Prediction of response to cardiac resynchronization therapy by speckle tracking echocardiography using different software approaches

Multisite Left Ventricular Pacing in Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) is an established treatment of patients with heart failure with reduced ejection fraction and prolonged ventricular depolarization on surface electrocardiogram. Although patients' characteristics, such as their type of cardiomyopathy and the morphology and width of their baseline QRS complex, have been associated with CRT response, these features are not modifiable. Left ventricular multisite pacing has been proposed and tested as a tool to improve response to CRT and positively impact patient outcomes. This article reviews the published literature on left ventricular multisite pacing, with focus on the results of recently presented or published clinical trials.

Usefulness of Multisite Ventricular Pacing in Nonresponders to Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) is an established treatment for heart failure patients with myocardial dysfunction and delayed ventricular activation, but approximately 25% to 40% of patients do not respond to CRT. Left ventricular (LV) multisite pacing (MSP) has been proposed as a tool to improve CRT response. The goal of this study is to examine the safety and efficacy of LV MSP in CRT nonresponders. Between January 2018, and September 2019, the Strategic Management to Improve CRT Using Multi-Site Pacing trial prospectively enrolled 584 CRT-defibrillator recipients for established indications at 52 sites across the United States and evaluated their response at 6 months using the clinical composite score (CCS). Of the nonresponders, 102 patients had the LV MSP feature turned on and 78 patients completed the 12-month CCS evaluation. The LV MSP feature-related complication-free rate was 99.0% with a lower 95% confidence interval limit of 94.9%, which was higher than the performance goal of 90%. The proportion of nonresponders with an improved CCS from 6 to 12 months was 51.3% with a lower 95% confidence interval limit of 41.4%, which was higher than the performance goal of 5%. The estimated mean reduction in battery longevity with the LV MSP feature was about 3.6 months (estimated battery longevity of 8.87 ± 2.08 years at 6 months and 8.07 ± 2.23 years at 12 months). In conclusion, in CRT nonresponders, the use of the LV MSP feature is safe and associated with a ∼50% conversion rate with a small projected reduction in CRT-defibrillator battery longevity. LV MSP should be considered in the management of CRT nonresponders.

Myocardial Work by Echocardiography: Principles and Applications in Clinical Practice

Left ventricular (LV) global longitudinal strain (GLS) has established itself in the last decade as a reliable, more objective method for the evaluation of LV systolic function, able to detect subtle abnormalities in LV contraction even in the presence of preserved ejection fraction (EF). However, recent studies have demonstrated that GLS, similar to LV EF, has important load dependency. Non-invasive myocardial work (MW) quantification has emerged in the last years as an alternative tool for myocardial function assessment. This new method, incorporating measurement of strain and LV pressure, has shown to overcome GLS and LV EF limitations and provide a loading-independent evaluation of myocardial performance. The presence of a commercially available echocardiographic software for the non-invasive MW calculation has allowed the application of this new method in different settings. This review sought to provide an overview on the current knowledge of non-invasive MW estimation, showing its potential applications and possible added value in clinical practice.

Optimization of Chronic Cardiac Resynchronization Therapy Using Fusion Pacing Algorithm Improves Echocardiographic Response

Background

Whether reprogramming of cardiac resynchronization therapy (CRT) to increase electrical synchrony translates into echocardiographic improvement remains unclear. SyncAV is an algorithm that allows fusion of intrinsic conduction with biventricular pacing. We aimed to assess whether reprogramming chronically implanted CRT devices with SyncAV is associated with improved echocardiographic parameters.

Methods

Patients at a quaternary center with previously implanted CRT devices with a programmable SyncAV algorithm underwent routine electrocardiography-based SyncAV optimization during regular device clinic visits. This analysis included only patients who could be programmed to the SyncAV algorithm (i.e., in sinus rhythm with intrinsic atrioventricular conduction). Echocardiography was performed before and 6 months after CRT optimization.

Results

Of 64 consecutive, potentially eligible patients who underwent assessment, 34 who were able to undergo SyncAV programming were included. Their mean age was 74 ± 9 years, 41% were female, and 59% had ischemic cardiomyopathy. The mean time from CRT implant to SyncAV optimization was 17.8 ± 8.5 months. At 6-month follow-up, SyncAV optimization was associated with a significant increase in left ventricular ejection fraction (LVEF) (mean LVEF 36.5% ± 13.3% vs 30.9% ± 13.3%; P < 0.001) and a reduction in left ventricular end-systolic volume (LVESV) (mean LVESV 110.5 ± 57.5 mL vs 89.6 ± 52.4 mL; P < 0.001) compared with baseline existing CRT programming.

Conclusion

CRT reprogramming to maximize biventricular fusion pacing significantly increased LVEF and reduced LVESV in patients with chronic CRT devices. Further studies are needed to assess if a continuous fusion pacing algorithm improves long-term clinical outcomes and to identify which patients are most likely to derive benefit.

