Global and regional left ventricular strain indices in post-myocardial infarction patients with ventricular arrhythmias and moderately abnormal ejection fraction

Strain Imaging and Ventricular Arrhythmia

Ventricular arrhythmia is one of the main causes of sudden cardiac death. Hence, identifying patients at risk of ventricular arrhythmias and sudden cardiac death is important but can be challenging. The indication for an implantable cardioverter defibrillator as a primary preventive strategy relies on the left ventricular ejection fraction as a measure of systolic function. However, ejection fraction is flawed by technical constraints and is an indirect measure of systolic function. There has, therefore, been an incentive to identify other markers to optimize the risk prediction of malignant arrhythmias to select proper candidates who could benefit from an implantable cardioverter defibrillator. Speckle-tracking echocardiography allows for a detailed assessment of cardiac mechanics, and strain imaging has repeatedly been shown to be a sensitive technique to identify systolic dysfunction unrecognized by ejection fraction. Several strain measures, including global longitudinal strain, regional strain, and mechanical dispersion, have consequently been proposed as potential markers of ventricular arrhythmias. In this review, we will provide an overview of the potential use of different strain measures in the context of ventricular arrhythmias.

Multi-modality imaging to guide the implantation of cardiac electronic devices in heart failure: is the sum greater than the individual components?

Heart failure is a clinical syndrome with an increasing prevalence and incidence worldwide that impacts patients' quality of life, morbidity, and mortality. Implantable cardioverter-defibrillator and cardiac resynchronization therapy are pillars of managing patients with HF and reduced left ventricular ejection fraction. Despite the advances in cardiac imaging, the assessment of patients needing cardiac implantable electronic devices relies essentially on the measure of left ventricular ejection fraction. However, multi-modality imaging can provide important information concerning the aetiology of heart failure, the extent and localization of myocardial scar, and the pathophysiological mechanisms of left ventricular conduction delay. This paper aims to highlight the main novelties and progress in the field of multi-modality imaging to identify patients who will benefit from cardiac resynchronization therapy and/or implantable cardioverter-defibrillator. We also want to underscore the boundaries that prevent the application of imaging-derived parameters to patients who will benefit from cardiac implantable electronic devices and orient the choice of the device. Finally, we aim at providing some reflections for future research in this field.

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

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). Furthermore, there were moderate correlations between PSI and both MDI (r = 0.77) and left ventricular global longitudinal strain (r = 0.69).

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.

Structural and Physiological Imaging to Predict the Risk of Lethal Ventricular Arrhythmias and Sudden Death

Identifying patients at risk of sudden cardiac death remains a major challenge in cardiovascular medicine. Advances in cardiovascular imaging have identified several anatomic and functional variables that can be quantified as continuous variables to predict the risk of developing lethal ventricular tachyarrhythmias in patients with depressed left ventricular (LV) systolic function. Some, such as LV mass, volume, and the dyssynchrony of contraction, can be derived from currently available echocardiographic and nuclear imaging modalities. Others require advanced cardiac imaging modalities with quantification of myocardial scar with gadolinium-enhanced cardiac magnetic resonance and myocardial sympathetic denervation using norepinephrine analogs and positron emission tomography or single-photon emission computed tomography offering the most promise. There is an immediate need to develop a sequential cost-effective approach that capitalizes on readily available clinical information complemented with advanced imaging modalities in selected patients to improve risk stratification for arrhythmic death beyond LV ejection fraction.

Assessment of strain and dyssynchrony in normal fetuses using speckle tracking echocardiography - comparison of three different ultrasound probes

OBJECTIVE

To evaluate segmental left (LV-S) and right (RV-S) ventricular strain as well as longitudinal mechanical myocardial dyssynchrony as a time difference between peaks in strain of both ventricles in fetuses (two-chamber-dyssynchrony, 2C-DYS) using speckle tracking echocardiography (STE). The aim of our study was to evaluate the influence of data acquisition on the results of STE measurement using different ultrasound probes.

METHODS

We prospectively recorded cardiac cycles of four-chamber views of 56 normal fetuses with three different ultrasound probes and analyzed them offline with speckle tracking imaging software. Furthermore, we looked at a possible influence of heartbeat variability (beat-to-beat variability).

RESULTS

The evaluation of the parameters was feasible with all three probes in 53 cases. There was no influence of heartbeat variability and no noticeable differences in 2C-DYS, LV-S and RV-S in all cases and for all three probes determined.

CONCLUSION

Assessment of strain and dyssynchrony using STE with three different probes is comparable. Further research is needed to validate dyssynchrony as a predictor for fetal outcome.

Prediction for Improvement and Remodeling in First-Onset Myocardial Infarction by Speckle Tracking Echocardiography: Is Global or Regional Selection Better?

