Mechanical Dyssynchrony Indices Research Articles

Association of cardiac mechanical dyssynchrony indices with data of dynamic single-photon emission computed tomography of the myocardium: the role of the time interval between the stress test and recording

Introduction. According to ECG-synchronized myocardial perfusion imaging (MPI) mechanical dyssynchrony (MD) is a sensitive marker of impaired myocardial perfusion. However, its direct comparison with indicators of myocardial blood flow reserve (MFR) according to single-photon emission computed tomography (SPECT) was not carried out. Traditional MPI protocols imply a long gap between stress test and image acquisition, during which stress-induced changes may pass. It is potentially possible to reduce the time interval down to 5 minutes.Aim: To investigate the relationship between early and delayed MD indices and the data of MFR by means of SPECT.Material and Methods. The study included 20 patients with suspected coronary heart disease, preserved left ventricular ejection fraction (> 55%) and without obstructive coronary artery lesions (< 50%) according to multislice computed coronary angiography. All patients underwent dynamic SPECT (dSPECT) according to a two-day rest/stress protocol. Gated MPI was performed 60 minutes after radiopharmaceutical administration. Myocardial blood flow and reserve, as well as phase histogram standard deviation (PSD, degree) and phase histogram bandwidth (HBW, degree) from 5 minutes after radiopharmaceutical administration were obtained from the dSPECT data by postprocessing. Perfusion data as well as MD indices (PSD, HBW) were obtained from delayed images. Based on dSPECT data, patients were divided into 2 groups: with preserved (MFR ≥ 2.0) and reduced (MFR < 2.0) myocardial blood flow reserve.Results. Correlation analysis showed that MD indices on stress test in early scan had a stronger association with MFR (PSD ρ = –0.68, p < 0.001; HBW ρ = –0.68, p = 0.001) compared to those in delayed scan (PSD ρ = –0.38, p = 0.019; HBW ρ = –0.44, p = 0.005). According to multivariate regression analysis, PSD on stress test at early scan was the only independent predictor of reduced MFR (OR 1.29 (1.1; 1.53)). Stress PSD > 22° obtained at early scanning had a sensitivity of 81% and specificity of 87% (AUC = 0.86, p < 0.001) in predicting of reduced MFR.Conclusion. Left ventricular mechanical dyssynchrony indices obtained by early post-stress gated MPI have a stronger association with myocardial blood flow reserve indices.

Prognostic value of left ventricular mechanical dyssynchrony indices derived from gated myocardial perfusion SPECT in coronary artery disease: a systematic review and meta-analysis.

Left ventricular mechanical dyssynchrony (LVMD) is an important prognostic factor in coronary artery disease. A growing body of evidence indicates that LVMD parameters derived from phase analysis of gated myocardial SPECT may allow risk stratification for future cardiac events. We performed a systematic review and meta-analysis on the prognostic value of LVMD on gated SPECT in patients with coronary artery disease. PubMed, Embase, and the Cochrane library were searched until August 25, 2022, for studies reporting the prognostic value of LVMD on gated SPECT for outcomes of all-cause death, cardiac death, or major adverse cardiovascular event (MACE) in patients with coronary artery disease. Hazard ratios (HRs) and their 95% confidence intervals (CIs) were meta-analytically pooled using a random-effects model. Nine studies (26,750 patients) were included in a qualitative synthesis. Among the SPECT LVMD parameters used in various studies, high phase standard deviation, phase bandwidth, and phase entropy were widely evaluated and reported to be associated with high rates of all-cause death, cardiac death, or MACE. For five studies (23,973 patients) in the quantitative synthesis, the pooled HR of LVMD for predicting MACE was 2.81 (95% CI 2.03-3.88). Studies using combined phase parameters to define LVMD showed higher HRs than a study using phase entropy (p = 0.0180). LVMD from gated myocardial SPECT is a significant prognostic factor for coronary artery disease. Phase analysis of gated SPECT may be useful for accurate risk stratification and could be applied for clinical decision-making in such patients.

Role of Left Ventricular Strain Imaging in Patients Undergoing Cardiac Resynchronization Therapy

Lack of therapeutic response in nearly 30% of patients undergoing cardiac resynchronization therapy (CRT) remains a major therapeutic challenge. Given the role of echocardiography in detecting mechanical dyssynchrony, extensive research has been undertaken to identify the echocardiographic predictors of CRT response. After the initial setback, the interest in this field has renewed with the introduction of speckle-tracking echocardiography (STE) for quantifying myocardial deformation. Several newer and potentially useful indices of mechanical dyssynchrony have been developed. In addition, the non-invasive assessment of myocardial work has also become feasible and many of the myocardial work indices have shown considerable promise in the initial studies. The strain imaging may also help in identifying the optimum site for left ventricular lead placement. This review summarizes the current understanding regarding the role of left ventricular strain imaging in patients undergoing CRT.