[Clinical Capabilities and Limitations in the Use of Modern Technologies in Echocardiography]

Transthoracic echocardiography is the most frequently used method for detection of impaired contractility of the left ventricle. In most cases, assessment of contractility is carried out visually "by eye", what increases its subjectivity, is operator-dependent in nature and requires a high level of clinical training and experience of the researcher. Currently in the arsenal of a specialist in echocardiography for quantification of left ventricular contractility sometimes is used tissue Doppler echocardiography, however, this method requires special settings of the image (high frame rate, the allocation of zones of interest), depends on the scanning angle and on operator qualification, has high intra - and inter-operator variability, and significantly increases the duration of the study. Therefore, this method has not received wide clinical application. In the 2000s years an innovative technique of speckle tracking emerged, which, unlike tissue Doppler echocardiography is efficient, does not burden a researcher with time costs, has a low intra - and inter- operator variability, does not depend on scan angle. In recent years, this technology is actively implemented in clinical practice for detection of subclinical impairment of the functional state of the myocardium in different diseases and syndromes: arterial hypertension, ischemic heart disease, valvular defects, and congenital heart disease, heart failure, cardiomyopathy of different etiology.

Physiological basis in the assessment of myocardial mechanics using speckle-tracking echocardiography 2D. Part II

In this paper, the authors attempt to concisely present the anatomical and pathophysiological bases as well as the principles for echocardiographic evaluation of mechanical aspects of cardiac function based on speckle tracking method. This technique uses a phenomenon involving the formation of characteristic image units, referred to as speckles or acoustic markers, which are stable during cardiac cycle, on a two-dimensional echocardiographic picture. Changes in the position of these speckles throughout the cardiac cycle, which are monitored and analyzed semi-automatically by a computer system, reflect deformation of both, cardiac ventricle as a whole as well as its individual anatomical segments. The values of strain and the strain rate, as well as the range and velocity of the movement of these markers, which are in close relationship with multiple hemodynamic parameters, can be visualized as various types of charts – linear, two- and three-dimensional – as well as numerical values, enabling deeper insight into the mechanical and hemodynamic aspects of cardiac function in health and disease. The use of information obtained based on speckle tracking echocardiography allows to understand previously unclear mechanisms of physiological and pathophysiological processes. The first part of the study discusses the formation of a two-dimensional ultrasound image and the speckles, as well as the technical aspects of tracking their movement. The second part presents in more detail the methodology of speckle-tracking echocardiography, the characteristic abnormalities of cardiac mechanics presenting in different clinical entities, and the limitations related to given clinical and technical issues.

Is speckle tracking actually helpful for cardiac resynchronization therapy?

What is the specific role of echocardiography in cardiac resynchronization therapy (CRT)? CRT has proven to be highly effective for improving symptoms and survival of patients with advanced heart failure (HF) and wide QRS. However, a significant minority of patients do not respond favorably to CRT on the basis of standard clinical selection criteria, including the electrocardiographic QRS width. Subsequently, echocardiographic assessment of left ventricular (LV) dyssynchrony has been considered useful for CRT for selected responders, but findings by multicenter studies suggest that its predictive value was not sufficiently robust to replace routine selection criteria for CRT. A more recent approach, however, using speckle-tracking echocardiography yields more accurate quantification of regional wall contraction. Speckle-tracking approaches have therefore generated a great deal of interest about their clinical applications for CRT. Although reports on speckle tracking have not been included in any recommendations as to whether patients should undergo CRT based on the current guidelines, speckle tracking can play an important supplementary part in CRT on the basis of a case-by-case clinical decision for challenging cases. Here, we review the strengths of speckle-tracking methods, and their current potential for clinical use in CRT.

Global longitudinal strain and global circumferential strain by speckle-tracking echocardiography and feature-tracking cardiac magnetic resonance imaging: comparison with left ventricular ejection fraction

BACKGROUND

Left ventricular (LV) ejection fraction (EF) is a routine clinical standard to assess cardiac function. Global longitudinal strain (GLS) and global circumferential strain (GCS) have emerged as important LV functional measures. The objective of this study was to determine the relationships of GLS and GCS by speckle-tracking echocardiography and featuring-tracking cardiac magnetic resonance (CMR) to CMR EF as a standard of reference in the same patients.

METHODS

A total of 73 consecutive patients aged 55 ± 15 years clinically referred for both CMR and echocardiography (EF range, 8%-78%) were studied. Routine steady-state free precession CMR images were prospectively analyzed offline using feature-tracking software for LV GLS, GCS, volumes, and EF. GLS was averaged from three standard longitudinal views and GCS from the mid-LV short-axis plane. Echocardiographic speckle-tracking was used from the similar imaging planes for GLS, GCS, LV volumes, and EF.

RESULTS

Feature-tracking CMR strain was closely correlated with speckle-tracking strain in the same patients: GLS, r = -0.87; GCS, r = -0.92 (P < .0001). End-diastolic and end-systolic volumes and EF by feature-tracking CMR were significantly correlated with standard manual tracing of multiple CMR short-axis images (r = 0.97, r = 0.98, and r = 0.97, P < .0001 for all). GLS and GCS by echocardiography and CMR feature-tracking were closely correlated with standard CMR EF: r = -0.85 and r = -0.95, respectively (P < .001). Global strain measures (in absolute values) were correlated with EF using the formula EF = 3(GLS) + 8% or EF = 2.5(GCS) + 8%.

