Intra-left ventricular electromechanical asynchrony

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.

Prevalence of cardiac dyssynchrony and correlation with atrio-ventricular block and QRS width in dilated cardiomyopathy: an echocardiographic study

INTRODUCTION

Cardiac dyssynchrony causes disorganised cardiac contraction, delayed wall contraction and reduced pumping efficiency. We aimed to assess the prevalence of different types of dyssynchrony in patients with dilated cardiomyopathy (DCM), and to establish the correlation between atrio-ventricular block and atrio-ventricular dyssynchrony (AVD), and between impaired intra-ventricular conduction and the existence of inter-ventricular dyssynchrony (inter-VD) and intra-left ventricular dyssynchrony (intra-LVD).

METHODS

We included 40 patients in New York Heart Association stage III or IV, admitted consecutively with DCM with severe left ventricular dysfunction (left ventricular end-diastolic diameter ≥ 60 mm and/or ≥ 30 mm/m(2)) and left ventricular ejection fraction < 35%. Electrocardiographic and echocardiographic data were evaluated in all patients. Patients were divided into two groups: group 1: eight patients, with a QRS duration ≥ 120 ms, and all presented with left bundle branch block; group 2: 32 patients with a narrow QRS < 120 ms.

RESULTS

Overall, the mean age was 54.7 ± 16.8 years and patients in group 1 were older (67.2 ± 13.6 vs 51.5 ± 15.8 years, p = 0.01). The prevalence of atrio-ventricular dyssynchrony (AVD), inter-VD and intra-LVD was respectively 40, 47.5 and 70%. Two patients (5%) did not exhibit dyssynchrony. AVD was present with a similar frequency in the two groups (37.5% in group 1 vs 40.6% in group 2, p = 0.8). There was no correlation of the magnitude of AVD with the duration of the PR interval (from the beginning of the P wave to the beginning of the QRS complex) (r(2) = 0.02, p = 0.37) or the QRS width (r(2) = 0.01, p = 0.38). A greater proportion of patients with inter-VD was observed in group 1 (87.5 vs 60%, p = 0.03). There was a trend towards a more important inter-ventricular mechanical delay according to QRS width (r(2) = 0.009, p = 0.06). The proportion of intra-LVD was similar in all groups, with a high prevalence (87.5% in group 1 and 65.6% in group 2, p = 0.39).

CONCLUSION

The assessment of cardiac dyssynchrony is possible in our country. Intra-ventricular mechanical dyssynchrony had a high prevalence in patients with DCM, irrespective of the QRS width. These data emphasise the usefulness of echocardiography in the screening of patients.

Left ventricular dyssynchrony is an early manifestation of heart involvement in sickle cell anemia

BACKGROUND

Sickle cell anemia (SCA) is the most common inherited anemia. Although heart involvement in SCA is well-established, there is no data about changes of contraction synchrony in SCA. Therefore, we aimed to study the left ventricular contraction synchrony in SCA patients with narrow QRS and normal ejection fraction (EF).

METHODS

Thirty-six patients with SCA and 37 age- and gender-matched control subjects were included in the study. Left ventricular dyssynchrony was investigated by color-coded tissue Doppler imaging.

RESULTS

The SCA patients had lower hemoglobin (Hb) and higher ferritin, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, left ventricular mass index (LVMI), and pulmonary artery pressure. Peak A velocity, Dt, and E/E' values were higher in the SCA group however, E/A ratio and average Em were higher in the control group. LV systolic dyssynchrony parameters including Ts-SD-12, Ts-12, Ts-SD-6, and Ts-6 were found to be higher in SCA group when compared with controls. In addition to that, the patients with ventricular dyssynchrony (a Ts-SD-12 > 34.4 msec) were higher in the SCA group than the control group (55.6% vs. 8.1%, P < 0.001). In the correlation analysis, systolic dyssynchrony parameters were found to be correlated with Hb, ferritin, LVMI, E/A, Dt, Em.

CONCLUSION

Our results revealed that in SCA patients with normal EF and narrow QRS, left ventricular systolic dyssynchrony was an early manifestation of heart involvement and might be coexisted with or preceding diastolic dysfunction.

Cardiac magnetic resonance evaluation of the impact of interventricular and intraventricular dyssynchrony on cardiac ventricular systolic and diastolic function in patients with isolated left bundle branch block

Ventricular dyssynchrony significantly impairs cardiac performance. However, the independent role of interventricular dyssynchrony (interVD) and intraventricular dyssynchrony (intraVD) in the development of abnormalities of systolic and diastolic performance is unclear. Cardiac magnetic resonance imaging was performed in 39 patients with left bundle branch block and 13 healthy patients. Structural and functional parameters of the left ventricle and degrees of interVD and intraVD were measured. We found that interVD was inversely correlated with left ventricular (LV) ejection fraction (r = -0.8, p <0.0001) and positively correlated with LV end-diastolic volume (r = 0.4, p <0.01), LV end-systolic volume (r = 0.6, p <0.0001), and LV mass (r = 0.4, p <0.01), thus indicating that interVD significantly affects systolic function and favors ventricular remodeling. Multivariate analysis further confirmed that interVD was an independent predictor of systolic dysfunction. Interestingly, we found that interVD was not associated with abnormalities of diastolic performance. Conversely, we found that intraVD significantly impaired diastolic function, whereas it had no effect on systolic function. IntraVD was inversely correlated with peak filling rate (r = -0.7, p <0.0001) and 1/2 filling fraction (r = 0.4, p = 0.04) and positively correlated with time to peak filling rate (r = 0.6, p <0.0001), validated parameters of diastolic function. Multivariate analysis confirmed that intraVD was an independent predictor of diastolic dysfunction. In conclusion, our study suggests that the 2 components of ventricular dyssynchrony differently affect cardiac performance. If confirmed in prospective studies, our results may help to predict the prognosis of patients with left bundle branch block and different degrees of interVD and intraVD, particularly those subjects undergoing cardiac resynchronization therapy.