Post-systolic shortening index by echocardiography evaluation of dyssynchrony in the non-dilated and hypertrophied left ventricle

Abstract Background Post-systolic shortening index (PSI) is defined as myocardial shortening that occurs after aortic valve closure, and is an emerging measure of regional LV contractile dysfunction. PSI measurement variability amongst software vendor and its relationship with mechanical dyssynchrony and mechanical dispersion index (MDI) remains unknown. We evaluated PSI by speckle-tracking echocardiography from several vendors in patients with increased left ventricular wall thickness, and associations with MDI. Methods This is a prospective cross-sectional study of 70 patients (36 hypertrophic cardiomyopathy [HCM], 18 cardiac amyloidosis and 16 healthy controls) undergoing clinically indicated echocardiography. PSI was measured using QLAB/aCMQ (Philips), QLAB/LV auto-trace (Philips), EchoPAC (GE), Velocity Vector Imaging (Siemens), and EchoInsight (EPSILON) software packages, and calculated as 100% × (post systolic strain − end-systole strain)/post systolic strain. Results There was a significant difference in mean PSI among controls 2.1±0.6%, HCM 6.1±2.6% and cardiac amyloidosis 6.8±2.7% (p<0.001). Variations between software vendors were significant in patients with pathologic increases in LV wall thickness (for HCM p=0.03, for amyloidosis p=0.008), but not in controls (p=0.11), as seen in Figure 1. Furthermore, there were moderate correlations between PSI and both MDI (r=0.77) and left ventricular global longitudinal strain (r=0.69), as seen in Figure 2. Conclusion PSI was greater in HCM and cardiac amyloidosis patients than controls, and a valuable tool for dyssynchrony evaluation, with moderate correlations to MDI and strain. However, there were significant variations in PSI measurements by software vendor especially in patients with pathological increase in LV wall thickness, suggesting that separate vendor-specific thresholds for abnormal PSI are required. Funding Acknowledgement Type of funding sources: None.

Post-systolic shortening index by echocardiography evaluation of dyssynchrony in the non-dilated and hypertrophied left ventricle.

Post-systolic shortening index (PSI) is defined as myocardial shortening that occurs after aortic valve closure, and is an emerging measure of regional LV contractile dysfunction. PSI measurement variability amongst software vendor and its relationship with mechanical dyssynchrony and mechanical dispersion index (MDI) remains unknown. We evaluated PSI by speckle-tracking echocardiography from several vendors in patients with increased left ventricular wall thickness, and associations with MDI. This is a prospective cross-sectional study of 70 patients (36 hypertrophic cardiomyopathy [HCM], 18 cardiac amyloidosis and 16 healthy controls) undergoing clinically indicated echocardiography. PSI was measured using QLAB/aCMQ (Philips), QLAB/LV auto-trace (Philips), EchoPAC (GE), Velocity Vector Imaging (Siemens), and EchoInsight (EPSILON) software packages, and calculated as 100%×(post systolic strain-end-systole strain)/post systolic strain. There was a significant difference in mean PSI among controls 2.1±0.6%, HCM 6.1±2.6% and cardiac amyloidosis 6.8±2.7% (p <0.001). Variations between software vendors were significant in patients with pathologic increases in LV wall thickness (for HCM p = 0.03, for amyloidosis p = 0.008), but not in controls (p = 0.11). Furthermore, there were moderate correlations between PSI and both MDI (r = 0.77) and left ventricular global longitudinal strain (r = 0.69). PSI was greater in HCM and cardiac amyloidosis patients than controls, and a valuable tool for dyssynchrony evaluation, with moderate correlations to MDI and strain. However, there were significant variations in PSI measurements by software vendor especially in patients with pathological increase in LV wall thickness, suggesting that separate vendor-specific thresholds for abnormal PSI are required.

Prognostic risk stratification based on left ventricular mechanical dyssynchrony in patients at low or intermediate risk of major cardiac events using the J-ACCESS risk model.