CONCLUSIONS

GLS and GCS by feature-tracking CMR analysis was a rapid means to obtain myocardial strain similar to speckle-tracking echocardiography. GLS and GCS were closely correlated with CMR EF in this patient series and may play a role in the clinical assessment of LV function.

Easy-to-use comprehensive speckle-tracking approach for cardiac resynchronization therapy

BACKGROUND

Left ventricular (LV) dyssynchrony has emerged as an important mechanism contributing to the patient's response to cardiac resynchronization therapy (CRT), but other potential factors, especially LV myocardial viability, are also influential. METHODS AND RESULTS: We studied 132 patients undergoing CRT. LV dyssynchrony was determined by anteroseptal-to-posterior wall delay on the mid-LV short-axis view using 2-dimensional speckle-tracking radial strain (≥130 ms as significant). Global circumferential strain (GCS), considered as a parameter of LV intrinsic myocardial function, was also determined as the peak GCS from the same view. Long-term follow-up was tracked over 40 months. Kaplan-Meier analysis indicated that patients with GCS >3.9% experienced fewer cardiovascular events overall (log-rank P=0.034). Similarly, patients with GCS >3.9% and ≥6.6% experienced fewer cardiovascular events than those with GCS ≤3.9% and <6.6% among patients with and without LV dyssynchrony (log-rank P=0.025 and P=0.029, respectively). An important finding from multivariate Cox proportional hazards analysis was that LV dyssynchrony and GCS were independently associated with cardiovascular events. Of note, only 2±1 min per patient were needed to analyze both LV dyssynchrony and GCS from the same routine mid-LV short-axis view.

CONCLUSIONS

This easy-to-use combined assessment of LV dyssynchrony and myocardial function using speckle-tracking strain from the same mid-LV short-axis view may well have clinical implications for CRT.

Feature tracking measurement of dyssynchrony from cardiovascular magnetic resonance cine acquisitions: comparison with echocardiographic speckle tracking

BACKGROUND

Analysis of left ventricular (LV) mechanical dyssynchrony may provide incremental prognostic information regarding cardiac resynchronization therapy (CRT) response in addition to QRS width alone. Our objective was to quantify LV dyssynchrony using feature tracking post processing of routine cardiovascular magnetic resonance (CMR) cine acquisitions (FT-CMR) in comparison to speckle tracking echocardiography.

METHODS

We studied 72 consecutive patients who had both steady-state free precession CMR and echocardiography. Mid-LV short axis CMR cines were analyzed using FT-CMR software and compared with echocardiographic speckle tracking radial dyssynchrony (time difference between the anteroseptal and posterior wall peak strain).

RESULTS

Radial dyssynchrony analysis was possible by FT-CMR in all patients, and in 67 (93%) by echocardiography. Dyssynchrony by FT-CMR and speckle tracking showed limits of agreement of strain delays of ± 84 ms. These were large (up to 100% or more) relative to the small mean delays measured in more synchronous patients, but acceptable (mainly <25%) in those with mean delays of >200 ms. Radial dyssynchrony was significantly greater in wide QRS patients than narrow QRS patients by both FT-CMR (radial strain delay 230 ± 94 vs. 77 ± 92* ms) and speckle tracking (radial strain delay 242 ± 101 vs. 75 ± 88* ms, all *p < 0.001).

CONCLUSIONS

FT-CMR delivered measurements of radial dyssynchrony from CMR cine acquisitions which, at least for the patients with more marked dyssynchrony, showed reasonable agreement with those from speckle tracking echocardiography. The clinical usefulness of the method, for example in predicting prognosis in CRT patients, remains to be investigated.

Early echocardiographic deformation analysis for the prediction of sudden cardiac death and life-threatening arrhythmias after myocardial infarction

OBJECTIVES

This study sought to hypothesize that global longitudinal strain (GLS) as a measure of infarct size, and mechanical dispersion (MD) as a measure of myocardial deformation heterogeneity, would be of incremental importance for the prediction of sudden cardiac death (SCD) or malignant ventricular arrhythmias (VA) after acute myocardial infarction (MI).

BACKGROUND

SCD after acute MI is a rare but potentially preventable late complication predominantly caused by malignant VA. Novel echocardiographic parameters such as GLS and MD have previously been shown to identify patients with chronic ischemic heart failure at increased risk for arrhythmic events. Risk prediction during admission for acute MI is important because a majority of SCD events occur in the early period after hospital discharge.

METHODS

We prospectively included patients with acute MI and performed echocardiography, with measurements of GLS and MD defined as the standard deviation of time to peak negative strain in all myocardial segments. The primary composite endpoint (SCD, admission with VA, or appropriate therapy from a primary prophylactic implantable cardioverter-defibrillator [ICD]) was analyzed with Cox models.