Clinical implication of mechanical dyssynchrony in heart failure

Mechanical dyssynchrony is a common phenomenon in patients with congestive heart failure, which usually identified by noninvasive cardiac imaging tools such as echocardiography. It demonstrates electromechanical delay in some regions of the failing heart which in turn contributes to further impairment of cardiac function. The diagnostic, therapeutic and prognostic values of mechanical dyssynchrony have been reported in a number of studies. Therefore, this review describes briefly the methods of measurement, but more importantly, explains the clinical implication of its assessment in heart failure related aspects including cardiac resynchronization therapy, functional mitral regurgitation, diastolic heart failure and mortality.

Dynamic dyssynchrony and impaired contractile reserve of the left ventricle in beta-thalassaemia major: an exercise echocardiographic study

BACKGROUND

Performance of the left ventricle during exercise stress in thalassaemia patients is uncertain. We aimed to explore the phenomenon of dynamic dyssynchrony and assess contractile reserve in patients with beta-thalassaemia major and determine their relationships with myocardial iron load.

METHODS AND RESULTS

Thirty-two thalassaemia patients (16 males), aged 26.8 ± 6.9 years, without heart failure and 17 healthy controls were studied. Their left ventricular (LV) volumes, ejection fraction, systolic dyssynchrony index (SDI), and myocardial acceleration during isovolumic LV contraction (IVA) were determined at rest and during submaximal bicycle exercise testing using 3-dimensional and tissue Doppler echocardiography. Myocardial iron load as assessed by T2* cardiac magnetic resonance in patients were further related to indices of LV dyssynchrony and contractile reserve. At rest, patients had significantly greater LV SDI (p<0.001) but similar IVA (p = 0.22) compared with controls. With exercise stress, the prevalence of mechanical dyssynchrony (SDI>4.6%, control+2SD) increased from baseline 25% to 84% in patients. Δ SDI(exercise-baseline) correlated with exercise-baseline differences in LV ejection fraction (p<0.001) and stroke volume (p = 0.006). Compared with controls, patients had significantly less exercise-induced increase in LV ejection fraction, cardiac index, and IVA (interaction, all p<0.05) and had impaired contractile reserve as reflected by the gentler IVA-heart rate slope (p = 0.018). Cardiac T2* in patients correlated with baseline LV SDI (r = -0.44, p = 0.011) and IVA-heart rate slope (r = 0.36, p = 0.044).

CONCLUSIONS

Resting LV dyssynchrony is associated with myocardial iron load. Exercise stress further unveils LV dynamic dyssynchrony and impaired contractile reserve in patients with beta-thalassaemia major.

Association of left ventricular mechanical dyssynchrony with survival benefit from revascularization: a study of gated positron emission tomography in patients with ischemic LV dysfunction and narrow QRS

PURPOSE

LV mechanical dyssynchrony (LVMD) is a risk marker in narrow QRS cardiomyopathy, but its association with treatment outcome is not well defined. We determined the incremental prognostic value of LVMD in ischemic cardiomyopathy, and assessed its interaction with scar, myocardium in jeopardy and subsequent revascularization.

METHODS

Stress and rest (82)Rb gated PET were performed in 486 consecutive patients (66 ± 11 years of age, 82 % men, LV ejection fraction 26 ± 6 %) with ischemic cardiomyopathy and QRS <120 ms. LVMD was determined as the standard deviation (SD) of the regional time to minimum volume on phase analysis of the gated PET scan. A propensity score was determined to adjust for nonrandomized referral after imaging to coronary artery bypass grafting (CABG). In a Cox proportional hazards model used to determine the association between measures of LVMD and survival time, CABG was included as a time-dependent covariate and the use of an implantable cardiac defibrillator (ICD) after imaging was modeled as a stratification factor.

RESULTS

Over 1.9 ± 1.4 years, 96 patients (20 %) underwent CABG and 108 (22 %) died. LVMD was a predictor of mortality (HR 1.16. 95 % CI 1.03;1.30, per 10° increase in phase SD, p = 0.02) after adjusting for baseline covariates, prior ICD use, the use of postimaging CABG, and other imaging data. There was a significant interaction between phase SD and CABG. Nested Cox models showed that LVMD carried prognostic information incremental to clinical variables, ejection fraction and CABG.

CONCLUSION

LVMD is an independent predictor of all-cause mortality in ischemic cardiomyopathy, and may identify patients with a differential survival benefit from CABG versus medical therapy.

Heart failure with normal ejection fraction: a growing pandemic

Heart failure is a heterogeneous syndrome. Approximately 30-50% of patients with heart failure have normal or near normal left ventricle function. Several epidemiological studies confirm that the prevalence of heart failure with normal ejection fraction is increasing. Given the current trends, heart failure with normal ejection fraction will become the most common form of heart failure, for which we do not currently have an evidence-based successful treatment. This article summarizes the etiology, current recommended guidelines and management options for this clinical manifestation.

Incremental value of global systolic dyssynchrony in determining the occurrence of functional mitral regurgitation in patients with left ventricular systolic dysfunction

AIMS

The aim of this study was to assess the contribution of left ventricular (LV) systolic dyssynchrony to functional mitral regurgitation (MR).