There have been no reports on prognostic prediction and risk stratification based on stress phase bandwidth (SPBW), or a left ventricular (LV) mechanical dyssynchrony index, in patients with known or suspected stable coronary artery disease (CAD) at low or intermediate risk of major cardiac events (MCEs) using the J-ACCESS risk model. We retrospectively investigated 4,996 consecutive patients with known or suspected CAD who underwent rest 201Tl and stress 99mTc-tetrofosmin electrocardiogram (ECG)-gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) and followed up for 3 years to confirm their prognosis. MCE risk over 3 years was estimated using an equation based on that used in the J-ACCESS study. The composite endpoint was the onset of MCEs consisting of cardiac death, non-fatal myocardial infarction (MI), and severe heart failure requiring hospitalization. SPBW was calculated by phase analysis with the Heart Risk View-F software and its normal upper limit was set to 38°. Based on the estimated 3-year incidence of MCEs obtained from the J-ACCESS risk model, 4,123 of the 4,996 consecutive patients were classified as low (n = 2,653) or intermediate risk (n = 1,470) and they were analyzed for follow-up. During the follow-up, 153 patients experienced MCEs: cardiac death (n = 38), non-fatal MI (n = 45), and severe heart failure (n = 70). The results of the multivariate analysis showed age, estimated glomerular filtration rate (eGFR), stress LV ejection fraction, and stress SPBW to be independent predictors of MCEs. The actual 3-year MCE rate in patients at intermediate risk was significantly higher than in those at low risk (6.7% vs. 2.1%, P < 0.0001). However, the actual 3-year MCE rate in patients with abnormal SPBW (> 38°) was 4.0% and 9.2% in low- and intermediate-risk patients, respectively, which corresponded to intermediate and high risk. Kaplan-Meier analysis also showed significant risk stratification by normal SPBW values for both low- and intermediate-risk patients. LV mechanical dyssynchrony assessed with ECG-gated SPECT MPI is useful for risk stratification of known or suspected stable CAD patients at low or intermediate risk of MCEs and may help identify higher risk patients who could not be identified as being at risk based on J-ACCESS risk assessment.

The value of cardiac sympathetic activity and mechanical dyssynchrony as cardiac resynchronization therapy response predictors: comparison between patients with ischemic and non-ischemic heart failure

BackgroundImpaired cardiac sympathetic activity and mechanical dyssynchrony (MD) are associated with poor prognosis in patients with heart failure (HF) after cardiac resynchronization therapy (CRT). The study aims to assess the significance of scintigraphic evaluation of cardiac sympathetic innervation and contractility in predicting response to CRT in patients with ischemic and non-ischemic chronic HF. Methods and resultsThe study includes 58 HF patients, who were referred for CRT. Prior to CRT all patients underwent 123I-metaiodobenzylguanidine (123I-MIBG) imaging and gated myocardial perfusion imaging (MPI) using a cadmium-zinc-telluride (CZT) SPECT/CT device. At a one-year follow-up post-CRT, the delayed heart-to-mediastinum 123I-MIBG uptake ratio was an independent predictor of CRT response in non-ischemic HF patients (OR 1.469; 95% CI 1.076-2.007, p = .003). In ischemic HF patients the MD index histogram bandwidth (HBW) obtained by CZT-gated MPI had a predictive value (OR 1.06, 95% CI 1.001-1.112, p = .005) to CRT response. ConclusionCRT response can be predicted by cardiac 123I-MIBG scintigraphy, specifically by the heart-to-mediastinum ratio in non-ischemic HF and by the MD index HBW in ischemic HF. These results suggest the value of a potentially useful algorithm to improve outcomes in HF patients who are candidates for CRT.

Prognostic Significance of Left Ventricular Dyssynchrony Assessed with Nuclear Cardiology for the Prediction of Major Cardiac Events after Revascularization.