RESULTS

A total of 988 patients (mean age: 62.6 ± 12.1 years; 72% male) were included, of whom 34 (3.4%) experienced the primary composite outcome (median follow-up: 29.7 months). GLS (hazard ratio [HR]: 1.38; 95% confidence interval [CI]: 1.25 to 1.53; p < 0.0001) and MD (HR/10 ms: 1.38; 95% CI: 1.24 to 1.55; p < 0.0001) were significantly related to the primary endpoint.

GLS (HR

1.24; 95% CI: 1.10 to 1.40; p = 0.0004) and MD (HR/10 ms: 1.15; 95% CI: 1.01 to 1.31; p = 0.0320) remained independently prognostic after multivariate adjustment. Integrated diagnostic improvement (IDI) and net reclassification index (NRI) were significant for the addition of GLS (IDI: 4.4% [p < 0.05]; NRI: 29.6% [p < 0.05]), whereas MD did not improve risk reclassification when GLS was known.

CONCLUSIONS

Both GLS and MD were significantly and independently related to SCD/VA in these patients with acute MI and, in particular, GLS improved risk stratification above and beyond existing risk factors.

Utility of combined assessment of baseline dyssynchrony and its acute improvement to predict long-term outcomes after cardiac resynchronization therapy

Although left ventricular (LV) mechanical dyssynchrony can predict the response to cardiac resynchronization therapy (CRT), the presence of baseline LV dyssynchrony might not be the only determinant of the response to CRT. The objectives of the present study were to test the hypothesis that a combined assessment of baseline LV dyssynchrony and its acute improvement can produce a more accurate prediction of the long-term outcomes after CRT. We studied 121 patients with heart failure undergoing CRT. LV dyssynchrony was determined by measuring the anteroseptal-to-posterior wall time delay using the speckle-tracking radial strain (≥130 ms was predefined as significant) and was assessed at baseline and 7 ± 3 days after CRT. Long-term unfavorable outcome events were tracked for 5 years. Acute improvement in LV dyssynchrony of ≥33% was predictive of the long-term outcome with an area under the curve of 0.67 (p = 0.0024). Using this cutoff value, the Kaplan-Meier curve showed that patients with acute improvement in LV dyssynchrony experienced fewer cardiovascular events than those without (log-rank p = 0.0002). The event-free survival of patients whose baseline LV dyssynchrony was ≥130 ms and whose acute improvement in LV dyssynchrony was ≥33% was greater than that of the patients with baseline LV dyssynchrony of ≥130 ms but with acute improvement in LV dyssynchrony of <33% (88% vs 65%, p = 0.012). In conclusion, the combined assessment of baseline LV dyssynchrony and its acute improvement after CRT produced a more accurate prediction of long-term outcomes after CRT.

Low-dose dobutamine test associated with interventricular dyssynchrony: a useful tool to identify cardiac resynchronization therapy responders: data from the LOw dose DObutamine stress-echo test in Cardiac Resynchronization Therapy (LODO-CRT) phase 2 study

BACKGROUND

Cardiac resynchronization therapy (CRT) is effective in patients with heart failure, but 30% to 50% of subjects are classified as nonresponders. Identifying responders remains a challenging task.

AIMS

The LODO-CRT trial investigated the association between left ventricular contractile reserve (LVCR) and clinical and echocardiographic long-term CRT response.

METHODS

This is a multicenter, prospective, observational study. Left ventricular contractile reserve was detected using a dobutamine stress echocardiography test, defined as an ejection fraction increase of >5 points. Clinical CRT response was defined as the absence of major cardiovascular events (ie, cardiovascular death or heart failure hospitalization). Echocardiographic response was defined as a left ventricle end-systolic volume reduction of >10%.

RESULTS

A total of 221 CRT-indicated patients were studied (80% presented LVCR). During a mean follow-up of 15 ± 5 months, 17 patients died and 16 were hospitalized due to heart failure. The proportion of clinical responders was 155 (88%) of 177 and 33 (75%) of 44 (P = .036) in the groups with and without LVCR, respectively. Kaplan-Meier analysis showed a significant difference in cardiac survival/hospitalization between patients with and without LVCR. The proportion of echocardiographic responders was 144 (87%) of 166 and 16 (42%) of 38 in the groups with and without LVCR (P < .001), respectively; LVCR showed 90% sensitivity and 87% positive predictive value to prefigure echocardiographic CRT responders. Multivariable analysis identified LVCR and interventricular dyssynchrony as independent predictors of CRT response. The concomitant presence of both factors showed 99% specificity and 83% sensitivity in detecting responders.

CONCLUSION

The presence of LVCR helps in predicting a clinical and echocardiographic CRT response. Concomitant assessment of LVCR and interventricular dyssynchrony accurately stratifies responder and nonresponder patients.