METHODS AND RESULTS

Patients (n = 136) with LV systolic dysfunction (ejection fraction <50%) and at least mild MR were prospectively recruited. The effective regurgitant orifice area (EROA) was assessed by the proximal isovelocity surface area method. Left ventricular global systolic dyssynchrony [the maximal difference in time to peak systolic velocity among the 12 LV segments (Ts-Dif)] and regional systolic dyssynchrony (the delay between the anterolateral and posteromedial papillary muscle attaching sites) were assessed by tissue Doppler imaging. Left ventricular global and regional remodelling, systolic function, indices of mitral valvular and annular deformation were also measured. The size of the EROA correlated with the degrees of mitral deformation, LV remodelling, systolic function, and systolic dyssynchrony. By multivariate logistic regression analysis, the mitral valve tenting area (OR = 1.020, P < 0.001) and the Ts-Dif (OR = 1.011, P = 0.034) were independent determinants of significant functional MR (defined by EROA ≥20 mm(2)). From the receiver-operating characteristic curve, the tenting area of 2.7 cm(2) (sensitivity 83%, specificity 82%, AUC 0.86, P < 0.001) and the Ts-Dif of 85 ms (sensitivity 66%, specificity 72%, AUC 0.74, P < 0.001) were associated with significant functional MR. The assessment of Ts-Dif showed an incremental value over the mitral valve tenting area for determining functional MR (χ(2) = 53.92 vs.49.11, P = 0.028).

CONCLUSION

This cross-sectional study showed that LV global, but not regional systolic dyssynchrony, is a determinant of significant functional MR in patients with LV systolic dysfunction, and is incremental to the tenting area that is otherwise the strongest factor for mitral valve deformation.

Patients with ankylosing spondylitis have evidence of left ventricular asynchrony

OBJECTIVES

Ankylosing spondylitis (AS) is a chronic inflammatory disease that often leads to cardiovascular complications including aortic regurgitation and conduction disturbances. Left ventricular (LV) systolic asynchrony is defined as loss of the simultaneous peak contraction of corresponding cardiac segments. The aim of this study was to evaluate LV systolic asynchrony noninvasively in patients with AS by using tissue synchrony imaging (TSI).

METHODS

Asynchrony was evaluated in 77 AS patients (61 male, mean age 36.4 ± 10 years) and 40 controls (35 male, mean age 39.1 ± 8.2 years). All study population underwent a comprehensive echocardiographic evaluation including TSI. The time to regional peak systolic velocity (Ts) during the ejection phase in LV was measured from TSI images by the six-basal and six-midsegmental model, and four TSI parameters of systolic asynchrony were computed.

RESULTS

The baseline demographic and echocardiographic characteristics were similar between the patients enrolled and controls. All TSI parameters of LV asynchrony were prolonged in patients with AS compared to controls: the standard deviation (SD) of the 12 LV segments Ts (39.6 ± 19.6 vs. 24.7 ± 11.6, P < 0.001); the maximal difference in Ts between any 2 of the 12 LV segments (122.1 ± 52.9 vs. 82.2 ± 38.6, P < 0.001); the SD of the six basal LV segments (33.5 ± 20.2 vs. 23 ± 13.3, P = 0.008); and the maximal difference in Ts between any two of the six basal LV segments (84.6 ± 48.1 vs. 60.4 ± 34.6, P = 0.008). The asynchrony parameters were significantly correlated with index of myocardial performance (Tei index) and peak systolic mitral annular velocity.

CONCLUSION

TSI showed presence of LV systolic asynchrony in patients with AS which may account for the cardiovascular complications of AS.

Diastolic dysfunction and intraventricular dyssynchrony are restored by low intensity exercise training in obese men

The aim of this study was to evaluate the impact of a low-intensity training program on subclinical cardiac dysfunction and on dyssynchrony in moderately obese middle aged men. Ten obese and 14 age-matched normal-weight men (BMI: 33.6 ± 1.0 and 24.2 ± 0.5 kg/m(2)) were included. Obese men participated in an 8-week low-intensity training program without concomitant diet. Cardiac function and myocardial synchrony were assessed by echocardiography with tissue Doppler imaging (TDI) and speckle tracking echocardiography (STE). At baseline, obese men showed diastolic dysfunction on standard echocardiography, lower strain values (systolic strain: 15.9 ± 0.9 vs. 18.8 ± 0.3%, diastolic strain rate: 0.81 ± 0.09 vs. 1.05 ± 0.06 s(-1)), and significant intraventricular dyssynchrony (systolic: 13.3 ± 2.1 vs. 5.4 ± 2.1 ms, diastolic: 17.4 ± 3.2 vs. 9.1 ± 2.1 ms) (P < 0.05 vs. controls for all variables). Training improved aerobic fitness, decreased systolic blood pressure and heart rate, and reduced fat mass without weight loss. Diastolic function, strain values (systolic strain: 17.4 ± 0.9%, diastolic strain rate: 0.96 ± 0.12 s(-1)) and intraventricular dyssynchrony (systolic: 3.3 ± 1.7 ms, diastolic: 5.5 ± 3.4 ms) improved significantly after training (P < 0.05 vs. baseline values for all variables), reaching levels similar to those of normal-weight men. In conclusion, in obese men, a short and easy-to-perform low intensity training program restored diastolic function and cardiac synchrony and improved body composition without weight loss.

Prevalence of dyssynchrony and relation with long-term outcome in patients after acute myocardial infarction

The impact of left ventricular (LV) dyssynchrony on the long-term outcomes of patients with acute myocardial infarction (AMI) remains unknown. The purpose of the present study was to evaluate the prevalence of LV dyssynchrony after AMI and the potential relation with adverse events. A total of 976 consecutive patients admitted with AMI treated with primary percutaneous coronary intervention were evaluated. Two-dimensional echocardiography was performed <48 hours after admission. LV dyssynchrony was assessed with speckle-tracking imaging and calculated as the time difference between the earliest and latest activated segments. Patients were followed up for the occurrence of all-cause mortality (the primary end point) or the composite secondary end point (heart failure hospitalization and all-cause mortality). Within 48 hours of admission for the index infarction, mean LV dyssynchrony was 61 ± 79 ms, and 14% of the patients demonstrated a ≥130-ms time difference, defined as significant LV dyssynchrony. During a mean follow-up period of 40 ± 17 months, 82 patients (8%) reached the primary end point. In addition, 36 patients (4%) were hospitalized for heart failure. The presence of LV dyssynchrony was associated with an increased risk for all-cause mortality and hospitalization for heart failure during long-term follow-up (adjusted hazard ratio 1.06, 95% confidence interval 1.05 to 1.08, p <0.001, per 10-ms increase). Moreover, LV dyssynchrony provided incremental value over known clinical and echocardiographic risk factors for the prediction of adverse outcomes. In conclusion, LV dyssynchrony is a strong predictor of long-term mortality and hospitalization for heart failure in a population of patients admitted with ST-segment elevation AMI treated with primary percutaneous coronary intervention.