Objective This retrospective study was aimed at determining whether or not stress phase bandwidth (SPBW), a left ventricular (LV) mechanical dyssynchrony index, predicts major cardiac events (MCEs) and stratifies the risk of those in patients with coronary artery disease (CAD) who undergo revascularization. Methods Patients were followed up to confirm the prognosis for at least one year. The SPBW was calculated by a phase analysis using the Heart Risk View-F software program. The composite endpoint was the onset of MCEs, consisting of cardiac death, non-fatal myocardial infarction, unstable angina pectoris, and severe heart failure requiring hospitalization. Patients The study subjects were 332 patients with CAD who underwent coronary angiography and revascularization after confirming ≥5% ischemia detected by rest 201Tl and stress 99mTc-tetrofosmin electrocardiogram-gated single-photon emission computed tomography myocardial perfusion imaging. Results During the follow-up, 35 patients experienced MCEs of cardiac death (n=5), non-fatal myocardial infarction (n=3), unstable angina pectoris (n=11), and severe heart failure requiring hospitalization (n=16). A receiver operating characteristics analysis indicated that the optimal cut-off value of the SPBW was 52° for predicting MCEs, and the MCE rate was significantly higher in the patients with an SPBW >52° than in those with an SPBW ≤52°. Results of the multivariate analysis showed the SPBW and estimated glomerular filtration rate to be independent predictors for MCEs. In addition, the cut-off value of the SPBW significantly stratified the risk of MCEs according to the results of the Kaplan-Meier analysis. Conclusion Evaluating the SPBW before revascularization may help predict future MCEs in patients with CAD who intended to undergo treatment.

2D/3D Echocardiographic features of patients with reverse remodeling after cardiac resynchronization therapy.

To describe clinical and echocardiographic characteristics associated with reverse left ventricular (LV) remodeling after 6months of cardiac resynchronization therapy (CRT) in patients with nonischemic dilated cardiomyopathy. Twenty-four consecutive patients underwent 2D and 3D echocardiography before and after 6months of CRT implant. Several echocardiographic parameters including global longitudinal strain (GLS) and 3D mechanical dyssynchrony (MD) index were calculated. CRT response was defined as a decrease in LV end-systolic volume (LVESV) of at least 10% at follow-up. Patients were divided in two groups according to CRT response. Cardiac resynchronization therapy responder (CRTR+) rate was 50%. Nonresponder (CRTR-) patients showed a less significant improvement in NYHA class at follow-up. At baseline, CRTR- presented with higher LV end-diastolic volume (LVEDV) (P=0.031), LVESV (P=0.024), lower left ventricular ejection fraction (LVEF) (P=0.002) and less negative GLS (P=0.03), and with higher diastolic dysfunction, more impaired right ventricle (RV), and higher pulmonary artery systolic pressure (PASP) (P=0.002). No significant differences in echocardiographic parameters of MD were found. Univariate determinants of CRTR+ were LVEF (OR=1.59, CI 95%=1.13-2.22, P=0.007) and TAPSE (OR 1.21, CI 95%=1.024-1.429, P=0.025). A ROC curve analysis showed a cutoff value of LVEF of 22.15% significantly related to CRTR+ (SE 80%, SP 50%). Our findings suggest that end-stage HF patients, presenting before CRT with LVEF <22.15%, may not benefit from the procedure after 6months. Mechanical dyssyncronicity did not provide additional information to improve candidate selection.

Ventricular interactions and electromechanical dyssynchrony after Ross and Ross-Konno operations

ObjectivesRoss and Ross-Konno operations are associated with the inherent risk of residual ventricular septal dysfunction and injury to the conduction system. However, comprehensive biventricular functional outcomes on magnetic resonance imaging after Ross and Ross-Konno procedures are unknown. The purpose of this study was to evaluate and compare the degree of electrical and mechanical dyssynchrony using cardiac magnetic resonance imaging in patients late after Ross and Ross-Konno operations. MethodsPatients following Ross operation (n = 16), Ross-Konno operation (n = 13), and healthy controls (n = 12) underwent cardiac magnetic resonance imaging strain deformation analysis to quantify left ventricular (LV) intraventricular dyssynchrony and right ventricular (RV)–LV interventricular dyssynchrony. Mechanical dyssynchrony indices were correlated with the degree of electrical dyssynchrony as assessed by QRS duration, as well as with magnetic resonance imaging-derived biventricular and autograft regurgitation parameters. ResultsPatients in the Ross and Ross-Konno groups had reduced LV global longitudinal strain when compared with controls (both P values < .01). Both Ross (P < .05) and Ross-Konno (P < .01) groups demonstrated increased RV–LV interventricular dyssynchrony compared with controls. Patients in the Ross-Konno group also had increased septal LV intraventricular dyssynchrony when compared with control and Ross groups (both P values < .01). The global LV intramechanical dyssynchrony strongly correlated with QRS duration (R = 0.716; P < .001). There was no association between mechanical dyssynchrony and aortic regurgitation fraction. ConclusionsLong-term follow-up of patients who underwent Ross and Ross-Konno operations demonstrates reduced LV global longitudinal strain suggestive of chronically increased afterload independent of autograft function. Additionally, Ross-Konno operation is associated with impaired LV intraventricular mechanics and electrical dyssynchrony.