A practical approach to imaging dyssynchrony for cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is believed to benefit patients by primarily correcting heterogeneity in regional ventricular mechanical contraction, known as dyssynchrony. Although many symptomatic heart failure patients with depressed left ventricular ejection fraction and widened electrocardiographic QRS complexes have clinical improvement from CRT, a significant subset of approximately one-third do not seem to respond. Because the degree of mechanical dyssynchrony may be widely variable, interest has remained high to attempt to improve patient selection for CRT using cardiac imaging as a means to quantify dyssynchrony. This article will review the principal echocardiographic methods of dyssynchrony analysis by tissue Doppler imaging, (opposing wall delay, 12-site standard deviation or Yu index, and longitudinal strain), routine pulsed-Doppler (interventricular mechanical delay, pre-ejection delay and filling time ratio), and speckle tracking (including radial, circumferential, and longitudinal strain). In addition, dyssynchrony analysis by cardiac magnetic resonance imaging is introduced as a potential alternative technique. The technical features, strengths and limitations, and clinical evidence for these methods are discussed, including a practical clinical approach.

Echocardiographic assessment of myocardial strain

Echocardiographic strain imaging, also known as deformation imaging, has been developed as a means to objectively quantify regional myocardial function. First introduced as post-processing of tissue Doppler imaging velocity converted to strain and strain rate, strain imaging has more recently also been derived from digital speckle tracking analysis. Strain imaging has been used to gain greater understanding into the pathophysiology of cardiac ischemia and infarction, primary diseases of the myocardium, and the effects of valvular disease on myocardial function, and to advance our understanding of diastolic function. Strain imaging has also been used to quantify abnormalities in the timing of mechanical activation for heart failure patients undergoing cardiac resynchronization pacing therapy. Further advances, such as 3-dimensional speckle tracking strain imaging, have emerged to provide even greater insight. Strain imaging has become established as a robust research tool and has great potential to play many roles in routine clinical practice to advance the care of the cardiovascular patient. This perspective reviews the physiology of myocardial strain, the technical features of strain imaging using tissue Doppler imaging and speckle tracking, their strengths and weaknesses, and the state-of-the-art present and potential future clinical applications.

Left ventricular mechanical dyssynchrony in acute onset cardiomyopathy: association of its resolution with improvements in ventricular function

OBJECTIVES

The purpose of this study was to evaluate mechanical dyssynchrony in patients with acute onset cardiomyopathy with narrow QRS interval, and its association with improvements in left ventricular (LV) function.

BACKGROUND

LV dyssynchrony has been usually studied in patients with chronic heart failure and wide QRS in the context of cardiac resynchronization therapy.

METHODS

We studied 201 patients enrolled in the IMAC-2 (Inflammatory Mediators in Acute Cardiomyopathy) trial with recent onset nonischemic cardiomyopathy and ejection fraction <40%. Dyssynchrony was assessed using speckle-tracking velocity vector imaging. Diastolic function was assessed by mitral inflow E and mitral E' annular velocities (E/E'). A normal control group of 15 normal volunteers was studied for comparison.

RESULTS

Although mean QRS was narrow (98 ± 21 ms), 108 (54%) acute cardiomyopathy patients had significant LV dyssynchrony at presentation: opposing wall delay 89 ± 51 ms, versus 35 ± 11 ms in controls, and 12-site standard deviation 43 ± 23, versus 24 ± 8 ms in controls (p < 0.001). Patients with dyssynchrony had greater degrees of diastolic dysfunction: E/E' 15 ± 8 versus 12 ± 6 (p < 0.05). At 6 months, group mean ejection fraction improved from 23 ± 8% to 40 ± 12% and E/E' improved from 14 ± 7 to 9 ± 5 (both p < 0.001). Dyssynchrony improved from 89 ± 51 ms to 52 ± 35 ms in maximum opposing wall delay, and 43 ± 23 ms to 32 ± 19 ms in 12-site standard deviation, and the prevalence of dyssynchrony decreased to 12% after 6 months (p < 0.001 vs. baseline).

CONCLUSIONS

Mechanical dyssynchrony was observed in a significant number of patients with acute onset cardiomyopathy, despite having a narrow QRS interval. Resolution of dyssynchrony associated with improvements in LV function occurred in the large majority of these patients.

Strain dyssynchrony index determined by three-dimensional speckle area tracking can predict response to cardiac resynchronization therapy

BACKGROUND

We have previously reported strain dyssynchrony index assessed by two-dimensional speckle tracking strain, and a marker of both dyssynchrony and residual myocardial contractility, can predict response to cardiac resynchronization therapy (CRT). A newly developed three-dimensional (3-D) speckle tracking system can quantify endocardial area change ratio (area strain), which coupled with the factors of both longitudinal and circumferential strain, from all 16 standard left ventricular (LV) segments using complete 3-D pyramidal datasets. Our objective was to test the hypothesis that strain dyssynchrony index using area tracking (ASDI) can quantify dyssynchrony and predict response to CRT.