Left ventricular performance during para-His pacing in patients with high-grade atrioventricular block: an acute study

AIM

To compare changes in left ventricular (LV) performance and mechanical synchrony between atrial-based pacing with intrinsic conduction (AAI), dual-chamber para-His Pacing (DDD-PHP) and dual-chamber right ventricular septal pacing (DDD-RVS) in patients with high-grade atrioventricular block (AVB).

METHODS AND RESULTS

Patients with high-grade AVB and QRS <120 ms, who had temporary intrinsic atrioventricular (AV) conduction the day after the implantation were included in the study. All patients received a biventricular pacemaker with a para-His lead in the LV port, and a RVS lead in the right ventricular port. Left ventricular three-dimensional echocardiograms, LV outlet tract-velocity time integrals (LVOT-VTI), and LV synchrony with tissue Doppler imaging were recorded during AAI, DDD-PHP, and DDD-RVS. Eleven patients were included. The mean LVOT-VTI was significant lower during DDD-RVS (19.2 ± 5.5 cm) as compared with DDD-PHP (21.4 ± 5.5 cm), P = 0.006 and AAI (21.6 ± 6.8 cm), P = 0.016. The LVEF was higher during AAI than during DDD-PHP (P= 0.02) and DDD-RVS (P< 0.01). The maximal time to peak velocity between basal segments was significant longer with DDD-RVS (95 ± 26 ms) than with AAI (72 ± 30 ms), P = 0.028, whereas no difference was observed between AAI and DDD-PHP (81 ± 42 ms), P = 0.20.

CONCLUSIONS

Acutely, DDD-PHP preserves LV systolic performance and mechanical synchrony as compared with DDD-RVS.

Comparison between tissue doppler imaging (TDI) and tissue synchronization imaging (TSI) in evaluation of left ventricular dyssynchrony in patients with advanced heart failure

BACKGROUND

Assessment of left ventricular (LV) dyssynchrony has an important role in optimizing the selection of cardiac resynchronization therapy (CRT) candidates. We compared a new semiautomatic echocardiographic modality, tissue synchronization imaging (TSI) with a manual method, color-coded tissue Doppler imaging (TDI), in the assessment of LV dyssynchrony in patients with heart failure (HF).

METHODS

Ninety-five patients (age = 54.5 ± 17.1 years, 66.3% male) with advanced HF (NYHA functional class ≥III and ejection-fraction ≤35%) were included in the study and evaluated echocardiographically. The time to regional peak systolic velocity (Ts) in six basal and six middle segments of the LV was measured manually using velocity curves from TDI and semiautomatically using TSI and seven parameters of systolic dyssynchrony were computed.

RESULTS

Overall, a moderate-to-good association was found between Ts derived by these two modalities, whereas the mean of Ts via TSI was significantly lower than that measured by TDI in many LV segments. The agreement between these two modalities in identifying LV dyssynchrony varied from weak to moderate according to various dyssynchrony indices. In comparison to the TDI-derived dyssynchrony indices, TSI showed a high sensitivity of more than 90% using Ts delay at the basal/all LV segments and the indices for their standard deviations (SD) for identifying LV dyssynchrony, whereas the highest specificity of 80% was achieved using the septal-lateral dyssynchrony index in the prediction of LV dyssynchrony.

CONCLUSION

With the aid of selected LV dyssynchrony indices, the TSI method may confer enough sensitivity for a speedy evaluation and initial screening of LV dyssynchrony in HF patients; however, the current technology of TSI does not seem specific enough to replace TDI in the evaluation of dyssynchrony.

Meta-analysis of randomized controlled trials comparing isolated left ventricular and biventricular pacing in patients with chronic heart failure

Cardiac resynchronization therapy (CRT) has been mostly achieved by biventricular pacing (BVP) in patients with chronic heart failure (CHF), although it can also be provided by left ventricular pacing (LVP). The superiority of BVP over LVP remains uncertain. The present meta-analysis of randomized controlled trials was performed to compare the effects of LVP to BVP in patients with CHF. Outcomes analyzed included clinical status (6-minute walk distance, peak oxygen consumption, quality of life, New York Heart Association class), LV function (LV ejection fraction), and LV remodeling (LV end-systolic volume). Five trials fulfilled criteria for inclusion in analysis, which included 574 patients with CHF indicated for CRT. After a midterm follow-up, pooled analysis demonstrated that LVP resulted in similar improvements in 6-minute walk distance (weighted mean difference [WMD] 11.25, 95% confidence interval [CI] -12.39 to 34.90, p = 0.35), quality of life (WMD 0.34, 95% CI -3.72 to 4.39, p = 0.87), peak oxygen consumption (WMD 1.00, 95% CI -0.84 to 2.85, p = 0.29), and New York Heart Association class (WMD -0.19, 95% CI -0.79 to 0.42, p = 0.54). There was a trend toward a superiority of BVP over LVP for LV ejection fraction (WMD 1.28, 95% CI -0.11 to 2.68, p = 0.07) and LV end-systolic volume (WMD -5.73, 95% CI -11.86 to 0.39, p = 0.07). In conclusion, LVP achieves similar improvement in clinical status as BVP in patients with CHF, whereas there was a trend toward superiority of BVP over LVP for LV reverse modeling and systolic function.

