-dimensional echocardiographic evaluation of left ventricular systolic synchronicity in patients with chronic heart failure: comparison with tissue Doppler imaging

BACKGROUND

To investigate the clinical value of real-time three-dimensional echocardiography (RT-3DE) for assessing of left ventricular systolic synchronicity.

METHODS

Thirty healthy volunteers and 62 patients with congestive heart failure (CHF) were enrolled. The SD of time to peak systolic motion (TDI-Ts12-SD) was measured with tissue Doppler imaging in 12 myocardial segments. The SD and maximal difference of the time to minimal systolic volume (Tmsv) between 16, 12, or 6 myocardial segments, expressed as a percentage of cardiac cycle duration, were measured with RT-3DE and labeled Tmsv16-SD%, Tmsv12-SD%, Tmsv6-SD%, Tmsv16-D%, Tmsv12-D%, and Tmsv6-D%, respectively. The Spearman coefficient and Kappa value were calculated, and Bland-Altman analysis was performed to investigate the correlation and agreement between the two methods. Tmsv values were compared with ejection fraction (EF).

RESULTS

There was a moderately positive (p< 0.01) correlation between TDI-Ts12-SD and Tmsv16-SD%, Tmsv12-SD%, Tmsv16-D%, and Tmsv12-D% (r = 0.65, 0.64, and 0.65, respectively, with Kappa values of 0.66, 0.65, 0.72, and 0.74, respectively, p< 0.01). Tmsv16-SD%, Tmsv12-SD%, and Tmsv12-D% were significantly different between CHF patients with EF ≤ 35% and those with EF > 35%.

CONCLUSIONS

RT-3DE can be used in patients with CHF to quantify left ventricular mechanical dyssynchrony. Tmsv12-SD% and Tmsv12-D% were the best indices of left ventricular systolic synchronicity in relation to the severity of CHF as evaluated from EF.

Optimizing electrode placement for hemodynamic benefit in cardiac resynchronization therapy

BACKGROUND

Research is needed to explore the relative benefits of alternative electrode placements in biventricular and left ventricular (LV) pacing for heart failure with left bundle branch block (LBBB).

METHODS

A fast computational model of the left ventricle, running on an ordinary laptop computer, was created to simulate the spread of electrical activation over the myocardial surface, together with the resulting electrocardiogram, segmental wall motion, stroke volume, and ejection fraction in the presence of varying degrees of mitral regurgitation. Arbitrary zones of scar and blocked electrical conduction could be modeled.

RESULTS

Simulations showed there are both sweet spots and poor spots for LV electrode placement, sometimes separated by only a few centimeters. In heart failure with LBBB, pacing at poor spots can produce little benefit or even reduce pumping effectiveness. Pacing at sweet spots can produce up to 35% improvement in ejection fraction. Relatively larger benefit occurs in dilated hearts, in keeping with the greater disparity between early and late activated muscle. Sweet spots are typically located on the basal to midlevel, inferolateral wall. Poor spots are located on or near the interventricular septum. Anteroapical scar with conduction block causes little shift in locations for optimal pacing. Hearts with increased passive ventricular compliance and absence of preejection mitral regurgitation exhibit greater therapeutic gain. The durations and wave shapes of QRS complexes in the electrocardiogram can help predict optimum electrode placement in real time.

CONCLUSIONS

Differences between poor responders and hyperresponders to cardiac resynchronization therapy can be understood in terms of basic anatomy, physiology, and pathophysiology. Computational modeling suggests general strategies for optimal electrode placement. In a given patient heart size, regional pathology and regional dynamics allow individual pretreatment planning to target optimal electrode placement.

Implantable cardioverter defibrillators and cardiac resynchronisation therapy

Implantable cardioverter defibrillators and cardiac resynchronisation therapy (CRT) have become standard of care in modern treatment for heart failure. Results from trials have provided ample evidence that CRT, in addition to its proven benefits in patients with symptomatic heart failure (New York Heart Association [NYHA] class III), might also reduce morbidity and mortality in those with mildly symptomatic heart failure (NYHA class II). As a result, the 2010 European Society of Cardiology guidelines now recommend CRT for both patient populations. In this review we summarise and critically assess the landmark randomised clinical trials REVERSE, MADIT-CRT, and RAFT. Furthermore, we discuss the rationale and available evidence for other emerging indications of CRT, including its use in patients with a mildly reduced left ventricular ejection fraction (>35%), in those with a narrow QRS complex (≤120 ms), and in those with concomitant bradyarrhythmic pacemaker indications. We also focus on patients who do not respond to CRT, and on CRT optimisation.

Acute Cardiac Resynchronization Therapy for the Failing Left, Right, or Single Ventricle After Repaired Congenital Heart Disease

Use of cardiac resynchronization in children and young adults with congenital heart disease has been described in a variety of anecdotal cases and pooled institutional summaries which report mid-term results. This manuscript addresses use of cardiac resynchronization and/or multisite pacing in children in the acute postoperative period with a failing right, left, or single ventricle.

Influence of aetiology on long-term effects of resynchronization on cardiac structure and function in patients treated with β-blockers

OBJECTIVES

Cardiac resynchronization therapy (CRT) elicits more beneficial effects on left-ventricular (LV) structure and function, and long-term clinical outcomes in nonischemic heart failure patients. Rates of β-blocker use in recent heart failure trials are higher than in CRT trials and this may influence the response to CRT. This study examined the long-term effects of CRT on LV structure and function in New York Heart Association class III-IV β-blocker-treated patients.

METHODS

One hundred and four (41 ischemic and 63 nonischemic) CRT patients, who were receiving β-blockers before and throughout 12 months following device implantation, were retrospectively selected. Variations in echocardiographic parameters recorded before, and 6 and 12 months after CRT were analyzed.

RESULTS

Selected patients were all stable on β-blockers, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (97%) and diuretics (97%) before implantation. CRT was associated with significant improvements in LV morphological and systo-diastolic functional parameters at 6 months, with further improvements between 6 and 12 months seen in nonischemic patients only. Accordingly, rates of echocardiographic response to CRT were similar at 6 months but significantly higher in nonischemic patients after 1 year. The degree of reduction in LV diameters and volumes, and of increase in ejection fraction, was significantly larger in nonischemic patients at both 6 and 12 months. In addition, a significant reduction in LV mass and severity of mitral regurgitation was more evident in nonischemic patients both 6 and 12 months following CRT.

CONCLUSIONS

Ischemic aetiology of heart failure is associated with less favorable long-term effects of CRT on LV structure and function despite the systematic use of β-blockers.