METHODS

We studied 14 heart failure patients with ejection fraction of 27 ± 7% (all≤35%) and QRS duration of 172 ± 30 ms (all≥120 ms) who underwent CRT. Echocardiography was performed before and 6-month after CRT. ASDI was calculated as the average difference between peak and end-systolic area strain of LV endocardium obtained from 3-D speckle tracking imaging using 16 segments. Conventional dyssynchrony measures were assessed by interventricular mechanical delay, Yu Index, and two-dimensional radial dyssynchrony by speckle-tracking strain. Response was defined as a ≥15% decrease in LV end-systolic volume 6-month after CRT.

RESULTS

ASDI ≥ 3.8% was the best predictor of response to CRT with a sensitivity of 78%, specificity of 100% and area under the curve (AUC) of 0.93 (p < 0.001). Two-dimensional radial dyssynchrony determined by speckle-tracking strain was also predictive of response to CRT with an AUC of 0.82 (p < 0.005). Interestingly, ASDI ≥ 3.8% was associated with the highest incidence of echocardiographic improvement after CRT with a response rate of 100% (7/7), and baseline ASDI correlated with reduction of LV end-systolic volume following CRT (r = 0.80, p < 0.001).

CONCLUSIONS

ASDI can predict responders and LV reverse remodeling following CRT. This novel index using the 3-D speckle tracking system, which shows circumferential and longitudinal LV dyssynchrony and residual endocardial contractility, may thus have clinical significance for CRT patients.

Utility of comprehensive assessment of strain dyssynchrony index by speckle tracking imaging for predicting response to cardiac resynchronization therapy

The strain delay index is reportedly a marker of dyssynchrony and residual myocardial contractility. The aim of this study was to test the hypothesis that a relatively simple version of the strain dyssynchrony index (SDI) can predict response to cardiac resynchronization therapy (CRT) and that combining assessment of radial, circumferential, and longitudinal SDI can further improve the prediction of responders. A total of 52 patients who underwent CRT were studied. The SDI was calculated as the average difference between peak and end-systolic strain from 6 segments for radial and circumferential SDI and 18 segments for longitudinal SDI. Conventional dyssynchrony measures were assessed by interventricular mechanical delay, the Yu index, and radial dyssynchrony by speckle tracking strain. Response was defined as a ≥15% decrease in end-systolic volume after 3 months. Of the individual parameters, radial SDI ≥6.5% was the best predictor of response to CRT, with sensitivity of 81%, specificity of 81%, and an area under the curve of 0.87 (p <0.001). Circumferential SDI ≥3.2% and longitudinal SDI ≥3.6% were also found to be predictive of response to CRT, with areas under the curve of 0.81 and 0.80, respectively (p <0.001). Moreover, radial, circumferential, and longitudinal SDI at baseline were correlated with reduction of end-systolic volume with CRT. In addition, the response rate in patients with 3 positive SDIs was 100%. In contrast, rates in patients with either 1 or no positive SDIs were 42% and 22%, respectively (p <0.005 and p <0.001 vs 3 positive SDIs). In conclusion, the SDI can successfully predict response to CRT, and the combined approach leads to more accurate prediction than using individual parameters.

Speckle-tracking echocardiography: a new technique for assessing myocardial function

Speckle-tracking echocardiography has recently emerged as a quantitative ultrasound technique for accurately evaluating myocardial function by analyzing the motion of speckles identified on routine 2-dimensional sonograms. It provides non-Doppler, angle-independent, and objective quantification of myocardial deformation and left ventricular systolic and diastolic dynamics. By tracking the displacement of the speckles during the cardiac cycle, strain and the strain rate can be rapidly measured offline after adequate image acquisition. Data regarding the feasibility, accuracy, and clinical applications of speckle-tracking echocardiography are rapidly accumulating. This review describes the fundamental concepts of speckle-tracking echocardiography, illustrates how to obtain strain measurements using this technique, and discusses their recognized and developing clinical applications.

Relationship of echocardiographic dyssynchrony to long-term survival after cardiac resynchronization therapy

BACKGROUND

The ability of echocardiographic dyssynchrony to predict response to cardiac resynchronization therapy (CRT) has been unclear.

METHODS AND RESULTS

A prospective, longitudinal study was designed with predefined dyssynchrony indexes and outcome variables to test the hypothesis that baseline dyssynchrony is associated with long-term survival after CRT. We studied 229 consecutive class III to IV heart failure patients with ejection fraction ≤35 and QRS duration ≥120 milliseconds for CRT. Dyssynchrony before CRT was defined as tissue Doppler velocity opposing-wall delay ≥65 milliseconds, 12-site SD (Yu Index) ≥32 milliseconds, speckle tracking radial strain anteroseptal-to-posterior wall delay ≥130 milliseconds, or pulsed Doppler interventricular mechanical delay ≥40 milliseconds. Outcome was defined as freedom from death, heart transplantation, or left ventricular assist device implantation. Of 210 patients (89) with dyssynchrony data available, there were 62 events: 47 deaths, 9 transplantations, and 6 left ventricular assist device implantations over 4 years. Event-free survival was associated with Yu Index (P=0.003), speckle tracking radial strain (P=0.003), and interventricular mechanical delay (P=0.019). When adjusted for confounding baseline variables of ischemic origin and QRS duration, Yu Index and radial strain dyssynchrony remained independently associated with outcome (P<0.05). Lack of radial dyssynchrony was particularly associated with unfavorable outcome in those with QRS duration of 120 to 150 milliseconds (P=0.002).