Strong coherence between heart rate variability and intracardiac repolarization lability during biventricular pacing is associated with reverse electrical remodeling of the native conduction and improved outcome

BACKGROUND

Reverse electrical remodeling (RER) of the native conduction with cardiac resynchronization therapy (CRT) is associated with decreased mortality and antiarrhythmic effect of CRT. Still, mechanisms of RER are largely unknown. In this study, we explored repolarization lability during biventricular pacing.

METHODS AND RESULTS

The width of native QRS was measured in lead II electrocardiogram before and at least 6 months after implantation of Cardiac Resynchronization Therapy Defibrillator (CRT-D) devices (Medtronic, Inc [Minneapolis, MN, USA] and Boston Scientific Corporate [Natick, MA, USA]) in 69 patients (mean age, 66.3 ± 13.9 years; 39 men [83%]) with either bundle-branch block (44 patients [64%]) or nonspecific intraventricular conduction delay (25 patients [36%]) and New York Heart Association class III and IV heart failure. Narrowing of the native QRS duration for at least 10 milliseconds was considered a marker of RER. Beat-to-beat QT variability and coherence was measured on surface electrocardiogram and intracardiac near-field electrogram during biventricular pacing. Reverse electrical remodeling was observed in 22 patients (32%) in whom coherence between heart rate variability and intracardiac repolarization lability was stronger (0.483 ± 0.243 vs 0.237 ± 0.146, P = .018) and normalized intracardiac QT variance was smaller (0.28 ± 0.0031 vs 0.46 ± 0.0048, P = .049), as compared with that in patients without RER. During a further 24 ± 13 months of follow-up, 21 patients (33%) died or experienced sustained ventricular tachycardia (VT)/ventricular fibrillation. Low intracardiac coherence (≤0.116) was associated with increased risk of death or sustained VT/VT (hazard ratio, 4.33; 95% confidence interval, 1.51-12.40; P = .006).

CONCLUSION

Strong coherence between heart rate variability and intracardiac repolarization lability during biventricular pacing is associated with RER of the native conduction with CRT. Low coherence is associated with increased risk of VT/ventricular fibrillation or death.

A new integrated approach to improve left ventricular electromechanical activation during right ventricular septal pacing

AIMS

The deleterious effects of apical right ventricular pacing has fostered the utilization of alternative pacing sites. Although right ventricular septal (RVS) sites are commonly used, the results have been controversial because of poor standardization of lead position by fluoroscopy. This study investigated the utility of a new RVS pacing technique based on the combination of fluoroscopy (F), and electrophysiological mapping (F + EP). Left ventricular (LV) electromechanical activation was determined in patients undergoing RVS pacing and the results of the F + EP approach were compared with those derived from standard F alone.

METHODS AND RESULTS

Between December 2008 and November 2010 we enrolled 156 consecutive patients undergoing permanent RVS pacing. The standard F approach was used in 93 patients and the F + EP technique was applied to 63 patients. Electromechanical activation was assessed by: (i) electromechanical latency (EML) interval measured from the QRS onset to the mechanical activation of the basal LV and (ii) intra-LV dyssynchrony measured as the interval from the earliest to the latest LV basal motion. Intra-LV dyssynchrony was found in 46.2% patients in the F group compared with 15.9% in the group F + EP (P < 0.001). The F group demonstrated a significantly higher degree of intra-LV dyssynchrony than F + EP group (43.9 ± 24.3 vs. 26.5 ± 15.4 ms; P < 0.001). The F group exhibited a significantly higher EML duration compared with the F + EP group (215.8 ± 25.3 vs. 195.1 ± 17.4 ms; P < 0.001).

CONCLUSION

During RVS pacing, the F + EP approach provides a more physiological LV activation than the standard F technique. The prognostic significance of these short-term findings needs to be correlated with long-term data.

Left ventricular diastolic dyssynchrony assessed with phase analysis of gated myocardial perfusion SPECT: a comparison with tissue Doppler imaging

Purpose

The aim of the current study was to evaluate the feasibility of phase analysis on gated myocardial perfusion SPECT (GMPS) for the assessment of left ventricular (LV) diastolic dyssynchrony in a head-to-head comparison with tissue Doppler imaging (TDI).

Methods

The population consisted of patients with end-stage heart failure of New York Heart Association functional class III or IV with a reduced LV ejection fraction of ≤35%. LV diastolic dyssynchrony was calculated using TDI as the maximal time delay between early peak diastolic velocities of two opposing left ventricle walls (diastolic mechanical delay). Significant LV diastolic dyssynchrony was defined as a diastolic mechanical delay of >55 ms on TDI. Furthermore, phase analysis on GMPS was performed to evaluate LV diastolic dyssynchrony; diastolic phase standard deviation (SD) and histogram bandwidth (HBW) were used as markers of LV diastolic dyssynchrony.

Results

A total of 150 patients (114 men, mean age 66.0 ± 10.4 years) with end-stage heart failure were enrolled. Both diastolic phase SD (r = 0.81, p < 0.01) and diastolic HBW (r = 0.75, p < 0.01) showed good correlations with LV diastolic dyssynchrony on TDI. Additionally, patients with LV diastolic dyssynchrony on TDI (>55 ms) showed significantly larger diastolic phase SD (68.1 ± 13.4° vs. 40.7 ± 14.0°, p < 0.01) and diastolic HBW (230.6 ± 54.3° vs. 129.0 ± 55.6°, p < 0.01) as compared to patients without LV diastolic dyssynchrony on TDI (≤55 ms). Finally, phase analysis on GMPS showed a good intra- and interobserver reproducibility for the determination of diastolic phase SD (ICC 0.97 and 0.88) and diastolic HBW (ICC 0.98 and 0.93).

Conclusion

Phase analysis on GMPS showed good correlations with TDI for the assessment of LV diastolic dyssynchrony.