Mechanical dyssynchrony of the left atrium during sinus rhythm is associated with history of stroke in patients with atrial fibrillation.

We sought to evaluate the relationship between left atrial (LA) mechanical dyssynchrony and history of stroke or transient ischaemic attack (TIA) in patients with atrial fibrillation (AF). We hypothesized that mechanical dyssynchrony of the LA is associated with history of stroke/TIA independent of LA function and Cardiac failure, Hypertension, Age, Diabetes, Stroke/transient ischaemic attack (TIA), VAscular disease, and Sex category (CHA2DS2-VASc) score in patients with AF. We conducted a cross-sectional study of 246 patients with a history of AF (59 ± 10 years, 29% female, 26% non-paroxysmal AF) referred for catheter ablation to treat drug-refractory AF who underwent preablation cardiac magnetic resonance (CMR) in sinus rhythm. Using tissue-tracking CMR, we measured the LA longitudinal strain and strain rate in each of 12 equal-length segments in two- and four-chamber views. We defined indices of LA mechanical dyssynchrony, including the standard deviation of the time to the peak longitudinal strain (SD-TPS). Patients with a prior history of stroke or TIA (n = 23) had significantly higher SD-TPS than those without (n = 223) (39.9 vs. 23.4 ms, P < 0.001). Multivariable analysis showed that SD-TPS was associated with stroke/TIA after adjusting for the CHA2DS2-VASc score, LA minimum index volume, and the peak LA longitudinal strain (P < 0.001). The receiver-operating characteristics curve showed that SD-TPS identified patients with stroke/TIA more accurately than CHA2DS2-VASc score alone (c-statistics: 0.82 vs. 0.75, P < 0.001). Higher mechanical dyssynchrony of the LA during sinus rhythm is associated with a history of stroke/TIA in patients with AF.

Role of low‑dose dobutamine echocardiography in predicting response to biventricular pacing. Results from themulticenter Viability in Cardiac Resynchronisation Therapy (ViaCRT) study.

INTRODUCTION The response to Cardiac Resynchronisation Therapy (CRT) varies significantly, resulting in lack of improvement among the substantial patients proportion. OBJECTIVES To identify mechanical dyssynchrony indices with combination of myocardial viability characteristics for predicting long-term response to CRT. PATIENTS AND METHODS ViaCRT was a multicentre study coordinated by the Working Group on Echocardiography of Polish Cardiac Society. 127 patients with heart failure were assessed prospectively. Cardiac dyssynchrony indices and low-dose dobutamine response were determined by echocardiography prior to CRT. Improvement in Wall Motion Score Index (WMSI) or LVEF exceeding 20% at peak stress identified preserved contractile reserve. RESULTS After 12 months there was significantly different survival between subsets with and without viability characterised by WMSI decrease, corresponding to 1 (4.4%) and 20 (19.4%) fatal events respectively (p=0.048). The predictive value of LVEF gain at Dobutamine Stress Echocardiography (DSE) study was only significant at 6 months, with all-cause death occurring in 1 (1.6%) and 7 (12.1%) of patients with viable and non-viable myocardium respectively (p=0.029). Multivariate regression analysis identified the presence of septal flash and interventricular dyssynchrony as independent indices with the ability to predict echocardiographic response alone at 12 months. CONCLUSIONS The study demonstrated a significant relationship between left ventricular contractile reserve at DSE and long-term all-cause mortality following CRT device implantation. Conversely, the presence of septal flash and interventricular dyssynchrony but not myocardial viability were predictive of the response to resynchronisation. The results indicate that interference of multiple different mechanisms may be responsible for the general effect following CRT.

Insights into the Evolution of Myocardial Dysfunction in the Functionally Single Right Ventricle between Staged Palliations Using Speckle-Tracking Echocardiography