CONCLUSIONS

The absence of echocardiographic dyssynchrony was associated with significantly less favorable event-free survival after CRT. Patients with narrower QRS duration who lacked dyssynchrony had the least favorable long-term outcome. These observations support the relationship of dyssynchrony and CRT response.

Impact of scar burden by single-photon emission computed tomography myocardial perfusion imaging on patient outcomes following cardiac resynchronization therapy

AIMS

Ischaemic heart disease negatively impacts response to cardiac resynchronization therapy (CRT), yet the impact of infarct scar burden on clinical outcomes and its interaction with mechanical dyssynchrony have not been well described.

METHODS AND RESULTS

We studied 620 NYHA classes III-IV heart failure patients with ejection fraction (EF) ≤ 35% and QRS duration ≥120 ms referred for CRT. Included were 190 ischaemic cardiomyopathy (ICM) CRT recipients with scar burden quantified by rest-redistribution Tl(201) myocardial perfusion imaging using a 17-segment (0 = normal to 4 = absence of uptake) summed rest score (SRS). Non-ICM (NICM) CRT recipients (n = 380) and 50 patients referred for CRT with unsuccessful LV lead implant comprised the comparison groups. Echocardiographic dyssynchrony analysis was performed in a subgroup of 150 patients. Follow-up left ventricular EF (LVEF) and volumes were examined at 7 ± 3 months in 143 patients. The outcome of death, cardiac transplant, or mechanical circulatory support was assessed in all. Over 2.1 ± 1.6 years, ICM patients had significantly worse survival and less LVEF improvement than NICM patients (P < 0.01). Ischaemic cardiomyopathy patients with low scar burden (SRS < 27) had favourable survival and LVEF improvement, similar to NICM patients. A high scar burden (SRS ≥ 27) was associated with reduced survival and lack of LV functional improvement (P ≤ 0.01), similar to those with unsuccessful LV lead implant, whereas baseline dyssynchrony was not predictive of outcome in these patients.

CONCLUSION

Extensive scar burden in ICM patients unfavourably affected clinical and LV functional outcomes after CRT, regardless of baseline dyssynchrony measures. Patients with ICM and lower scar burden had significantly better outcomes, similar to NICM patients.

Measurement of right ventricular mechanical synchrony in children using tissue Doppler velocity and two-dimensional strain imaging

BACKGROUND

Right ventricular (RV) mechanical dyssynchrony may be associated with RV dysfunction. The aim of this study was to investigate the feasibility of measuring RV synchrony in normal children using Doppler tissue imaging and two-dimensional speckle tracking.

METHODS

The RV delay (difference in time to peak velocity or two-dimensional strain between the RV lateral wall and the interventricular septum) and standard deviation of time to peak velocity or strain were measured and corrected for heart rate. Intraobserver and interobserver reliabilities were analyzed.

RESULTS

One hundred three children were studied. RV delay analysis was feasible in 95% by Doppler tissue imaging and in 63% by two-dimensional speckle tracking (99% and 84% when imaging was adequate). The mean ± 2 standard deviations RV delay by either method was <70 msec or <8% of the cardiac cycle in systole and <65 msec or <7% of the cardiac cycle in diastole. Intraobserver and interobserver variability showed small absolute differences but high variability because delays were either positive or negative.

CONCLUSION

This study establishes the feasibility of the measurement of RV mechanical synchrony in normal children aged 3 to 18 years.

Comparative mechanical activation mapping of RV pacing to LBBB by 2D and 3D speckle tracking and association with response to resynchronization therapy

OBJECTIVES

The goals of this study were to compare patterns of mechanical activation in patients with chronic right ventricular (RV) pacing with those with left bundle branch block (LBBB) using 2-dimensional and novel 3-dimensional speckle tracking, and to compare ejection fraction (EF) response and long-term survival after cardiac resynchronization therapy (CRT).

BACKGROUND

Several randomized CRT trials have excluded patients with chronic RV pacing, and current guidelines for CRT include patients with intrinsically widened QRS, typically LBBB.

METHODS

We studied 308 patients who were referred for CRT: 227 had LBBB, 81 were RV paced. Dyssynchrony was assessed by tissue Doppler, routine pulsed Doppler, and 2-dimensional speckle-tracking radial strain. 3D strain was assessed using speckle tracking from a pyramidal dataset in a subset of 57 patients for mechanical activation mapping. Survival after CRT was compared with survival in a group of 46 patients with attempted, but failed, CRT.