The assessment of left ventricular systolic asynchrony in patients with primary hyperparathyroidism

OBJECTIVES

Primary hyperparathyroidism (PHP) is associated with a variety of cardiovascular disturbances such as left ventricular (LV) hypertrophy, diastolic cardiac dysfunction, and hypertension. LV asynchrony is defined as the loss of the simultaneous peak contraction of corresponding cardiac segments. The objective of this study was to assess systolic asynchrony in patients with overt hyperparthyroidism.

METHODS

Asynchrony was evaluated in 22 patients with PHP and 24 controls. All the patients and controls were subjected to a tissue synchronization imaging (TSI). The time to regional peak systolic tissue velocity (Ts) in LV by the six-basal-six-midsegmental model was measured on ejection phase TSI images and four TSI parameters of systolic asynchrony were computed.

RESULTS

All TSI parameters of LV asynchrony increased in patients with PHP patients compared to the controls: the standard deviation (SD) of the 12 LV segments Ts (37.3±20.6 vs. 21.5±11.1, P=0.01); the maximal difference in Ts between any 2 of the 12 LV segments (111.2±59.8 vs. 70.2±32.1, P=0.01); the SD of the 6 basal LV segments (42.9±36.4 vs. 18.5±13, P=0.003); and the maximal difference in Ts between any 2 of the 6 basal LV segments (89.6±50.5 vs. 48±31.1, P=0.003).

CONCLUSION

Patients with PHP show an evidence of LV asynchrony by TSI. Asynchrony may contribute to the harmful cardiovascular effects of PHP.

Current and evolving echocardiographic techniques for the quantitative evaluation of cardiac mechanics: ASE/EAE consensus statement on methodology and indications endorsed by the Japanese Society of Echocardiography

Echocardiographic imaging is ideally suited for the evaluation of cardiac mechanics because of its intrinsically dynamic nature. Because for decades, echocardiography has been the only imaging modality that allows dynamic imaging of the heart, it is only natural that new, increasingly automated techniques for sophisticated analysis of cardiac mechanics have been driven by researchers and manufacturers of ultrasound imaging equipment. Several such techniques have emerged over the past decades to address the issue of reader's experience and inter-measurement variability in interpretation. Some were widely embraced by echocardiographers around the world and became part of the clinical routine, whereas others remained limited to research and exploration of new clinical applications. Two such techniques have dominated the research arena of echocardiography: (1) Doppler-based tissue velocity measurements, frequently referred to as tissue Doppler or myocardial Doppler, and (2) speckle tracking on the basis of displacement measurements. Both types of measurements lend themselves to the derivation of multiple parameters of myocardial function. The goal of this document is to focus on the currently available techniques that allow quantitative assessment of myocardial function via image-based analysis of local myocardial dynamics, including Doppler tissue imaging and speckle-tracking echocardiography, as well as integrated back- scatter analysis. This document describes the current and potential clinical applications of these techniques and their strengths and weaknesses, briefly surveys a selection of the relevant published literature while highlighting normal and abnormal findings in the context of different cardiovascular pathologies, and summarizes the unresolved issues, future research priorities, and recommended indications for clinical use.

Serial ultrasound evaluation of intramyocardial strain after reperfused myocardial infarction reveals that remote zone dyssynchrony develops in concert with left ventricular remodeling

This study noninvasively evaluated the development of left ventricular (LV) dyssynchrony following reperfused myocardial infarction (MI) in mice using an ultrasonic speckle-tracking method. Eight C57BL/6J mice were assessed by high-resolution echocardiography at baseline and at eight time-points following MI. Images were acquired at 1mm elevational intervals encompassing the entire LV to determine chamber volumes and radial strain. Receiver-operating characteristic (ROC) analysis of regional radial strain was used to segment the three-dimensional (3-D) LV into infarct, adjacent and remote zones. This in vivo segmentation was correlated to histologic infarct size (R = 0.89, p < 0.01) in a short-axis, slice-by-slice comparison. The onset of dyssynchrony during LV remodeling was assessed by standard deviation of time to peak radial strain in the infarct, adjacent and remote zones. It was discovered that the form of LV dyssynchrony that develops in the remote zone late after MI does so in concert with the progression of LV remodeling (R = 0.70, p < 0.05).

Current and evolving echocardiographic techniques for the quantitative evaluation of cardiac mechanics: ASE/EAE consensus statement on methodology and indications endorsed by the Japanese Society of Echocardiography

Echocardiographic imaging is ideally suited for the evaluation of cardiac mechanics because of its intrinsically dynamic nature. Because for decades, echocardiography has been the only imaging modality that allows dynamic imaging of the heart, it is only natural that new, increasingly automated techniques for sophisticated analysis of cardiac mechanics have been driven by researchers and manufacturers of ultrasound imaging equipment.Several such technique shave emerged over the past decades to address the issue of reader's experience and inter measurement variability in interpretation.Some were widely embraced by echocardiographers around the world and became part of the clinical routine,whereas others remained limited to research and exploration of new clinical applications.Two such techniques have dominated the research arena of echocardiography: (1) Doppler based tissue velocity measurements,frequently referred to as tissue Doppler or myocardial Doppler, and (2) speckle tracking on the basis of displacement measurements.Both types of measurements lend themselves to the derivation of multiple parameters of myocardial function. The goal of this document is to focus on the currently available techniques that allow quantitative assessment of myocardial function via image-based analysis of local myocardial dynamics, including Doppler tissue imaging and speckle-tracking echocardiography, as well as integrated backscatter analysis. This document describes the current and potential clinical applications of these techniques and their strengths and weaknesses,briefly surveys a selection of the relevant published literature while highlighting normal and abnormal findings in the context of different cardiovascular pathologies, and summarizes the unresolved issues, future research priorities, and recommended indications for clinical use.