Cardiac function improvement and chamber remodeling after the onset of acute myocardial infarction (AMI) is crucial as it is closely related to the outcomes of patients. We sought to investigate the predictive value of left ventricular (LV) global and region of interest (ROI) assessment for prognosis of AMI patients by speckle tracking echocardiography (STE). We prospectively enrolled 81 first-onset AMI patients for baseline and 6-mo follow-up analysis. The echocardiography-derived parameters were compared in receiver operator characteristics (ROC) analysis for prediction of LV remodeling (LVR) (a minimum 20% increase of LV end-diastolic volume) and cardiac function improvement (a minimum 5% increase of LV ejection fraction). The ROI strain was selected by wall motion score index (WMSI) scores ≥2. The time of whole analysis process was recorded. Cut-off values of -9.92% for global circumferential strain (CS) and -5.53% for ROI CS predicted LVR. Cut-off values of -10.40% for global longitudinal strain (LS) and -5.33% for ROI LS predicted cardiac function improvement. Areas under curves of global and ROI parameters were comparable in ROC analysis (p > 0.05, all). The time of global analysis was less than the time of ROI analysis (p < 0.05) and the reproducibility of global analysis was slightly better than the ROI analysis. Our results demonstrated that STE was valuable for the prediction of LVR and cardiac function improvement after AMI. Compared with ROI parameters, global parameters were more integral and efficient as predictive factors with high predictive power, less analysis time and better reproducibility.

Prominent differences in left ventricular performance and myocardial properties between right ventricular and left ventricular-based pacing modes in rats

Biventricular pacing is an important modality to improve left ventricular (LV) synchronization and long-term function. However, the biological effects of this treatment are far from being elucidated and existing animal models are limited and demanding. Recently, we introduced an implanted device for double-site epicardial pacing in rats and echocardiographically demonstrated favorable effects of LV and biventricular (LV-based) pacing modes typically observed in humans. Here, this new animal model was further characterized. Electrodes were implanted either on the right atria (RA) and right ventricle (RV) or on the RV and LV. Following recovery, rats were either used for invasive hemodynamic measurements (pressure-volume analysis) or exposed to sustained RV vs. biventricular tachypacing for 3 days. RV pacing compromised, while LV-based pacing modes markedly enhanced cardiac performance. Changes in LV performance were associated with prominent compensatory changes in arterial resistance. Sustained RV tachypacing increased the electrocardiogram QTc interval by 7.9 ± 3.1 ms (n = 6, p < 0.05), dispersed refractoriness between the right and left pacing sites and induced important molecular changes mainly in the early-activated septal tissue. These effects were not observed during biventricular tachypacing (n = 6). Our results demonstrate that the rat is an attractive new model to study the biological consequences of LV dyssynchrony and resynchronization.

Regional Longitudinal Deformation Improves Prediction of Ventricular Tachyarrhythmias in Patients With Heart Failure With Reduced Ejection Fraction

Background—

Left ventricular dysfunction is a known predictor of ventricular arrhythmias. We hypothesized that measures of regional longitudinal deformation by speckle-tracking echocardiography predict ventricular tachyarrhythmias and provide incremental prognostic information over clinical and conventional echocardiographic characteristics.

Methods and Results—

We studied 1064 patients enrolled in the MADIT-CRT trial (Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy) with speckle-tracking data available. Peak longitudinal strain was obtained for the septal, lateral, anterior, and inferior myocardial walls at baseline. The end point was the first event of ventricular tachycardia (VT) or fibrillation (VF). During the median follow-up of 2.9 years, 254 (24%) patients developed VT/VF. Patients with VT/VF had significantly lower left ventricular ejection fraction (28.3% versus 29.5%; P <0.001) and longitudinal strain in all myocardial walls compared with patients without VT/VF (anterior-strain, −7.7% versus −8.8%; P <0.001; lateral-strain, −7.3% versus −7.9%; P =0.022; inferior-strain, −8.3% versus −9.9%; P <0.001; septal-strain, −9.1% versus −10.0%; P <0.001). After multivariate adjustment, only anterior and inferior longitudinal strain remained independent predictors of VT/VF (anterior: hazard ratio, 1.08 [1.03–1.13]; P =0.001; inferior: hazard ratio, 1.08 [1.04–1.12]; P <0.001; per 1% absolute decrease for both). When including B-type natriuretic peptide in the model, only a decreasing myocardial function in the inferior myocardial wall predicted VT/VF (hazard ratio, 1.05 [1.00–1.11]; P =0.039). Only strain obtained from the inferior myocardial wall provided incremental prognostic information for VT/VF over clinical and echocardiographic parameters (C statistic 0.71 versus 0.69; P =0.005).

Conclusions—

Assessment of regional longitudinal myocardial deformation in the inferior region provided incremental prognostic information over clinical and echocardiographic risk factors in predicting ventricular tachyarrhythmias.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00180271.