The long-term prognosis of hypoplastic left heart syndrome is limited by progressive right ventricular dysfunction. The aim of this study was to determine the trends in single right ventricular systolic function between staged palliative surgeries using speckle-tracking and conventional echocardiography. There were 76 patients with functionally single right ventricles at the (1) pre-Norwood (n = 26), (2) pre-bidirectional cavopulmonary anastomosis (BCPA; n = 19), (3) pre-Fontan (n = 16), and (4) post-Fontan (n = 15) stages, compared with 30 controls of similar ages. Speckle-tracking-derived longitudinal and circumferential strain and strain rate, postsystolic strain index, and mechanical dyssynchrony index were compared with conventional measures of ventricular function. Differences between stages were analyzed using analysis of variance (P < .05). Strain rate was highest at the pre-Norwood stage and decreased at the other stages (longitudinal P < .0001, circumferential P = .0002), as opposed to controls, in whom strain rate was maintained. Longitudinal strain was significantly decreased at the pre-BCPA stage compared with the pre-Norwood stage (P = .004), but circumferential strain was maintained, resulting in a corresponding decrease in the ratio of longitudinal to circumferential strain, which failed to resemble that of controls. Longitudinal (P = .003) and circumferential (P = .002) postsystolic strain indices were greatest at the pre-BCPA stage. A decline in contractility occurred at the pre-BCPA stage. Although there was evidence of adaptation of the single right ventricle, this failed to resemble the normal left ventricle and may be insufficient to handle the chronic volume load or insult from previous surgery. These findings suggest an intrinsic inability of the single right ventricular myocardium to fully adapt to chronic systemic pressures.

Assessment of strain and mechanical dyssynchrony indices in single ventricle populations by cardiac magnetic resonance feature-tracking techniques

Background Single ventricle (SV) physiology consists of a single pumping chamber that provides both systemic and pulmonary blood flow. The typical quantitative measurements of ventricular function (i.e. ejection fraction) cannot be accurately applied to single ventricles due to abnormal ventricular morphology. Cardiac Magnetic Resonance (CMR) has become a leading diagnostic tool in the assessment of ventricular mechanics in patients with abnormal ventricular morphology. CMR feature-tracking (FT) techniques allow for the analysis of circumferential strain (ecc), longitudinal strain (ell), and mechanical dyssynchrony indices (MDI). We hypothesize that evidence of declining ecc, ell, and MDI by CMR will be a early biomarker of ventricular dysfunction in SV patients. Methods

Paradoxical septal motion from prior coronary artery bypass graft surgery does not impact left ventricular mechanical dyssynchrony by gated myocardial perfusion imaging

BackgroundPhase analysis of gated myocardial perfusion imaging (MPI) provides automated and reproducible assessment of left ventricular (LV) mechanical dyssynchrony (LVMD) (phase standard deviation [SD]). Many patients undergoing gated MPI have history of prior coronary artery bypass graft surgery (CABG). The latter is often associated with paradoxical septal wall motion (PSM). The effect of prior CABG and PSM on LVMD has not been evaluated. Methods and ResultsFrom the single-photon emission computed tomography (SPECT) and positron emission tomography (PET) MPI clinical database maintained at the Cleveland Clinic, we identified 200 consecutive patients with SPECT (100 control with normal LV ejection fraction [EF], MPI, and QRS < 120 ms; and 100 with LVEF < 35%), and 631 patients with LVEF < 35% with gated PET. Patients with QRS ≥ 120 ms, bundle branch block, ventricular pacing or isolated non-CABG surgery were excluded. There were 162 patients with gated SPECT (46 with prior CABG), and 568 with gated PET (220 with prior CABG) that were left for analysis. Phase SD was derived using Emory Cardiac Toolbox (ECTb) (for gated SPECT) and Corridor 4DM (4DM) (for gated SPECT and PET images). Multivariate linear regression analysis was performed to assess whether prior CABG was an independent predictor of worse LV mechanical dyssynchrony. After adjusting for patients’ demographics, co-morbidities, medications, and MPI data, history of prior CABG was not and independent predictor of LV mechanical dyssynchrony (P = .67 with 4DM, P = .97 with ECTb) in patients undergoing gated SPECT or among patients undergoing gated PET imaging (P = .18). ConclusionsAlthough paradoxical septal wall motion is commonly seen after cardiac surgery, prior CABG does not affect or impact LV mechanical dyssynchrony indices measured from gated SPECT or PET images. Whether dyssynchrony measurements with echocardiography that has higher temporal resolution might uncover intraventricular delays, remains to be determined.