Echocardiographic assessment of interventricular and intraventricular mechanical synchrony in normal dogs

OBJECTIVES

The aims of this prospective study are to (1) generate normal ranges for interventricular and intraventricular mechanical synchrony in dogs, and (2) generate normal ranges for tissue Doppler imaging (TDI) velocity imaging and speckle tracking strain imaging assessment of segmental intraventricular mechanical synchrony in dogs.

ANIMALS

10 prospectively recruited healthy dogs.

METHODS

Dogs were excluded if they had abnormal historical, physical examination, echocardiographic, ECG or systolic blood pressure findings. Interventricular mechanical synchrony was assessed using time difference between left and right ventricular pre-ejection periods. Intraventricular mechanical synchrony was assessed using both M-mode and color M-mode septal to posterior wall mechanical delay (SPWMD). Intraventricular segmental mechanical synchrony was assessed using both color TDI and speckle tracking strain analysis of segmental myocardial motion during systole and diastole.

RESULTS

All synchrony measures were found to be independent of age or body weight. Normal range for mechanical interventricular synchrony was found to be -10.2 to 12.6 ms. Assessment of mechanical intraventricular synchrony using either M-mode or color M-mode SPWMD was found to be associated with an extremely wide normal range, limiting clinical applicability. Normal ranges for segmental intraventricular mechanical synchrony assessed using either color TDI or speckle tracking were found to be comparable to those published for human subjects.

CONCLUSIONS

Interventricular and intraventricular mechanical synchrony in dogs is independent of age and body weight. The normal ranges identified in this study form a basis for assessment of normal versus abnormal mechanical synchrony in canine cardiovascular disease patients.

The tissue velocity imaging and strain rate imaging in the assessment of interatrial electromechanical conduction in patients with sick sinus syndrome before and after pacemaker implantation

Tissue velocity imaging (TVI) and strain rate imaging (SRI) were recently introduced to quantify myocardial mechanical activity in patients receiving cardiac resynchronization therapy. To clear whether atrial-demand-based (AAI) (R) atrial pacing can fully simulate the electromechanical conduction of physiological state and to clarify which one is more appropriate for the assessment of electromechanical activity of the heart between TVI and SRI, 30 normal subjects and 31 patients with sick sinus syndrome (SSS) before and after AAI(R) pacemaker implantation (PI) were investigated in this study. The results showed that the time intervals (ms), P-SRa assessed by SRI (not P-Va assessed by TVI) prolonged step by step from the lateral wall of the right atrium (RA), the interatrial septum (IAS) and the left atrium (LA) in normal subjects(5.01±0.62, 17.05±3.54 and 45.09±12.26, p<0.01). P-Va and P-SRa did not differ at the RA, IAS and LA in patients with SSS before PI (p>0.05), and they were significant longer than those of normal subjects (p<0.01). However, they shortened to normal levels in patients with SSS after PI and P-SRa showed again the trend of gradually prolonging from the RA, IAS to LA. At the same time, the peak velocities and the peak strain rates during atrial contraction also returned to normal values from lower levels. These data suggested that AAI(R) atrial pacing can successfully reverse the abnormal interatrial electromechanical conduction in patients with SSS, and SRI is more appropriate for the assessment of the electromechanical activity of atrial wall than TVI.

Left-ventricular systolic and diastolic dyssynchrony as assessed by multi-harmonic phase analysis of gated SPECT myocardial perfusion imaging in patients with end-stage renal disease and normal LVEF

BACKGROUND

The purpose of this study was to develop a multi-harmonic phase analysis method to measure diastolic dyssynchrony from conventional gated SPECT myocardial perfusion imaging (MPI) data and to compare it with systolic dyssynchrony in normal subjects and in patients with end-stage renal disease (ESRD) and normal left-ventricular ejection fraction (LVEF).

METHODS

121 consecutive patients with ESRD and normal LVEF and 30 consecutive normal controls were enrolled. Diastolic dyssynchrony parameters were calculated using 3-harmonic phase analysis. Systolic dyssynchrony parameters were calculated using the established 1-harmonic phase analysis.

RESULTS

The systolic and diastolic dyssynchrony parameters were correlated, but significantly different in both control and ESRD groups, indicating they were physiologically related but measured different LV mechanisms. The systolic and diastolic dyssynchrony parameters were each significantly different between the control and the ESRD groups. Significant systolic and diastolic dyssynchrony were found in 47% and 65% of the entire ESRD group.

CONCLUSION

Multi-harmonic phase analysis has been developed to assess diastolic dyssynchrony, which measured a new LV mechanism of regional function from gated SPECT MPI and showed a significantly higher prevalence rate than systolic dyssynchrony in patients with ESRD and normal LVEF.

Effects of physical exercise on cardiac dyssynchrony in patients with impaired left ventricular function

AIMS

The purpose of this study was to determine the effect of exercise on dyssynchrony in patients with left ventricular dysfunction.

METHODS AND RESULTS

Sixty patients with a left ventricular ejection fraction (LVEF) ≤ 35% were studied. Interventricular mechanical delay (IVMD), intraventricular mechanical delay [Ts-(lateral-septal)], and left ventricular filling ratio were measured at rest and during exercise. Significant IVMD was defined as a difference between aortic and pulmonary pre-ejection times of >40 ms. Intraventricular dyssynchrony was defined as a Ts-(lateral-septal) >65 ms. Forty-five patients with no dyssynchrony at rest were analysed (age 62 ± 14; LVEF 28 ± 6%) and compared with a control group of 15 patients with known dyssynchrony at rest. None of the 45 patients without dyssynchrony at rest developed dyssynchrony during exercise based on IVMD and Ts-(lateral-septal). In the control group, IVMD decreased from 65 ± 19 to 33 ± 11 ms (P< 0.001) during exercise, whereas Ts-(lateral-septal) did not change. Persistence of dyssynchrony during exercise (decrease of IVMD <60%) was significantly associated with response to cardiac resynchronization therapy (CRT). Whereas all 10 responders had persistent dyssynchrony during exercise, 4 of the 5 non-responders (80%) had an exercise-induced decrease of IVMD >60% (P< 0.004).