RESULTS

Patients with chronic RV pacing and LBBB had similar intraventricular dyssynchrony, with opposing wall delays by tissue Doppler of 82 +/- 45 ms versus 87 +/- 63 ms and anteroseptum-to-posterior delays by speckle tracking of 225 +/- 142 ms, versus 211 +/- 107 ms, respectively. RV-paced patients, however, had greater interventricular dyssynchrony: 44 +/- 24 ms versus 35 +/- 21 ms (p < 0.01), which correlated with their greater QRS duration (p < 0.001). Sites of latest mechanical activation were most often posterior or lateral in both groups, but RV-paced patients had sites of earliest activation more often from the inferior-septum and apex (p < 0.05). EF response was similar in RV-paced and LBBB groups, and survival free from transplantation or mechanical support after CRT was similarly favorable as compared with failed CRT patients over 5 years (p < 0.01).

CONCLUSIONS

RV-paced patients, when compared with LBBB patients, had similar dyssynchronous patterns of mechanical activation and greater interventricular dyssynchrony. Importantly, RV-paced patients had similar EF response and long-term outcome as those with LBBB, which supports their candidacy for CRT.

Echocardiography, dyssynchrony, and the response to cardiac resynchronization therapy

Biventricular pacing or cardiac resynchronization therapy (CRT) has been a considerable advance in the therapy of chronic heart failure. However, it is clear that not all patients benefit either in terms of symptoms or cardiac function, and some may be worsened by CRT. In this review, we consider the arguments, both clinical and economical, in favour of improved selection of patients for CRT other than those in current guidelines. It also seems clear that the fundamental mechanism of CRT is correction of dyssynchrony, and we review the various methodologies available to detect dyssynchrony. Other factors are probably also important in determining outcomes such as lead position, the extent and form of myocardial damage, optimizing pacemaker performance, and clinical expertise. The potential costs of inappropriate CRT implantation are high to our patients and to the health economy, and it behooves the cardiology community to develop better selection criteria. The current guidelines can and should be improved.

Dyssynchrony by speckle-tracking echocardiography and response to cardiac resynchronization therapy: results of the Speckle Tracking and Resynchronization (STAR) study

Aims

The Speckle Tracking and Resynchronization (STAR) study used a prospective multi-centre design to test the hypothesis that speckle-tracking echocardiography can predict response to cardiac resynchronization therapy (CRT).

Methods and results

We studied 132 consecutive CRT patients with class III and IV heart failure, ejection fraction (EF) ≤35%, and QRS ≥120 ms from three international centres. Baseline dyssynchrony was evaluated by four speckle tracking strain methods; radial, circumferential, transverse, and longitudinal (≥130 ms opposing wall delay for each). Pre-specified outcome variables were EF response and three serious long-term events: death, transplant, or left ventricular assist device. Of 120 patients (91%) with baseline dyssynchrony data, both short-axis radial strain and transverse strain from apical views were associated with favourable EF response 7 ± 4 months and long-term outcome over 3.5 years (P < 0.01). Radial strain had the highest sensitivity at 86% for predicting EF response with a specificity of 67%. Serious long-term unfavourable events occurred in 20 patients after CRT, and happened three times more frequently in those who lacked baseline radial or transverse dyssynchrony than in patients with dyssynchrony (P < 0.01). Patients who lacked both radial and transverse dyssynchrony had unfavourable clinical events occur in 53%, in contrast to events occurring in 12% if baseline dyssynchrony was present (P < 0.01). Circumferential and longitudinal strains predicted response when dyssynchrony was detected, but failed to identify dyssynchrony in one-third of patients who responded to CRT.

Conclusion

Dyssynchrony by speckle-tracking echocardiography using radial and transverse strains is associated with EF response and long-term outcome following CRT.

Dynamic and site-specific impact of ventricular pacing on left ventricular ejection fraction

BACKGROUND

Some studies suggest that right ventricular (RV) pacing has an adverse impact on left ventricular ejection fraction (LVEF), particularly in subjects with preexisting left ventricular (LV) dysfunction, and that direct LV pacing may be relatively protective. Interactions between pacing site and LVEF remain unclear.

OBJECTIVE

The purpose of this study was to examine the relative impact of RV and LV pacing on LVEF by serial study during a period in which LV dysfunction, induced by tachypacing, was introduced and then resolved.

METHODS

In each of five dogs, RV, LV, and simultaneous RV and LV (BiV) pacing modes were compared to native ventricular activation (1) prior to tachypacing (baseline), (2) weekly during a 5-week continuous tachypacing period, and (3) weekly during a 3-week post-tachypacing recovery period. At each evaluation, LVEF and LV contraction synchrony were assessed during each pacing mode.

RESULTS

The decrease in LVEF during the tachypacing period was more pronounced during RV pacing than during native activation or LV or BiV pacing. The magnitude of this effect correlated with a diminishment in LV contraction synchrony that was not observed during native activation or LV or BiV pacing. During the post-tachypacing period, gradual reversal of these changes toward baseline was observed.

CONCLUSION

Compared to native activation, RV pacing worsens LVEF in a manner proportional to the severity of preexisting LV dysfunction, attributable to reduced LV contraction synchrony. In comparison, both LV and BiV pacing preserve LVEF and contraction synchrony.