Insights into dyssynchrony in Hypoplastic Left Heart Syndrome

Cardiac resynchronization therapy has been proposed for treatment of hypoplastic left heart syndrome (HLHS) patients with right ventricular (RV) failure. The role of dyssynchrony, however, is poorly understood in this population. The purpose of this study was to better understand the relationship between electrical and mechanical dyssynchrony in HLHS using 3-dimensional electrical mapping, tissue Doppler indices of wall motion, and vector velocity imaging. Eleven HLHS subjects with normal RV function and ten normal subjects (age 3-18 years) were studied. Electrical and mechanical activation times and dyssynchrony indices (electrical dyssynchrony index, mechanical dyssynchrony index) were calculated using 3-dimensional electrical mapping, tissue Doppler indices, and vector velocity imaging. No differences in measures of electrical dyssynchrony were seen when comparing HLHS patients and normal patients (electrical activation time 63.3 ± 22.8 ms vs 56.2 ± 11.2 ms, P = .38; electrical dyssynchrony index 13.7 ± 6.3 ms vs 11.6 ± 3.0 ms, P = .34). However, measures of mechanical dyssynchrony were markedly abnormal in HLHS patients despite normal RV function (mechanical activation time 16 ± 11.3 ms vs 0.9±1.9 ms, P = .01; mechanical dyssynchrony index 7.5 ± 5.5 vs 0.4 ± 0.8, P<.01). Patients with HLHS and preserved RV systolic function have normal electrical activation when compared to patients with normal right and left ventricles. In contrast, these patients demonstrate mechanical dyssynchrony compared to patients with normal right and left ventricles. This finding raises important questions about the indications for cardiac resynchronization therapy in this patient population.

Mechanistic Evaluation of Echocardiographic Dyssynchrony Indices

Background— The power of echocardiographic dyssynchrony indices to predict response to cardiac resynchronization therapy (CRT) appears to vary between indices and between studies. We investigated whether the variability of predictive power between the dyssynchrony indices can be explained by differences in their operational definitions. Methods and Results— In 132 CRT-candidates (left ventricular [LV] ejection fraction, 19 ± 6%; QRS width, 170 ± 22 ms), 4 mechanical dyssynchrony indices (septal systolic rebound stretch [SRSsept], interventricular mechanical dyssynchrony [IVMD], septal-to-lateral peak shortening delay [Strain-SL], and septal-to-posterior wall motion delay [SPWMD]) were quantified at baseline. CRT response was quantified as 6-month percent change of LV end-systolic volume. Multiscale computer simulations of cardiac mechanics and hemodynamics were used to assess the relationships between dyssynchrony indices and CRT response within wide ranges of dyssynchrony of LV activation and reduced contractility. In patients, SRSsept showed best correlation with CRT response followed by IVMD, Strain-SL, and SPWMD ( R =−0.56, −0.50, −0.48, and −0.39, respectively; all P &lt;0.01). In patients and simulations, SRSsept and IVMD showed a continuous linear relationship with CRT response, whereas Strain-SL and SPWMD showed discontinuous relationships characterized by data clusters. Model simulations revealed that this data clustering originated from the complex multipeak pattern of septal strain and motion. In patients and simulations with (simulated) LV scar, SRSsept and IVMD retained their linear relationship with CRT response, whereas Strain-SL and SPWMD did not. Conclusions— The power to predict CRT response differs between indices of mechanical dyssynchrony. SRSsept and IVMD better represent LV dyssynchrony amenable to CRT and better predict CRT response than the indices assessing time-to-peak deformation or motion.

Electrical and mechanical dyssynchrony in pediatric pulmonary hypertension

Electrical and mechanical dyssynchrony are often seen in patients with left ventricular failure. In pediatric pulmonary hypertension (PH), right ventricular failure predominates; however, the prevalence of electrical and/or mechanical dyssynchrony in these patients is unknown. We examined the prevalence of electrical and mechanical dyssynchrony in pediatric PH patients. Medical records (including, functional status, electrocardiograms and echocardiograms) of pediatric PH patients were reviewed. QRS duration z-scores were calculated to determine electrical dyssynchrony. Echo vector velocity imaging was used to calculate the mechanical dyssynchrony index (DI). Seventy-seven PH patients (idiopathic pulmonary arterial hypertension [IPAH]: n = 26; congenital heart disease: n = 41; other: n = 10) were studied. Electrical dyssynchrony was seen in 84% (p < 0.01 vs historic controls), with a mean z-score of 4.3 (95% CI 3.5 to 5.1). There was no difference between those with IPAH, z = 3.6 (95% CI 2.5 to 4.6), and those without, z = 4.7 (95% CI 3.6 to 5.8). Mechanical dyssynchrony was seen in 76% of patients (mean DI = 66 ± 47 vs 18 ± 8 milliseconds in historic controls, p < 0.01) in both IPAH and non-IPAH patients. Post-operative congenital heart disease patients had the largest dyssynchrony index. No correlation was found among electrical or mechanical dyssynchrony, hemodynamics or disease severity. Significant electrical and mechanical dyssynchrony is present in pediatric PH patients, regardless of etiology. The overall effect of electrical and mechanical dyssynchrony on outcomes in this patient population is still unknown. Select patients may benefit from resynchronization therapy.