CONCLUSION

Exercise does not elicit mechanical dyssynchrony in patients without dyssynchrony at rest. In patients with significant dyssynchrony at rest, exercise-induced decrease of IVMD is common. Persistence of dyssynchrony during exercise might be a novel predictor of response to CRT.

Interventricular delay measurement using equilibrium radionuclide angiography before resynchronization therapy should be performed outside the area of segmental wall motion abnormalities

BACKGROUND

The aim of this study was to demonstrate that only mechanical dyssynchrony outside the area of segmental wall motion abnormalities (WMA) can be reduced by cardiac resynchronization therapy (CRT).

METHODS AND RESULTS

Included in the study were 28 consecutive patients with nonischaemic cardiomyopathy selected for CRT. Equilibrium radionuclide angiography (ERNA) was carried out before and after implantation of a multisite pacemaker. Patients were separated into two groups depending on the presence or absence of segmental WMA.

RESULTS

A reduction in QRS duration was observed in all patients after CRT. The interventricular delay (IVD) decreased significantly after CRT only in patients without WMA (homogeneous contraction, HG group; IVD 44 ± 11.4° vs. 17 ± 3.1°, p = 0.04). In contrast, no significant decrease was observed in patients with WMA (WMA group; IVD 51 ± 6° vs. 38 ± 6°, p NS). However, when dyssynchrony was considered outside the WMA area, a significant reduction in IVD was obtained, in the same range as in the HG group (IVD 32 ± 3° vs. 19 ± 3°, p = 0.04). In 9 of 15 patients (60%) with a reduction in IVD after CRT, the left ventricle ejection fraction (LVEF) increased by about +10%. In contrast, in 13 of 13 patients (100%) with no reduction in IVD, no modification of LVEF was obtained. In the presence of segmental WMA without significant delays outside the WMA area, no reduction in IVD was observed and LVEF did not increase (IVD 34 ± 5° before CRT vs. 37 ± 7° after CRT; LVEF 19 ± 4% before CRT vs. 22 ± 3% after CRT, p NS).

CONCLUSION

ERNA can be used to predict good mechanical resychronization (decrease in IVD) in patients after pacing. IVD has to be determined excluding the area of WMA in order to select patients who will show an increase in their left ventricle function after CRT.

Relation of right ventricular pacing site to left ventricular mechanical synchrony

Transvenous pacing leads are regularly placed in the right ventricular (RV) apex. Pediatric patients can develop myopathic changes after long-term RV apical pacing. Left ventricular (LV) mechanical dyssynchrony, estimated with echocardiography, may explain the acute decrease in LV function and long-term histopathologic changes. Ts-4w is an established echocardiographic measurement of LV synchrony, using tissue Doppler imaging (TDI). The purpose of this study was to determine whether TDI could identify acute changes in LV synchrony during pacing from different RV sites. We prospectively measured Ts-4w and Doppler-derived cardiac output after 5 minutes of pacing in 19 subjects undergoing catheter ablation. Each subject underwent pacing at 4 sites in random order: high right atrium, high RV septum (septal), RV outflow tract, and RV apex. Ts-4w was measured during sinus rhythm and each pacing protocol, with a value >65 ms defining mechanical dyssynchrony. Ts-4w during high right atrial (32.6 +/- 17.6 ms) and septal (28.9 +/- 10.9 ms) pacing were not different from sinus rhythm (39.5 +/- 15.5 ms). RV apex (85.7 +/- 18.4 ms) and RV outflow tract (84.2 +/- 20.4 ms) pacing induced mechanical dyssynchrony (p <0.0001). In conclusion, TDI demonstrated significant differences in LV synchrony related to pacing site. Ts-4w may be useful to determine ideal lead placement because it correlates with acutely improved hemodynamics.

Spontaneous remission of left bundle branch block immediately after denitrogenation with inhalation of 100% oxygen prior to anesthetic induction

Complete left bundle branch blocks have focused our attention, primarily because they are a sign predictive of mortality and a predictor of coexisting cardiovascular disease. Left bundle branch block (LBBB) is usually permanent but may occur transiently or intermittently. Spontaneous remission of LBBB rarely occurs during anesthesia. We present two patients in whom chronic LBBB reverted to normal sinus rhythm shortly following denitrogenation with inhalation of 100% oxygen during induction of anesthesia.

Morbidity and mortality in heart failure patients treated with cardiac resynchronization therapy: influence of pre-implantation characteristics on long-term outcome

AIMS

Cardiac resynchronization therapy (CRT) improves cardiac function, heart failure symptoms, and prognosis in selected patients. Many baseline characteristics associated with heart failure may influence prognosis after CRT. The objective of this study was to evaluate the effect of several baseline characteristics in relation to long-term prognosis in heart failure patients treated with CRT.

METHODS AND RESULTS

A total of 716 consecutive heart failure patients treated with CRT were included in an observational registry. All available data, including clinical and echocardiographic measurements, were analysed in relation to two endpoints: all-cause mortality and a combined endpoint of all-cause mortality or major cardiovascular event. Outcome data were collected by chart review, device interrogation, and telephone contact. Mean follow-up was 25 ± 19 months. During follow-up, 141 patients (20%) died (primary endpoint). Most of these patients (61%) died due to worsening heart failure. A total of 214 patients (30%) reached the secondary endpoint. Larger left ventricular end-systolic volume, less distance covered in the 6 min walking test, poor renal function, more severe heart failure, male gender, presence of atrial fibrillation, no posterolateral left ventricular (LV) lead, and no LV dyssynchrony were associated with poor prognosis after CRT.

CONCLUSION

In this large single-centre registry, several baseline clinical and echocardiographic characteristics were associated with prognosis after CRT. Worsening heart failure was the main cause of death in heart failure patients treated with CRT.