Impaired Left Ventricular Myocardial Mechanics and Their Relation to Pulmonary Regurgitation, Right Ventricular Enlargement and Exercise Capacity in Asymptomatic Children after Repair of Tetralogy of Fallot

Left ventricular (LV) dysfunction is common in adults late after repair of tetralogy of Fallot (TOF). The early detection of myocardial dysfunction may be important, but LV myocardial strain and dyssynchrony are not well studied in children with TOF. The objective of this study was to investigate LV strain and dyssynchrony in asymptomatic children and adolescents after contemporary repair of TOF. The hypothesis was that impaired LV myocardial mechanics are related to pulmonary regurgitation, right ventricular (RV) enlargement, and exercise capacity. Children and adolescents were prospectively studied after TOF repair. LV regional strain and dyssynchrony were assessed using two-dimensional speckle-tracking echocardiography. Ventricular volumes, ejection fraction, and pulmonary regurgitation were assessed using magnetic resonance imaging. Exercise capacity was determined using metabolic exercise testing. One hundred twenty-four subjects (53 patients with TOF and 71 controls) were studied. Regional circumferential (e.g., basal lateral wall, -15.0 ± 7.0% vs -19.0 ± 7.0%, P= .02) and radial (e.g., basal posterior wall, 32.0 ± 18.0% vs 48.0 ± 21.0%, P < .001) LV strain and longitudinal septal strain (-18.5 ± 3.5% vs -20.2 ± 2.8%, P= .01) were significantly reduced in patients with TOF compared with controls. LV mechanical dyssynchrony indices were not significantly different between groups (e.g., standard deviation of time to peak circumferential strain, 52.5 ± 40.4 vs 50.5 ± 27.1 msec, P= .81). Higher pulmonary regurgitation volume and larger RV end-diastolic volume were associated with decreased LV radial strain (P= .09). There was no association between LV longitudinal, radial, or circumferential dyssynchrony and indexed pulmonary regurgitation flow volume, RV end-diastolic volume, or RV ejection fraction. LV circumferential and radial strain are significantly reduced in children and adolescents after TOF repair and are associated with pulmonary regurgitation and RV dilatation. Resting LV mechanical dyssynchrony does not appear to contribute to early impaired LV strain in this population.

Effect of tracer dose on left ventricular mechanical dyssynchrony indices by phase analysis of gated single photon emission computed tomography myocardial perfusion imaging

BackgroundThere are limited data on the effect of tracer dose on the reproducibility and accuracy of left ventricular (LV) mechanical dyssynchrony indices by phase analysis of gated single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). Methods and ResultsWe measured LV dyssynchrony in 54 patients with normal LV ejection and perfusion (group 1) and 54 age and gender matched patients with LV ejection <35% (group 2) using phase analysis of gated SPECT MPI from stress (high dose) and rest (low dose) studies with 2 software programs: Corridor4DM (4DM) and Emory Cardiac Toolbox (ECTb). Although the correlation between rest- and stress-derived standard deviation was good (R = 0.76, P < .0001, with both software programs), there was considerable variability between the measurements (P < .0001 by paired t test). In addition, the rest standard deviation was significantly higher than stress in group 1 (10.2° ± 4.6° vs 6.1° ± 2.5°, and 12.2° ± 6.4° vs 7.9° ± 4.6°, with 4DM and ECTb, respectively, P < .0001 for both) and group 2 patients (44.0° ± 18.0° vs 35.9° ± 21.0° and 47.3° ± 19.2° vs 38.8° ± 19.8°, with 4DM and ECTb, P = .03 and.02, respectively). Similarly, the rest standard deviations were higher than the stress values irrespective of the type of stress test (i.e., exercise vs pharmacological), and the body mass index. Finally, using rest-derived dyssynchrony indices was associated with 9%-13% and 22%-26% false positive rate of significant mechanical dyssynchrony using different cut-off values for groups 1 and 2, respectively. ConclusionLV mechanical dyssynchrony indices by phase analysis have more variation and are significantly higher if derived from rest gated SPECT images obtained with low-dose tracer.